## Compassionate 3 years ago So if a star is 1000 light years away, that means I'm seeing the star how it was 1000 light years ago. Here's my question: if I travel far enough to view earth 65 million years ago and I have a telescope strong enough to view the earth, theoretically speaking, I can see dinosaurs?

1. lgbasallote

based on the phrasing of your question "I travel far enough to view earth 65 million years ago" that means you *are* far enough and *can* see the earth 65 million years ago. but if you are just 65 million light years from earth then you cant see earth 65 million years ago. what you'll see is 130 million years ago

2. Compassionate

Ah, smart one. So what if I'm 32.5 years from earth?

3. agentx5

First off I think you meant light-years (which is a distance), "32.5 years" is a measure of time. If you were already 32.5 light-years (ly) from earth, oncoming light you see that passes by and heads on back behind you to earth won't reach the rest of us for 32.5 years. Whereas if we try to send you flash of light from earth, you won't see it for 32.5 years. Make sense? Light is simply the speed of massless particles, and since light was the first discovered, it's called the speed of light. If you take something that has mass and go faster (approaching this high speed), your frame of reference shifts and time slows down for you the traveler. Which is what I think @lgbasallote was trying to get at. :-) Interesting FYI: Mass is now thought of as interactions with the Higgs field. As of this summer, the standard model is now a full-set. But there's one issue with that, gravity & the concept of space-time. This is why so many physicists are looking for this holy-grail unified theory that connects it all together mathematically.

4. theyatin

let me explain this way if you see a stoem on a planet 4 light years far from earth that means the storm was 4 years ago from no as per date on earth. . . i dont think you would be able to see any planet from 32.5 million light years far. . .

5. henpen

No. Imagine the last rays of light that the last dinosaurs gave off (ie- the last years that you could see them). Let's simplify this to a very powerful red LED blinking once, 65 million years ago. The rays will spread out spherically|dw:1342800242448:dw| The 'last sphere of dinosaur light' reaches x after (say) 1 million years, y after 4 and z after 6 million. This surface is now 65 million light years away from us, and to see dinosaurs you must at least catch up with that (but ideally if you would need to see older light to really see the best ones). Nothing with mass can travel at the speed of light, and the last light is receding away from you at light speed (ie- faster than you can ever go). Even if you did reach 0.99999 light speed without dying, the light will still travel away from you at 1 light speed relative to you (so not 0.00001 as you would expect), so the situation is even worse, if possible.