Can We Really See Into the Past by Observing Distant Worlds?

  • Context: High School 
  • Thread starter Thread starter ianpr
  • Start date Start date
Click For Summary

Discussion Overview

The discussion revolves around the concept of observing distant celestial bodies and the implications of light travel time on our perception of the past. Participants explore whether it is possible to see into the past by observing light from distant planets or events, and whether similar principles could allow for seeing into the future.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that observing light from a planet 100,000 light years away means we are seeing it as it was 100,000 years ago, raising the question of whether the planet still exists.
  • One participant suggests that if light emitted by dinosaurs could be reflected back to Earth, it might be possible to see images of them, although this would be akin to watching an old recording.
  • Another participant questions whether it could be possible to reverse the process and see into the future, but acknowledges that current physics does not support this idea.
  • There is a discussion about whether light can be slowed down or trapped using mirrors, with some participants noting that while it is theoretically possible to reflect light between mirrors, practical limitations make it unfeasible.
  • One participant humorously suggests that taking a photograph is a simpler method than trying to capture light from distant events.
  • Another participant speculates about trapping light in a box of perfect mirrors, questioning the feasibility of such an idea given the absorption of light by mirrors.

Areas of Agreement / Disagreement

Participants express a range of ideas and hypotheses, with no consensus reached on the feasibility of seeing into the future or the practicality of trapping light. The discussion remains unresolved regarding the implications of light travel time and the potential for capturing images of past events.

Contextual Notes

Limitations include the dependence on ideal conditions for trapping light and the unresolved nature of the discussion about seeing into the future, which lacks scientific evidence according to current understanding.

ianpr
Messages
17
Reaction score
0
ok, if when we look at a planet that is say 100000 light years away, and we can see it emitting light, and that light takes 100000 light years to reach us, then is it possible that the planet may not even be there any more? if so i f i was there looking back at erath would i be seeing into the past, like could i be seeing dinosours and stuff walking the earth?
 
Physics news on Phys.org
ianpr said:
ok, if when we look at a planet that is say 100000 light years away, and we can see it emitting light, and that light takes 100000 light years to reach us, then is it possible that the planet may not even be there any more? if so i f i was there looking back at erath would i be seeing into the past, like could i be seeing dinosours and stuff walking the earth?

Yes, all our observations from the cosmos are delayed, some by very long periods of time, e.g. billions of years.

In principle, you could see the dinosaurs. For example if the light emitted by the dinosaurs traveled out into space and was reflected at some mirror millions of lightyears away, and back towards earth. Then you'd see moving images of the dinosaurs from many millions of years ago.

You'r only seeing old moving pictures, you cannot interact with the events taking place in this moving picture, and therefore not influence those events, of course.

So its not really much more interesting than watching an old recording... :-)
 
wow thanks for the reply :-)
 
not that has got me thinking, can this be somehow reversed into seeing into the future? or am i just talking madness?
 
You're welcome!

I should probably mention something more in connection with my example of the cosmic mirror. It is of course too late now to place such a mirror in outer space. You'd have to do it beforehand. RIght now the images of the dinosaurs (the emitted light) are in principle (although increadibly/fantastically weak...) still traveling at the speed of light away from Earth at many millions of lightyears away. It is impossible for us to close that gap, due to the restrictions of special relativity. We'd have to travel faster than light, which is not possible.

Similarly, when you admire yourself in a mirror, standing 0.5m away from it, you are really watching an image of yourself that is around 3 nanoseconds old :-)
 
ianpr said:
not that has got me thinking, can this be somehow reversed into seeing into the future? or am i just talking madness?

