Paradox or Not?

Id go with Hubble, far less distortion to correct, no atmoshere to mess things up

Would it mean the demise of history books if we did?

No, you will be seeing a past in your own life, since you will be present at the time the image starts its journey.

History would be what had happened before your time. Since the mirror was placed by the same person watching the return image, it's hardly history.

Deleted post...

Theoretically the concept is sound, but the realization, not....

Why is that a paradox? It would take light 10 years to make the round trip. However, there are a huge number of practical problems with this. Even given perfect optics, the resolving power of a telescope is limited by the diffraction limit. To see anything useful would require an immense size telescope and an immense size mirror.

NO. You would see 5 years into the past 10 years later.

Its logic, isn't it?

No its a Paradox!

The image viewed from Earth would be of a five year old mirror and its additional five year old image of Earth. Thus we could see ten years into the past. I think there is little bit of a paradox with this thought experiment.

With the continuing expansion of the universe, one can look into a distant mirror back into the past precisely ten years only once with the same mirror.

No. You are seeing a 5 yo image 10 years later.

Warp speed doesn't exist yet.

Neither do miracles.

Dàmn. I hate it when I'm wrong.

More than once.

I'm on my phone, or I'd grovel more.

's ok...

I'm getting old, too.

Lyn is actually incorrect, the data returned from the mirror is five years old at the point of reflection, but it takes an additional five years for the data to be received back at earth. The data is received at earth ten years after being transmitted.

I never thought that the added space with only five light years of distance would be easy to measure but with this being a thought experiment I assumed flawless, absolute measurements could also be assumed. I also assumed the expansion of space effect in this thought experiment would be like the movement of the Moon away from Earth but even more extreme.

That's what I thought too. It just seemed too fun to be true. Think of the forensic possibilities... My failing memory wouldn't be so much of a bother.

We wouldn't need propulsion except during the initial deployment of the mirror. Earth/Sun is traveling through space (relative to an appropriate origin) in a roughly straight line. For practical terms - we're all about practicality here - an initial vector should suffice. Many years later, the different orbits around the center of the galaxy would diverge the mirror & viewer.

I think we could pick a galactic orbit for the mirror that would hold the distance constant for a very long time.

The mirror would require energy to maintain alignment though.

What is so bluddy annoying about such mirrors is that, when I go to comb my hair it isn't there.

That's because you're standing too close to the mirror...... try backing up about a dozen light years.

The apparent paradox would be to see yourself on the way to deliver the message and coming back at the same time, except that won't happen either because it would be against the restraints of physics, sounded good though.

I'm rolling in the floor here guys!! Thanks for making a bad night bearable. Lyn thanks for the humility that few people will show.

Well, the two guys who correctly set me straight are very intelligent.

It's hard not be be humble in the presence of such big brains.

I may sometime need what you were having that night. :-)

Only reason I come here is as an antidote to the Internet. Real talk about real stuff by real thinkers. Not that it's peerfect (sic). -0-

Rationally.

It takes 5 years to reach the installation point, and 5 to return.(10 yr round-trip)

Upon our return, light that had left Earth 5 years before, is just reaching the mirror, but

it takes another 5 years for that image to return, in order to be observed from Earth.

Yup,10 years into the past of for an observer who had remained on Earth throughout.;

But somebody has to travel there to hold the mirror!

Isn't it a nice thought experiment? What happens to the actual picture? Will it age the same way as it needs time to get forth and back or will there be a time dilatation?

What about the guy holding the mirror?

Common sense says the guy holding the mirror must do so from behind, in order not to interfere with the reflected image. Therefore, he doesn't see any image at all. He just gets 10 years older, holding the mirror.

Will that be years that went on Earth or years that went for the beholder in relation to the Earth years?

Just to complete your remark. The guy who should hold the mirror, doesn't have to be there a long time. He leaves the Earth one month earlier (or two , or only two weeks), then holds the mirror for your image to bounce on it, after that, he can leave. Now, we can discuss the speed at which he must travel....According to Albert, he cannot travel faster than Mach1 (sorry, c) so that would be his journey, some ten years.

A light year is the distance light travels in 1 year, so your mirror is 5 "years" away.

The image would be traveling for 5 years to reach the mirror, thereafter another 5 years for it to return, you would then be seeing the image after 10 years.

I think the answer is yes.

It is just one's Perception...

Cheers!

