HOW TO STAY YOUNG

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1. Throw out nonessential numbers. This includes age, weight and height.
Let the doctors worry about them. That is why you pay them.

2. Keep only cheerful friends.
The grouches pull you down. (keep this In mind if you are one of those
grouches;)

3. Keep learning:
Learn more about the computer, crafts, gardening,
whatever. Never let the brain get idle.
"An idle mind is the devil's workshop."
And the devil's name is Alzheimer's!

4. Enjoy the simple things.

5. Laugh often, long and loud. Laugh until you gasp for breath.
And if you have a friend who makes you laugh, spend lots and Lots of time
with HIM/HER.

6. The tears happen:
Endure, grieve, and move on. The only person who is with us our entire
life, is ourself. LIVE while you are alive.

7. Surround yourself with what you love:
Whether it's family, pets, keepsakes, music, plants, hobbies, whatever.
Your home is your refuge.

8. Cherish your health:
If it is good, preserve it.
I f it is unstable, improve it.
If it is beyond what you can improve, get help.

9. Don't take guilt trips.
Take a trip to the mall, even to the next county, to a foreign country, but
NOT to where the guilt is.

10. Tell the people you love that you love them, at every opportunity.

And if you don't send this to at least four people -- who cares?
But do share this with someone.

SPIDER

Spiders were among the earliest animals to live on land. Despite this their fossil record is relatively poor. They probably evolved about 400 million years ago from thick-waisted arachnid ancestors that were not long emerged from life in water. The first definite spiders, thin-waisted arachnids with abdominal segmentation and silk producing spinnerets, are known from fossils like Attercopus fimbriungus. This spider lived 380 million years ago during the Devonian Period, more than 150 million years before the dinosaurs.
Most of the early segmented fossil spiders belonged to the Mesothelae, a group of primitive spiders with the spinnerets placed underneath the middle of the abdomen (rather than at the end as in 'modern' spiders). They were probably ground dwelling predators, living in the giant clubmoss and fern forests of the mid-late Palaeozoic, where they were presumably predators of other primitive arthropods (like cockroaches, giant silverfish, slaters and millipedes). Silk may have been used simply as a protective covering for the eggs, a lining for a retreat hole, and later perhaps for simple ground sheet web and trapdoor construction.
As plant and insect life diversified so also did the spider's use of silk. Spiders with spinnerets at the end of the abdomen (Opisthothelae) appeared more than 250 million years ago, presumably promoting the development of more elaborate sheet and maze webs for prey capture both on ground and foliage, as well as the development of the safety dragline.
By the Jurassic Period (191 - 136 million years ago), when dinosaurs roamed the earth, the sophisticated aerial webs of the orb weaving spiders had developed to trap the rapidly diversifying hordes of flying insects. Similarly, the diversification of hunting spiders in litter, bark and foliage niches would have progressed in response to new prey-capture and habitat opportunities.
During the Tertiary Period the rich record of amber spider fossils - complete spiders trapped in clear, sticky, tree resins - show us that a spider fauna basically similar to that of the present day existed more than 30 million years ago.

What are the differences between spiders and insects?
Spiders have two main body parts, eight walking legs, simple eyes and piercing jaws (fangs), abdominal silk spinning organs, anterior abdominal genital opening.
Insects have three main body parts, six walking legs, compound eyes, antennae, chewing jaws (mandibles - often secondarily modified), posterior abdominal genital opening.
Spiders can't fly.
Many insects can fly.

