How does light catch up and pass up when looking in to space

How does light catch up and pass up when looking in to space

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Discussion

carmonk

7,910 posts

186 months

Friday 20th January 2012
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AJI said:
philis said:
biggrin
OP: great question!

Also If the static we hear on the radio is the microwave backgound and the remenants of the big bang, and microwaves are part of the electro magnetic spectrum, then why cant i tune my tv in and sit down and watch the big bang?
Thanks


After finding out that light only started being emitted after 'x' number of years I wish I had used the wording of 'radiation' rather than 'light'.

Scientists state they can see the beginnings of the universe if they have a telescope powerful enough, but even after the 'inflation' terminology I still can't see how this 'radiation' can still be 'behind' us in the expansion away from the big bang singularity.

I know cosmic background radiation is all around us and is coming from all directions....but i guess I have to know more about this 'inflation' concept to understand why looking 'behind' us (in the direction away from the singularity) we can still see light-speed EM waves from the singularity catching us up.
The 'behind' is behind in time, not space. It's basically looking at more and more distant objects. If you look at something 1 light year away you're seeing it as it was a year ago. Same with 13.7bn years away, the difference being you're seeing what is essentially the beginnings of the universe. We'll never see the singularity as there was too much matter around and none of the light from the first few thousand years made it through the gaps, but we could well see right up to the point it all cleared up.

nammynake

2,587 posts

172 months

Friday 20th January 2012
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philis said:
Also If the static we hear on the radio is the microwave backgound and the remenants of the big bang, and microwaves are part of the electro magnetic spectrum, then why cant i tune my tv in and sit down and watch the big bang?
The static you hear isn't the CMBR - it's generic interference from terrestrial sources.

R300will

3,799 posts

150 months

Friday 20th January 2012
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nammynake said:
philis said:
Also If the static we hear on the radio is the microwave backgound and the remenants of the big bang, and microwaves are part of the electro magnetic spectrum, then why cant i tune my tv in and sit down and watch the big bang?
The static you hear isn't the CMBR - it's generic interference from terrestrial sources.
If you've got a telescope you can watch it. You will have missed a lot but you might get to see the end if you hang around smile

nammynake

2,587 posts

172 months

Friday 20th January 2012
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Bedazzled said:
The singularity isn't a particular point in space. At the beginning all spacetime existed within the singularity then it inflated into the universe we see today (and beyond). We can detect the 'afterglow' of the big bang all around us; it happened everywhere.
This is the problem. We tend to think of a typical explosion, which radiates from a point in space in all directions. One can not think of the Universe expanding in such a way. The Universe did not expand radially into some external medium. Space itself was created during this expansion. It's like trying to explain atomic structure as electrons being little planets orbiting a central star (nucleus). It just doesn't work that way. It's a convenient method for teaching school children, but creates more problems than it solves IMHO.

don4l

10,058 posts

175 months

Friday 20th January 2012
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nammynake said:
Bedazzled said:
The singularity isn't a particular point in space. At the beginning all spacetime existed within the singularity then it inflated into the universe we see today (and beyond). We can detect the 'afterglow' of the big bang all around us; it happened everywhere.
This is the problem. We tend to think of a typical explosion, which radiates from a point in space in all directions. One can not think of the Universe expanding in such a way. The Universe did not expand radially into some external medium. Space itself was created during this expansion. It's like trying to explain atomic structure as electrons being little planets orbiting a central star (nucleus). It just doesn't work that way. It's a convenient method for teaching school children, but creates more problems than it solves IMHO.
This raises an interesting question.

Was there empty space before the "Big Bang"? You seem to be suggesting that there was no "space" at all before the "Big Bang".


Don
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nammynake

2,587 posts

172 months

Friday 20th January 2012
quotequote all
don4l said:
This raises an interesting question.

Was there empty space before the "Big Bang"? You seem to be suggesting that there was no "space" at all before the "Big Bang".


Don
--
Well it's actually quite a hot topic, but classically the Universe was and IS everything. It didn't originate in some pre-Universe vast space. There was NO before, and there was no space until the Universe came into existence. It didn't expand into some pre-existing volume, it simply expanded itself. Likewise there was no time before the Big Bang. Time was created in that instant.

