Questions about light seen from distant galaxies.

[phiphika1453]

Ok, I have been looking at and reading about Hubble's ultra deep field stuff lately and a weird thought came across me.

Nasa says that the images we see in these UDF images are 13 billion light years old and therefore we know what the galaxies looked like 13 billion light years ago but have no clue of what they look like at this very instant.

So, one day if the technology allowed for good enough resolution and high enough magnification would it be possible to see living dinosaurs roaming on another planet. (Please dont hijack this and turn it into the theory of existence type thread)

Also I know this is really far fetched but, if we sent another Hubble into space to look back at Earth would it be possible to actually witness the happenings on earth as they happened millions of years ago, if hubble were recieving the light reflected by earth from that time period? I have thought about the compications of the telescope not being able to travel fasted than light and all that stuff, but hypothetically this would be possible correct?

Basically my question is, Does light hold the images it was reflected off of forever?

[AceofSpades]

I'm incline to believe (but not sure) that we couldn't. I think the problem is that good enough resolution is directly limited by other light sources overwhelming/contaminating the reflected light that we want to see. Which is the reason you can't see stars when the sun is out.

Of course I really don't know that much about this, so I could be wrong. But it is a really interesting question.

[cambraceres]

Light doesn't really "hold" Images. Images are light. The light from other stars is how they looked at the time this light was originated, but this light has been skewed and bent. In the case of a star this only changes it's position in the sky. Gravity pulls and twists light as it travels throughout the universe.

A satellite would not be able to observe earth in a past time sense beacause it cannot travel fast enough. Another peoblem is that high resolution images of far away entities are almost a contradiction in terms. As the weak light signatures of small scale objects travels through space, it is washed with other light so that you can observe only macro phenomena. It is analogous to looking at the sun to try to see a man striking a match om mercury.

Hope this isn't confusing, because I am generally confused and this shows in scientific discourse.

Cambraceres

[yukoncpa]

[ QUOTE ]
Basically my question is, Does light hold the images it was reflected off of forever?



[/ QUOTE ] As a complete layman on this subject, I'm going to say that a photon, unlike a diamond, lasts forever. Any information carried on that photon will always be there. I please welcome comments.

[cambraceres]

[ QUOTE ]
[ QUOTE ]
Basically my question is, Does light hold the images it was reflected off of forever?



[/ QUOTE ] As a complete layman on this subject, I'm going to say that a photon, unlike a diamond, lasts forever. Any information carried on that photon will always be there. I please welcome comments.

[/ QUOTE ]

Photons can potentially last that long, but they do dissappear and are also synthesized by natural processes.

[yukoncpa]

[ QUOTE ]
Photons can potentially last that long, but they do dissappear and are also synthesized by natural processes.



[/ QUOTE ] I guess I can understand photons being absorbed, etc, etc., but I was thinking in terms of relativity. If something is traveling the speed of light, does time not stop for this particle? I always looked at light speed particles as infinite for this reason. Can you explain this to me?

[cambraceres]

[ QUOTE ]
[ QUOTE ]
Photons can potentially last that long, but they do dissappear and are also synthesized by natural processes.



[/ QUOTE ] I guess I can understand photons being absorbed, etc, etc., but I was thinking in terms of relativity. If something is traveling the speed of light, does time not stop for this particle? I always looked at light speed particles as infinite for this reason. Can you explain this to me?

[/ QUOTE ]

Photons behave in a counterintuitive way. They can travel back in time, then forward, then back, stand still, and dissappear altogether.

I suppose by infinite you mean to say of indeterminate duration? If so this is true, they are not particles which only last for a set time period, nor do they follow classical rules. Photons can even, for extremely brief periods, violate conservation of energy relations. This is a Quantum phenomena.

Light is a complicated entity shrouded in the smoke of perceived simplicity. Feynman has done the best recent work on light. QED is a classic which explains these things in layman terms. If you are interested this is a book to read.