FACTS FILE OF SPIDER

Can funnel-web spiders jump?
No. They rear up when disturbed, and bite with a fast downward action. They may rush forward aggressively, but they are not capable of propelling themselves off the ground.
What do funnel-web spider burrows look like?
Funnel-web burrows are distinguished from other holes in the ground by the presence of a series of irregular silk "trip-lines" radiating out from the entrance. Holes are normally found in moist, shaded areas like rockeries, dense shrubs, logs and leaf litter. A small, neat hole lined with a collar of silk which does not extend more than a centimetre from the rim could belong to a trapdoor spider (the common Brown Trapdoor Spider does not build a "door" for its burrow). Other possible hole owners include mouse spiders, wolf spiders or insects (most commonly cicadas or ants).
Photograph of a funnel-web burrow - funnel-web spider fact sheethttp://www.amonline.net.au/factsheets/funnelweb.htm
Why do funnel-web spiders wander (and end up in my house or swimming pool)?
Male funnel-webs leave their burrows to search for females in summer and autumn, and are normally active at night. The female funnel-web does not normally leave her burrow, but may be unearthed by excavations, rubbish removal or gardening, or be driven out by heavy rain. Wandering spiders are frequently encountered after a period of wet weather. Funnel-web spiders often fall into swimming pools. Spiders can trap a small bubble of air in hairs around the abdomen, which aids both breathing and floating, so it should not be assumed that a spider on a pool bottom has drowned. Funnel-webs have been known to survive 24-30 hours under water. Wandering spiders can enter houses at ground level, often under a door. Once inside a house, Funnel-web spiders will seek shelter to avoid drying out. Other large spider species such as the Brown Trapdoor and mouse spiders exhibit similar behaviour.
Information on control - Spiders in the House and Garden leaflethttp://www.amonline.net.au/factsheets/spiders.htm
Are huntsman spiders dangerous? They look so large and hairy...
Despite their often large and hairy appearance, huntsman spiders are not considered to be dangerous spiders. As with most spiders, they do possess venom, and a bite may cause some ill effects. However, they are quite reluctant to bite, and will usually try to run away rather than be aggressive. In houses they perform a useful role as natural pest controllers.
Some people may think of huntsman spiders as "tarantulas". However, they are not related to the large hairy ground dwelling spiders that are normally called tarantulas. Both huntsman spiders and tarantulas are often portrayed as being dangerous and scary. This usually is the case in films or stories that deliberately present spiders in a frightening and unrealistic way. If you feel frightened of huntsman spiders because of this, perhaps you might like to learn more about their true habits and biology. In this way you might be able to reduce your fears.
Huntsman spiders fact sheethttp://www.amonline.net.au/factsheets/huntsman_spiders.htm
How do you identify a wolf spider?
One of the diagnostic features of wolf spiders is their eye pattern which comprises three rows at the front of the carapace: four (smaller) eyes in the first row, two above the first and two above the second row. The diagram below (basically) shows this layout, face-on to the spider.
top
o oo o. . . .
bottom
Wolf spiders also have a variegated pattern on their bodies, often including radiating lines on the carapace and scroll-like patterns on the top of the abdomen. The underside of the spider is grey or black, sometimes with white markings. They can have orange spots on the sides of their jaws.
As Wolf spiders actively hunt for food they are likely to be found roving along the ground and they are more active at night. When spotlighted at night wolf spider's eyes will glow green. Scientists use this method during invertebrate surveys
Wolf spiders fact sheethttp://www.amonline.net.au/factsheets/wolf_spiders.htm
Does Australia have a bird-eating spider?
The term 'bird-eating spider' usually refers to large spiders from the family Theraphosidae. These spiders are also referred to as tarantulas. In Australia the theraphosids are represented by the whistling spiders (Selenocosmia sp.). These ground-dwelling spiders are big enough to prey on small frogs and reptiles, but are not known to eat birds. They are also known as barking spiders.
Museum of Victoria: Where did the barking spider get its name? http://www.museum.vic.gov.au/spidersparlour/faq.htm#barking
I have a pet whistling spider and want to know more about it...
There is more information about Selenocosmia species at the following websites:
South Australian Museum: Life and Adaptations to Water - Whistling spider Selenocosmia stirlingi http://www.samuseum.sa.gov.au/water/tesdes2.htm
The Whistling / Barking spider (Selenocosmia crassipes)http://www.arachnophiliac.com/burrow/whistling_barking_spider.htm
Queensland Bird-eating Spiderhttp://www.tenforward.com.au/spiders/
The Tarantulas.com website has general care information for large spiders, including spider first aid and how to deal with moulting: http://www.tarantulas.com/
Big Hairy Spidershttp://www.bighairyspiders.com/
More tarantula websites - Spider Linkshttp://www.amonline.net.au/spiders/resources/links.htm
Do we have tarantulas in Australia?
It depends on what you mean by the word "tarantula". Some people use it to describe the large hairy spiders of South and Central America. In Australia, the whistling spiders are also called tarantulas, as they are related to the American spiders. However, the word tarantula is also used to refer to huntsman spiders.
Tarantula is derived from the name of a town in Italy, Taranto. This town is the original home of the wild dance called the tarentella. During the Middle Ages, the tarentella was thought to be the way to cure the bite of a particular spider. The symptoms - known as tarantism - included severe pain, swelling, spasms, nausea and vomiting, palpitations, and fainting, along with exhibitionism, melancholia and delirium. It was hard to determine whether an actual bite had occurred or if people were merely displaying some form of madness or hysteria. Scientists later determined that many cases might indeed have been the result of a bite, although much of the fierce dancing and extreme behaviour may reflect more about the social and sexual repression at the time.
The alleged spider that caused all of these symptoms was called a tarantula, but the species was incorrectly identified. The original spider identified by the people of the time was a wolf spider (Lycosa tarantula). However, it was subsequently shown to cause little serious results when it bit people. Finally, it was shown that the real culprit was a Black Widow relative, Latrodectus tredecimguttatus, known in Southern Europe as the "malmignatte". The symptoms of this spider's bite (and of other Latrodectus species, including the Redback Spider) match the whole-body symptoms experienced during tarantism.
Information from Hillyard, P. 1994. The Book of the Spider. Hutchinson, London.
To learn about the history of the word "tarantula", and its origins, have a look at:
Tarantism episodes in Lizzano, Italyhttp://www.ba.infn.it/~zito/taranta.html
Article: Rethinking the dancing maniahttp://www.csicop.org/si/2000-07/dancing-mania.html
More tarantula websites - Spider Linkshttp://www.amonline.net.au/spiders/resources/links.htm
Do we have scorpions in Australia?
Yes we do. Scorpions are common in gardens and forests throughout eastern Australia and are found under logs, rocks and in shallow burrows in earth banks. They are nocturnal - which is why we rarely see them - but they can be disturbed during the day, especially during the prolonged wet weather. There are also species that live in the desert and others that inhabit tropical rainforests.
Scorpion Fact Sheethttp://www.amonline.net.au/factsheets/scorpions.htm
How does spider venom work in humans?
Venoms are chemicals of biological origin (i.e. made by an animal) used for the purpose of attack or defence. Venoms are made by specialised organs, such as modified salivary glands, and are delivered via specialised systems such grooved or hollow fangs. Most venoms consist of a complex mixture of chemical substances, including proteins, peptides, sugars and other substances. Venoms may affect many systems of the body. Common venom effects include paralysis, interference with blood clotting, breakdown of muscle, pain, breakdown of tissues and effects on the cardiorespiratory system (the heart and lungs).
There are basically two types of venom that have an effect on humans: neurotoxic and cytotoxic or necrotic venoms. Neurotoxic venoms work directly on the nervous system. The best known example is the venom of the Black Widow/Redback spiders (Latrodectus species). Necrotic venoms cause damage to the tissues, such as blisters and lesions. A good example is the venom of the White-tailed Spider (Lampona cylindrata). Generally, neurotoxic venoms kill more quickly than necrotic venoms.
The main effect of a neurotoxic venom is to block nerve impulses to the muscles, causing cramps and rigidity. It also overstimulates the production of the neurotransmitters, acetylcholine and norephinephrine, causing paralysis of the entire nervous system. The combined effect causes sudden and severe stress to the entire human body. Funnel-web Spider venom - known as atraxotoxin - acts directly upon the nervous system in this way.
Necrotic venoms cause skin blisters around the site of the bite, which may lead to ulcers and tissue death - necrosis. The widespread Recluse Spiders are the most toxic of the spiders that possess necrotic venom. The introduced species Loxosceles rufescens is present in Australia. Bites from some wandering spiders, including the White-tailed Spider, Wolf Spiders and the Sac Spiders (Cheiracanthum species) can also cause necrosis, but severity varies from little to acute reactions. Scientists are still determining which species cause most problems, as many spiders involved in necrotic bites have been misidentified in the past.
Venoms are complex substances, made up of several components, including proteins, sugars.
Venom links
Spider bites and venomshttp://www.amonline.net.au/spiders/dangerous/bites/index.htm
International Venom and Toxin Databasehttp://www.kingsnake.com/toxinology/
Australian Venom Research Unit (AVRU): Venoms and Antivenomshttp://www.pharmacology.unimelb.edu.au/avruweb/index.htm
What is the world's most dangerous spider?
It is hard to define which spider in the world is the most dangerous to humans. Several spiders could qualify, depending on what you mean by dangerous. Do you mean the spider with the most toxic venom, measured by its effect on newborn mice or other mammals? Or do you mean the spider that has caused the death of the most people? Those that have the strongest venom may not be encountered by humans very often, or may even have trouble piercing human skin and so are not considered to be "dangerous". Data are usually only kept on bites from spiders that are potentially deadly or cause severe reactions and these data are not recorded consistently at a national or international level. Here, we will define dangerous as "deadly".
In summary, on current evidence the most dangerous spiders in the world are funnel-web spiders (Atrax and Hadronyche species), Redback Spiders and their relations (Latrodectus species), Banana Spiders (Phoneutria species) and Recluse Spiders (Loxosceles species). In Australia, only male Sydney Funnel Web Spiders and Redback Spiders have caused human deaths, but none have occurred since antivenoms were made available in 1981.
The Australian funnel-web spiders are among the deadliest spiders in the world in the effect their bites have on humans and our primate relations (although the bite has little effect on dogs and cats). There are many species of funnel-web spiders in Australia but only male Sydney Funnel-webs have caused human deaths. There have been only 13 deaths recorded from male Sydney Funnel-webs, but up to 30-40 people are bitten by funnel-web spiders each year. Mouse spiders may have venom that is as toxic as that of some funnel-webs, as some patients have had severe reactions to their bites, although no-one has been recorded as having died from the effects of a mouse spider bite. Antivenoms are available for both funnel-web and Redback Spider bites.
