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Comment by TaurenHunter | Hacker News Reader

It would be nice if photons from the past could be captured to take pictures of millennia ago.

If you could use a wormhole to travel 50 million light years away from earth instantly, then look back at earth with a sufficiently powerful microscope, I believe you could observe the dinosaurs.

50 million light years would not get you light from 65+ million years ago.

Imagine seeing the exact point in time the asteroid hit!

There is this sci-fi book about this, but I forgot name/author. In the book a wormhole end can be positioned anywhere in space and time history. The tech starts as an ITER-like project and then becomes available in mainstream products, and all the dirty secrets of mankind come to light.

That is Arthur C Clark's last novel "The Light of Other Days", and it even has an Elon Musk like no ethics billionaire as one of the plot driving main characters.

Thank you! Yes, that is the one. I actually found it on my bookshelf just now, but in searching for "that book with the wormholes" several times before I never thought to check this one. Great sci-fi story.

Asimov has written a somewhat similar novel called "The Dead Past". In fact from the description I thought parent was referring to this story.

The photons would be so spread out that you'd need a telescope with a primary optic bigger than anything else in the universe. And even then, you'd struggle to capture enough to have any meaningful information.

You don't even need a wormhole. Light can "reflect" (ok more like slingshot) around a blackhole 25 million light years away, giving us a direct visual path to our own planet 50 millions years ago.

Of course our telescopes don't have anywhere near the resolution for this right now.

Will they ever? Surely at some point there just wasn't enough light reflected off of dinosaurs skin to reconstruct anything more than scattered dots of light.

Theoretically you'd just need an enormous telescope to collect enough light to resolve an image. Though based on the features that modern telescopes can resolve on the moon ~1 light second away, it'd probably need a telescope on the scale of a galaxy

At some point there might be it be enough photons, though, right?

Nope! We can detect individual photons (and measure their properties) and a mirror can (nearly) perfectly focus and collect every photon that hits it. The frequency of detection events would change with the distance, but the frequency doesn't hugely matter, one photon per week is enough for science!

It is definitely possible that I’m missing something here.

But, for example, if we are trying to get an image of a dinosaur, and we’re only getting one photon per week, how’s that work? The dinosaur should have moved before the second photon is sent off, right?

You're totally right, it's me that's missing something. If you had something that moved predictably, say a whole planet, you might be able to get results by accumulating over a long period of time, but single photons would not be useful for imaging a dinosaur.

Scattered dots of light can tell us a lot! If you find a photon of a frequency that's only produced by, say, a CO2 molecule, you can prove that CO2 existed 50 million years ago. Ok wow, probably not too useful. Collect a bunch of photons, count how many indicate CO2 and how many indicate O2, and you can figure out the composition of Earth's atmosphere. All of this using single photon detections!

This would be a very expensive way to get a very noisy copy of data that we can more easily extract from the geological record.

In other words: it's awesome, and we should totally do it.

I hope this is a sarcastic post about telescopes :)

It "can" be done. Some photons leaving the earth a thousand years ago. Bouncing off a mirror in some distant planet and allowing us to see two thousand years into the past

Just imagine of all the plants that have absorbed photons…the memories would be corrupted…though photons do dispersed isotropically…

I'd personally appreciate it very much if photons from the future could be captured to take pictures from week and years ahead. Could be used to help with those awkward tasks like choosing the correct lottery numbers, choosing the correct stocks, choosing the horse that's definitely going to win, etc.

If you can't get photons from the future, just get a hold of some thiotimoline, a compound invented by SF master Isaac Asimov that dissolves slightly before it is added to water. After first describing it in a spoof chemistry paper, he returned to it several times, exploring its different applications and the new scientific field it created, "chronochemistry".

The best IMHO is "Thiotimoline and the Space Age" from 1960. You can read it on archive.org: https://archive.org/details/MerrilEdTheYearsBestSF05/Merril_...

All photons you see are "from the past". Photons moving backwards in time would let you see _the future_.

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