[acecharly (OP)]

If we take an elctron orbiting an atom it flys round extremely fast then say the moon orbiting the earth approximately every month earth takes a year to orbit the sun then the solar system takes a, lets say an extremely long time to orbit the galaxy. There are no solar systems ive heard of which orbit the centre of there galaxy at the same speed an electron orbits its atom.

It seems the same for life generally a fly may live 2 weeks. larger a cat/dog maybe 15-18 years a human 70ish years an oak tree maybe 250 years.

Larger seems to have a link to longer...

Any thoghts guys?

Cheers Ace

[David Cooper]

If you try to make something orbit faster, you either rip it out of orbit altogether or you'll increase the size of its orbit and slow it down on average (to move a space craft from a low circular orbit into a high circular orbit you might accelerate it twice with rockets and end up with it orbiting at a slower speed than it started with).

A tree is always young, growing round the circumference of a dead tree inside it - it isn't really the same tree over the hundreds of years that a tree has been there. With people it's similar - almost all the material being replaced repeatedly, though some cells are said to last the whole distance, which leads me to wonder if all the genetic material inside them gets replaced from time to time without cell division taking place. If not, then that would suggest that quite a lot of the material in your brain doesn't get replaced during your lifetime.

[LetoII]

bigger = slower because of mass i guess, and that's a subject you can go on and on about.
As for life spans of living creatures dont neglect the change in life spans within one species. Humans are a nice example.
For this reason i often chuckle inside when i think about the lenght space travel would take and how species evolve, we wouldnt be what we call humans very soon yet confronting this fact seems a diturbing thought to most people. We even dream of self preservation, what a foolish ambition to begin with.

[Don_1]

It seems the same for life generally a fly may live 2 weeks. larger a cat/dog maybe 15-18 years a human 70ish years an oak tree maybe 250 years.

Larger seems to have a link to longer...

And here's a fly for your ointment.

The Testudo Graeca Graeca (Mediterranean Spur Thigh Tortoise) will be around the size of a dinner plate when fully grown. Timothy, a mascot of several Royal Navy ships, including HMS Queen during the first bombardment of Sevastopol in the Crimean War (she was the last survivor of this war), died in 2004. She was at least 160 years old and may have been up to 175. Harriet, the Galapagos Giant tortoise brought to London by Charles Darwin, and the largest species, died in 2006 at around 175 years of age, while Tu'i Malila, an Aldabra (second largest) died in 1965 at the age of 188 and another Aldabra named Adwaita died in 2006 at the grand old age of 255. He holds (albeit posthumously) the record for the longest lived vertebrate.

So even in the entire order of the Testudines, size does not necessarily determine longevity.

[Guthers]

Not forgetting that some birds (parrots?) can live to 100 years or more. Also I seem to remember hearing lobsters can survive well into retirement age.

On a couple of other points above, I don't think brain cells ever get replaced. Once these cells die they are gone for ever. Stories of people who sustain brain injuries gradually recovering lost abilities are due to other undamaged parts of the brain adapting to perform new functions.

And then the question of whether future long distance astronauts (taikonauts?) would still be human, well are you looking for a definition of "human" which depends on the mental or the physical? The body is just a machine after all, and being human encompasses a very wide range of body shapes already. Even if our travellers evolve an extra arm or a second heart, they'd still be our descendants. If their brains evolve abilities which meant they look on us much as we would think of our smaller primate or even fishy ancestors then that might be a difficult question to answer. In the end, if we eventually meet aliens with whom we (they?) can communicate and are on the same wavelength, who cares what we would actually call ourselves?

[yor_on]

No, you can grow new cells by studying a subject craving a lot of thought. It's experimentally proven although it's about specific parts of the brain as I remember it. It may be that there are areas that won't be able to do this, but it's not true of the whole brain.

[RD]

No, you can grow new cells by studying a subject craving a lot of thought. It's experimentally proven although it's about specific parts of the brain as I remember it. It may be that there are areas that won't be able to do this, but it's not true of the whole brain.

e.g. cabbies hippocampi ... http://news.bbc.co.uk/1/hi/677048.stm

The evidence for neurogenesis is mainly restricted to the hippocampus and olfactory bulb, but current research has revealed that other parts of the brain, including the cerebellum, may be involved as well.

http://en.wikipedia.org/wiki/Neuroplasticity#Treatment_of_brain_damage