A group of spiders that is dangerous in many countries belongs to the genus Latrodectus in the Family Theridiidae. In Australia we have the Redback Spider (Latrodectus hasselti). In America, a common representative of this genus is the Black Widow (Latrodectus mactans). Antivenoms are available for both funnel-web and Redback Spider bites.
A deadly spider which comes from South America is the Banana Spider, Phoneutria species. In south-eastern Brazil between 1970 and 1980, more than 7,000 people were admitted to hospital with bites from this spider. An antivenom also exists for this species.
The Recluse or Fiddleback Spider is a deadly spider belonging to the genus Loxosceles. Recluse spiders are found in many parts of the world and have been introduced into Australia. The venom of this spider can cause severe skin necrosis (eating away of the flesh) and can be fatal although not many deaths have been recorded.
How many dangerous spider bites occur in Australia each year? Has anyone died from a bite recently?
There have been no deaths in Australia from a confirmed spider bite since 1979. An effective antivenom for Redback Spiders was introduced in 1956, and one for funnel-web spiders in 1980. These are the only two spiders that have caused deaths in Australia in the past.
A spider bite is not a notifiable medical emergency, so there are no Australia-wide statistics, but the following figures give an idea of the incidence of reported bites in recent years.
Approximately 2000 people are bitten each year by Redback Spiders
Funnel-web spider antivenom has been given to at least 100 patients since 1980. Antivenom is given only when signs of serious envenomation are observed. Many spider bites are 'blank', which means that no venom has been injected.
During 2000 the New South Wales Poisons Information Centre received 4,200 calls about spiders. However not all of these would have involved actual bites. Many reported bites are not able to be identified as definitely being from a spider, and it is nearly impossible to work out what species has caused a bite without seeing a specimen of the spider responsible.
Figures are from:
Sutherland, S K and Nolch, G (2000) Dangerous Australian Animals. Hyland House, Flemington, Vic. 201 pp. ISBN 86447 076 3
NSW Poisons Information Centre The Children's Hospital at Westmead Locked Bag 4001 Westmead, NSW 2145 Emergency Phone: +612 9845 3111 Administrative Phone: +612 9845 3599 Fax: +612 9845 3597
What spiders in Australia may cause ill effects if they bite you?
In Australia, bites from at least two kinds of spiders - wolf spiders and white-tailed spiders - in some cases cause skin necrosis (eating away of the flesh). However, neither spider has caused human deaths. There are also a number of others which are thought to cause the same problem, but research is still being done to find out exactly which species do so.
Bites from many Australian spiders can cause localised reactions, with symptoms such as swelling and local pain at the site of the bite, sweating, nausea and vomiting and headaches. All of these symptoms will vary in severity depending on the age of the victim, their health, and the amount of venom that the spider was able to inject. Have a look at our spider fact sheets to find out more about individual species.
Do white-tailed spiders cause the skin condition known as necrotising arachnidism?
There is an ongoing debate among toxicologists and spider biologists about the effects and dangers of white-tailed spider bites. Most of these bites appear to cause little or no effect beyond transient local pain. However a small number of cases do cause more extensive problems. Whether this is a result of the spiders' venom or to bacteria infecting the wound at or after the time of the bite has not yet been resolved. It is also possible that some people may react badly to white-tailed spider bite, possibly because of immune system susceptibility or a predisposing medical condition.
Links
White-tailed spider fact sheethttp://www.amonline.net.au/factsheets/white_tailed_spider.htm
Medical Journal of Australia: A comprehensive summary of current knowledgehttp://www.mja.com.au/public/issues/171_2_190799/pincus/pincus.html
An article by Dr Julian Whitehttp://www.mja.com.au/public/issues/171_2_190799/white/white.html
An article by Chan and Dr White's responsehttp://www.mja.com.au/public/issues/xmas98/chan/chan.html
Clinical Toxicology page by Julian Whitehttp://www.wch.sa.gov.au/paedm/clintox/
The University of Melbourne's Australian Venom Research Unit (AVRU)http://www.pharmacology.unimelb.edu.au/ pharmwww/avruweb/aboutav.htm
References
Meier, J. & White, J. (1995) Handbook of Clinical Toxicology. CRC Press, Florida USA.
Whitehouse, R. (ed.) (1991) Australia's Dangerous Creatures Readers Digest Pty Ltd, Surry Hills NSW.
Sutherland, S. & Sutherland, J. (1999) Venomous Creatures of Australia Oxford University Press, South Melbourne.
Isbister,G. & Greay,M. (2000). "Acute and recurrent skin ulceration after spider bite" Medical Journal of Australia 172, 20 March 2000, pp.303-304
How do I control white-tailed spiders around the house?
Beyond killing or removing all white-tailed spiders that you encounter, you can try a prey reduction strategy. White-tailed spiders like to feed on Black House Spiders (Badumna insignis) in particular, but will take other spiders too. This means that you should clean up obvious spiders around the house (outside and in). This involves removing spiders from around windows, walls and verandas (by web removal and/or direct pyrethrum spray). The condition of the roof cavity and the underfloor area (if raised) should also be investigated. (from Mike Gray, Arachnologist, Australian Museum)
What is the biggest spider in the world?
The biggest spider in the world is the Goliath Spider, Theraphosa leblondi. It lives in coastal rainforests in northern South America. Its body can grow to 9 cm in length (3.5 inches) and its leg span can be up to 28 cm (11 inches). (from: Carwardine, M. 1995. The Guinness Book of Animal Records. Guinness Publishing.)
What is the biggest spider in Australia?
Australia's biggest spiders belong to the same family as the Goliath Spider. They are the whistling spiders. The northern species Selenocosmia crassipes can grow to 6 cm in body length with a leg span of 16 cm.
What is a Daddy-long-legs?
'Daddy-long-legs' is the common name for a particular group of spiders, but it is also used for a different group of arachnids - the harvestmen or opilionids. As a result, there is a lot of confusion about what people mean when they say 'daddy-long-legs'.
Daddy-long-legs: spiders The animal which most biologists call Daddy-long-legs, is a spider, Pholcus phalangioides, which belongs to the spider family Pholcidae, order Araneida, class Arachnida. It has two parts to the body, separated by a narrow waist. It has eight eyes and eight very long thin legs. Pholcids often live in webs in the corners of houses, sometimes in bathrooms. Daddy-long-legs spiders (or pholcids) kill their prey using venom injected through fangs. Digestion is external, with fluids being squirted onto the prey item and the resulting juices sucked up by the spider.
Daddy-long-legs: harvestmen The other eight-legged invertebrates that are sometimes called Daddy-long-legs, are members of the order Opiliones or Opilionida in the class Arachnida. Another common name for these arachnids is 'harvestmen'. Unlike spiders, their bodies do not have a 'waist', they do not produce silk and they normally have only one pair of eyes. They do not have venom glands or fangs, although they may produce noxious defence secretions. Most harvestmen eat smaller invertebrates but some eat fungi or plant material and others feed on carcasses of dead mammals and birds. Digestion is internal and some solid food is taken in, which is uncharacteristic for arachnids. You usually do not find harvestmen inside houses.
Are Daddy-long-legs the most venomous spiders in the world?
There is no evidence in the scientific literature to suggest that Daddy-long-legs spiders are dangerously venomous. Daddy-long-legs have venom glands and fangs but their fangs are very small. The jaw bases are fused together, giving the fangs a narrow gape that would make attempts to bite through human skin ineffective.
However, Daddy-long-legs Spiders can kill and eat other spiders, including Redback Spiders whose venom can be fatal to humans. Perhaps this is the origin of the rumour that Daddy-long-legs are the most venomous spiders in the world. The argument is sometimes put that if they can kill a deadly spider they must be even more deadly themselves. However this is not correct. Behavioural and structural characteristics, such as silk wrapping of prey using their long legs, are very important in the Daddy-long-legs' ability to immobilise and kill Redbacks. Also, the effect of the Daddy-long-legs' venom on spider or insect prey has little bearing on its effect in humans.
This myth is also debunked at the following web site:
University of California Riverside Department of Entomology: Daddy-longlegs Mythhttp://spiders.ucr.edu/daddylonglegs.html
What are banana spiders and where are they found?
Banana spider is the common name given to large (3 cm body length) active hunting spiders of the genus Phoneutria (Family: Ctenidae). These spiders live in Central and South American rainforests. They are often found in rubbish around human dwellings, as well as hiding in foliage such as banana leaves where they sometimes bite workers harvesting bananas. They have a reputation for being quite aggressive.
Other names for this spider include: Kammspinne, Bananenspinne, Wandering spider, and Aranha armadeira.
The venom of this spider is neurotoxic - acting on the nervous system - and causes little skin damage. Symptoms of a bite include immediate pain, cold sweat, salivation, priapism, cardiac perturbations and occasional death. Research suggests it is similar in action to a-latrotoxin, which is produced by spiders of the Family Latrodectidae, such as the Redback and Black Widow Spiders.
For more information about spider bites:
NetDoctor: Scorpion stings and spider bites (mentions Banana Spider)http://www.netdoctor.co.uk/travel/diseases/scorpions_and_spiders.htm
Another spider that seems to have been given the common name "banana spider" is actually a completely unrelated species of orb weaving spider from Florida. This is a good example of why it is more useful to use scientific names when you are trying to find information on different animals or plants.
Florida's Golden Silk Spider(Nephila clavipes) - also known as a Banana Spider:http://pelotes.jea.com/spiders.htm
How do I find out about spiders in New Zealand?
The following New Zealand arachnologist (spider biologist) has offered to respond to inquiries from people interested in New Zealand spiders:
Dr Phil SirvidEntomology Section Museum of New Zealand Te Papa Tongarewa PO Box 467 Wellington, New Zealand ph: +644 381 7362 fax: +644 381 7310 email: Phils@tepapa.govt.nz
There is a book on New Zealand spiders:
Forster, Ray and Lyn. 1999. Spiders of New Zealand and Their Worldwide Kin. University of Otago Press, ISBN 1 877133 79 5
What about white-tailed spiders in New Zealand?
Dr Phil Sirvid has this to say about white-tailed spiders in New Zealand:
"We have two species of white-tails in New Zealand - Lampona cylindrata and Lampona murina. They are both very similar in appearance, and can really only be separated from one another by viewing them under a microscope and examining certain features that aren't apparent to the naked eye.
Both have been introduced from Australia.
L. murina has been in the North Island of New Zealand for [over] 100 years, and has also been introduced to the Kermadecs, Lord Howe Island and Norfolk Island. I wouldn't be surprised if it's in the Chatham Islands as well. In Australia, this species is recorded along the East Coast from northern Queensland down through New South Wales and Victoria.
L. cylindrata had only been found occasionally in the South Island until the 1980s. About this time it seemed to spread rapidly throughout the South Island's main urban centres, and is known to occur as far south as Dunedin. This species is found along the southern part of Australia from Western Australia, through South Australia, Victoria and Tasmania, as well as in New South Wales and Queensland."

