Hey, I’m a NASA dude, too. All electromagnetic waves are comprised of photons. Photons like the ones in X rays and audio signals don’t have to be visible. They have varying uh wavelengths. The electromagnetic spectrum is much wider than the portion that contains visible light. It also explains why electromagnetic waves travel at light speed since photons are the only thing that can go that fast. Photons must travel at the speed of light! Hel-loo!
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