Theoretical question: if spectrography advanced to the point that we could see individual organisms and their behavior from lightyears away, and then we placed a very large mirror very far away from our planet, could we aim a telescope at that mirror and watch ourselves going about our lives in the past? Could we use this technology to solve crimes, answer historical questions, see dinosaurs, etc?
Yes! Problem being that if we launched the mirror a light-year away, it would take more than a year to get there, and once we got the telescope set up, it would only show us a year in the (relatively speaking) past. Send it a million light years away, it would take more than a million years to get there, and our million-year-distant descendents would only see a million years in their past. So we wouldn't see into our past... it would be cheaper to just launch a camera into space with a long buffer of tape.
However, black holes are known to curve space-time and I've often wondered if we could find a sequence of black holes in a configuration that would bend the earth's light back on itself... theory being that if we had good enough resolution we might actually be able to see our deep past. I have no optimism that we could resolve organisms though -- just finding the sun, and seeing what it looked like in the past would be an incredible feat.
We should pop up a mirror facing away from Earth as a service for anyone who wants to look at their past. Hopefully someone else did that for us, just need to find it.
This is kind of a fascinating idea - wouldn’t it be kind of an amazing “public service” to just deploy a large reflective perfect sphere into space at the galactic restful reference frame?
Now that I look more closely it was an April Fools joke. Whoops.
See the small note at the end:
> I just realized that this story was hosted on a blogger’s site, not the Beeb… and it was loaded on Wednesday, 1 April 2009… well done. You got me over two years later.
I'm not sure where I've seen this described, but apparently a single black hole already reflects light back toward the observer, through a series of concentric rings, where each inner ring reflects light that has gone one more time around the black hole
> Photons that make a single U-turn around a black hole and then zip toward Earth would appear to us as a single ring of light. Photons that make two U-turns around the hole appear as a fainter, thinner subring within the first ring. And photons that make three U-turns appear as a subring within that subring, and so on, creating nested rings, each fainter and thinner than the last.
> Light from the inner subrings has made more orbits and was therefore captured before the light from outer subrings, resulting in a series of time-delayed snapshots of the surrounding universe. “Together, the set of subrings are akin to the frames of a movie, capturing the history of the visible universe as seen from the black hole,”
It does... but I'm guessing those rings of navelgazing, as it were, would be infinitesimally thin. Further out, there is less distortion and perhaps a hope of figuring out what one is looking at.
Edit: a ring??? Mind blown. I guess it makes sense, the light doesn't have a preferred direction to travel around the hole... still, that's wild. It's like how photoreflectors throw light back where they came, but instead of internal reflections of a sphere... yup, mind blown
Stated more succinctly: Any mirror we launch couldn't catch up with any light emitted from before the mirror launched. So we couldn't see our past that way.
We could do it only with a reflector/bender that already existed in the light cone future from when the light was emitted.
You might get better resolution than you think. Using the sun as a gravitational lens you could image the exoplanets at alpha centuri with meter resolution.
If you're using a black hole as the lens then you might be able to image organisms at sub millimetre resolution from thousands of light years away.
I don't think it's possible. R squared pretty much means that no light from an individual organism will ever reach you. The number of photons reflected from a planet is a staggeringly large number, but the distances involved mean that the faction that actually hit your spectrograph are so incredibly tiny that its impossible to tell what they are from.
Now, that's just in one way travel. In two way reflected travel it gets even worse. Only some tiny fraction of our light will hit the mirror due to R2. There is no such thing as a perfect mirror so only a tiny percent of the tiny percent will be reflected back.
Distances in space are stupid. Our minds cannot comprehend them.
Only if you had the ability to outrun a photon that has been traveling for 65,000,000 years, park, set up camp, and build a mirror. But then, if you can do that why are you building a mirror?
What if you could avoid the travel? Perhaps some chance alignment of distant black holes creating something like a gravitational mirror? Bend the light, bend it some more, bend it so it reaches earth today. A 65 million light year round trip.
Or we have discovered aliens have already done this for us, perhaps to amuse themselves at the chaos that will ensue once we figure out what it is we're looking at and what it means for all of our civil, social, and religious institutions.
Theoretically yes, but you would need a very large telescope to resolve individual organisms at the distance of one or more light years. The Rayleigh criterion gives us a minimum diameter of 1.22 * wavelength / angle, and the angle to resolve 1 meter at 1 ly is approximately 1.06e-16 radians. So for 508 nm visible (sun)light the minimum diameter would be ~5.86e9 meters (or a little more than 919 Earth radii) per light year.