A less probable scenario (if that's possible), but the same principle:

If through our telescope, we miraculously see a mirror 5 light years away placed by an unknown benefactor (at least 5 years ago), the image we would see in the mirror would be of earth 10 years ago.

Seems like a lot of trouble to place a mirror so you look ten years younger!

You could slow light down and you wouldn't need the mirror so far away!

http://en.wikipedia.org/wiki/Slow_light

Cheaper to simply take a picture and wait 10 years to develop it.

... Or develop it and just not look at it.

Obviously, yes...

It's not a paradox at all. If we assume that, right now, a mirror is installed on a distant planet, 5 light-years away, we'll have to wait 5 years just to see the mirror itself. However, we'll see no image of the Earth on that mirror. We'll have to wait another 5 years (i.e. overall 10 years) in order the photons -which leave the Earth right now- to go there, reflect on the mirror and come back to us. So, we'll have to wait 10 years in order to see ourselves on the mirror, as we are right now.

When were you going to install that mirror, just before the Earth's creation?

Given the Earth is 4.5 billion years old already, the moment you erect that mirror you will have photons striking that mirror that left Earth 5 years prior.

So, unless you have a time machine, too, and go back 4.5+ billion years, there will be reflected and emitted photons from Earth striking that mirror from the moment it is installed.

"... there will be reflected and emitted photons from Earth striking that mirror from the moment it is installed." That's right. We can't see -on that mirror- any event that happened before its instalation. That's why I said that we have to wait 10 years in order to see the first image of ourselves (as we are right now).

Nope. Think about it. Photons are already arriving from Earth at the instant the mirror goes into operation, so in 5 years we start getting the first photons back.

It just so happens that the photons were already 5 years old when they hit the new mirror, so the data is still 10 years stale.

Yes, you are right. My mistake was that I didn't take into account that photons have already been transmitted from Earth 5 years before the instalation of the mirror. And these will be the first photons which will be reflected and travel back to us. So, in 5 years we'll see these photons, i.e. we'll see the Earth as it was 5 years before the instalation of the mirror. And in 10 years we'll see the Earth as it is now.

this is a corollary experiment: suppose you could discover a way to bounce tranmitted, encoded signals from the surface of the sun (or any other star with similar properties), and further suppose that any distortion of the signal could be corrected by an algorithm that averaged the signal over time or some such scheme (data smoothing?). Now we know it would take the signal something like 17 minutes for a round trip to sol, so that would not be so interesting.

Suppose we sent messages to stars at various depths of space, within the galaxy. Presuming our signal return is even detectable at 1, 5, 10, and 100 light years (or even more), we would have a "message in a bottle" for later generations to read at some point, so how useful could that possibly be? It presumes we don't wipe ourselves off the planet, and that we can still detect the signal 2, 10, 20, or 200 years from now (or even longer), and that having detected this signal, we could still interpret the encoded data. It would possibly help the observer if the encoding started with a binary sequence that repeated for up to a month, 1,0,1,0, ... then progressed thru the bits up to the length of a word (32 bit?), then the remaining message could be the binary code for images, sounds, words, etc.

We already have that. It is called the NSA archives.

Everything we've ever broadcast into space is such a message in a bottle, just as we observe distant objects as they once were, not as they are.

Observers of Earth more than 150 light-years away have only "passive" emissions to observe: they can see whatever the Sun illuminated. We didn't actively start transmitting data to the universe until the first radio.

To someone on the other side of the universe, the Earth doesn't exist... yet.

Once we develop the ability to warp space, we can go out in advance of our electronic signals and reference them at leisure.

What if you position a second mirror on earth, focus it at the first mirror, (ignore the loses/degradation), so that it reflects the reflection from the first mirror, back to the first mirror.

Would it produce a Droste effect?

Now that's a paradox.

and like the reflection, or 8-track tape ............I'll get back to you.....

So if you play the 8-track tape backwards, do you...wait for it... go "Back to the Future"? Oh snap, that was meant for the thread on stainless steel auto bodies, where we were discussing various mods of the DeLorean.

On a lighter note, can the Droste effect be done well with convex mirrors, or concave ones? What about carnival distortion mirrors?

"So if you play the 8-track tape backwards, do you..."

If it's an 8-track Country music tape, the lucky sod gets un-run-over by a train, goes to prison, gets out, gets his truck back, gets his dog back, gets his wife back, falls out of love at 10 PM and, finally, sobers up at 3.