Ok lads n lasses iv been thinking about this for ooo about 5 mins.What would happen if we used the farthest from earth telescope(or sent a telescope millions of miles out)and looked at earth.Would we see our past since it takes light so long to travel these distances.You know the light that we would see would be from a long long time ago.Let the bamming up commence

I think in the time it took (the telescope) to get there, then the time it took the light (from Earth) to get there, then the time it took to send the data back would negate the "seeing into the past" thing.
But, if we had a telescope there NOW which could instantaneously send back images of Earth then we would be seeing into the past, in theory. (I think )

I want to reply to this, but my head is spinning to much..to dizzy.

I imagine you would have to travel faster than light to get to a place where you could see the past. That alone would be a massive hurdle

they actually did this in Hubbards novel "Battlefield earth" but of course they had the aid of teleportation and really powerful telescopes.

IN fact a ESA telescope is going to be attempting to take picutres of the Moon and get first hand evidance of the moon landing.

To really make this work you need to have a telescope that would alsmot need to use a black hole as a lens to amplify the light, and FTL travel

just think, an alien with such a telescope 500 light years away could see us in the middle ages.

Thats exactly it,You would have to send the Telescope Faster than the light travels so it would be cathing up to past light So IF you traveled 2 X the speed of light for 50 Years you would see 100 years past light from earth. Now if you could go 4 X times the speed of light and go 50 lights years. You would catch up to 200 years ago. Now how would you send a message to the planet? Could you send somthing 4 X times the speed of light (A message) back to earth and would that mean it gets there 50 years ago (or something like that).

Read Universe in a Nut Shell by Hawkings, Has some time theroies alot to do with Einstiens Light speed Theroies

Yes, if you moved to a distant location at ultra speeds and had an extremely powerful telescope, you could observe things that happened in the past.

In theory it sounds like it would work, but consider this. Think of a probe 1 light year away,.....observing the earth. Everything it views is exactly 1 year old when it hits the lens. It would then have to transmit the information BACK to Earth. The transmission would move at the speed of light and take 1 year to get to us. The resulting image would be 2 years old. At 1 light year,....the best we could hope to see are weather patterns. So, even though it's theoreticaly possible,....there would be no point. We already have MUCH more detailed information about the weather 2 years ago than this setup would provide. It's simply impractical. I'm more interested in tomorrows weather frankly.

Actually, i have to wonder, because of the twin paradox.

Take a pair of twins, move one at faster than the speed of light for a while and return him to earth. he is now youner than the twin that remained on earth.

So a device traveling at ultra high speeds, would it be able to catch up to where light from earth, say from a thousand years ago, will be when he stops? Because it will not be where it is now, or merely, say, where it will be in an hours worth of flight time (time on the ship) form now.

Originally posted by Nygdan
Take a pair of twins, move one at faster than the speed of light for a while and return him to earth. he is now youner than the twin that remained on earth.

So a device traveling at ultra high speeds, would it be able to catch up to where light from earth, say from a thousand years ago, will be when he stops?

First, time dilation works also in speeds under c (no need to exceed it).
Effect of it just gets bigger only at speeds near speed of light. Even small speeds are enough if you measure time precisely. (like atom clocks, other in ground and other in aircraft)


If you would move away from earth with bigger speed than c you would see things in earth happening backwards because light which left earth at the moment of your departure would be left behind you and you would be continuously catching light which left earth earlier and earlier.
Logically if you would move at speed of light you would see earth looking always same as it was at the time of your departure.
And if you would be teleported to one light year away you would see earth like what it was one year ago.

So in astronomy distances mean also other thing, if object is 100 light years away we see it as like it was 100 years ago because it takes that long for information to arrive.
For example Orion's Betelgeuze might have already gone supernova but we don't know about it simply because information from that moves at speed of light and trip takes couple hundred years.
Also nearest other bigger galaxy, M31, is two million LYs away so we see "two million years old image" of it.

But how does time dialation factor into it? If time on earth and time in the ship are running differently, then why isn't time outside the ship also running differently? And if time outside the ship is different then the light will have moved to a different point than if it was continuing the same as inside the ship.