Now...there are theories which describe the Universe as being one of many (infinite) Universes in a Multiverse, however this requires more than 4 dimensions. Easiest way to explain it is that our Universe (which consists of 4 dimensions) is represented by a flat sheet. The Universe consists of multiple flat sheets, all arranged in parallel along a new fifth dimension. Now, string theory allows up to 11 dimensions - that hurts my brain.

Eric Mc

121,783 posts

264 months

Saturday 21st January 2012
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Next questiuo, if it is the actual fabric of space and time that is expanding, does that mean that I am expanding too - and does that the reason why I keep having to buy trousers with bigger waistlines?

carmonk

7,910 posts

186 months

Saturday 21st January 2012
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Eric Mc said:
Next questiuo, if it is the actual fabric of space and time that is expanding, does that mean that I am expanding too - and does that the reason why I keep having to buy trousers with bigger waistlines?
But your trousers are expanding too, so no monetary outlay needed.

NismoGT

1,634 posts

189 months

Saturday 21st January 2012
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Bedazzled said:
There's been a heated debate on PH before about the nature of spacetime; but whether you view it as a physical thing or not, spacetime is expanding and the rate of expansion is increasing; at first the effects are seen in galaxy separation but if it continues eventually even atoms will fly apart. You'll need more than bigger trousers to cope with that!
Entropy?

R300will

3,799 posts

150 months

Saturday 21st January 2012
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Is it expanding quicker because of dark energy?

ShayneJ

1,073 posts

178 months

Monday 23rd January 2012
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xRIEx said:
Einion Yrth said:
Just to further muddy the waters clarify;

The light in question will arrive at the speed of light, but with a stupidly long wavelength.
if this is so will it not be IR or RF ?

annodomini2

6,860 posts

250 months

Monday 23rd January 2012
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Key point to the earlier posts, the maximum speed of light is a constant, but the speed of light can be lower depending on the medium that is travelling through.

carmonk

7,910 posts

186 months

Tuesday 24th January 2012
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The denser the medium the slower light travels from A to B, but the light is always travelling at C, it's just that it tends to 'bounce around' more.

mrmr96

13,736 posts

203 months

Tuesday 24th January 2012
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nammynake said:
Well it's actually quite a hot topic, but classically the Universe was and IS everything. It didn't originate in some pre-Universe vast space. There was NO before, and there was no space until the Universe came into existence. It didn't expand into some pre-existing volume, it simply expanded itself. Likewise there was no time before the Big Bang. Time was created in that instant.
I don't find it terribly surprising that we can't get our heads around that concept.

Our brains are designed to understand the world "as we see it". So we understand stuff as small as sand, and as big as mountains as that's what we're evolved to cope with. We don't naturally grasp things like bacteria or viruses, or indeed going smaller into sub atomic particles. We kind of understand the moon, but have no real concept of how big the sun is. Therefore interstellar distances are not really within our comprehension.

That example is based on understanding things of different scales. But we also don't see things in 4 Dimensions, and have no real proper understanding of how a "universe" can just "start" and expand into what was previously nothing. Our brains are built for 3D only really, so it doesn't make natural sense to conceive of "space" expanding, without immediately wondering "what is it expanding into".

There's also an interesting maths problem, the details of which I forget. But it basically says that you can't prove the completeness and consistency of rules of a system, using only the rules of the system. It's axiomatically impossible to do so. I imagine a bacteria on a petri dish would consider that dish to be its entire world and not be able to conceive anything else. If we were within such a system (our entire universe as we know it) then we'd not be able to prove otherwise, because to do so would require knowledge from outside the system.

If you can even begin to get your head around how small sub atomic particles are, and how big the universe is by comparison... there's a great many orders of magnitude difference in size/scale. So I wonder how small does stuff REALLY go? And also how big does it REALLY go? Because there could easily be another "world" outside what we know as our universe, in which our universe is but a tiny tiny spec. (Yes, a bit like the ending of Men In Black, but less flippant.)

R300will

3,799 posts

150 months

Tuesday 24th January 2012
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mrmr96 said:
nammynake said:
Well it's actually quite a hot topic, but classically the Universe was and IS everything. It didn't originate in some pre-Universe vast space. There was NO before, and there was no space until the Universe came into existence. It didn't expand into some pre-existing volume, it simply expanded itself. Likewise there was no time before the Big Bang. Time was created in that instant.
I don't find it terribly surprising that we can't get our heads around that concept.