There is no scientific evidence that suggests that this would be possible. According to the currently established laws of physics, signals such as light emanating from events only move forward in time. So a signal cannot be sent to the past, to make it possible for someone to see the future.
 
when u say close the gap, do you mean that the light has long gone and is still on the move?, my question then would be can we slow light down down? if light is constant if you get me? then let's make it destination longer, say you used mirrors to deflect it 100 million times round the Earth first then sent it on it way, would that not take longer to get there, i unsderstand the bit you said about you would need to have the mirror in place before hand, just asking would it be possible to slow light down , also i know 100 million times at light speed would not be enougth its just an example? thanks for your time and please tell me if u think i am waisting it and i will leave you be ha ha, thanks again for your time.
 
ianpr said:
when u say close the gap, do you mean that the light has long gone and is still on the move?, my question then would be can we slow light down down? if light is constant if you get me? then let's make it destination longer, say you used mirrors to deflect it 100 million times round the Earth first then sent it on it way, would that not take longer to get there, i unsderstand the bit you said about you would need to have the mirror in place before hand, just asking would it be possible to slow light down , also i know 100 million times at light speed would not be enougth its just an example? thanks for your time and please tell me if u think i am waisting it and i will leave you be ha ha, thanks again for your time.

Yup, it is possible in principle to "save" an image for future observation by letting the emanated light signal reflect e.g. between parallel mirrors. But in practice, it will be impossible, for many reasons. You'd need perfect mirrors, a near perfect vacuum, a perfect setup of perfectly stationary mirrors, etc. But in principle it is possible, if everything is "ideal". Which it never is...
 
torquil said:
Yup, it is possible in principle to "save" an image for future observation by letting the emanated light signal reflect e.g. between parallel mirrors. But in practice, it will be impossible, for many reasons.
Just make a photograph, much simpler.
 
  • #10
ty again
 
  • #11
Passionflower said:
Just make a photograph, much simpler.

Agreed. Hence my comment above about the "light signal from the far past" not being much better than looking at a recording.
 
  • #12
do u think by using your (You'd need perfect mirrors, a near perfect vacuum) u could trap light in a box then u could in theory see these images from the 0.5m like looking into a mirror,.....passion where on Earth ar u goona be able to take a photo of a moving dinosour? as in a real 1?
 
  • #13
ianpr said:
do u think by using your (You'd need perfect mirrors, a near perfect vacuum) u could trap light in a box then u could in theory see these images from the 0.5m like looking into a mirror,.....passion where on Earth ar u goona be able to take a photo of a moving dinosour? as in a real 1?

You won't be able to capture any light from a real dinosaur by any method, since that light is too far away from us and moving away at the speed of light. But you could in principle capture light from some current event, and use it a hundred millions years later, by the methods mentioned. Again, just in principle... :-) If you want to avoid the usual simple techniques for storing images (camera etc).
 
  • #14
no i mean say u shined a torch into a box of perfect mirrors and shut the box... arrr i see... u can't shut the box fast enough. was going to say and trap it, i know mirrors absorb a fraction of the light there for over time it will be gone, but say perfect mirrors?
 
  • #15
but if you could shut that box, maybe this is for another place on here i am not sure,
 

Similar threads

High School New Paradox Discovered, I Think
  • · Replies 98 ·
4
Replies
98
Views
9K
High School Would We See the Same Light After Traveling Back to Earth Faster Than Light?
  • · Replies 2 ·
Replies
2
Views
2K
High School Do all events in my past lightcone have fewer past events in theirs?
  • · Replies 14 ·
Replies
14
Views
1K
High School What if we use a non physical reference point to measure an object's mass?
  • · Replies 5 ·
Replies
5
Views
1K
High School How far away can a World So Newly Born Be at relativistic velocities?
  • · Replies 18 ·
Replies
18
Views
2K
High School Reciprocal time dilation
  • · Replies 15 ·
Replies
15
Views
3K
High School Can We Use Space/Time Fabric to See the Past?
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Does the past of an observer still actually exist in their "now"?
  • · Replies 58 ·
2
Replies
58
Views
6K
High School If light beam travels through a vacuum, then through diamond, then through more vacuum...
  • · Replies 15 ·
Replies
15
Views
2K
High School Why Do Events Freeze For Me at the Speed of Light?
  • · Replies 4 ·
Replies
4
Views
1K