The View of Mind in Antiquity

550 BC - Pythagoras - the mathematical mind.
Pythagoras (582-500 BC) suggested that matter and mind are mystically connected. Logic, numbers, spirit, and soul were expressions of the same reality. He thought the soul to be immortal and wandering on a path of transmigration from one body to another. The Pythagoreans had a geometrical conception of the world. They believed that mind is attuned to the processes of nature, in particular to the laws of mathematics. Mathematics is seen as the true essence of mind.
450 BC - Anaxagoras - the universal intelligence.
Anaxagoras (500-428 BC) introduced the concept of "Nous" (mind, reason) into Greek philosophy. Nous, the eternal mind, transforms chaos into order and through it the material world comes into being. The primordial One produces forms of multiplicity through dichotomisation. This process is originated and controlled by the power of mind, or Nous. According to Anaxagoras, mind is infinite and self-organizing. It is not intermixed with anything, but pure in its being.
450 BC - Alcmaeon - the dissected brain.
The Greek physician Alcmaeon (around 450 BC) concluded from his studies of dissection that the brain is the centre of intelligence. In doing so, he contradicted the mainstream theory of his time, which held that the heart is the centre of intelligence and seat of the soul. Alcmaeon also surmised that optic nerves conduct light from the eye to the brain and that the eye itself contains light.
400 BC - Hippocrates - the four humours.
Hippocrates (460-377 BC), the founder of Western medicine, is famous for the Hippocratic oath. He invented the notion of the four humours, black bile, yellow bile, phlegm, and sanguine, which he equated with the four elements. Hippocrates thought that disease arises from an imbalance of these four humours and that people can be healed by restoring their proper proportions. The dominating humour was also thought to be responsible for the temperament (black bile = melancholy, yellow bile = bitterness and irascibility, phlegm = equanimity, and sluggishness, sanguine = passionate and cheerful).
Hippocrates correctly identified epilepsy as a brain disorder. He held that not only thought and reason, but also feelings and moods originate in the brain: "Men ought to know that from the brain, and from the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, grievances, and tears. Through it...we...think, see, hear, and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant."
400 BC - Plato - ideal forms and reason.
Plato (428-347 BC) plays an important role in the history of epistemology. His theory of ideas, which he presented in the famous cave allegory, can be seen as a precursor of both medieval realism and later idealism. Plato held that all forms of the physical world are merely instances of perfect forms in an ideal world. The idea of a table is the supreme form of table of which there is only one. It contains in itself all actual tables of the physical world. The knowledge of ideas, or supreme forms, provides intellectual and ethical guidance for humans. Plato thought that perfect forms have an actual metaphysical existence.
Plato divided the human mind into three parts: the rational part, the will, and the appetites. Ideally the will supports the rational element, which in turn controls the appetites. If the rational element is not developed, the individual behaves immorally, hence immorality is a consequence of ignorance. Furthermore, Plato distinguished between two kinds of conscious thought: opinion and knowledge. He said that all assertions about the outside world are necessarily based on sense experience, and are therefore only opinions. In contrast, he described knowledge as a higher form of awareness, because it is gained from reason rather than from sense experience.
350 BC - Aristotle - the three souls.
Aristotle (384-322 BC) equated mind with reason and thought it to be a property of the living soul. In contrast to Plato, who believed that body and soul are two different entities, he held that mind and body are intertwined in all living beings and are thus inseparable. Growth, purpose and direction are therefore built into nature. Aristotle proposed three forms of soul: 1. the vegetative soul possessed by plants in that they grow and decay and enjoy nutriment, but they do not have motion and sensation, 2. the animal soul which bestows animals with motion and sensation, and 3. the rational soul which is the conscious and intellectual soul peculiar to man. Each higher form possesses in full the attributes of the lower souls, which makes human beings the only possessor of all three types. Aristotle also proposed a theory of memory surmising that the processes involved in short term memory (immediate recall) differ from those involved in long-term memory.
300 BC - Herophilus - the beginning of neuroscience.
The Greek anatomist Herophilus (335-280 BC) studied the human brain and recognised it as the centre of the nervous system. He distinguished the cerebrum and cerebellum and named the brain as the source of thought. Herophilus also made the first contribution to the field of neuroscience by distinguishing between sensory and motor nerves and by performing the most thorough study of brain anatomy attempted until the Renaissance.
300 BC - Pyrrho - scepticism as a state of mind.
The founder of the Greek school of scepticism, Pyrrho (360-272), stated that human mind is incapable of attaining true knowledge of anything, because ultimate reality is incomprehensible. Therefore, there is no objective knowledge, but only opinion. The best attitude one can develop in view of this fact, is to suspend any judgment completely, to free oneself from passions, and to calm one's mind. The idea that no person's judgment is more correct than that of another goes back to the first Sophist, Protagoras, who lived around 450 BC. Pyrrho developed scepticism into a more elaborate and consistent system of thought.
250 BC - Erasistratus - the brain and the vital spirit.
Erasistratus (300-260 BC) was an anatomist who worked one century after Aristotle. He found three tubular structures going to every organ of the body: an artery, a vein, and a nerve. He expanded Herophilus's theory of motor and sensory nerves by adding the thesis that all nerves are connected to and controlled by the brain. Erasistratus saw the brain as a mechanism for distilling the pneuma (the vital spirit), which he thought was flowing from the heart up to the brain and then down to the organs.
150 AD - Galen - the great Greek doctor.
Galen (129-199 AD) was the most influential physician of antiquity, after Hippocrates. He influenced medicine profoundly until about the 17th century. Galen synthesised the thought of Pythagoras, Plato and Aristotle and built upon the discoveries of Hippocrates and Erasistratus. He proved that the arteries carry blood instead of air (as the Greeks formerly presumed); and he demonstrated that the brain controls motion and voice. Galen further assigned the three largest organs of the body to be the seat of the three Aristotelian souls; the liver as the seat of the vegetative soul, the heart as the seat of the animal soul, and the brain as the seat of the rational soul.
For Galen, the rational soul was divided into the faculties of imagination, reason, and memory. He located these three faculties in the ventricles of the brain. Because the function of the brain was to distribute animal spirit throughout the body, to Galen it seemed that the fluid filled ventricles perform this function and thus disregarded the white and grey matter surrounding the ventricles. According to Galen, the brain receives vital spirit (pneuma) from the heart, which is mixed into the sanguine humour (blood). The brain then separates the animal spirit out and stores it in the ventricles, from where it is distributed throughout the body via the nerves. This mechanism of circulating pneuma controls muscles, organs, and all of the body's activities.
250 AD - Plotinus - the emanation of mind from the Absolute.
Plotinus (204-270 AD) rejected Aristotle's notion of the soul not being able to exist without the body. Building mainly on Plato, he said that mind is a prisoner of the body. Plotinus held that soul is the immortal part of mind. It survives the death of the body and enters a series of transmigration from one body to another. Consequently, the soul is the only abiding reality of the human condition. Plotinus formulated a theory of emanation according to which mind emanates originally from the Absolute Being, or the One, and then forms Nous, the universal intelligence, from which the world spirit is formed in turn. Human mind, animal mind, vegetative mind, and finally matter all emanate from the world spirit. They are different manifestations of one universal intelligence.
400 AD - St. Augustine - the illuminated mind.
The church father St. Augustine (354-? AD) had an interesting idea about mind. He said that the human mind couldn't gain knowledge from sense perception alone. He also rejected Plato's theory of ideas. Instead, according to Augustine, knowledge is acquired on account of divine illumination. He argued as follows: The shape of an object such as a tree can only be seen by the eye, because the object is bathed in light. Similarly the mind can only recognise truths, such as the mathematical truth 1+1=2, because it is illuminated by the light of eternal reason. This light is not so much the source of ideas and knowledge, but the condition under which mind is able to recognise the quality of truth. In spite of the simplicity of this idea, or perhaps due to it, Augustine had a tremendous influence on the philosophers and theologians of the Middle Ages.

