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Comment by william42 | Hacker News Reader

Considering the lightyears involved, I assume this means we'll see it in 2013?

That's correct. But never forget the idea of a "now" is deeply tied to a "here".

Implying whatever happened so many thousand years ago will have an impact here at about the same time we observe it happening from here? (I.e. light coming from that time and direction arrives here at about the same time as whatever implication this has to us does.)

If so, what kinds of implications would this have to us? Is this quasar radiation merely an observable thing, or could it disturb communications or something along those lines?

Edit: no doomsday paranoia implied. :-)

I think that’s the implication, but it goes even further than you say: because of the relativity of simultaneity (see Wikipedia), there is no absolute yardstick of the timeline.

In other words, “it happened n years ago”, like “it’s happening right now”, isn’t defined by itself; it only makes sense for given values of here and there.

This comes out of special relativity and is closely connected with the fact that nothing, not even photons, can move faster than a certain speed.

It's interesting — this both appeals to my intuition and is hard for me to completely wrap my head around... I can see it but I realise that I don't naturally think like that.

Essentially, it's meaningless to say that two things are absolutely happening at the same time in different places. There is no such thing as "meanwhile, somewhere else". Or at best, it's a very limited model.

When we observe the light from an event is when it actually happens, from our perspective, for all intents and purposes. Kinda screws up our whole way of thinking, but this is how the universe actually works.

Was thinking the same thing. Depending on how you think about space-time it "is" happening 27,000 years go.

http://en.wikipedia.org/wiki/Milky_Way#Galactic_Center

Or rather, it is happening now 27k light-years away.

Presumably, yes. It would be odd for the astronomers to use two different temporal points of reference; time of observation is the only time that matters. Plus, any excitement on the part of astronomers would be super pointless if they had to wait another 24824 years to observe it.

From the point of view of a photon originating in that gas cloud, it was emitted by an electron in the gas cloud and absorbed by an electron in the telescope sensor at the exact same instant.

On the other hand it would be impressive if they correctly predicted it from 24-millenia-old data.

Think of it as the "egocentric" rule of astronomy: always describe things from the perspective of the observer (you), not from the perspective of the agent.

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