for the physicists...

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bluechair84
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for the physicists...

Postby bluechair84 » Mon Oct 01, 2012 20:16 pm

I watched an episode of Horizon recently that blew my mind... It described the size of the universe. In doing so, it defined for me 'the visible universe' which says that we can only see as far as light has had time to travel. If the universe was born 8 Billion years ago, we can only see the distance light has travelled in 8 billion years. They demonstrated this with a view of the universe showing a bubble of what we could see from the oldest light in all directions. Now... if that bubble represents the distance light can travel in the time the universe has existed, how can it be any bigger than that if the speed of light is a universal speed restriction? Surely the edge of the universe couldn't have at one point (or even still presently) been travelling faster than the speed of light for there to be anything further than 8 Billion light years? I would assume maximum radius would be 8 Billion light years, but more likely far less...

And if you can solve that, maybe you can also explain why I'm able to get toothpaste out of a tube my girlfriend gave up on a week ago? Answers to the crudcatcher I think!

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Re: for the physicists...

Postby Chunkers1980 » Mon Oct 01, 2012 20:20 pm

Hawkins explains it on Discovery with a train. But it hurt my head.

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jndb72
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Re: for the physicists...

Postby jndb72 » Tue Oct 02, 2012 08:24 am

Read a few of his (Hawkins) books a while back. Found them very disappointing, mainly because I found him very patronising.
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Re: for the physicists...

Postby kieranb » Tue Oct 02, 2012 09:46 am

well, I think you are coming at it from the wrong angle. when they say the universe is expanding they don't mean that within a vast space things are moving apart like a fragments froma bomb blast, what is actually happening is that the space itself is getting bigger, like dots on the surface of a balloon. as you inflate the dots become further apart although the dots aren't moving of their own accord?

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bluechair84
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Re: for the physicists...

Postby bluechair84 » Tue Oct 02, 2012 10:14 am

But the edge of space itself would have to be moving faster then the speed of light to have gotten away from 'the visible universe' boundary?
And things are always explained better though use of childhood toys. My preference would be lego if anyone can give that kind of analogy!

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Re: for the physicists...

Postby pilch » Tue Oct 02, 2012 12:05 pm

Chunkers1980 wrote:Hawkins explains it on Discovery with a train. But it hurt my head.


I saw some of that programme... I had the same reaction :lol:
A berm? were you expecting one?

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Re: for the physicists...

Postby bennett_346 » Tue Oct 02, 2012 18:58 pm

bluechair84 wrote:But the edge of space itself would have to be moving faster then the speed of light to have gotten away from 'the visible universe' boundary?
And things are always explained better though use of childhood toys. My preference would be lego if anyone can give that kind of analogy!

No. Imagine the light comes from the edge of the universe and arrives here for us to see 8 billion years later. During that time the universe expands and we are too young to see the next amount of light arrive back here (the light that comes from the new edge).

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Re: for the physicists...

Postby cooldad » Tue Oct 02, 2012 19:45 pm

It's all a conspiracy - there are no stars. It's all done with lightbulbs and a bloody big black sheet.
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cooldad
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Re: for the physicists...

Postby cooldad » Tue Oct 02, 2012 19:50 pm

Bugger I thought this was Crudcatcher.
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Re: for the physicists...

Postby bennett_346 » Tue Oct 02, 2012 21:54 pm

cooldad wrote:a bloody big black sheet.

I laid one of those before.

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bluechair84
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Re: for the physicists...

Postby bluechair84 » Wed Oct 03, 2012 06:53 am

bennett_346 wrote:
bluechair84 wrote:But the edge of space itself would have to be moving faster then the speed of light to have gotten away from 'the visible universe' boundary?
And things are always explained better though use of childhood toys. My preference would be lego if anyone can give that kind of analogy!

No. Imagine the light comes from the edge of the universe and arrives here for us to see 8 billion years later. During that time the universe expands and we are too young to see the next amount of light arrive back here (the light that comes from the new edge).


Ahrum... I think that makes some sense.

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Re: for the physicists...

Postby Daz555 » Wed Oct 03, 2012 15:45 pm

error
You only need two tools: WD40 and Duck Tape.
If it doesn't move and should, use the WD40.
If it shouldn't move and does, use the tape.

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Daz555
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Re: for the physicists...

Postby Daz555 » Wed Oct 03, 2012 16:13 pm

bluechair84 wrote:
bennett_346 wrote:
bluechair84 wrote:But the edge of space itself would have to be moving faster then the speed of light to have gotten away from 'the visible universe' boundary?
And things are always explained better though use of childhood toys. My preference would be lego if anyone can give that kind of analogy!

