eli5: Prior to actual imagery from space, how did scientists know what distant objects looked like?


Was it I’m a math equation? Was it a wild guess?

In: 6

4 Answers

Anonymous 0 Comments

Telescopes and very talented sketch artist. But I guess the real question is what do you mean by distant objects?

Anonymous 0 Comments

There are very few things out there that we couldn’t see pretty well from Earth. Probes and space telescopes can give us tremendous detail, but we could already see all the planets, nebulae and galaxies using Earth-based telescopes.

Anonymous 0 Comments

Humans have had eyeballs since before science was science.

Our ancestors could see the sun and moon in the sky and also the stars – and they could also see some of the planets (Mercury, Venus, Mars, Saturn, Jupiter) but called them “wandering stars” because they seemed to follow strange paths in the sky compared to regular stars which were more or less stationary.

Eventually, folks invented glass lenses and telescopes and scientists finally got to take a better look at the “wandering stars” and see that they were actually just round orbs like the Moon. (And as telescopes got even better they also were able to see that some of those planets had tiny moons of their own, and that there were more planets like Neptune and Uranus.)

But, other than what we could see with our eyes and telescopes, nobody had any idea what kinds of distant objects might even exist.

Anonymous 0 Comments

They didn’t. When Galileo used the telescope to look at Jupiter it was a revelation. Specifically, he saw the ‘Galilean moons’ which look nothing like you expecting them to when you observe them for yourself. I can’t imagine what he thought but I am sure he said the Italian equivalent of “What the sh_t?”


Planets, which are Greek for ‘Wanderer’ defied expectations, observers didn’t know the difference between a star and a planet except that the planets obviously moved throughout the night.

Until powerful telescopes and astronomers like Hubble we knew practically nothing about the celestial environment. People had to be convinced about the scale of outer space, Anaxagoras spun in his grave. As an aside, Anaxagoras was a pre-Socratic philosopher known for saying that stars were huge balls of flaming rock that were small to us because they were really far away and that the Gods had nothing to do with them. He was laughed into obscurity.

That wasn’t that long ago, Hubble made convincing arguments in the 1920s, barely a century ago. Shoot, we didn’t know about dinosaurs until 1842. The US constitution pre-dates the discovery of Dinosaurs. The depth of ignorance about the natural world pre mid 19th century is stunning to a scientifically minded person of 2023. Someone with AP bio, AP chem, and AP Physics are given information that was beyond cutting edge a century ago.