eli5-how do we know for sure how big space is? and how do we know we are right about everything we know in space?
In: Planetary Science
From measurements and calculations.
The speed of light we can verify in labs and all over. The composition of stars.from spectrometry and the light they give off. The color of what stuff burns. The way that space expands and how the stars all fade off into infrared. From parallaxing telescope data at opposites sides of the year and seeing how things shift. From our knowledge of atoms and how they form. To calculations on how fast they can happen.
Science is a massive web of observations that fit with each other. All it really takes is one thing not fitting in which shows us that we are getting something wrong, at least a little. Before Newton, people weren’t entirely wrong when they said “thing fall down”. But Newton was less wrong when he figured out the planet also falls up to meet you. Just a little.
And we are wrong about something. Don’t let anyone fool you into thinking we’ve got this all figured out. Dark matter and dark energy and just why space expands are big ‘ol question marks where something doesn’t fit and we haven’t discovered it yet. Of the bits we know, we are very solidly positive that things fall down.
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