What is gravity?

[renormalised (Carl)]

Originally Posted by Nesti

Hmmmm, have you been doing some reading or something? LOL

No. I haven't read your book yet. Just my own thoughts and what I understand of the various theories.

[Nesti (Mark)]

Originally Posted by renormalised

Just my own thoughts and what I understand of the various theories.

Can't say you'll agree with it, but coming from the angles you do, you're sooooo gonna see it.

[renormalised (Carl)]

Originally Posted by Nesti

Can't say you'll agree with it, but coming from the angles you do, you're sooooo gonna see it.

Should be a good read, then

[shane.mcneil]

Originally Posted by renormalised

Maybe, Alex. If the universe is indeed fractal, then all things being relative, the higher space from which it unfolded should also be fractal in nature. As you move to smaller and smaller scales in either state, being able to resolve the fine structure of spacetime would become harder and harder (from the perspective of your location within spacetime) until it appeared to become random and chaotic. It would be there that the transition between spaces occurred. Where the spacetime we live in "froze" out of the higher space from whence it sprang. The freezing out of the universe from that higher space would be, in effect, the Big Bang. Whilst universes may come and go in the higher space much like virtual particles out of the quantum froth, when they reach a threshold level of energy, the "universe bubble" "detaches" itself from that higher space by lowering its "degrees of freedom" (if you think of physical dimensions as degrees of freedom of existence or mathematical movement) and expands "outside" that higher spacetime.

Forgive me if I am sounding really dumb here. I am trying to follow the concepts. Is what you are describing here a form of the big bounce universe as opposed to the big bang? Where our universe is expanding from a singularity "interface" from a previously collapsing universe?

Shane

[renormalised (Carl)]

Originally Posted by shane.mcneil

Forgive me if I am sounding really dumb here. I am trying to follow the concepts. Is what you are describing here a form of the big bounce universe as opposed to the big bang? Where our universe is expanding from a singularity "interface" from a previously collapsing universe?

Shane

No, that's another topic altogether. What I was saying there is (amongst other things in previous posts) that the universe we live in "unfolded" from a higher dimensional state...if you follow SUSY (supersymmetry) and String Theory, it's an 11 dimensional "superspace" (a "space of all spaces").

Though, if you follow M-Theory, this superspace contains multidimensional spacetime membranes which float about and periodically collide with one another. It's this collision which generates the Big Bang event within the brane.

When you talk about a big bounce universe, there is no singularity present. The previous universe basically collapses into an indeterminate state where most of the information about that universe is lost. It then re-expands into a new universe with new constants and fundamental values of state. Even with a "normal" big bang universe, there is no singularity. To have a singularity, you have to have zero size and infinite density. Before it even got to that, quantum fluctuations would prevent it from forming. A singularity, by definition, would be an absolute location and frame of reference, simply because of it's dimensional state. That's why Relativity breaks down at that scale, it's equations simply become nonsensical. It's also why QM would prevent it from forming...because it can't become infinitely dense and zero in size as that would violate the Pauli Exclusion Principle, for a start. What would happen is once the universe approached the Planck Scale time/size limit, random quantum fluctuations would smear its existence out into an indeterminate state of probabilities. It would essentially return to the higher dimensional state out of which it first formed. Or just before it went completely back to that condition, a spike in the quantum field would cause another bubble to form and expand into a new universe (the bounce scenario).

[Enchilada]

...I'm not supposed to respond on this thread, but you guys might like to look at this interesting paper on arxiv article "New Class of Dark Matter Objects and their Detection" by C Sivaram and Kenath Arun. Linked at; http://arxiv.org/pdf/0910.2306 . They seem to claim the dark matter source might be by so-called "Wimponium" which they examine in various scenarios. (First postulated by March-Russell J and West S M, Phys. Lett. B, 676, 133, 2009)

They conclude;

"In this paper we look at a new class of objects formed by the collapse of dark matter particles and elucidated their various physical properties and observable aspects associated with them. We have analysed the effects of the mass of individual dark matter particles on the mass, annihilation rate, mass loss, etc of these dark matter objects. In a certain range of parameters their life times are comparable to the Hubble age and they could be observable as gamma ray point sources (like Hawking black holes, but with distinctly different signatures). We have also explored the possibilities of star formation and black hole formation from accretion onto and mergers of these dark matter objects."

