Some question's re time.

[Vraith]

I think I heard Stephen Hawking once describe the world down at the quantum level as 'grainy' - by this I think he meant that at ever smaller and smaller measurements of time, distance whatever, a point is reached where it is no longer *possible* to talk of smaller units - that distance and time have 'quanta' in just the same way as energy does, minimum 'packet sizes' below which you cannot go. Is this a) correct and b) what you are referring to above in the comments on distance V?

It's partly that, peter. And that's connected with what M said on the collapse that happens if smallness is allowed to be infinite.
[that collapse happens regardless of whether one is trying to measure it or not]

But, even on the ordinary scale, I don't think people understand space any more than time [or not much more]. I mean...what is distance MADE of? HOW does it "pass," [or we "cover/cross/measure it?].
And distance is every bit as relative as time.
And...I think this might have come up before...in some ways time is easier. It's not that hard to imagine time going the other direction. Yea, we end up all kerfluffled in paradoxes and stuff when thinking on the effects, but at least we can roughly picture it.
Try that with space, though. You can picture shrinking, sure. But can you picture "reverse distance," or even begin to describe "anti-space?"

[peter]

Anti-time is not the same as time flowing backward is it though V., any more than say anti-distance is the same as going from b to a as opposed to a to b.

[Not wanting to be a nit-picking prick here, but the same thought jumped into my head 3 days after seeing the post for the first time, so it had to be nailed down ]

[Vraith]

Anti-time is not the same as time flowing backward is it though V., any more than say anti-distance is the same as going from b to a as opposed to a to b.

[Not wanting to be a nit-picking prick here, but the same thought jumped into my head 3 days after seeing the post for the first time, so it had to be nailed down ]

Yes, I thought of that distinction after I posted.
And I think it is complicated, again, cuz we disconnect time and space.
Reverse time and anti-time ARE the same, I think...time is always a result of space, anti-/reverse time and normal time both require "positive" space to happen in/with.
But anti-space and reverse [shrinking] space are not the same thing. Space is something that "is," time is something that "happens" because of space [and things in space...matter, energy]
heh...maybe.

[Hashi Lebwohl]

Distance is "directionless" because in and of itself it has no inherent order while vectors have direction because they go from point A to point B. Time is a vector, not a distance--it has an inherent order, which is why it is possible to speak of going "backwards" in time--the cup was sitting on the table before it fell to the floor, etc.

[peter]

I think we've battered the lights out of that one, but while I have your attention can I just raise a question that occured to me during a bout of random thinking the other day. If, say an earth sized planet shot past us like two snooker balls nearly grazing each other.....no this is wrong, start again. Are there points in space where the cumulative gravitational attraction between all the objects at their various distances, result in null points - ie places where an object placed, would stay suspended by virtue of a cumulative zero gravitational pull in any direction.

If every piece of matter in the universe attracts every other piece of matter, surely given time the whole lot will fall back together even in the face of the expanding space between them. [Is this what they mean when they talk about whether the universe has enough 'mass' to start contracting again. If so, why would the expanded space contract back to a reverse big bang as opposed to all the matter just pulling itself into one bloody great lump, but with the space continuing to expand as before ad infinitum.] Silly questions - has to have something to do with the relationship between space and matter; I'm guessing that you can no more have space without matter in it than you could have matter without there being space for it to be in.]

[Hashi Lebwohl]

Correct--matter and the space in between collections of matter are made of the same thing.

The ultimate long-term fate of the universe depends upon which camp of cosmology you are in. Some think that the expansion will slow down and could result in everything coming back together in a Big Crunch. It will get really crowded and loud before we all fall into the accretion disk of the largest black hole ever.
Others hypothesize that eventually galaxies will become so separated and old that star formation ends, the existing stars burn out or collapse into brown dwarves, neutron stars, or black holes, and that after a couple dozen trillion years the universe will reach heat death--everything settles into a thermodynamic state such that very little is happening anywhere. Cold, quiet, and dark.

[Vraith]

The slowing of expansion, and perhaps a reversal to collapse is looking more and more unlikely since the fairly recent observations that show the expansion is actually accelerating...the exact opposite of what everyone thought was/should be happening due to gravity's universal reach.

Someone, don't recall who, said something like
"We have a good equation we use to describe it on the large scale. With this observation, we can either blame one side of the equation and say we don't understand gravity, or blame the other side and say there's all this other stuff." [the other stuff being dark energy].

[peter]

Can I quote Deutsch [again - sorry guy's] on gravity;

Most non-physicists consider it self evident that when you hold your arm out hozontally you can feel the force of gravity pulling it downwards. You cannot. The existance of a force of gravity is ...... denied by Einsteins general theory of relativity.... This says that the only force on your arm in that situation is that which you are exerting, upwards, to keep it constantly accelerating away from the straightest possible path in a curved region of spacetime

Would it be helpfull in the coundrums discussed above if the concept of gravity was abandoned, or at least put back in it's box for a while, in order to bring some clarity to the situation. Are scientists not in a sense caught in a paradox of thier own making if they endevour to understand the universe in terms of a force whose very existance is, at other points in the theory denied.

[Vraith]

Can I quote Deutsch [again - sorry guy's] on gravity;

Most non-physicists consider it self evident that when you hold your arm out hozontally you can feel the force of gravity pulling it downwards. You cannot. The existance of a force of gravity is ...... denied by Einsteins general theory of relativity.... This says that the only force on your arm in that situation is that which you are exerting, upwards, to keep it constantly accelerating away from the straightest possible path in a curved region of spacetime

Would it be helpfull in the coundrums discussed above if the concept of gravity was abandoned, or at least put back in it's box for a while, in order to bring some clarity to the situation. Are scientists not in a sense caught in a paradox of thier own making if they endevour to understand the universe in terms of a force whose very existance is, at other points in the theory denied.

