Every observation out into deep space is also a look back in time.
Whenever you observe an object, you aren’t viewing it in its present state.
Instead, we’re held back while light travels through space.
Visible artificial satellites appear as they were ~1–2 milliseconds ago.
The farthest naked eye Solar System object, Uranus, is 2 hours and 40 minutes in the past.
The closest stars, in Alpha Centauri’s system, are ~4.3 light-years away; there, it’s early 2016 on Earth.
The second brightest star, Canopus, sees a pre-Industrial Revolution Earth: 310 light-years distant.
Deneb, anchoring the Summer Triangle, appears as it did 2,615 years ago; Athenian Democracy is a century away.
Eta Carinae, 7,500 light-years away, witnesses the Black Sea’s flooding.
The oldest naked-eye starlight arrives from V762 Cassiopeiae, 16,300 years old: when humans first entered North America.
Numerous visible globular star clusters are farther, with Messier 3 the most distant.
It’s 33,900 light-years away, corresponding to the final demise of Earth’s Neanderthals.
Galaxies outdistance all other visible objects.
The Triangulum galaxy even bests Andromeda: 2.73 million light-years away, predating Homo Habilis.
Only temporary, transient events are farther.
Gamma-ray burst GRB 080319B was visible for ~30 seconds on March 19, 2008.
7.5 billion light-years away, its light predates Earth’s existence by ~3 billion years.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
Starts With A Bang is written by Ethan Siegel, Ph.D., author of Beyond The Galaxy, and Treknology: The Science of Star Trek from Tricorders to Warp Drive.