Post by unkleE on Mar 16, 2011 8:19:22 GMT
Here is an interesting talk on cosmology by physicist Lawrence Krauss. For those averse to these things, it includes some gratuitous anti-religion comments, but overall he is an engaging speaker and I thought his graphics were excellent. The hour is well spent if you enjoy cosmology.
About midway through the talk (I think it was about 32 minutes) he makes an interesting statement. He has been explaining that scientists now believe the universe is flat, which means (1) it's expansion will gradually slow down until it is zero at time infinity, but it will never collapse back on itself, and (2) that the positive energy and negative energy (gravity) are equal, and therefore the universe has a net energy of zero.
Then he makes the statement that this means the universe can be created out of nothing, scientifically, because conservation of energy is maintained (something that wouldn't happen, he says, if the universe was positively or negatively curved). He then adds, perhaps as a qualification, that the universe could have begun as a quantum fluctuation.
Now my reading indicates that a quantum fluctuation occurs in a quantum vacuum, and that a quantum vacuum is certainly not "nothing" - it contains energy in space and time (see e.g. Wikipedia on quantum fluctuation and vacuum state).
Thus it seems to me that Krauss contradicted himself - the universe arises from nothing but it arises from something. Martin Rees certainly thinks we have to be careful talking about nothing: "Cosmologists sometimes claim that the universe can arise 'from nothing' - but they should watch their language, especially when addressing philosophers. We've realised ever since Einstein that empty space can have a structure such that it can be warped and distorted. Even if shrunk to a 'point', it is latent with particles and forces - still a far richer construct that the philosophers' nothing."
It did seem that Krauss enjoyed being mischievous, and was playing up to his audience a bit (as any gifted speaker will), so I don't know how serious he was with this comment.
Does anyone else know if Krauss opposes the established consensus on a quantum vacuum being "nothing"?
About midway through the talk (I think it was about 32 minutes) he makes an interesting statement. He has been explaining that scientists now believe the universe is flat, which means (1) it's expansion will gradually slow down until it is zero at time infinity, but it will never collapse back on itself, and (2) that the positive energy and negative energy (gravity) are equal, and therefore the universe has a net energy of zero.
Then he makes the statement that this means the universe can be created out of nothing, scientifically, because conservation of energy is maintained (something that wouldn't happen, he says, if the universe was positively or negatively curved). He then adds, perhaps as a qualification, that the universe could have begun as a quantum fluctuation.
Now my reading indicates that a quantum fluctuation occurs in a quantum vacuum, and that a quantum vacuum is certainly not "nothing" - it contains energy in space and time (see e.g. Wikipedia on quantum fluctuation and vacuum state).
Thus it seems to me that Krauss contradicted himself - the universe arises from nothing but it arises from something. Martin Rees certainly thinks we have to be careful talking about nothing: "Cosmologists sometimes claim that the universe can arise 'from nothing' - but they should watch their language, especially when addressing philosophers. We've realised ever since Einstein that empty space can have a structure such that it can be warped and distorted. Even if shrunk to a 'point', it is latent with particles and forces - still a far richer construct that the philosophers' nothing."
It did seem that Krauss enjoyed being mischievous, and was playing up to his audience a bit (as any gifted speaker will), so I don't know how serious he was with this comment.
Does anyone else know if Krauss opposes the established consensus on a quantum vacuum being "nothing"?