What is Mind

What is mind? What is consciousness? There seems to be no single answer that explains the phenomenon of mind. The contemporary views of philosophy, psychology, neuroscience, and cybernetics all come up with different interpretations of mind and consciousness.
It is a bit ironic that something we claim to possess is so hard to explain. Obviously mind cannot be an object of itself. Or can it? If we should one day understand the chemical and electrical processes in the brain completely, would this explain mind? Would this understanding account for all faculties including intelligence, consciousness, emotion, and volition?
On the following pages we will try to give some possible answers to this question. On the topic of consciousness, the British psychologist Stuart Sutherland once wrote: "Consciousness is a fascinating but elusive phenomenon; it is impossible to specify what it is, what it does, or why it evolved. Nothing worth reading has been written on it." - Hopefully this won’t keep you from reading on.
Epistemology and psychology.
The investigation of mind is closely related to the field of epistemology, the part of philosophy that deals with knowledge and whose principal question is: "What can we know?" Epistemology is not so much preoccupied with the process of accumulating knowledge, but with the validity of knowledge and how we can achieve certainty about it. It includes the branch of philosophy that the ancients called logic, which deals with language and thought. Bertrand Russell once remarked tellingly that the theory of knowledge is a product of doubt. Things seem to speak in favour of Russel's view – most philosophers find it easier to determine what we cannot know rather than what we can know. Perhaps the theory of knowledge should then be called "theory of ignorance."
The other question about knowledge is: "How do we know?" This question pertains to the mechanics of sensation, perception, cognition, memory, and physical brain processes. It also touches upon language and thought, but it takes a more scientific approach to these issues. The latter question is primarily asked by psychologists and neuroscientists, although philosophers recently took a renewed interest in the workings of the brain. Since both approaches are beneficial in their own way, we shall not limit ourselves to a particular one.
Defining mind.
On the surface, the attempt to define mind seems superfluous, since it is so fundamental to us. However, the explicit verbalisation of an intuitive understanding of mind is fairly difficult, because it requires us to transform the subjective first-person experience into an objective third-person description.
The American Heritage Dictionary of the English Language defines mind as follows: "The collective conscious and unconscious processes in a sentient organism that direct and influence mental and physical behaviour." This definition attributes mind to sentient organisms and identifies it with processes that control behaviour. According to the view of contemporary science, these are brain and nerve processes, cognition, motor, and sensory processes.
The faculties of mind.
The scientific definition is in agreement with the physicalist view of mind that equates mental phenomena with neuronal activity. The definition is also in agreement with the functionalist view of psychology, which frequently divides mind into distinct faculties (as shown on the right) and then investigates those faculties individually. Some of these functions can be mapped to particular brain areas.
Dividing mind into faculties involves a great deal of abstraction, because in reality there are no clear boundaries between them. For example, the simple process of catching a ball involves sensation, cognition, and reasoning processes without there being a clear separation between the single actions of seeing the ball, calculating its speed and angle, and coordinating body movements.
Another more serious problem is that the scientific definition makes no reference to conscious experience and its subjective qualities. It is not easy to see how the experience of sensations and feelings could be part of the physical world. For example, how can emotions, such as love (affection, attraction) and hate (aversion, repulsion) which we seem to share with some animals, be described in terms of physical structures and processes?
Is the scientific definition viable in philosophy?
Perhaps it is necessary to ask whether science is capable of explaining mind at all.
Unfortunately the scientific definition falls short of one important quality: spirit. The scientific view is difficult to apply, for instance, in the context of sociology where we speak of the mental qualities of a group or population (the nation's mind, group mind, team spirit). It is also difficult to apply in the context of religion, where mind and spirit are associated with transcendental concepts such as the immortal soul, the world mind, the holy spirit, etc.
The materialist notion of mind is possibly too limited for a general philosophical discourse. It would be extremely difficult to discuss topics that involve metaphysical, ontological, and phenomenological accounts of mind. A purely materialist understanding of mind would simply evade these topics. More exotic fields of knowledge, such as theology, religion, and parapsychology do not harmonise with the scientific view of mind either. Hence, we shall postpone further attempts to define mind and as yet allow the largest possible meaning of the word, perhaps in the sense of the German word "Geist", which means both mind and spirit.
Philosophy of mind.
The philosophy of mind is the branch of philosophy that deals with mind and consciousness. It falls outside the four classical branches, metaphysics, epistemology, ethics, and aesthetics, but it relates especially to the first two. The ancients did not see it as a separate discipline, although the systematic investigation of certain aspects of mind began with the study of reason in Plato and Aristotle. During the middle ages, the philosophy of mind lingered within the confines of Christian epistemology. Important theoretical advances began to take shape only in the 17th century with Descartes and Hobbes. The philosophy of mind flourished during the late 18th and 19th century (Hegel, Darwin, Wundt, James) just before it spawned psychology, while the philosophical currents of the time flowed into the schools of phenomenology and existentialism. Psychology has ruled the field for some time during the 20th century, however, the philosophy of mind experienced a small renaissance lately due to the appearance of computer technology and other new disciplines such as cybernetics and the neurosciences. These developments brought up the question whether a machine can emulate mind and whether it can become conscious.