PM me if you wish, I'm busy but do so love these topics

Cambraceres

[mostsmooth]

[ QUOTE ]

Nasa says that the images we see in these UDF images are 13 billion light years old and therefore we know what the galaxies looked like 13 billion light years ago but have no clue of what they look like at this very instant.


[/ QUOTE ]
im not trying to make fun of you, just helping here: a light year is a measure of distance, not time. so those images would be 13billion years old. a light year is ~6 trillion miles. /images/graemlins/cool.gif

[miajag]

Theoretically it is possible. The fact that we are seeing light from those galaxies at all shows that the photons can travel the distance. However a telescope capable of achieving that level of resolution would probably have to be at least the size of the Milky Way galaxy, if not larger.

[mostsmooth]

[ QUOTE ]
Theoretically it is possible. The fact that we are seeing light from those galaxies at all shows that the photons can travel the distance. However a telescope capable of achieving that level of resolution would probably have to be at least the size of the Milky Way galaxy, if not larger.

[/ QUOTE ]
thats a big scope. how much does one of those cost?

[CORed]

[ QUOTE ]
Also I know this is really far fetched but, if we sent another Hubble into space to look back at Earth would it be possible to actually witness the happenings on earth as they happened millions of years ago, if hubble were recieving the light reflected by earth from that time period? I have thought about the compications of the telescope not being able to travel fasted than light and all that stuff, but hypothetically this would be possible correct?

[/ QUOTE ]

Well the telescope couldn't travel faster than light, so it would take >1,000,000 years to travel 1,000,000 light years. It would take another 1,000,000 years for any signal it sent to get back to Earth.

However, if some extraterrestrial beings 100,000,000 light years away has built a telescope with sufficient resolution to see what's happening on the surface of the planet, they would be seeing dinosaurs right now (although "right now" is really pretty much meaningless when considering an observer that far away).

[Trantor]

[ QUOTE ]
Ok, I have been looking at and reading about Hubble's ultra deep field stuff lately and a weird thought came across me.

Nasa says that the images we see in these UDF images are 13 billion light years old and therefore we know what the galaxies looked like 13 billion light years ago but have no clue of what they look like at this very instant.

So, one day if the technology allowed for good enough resolution and high enough magnification would it be possible to see living dinosaurs roaming on another planet. (Please dont hijack this and turn it into the theory of existence type thread)

Also I know this is really far fetched but, if we sent another Hubble into space to look back at Earth would it be possible to actually witness the happenings on earth as they happened millions of years ago, if hubble were recieving the light reflected by earth from that time period? I have thought about the compications of the telescope not being able to travel fasted than light and all that stuff, but hypothetically this would be possible correct?

Basically my question is, Does light hold the images it was reflected off of forever?

[/ QUOTE ]
As another poser has pointed out you can't launch a telescope to overtake light from the earth and so see back in time even for an observer at the telescope. But in a finoite universe the light from the early solar sytem could havve gone out in one dierection and return having gone round the universe in the opposite direction. People are trying to detect just such signals which would be looking back in time.

http://www.tcsdaily.com/article.aspx?id=102203Bhttp://www.tcsdaily.com/article.aspx?id=102203B

[phiphika1453]

[ QUOTE ]
[ QUOTE ]

Nasa says that the images we see in these UDF images are 13 billion light years old and therefore we know what the galaxies looked like 13 billion light years ago but have no clue of what they look like at this very instant.


[/ QUOTE ]
im not trying to make fun of you, just helping here: a light year is a measure of distance, not time. so those images would be 13billion years old. a light year is ~6 trillion miles. /images/graemlins/cool.gif

[/ QUOTE ]

Thanks for pointing that out in a non-degrading manner. Just got my words twisted around a little bit.

So, about light not "holding" images. Maybe that word was a bad choice but I still dont understand how the light we see from these galaxies has not been bent/distoted so much that we are still able to resolve the arms of some spral galaxies.

I have read some stuff on both the wave and particle theories of light. That damn light [censored] is amazing.