If light travels at 180,000 miles a second, if and alien civilization was looking at us from thousands of lightyears away, and decided to travel, at light speed, towards earth, wouldnt they be seeing earth fastforwarded until they arrive to see a current intelligent people, since the light would be proccessed by an eye two times faster.

Question

apoorvk · Answer

nah.. "law of relativity"... for any thing travelling at the speed of light or at comparable speeds, will follow the principle of special relativity!

jamesj · Answer

If they travel at the speed of light, for them time will stop.  This is a key prediction of special relativity.  So for them, the time required to reach here is zero.  Hence the image they see of earth will be discontinuous.  One second, it's from thousands of years ago; next, it's the present day.

What's more interesting to ask is what happens if they travel close to--but not at--the speed of light.  Then for them time slows down and they will see the history of the earth in high speed.  The time dilation factor is a key prediction of Special Relativity and if you're interested, I suggest you find something fun to read on the topic.  It is fascinating!

apoorvk · Answer

Awesome explanation @jamesj !!

anonymous · Answer

Awesome, so as long as you arent traveling at light speed, because the other person added comparable speeds

apoorvk · Answer

comparable speeds mean the speeds "close to".. as jamesj said in the second part of his answer.