IE, i want to see what was happening a thousand years ago. Light from a thousand years ago is a certain point now. It takes me a year of travel time, so lets say light will be at point A. I jump in my ship travel at my speed and, what exactly? Travel for a year? But then, say, ten years has progressed on earth. So shouldn't that light be at point A plus a distance of 9 light years (since A is where its going to be in one year already, so its not plus ten light years)?

If you were on mars you would look at earth and see it as it was 8? min ago I believe. Therefore you would see earths past just as we see mars past when we look at it..

X

By the Time u got a telescope far enough out what u would see would probably be what it looked like when the telescope left earth

There is a much easier way to view the past and you don't have to travel
off the earth. To answer the question at hand, yes you would be viewing
the past from a telescope off earth.

Now for the easy way: Get out your camcorder and tape any scene of interest.
Next wait until tomorrow and view the tape. Presto! you're viewing one day
into the past.

Viewing the Future, now that would be a trick.

erm traveling at speed of light to next galaxy m31 would take 2 million years yes?

so how fast would we need to travelto get there in say 1-10 year trip there and back again??

would we need to travel at something like half million x speed of light???

as i see it even if we traveled at speed of light we cant get far into universe, now if we travel at 10 x speed of light still cant get that far into universe..........

Originally posted by Nygdan
IE, i want to see what was happening a thousand years ago. Light from a thousand years ago is a certain point now. It takes me a year of travel time, so lets say light will be at point A. I jump in my ship travel at my speed and, what exactly? Travel for a year? But then, say, ten years has progressed on earth. So shouldn't that light be at point A plus a distance of 9 light years (since A is where its going to be in one year already, so its not plus ten light years)?

Light which left earth 1000 years ago is currently 1000 light years away.

So with one year travel time your speed would have to be 1001x speed of flight (with forgetting how do you get to that speed or apparent speed) to see earth at it was thousand year ago.

And in this example one year travel time would be in timescale of earth, not your ship traveling away at 1001c.
So in this we use one clock for everyone involved. (time of "stationary" reference clock)

Originally posted by Blobby 2
erm traveling at speed of light to next galaxy m31 would take 2 million years yes?

Yes and no, it just depends on who is watching.

In "reference" time (earth's time) it would take two millions years.
But because of great speed time inside that ship would go much slower.

That's what relativity means!

I always get brain-boggled at thinking how large the universe is, I mean, traveling at the speed of light, it'd take you 100,000 YEARS just to get across the galaxy, and that is just a straight ride. If you wanna stop and explore, sheesh.

If I could live forever and travel the universe at my own will, I'd search this planet all over, then leave and search around the galaxy for awhile, and then after oh a few hundred million years probably of having searched through this galaxy and its planets, I'd go to the next galaxy, and so forth.

The universe sure is huge. I truly wonder what is out there??

That's the beauty of an apparently-infinite universe: It's more useful to ask, "what isn't out there?"

One of my college astronomy texts had a deep field picture (i.e. of nothing in particular) taken by some ground observatory. All you can really see in the 2 x 3-inch pic are thousands of blue-white dots/pixels. According to the caption, the pic was something like a tenth-degree of arc across, and every dot was a galaxy.

Now, if that's not freakin' amazing, I have no idea what amazing is.

What came to mind right away when I first saw it was, "Given this, how can anyone believe life exists nowhere else?"

If I can find this pic, I'll post it with references...

Originally posted by ShiftTrio
Thats exactly it,You would have to send the Telescope Faster than the light travels so it would be cathing up to past light So IF you traveled 2 X the speed of light for 50 Years you would see 100 years past light from earth. Now if you could go 4 X times the speed of light and go 50 lights years. You would catch up to 200 years ago. Now how would you send a message to the planet? Could you send somthing 4 X times the speed of light (A message) back to earth and would that mean it gets there 50 years ago (or something like that).

Read Universe in a Nut Shell by Hawkings, Has some time theroies alot to do with Einstiens Light speed Theroies

The sending of the message would be irrelevant as earth would still be in the same time it is now.

For instance, you can see a stars light from lets say 1000000 years ago, but it doesn't mean that the actual star at this point in time is 1000000 years younger, it just means that it took a while for the light to get here, thus sending a message back would be irrelevant and people would think you were nuts as they already knew that.