Our brains are designed to understand the world "as we see it". So we understand stuff as small as sand, and as big as mountains as that's what we're evolved to cope with. We don't naturally grasp things like bacteria or viruses, or indeed going smaller into sub atomic particles. We kind of understand the moon, but have no real concept of how big the sun is. Therefore interstellar distances are not really within our comprehension.

That example is based on understanding things of different scales. But we also don't see things in 4 Dimensions, and have no real proper understanding of how a "universe" can just "start" and expand into what was previously nothing. Our brains are built for 3D only really, so it doesn't make natural sense to conceive of "space" expanding, without immediately wondering "what is it expanding into".

There's also an interesting maths problem, the details of which I forget. But it basically says that you can't prove the completeness and consistency of rules of a system, using only the rules of the system. It's axiomatically impossible to do so. I imagine a bacteria on a petri dish would consider that dish to be its entire world and not be able to conceive anything else. If we were within such a system (our entire universe as we know it) then we'd not be able to prove otherwise, because to do so would require knowledge from outside the system.

If you can even begin to get your head around how small sub atomic particles are, and how big the universe is by comparison... there's a great many orders of magnitude difference in size/scale. So I wonder how small does stuff REALLY go? And also how big does it REALLY go? Because there could easily be another "world" outside what we know as our universe, in which our universe is but a tiny tiny spec. (Yes, a bit like the ending of Men In Black, but less flippant.)
What if our universe was simply an atom of another universe nuts

andy_s

19,397 posts

258 months

Tuesday 24th January 2012
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R300will said:
What if our universe was simply an atom of another universe nuts
I don't know about that, but apparently if an atom was blown up to be the same size as the solar system then a neutrino would be the size of a golf ball...no wonder they hardly interact.

AJI

Original Poster:

5,180 posts

216 months

Tuesday 24th January 2012
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With reference to the last couple of posts ....some may find this intersting:
http://www.scaleofuniverse.com/


alock

4,224 posts

210 months

Tuesday 24th January 2012
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AJI said:
But going back to the original question.....so light took 'x'million years to form, and by this time both light and the matter that formed the earth would be 'x'billion kms away from the singularity of the big bang.
So the matter that started emitting light would be at a similar distance from the singularity to that of the matter that formed the earth. <--(assumption made - please correct if wrong).
So as soon as the first light was beginning to be emitted, this would travel at light-speed away from this matter and surely also pass the matter that formed the earth.

So why are we looking 'inwards' towards the centre of the universe to try and see light which should surely be heading away from us that probably passed us 'x' billion years ago?
Simplify the problem to 1 dimension. You and a friend are at opposite ends of a straight road. The council come and dig up the straight road and build a twisty road instead. Neither you or your friend have moved and yet you are now twice as far apart in this 1 dimensional world.

In 3 dimensions, the big bang created the space between objects. They didn't have to move apart to end up further apart wobble

AJI

Original Poster:

5,180 posts

216 months

Tuesday 24th January 2012
quotequote all
Thanks for the replies on this subject.
Explaining the 'inflation' theory in simplified terms is helping a lot.

With the 'twisty road' analogy I can easily 'see' how that works in space-time in that 'distance' can be quickly formed irrespective of initial 'separation'.

I've been trying to read up on a few things, and would it be true to say that as cosmic background radiation is approaching us from all directions that there is no real direction to point a telescope to say that it is pointing towards the 'centre' of the universe?

As cosmic background radiation is coming from all angles and not like a river from its source, then there is no one direction to look to view far enough back in time to be closer to the big bang, in fact you could look in ANY direction to get the 'same' result?

Or have I once again flown off on a tangent?


Also, as the universe is now big enough for light to travel from one side to the other in a time that is longer than the life of the universe, are the TV statements a little misleading, in that what they are saying is that given a powerful enough telescope we can see light that is about the same age as the universe itself, and relating this to the time passed since the big bang?

mrmr96

13,736 posts

203 months

Tuesday 24th January 2012
quotequote all
AJI said:
With reference to the last couple of posts ....some may find this intersting:
http://www.scaleofuniverse.com/
THAT is FANTASTIC!!

It's totally beyond comprehension that stuff THAT BIG can be made out of stuff SO SMALL!!
Whoever put this world together has done an IMMENSE job of it!
I also think there's a really good chance that our theories about "how small" or "how big" stuff can be are STILL incorrect!