JoeyBlades, how can, in theory, something be elastic AND rigid?
The head of a hammer is one example.
Not theory, fact.
My head is a theory,and thats a hard fact.
Nick is right though.
I was struck by lightening in my right big toe when I was 10 or 11.True
Pete,
Elastic (in physics) means “no loss of kinetic energy between particles during a collision” - or something close to that, I don’t have my physics dictionary handy for an exact quote.
It has virtually nothing to do with that rubber-bandy material that makes up the wasteband of your boxers…
Check out this mental exploration of lightning:
WHAT IF LIGHTNING TRAVELLED SLOWLY? http://www.amasci.com/tesla/spark.html
BILL BEATY billb@eskimo.com
http://www.amasci.com SCIENCE HOBBYIST
Seattle, WA USA
Here’s a subtle aspect of the speed of lightning “leaders”. A leader does not travel at the speed of light, nor does it travel at the speed of the moving charges. What then creates its speed? Something weird! A lightning leader is a conductor. It is a HIGHLY CHARGED conductor.
What happens when a long, thin conductor has an immense charge on it? It grows “St. Elmo’s Fire” at any sharp spots, therefor the tip of an advancing lightning leader will “shatter” the air into plasma (into separated electrons and positively-ionized nitrogen molecules).
But the leader itself is made of plasma. Right. In other words, the charge on the plasma-filament makes the plasma-filament grow longer.
What controls its speed? All kinds of things. The speed of leader growth is obviously limited to the speed of light, but the LOWER limit on the speed of a leader is millions of times slower.
I’ve seen lightning leaders crawl slowly across the base of a thunderstorm, maybe going a couple of miles per second. I’ve seen videotapes (http://www.tornadoproject.com) where the same sort of horizontal lightning appeared to crawl at a fraction of a mile per second.
The speed of a lightning-leader is mostly controlled by the gradient of voltage at its tip. If a leader is highly charged, it will go faster. If a leader invades a cloud which contains opposite charge, then the leader will become highly charged by “induction”, and therefor will go faster.
If a leader wanders out away from the charged clouds, it can slow down and stop entirely (we’ve all seen branched lightning, no? Where many branches just hang out in space with nothing at their tips?)
BILL BEATY billb@eskimo.com
http://www.amasci.com SCIENCE HOBBYIST
Seattle, WA USA
We don’t have many lightning storms in SF and hwne they we do they are strange. Sometime thunder will rumble for almost a mniute. I’ve lived here 25 years and have been in maybe 5 at most, all very mil. During one I was watching, shooting out from the street in front of my house, at about a 45 degree angle were what appeared to be bottle rockets. They traveled at about the speed of a bottle rocket and must have been some sort of lightning.
IIRC, the speed of the electric current in a good conductor, like copper wire, is about .3c, so the earlier estimate of .1c for lightning’s return stroke seems about right.
“non sunt multiplicanda entia praeter necessitatem”
St Elmos fire is really weird I have only seen it a few times.Once along a barbed wire fence,the wires had an ‘aura’ along them that slowly concentrated around the barbs then to the tops of the metal fence stakes. Jim, the stuff you saw has a name but i forget what it is, I have seen that out on the plains too.That was a great discription of it. It seems to be intermediary between St.Elmo’s and ‘real’ lightening. ( ball lightening may or may not exist I have never seen it but…).Those long low rumbles are from horizontal lightening aWWWAY up there.It can travel dozens of miles,instead of the thousands of feet vertical stuff does. When it is lower you can hear it coming, it’s real nice when it’s directly over head, that low rumble getting louder , beginning of a boom,then the a great loud sharp KeeeeeeRACK! that makes windows rattle,old ladies pee their pants and cattle stampede, then it rumbles away . Actually you don’t hear it coming, by the time you hear it, it’s done left here and gone.Cause lightening is real fast. i don’t know how fast, I think I will start a topic on that when i leave here.
“Pardon me while I have a strange interlude.”-Marx