“The experiments that we will do with the LHC [Large Hadron Collider] have been done billions of times by cosmic rays hitting the earth. … They’re being done continuously by cosmic rays hitting our astronomical bodies, like the moon, the sun, like Jupiter and so on and so forth. And the earth’s still here, the sun’s still here, the moon’s still here.” -John Ellis
Relativity, or the idea that space and time are not absolute, was one of the most revolutionary and counterintuitive scientific theories to come out of the 20th century. It was also one of the most disputed, with hundreds of scientists refusing to accept it. Yet with less than $100 and a single day’s worth of labor, there’s a way you can prove it to yourself: by building a cloud chamber.
An old fishtank, some 100% ethyl or isopropyl alcohol, a metal base with dry ice beneath it and only a few other steps (see the full article for instructions) will allow you to construct a detector capable of seeing unstable cosmic particles. Yet these particles — and you’ll see about 1-per-second — would never reach Earth’s surface if it weren’t for relativity!