Do all thunderstorms have lightning?

Chris - I think that actually, if you're going to have a thunderstorm, that means by definition you're hearing thunder. So if you're hearing thunder, you're hearing a shockwave, and what's happened during a thunderstorm to make that shockwave is that something has heated a patch of the air to a very high temperature. This has made the air expand supersonically, making a shockwave that then comes towards you through the air as a rippling roll of thunder. You can't really have the heating of the air without some kind of an electrical discharge which is what the lightning is. In fact, I think when people have done calculations and measurements, a lightning bolt actually registers a temperature of about 30,000 degrees C which is 5 or 6 times hotter than the surface of the Sun. So I don't think you can have a thunderstorm without a lightning bolt because you wouldn't hear any thunder because something, some discharge has got to actually drive that happening in the first place. I think it's probably just that the lightning is masked behind a layer of cloud or something and you just don't see it.