One afternoon when my cousin and I were about twelve years old, as she and I were playing indoors during a thunderstorm, we saw a small bolt of lightning enter the room through a windowpane. The lightning vanished without causing any harm to either of us or to any object in the room. It didn’t shatter or melt the window glass.
My cousin, like me, remembers this clearly and all these years later we are still puzzled by the incident. I’ve Googled this topic with no results, so I need some Doper wisdom. Is it possible for lightning to pass through a pane of glass without destroying it? Or are cuz and I afflicted with folie à deux?
I’d have to say “no it can’t”. A lightning bolt reaches temperatures into the tens of thousands of degrees (Cite). That’s going to cause some damage to a windowpane, not to mention objects inside a room.
Lightning is, however, extremely bright. Often you’ll see it, seemingly right in front of your eyes, when in fact the bolt struck in a completely different direction. I’ve witnessed this before now, when inside a room and lightning strikes nearby. The flash appeared to be right in front of me, when I knew it couldn’t be. It must have been an illusion.
It’s conceivable, but I’m really really dubious. Lightning is essentially a flow of electricity. It’s possible that if lightning struck your house, there would be enough strangeness in voltage gradients and such to cause miniature electrical arcs inside the house as well. However, there are two problems with this scenario:
First, it’s pretty much inconceivable that lightning could strike your house without anyone other than your cousin or you noticing it (thunder, anyone?). Even if there wasn’t a big momma lightning bolt that caused the indoor lightning, the one indoors still should have made a pretty big pop. If you don’t remember any particularly loud noise accompanying the bolt, then that’s a problem.
Second, glass really isn’t that good of a conductor of electricity. If you know anything about AC circuits, the window would probably act like a big old capacitor if you were trying to transmit current “through” it, and capacitors have a very high impedance for quick, high-frequency stuff like lightning. In other words, very little current could be transmitted “through” the window as you describe.
All in all, I wouldn’t rule it out, but I’m going to have to be skeptical.
Er, no. Capacitors have very *low *impedance at high frequencies. The impedance (strictly speaking, the reactance) of a capacitor is inversely proportional to frequency.
I can’t believe it. Glass is an insyulator, and wouldn’t permit the bolt to pass. Heck, insulators for telegraph and old telephone lines were made of vglass, and even after they switched to ceramic they were glazed, and glaze is basically a thin coatying of glass. And unless it was coated, the glass wouldn’t make a good capacitor either (Leyden jars were lined inside and out with foil. The earliest ones were filled with water, presumably with a little bit of ionized salt in it, intentionally or not).
So I think you might have seen the lightning go around the glass, popssibly through the window frame, which probably was or contained metal, but I doubt if it could have come through the glass itself.
If lightning really did come through the window, there would be tell-tale damage: broken pane, scorch marks on the frame and wherever it hit, broken eardrums from the concussion, etc. I’ll second the reflection explanation.
Right. Although a pane of glass has capacitance in that it will accumulate a charge and this will increase its voltage, it wouldn’t be a capacitor without conductive material on both sides.
So is air. At lightning voltages, there is no such thing as an insulator, there are merely poor conductors. Clearly, you’ve never played with one of those lightning ball toys. If you hold your finger very close to the glass globe without touching it, you can see a very small amount of arcing and corona discharge between your finger and the glass “insulator”.
:smack: You’re right, of course – that’ll teach me to post before my morning coffee has kicked in. Oh well, I still have one explanation left why it seems unlikely.
To clarify: Did you see a line of lightning appear and then disappear, or did you see a “piece” of lightning moving through the window? If the latter, it could be ball lightning, which has been known to pass through windows.
Sure, glass is a lousy conductor, but then, so is air, and lightning has no trouble getting through a mile of air. What’s a fraction of an inch more through a window?
And shouldn’t a capacitor have very little effect on high frequencies? It’s inductors that impede rapid changes, not capacitors.
My point , in my post, was that glass is an insulator even with voltages associated with lightning bolts. In those glass ghlobes, the glass is still an insulator – no current is passing through the glass.
The breakdown voltage of air is up to about 100 times that of glass. So a 1/8 inch thick plane of glass would have the same breakdown voltage as about a foot of air.
I thought that in those glass globes, the inside was coated with some kind of thin metalization that could conduct low currents. Else, when you touch the globe, why is there still some arcs that don’t go to your finger?
There might be, I’m not sure on that score to be honest. But when I press my finger hard on mine, it makes a single “bolt” that a) makes my finger tingle very slightly and b) heats the glass quite noticeably. Also, as noted earlier, I can get some small arcing and corona outside the glass, so clearly there IS current flow through it.
… and I see Chronos has written a staff report on those. No mention of coating the interior. So Chronos, did you happen to contact any manufacturers about those when you wrote that report? (FTR, I have no first-hand knowledge, it’s just what I always assumed.)
I’m not convinced of this. Certainly the main bolt would cause a lot of damage, but a side bolt could have ust less energy behind it. That’s why we’re even talkign about the lightning balls in the first place.
It’s a matter of degree, really. A full-blown lightning bolt carring hundreds of thousands of amps, absolutely. But a high-voltage, low-current static discharge can look like “lightning”, without packing the punch–which is most likely what the OP witnessed, IMO.