twistor59 wrote:

surreptitious57 wrote:

crank wrote:

surreptitious57 wrote:
He appears
to be saying that the Universe is flat which was a bit of
a surprise for I thought it was curved due to space time but
a fascinating talk nevertheless

Im sure someone else can explain this better but why not ? These are two different curvatures Krauss is talking about what is the overall basic structure of the universe as a whole, the other curvature you hear of associated with general relativity and gravity is a measure of how the local space time geometry is bent or curved due to local mass / energy density the bending determines, or gives rise to, the local gravity force

I was under the impression that the
entire Universe was curved due to space
time so thanks for emphasising the distinction

I havent listened to the video yet, but the overall structure of the observable universe, as Crank says looks as near as dammit to flat Thats looked at on a huge scale. Like a huge tarpaulin stretched over a football pitch Locally, however, there are clumps of matter and they cause wrinkles in the flatness like wrinkles in the tarpaulin These wrinkles represent gravity due to galaxies and shit The question is - is the whole tarpaulin really flat or does it have some slight curvature - so when you looked at it on a ( hypothetical ) divine scale, would it look like a sphere or would it look like a saddle

Only it were possible to look outside the Universe

surreptitious57 wrote:

twistor59 wrote:

surreptitious57 wrote:

crank wrote:

Im sure someone else can explain this better but why not ? These are two different curvatures Krauss is talking about what is the overall basic structure of the universe as a whole, the other curvature you hear of associated with general relativity and gravity is a measure of how the local space time geometry is bent or curved due to local mass / energy density the bending determines, or gives rise to, the local gravity force

I was under the impression that the
entire Universe was curved due to space
time so thanks for emphasising the distinction

I havent listened to the video yet, but the overall structure of the observable universe, as Crank says looks as near as dammit to flat Thats looked at on a huge scale. Like a huge tarpaulin stretched over a football pitch Locally, however, there are clumps of matter and they cause wrinkles in the flatness like wrinkles in the tarpaulin These wrinkles represent gravity due to galaxies and shit The question is - is the whole tarpaulin really flat or does it have some slight curvature - so when you looked at it on a ( hypothetical ) divine scale, would it look like a sphere or would it look like a saddle

If only it were possible to look outside the Universe

That would be like trying to pee with a hard on.

surreptitious57 wrote:Our tiny mammalian brains are not hardwired to comprehend
the paradoxes of the cosmos unfortunately.

But that doesn't preclude us from comprehending it indirectly via the scientific method. For instance, I think physicists are far too modest when they say things like "no-one understands quantum mechanics". Maybe not fundamentally, but it's the most successful and accurate theory ever. They understand it enough to use the information to make our lives far better than previously, and their comprehension will continually improve.

twistor59 wrote:That would be like trying to pee with a hard on.

Ah, that's actually possible.

surreptitious57 wrote:

twistor59 wrote:

surreptitious57 wrote:

crank wrote:

Im sure someone else can explain this better but why not ? These are two different curvatures Krauss is talking about what is the overall basic structure of the universe as a whole, the other curvature you hear of associated with general relativity and gravity is a measure of how the local space time geometry is bent or curved due to local mass / energy density the bending determines, or gives rise to, the local gravity force

I was under the impression that the
entire Universe was curved due to space
time so thanks for emphasising the distinction

I havent listened to the video yet, but the overall structure of the observable universe, as Crank says looks as near as dammit to flat Thats looked at on a huge scale. Like a huge tarpaulin stretched over a football pitch Locally, however, there are clumps of matter and they cause wrinkles in the flatness like wrinkles in the tarpaulin These wrinkles represent gravity due to galaxies and shit The question is - is the whole tarpaulin really flat or does it have some slight curvature - so when you looked at it on a ( hypothetical ) divine scale, would it look like a sphere or would it look like a saddle

Only it were possible to look outside the Universe

Try to get real close to a fundie and look'em in the eye.

I haven't watched the video either, but here I am trotting out my little bit of knowledge.

It is not inevitable that space would have turned out to be flat, and there are cosmological theories (including Einstein's original one) which postulate positive or negative curvature.

The curvature of space on a cosmological scale is related to the density of matter and "dark energy" (whatever that is) at the time under consideration, and there is a critical density which causes both the cosmological constant Λ and the curvature parameter k to be zero. The more the actual density is different from the critical density, the more - among other things - space will be curved.

Observations suggest that the ratio Ω of the actual density to the critical density is about 1.02 with an uncertainty of plus/minus 0.02, suggesting that the actual density is extremely close to the critical density. This is a bit of a puzzle, because there doesn't seem to be any obvious a priori reason why the matter and dark energy in the universe should occupy the available space with exactly that critical density, and because any difference between the actual and critical density must (according to the various models currently in circulation) increase over time, suggesting that any difference today used to be even smaller in the past.

And this is one of the reasons why inflation in the very early universe is a very welcome deus ex machina, because it would have tended to smooth out the curvature of space (and - because of the way the Friedman equation works - the density). The implication is that the observable universe is as flat as makes no difference, but that this observable universe is only a tiny part of the actual universe. Another mind-boggling thought in a subject that boggles minds on a routine basis.

Amazon just shipped the book.

Lawrence Krauss
bloggingheads
http://bloggingheads.tv/videos/8727?in=27%3A26&out=32%3A21

Lawrence's new book, "A Universe from Nothing" 6:02
The spontaneous generation of the multiverse 4:47
Bob: But where do scientific laws come from? 7:04
Is reality fathomable? 7:18
What use is theology, anyway? 4:35
What Lawrence wants readers to take from his book 4:09

EDIT:
Wright has some fascinating ideas,wrong, but he's interesting, I saw him on Charlie Rose, the 09 appearance on his book The Evolution of god, if interested, see http://www.charlierose.com/guest/view/3129