How can we see lightning in detail when the average bolt only lasts for about 30 microseconds?
In: Planetary Science
When you say a bolt lasts 30μs, that’s about the time for one ‘surge’ of electrons to jump through the air, but that isn’t the thing we see. Electrons, even trillions of them at once, are invisible.
When that surge happens, it heats the air along its path glowing-white hot (as the flowing electrons crash into air molecules), and that’s the part our eyes detect. The air remains hot, and visible, for tenths of a second even though the electrical event that heated it is over.
Another thing to think about is, a lightning bolt is usually not just one electron surge. After that first surge, the heated air is more conductive for a while (IIRC due to extra ions created by the first surge) and so it’s easy for a few more surges to jump along pretty much the same path. Every one of them re-heats the air, keeps it glowing, and keeps the bolt path visible to our eyes.
Our eyes are pretty slow. When light hits them they see light, and when the light stops hitting them the image fades.
So if we are only briefly exposed to a very bright light, then our eyes will see the shape lingering for a dozen milliseconds or so as it fades.
Our eyes aren’t like a camera shutter that only “sees” for a small amount of time every frame, the cells in our retina are continually gathering light and react the moment enough light hits them so even an incredibly brief flash will activate them as long as it’s bright enough.
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