[lefrenchy]

It's just so crazy to me to see a galaxy 420 million light years away. That is so much time for what we're seeing to have changed. I presume life can form within that window given the right conditions, so to some degree it just feels a bit sad that the distance is so great that we can't actually see what may exist in this moment that far away

[gary_0]

Given that the speed of light is the speed of causality, technically it's not really 420 million years in the "past" in any meaningful sense. The present is relative, not universal. The collected light we see in our telescopes is a lie about a particular universe that will never be, at least in any tangible way. On a cosmic scale, every spot in the universe sees its own unique sequence of events going on around it, all of it rendered virtually immutable by the relative slowness of c.

It's a beautiful nightmare, isn't it?

https://en.wikipedia.org/wiki/Relativity_of_simultaneity

[codethief]

> Given that the speed of light is the speed of causality, technically it's not really 420 million years in the "past" in any meaningful sense.

Yes, it is. It is 420 million years in the past in our frame of reference. The link you posted is about how frames of reference of other observers might differ from ours. However, doesn't make the notion "420 million years in the past [in our frame of reference]" any less well-defined.

[conductr]

I’ll admit I’m severely undereducated in this stuff, probably less than an average high schooler these day but nevertheless I feel like I’ve considered this before and never knew it had a name. Which makes me feel not completely stupid.

> whether two spatially separated events occur at the same time – is not absolute, but depends on the observer's reference frame.

But What I don’t understand about this is why is “time” framed as observer based? In my mind, the events do happen at the same time and just are unable to be observed as such. I feel like time is a figment of our imagination, it’s just a measurement. In my pea brain time makes sense more as a constant and the other things are something else that impacts the latency of observance

[nullwriter]

Absolutely mind blowing - I've not thought of this and will be reading about it

[0xDEAFBEAD]

It might be possible to build a powerful telescope to see life on planets that are closer to us, though: https://www.palladiummag.com/2024/10/18/its-time-to-build-th...

[Tepix]

Or go for the gravitational lens provided by our sun (580 AU out).

[Sander_Marechal]

Ohh I love the idea of a massive telescope that's just compromised of thousands of individual satellites!

[vasco]

In another way it's really cool to be able to "see the past" even if all we see is always the past. At this level it is like a super power. If only some aliens had put a mirror somewhere far so we could see ourselves too. Or multiple mirrors at different distances.

With enough mirrors and light bouncing around the size of the universe itself can be a "storage media" of the past with different photons all around carrying "how this location looked X years ago". "All" you have to do to know what happened is find the right photon to see whatever it is you want to see.

[ujikoluk]

For prior art in this field, see:

https://github.com/yarrick/pingfs

"pingfs is a filesystem where the data is stored only in the Internet itself, as ICMP Echo packets (pings) travelling from you to remote servers and back again."

Also https://en.wikipedia.org/wiki/Delay-line_memory

Storing data as acoustic waves gave a higher capacity in practice, as propagation is slower thus fitting a larger number of symbol per time unit.

[ConcernedCoder]

In theory, couldn't we focus on a perfect spot near a black hole where the light has been warped 180 degrees around it... i.e. if the black hole is 100 light years away, you'd see ( with perfect zoom, of course ) a picture of the earth 200 years ago...?

I understand that we'd have to account for the movement of objects, of course, but with computers, seems like a small hurdle...

[grahamj]

You don't need mirrors, you just need to get in front of the photons. A time machine or warp drive will do :)

Also the past is the only thing you can perceive, there effectively is no now.

[steveoscaro]

Well that sounds like a good premise for a scifi book or movie.