BBC Horizon (2011) - What is Reality?

[Fresco]

Interesting BBC show on physics and reality

http://www.youtube.com/watch?v=o4Z8CqAiYI8

[Lexy]

ooOOOOoooo a whole hour, I will watch it later, thanks!

[Fresco]

At approx. 29:00 the guy talks of infinite parallel universes, but I think he's basically talking about the different dimensions, only he gives it a different label

[grzazek]

.

[Jarrod]

Actually in theoretical physics the terms "universe" and "dimension" are completely different.  Dimensions are like the three dimensions of space and the fourth of time and all the others string theory predicts.  All those dimensions are aspects of this one universe we're in, but there are supposed to be infinitely many more completely separate universes.  But I do see a lot of people confuse the terms and use dimension like universe.

[Monk]

How can there be a plural to it if it is already supposed to encompass the entirety of it?

[skiax]

  I believe one word in current usage is "multiverse" which attempts to describe a non-monolithic version of reality.

[Stillwater]

How can there be a plural to it if it is already supposed to encompass the entirety of it?

Many people take "universe" to mean the whole of the physical, material (matter and energy) entity of which our planet is a part, and which is contiguous across a spatial plane.

It is believed that there are possibile other "universes" like our own, that are separated by some uncrossable barrier. This may be because they are separtated on other timelines which can never cross or interact, or are places where opposite possibilities in seemingly random quantum events are played out alternatively. They may also be places which exist in entirely separate spatial volumes, which are governed by entirely different physical laws or constants than our universe.

So some people take "multiverse" to denote the whole of this collection of separte universes, which never interact or affect one another, but nonetheless all exist.

If this seems strange, I guess you can also consider the example of the word "atom", which was meant to denote the smallest indivisible unit of matter. When subatomic particles were found that comprised these, atoms still retained their name, even if it was apparently no longer literally true. It might be the same with "universe"; we may have used the word once to denote the entirety of existence, and meant by this a certain physical entity which seemed to comprise the totality of all things; if this should prove to be inaccurate, the physical universe might still retain this name.

[Monk]

Distorting the language to describe something that is currently not observable in this configuration within the whole is just absurd in my opinion.

[Stillwater]

Well it is theoretical at the moment. They are devoloping terminology to describe what must be the case if certian guesses or suppositions are true, and they need language to describe that. The distinction between the terms "universe" and "multiverse" expresses the separation of the models of reality each of them describes. Introducing a new term emphasizes the idea that it is a new way of looking at existence, while retaining the older term allows it to have part of its old meaning.

[Monk]

But how can you look at existence in a different perspective with only a mere abstraction? Or is this just the slow, grinding cog of scientific inquiry that's catching up?

[radman32]

Abstraction is the only tool the human mind can use to grasp new understanding, that maybe existence is governed by different laws in different universes; in that the constituents of a universe devise the laws it abides by (or what ever other theory supports).

[personalreality]

At approx. 29:00 the guy talks of infinite parallel universes, but I think he's basically talking about the different dimensions, only he gives it a different label

No he's not.  There aren't any physics theories that use infinite dimensions.  String Theory uses 10 dimensions (9 physical, 1 time), that's the largest number of dimensions in a working theory.

There are multiple different parallel universe theories.  He could be talking about any number of them. 

[Fresco]

No he's not.  There aren't any physics theories that use infinite dimensions.  String Theory uses 10 dimensions (9 physical, 1 time), that's the largest number of dimensions in a working theory.

There are multiple different parallel universe theories.  He could be talking about any number of them. 

Or he could be talking about different astral planes.  You dont know either or for sure, PR

[Jarrod]

I thought M theory has 11 dimensions.

[catmeow]

I thought M theory has 11 dimensions.

That's correct. M theory is a general case of which each of the 5 "string theories" is a specialisation. M theory has 11 dimensions (including time) whereas each of the string theories has 10 dimensions (including time). Each string theory is a special case of M theory in which one of the dimensions cancels out leaving only 10.  Ed Witten dreamt it up

There are multiple different parallel universe theories.  He could be talking about any number of them. 

There are many different possible multiverses. Brian Greene lists and explains them in "The Hidden Reality". They are all mathematical possibilities.  Curiously, in our scientific framework "possibility" equates to "reality", since if it is "possible" then given an infinite space/time, at some point it will actually happen:

http://www.amazon.co.uk/Hidden-Reality-Parallel-Universes-Cosmos/dp/0713999780/

The Hidden Reality reveals how major developments in different branches of fundamental theoretical physics—relativistic, quantum, cosmological, unified, computational — have all led us to consider one or another variety of parallel universe. In some, they are separated from us by enormous stretches of space or time, in others they're hovering millimetres away, in others still the very notion of their location proves to be a concept beyond our reach. Most extraordinarily, Greene shows how all of these parallel universe proposals emerge unbidden from the mathematics of theories developed to explain conventional data and observations of the cosmos.