If You Could Look At Earth From 65 Million Light Years Away. You Would See Dinosaurs.

If You Could Look At Earth From 65 Million Light Years Away. You Would See Dinosaurs. 

-Crazy Facts Of Cosmology. 

Light that left the Earth 65 million years ago is now 65 million light years away, and an alien with big a big enough telescope pointed directly at the Earth might be able to see dinosaurs.

Yes that planet looking at Earth with sufficiently powered telescopes will not be seeing survivor on TV.Practically, such a telescope would be impossibily huge.

they would see the light that left the Earth from 65 million years ago.

At such distance, they will need to take long exposure images from Earth,  and that means they will only gett a blurr of everything. Not a nice and sharp image of dinosaur. Even if they get a telescope big enough to see Earth.

As for watching the past keep in mind we see the sun from what happen to it 8 minutes ago from our point of view, 45 minutes for Jupiter,  and we see the light from what was happening in the Andromeda galaxy 2.5 million years ago(1/30 as far as your hypothetical planet. ie.  One powerful telescope they have.

Light takes time travel, so looking at anything is tantamount to looking back in time.

The telescope lens or mirror would need to be at least 50 trillion km across.  The smaller the angle of view  needed, the larger to objective mirror or lens needed.