That's what always freaks me out about astronomy. We don't know what Sagittarius A is up to at the moment. We will know in 26400 years.
Ironically, HN seems to be confused as to whether you made this comment 15 minutes or 1 hour ago, depending on whether I'm in "Add Comment" or the main thread. Different frames of reference, perhaps?
(edit: all comments are incorrectly marked as being 20 minutes old in the main thread) (edit2: and my comment is only visible to me, apparently. HN is broken.) (edit3: huge lag between edits and public visibility of said edits from a non-logged-in browser)
As the saying goes, "there are 2 great unsolved problems in computer science:, naming objects, cache invalidation, and off by one errors."
In case you haven't noticed, to reduce server pressure, a logged-in user sees comments in real time, but a guest only sees the cached version of the page that only updates slowly. When Hacker News sees an explosive amount of traffic, logging out is a way to help. The last time it happened was when Donald Trump was elected.
Doesn't it make more sense to freak out because we won't know in 26400 years? Or, for that matter, not even get to know what will happen in 100 years?
Some supermassive black holes have been caught briefly turning on, over timescales on the order of weeks-months. Tidal disruption events, where a star wanders too close to a SMBH, can result in luminous accretion with significant accretion rates (e.g., Figure 3 of [0]). As the material of the star falls into the SMBH or is blown away, the luminosity drops off, with a predicted decay of t^(-5/3).
[0] https://physicstoday.scitation.org/doi/full/10.1063/PT.3.238...
The same possibility holds true for gravitational waves, since they are unimpeded by matter as well. They even have the advantage of propagating at the speed of light, unlike neutrinos.
> For example, it can take thousands of years for the light produced by fusion in the Sun to reach the surface of the photosphere
This is not due to free travel of light through a transparent medium with a high index of refraction or due to gravity. Through a large part of the sun energy is transported by convection and even in the radiative zone photons get frequently absorbed and remitted, the mean free path is below 1cm.
‘Slowing’ down light by putting it in a reflective cylinder, water or fiber optic cable doesn’t change the nature of the universe or help achieve faster than light information exchange - it just means some photons are experiencing a traffic jam.