The missing edge

[Fred56]

There is no 3-dimensional edge to spacetime. There is an "edge" to its expansion, which is the "arrow" of entropy.

[ydoaPs]

There is no 3-dimensional edge to spacetime.

Prove it.

There is an "edge" to its expansion,

prove it

 

which is the "arrow" of entropy.

The entropy of a system can be lowered.

[foodchain]

There is no 3-dimensional edge to spacetime. There is an "edge" to its expansion, which is the "arrow" of entropy.

 

What I don’t get is if spacetime or the universe is one solid body I get this image in my mind. If you take a piece of paper, crumple it so you have some texture, moving such at any part causes moment to the rest. So my idea is if that the universe is fully connected at some or any points, any activity in such then should have related activity via its connection to all parts it touches, sort of like a butterfly effect. I don’t know if at all this can be explained at a QM level as I have no formal education in physics, just an interest and an over the top at times imagination.

 

Then with the concept of time as I think you may or may not be getting at? I just don’t know how time can be fully separated from say matter/energy or the relationship the two have, which again for some reason I get tossed back wondering at QM origins. I don’t really understand classical systems to much and to be honest. I mean from reading on string theory if everything is a representation of a more primitive or underlying particle or object, what is or why is the differentiation present from a particle level to a classical system, more or less with the idea that the universe is a quantum system, and of course lastly how does chaos theory role up in all of it.

[Fred56]

Here's what a certain wheelchair-bound mathematician has to say:

 

“Despite ... difficulties with the idea of a static and unchanging universe, no-one in the seventeenth, eighteenth, nineteenth, or early twentieth century suggested that the universe might be evolving with time. Newton and Einstein both missed the chance of predicting that the universe should be either contracting or expanding. One cannot really hold it against Newton, ...but Einstein should have known better. The theory... that he formulated... predicted that the universe was expanding.”

Stephen Hawking, Black Holes and Baby Universes

 

You have to step beyond Newton's ideas to accept the expansion. Anyone who has difficulty with this concept isn't alone, Einstein couldn't accept it either.

[Spyman]

You have to step beyond Newton's ideas to accept the expansion. Anyone who has difficulty with this concept isn't alone, Einstein couldn't accept it either.

AFAIK: Einstein did accept the expansion:

In physical cosmology, the cosmological constant was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. Einstein abandoned the concept after the observation of the Hubble redshift indicated that the universe might not be stationary. However, the discovery of cosmic acceleration in the 1990s has renewed interest in a cosmological constant.

http://en.wikipedia.org/wiki/Cosmological_constant

[Fred56]

“Putting a disconnected world together by explaining it in terms of effects and causes may be as natural to us as breathing. If the world does not provide coherent information, the mind is apt to impose its own coherence on the world, with an abundance of explanations.” -Jeremy Campbell, The Improbable Machine

 

Spyman: why do you think he initially used such a small value (for his constant)?

[Spyman]

Spyman: why do you think he initially used such a small value (for his constant)?

He wanted to achieve a stationary universe and the equation in itself is 'unstable'.

 

If the universe expands slightly, then the expansion releases vacuum energy, which causes yet more expansion. Likewise, a universe which contracts slightly will continue contracting.

 

It's all in the link I provided...

 

 

But when Edwin Hubble showed that the universe appeared to be expanding, Einstein removed the cosmological constant and called it the "biggest blunder" of his life.

[Fred56]

Right, we know all that.

 

Hawking is saying that he "fudged" his theory. Which is different to explaining the problem with it. He didn't really change his mind until Hubble's observation. So he did "miss the opportunity" to predict it (expansion). Fixing up a theory after the fact to bring it into line with empirical observation isn't quite the same thing.

 

He wanted to achieve a stationary universe

Remember?

[Royston]

Right, we know all that.

 

Hawking is saying that he "fudged" his theory. Which is different to explaining the problem with it. He didn't really change his mind until Hubble's observation. So he did "miss the opportunity" to predict it (expansion). Fixing up a theory after the fact to bring it into line with empirical observation isn't quite the same thing.

 

Ummm, I don't understand where this is going, or what this particular issue (above) has to do with your original statement...in your OP.

[Fred56]

OK, the expansion might not be "due" to entropy. That's a bit of a leap right there. But saying time is a vector on the surface (of entropy/expansion) is ok, no?

(I say entropy is on the "surface" of the expansion, above)

The expansion and the fact the universe may have no (Euclidean) boundary are related. This is my conjecture.

[Spyman]

Fixing up a theory after the fact to bring it into line with empirical observation isn't quite the same thing.

Fixing a theory to match observation is to accept the observation.

 

You did say:

Einstein couldn't accept it either.

 

And I said:

Einstein did accept the expansion

 

Remember ?

[Fred56]

Right. But you're splitting hairs.

I'm saying he didn't (initially) you're saying he did (eventually) you ning.

[Spyman]

So you should have said "Einstein didn't accept it initially either".

 

OK, so I am nitpicking, but you could have admitted that you where wrong and corrected/explained yourself directly, instead of making a 'verbose' argument about it. And - "ning" on yourself...

[Fred56]

“the total number of people who understand relativistic time ...is still much smaller than the number ...who believe in horoscopes.” -Yuval Ne'eman

 

1) Maybe someone would like to try and show that there is a dimensional edge, a "boundary", to the universe?

2) Or try to prove that there is no expansion (so no "edge of expansion")?

3) The entropy of the universe cannot decrease.

[foodchain]

1) Maybe someone would like to try and show that there is a dimensional edge, a "boundary", to the universe?

2) Or try to prove that there is no expansion (so no "edge of expansion")?

3) The entropy of the universe cannot decrease.

 

1) A boundary to what, what encapsulates the universe, the size of its own existence? Dark matter/energy? I have no idea either...

2)I think expansion has already been proven right?

3)Decrease into what? Does it devolve:eek: Does is go into that nothing at the boundary, or is it stuck in what is the current universe occupying empty space that has no mass or matter or what not in it. I asked a question about what happens to photons emitted towards nothing, such as the boundary, or what happens to a photon that never touches anything. I just wonder if they live forever is all.

[Fred56]

Saying "it can't decrease" means "it can only increase", it isn't "going" anywhere.

 

saying time is a vector on the surface (of entropy/expansion) is ok, no?

Since no one's pulled me up on this, I'll ride it a bit further. The "vector" of time (times arrow) is obviously not a real quantity, but belongs in the imaginary realm.

Is it still logically consistent to say the vector is measurable? How should it be modelled? Or do we only have a single point to consider (at a time, har har)?

[Fred56]

P.S. I vote this goes into the relativity thread.