Since this is a theoretical question, I can theorize an actual possibility for such effect - bending of light by massive objects which results in actually observed gravitational lensing (focusing of light from distant object by front objects). If just by pure coincident galaxy clusters (the most massive objects we know) happen to be located just right, light from Earth can bend enough to point back on us. Those clusters are far enough though that we can then "see" on the time scales of Earth forming, so getting to any historical questions or even dinosaurs would actually take some waiting.
It's so cool how far we've come with exoplanet discovery in such a short time! The first one was only in 1992 and it's so neat seeing us go from only picking up giants to being able to detect smaller and smaller planets. Now to get chemistry from a rocky planet?! Awesome.
1992 was 30 years ago. You should probably add for a project with limited military potential. The time between Sputnik's launch and the first manned Moon landings was only 12 years, but there you had the military component. Of course it's still amazing progress and there is a lot of engineering involved in it. I'm definitely a fan.
It's like they're different worlds. Ever since humanity broke out of the "just being a subsistence farmer or serf like my parents" loop a hell of a lot happens in 30yr.
I remember when I talked to my parents and others telling them it's obvious exoplanets exist - since our Sun is a star and there are many stars, it seemed logical that at least some of them do have their planets. They would laugh and say, "Yes, it's not impossible, but for now it's just science-fiction."
Again, since life developed on our planet, it seems logical that it also exists at some of the exoplanets. We are just lacking an efficient method of communicating with them.
Yes, of course. It must be life is present in other places because of the vast number of suns with planets. We are starting to see that planets are forming around stars in some ways similar to us, other ways different (it's hard to see earth like planets bc of limits of our technology). We already know rocks can get ejected from one planet in our own solar system, and thus have certainly the possibility to spread small bits of dna from earth to mars (and it could go the other way). We have seen the 4 dna bases (plus the one that is different is rna) in space. We have the extremely suggestive but not certain possibility that methane detected on mars is coming from biological processes. There is certainty on life in the universe elsewhere - at least microbial but I think it's certain that higher level life forms are there.
We don't know nearly as much about advanced life, like say animals, plants over bacteria, much less intelligent life. But the universe is so huge, I think it's likely there are other places with intelligent life.
Maybe. Or maybe we're not special only in the sense that every place is special. Is any one particlar day special? No. Has any day ever been duplicated? Never.
The default assumption should be that the solar system is typical and that would lead to numerous earth-like planets in the galaxy and that would give hope to a lot of (intelligent) life. But untiol a few years ago, this was just a very plausible explanation. Since then we have confirmed thousands of planets. So while there are still a lot of unknowns for a good prediction, the planet count is at least consistant with the assumption, that solar-like systems are not an exception.
If you accept the possibility of the multiverse as a "solution" to why the laws of the universe allow for life to develop in the first place (in quotes as it's not really a solution as it can never be proven), then it seems to me there is no reason to think that intelligent life can't be so rare that only in 1% of all universes that can support intelligent life, intelligent life actually develops.
Interesting choice for the first Webb exoplanet at 41 light years distance. There are 11 stars within 10 light years of us. Does their choice mean that none of the closer stars have systems that are edge-on to us?
You not only need a system that has exoplanet transiting its star, you also need to have it happen at right time (it happens at most once per exopelanet's orbit) and also at right time for Webb to look at (remember, it is severely restricted in where it can point).
Potentially, wouldn't star systems have planets where their orbital planes are at positions that we cannot observe transit event from? In fact, most planets?
"Anything more than 85° from the Sun as viewed from L2, which includes Mars, Jupiter, Saturn, their satellites, the asteroid belt, and all outer Solar System objects. JWST also can't look farther from the Sun than 135° (i.e. within 45° of the anti-sun position) but outer solar system objects will all be observable some of the time. The field of regard limitations are a fundamental consequence of the observatory thermal design and the sunshield design that keeps the telescope and instruments cold. This means that the Sun, Earth, Moon, Mercury, and Venus, and of course sun-grazing comets and many known NEOs cannot be observed."
Not really? From what I read temperature there is few hundred degrees higher than here.
Unless it's tidally locked "eyeball world" then probably not too livable.
Given how much energy can be present inside planets and how water can persist underground so long as there is a stable water cycle in the atmosphere and planetary surface, I have a feeling that (similar to earth) tons of life would be possible in the dark, feeding off of geological outputs. This kind of scenario seems like a potential hotspot for sources of life. Maybe not intelligent, but I’d be elated if we found it.
Water is just an example here — who knows what’s possible.
