Where does the light go when you turn off its source?

@cheesegreater@lemmy.world !asklemmy@lemmy.world

In order to understand what happens with the light from our earthly shelters, one needs to look up. See those stars shining all across the night sky? Those celestial bodies aren't where we see them, and many of them are long gone. So we don't see the stars, we see their "ghosts", compelled to physically wander through the spacetime continuum.

Roughly speaking, EM radiation (and, by extension, visible light) travels indefinitely to the far reaches of cosmos once it's emitted. It'll definitely decay and become fainter and fainter (Inverse Square Law), eventually blending with other faint signals also scattered and wandering through the space. We call it "noise", which is nothing but the sum of all cosmic EM activity that once happened since the dawn of time, especially (but not limited to) that of Big Bang, as "Cosmic Microwave Background", which is still around (it's just that our home equipment, as digital sets, are designed to ignore such noise, but people used to be able to tune into it with the early analog TV and radio receptors).

Now, there's a maxim from Hermeticism that says "As above, so below": just as we see the past from cosmos whenever we look at the skies, some hypotethical extraterrestrial civilization at hundreds of thousands of light-years from here would see (supposing they exist and supposing that they got highly advanced optics) a Pale Blue Dot with some minuscule flame spots on its surface, the bonfires once lit by Homo erectus when they began tinkering with fire. Those extraterrestrials won't see the Earth as it currently is relative to the Sun, which also won't be where it currently is relative to Milky Way, which also won't be where it currently is relative to Laniakea.

Those extraterrestrials definitely won't see our desperate signals begging for them to beam us up (from the former Arecibo transmission all the way to someone lonely blinking their home lights right now desperately trying to call the extraterrestrial attention): we're all screaming to the void, and the void screams back as a silent noise from long-gone celestial bodies. The cosmos is a big cemetery where ghosts are hauntingly compelled to roam around without getting anywhere (still they sometimes stumble upon other ghosts, when energy is absorbed by all sorts of cosmic matter both here and out there).

In the end, this is what happens with your home light every time you turn it off: it becomes some kind of "electromagnetic ghost" electrically "summoned" in your room and unleashed to the outer space, not to haunt, but to be haunted and devoured by the ineffable darkness of the abyss, where it will spend the eternity going everywhere to reach nowhere...