The problem with that is GR says spacetime is curved, we perceive/label the curvature as gravity...but curved BY WHAT? [and that's ignoring the question of how something that has no "material" can be "curved"...or any other shape, for that matter...]
Eliminating it as a force doesn't answer any questions...it just moves them into some other physicists pile.

[I'm Murrin]

Curved by the presence of mass, I assumed?

[Vraith]

Curved by the presence of mass, I assumed?

That's one of the displacements...it doesn't solve the problem, just moves the question.
IF [as the existence of Higgs suggests] mass is something incorporated into things, then there still has to be a mechanism by which mass takes hold of "spacetime" and curves it.
IF the interpretation that mass is equivalent to curved spacetime is accepted, you still don't know what spacetime is made of that it can have a shape...curved or otherwise.

[peter]

Hashi said above that matter and space-time are at their fundamental level the same thing [hence the one not being able to 'exist' without the other]. Since matter has form [that we can see] and space-time we cannot see, so can we not also asume that space-time can also have form - it's just that we also cannot see that. [Badly put, but I think you get the idea].

[Hashi Lebwohl]

Matter is "compressed" spacetime. Matter tells spacetime how to curve and curved spacetime tells matter how to move. That which we experience as "gravity" is really the degree to which spacetime is being curved--the more curved that spacetime is the stronger the gravity becomes.

I don't think we know what spacetime is made of, only that it exists.

[Vraith]

Matter is "compressed" spacetime. Matter tells spacetime how to curve and curved spacetime tells matter how to move. That which we experience as "gravity" is really the degree to which spacetime is being curved--the more curved that spacetime is the stronger the gravity becomes.

I don't think we know what spacetime is made of, only that it exists.

Yea. That's basically why I said we feel like we know more about space than time...but in fundamental ways, we don't.
For many reasons, space has to have all the properties of "nothing." [heh, or a complete lack of properties].
Yet, it must also have SOME physical/material property. In some way it must have inherent duality.
And I'm pretty sure that the Higgs and mass as simply compressed spacetime contradict each other in exactly the same way that Quantum and GR gravity contradict each other. [among other difficulties].

[Vraith]

Don't watch the link at the bottom unless you got a lotta time...and it's a little tedious/boring. But the conclusion is interesting.
It's about the ultimate tiny structure of spacetime, and the quantum/cosmic scale reconciliations.
Some highlights: She talks about the scales physicists talk about/examine...she's personally interested in the Planck scale [10^-35] which is defined as ""the smallest scale you can still get funding for."
When she gets to wormholes and the time problem she says "you can use the Grandfather Paradox, usually I don't because I think it has a lot of unnecessary violence.""
A couple other funny things...like a sample promo video to show your university to get funding for looking at wormholes...

Anyway...I'm gonna have to watch the end again to make sure I get it.
But she says they've [physicists, not just her specific people] built lots of computation models and tools...apparently proven ones that have been shown to work on testable problems...
Her [currently not physically testable] simulations...one of the main purposes being to find consistency/connection between quantum and cosmic... have shown that in Universes where wormholes are allowed, they collapse on themselves, self-connecting and shrinking, and everything in them is "one step away."
Only in models that forbid wormholes do you end up with a universe like ours...not only that expands, but that expands with acceleration.
That's interesting...more interesting still...at that tiniest scale, things are not 4-dimensional, or 4-dimensional with multiple "curled up" dimensions.
Things are basically 2-dimensional, with shapes fractal and interlocking with odd features...like being 1.387 dimensional.

So...maybe that does sound interesting to folk?
Here it is, all hour and 10 minutes of it:
www.youtube.com/watch?v=fv2gBjQ8xIo

[peter]

Don't watch the link at the bottom unless you got a lotta time...and it's a little tedious/boring. But the conclusion is interesting.
It's about the ultimate tiny structure of spacetime, and the quantum/cosmic scale reconciliations.
Some highlights: She talks about the scales physicists talk about/examine...she's personally interested in the Planck scale [10^-35] which is defined as ""the smallest scale you can still get funding for."
When she gets to wormholes and the time problem she says "you can use the Grandfather Paradox, usually I don't because I think it has a lot of unnecessary violence.""
A couple other funny things...like a sample promo video to show your university to get funding for looking at wormholes...

Anyway...I'm gonna have to watch the end again to make sure I get it.
But she says they've [physicists, not just her specific people] built lots of computation models and tools...apparently proven ones that have been shown to work on testable problems...
Her [currently not physically testable] simulations...one of the main purposes being to find consistency/connection between quantum and cosmic... have shown that in Universes where wormholes are allowed, they collapse on themselves, self-connecting and shrinking, and everything in them is "one step away."
Only in models that forbid wormholes do you end up with a universe like ours...not only that expands, but that expands with acceleration.
That's interesting...more interesting still...at that tiniest scale, things are not 4-dimensional, or 4-dimensional with multiple "curled up" dimensions.
Things are basically 2-dimensional, with shapes fractal and interlocking with odd features...like being 1.387 dimensional.

So...maybe that does sound interesting to folk?
Here it is, all hour and 10 minutes of it:
www.youtube.com/watch?v=fv2gBjQ8xIo

Will come back on this V. when I've had time to watch the link, but in the meantime re 'the grandfather paradox', I saw Hawking in one of his popular tv shows, give his explanation of where the paradox breaks down. Alas I don't remember how he pulled it off, but I know he was able to give a convinceing theory as to how the conundrum would most likely be resolved [ I've found it on you tube www.youtube.com/watch?v=sUqxzH0652w ].