Theoretically, would this work?

I call my theorem the Kobayashi Quantum Time Flux Observation Theory™©® - let’s hope it makes some kind of sense, please excuse any poor wording on my part.

I was inspired by the fact that the stars we observe from Earth are already billions of years old when we see them, due to the time it takes light to get here.
Logically, wouldn’t the same apply to Earth? If we developed a craft that went faster than the speed of light we could observe the Earth as it was in any particular time frame. If, for example, we went 100 light years away from Earth we would see it Earth 100 years ago.
Obviously, you’d have to account for the amount of time it takes for the craft to reach it’s destination in order to see reflected light (or anything else we could pick up) from the Earth 100 years ago.
You’d also need incredibly powerful telescopes or other means of detection - I know we presently do not have the technology to locate, let alone observe, individual planets beyond our solar system). We’d also need some way of getting data back to Earth, I realise.

Of course, all this is far in the future due to the technology involved. I’m just wondering - is it possible in a hypothetical sense?

Nothing can exceed the speed of light - so no, it couldn’t work.

Crap, I forgot that falldown point straight from the get-go. Foiled again by Einstein! Oh well, it was a nice theory while it lasted.

Sorry for the double-post; but I have a new idea.

The theory does not necessarily need a faster-than-light object to work. It needs some sort of object that can observe the Earth to be located x light years away from Earth when you want to observe Earth x amount of years ago. Sending a regular ship is no good - by the time it reached it’s location the light from Earth of x years ago and come and gone.
Refusing to give up on my quack theory, I checked out good ol’ Wikipedia. What about using a wormhole or Alcubierre drive to allow the craft to reach point x?

Find some negative mass. Assuming it exists.

Considering we know of no way to make either of those methods work y ou still have an uphill battle. Even if they did what would you have? A distance so great that the sun is only a bright dot and you can’t even see the earth but only infer its existance because of wobbles in the sun’s location. You’ve determined that in the past the earth existed. Whee! If you go far enough to see before the earth existed you will likely be too far to even see the sun.

Thanks Mr. Kobayashi. This thread just made me realise how particles that travel faster than light, i.e tachyons, actually travel backwards through time. :smiley:

How about the nocturnal_tick Stellar Reflection Time Observing Principle[sup]TM[/SUP]

What if, theorically, you were able to find a perfectly reflective surface somewhere already out there, this body X would recieve light from the earth and reflect it back to us, giving us a picture of the earth way back when.
time to travel = T / years
(E)-----------------------------------(X)

        • : light transmitted

_ _ _ _: light reflected

=> Images of earth 2T years before.

Obviously you can’t have a perfectly reflective surface but every observable surface reflects somewhat, so all you would need to do was build telescopes that encompassed the earth and a giant supercomputer to organise which light came originally from the earth and Bob’s your uncle! One time machine television.
(C)
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(A)-----------------------(E)-----------------------(B)
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(D)

Yes, that would work: if we stationed a big ol’ mirror at Alpha Centauri, 4.3 light years away, then we would see the Earth as it was 8.6 years ago. Of course, we could only see the Earth at that particular moment in time — it’s not “tunable”; and no matter how far away from Earth you send your BOM, you’ll never be able to observe a time before you actually launched the mirror. (Violations of the weak, strong, and dominant energy conditions excluded.)

It’s not exactly the same idea, but read the Isaac Asimov short story called, “The Dead Past.” It’s based on the idea nocturnal_tick mentioned about tachyons and viewing the past. I don’t want to spoil the plot twists, but it’s similar to what MikeS said about limited usefulness, i.e. the life of the tachyon particles.

There’s also the problem of the Earth’s relative movement to the mirror in the first place.

Thanks for the replies, I thought I’d get the “I’ll have whatever he’s drinking!” type of response.
Now off to NASA to sell my idea.
:wink:

This exact question was asked four years ago (wow, was it that long?). And to recap what I said in that thread, any method whatsoever that can get you from point A to point B before light could travel there through a vacuum can also be used to travel into the past. So not only would you be able to see history unfold, you’d be able to actively participate in it.

However, there is no method known to be possible which would allow you to get from point A to point B before light. All proposed methods require the use of substances with negative mass, which, so far as we know, seems to be impossible.

L Ron Hubbard sketches out such a scenario in Battlefield Earth.

Since I doubt anyone will ever bother to read that book, though it’s not as bad as the movie- which isn’t saying much, I’ll fill everyone in on how it went down.

The Evil Alien Menace has teleportation technology.
The Evil Alien Menace breathes the creatively identified “breathe gas” which reacts explosively when exposed to radiation.
The Self-Realized Protagonist sends a number of convenient nuclear weapons back through the teleporter and so vanquishes the Evil Alien Menace… or at least stops them from sending more Evil Aliens through the teleporter to be Menacing.

A couple years later, the Self-Realized Protagonist has deciphered the alien technology and brought humanity back from the post apocalyptic brink and into the interstellar age. Curious as to what his handiwork actually did, a probe is sent out to the space “a couple” lightyears away from the Evil Alien Homeworld, points a superwhamadyne telescope at the Evil Alien Homeworld and records the whole event as the light reflected from the planet at the moment the nuclear payload was delivered arrives at that point in space currently inhabited by the superwhamadyne telescope.

This was pretty much the only cool SciFi idea I remember from the book.

The Light of Other Days by Arthur C. Clarke and Stephen Baxter also plays with this concept, but this book is actually worth reading… so I’m not going to do a hack job synopsis on it.

Light is made of photons. So at some point your distant telescope is reduced to spotting individual photons that came from Earth. For that matter there is a finite amount of light reflected from the Earth. So for a telescope of any sub-astronomical size, your data rate drops to nearly zilch at interstellar distances.

But assuming there would be some kind of telescope that could see events across interplanetary distances, there could be something like this. We might receive a message (transmitted at light speed) from the inhabitants of Omicron 7, a planet orbiting a star 1000 light years away. They’ve got thousands of hours of tape from the days of Caesar and Christ and they’re anxious to sell them to us. Granted, it’ll be another 2000 years before we can send back our agreement and start receiving our transmissions.

Or, the Yeticus Rex Black Hole Gravitational Lensing Observing Principle[sup]TM[/sup] which incorporates a black hole to return the information 180 degrees by use of gravity. Since we have done about 80 years of radio, I wonder if we’re able to find mini-black holes within 40 light years of earth this way and hear echoes of our past…

While this is the accepted hypothesis, we can’t yet confirm it and hence cannot rule out the possibility of FTL phenomena.

This would be harder, because you would only recieve a small proportion of what was originally sent out. Not only would a majority just be “sucked” into the black hole but most of what remains what either be caught in orbit or be thrown off at angles that are not suitable. It would be easier for photons to do a “fly-by” and come off at oblique angles than manage to go round the black hole and return to us.

True, but it is actually seriously considered. I’ve seen papers proposing finding solitary black holes by looking for faint points of light with the Sun’s exact spectrum. On the plus side, a black hole “reflector” wouldn’t change the spectrum of the light at all, like reflection off of any material would. But I don’t think that it would be possible to recover images in this manner, since orbits in the vicinity of black holes tend to be chaotic.