No. Imagine the light comes from the edge of the universe and arrives here for us to see 8 billion years later. During that time the universe expands and we are too young to see the next amount of light arrive back here (the light that comes from the new edge).


Ahrum... I think that makes some sense.

No - it really really does not make any sense at all. That there is no edge to the universe means the explanation given is not helpful I'm afraid. There is also no centre to the universe. There is a common misconception that the universe exploded from the the big bang at a certain "central" point in the universe. From this misconception it is easy to make some assumptions about our universe which are entirely false.

Big Bang by Simon Singh is a great book for the intelligent layman - read it, it is superb.

In the mean time, this wiki article will help:

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

Make sure you at least branch out and read a few of the linked pages as well - cosmic microwave background radiation is very important for example.

There is also a good section on common misconceptions.
You only need two tools: WD40 and Duck Tape.

If it doesn't move and should, use the WD40.

If it shouldn't move and does, use the tape.

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Re: for the physicists...

Postby bluechair84 » Wed Oct 03, 2012 20:07 pm

Daz555 wrote:In the mean time, this wiki article will help:

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

A little bit of my brain just dribbled out of my nose. But I am genuinely interested so I'll look up the book.

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Re: for the physicists...

Postby Daz555 » Thu Oct 04, 2012 08:55 am

On the subject of why there is no edge to the universe (or centre), the balloon analogy helps.

Imagine that your are 2-dimensional being who lives in the surface of a balloon - the material of the balloon represents space and the air inside and outside is not part of this analogy.

As a 2D being you can only move forwards/back/left/right and up/down do not exist for you. As you move around and study your "universe" you will find that it has no edge - you can travel around your universe forever and will return to your originating point if you travel far enough. If you are a 2D chap who dabbles in science you may also have figured out that your space is curved.

The balloon analogy also helps with the idea of the way in which the universe expands for our mythical 2D being. When you inflate the ballon it is space itself which expands, rather than objects flying away 'into" some void or other.

As 3D beings it is hard to scale this idea up in our minds to our own unviverse but we do indeed know that spacetime is curved.
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If it doesn't move and should, use the WD40.

If it shouldn't move and does, use the tape.

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Re: for the physicists...

Postby kieranb » Thu Oct 04, 2012 10:53 am

so, if you're a bit religious, think of it as God blowing up a balloon in a higher dimensional space and we all live on the surface. So obviously the big bang is that first big puff when one starts blowing up a balloon and as the balloon gets bigger the rate of inflation (on the surface of the balloon) slows as the volume and the surface area is increasing but the amount of puff per breath remains the same.

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Re: for the physicists...

Postby pilch » Thu Oct 04, 2012 11:07 am

kieranb wrote:so, if you're a bit religious, think of it as God blowing up a balloon in a higher dimensional space and we all live on the surface. So obviously the big bang is that first big puff when one starts blowing up a balloon and as the balloon gets bigger the rate of inflation (on the surface of the balloon) slows as the volume and the surface area is increasing but the amount of puff per breath remains the same.


But according to Hawkins, time didn't exist before the big bang, therefore there was no 'time' for god or a creator to exist, therefore there is no god...
A berm? were you expecting one?

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cooldad
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Re: for the physicists...

Postby cooldad » Thu Oct 04, 2012 11:13 am

pilch wrote:
kieranb wrote:so, if you're a bit religious, think of it as God blowing up a balloon in a higher dimensional space and we all live on the surface. So obviously the big bang is that first big puff when one starts blowing up a balloon and as the balloon gets bigger the rate of inflation (on the surface of the balloon) slows as the volume and the surface area is increasing but the amount of puff per breath remains the same.


But according to Hawkins, time didn't exist before the big bang, therefore there was no 'time' for god or a creator to exist, therefore there is no god...

Maybe Hawkins is god, just not letting on - would ruin his rep for god to talk through a computer.
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bluechair84
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Re: for the physicists...

Postby bluechair84 » Thu Oct 04, 2012 12:43 pm

The religulous argument that I'm aware of is that God creates the universe in a manner he sees fit, and if he wants it to appear as if he doesn't exist, then that's what we have; a Universe with no experimental or visible signs of his presense. This way, faith can be tested. Which is a stunning argument in both it's ridiculousness and it's simplicity. Hitchens vs Hitchens debat on youtube is fantstic for a creationist vs scientific argument.

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Re: for the physicists...

Postby mrmonkfinger » Thu Oct 04, 2012 13:07 pm

bluechair84 wrote:a Universe with no experimental or visible signs of his presense


No observable or experimentally provable signs of "his presence" means you could never know if "God" was ever the right concept, or even the concept of the universe being deliberately created in any way, which just goes to prove that any religion is a pointless construct of our collective imagination.


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