Quantum Embafflement.

[Audley Strange]

I'm looking for someone to put me right on this if I'm wrong and to clear up something. If spacetime is a by-product of the big bang, how could there have been an ignition since there was no time in which to proceed from one state to the next? did time exist prior to space?

AND!!!

If the ignition condition (as I'm led to believe) was a quantum process, then all that follows is still part of that process. If this is the case then any observations we make alter the process, and if we can, as we do, observe spacetime events retroactively, i.e. we are peering into the past, are we not then altering the past? So, if we can observe the start conditions, have we in essence altered the big bang in order that we can observe the big bang?

Does that make any sense at all ?

[Xamonas Chegwé]

You can understand QM or know how to control your bladder - but never both - Heisenberg proved this with his Incontinence Theory (and promptly pissed himself.)

The trouble is, the mathematics of QM and General Relativity breaks down at the Big Bang. Neither system is able to adequately describe what happens at such a high density and tiny volume. That is why physicists are tripping over each other to develop a fully functional theory of quantum gravity. String theory claims to have solved some of the problems - but the maths is so hugely complex that nobody can say for sure!

All you can really say about the Big Bang is that things were fucking weird back then!

[Mr P]

Short answer: We don't know yet.

The big bang is a prediction of Einsteins general realtivity which breaks down completely once we get to a timescale of 1x10-44 seconds[1] after the initiation of the big bang. Prior to this time quantum uncertainty would render any measurement meaningless and general relativity only predicts infinities with regards to energy content of the universe.

This is where the search for a quantum theory of gravity comes into play, the main contenders being string theory, quantum loop gravity and conformal cyclic cosmology. As for as anyone knows at the moment it could be any of these, none or some mix of each, you pays yer mony and takes yer choice.


[1] Planck time.

[Mr P]

You can understand QM or know how to control your bladder - but never both - Heisenberg proved this with his Incontinence Theory (and promptly pissed himself.)

The trouble is, the mathematics of QM and General Relativity breaks down at the Big Bang. Neither system is able to adequately describe what happens at such a high density and tiny volume. That is why physicists are tripping over each other to develop a fully functional theory of quantum gravity. String theory claims to have solved some of the problems - but the maths is so hugely complex that nobody can say for sure!

All you can really say about the Big Bang is that things were fucking weird back then!

So yeah... wot he said.

[Audley Strange]

Heh I read your last line as "you pay your monad and take your choice" which made me laugh.

[Audley Strange]

oh and thank you both.

[Clinton Huxley]

Have a look at Sean Carroll's From Eternity To Here. Think he goes into this. Well, I'm only on page 13 so I can't be sure. He may go off on a tangent about ginger biscuits. Hope not.

[Gawdzilla Sama]

It might be that the rules are different when the entire universe was zero millimeters across, you know.

[Xamonas Chegwé]

Everything is made out of Plancks, I think.

[Gawdzilla Sama]

Everything is made out of Plancks, I think.

It's Turings all the way down.

[mistermack]

I really do wish that physicists wouldn't go on TV and say that during the big bang, the Universe came into existence from "nothing".
They don't know that, they don't even know what "nothing" means in that context.

Time with regard to the Universe is a property of the movement of it's parts. And elapsed time is a record of that movement.

When the Universe was "infinitely" small, it seems likely that nothing could move. So time couldn't exist, if movement was impossible. That doesn't mean that nothing existed. It just means that nothing could move.

And it doesn't mean that there weren't other universes, where time WAS happening.

[Santa_Claus]

I created the Unviverse out of Lego. and a lot of serious wanking.

on the 7th Day I invented Buses

FACT.