# Could we "catch" the light from prehistoric Earth and see dinosaurs?

My first question on your forum. I just found you last week and have spent a whole lot of time reading.

My question: Not actually a question, but a supposition seeking confirmation.

Were it possible to travel faster than light, could we "catch" the light from prehistoric Earth and see dinosaurs? So, for instance, the Tyrannosuarus Rex was in existence during the Cretaceous period 66-68 million years ago. With FTL, could we travel some 68-million light years away, turn around to face Earth and watch a T-Rex chow down?

All the more reason to work on FTL. :)

Thanks,

Steve

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Hi and welcome to PF!
With FTL, could we travel some 68-million light years away, turn around to face Earth and watch a T-Rex chow down?
Following your logic you'd have to be 68 million light years away INSTANTLY to see what happened here 68 million years ago. If the universe allowed mass to travel faster than c (which it appears it does not) you would have to go 2c for 68 million years (ignoring expansion and time dilation) and maybe you could see Earth dim the Sun if it passes our line of sight, and perhaps make out some contents of the atmosphere from spectral analysis, but certainly we could not see any details of the planet.

Well.......that kinda sucks. :)

Thanks for the reply.....and for crushing my dreams.

Yes, it would have to instantaneously travel ~68 million light years. I'll go one step further......assuming we have advanced enough technologically and scientifically to travel some 68 millions light years in an instant, I'd guess we would have advanced our optics enough in that time to be able to see objects 68 million light years away more clearly than you describe in your response.

Steve

phinds
Gold Member
2019 Award
Optics improvement "more clearly than you describe ... ", even if representing an unlikely couple of orders of magnitude in improvement, would STILL not be good enough for your purposes.

@smsaks2000, your original question amounts to "if the laws of physics didn't apply, what would the laws of physics have to say about <insert nonsense of your choice>". You would likely find it more interesting, and certainly more productive, to study some actual physics rather than worry about impossible scenarios. I'm not trying to "crush your dreams", but you should check the forum rules on personal speculation.

russ_watters
Mentor
68 million light years is pretty far away and the questions are unreasonable enough that I'm going to ignore them and ask and answer my own question:

Could we take a picture of an animal on another planet nearby in our galaxy? With any level of technology?

No. There are ways of getting around resolution limits, but there is no reasonable way to get around exposure limits. Even as close as a few light years away, even a truly enormous telescope (like, a solid mirror the size of earth) would probably need days of exposure to capture enough light to see fine details. So even if it had the needed resolution, it wouldn't catch a moving animal. Early photographs here had the same problem.

(I might be able to put some numbers to that later...)