THE UNIVERSE

In the beginning, the Earth was flat. At least it appeared so to its first observers, hunters and gatherers, and members of early civilisations. Not totally unreasonable, one would think, because the curvature of our planet's surface is not immediately apparent. Yet we know, and it must have been not totally inconceivable even to the archaic tribesmen, that our senses occasionally deceive us. The Earth being flat brings about the problem that it must end somewhere, unless we imagine it to extend infinitely. Infinity is a rather unfathomable conception and, hence, right down to the Middle Ages people were afraid of the possibility of falling off the Earth's boundaries.
Early cosmogonies.
What lies beyond these boundaries was largely unknown and open to speculation. The starry heavens were a source of endless wonder and inspiration. Peoples from all parts of the world created their own myths, inspired by the skies and the celestial bodies. Their cosmogonies can be seen as an attempt to explain their own place in the universe. Six thousand years ago, the Sumerians believed that the Earth is at the centre of the cosmos. This belief was later carried into the Babylonian and Greek civilisations.
According to the history books, it was the Greeks who first put forward the idea that our planet is a sphere. Around 340 BC, the Greek philosopher Aristotle made a few good points in favour of this theory in On the Heavens. First, he argued that one always sees the sails of a ship coming over the horizon first and only later its hull, which suggests that the surface of the ocean is curved. Second, he realised that the eclipses of the Moon were caused by the Earth casting its shadow on the moon. Obviously, the shadow would not always appear round, if the Earth was a flat disk, unless the Sun was directly under the centre of the disk. Third, from their travels to foreign countries, the Greeks knew that the North Star appears higher on the northern firmament and lower in the south. Aristotle explained this correctly with the parallactic shift that occurs when moving between two observation points on a spherical object. Among the Greeks, the heliocentric system was proposed by the Pythagoreans and by Aristarchus of Samos (ca. 270 BC). However, Aristotle dismissed the case for heliocentrism.
Ptolemy's geocentric model of the cosmos.
The influence of Aristotle was significant. Around 150 AD, Claudius Ptolemaeus (Ptolemy) elaborated Aristotle's ideas into a complete cosmological model. He thought that the Earth was stationary at the centre of the universe and that the Sun, the stars, and all planets revolve around it in circular orbits, hence, the model is sometimes referred to as the geocentric system. Ptolemy was aware that the postulation of perfect circular orbits contradicted observation, because the planets' motion, size and brightness varied with time. To account for the observed deviations, he introduced the idea of epicycles, smaller circular orbits around imaginary centres on which planets were supposed to move while describing a revolution around Earth. This enabled astronomers to make reasonably accurate predictions about the movement of the celestial bodies, and consequently the Ptolemaic model was a great success. The system was later adopted by the Christian Church and became the dominant cosmology until the 16th century.
Ptolemy's model of the universe was that of an onion with the Earth at its centre and stars arranged in layers around it. The outer layer was thought to be like a crystal to which the fix stars were attached. The hypothesis of epicycles accounted for the observable deviations.
Copernicus.
In 1514 the Polish astronomer Nicolaus Copernicus (1473-1543) put forward an alternative model, referred to as the heliocentric system, in which the Sun is at the centre of the universe, and all planets, including Earth, revolve around it. The further apart a planet is from the Sun, the longer it takes to complete a revolution. Copernicus said that the ostensible movement of the Sun is caused by the Earth rotating around its north-to-south axis. The heliocentric system got rid of Ptolemy's obscure epicycles, whose main weakness was that they did neither account for the observed backward motion of Mars, Jupiter, and Saturn, nor for the fact that Mercury and Venus never moved more than a certain distance from the Sun. Unfortunately, the Copernican system was not inherently simpler than the geocentric system; and it did not immediately render more accurate calculations of the planet's motion.
Galileo.
The end of the Ptolemaic theory came with the invention of the telescope. With the help of this device, Galileo Galilei (1564-1642) discovered the four largest Jupiter moons. The existence of these moons demonstrated beyond doubt that not all celestial bodies revolve around the Earth, contrary to Ptolemy’s theory. Galileo confirmed the Copernican model and thus initiated a scientific revolution of great importance, much to the discontent of the Roman Catholic Church. Unsurprisingly, Galileo struggled with church authorities during much of his lifetime. In 1594 the German astronomer Johannes Kepler (1571-1630) refined the heliocentric model in his book Mysterium Cosmographicum by showing that planets move on elliptical, rather than circular orbits. Kepler also prepared the idea of gravity by explaining that the Sun exerts a force on planets that diminishes inversely with distance and causes them to move faster on their orbits, the closer they come to the Sun. This theory finally allowed predictions that matched observations.
Kepler and Newton: The paradox of the collapsing universe.
Kepler’s model became the accepted 17th century cosmology, until Isaac Newton further refined Kepler's notion of the forces between celestial bodies. Newton postulated the law of universal gravitation that applied to all bodies, whether in space or on Earth, and he supplied the mathematical foundation for it. According to Newton, bodies attract each other proportionally with their size and inverse proportionally with the square of the distance between them. He went on to demonstrate that according to this law, planets move on elliptical orbits, as previously assumed by Kepler. Unfortunately, one consequence of this theory is that the stars of the universe attract each other and thus must eventually collapse onto each other. Newton was not able to give a plausible explanation for why this did not happen.
To counter this paradox, it was inferred that the universe is infinite in space, and thus contains an infinite number of evenly distributed stars, which would on the whole create a gravitational equilibrium. This assumption, however, would still imply instability. If the balance is disturbed in one region of space, the nearest stars collapse and the gravitational pull of the resulting more massive body draws in the next cluster of stars. Clusters would collapse like a house of cards and eventually draw in the entire universe. Today we know that this is not the case, because the universe is not static as Newton thought. The cosmos is in a state of expansion and therefore, gravitational collapse is prevented.
Is the universe infinite in space and time?
The question of whether the universe has boundaries in time and space has captivated the imagination of mankind since early times. Some would say the universe had existed forever, while others would say that the universe was created and thus had a beginning in time and space. The second thesis immediately raises the question what exists beyond its temporal and spatial bounds. Could it be nothingness? But then, what is nothingness? The absence of matter, or the absence of space and time itself? The German philosopher Immanuel Kant (1724-1804) dealt intensively with this question. In his book Critique of Pure Reason he came to the conclusion that the question cannot be answered reliably within the limits of human knowledge, since thesis and antithesis are equally valid. Kant thought instead of time and space as fundamental aspects of human perception.
Big Bang - the birth of our universe.
Fast forward: Despite Kant's doubts thereto, it appears that modern cosmology has answered the above question. The universe we can observe is finite. It has a beginning in space and time, before which the concept of space and time has no meaning, because spacetime itself is a property of the universe. According to the Big Bang theory, the universe began about twelve to fifteen billion years ago in a violent explosion. For an incomprehensibly small fraction of a second, the universe was an infinitely dense and infinitely hot fireball. A peculiar form of energy that we don't know yet, suddenly pushed out the fabric of spacetime in a process called "inflation", which lasted for only one millionth of a second. Thereafter, the universe continued to expand but not nearly as quickly. The process of phase transition formed out the most basic forces in nature: first gravity, then the strong nuclear force, followed by the weak nuclear and electromagnetic forces. After the first second, the universe was made up of fundamental energy and particles like quarks, electrons, photons, neutrinos and other less familiar particles.
About 3 seconds after the Big Bang, nucleosynthesis set in with protons and neutrons beginning to form the nuclei of simple elements, predominantly hydrogen and helium, yet for the first 100,000 years after the initial hot explosion there was no matter of the form we know today. Instead, radiation (light, X rays, and radio waves) dominated the early universe. Following the radiation era, atoms were formed by nuclei linking up with free electrons and thus matter slowly became dominant over energy. It took 200 million years until irregularities in the primordial gas began to form galaxies and early stars out of pockets of gas condensing by virtue of gravity. The Sun of our solar system was formed out of such a pocket of gas in a spiral arm of the Milky Way galaxy roughly five billion years ago. A vast disk of gas and debris swirling around the early Sun gave birth to the planets, including Earth, which is between 4.6 and 4.5 billion years old. This is -in short- the history of our universe according to the Big Bang theory, which constitutes today's most widely accepted cosmological viewpoint.
What speaks in favor of the Big Bang theory?
A number of different observations corroborate the Big Bang theory. Edwin Hubble (1889-1953) discovered that galaxies are receding from us in all directions. He observed shifts in the spectra of light from different galaxies, which are proportional to their distance from us. The farther away the galaxy, the more its spectrum is shifted towards the low (red) end of the spectrum, which is in some way comparable to the Doppler effect. This redshift indicates recession of objects in space, or better: the ballooning of space itself. Today, there is convincing evidence for Hubble's observations. Projecting galaxy trajectories backward in time means that they converge to a high-density state, i.e. the initial fireball.
If two intelligent life forms in two different galaxies look at each other’s galaxy, they perceive the same thing. The light of the other galaxy appears redshifted in comparison to nearer objects. This is caused by ballooning space that stretches the wavelength of emitted light. The magnitude of this effect is proportional to the distance of the observed galaxy.
According to the Copernican cosmological principle, the universe appears the same in every direction from every point in space, or in more scientific terms: The universe is homogeneous and isotropic. There is overwhelming evidence for this assertion. The best evidence is provided by the almost perfect uniformity of the cosmic background radiation. This observed radiation is isotropic to a very high degree and is thought to be a remnant of the initial Big Bang explosion. The background radiation originates from an era of a few hundred thousand years after the Big Bang, when the first atoms where formed. Another piece of evidence speaking in favour of Big Bang is the abundance of light elements, like hydrogen, deuterium (heavy hydrogen), helium, and lithium. Big Bang nucleosynthesis predicts that about a quarter of the mass of the universe should be helium-4, which is in good agreement with what is observed.
Will the universe expand forever?
On basis of our understanding of the past and present universe, we can speculate about its future. The prime question is whether gravitational attraction between galaxies will one day slow the expansion and ultimately force the universe into contraction, or whether it will continue to expand and cool forever. The current rate of expansion (Hubble Constant) and the average density of the universe determine whether the gravitational force is strong enough to halt expansion. The density required to halt expansion (=critical density) is 1.1 * 10^-26 kg per cubic meter, or six hydrogen atoms per cubic meter; the relation "actual density" / "critical density" is called Omega. With Omega less than 1, the universe is called "open", i.e. forever expanding. If Omega is greater than 1 the universe is called "closed", which means that it will contract and eventually collapse in a Big Crunch. In the unlikely event that Omega = 1, the expansion of the universe will asymptotically slow down until it becomes virtually imperceptible, but it won't collapse.
Big Bang - Big Crunch?
Some scientists think it not impossible that the universe is oscillating between eras of expansion and contraction, where every Big Bang is followed by a Big Crunch. Stephen Hawking (born 1942) pointed out the possibility that such an oscillating universe must not necessarily start and end in singularities, i.e. questionable points in spacetime where physical theories, such as General Relativity, break down while energy and density levels approximate infinity. Although everything points towards Big Bang, the future reversal and contraction of the universe is rather uncertain. Big Crunch is at most a hypothesis, because only about 1/100th of the matter needed for Omega=1 can be observed.
In spite of this, galaxies and star clusters behave as if they would contain more matter than we can see. It is almost as if these objects were engulfed by invisible matter. This "dark matter" that cannot be accounted for is one of the open questions in cosmology. Dark matter makes is thought to make up 23% of the universe.
Big Rip!
Today, most cosmologists believe there is not enough matter in the universe to halt and revert expansion. Robert Caldwell of Dartmouth University has recently suggested a third alternative for the fate of the universe. His Big Rip scenario is based on astronomical observations made in the late 1990s according to which a mysterious force, labelled dark energy, is responsible for the expansion of the universe. Dark energy makes up 73% of the universe. If the rate of acceleration increases, there will be a point in time at which the repulsive force becomes so strong that it overwhelms gravity and the other fundamental forces. According to Caldwell, this will happen in 20 billion years. "The expansion becomes so fast that it literally rips apart all bound objects," Caldwell explains. "It rips apart clusters of galaxies. It rips apart stars. It rips apart planets and solar systems. And it eventually rips apart all matter." Even atoms would be torn apart in the last 10-19 seconds before the end of time. –Whether or not this scenario will become true is to be decided by future research. Until then, the field is open to speculation.

