How does light catch up and pass up when looking in to space
Discussion
After the recent 'stargazing' programs on BBC they talked about looking 'back in time' and also looking back to the beginnings of the universe.
I fully grasp that light takes time to travel from one point in space to another and when light takes 1000's of years to travel this distance we see the object as it was 1000's years ago.
But this surely breaks down when they say we can look back from our current position in the universe and claim to see far enough to state we are looking at the 'beginnings' of the universe?
With the big bang theory everything was in a singularity which 'exploded' in the timeline shown on the image below..
http://www.universetoday.com/wp-content/uploads/20...
The image above, I'm guessing, should be read as if this shape and events took place in 360 degrees in all directions and not only just the left-to-right diagrammatic that is shown.
So if all 'matter' was originally in a singularity and there was a rapid expansion, and the speed of light has a finite value with 'C' at its maximum in a vacuum, then why hasn't all the light passed the material that formed the earth in the early stages of the big bang?
The way they say on TV that we are able to look back in time suggests that the earth (or the material that formed the earth) was able to travel faster than light and we are now able to wait for the singularity events and the light emitted from it to catch us up....allowing us to view it as it passes the earth.
If I explain it like this..... say for example a TV station existed at the time of the big bang and was located at the singularity.....and aired a single episode of Eastenders, it is a case of the material that formed earth having to travel/expand faster away from the singularity than the EM signal of Eastenders in order we can wait for it to arrive at a later date?
And then if we had a telescope powerful enough we could then watch/receive this particular episode of Eastenders?
If this is true then faster than light speeds are possible no?
Or is something else happening? <--I'm guessing this!
I fully grasp that light takes time to travel from one point in space to another and when light takes 1000's of years to travel this distance we see the object as it was 1000's years ago.
But this surely breaks down when they say we can look back from our current position in the universe and claim to see far enough to state we are looking at the 'beginnings' of the universe?
With the big bang theory everything was in a singularity which 'exploded' in the timeline shown on the image below..
http://www.universetoday.com/wp-content/uploads/20...
The image above, I'm guessing, should be read as if this shape and events took place in 360 degrees in all directions and not only just the left-to-right diagrammatic that is shown.
So if all 'matter' was originally in a singularity and there was a rapid expansion, and the speed of light has a finite value with 'C' at its maximum in a vacuum, then why hasn't all the light passed the material that formed the earth in the early stages of the big bang?
The way they say on TV that we are able to look back in time suggests that the earth (or the material that formed the earth) was able to travel faster than light and we are now able to wait for the singularity events and the light emitted from it to catch us up....allowing us to view it as it passes the earth.
If I explain it like this..... say for example a TV station existed at the time of the big bang and was located at the singularity.....and aired a single episode of Eastenders, it is a case of the material that formed earth having to travel/expand faster away from the singularity than the EM signal of Eastenders in order we can wait for it to arrive at a later date?
And then if we had a telescope powerful enough we could then watch/receive this particular episode of Eastenders?
If this is true then faster than light speeds are possible no?
Or is something else happening? <--I'm guessing this!
Inflation. It's proposed that, rather than everything in the universe flying apart, it is the fabric of space itself which is expanding. The usual example is dots on a balloon as it is blown up. Things aren't moving away in a fixed space, the space itself is getting bigger.
No it makes little sense to me either!
No it makes little sense to me either!
Imagine something traveling away from you at the speed of light. If it is emitting light, and it is traveling away from you at the speed of light, no light from that object will ever reach you.
The reason for that, is because in the vastness of space, you too are also moving away from that object at the speed of light as there is no reference point of what is moving away from what.
If it is traveling fractionally slower than the speed of light away from you, a tiny amount of light will reach you very slowly indeed. In theory, light could be reaching you that is millions or even billions of years old.
It's f
ked up, but that's the universe for you!
The reason for that, is because in the vastness of space, you too are also moving away from that object at the speed of light as there is no reference point of what is moving away from what.
If it is traveling fractionally slower than the speed of light away from you, a tiny amount of light will reach you very slowly indeed. In theory, light could be reaching you that is millions or even billions of years old.
It's f
ked up, but that's the universe for you!Mr Gear said:
If it is traveling fractionally slower than the speed of light away from you, a tiny amount of light will reach you very slowly indeed. In theory, light could be reaching you that is millions or even billions of years old.
Huh?Doesn't light always reach you at the "speed of light".
Don
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don4l said:
Huh?
Doesn't light always reach you at the "speed of light".
Don
--
Not if YOU are moving away from the source of light at the speed of light Doesn't light always reach you at the "speed of light".
Don
--
In an expanding universe, that is basically how objects move relative to each other.
If you fire a satellite out of orbit, is IT moving away from earth, or is the earth moving away from it?
I think this is right – The things we see that are 'at the beginning of the universe' are moving away (or us moving away from them) but not at the speed of light. So when a photon is emitted it is at a single point in space. It then takes a finite amount of time to reach us, relative to how fast we are moving from that point of origin. So you are viewing it where it was in space at that point in time, we know the points (us and the origin of the light) are moving apart because the light red-shifts, moving into the red end of the spectrum as the light waves elongate. The light that we see is where the object was at that time not where it is now.
Mr Gear said:
Not if YOU are moving away from the source of light at the speed of light
In an expanding universe, that is basically how objects move relative to each other.
If you fire a satellite out of orbit, is IT moving away from earth, or is the earth moving away from it?
I think that you will find that light can only ever reach you at "the speed of light" according to the theory of special relativity. In an expanding universe, that is basically how objects move relative to each other.
If you fire a satellite out of orbit, is IT moving away from earth, or is the earth moving away from it?
I'm quite receptive to new ideas, so perhaps you would explain to us why Einstein was wrong. Personally, I don't believe that Einstein got it 100% correct, so I am genuinely willing to give you a fair hearing.
You could be in line for a Nobel Prize
.Don
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don4l said:
Mr Gear said:
Not if YOU are moving away from the source of light at the speed of light
In an expanding universe, that is basically how objects move relative to each other.
If you fire a satellite out of orbit, is IT moving away from earth, or is the earth moving away from it?
I think that you will find that light can only ever reach you at "the speed of light" according to the theory of special relativity. In an expanding universe, that is basically how objects move relative to each other.
If you fire a satellite out of orbit, is IT moving away from earth, or is the earth moving away from it?
I'm quite receptive to new ideas, so perhaps you would explain to us why Einstein was wrong. Personally, I don't believe that Einstein got it 100% correct, so I am genuinely willing to give you a fair hearing.
You could be in line for a Nobel Prize
.Don
--
The light in question will arrive at the speed of light, but with a stupidly long wavelength.
Yeah this is what I thought.....it comes back to the thought experiment of - if you were in a spacecraft travelling at light speed....looking ahead would you see light at twice the intensity?...answer = no....also if you were to look behind you, would you see no light as it is unable to catch you up?....answer = no.
What you would see is light with different wavelengths. (please correct if wrong)
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?
What you would see is light with different wavelengths. (please correct if wrong)
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?
It's because with inflation it was spacetime that was expanding, with the matter staying in the same place and being repositioned and multiplied. So the inflation of the actual fabric of spacetime created most of the observable universe in seconds, where we already had our widely spaced positions in the universe long before the time matter started to coalesce and turn to stars. So you aren't seeing it close to the singularity, it had already inflated and is now expanding and traveling away which is why it red shifts.
Mr Gear said:
It's fked up, but that's the universe for you!
ked up, but that's the universe for you!
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?
philis said:
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?
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.
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