Today marks the 50th anniversary of the launch of America's first satellite, Explorer 1.
This was a response to Sputnik, launched by Soviets a few months before. The whole story is actually a bit complicated (Clavius.org has a nice synopsis, and AstroProf has more too); but ironically the Americans could have had the first satellite in orbit had they not been reluctant to use a rocket built for the Army and based on German technology.
Explorer 1 was equipped with an X-ray detector that was basically a fancy Geiger counter. Built by a team led by James van Allen, it was lofted up to see what the radiation environment of space was. The team was astonished to discover that near-Earth space was tremendously radioactive; their detector saturated.
And thus the basis of the Moon Hoax was born.
Too bad; if the hoax believers had some basic science education they'd understand the problem. What Explorer 1 discovered were the van Allen radiation belts: regions around the Earth where the magnetic field of our planet has captured subatomic particles. Moving at high speed, when these slam into the metal walls of a satellite they are decelerated. This process produces X-rays (called Bremsstrahlung -- German for "braking" -- radiation), and that's what the Explorer 1 detector detected. Moon hoaxers get terribly confused about this, saying there are deadly X-rays in space. They're wrong: the X-rays are a by-product of the subatomic particles screeching to a halt inside metal. Unless the Sun is flaring, there is very little X-radiation in near-Earth orbit. It's the subatomic particles that are dangerous, but they can be stopped by various substances like glass and insulation without creating X-rays.
Try explaining that the hoax believers. You might as well speak in Klingon to them.
Anyway, Explorer 1 was a fantastic achievement. Not only was it the US's first satellite, it also broke through a new frontier in science. We learned that the Earth's magnetic field has ramifications for space flight, and eventually led to a better understanding of how we are coupled with our nearest star, the Sun.
Mind you, these guys had no clue what they'd find. That's why they put the X-ray detector in Explorer 1 in the first place! And look what happened.
I salute the pioneers of the space age, and of the space science age. We owe you folks a lot.