RELATIVITY

The notion of relativity is not as revolutionary as many believe. In fact, spatial relativity is part of our everyday experience. Spatial relativity, also called Galilean relativity in honour of Galileo who first formulated the concept of relative motion, is often confused with Einstein's theories. Galileo simply described the fact that an observer in motion sees things differently from a stationary observer, because he has a different spatial coordinate system, or "reference frame" in Relativity speak. It might sound more complicated than it actually is. Consider the following example:

Galilean relativity: the train example (courtesy of Stephen Hawking).

Two people riding on a train from New York to San Francisco play a game of ping-pong in the sport compartment of the train. Lets say, the train moves at 100 km per hour (= 27.8 m/s) and the two players hit the ball at a speed of two meters per second. In the reference frame of the players, the ball moves back and forth at this particular speed. For a stationary observer standing beside the railroad, however, things look quite different. In his reference frame the ball moves at 29.8 m/s when it is played forward in the direction where the train is heading, while it moves at 25.8 m/s in the same direction when it is played backwards. Thus he doesn't see the ball moving backward at all, but always moving towards San Francisco. For an observer in outer space, things look again totally different because of the Earth's rotation, which is opposite to the train's movement; therefore the outer space observer always sees the ball moving East.

Einstein's new concept of relativity.

Einstein's Relativity differs from classical relativity, because of the way he looked at time. Before Einstein, people thought time to be absolute, which is to say that one big clock measures the time for the entire universe. Consequently one hour on Earth would be one hour on Mars, or one hour in another galaxy. However, there was a problem with this concept. In an absolute time frame the speed of light cannot be constant. Roemer found that the speed of light is finite and has a certain, quantifiable velocity (usually abbreviated with "c"), which at first implies Galilean relativity. This would mean that while the Earth rotates at a velocity of v, light emitted in the direction of the Earth rotation must be c + v, while light emitted in the opposite direction would travel at c - v, relative to an outside observer.

In 1881, A. Michelson conducted an experiment which proved that this is not the case. With the help of an apparatus that allowed measuring minute differences in the speed of light by changes in the resulting interference patterns, Michelson observed that the speed of light is always the same. No changes whatsoever. The experiment has been repeated later with greater precision by Michelson and E.W. Morley.
Special Relativity published in 1905.

Numerous attempts were made at reconciling these discrepancies, yet they were all unsuccessful, until Einstein solved the dilemma with his famous paper On the Electrodynamics of Moving Bodies in 1905, in which he developed his Special Relativity Theory. Special Relativity is an extremely elegant construct that deals with things moving near or at the speed of light. Surprisingly, the new concept of space and time that arises from Relativity is based only on two simple postulates: 1. The laws of physics are the same in all inertial (=non-accelerating) reference frames, and 2. The speed of light in free space is constant.

It is a matter of common experience that one can describe the position of a point in space by three numbers, or coordinates. For the purpose of explaining the relativistic model, Einstein added time as a fourth component to the coordinate system, and the resulting construct is called spacetime. Just as there is an infinite number of 3-D reference frames in Galilean relativity, there is an infinite number of 4-D spacetime reference frames in Einstein's theory. This is to say that Einstein put an end to absolute time. The revolutionary insight lies in the conclusion that the flow of time in the universe does indeed differ depending on one's reference frame.


Albert Einstein (1879-1955)
German physicist Albert Einstein published his papers on Relativity Theory between 1905 and 1916. He became internationally noted after 1919 and was awarded the Nobel Prize in 1921. Einstein emigrated to the USA when Hitler came to power in Germany.

Einstein: "Relativity teaches us the connection between the different descriptions of one and the same reality."

In his usual humble way, Einstein explained how he reinvented physics: "I sometimes ask myself how it came about that I was the one to develop the theory of Relativity. The reason, I think, is that a normal adult stops to think about problems of space and time. These are things which he has thought about as a child. But my intellectual development was retarded, as a result of which I began to wonder about space and time only when I had already grown up." On Relativity, he said: "Relativity teaches us the connection between the different descriptions of one and the same reality."

This view of Relativity, that there are different realities, has been picked up unanimously by the public, and hence, has taken on a far greater meaning than that of the original scientific theory, the focus of which was -strictly speaking- on mechanics and electrodynamics. This astonishing success was at least in part due to Einstein's personality. He understood himself as a philosopher as much as a scientist, and he was ready to discuss philosophical issues at any time, particularly matters involving Relativity. The philosophical aspect of Relativity forced people to think differently about the universe. Suddenly, the cosmos was not a God-created clockwork anymore, but a totality of disparate realities with the same basic natural laws.
E=mc² - Energy equals mass times the speed of light squared.

An outstanding feature of Special Relativity is its mass-energy relation, which is expressed in the well-known formula: E=mc².

Click on this button to hear Einstein explaining his famous formula E=mc² (.au, 426 kb)
Einstein derived this relation in an attempt to reconcile Maxwell's electromagnetic theory with the conservation of energy and momentum. Maxwell said that light carries a momentum, which is to say that a wave carries an amount of energy. Due to the principle of conservation of momentum, if a body emits energy in the form of radiation, the body loses an equivalent amount of mass that is given by E/c². This describes the relation between energy and mass.

According to the conservation principle, in a closed system the sum of mass and its energy equivalent is always the same. The mass-energy relation tells us that any change in the energy level of an object necessarily involves a change in the object's mass and vice-versa. The most dramatic consequences of this law are observed in nature, for example in nuclear fission and fusion processes, in which stars like the Sun emit energy and lose mass. The same law also applies to the forces set free in the detonation of an atomic bomb.
Was Einstein involved in the development of the atomic bomb?

Einstein was not directly involved in the creation of the atomic bomb, as some people assume. His credits are rather being the one who provided the theoretical framework. In 1939, Einstein and several other physicists wrote a letter to President Franklin D. Roosevelt, pointing out the possibility of making an atomic bomb and the peril that the German government was embarking on such a course. The letter, signed only by Einstein, helped lending urgency to efforts in the creation of the atomic bomb, but Einstein himself played no role in the work and knew nothing about it at the time.

General Relativity published in 1916.

Eleven years after On the Electrodynamics of Moving Bodies, Einstein published his second groundbreaking work on General Relativity, which continues and expands the original theory. A preeminent feature of General Relativity is its view of gravitation. Einstein held that the forces of acceleration and gravity are equivalent. Again, the single premise that General Relativity is based on is surprisingly simple. It states that all physical laws can be formulated so as to be valid for any observer, regardless of the observer's motion. Consequently, due to the equivalence of acceleration and gravitation, in an accelerated reference frame, observations are equivalent to those in a uniform gravitational field.

This led Einstein to redefine the concept of space itself. In contrast to the Euclidean space in which Newton’s laws apply, he proposed that space itself might be curved. The curvature of space, or better spacetime, is due to massive objects in it, such as the sun, which warp space around their gravitational centre. In such a space, the motion of objects can be described in terms of geometry rather than in terms of external forces. For example, a planet orbiting the Sun can be thought of as moving along a "straight" trajectory in a curved space that is bent around the Sun.

On the following pages we will examine spacetime and other fascinating aspects of Relativity in some detail and see how Relativity leads us to new insights about the structure and the creation of the universe.

FAQ

What is light?

Light is a phenomenon that has particle and wave characteristics. Its carrier particles are called photons, which are not really particles, but massless discrete units of energy.

What is the speed of light?

The speed of light is 299,792,458 m/s in a vacuum. The symbol used in Relativity for the speed of light is "c", which probably stands for the Latin word "celeritas", meaning swift.

Is the speed of light really constant?

