I didn’t see this covered in the “How fast is lightning” thread (or maybe my powers of extrapolation just ain’t up to task), so let me ask it here:
why is it that some lightning is silent, without any audible thunder?
I’ve seen this kind of lightning twice, and both times it was lightning that appeared to be “contained” within the cloud(s). On one occasion, there was a single (but pretty huge) cloud off in the distance that was flickering with “internal” lightning, almost non-stop (quite a light show).
The other time was with a thick bank of clouds (news reports the following day said the clouds rose to 40,000 feet), where the lightning flashed every few seconds but almost always danced along the bottom of the clouds; occasionally you’d see a bolt that headed earthward, and only then would there be a loud clap of thunder. (In this latter case, the clouds were directly overhead, so I can’t imagine that distance from lighting to ear was a factor here.)
Someone in the other thread said that the speed of lightning can significantly vary, so is silent lightning simply a result of (slow) speed? Ideas, anyone?