The reason is, the Universe becomes transparent to optical light at times between 500-to-700 million years of age, with the most distant known galaxy existing in a rare “pocket” where the Universe is transparent at only 400 million years old. But various estimates for the time of formation of the very first stars, at redshifts of 20, 30 and 50, correspond to ages of the Universe of 177 million, 98 million and 46 million years, respectively. Even if the Universe were transparent to begin with, the wavelengths of light we’d look for — that strong Lyman-α emission line at 121.567 nanometers (UV light) — will be redshifted to wavelengths of 2,553 nm, 3,769 nm or 6,200 nm, depending on how early these stars formed.
Ethan Siegel — Why Hubble Will Never see the First Stars
Image by Eurritimia 
Whenever I read about the latest thing Astronomers have seen, I have to do a little mental reminder that they are really looking back in time, and what we see is quite possibly no longer there.
In Larry Niven’s Ringworld, there is a subplot that the center of the Milky Way has exploded and it’s a growing concern, but not terribly so, because the shock wave from the explosion that will wipe everything out will take 25,000 years to reach known space.Report
no longer there
Whatever that means, relativistically speaking 🙂Report
And now, for something completely different (but very similar)
Dogs, and other animals with a highly developed olfactory sense, “see” (smell) the world differently than us. They can “see” backwards in time to what was there before, and not just what it’s there now, and can “see” al their surrounds at the same time.
Every once in a while I think this could be great material to write a story truly from a dog’s POV, in which the dog relies more on smell and sound to explain his world and his actions
(famous New Yorker cartoon: one dog to another, who looks a bit cross with the first: “It doesn’t matter he’s a jerk, of course I smelled his ass. It’s the polite thing to do”)
And re Ringworld, the wave is actually an important thingReport
wow. an actually funny new yorker cartoon. whoda thunk?Report
Duh.Report
(((I just want to say this comment made my day.)))Report
I took the liberty of fixing the HTML for the spacial characters.Report
I’m much obliged.Report