The speed of light is constant by definition in the sense that it is independent of the reference frame of the observer. Light travels slightly slower in a transparent medium, such as water, glass, and even air.

Can anything travel faster than light?

No. In Relativity, c puts an absolute limit to speed at which any object can travel, hence, nothing, no particle, no rocket, no space vehicle can go at faster-than-light (=superluminal) speeds. However, there are some cases where things appear to move at superluminal speeds, such as in the following examples: 1. Consider two spaceships moving each at 0.6c in opposite directions. For a stationary observer, the distance between both ships grows at faster-than-light speed. The same is true for distant galaxies that drift apart in opposite directions of the sky. 2. Another example: Consider pointing a very strong laser on the moon so that it projects a dot on the moon's service and then moving the laser rapidly towards Earth, so that it points on the floor in front of you. If you accomplish this in less than one second, the laser dot obviously travelled at superluminal speed, seeing that the average distance between the Earth and the Moon is 384,403 km.

What is matter?

The schoolbook definition would be: Matter is what takes up space and has mass. Matter as we know it is composed of molecules, which themselves are built from individual atoms. Atoms are composed of a core and one or more electrons that spin around the core in an electron cloud. The core is composed of protons and neutrons, the former have a positive electrical charge, the latter are electrically neutral. Protons and neutrons are composed of quarks, of which there are six types: up/down, charm/strange, and top/bottom. Quarks only exist in composite particles, whereas leptons can be seen as independent particles. There are six types of leptons: the electron, the muon, the tau and the three types of neutrinos. The particles that make up an atom could be seen as a stable form of locked up energy. Particles are extremely small, therefore 99.999999999999% (or maybe all) of an atom's volume is just empty space. Almost all visible matter in the universe is made of up/down quarks, electrons and (e-)-neutrinos, because the other particles are very unstable and quickly decay into the former.

How fast does an electron spin?

An electron in a hydrogen atom moves at about 2.2 million m/s. With the circumference of the n=1 state for hydrogen being about 0,33x10-9 m in size, it follows that an n=1 electron for a hydrogen atom revolves around the nucleus 6,569,372 billion times in just one second.

Are quarks and leptons all there is?

Not really. Fist of all, quarks always appear in composite particles, namely hadrons (baryons and mesons), then there is antimatter, and finally there are the four fundamental forces.

What is antimatter?

The existence of antimatter was first predicted in 1928 by Paul Dirac and has been experimentally verified by the artificial creation of the positron (e+) in a laboratory in 1933. The positron, the electron's antiparticle, carries a positive electrical charge. Not unlike the reflection in a mirror, there is exactly one antimatter particle for each known particle and they behave just like their corresponding matter particles, except they have opposite charges and/or spins. When a matter particle and antimatter particle meet, they annihilate each other into a flash of energy. The universe we can observe contains almost no antimatter. Therefore, antimatter particles are likely to meet their fate and collide with matter particles. Recent research suggests that the symmetry between matter and antimatter is less than perfect. Scientists have observed a phenomenon called charge/parity violation, which implies that antimatter presents not quite the reflection image of matter.

What are the four fundamental forces?

The four fundamental forces are gravity, the electromagnetic force, and the weak and strong nuclear forces. Any other force you can think of (magnetism, nuclear decay, friction, adhesion, etc.) is caused by one of these four fundamental forces or by a combination of them. Electromagnetism and the weak nuclear force have been shown to be two aspects of a single electroweak force.

What is gravity?

Gravity is the force that causes objects on Earth to fall down and stars and planets to attract each other. Isaac Newton quantified the gravitational force: F = mass1 * mass2 / distance². Gravity is a very weak force when compared with the other fundamental forces. The electrical repulsion between two electrons, for example, is some 10^40 times stronger than their gravitational attraction. Nevertheless, gravity is the dominant force on the large scales of interest in astronomy. Einstein describes gravitation not as a force, but as a consequence of the curvature of spacetime. This means that gravity can be explained in terms of geometry, rather than as interacting forces. The General Relativity model of gravitation is largely compatible with Newton, except that it accounts for certain phenomena such as the bending of light rays correctly, and is therefore more accurate than Newton's formula. According to General Relativity, matter tells space how to curve, while the curvature of space tells matter how to move. The carrier particle of the gravitational force is the graviton.

What is electromagnetism?

Electromagnetism is the force that causes like-charged particles to repel and oppositely-charged particles to attract each other. The carrier particle of the electromagnetic force is the photon. Photons of different energies span the electromagnetic spectrum of x rays, visible light, radio waves, and so forth. Residual electromagnetic force allows atoms to bond and form molecules.

What is the strong nuclear force?

The strong force acts between quarks to form hadrons. The nucleus of an atom is hold together on account of residual strong force, i.e. by quarks of neighbouring neutrons and protons interacting with each other. Quarks have an electromagnetic charge and another property that is called colour charge, they come in three different colour charges. The carrier particles of the strong nuclear force are called gluons. In contrast to photons, gluons have a colour charge, while composite particles like hadrons have no colour charge.

What is the weak nuclear force?

Weak interactions are responsible for the decay of massive quarks and leptons into lighter quarks and leptons. It is the primary reason why matter is mainly composed of the stable lighter particles, namely up/down quarks and electrons. Radioactivity is due to the weak nuclear force. The carrier particles of the weak force are the W+, W-, and the Z bosons.

How are carrier particles different from other particles?

The photon, gluon, and the graviton carrier particles are thought to be massless and having no electrical charge. Only the W and Z particles, mediators of the weak nuclear force, are massive, and the W+ and W- particles carry charge. Force carrier particles can only be absorbed or produced by a matter particle which is affected by that particular force. These particles allow us to explain interactions between matter.

How old is the universe?

Today's most widely accepted cosmology, the Big Bang theory, states that the universe is limited in space and time. The current estimate for the age of the universe is 13.7 billion years. This figure was computed from the cosmic microwave background (CMB) radiation data that the Wilkinson Microwave Anisotropy Probe (WMAP) captured in 2002.

What came before the Big Bang?

The Big Bang model is singular at the time of the Big Bang. This means that one cannot even define time, since spacetime is singular. In some models like the oscillating universe, suggested by Stephen Hawking, the expanding universe is just one of many phases of expansion and contraction. Other models postulate that our own universe is just one bubble in a spacetime foam containing a multitude of universes. The "multiverse" model of Linde proposes that multiple universes recursively spawn each other, like in a growing fractal. However, until now there is no observational data confirming either theory. It is indeed questionable, whether we will ever be able to gain empirical evidence speaking in favor these theories, because nothing outside our own universe can be observed directly. Hence, the question can currently not be answered by science.








How big is the universe?

The universe is constantly expanding in all directions, therefore its size cannot be stated. Scientists think it contains approximately 100 billion galaxies with each galaxy containing between 100 and 200 billion star systems. Our own galaxy, the Milky Way, is average when compared with other galaxies. It is a disk-shaped spiral galaxy of about 100,000 light-years in diameter.

What is the universe expanding into?

This question is based on the popular misconception that the universe is some curved object embedded into a higher dimensional space, and that the universe is expanding into this space. There is nothing whatsoever that we have measured or can measure that will show us anything about this larger space. Everything that we measure is within the universe, and so we see neither edge nor boundary nor centre of expansion. Thus the universe is not expanding into anything that we can see or measure.

Why is the sky dark at night?

If the universe were infinitely old, and infinite in extent, and stars could shine forever, then every direction you looked would eventually end on the surface of a star, and the whole sky would be as bright as the surface of the Sun. This is known as Olbers's paradox, named after Heinrich Wilhelm Olbers [1757-1840] who wrote about it in 1823-1826. Absorption by interstellar dust does not circumvent this paradox, since dust reradiates whatever radiation it absorbs within a few minutes, which is much less than the age of the universe. However, the universe is not infinitely old, and the expansion of the universe reduces the accumulated energy radiated by distant stars. Either one of these effects acting alone would solve Olbers's paradox, but they both act at once.

If the universe is only 13.7 billion years old, how can we see objects that are 30 billion light-years away?

This question is essentially answered by Special Relativity. When talking about the distance of a moving object, we mean the spatial separation now, with the positions of us and the object specified at the current time. In an expanding universe, this distance is now larger than the speed of light times the light travel time due to the increase of separations between objects, as the universe expands. It does not mean that any object in the universe travels faster than light.

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