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Wednesday, October 19, 2005

Is time travel possible?

It's nerve wracking enough going to live in a foreign country without knowing what it's like. I don't understand why anyone would want to live in the future. How awful must it be to be homesick for a world that no longer exists.

However is time travel theoretically possible?

It's a question that has been seriously considered outside the realms of science fiction. This BBC article discusses one of the paradoxes of time travel. A new model using the laws of quantum physics (I don't even know what that is) suggests that it is possible to go back in time but that we can only observe events, we can't alter them. The fact of the present being the way it is means that anything you do in the past can only lead to the present state of affairs.

Michio Kaku describes the physics behind time travel here. I've never been able to get my head round the fact that time can speed up and slow down. If time were a thing like soup I could imagine it changing in consistency, but isn't time an abstract, an idea? How can it change? I really wish someone would explain that one to me. (Ah, this sort of helps.)
Einstein gave us a much more radical picture. According to Einstein, time was
more like a river, which meandered around stars and galaxies, speeding up and
slowing down as it passed around massive bodies. One second on the earth was Not
one second on Mars. Clocks scattered throughout the universe beat to their own
distant drummer.
Kaku outlines two issues that get in the way of time travel.
  1. A huge amount energy is required. 'One either has to harness the power of a star, or to find something called “exotic” matter (which falls up, rather than down) or find a source of negative energy.'
  2. In principle a worm hole can be used to connect two regions of time but there is no way of knowing if it would be stable.
Stephen Hawkings thinks that time travel may be possible but that there are huge obstacles. He discusses these issues further in this lecture. It made my head hurt reading it but it's worth a look.


Blogger GreenSmile said...

Glad that "science and politics" [bora] pointed me here. I was looking for an informed second opinion on Amos Ori's work. Here is a post I could not get slashdot to look at:
News@nature.com gives a readable description of physicist Amos Ori's article in Physical Review Letters on a better way to build a time machine. Expert Paul Davies rates it as more feasible than ideas that require the manipulation of black holes. Researchers are divided over whether any solution to the fundamental problem of a time machine, regardless of design, blowing up due to quantum mechanical instabilites will ever be found. Says Ori: "Perhaps we shall have to await the formulation of the full theory of quantum gravity before we know whether quantum instabilities provide chronology protection or not".

3:06 am  
Blogger Mapo said...

Thanks Greensmile. :)

10:04 pm  

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