MegaSack DRAW - This year's winner is user - rgwb
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A was idly wondering if it was possible to make a camera that showed live pictures of the past (as they happened not recorded) by sending a live feed very far away into space then beaming it back to Earth*. Ahh the joys of not sleeping ! Anyhow in my quest for the inevitable answer I came across this rather nice website.
[url= http://www.askamathematician.com/ ]Ask a Physicist[/url]
Which is worth a look if you are interested in such stuff.
* Using the twin paradox for digital info rather than twins.**
** This Question is more than likely only possible due my complete and utter non understanding of Relativity.
My heads hurt.
you should try reddit.com/r/askscience
No because the info would be beamed at the speed of light.
If you mean transmitting the info using quantum entanglement then (if that's possible) surely what you would see is not the past but the present?
[url= http://www.dnatube.com/video/28258/Michio-Kaku-on-Communicating-via-Quantum-Entanglement ]Linky[/url]
Oh, in answer to the question: Yes.
But you could also just use a tape loop, or delay all frames by an equal, fixed number of seconds [as you suggested]. Both of these would be easier.
gofasterstripes - Member
My heads hurt.
Mine too 😀
Ok I reckon at best it would be no better than a recording the past and just watching it without all the beaming nonsense.
Because if it did work at some stage you would need to see images from before the camera was switched on which is clearly not going to happen regardless of the relativity effects of sending the data on a long fast journey.
I wondered what if the camera was not pointing the the way you wanted. You could send a signal to the camera to move, however you would not see this change in camera position until sometime after you sent the signal. Meaning surely that you were not watching the past as it happened rather than a recording. ( I had to draw a picture to work this out 😳 )
Please feel free to flame 😀
Because if it did work at some stage you would need to see images from before the camera was switched on which is clearly not going to happen
I wondered if the OP was making some reference to the Andromeda Paradox whereby a moving and a stationary observer will witness different 'present moments' in a distant place.
Actually the question or query is not clear enough to give an answer.
I wondered if the OP was making some reference to the Andromeda Paradox whereby a moving and a stationary observer will witness different 'present moments' in a distant place.
Looks up Andromeda Paradox 🙂
forwards to my brother for explanation - he is the physicist, I live in the real world
Spin - Member
Actually the question or query is not clear enough to give an answer.
This is very true. I am now certain that the answer is no, However I am still unclear myself what the question is. The original reason for posting was not the question ( although I would be very happy if someone let me know what it was ) but to highlight the website.
It is interesting to find out about oneself, that you can know so little about a subject that you can not even put together a meaningful question..That is not getting you SPIN for pointing this out as I have been wrestling with clarifying the question to myself all morning.
I have been wrestling with clarifying the question to myself all morning.
A thoroughly worthwhile activity.
Wouldn't it just be easier to watch Gold, Yesterday, or ITV4?
What's the point? It was all in black and white then so nobody would watch it.
Isn't this exactly what happens normally? When you watch "live" television, it's taken a finite amount of time to reach you from where it was being filmed.
That time is at best, the time taken for light to travel from the camera to you - a few seconds if, for example, the camera is sitting on the moon, about 30 minutes if it's on Mars, or 35 hours if it's the one on Voyager I.
[url= http://voyager.jpl.nasa.gov/index.html ]
[img] 
[/img][/url]
But if you are the signal* how long does it feel like it's taken [i]you [/i] to travel?
*
[img] 
[/img]
oldnpastit - Member
Isn't this exactly what happens normally? When you watch "live" television, it's taken a finite amount of time to reach you from where it was being filmed.
Yes
But I think my question lies somewhere in :-
gofasterstripes - Member
But if you are the signal* how long does it feel like it's taken you to travel?
In the twin paradox the twin that returns from the journey is younger than the one that stays on earth. If you exchange the twin for data ( as it is easier to send data at the speed of light ( or very quickly anyway)) does the data also come back younger ? I very much doubt it.
What is clear is that I have no idea what my own question is 😀
does the data also come back younger
If that's your question the answer is no.
The visual data you encoded as a radio wave remains exactly the same.
In the twin paradox the twin that returns from the journey is younger than the one that stays on earth.
I'm not a physicist, but in the twins paradox, the twin who goes on the journey travels at speed, and time slows down for her due to all that special relativity stuff (i.e. time dilation).
I think what that means is that if you are a photon (one of the photon's encoding this stream of data) then time is at a standstill: the photon arrives at the end of its journey the same "age" as when it departed. So for the photon, the journey from (say) Voyager I is instantaneous.
That's also why if you were to get a spaceship going fast enough to the nearest star, then for the people on board it would appear to take a lot less time than for observers on earth.
For observers on earth watching the photon, it will take distance/speed-of-light seconds to arrive though, so no use for budding time machine builders.
But I could be talking nonsense here.