40
votes
Why is the color of lightning white or blue rather than nothing?
TL;DR: Air in lightning gets hot. Hot things (like the Sun) emit light in a broad spectrum; including visible. You are right there will be emissions outside the visible - but your eye doesn't pick ...
- 119k
38
votes
Accepted
Tree vs lightning rod: why does one burn and the other not?
The amount of heat generated by current flowing through a resistor (whether from lightning or more ordinary sources) is directly related to the power dissipated by the resistor, which is
$$ P = I^2 R.$...
- 126k
37
votes
Accepted
At what temperature do the laws of physics break down?
Hank Green is describing the concept of the Planck temperature,
$$
T_\mathrm{P} = \sqrt{\frac{\hbar c^5}{Gk_B^2}}\approx1.4\times 10^{32}\:\mathrm K,
$$
which is defined as $\frac{1}{k_B}$ times the ...
- 134k
33
votes
Can Special Relativity hold even without motion?
You are mixing up two different things.
The observers know that light takes time to travel the distance from the strike to their eyes. So when they are calculating the time the strike occurs they ...
- 358k
27
votes
How thick in diameter is the average lightning bolt visually?
Well, if all what you care is just the visual (subjective) perception of how wide a lightning bolt looks like, here we go. We take as an example lightning which very often hits CN Tower in Toronto:
...
26
votes
How thick in diameter is the average lightning bolt visually?
There are a couple ways the answer could go.
The 1 inch diameter probably refers to plasma generated by the bolt. The air for some distance around it might be hot enough to glow.
Then there are visual ...
- 41.1k
25
votes
What causes the direction of lightning flashes?
They exist, they're just rarer, which is why you don't often see them. They're called gigantic jets, and they connect storm clouds to the reservoir of charge in the ionosphere. Here's one that was ...
- 35.6k
23
votes
Accepted
Why does moderately distant lightning sound the way it does: relatively quiet high pitched thunder first, and then much louder low pitched thunder?
I'm not an expert, but I spent some time with references 1 and 2 several years ago. This answer is based on some notes I took.
Measurements using the radio waves produced by lightning indicate that ...
- 54.5k
19
votes
Accepted
What determines the shape of lightning?
Your assumptions are right. There is indeed physics involved in lightning shapes.
Why can’t lightning just be in a plain, straight shape?
From the Indiana Public Media's Moment of Science Podcast ...
- 712
18
votes
Accepted
Can Special Relativity hold even without motion?
As already stated by John Rennie, the observers are already aware of the property that light travels at a constant speed, and they account for the given fact, so even if the lightning strikes are not ...
- 1,368
15
votes
How thick in diameter is the average lightning bolt visually?
When I was a teenager I had a newspaper delivery round; one morning a storm broke as I was out delivering papers and a lightning bolt struck the ground just in front of me. It seemed to me to be about ...
- 181
14
votes
Does a tower bell ringing prevent thunderstorms?
There is enormous energy in a storm, which will be randomly oriented with respect to a bell tower.
The energy in the bell's sound will be radially falling with $1/r^2$ and is not directional. The ...
- 234k
13
votes
How many photons are emitted by a lightning strike?
From How Big Is A Lightning Bolt? we see that a lightining bolt is “an inch wide and five miles long”, and at “50,000 °F”. So in useful units, approximately 3 cm diameter, 8 kilometer long, 28000 K ...
- 914
12
votes
How could lightning have killed 322 reindeer at one time in Norway?
The National Weather Serivce has a page on ways someone can get struck by lightning. Two possibilities jump out at me as potential killers in the case of the reindeer:
1. Ground current
Lightning ...
- 10.8k
12
votes
Tree vs lightning rod: why does one burn and the other not?
The high electrical current in a lightning strike delivers heat energy along
the full length of the lightning bolt. Part of that length is in the ionized air over the
plane, part is the plane's ...
- 9,943
11
votes
Accepted
Is it possible for a lightning strike to hit the ground if there are high rise buildings nearby?
Yes.
A lightning conductor on top of a high-rise structure is designed to minimize the possibility of lightning hitting the structure by the virtue of its pointed tip giving rise to very high ...
- 5,257
11
votes
If lightning is caused by ionisation of air, why does it only last briefly?
Fire is a chemical reaction fueled by some product that undergoes combustion, generating energy by breaking (usually) carbon chain molecules down into $CO_{2}$ and $H_{2}O$. So long as fuel plus ...
- 15.6k
10
votes
Simulated nuclear blast using electric arcs
We can do a quick and simple energy comparison between lightning strikes and nuclear weapons.
An average lightning strike releases approximately $10^9$ joules of energy, which is one gigajoule. ...
- 56.4k
9
votes
What causes the direction of lightning flashes?
If you look at slow-motion videos of lightning strikes you'll notice that a "pilot lightning", called a step leader, originates indeed in the cloud and propagates, branching out roughly radially from ...
- 4,310
8
votes
If lightning is caused by ionisation of air, why does it only last briefly?
For the fire the source of energy is the "chemical" energy stored in the reacting compounds whereas for lightning the stored of energy is electrostatic in nature due to the separation of ...
- 97.9k
8
votes
How did a spark generate electromagnetic fields that radiate to places?
EM waves are generated by accelerating charges. The transmitter is a circuit that supports an oscillating current (which requires that the charges are accelerating during the oscillations). The ...
- 41.2k
7
votes
Why does moderately distant lightning sound the way it does: relatively quiet high pitched thunder first, and then much louder low pitched thunder?
Air is not a dispersive medium for sound waves. At least, in normal condition.
When a lightning is produced, the air is heated up to a very high temperature, creating a shock wave like. The sound ...
- 896
7
votes
Accepted
Does a tower bell ringing prevent thunderstorms?
The question whether ringing a bell on a tower can influence lightning strikes involves two aspects: hypothesizing physical processes which might be relevant, and then figuring out (or measuring) ...
- 59.6k
6
votes
Accepted
Can lightning happen in a vacuum?
Depends on what you mean by "lightning". Yes, because charge can flow across vacuum, but no, because you won't see anything. The visual effect that you see in the sky is actually a luminescent plasma ...
- 2,105
6
votes
Why is the color of lightning white or blue rather than nothing?
The high voltage of the lightning arc separates electrons and ions, briefly forming a plasma. When the electrons and ions recombine back into a gas, the formerly free electrons drop to a lower energy ...
- 2,624
6
votes
What causes the direction of lightning flashes?
According to Wikipedia, charge separation in a thunderstorm occurs as follows:
The differences in the movement of the precipitation cause collisions to occur. When the rising ice crystals collide ...
- 56.4k
6
votes
Accepted
How many photons are emitted by a lightning strike?
According to Could We Harness Lightning as an Energy Source?:
An average bolt of lightning, striking from cloud to ground, contains roughly one billion ($1,000,000,000$) joules of energy.
...
- 40.1k
6
votes
Accepted
Why isn't thunder muted or softened by rain drops?
Typical wavelengths in thunderclaps are vastly greater than the diameters of raindrops. Consequently, the pressure around each drop is almost isotropic, and the drop is barely distorted. Water is ...
- 3,109
6
votes
Why does moderately distant lightning sound the way it does: relatively quiet high pitched thunder first, and then much louder low pitched thunder?
Although I am not a thunderstorm expert either, my guess would be, that the reflections of the soundwaves between the atmosphere/clouds and/or ground are responsible for the delay of the low ...
- 7,514
Only top scored, non community-wiki answers of a minimum length are eligible