If you have an old digital camera, try getting images with the lens cap ON, any light you see in said images is cosmic or other penetrating radiation. Newer cameras have built in software that takes several exposures and averages them to remove this type of noise, so maybe a webcam might be a better choice.

I just thought I’d add/clarify a point: flash drives will last significantly longer than floppy disks, on average. Floppy disks (and the drives to read them) are magnetic, mechanical devices. Magnets lose the molecular polarization (the so-called bit-rot on a floppy) and mechanical devices can lose precision or break.

With a flash device, your limitations on longevity are almost entirely electrical (or, dare I say, atomic). The individual memory cells in flash memory devices are composed of floating gate transistors, which are incredibly small. The only way to actually damage one short of traumatic abuse would be to apply too many amps to it, blowing it (and surrounding transistors) out like a fuse. This is most likely to happen in someone’s pocket from static electricity or while being inserted into a poorly/improperly grounded computer. The other components on a flash device (IE, not the memory itself) are likely just as, if not more, sensitive to such current fluctuations. I suspect this is how most flash drives “die”.