Although your gravity questions here are interesting, this paper is some really good food for thought to the progression of the missing mass and the gravitational effects additional to the theory properly describing general relativity.

IMO, these two paper are significant to the cutting edge searches to dark energy and dark matter.

I'll comment no more.

[shane.mcneil]

Originally Posted by renormalised

Or just before it went completely back to that condition, a spike in the quantum field would cause another bubble to form and expand into a new universe (the bounce scenario).

Thanks for that Carl. Sorry I realised that you weren't talking about a big bounce, I guess what I was asking if you were saying our universe came from a previous one? Because the other question I'm interested in is how did it all start? It seems that understanding that would answer gravity and everything else, obviously.

So is what you are saying here accepted as science fact? Is there ever an ultimate beginning anywhere? If we popped out from something else, what did it pop out of?

Thanks again,

Shane

[sjastro]

Originally Posted by shane.mcneil

Thanks for that Carl. Sorry I realised that you weren't talking about a big bounce, I guess what I was asking if you were saying our universe came from a previous one? Because the other question I'm interested in is how did it all start? It seems that understanding that would answer gravity and everything else, obviously.

So is what you are saying here accepted as science fact? Is there ever an ultimate beginning anywhere? If we popped out from something else, what did it pop out of?

Thanks again,

Shane

Shane,

It's not even science in the strictest definition of the word. A scientific theory needs to be falsifiable or be able to be proven or disproven.
String theory and it's variants are more of a philosophical than a scientific argument.

Supersymmetry is a scientific theory as it can be proven or disproven on the basis of experiment or observation.

Steven

[renormalised (Carl)]

Originally Posted by shane.mcneil

Thanks for that Carl. Sorry I realised that you weren't talking about a big bounce, I guess what I was asking if you were saying our universe came from a previous one? Because the other question I'm interested in is how did it all start? It seems that understanding that would answer gravity and everything else, obviously.

So is what you are saying here accepted as science fact? Is there ever an ultimate beginning anywhere? If we popped out from something else, what did it pop out of?

Thanks again,

Shane

It's one of the ideas they've come up with, but whether it becomes a fact or not depends on what they find in the future. Even the Big Bang isn't really a fact....it's a theory. Whilst much of the evidence they have points toward it being the most likely mechanism for the universe's formation, it's still yet to be confirmed for certain.

[shane.mcneil]

OK, so any discussion of say points B C and D are only correct if our initial starting place A is right. But when it comes to these sorts of subjects, we aren't certain that our initial starting point is correct (not that I'm saying they are wrong either). I guess that's why everyone is looking for the TOE. If there is one. I didn't realise how much science and philosophy can over lap.

Thanks again. Shane.

[sjastro]

Originally Posted by shane.mcneil

OK, so any discussion of say points B C and D are only correct if our initial starting place A is right. But when it comes to these sorts of subjects, we aren't certain that our initial starting point is correct (not that I'm saying they are wrong either). I guess that's why everyone is looking for the TOE. If there is one. I didn't realise how much science and philosophy can over lap.

Thanks again. Shane.

In the context of this thread perhaps one should substitute the word "correct" with the word "complete".

Newtonian physics is an incomplete theory but it is "correct" in terms of what it has been able to explain. GR is a more complete theory than Newtonian physics but it cannot be considered to be any more "correct".

For example for low velocities and low gravitational field strengths, Newtonian physics and GR give the same predictions. That is not an accident since GR is an evolution of Newtonian physics instead of a replacement.

Similarly the various alternatives mentioned in this thread such as string theory and it's offshoots are not meant to be seen as replacements to GR, but to make GR (and QM) structured into a more complete theory.

Regards

Steven