Thread: cronology protection conjecture

can somebody help me what does actuall cronology protection conjecture mean? i reall could not get it help me guys

Have you read the wikipedia article on the subject? It seems quite good.

The basic notion is that time travel, which is theoretically possible, is prevented at the macroscopic scale by aspects of quantum mechanics.

That's my way of saying I can understand a simplified English explanation, but to properly grasp it you would have to do the maths. I can't, since I'm at heart a dumb Scotsman.

Originally Posted by Ophiolite

I can't, since I'm at heart a dumb Scotsman.

Dumb scotsman? Ahem:
James watt
James Maxwell
Alexander Graham Bell
lord Kelvin
John logie Baird
Robert Brown

Not to mention plenty of others who have contributed massively to physics, astronomy, engineering and a good amount in medicine as well.
For a population of only 5 million thats pretty impressive.

Have some pride in your country man!

Originally Posted by harvestein

Have some pride in your country man!

Obviously you are unaware of the habit of self deprecating irony practised by Scots and some other inhabitants of the British Isles. When I say I am only a dumb Scotsman I actually mean In your wildest dreams you couldn't even hope to be half as smart. This approach is just part of our natural charm and is a useful defense mechanism when we invade England.

England has already been invaded.

I probably should have pointed out that i am also Scottish. I did detect some sarcasm. I am sorry if i have revealed our plot to take over the world. its a pity though, the first part of the plan was successful: Brainwashing the populace with television by drugging them with what they think is an antibiotic. BWAHAHA!

Sorry ill get back to work now....

Originally Posted by saurab dulal

can somebody help me what does actuall cronology protection conjecture mean? i reall could not get it help me guys

There are some solutions of the Einstein field equations of general relativity that admit closed timelike curves, which would permit "time travel". However these arise in somewhat exotic situations and are somewhat suspect from a physical point of view. So, from a theoretical perspective the question is whether or not closed timelike curves represent real physics or are real.

There is some thought that a quantum theory of gravity, which we do not have at the moment, might rule out closed timelike curves.

The chronology protection conjecture is a conjecture by Hawking that there is some principle of physics that would prevent the existence of closed timelike curves in a correct theory.

Three words: Battle of Flodden 8)

I have been reading " A Briefer History Of Time " by Stephen Hawking with Leonard Mlodinow. Page 116 mentions " chronology protection conjecture " He says that " The laws of physics conspire to prevent macroscopic bodies from carrying information into the past. This conjecture has not been proved, but there is reason to believe it is true. The reason is that when space- time is warped enough to make time travel into the past possible, calculations employing quantum theory show that particle/antiparticle pairs moving round and round on closed loops can create densities large enough to give space-time a positive curvature, counteracting the warpage that allows the time travel. Because it is not yet clear whether this is so, the possibil.ity of time travel remains open. But don`t bet on it. " I am still trying to get my head around quite a few things in the book, but it makes for good reading.