this post was submitted on 28 Oct 2025
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But only after 10 years. You couldn't see anything that wasn't visible from the viewpoint of the mirror beforehand, as from earth's point of view the mirror isn't there yet. And if you're there anyway… you can just look at Earth with the craft that's on the position of the mirror already.
That's why we need to find a natural mirror somewhere already out there, so we can see into our past. Something like a planet made of pure mercury, or an arrangement of blackholes doing gravitational lensing that bends our light back to us, or whatever. We'd also need instruments vastly superior than what we currently have in order to get any useful information out of seeing our own light bounced back to us from so far away
... But still! the idea that it's at least hypothetically possible to actually see our own past is very exciting!
Just look in any mirror. What you see is also you in the past.
“‘That’s a picture of me when I was younger.’ Yeah, no shit. Every picture of you is a picture of you when you were younger.”
-Mitch Hedberg
He didn't curse in that line. In fact he didn't curse much generally. I don't have any objection to curse words, it just doesn't sound like his voice when you add curse words in.
Fuck shit ass titties. I just had to get that out after talking about not cursing
Fuck shit ass tities right back at you.
He did on the record.
True true. Heck it takes some 100-150ms for your brain to register what your eyes have seen.
I tried to point this out and everyone got grumpy. It must be nice being so attractive.
So you are saying, I always looking younger in the mirror?
I'm assuming the inverse square law would hinder us from seeing anything useful. But now I'm imagining scientists being ecstatic about discovering a foreign signal, only to realise its us from the past
That's highly unlikely basically because of the inverse square law. Even tightly focused beams dissipate quite effectively over light-hours, let alone light years. We'd be lucky to catch a single photon from our past selves over any significant distance.
For reference, look up how weak the signal is even just coming back from the moon when people try to hit the retroreflectors with lasers. Or how crazy weak the signals are when they reach Voyager.
We... we have tools for seeing our past. We have extensive records of imagery from as far back as we have orbital satellites. You can go on Google Earth right now and look at older maps.
I mean, I get why it would be cool to see a reflection from the past, but literally every reflection you see is from the past. At a certain distance from your reflective or distorting surface, you're going to need major image processing to make out a clear image of the planet, so again, at that point it's far easier to just look at recorded images or videos.
There is a much cooler idea though that you can exploit from this principle: you can use a star or other dense object in space to work like a light-lens, we could build this now but it would be a very expensive and long-term project, because we would need to send a series probes out past the distance that Voyager 1 has already traveled over 40 years. We would also need to know ahead of time what our target is so we place the probes in the right place, placing the sun between the probes and the target at just the right distance.
If you take the distorted light from around the edges of the Sun and reconstruct it, you can theoretically see details of continents and other surface features of Earth-sized planets in entire other solar systems, which would be fantastic.
You're missing the idea of why this is cool. Recorded images only go back a couple hundred years
Hey, don't you bring logic in here!
Only after 20 years. Light will take 10y to make it from earth to the mirror, and 10y to travel back.
No, the light would be reflected as soon as the mirror is set up. If the mirror is set up 10 lightyears away it would take 10 years for you to see it and whatever it reflects. There already is light on the way to the position of the mirror before you set it up.
Oops, that's right!
it takes way more than 10 years to ship a mirror from Earth to some place 10 ly away from earth.
None of these sound like deal breakers to this great idea