If lightning can destroy trees, how come that people survive it?

  • Thread starter Thread starter jetwaterluffy
  • Start date Start date
  • Tags Tags
    Lightning Trees
AI Thread Summary
Lightning can destroy trees due to their size and the high moisture content, which causes them to explode when the water inside boils rapidly. In contrast, humans often survive lightning strikes because their bodies have lower resistance and are typically not directly in the path of the lightning. The 'skin effect' allows current to flow mostly on the surface of human bodies, reducing the impact on vital organs. While trees can be severely damaged or destroyed, humans can survive varying levels of current, with fatalities occurring in a specific range of current that affects the heart. The difference in survival rates may be attributed to the directness of the lightning strike, with trees often taking the full force while humans may only experience offshoot paths.
jetwaterluffy
Messages
227
Reaction score
0
I mean, trees are a lot bigger than people, aren't they?
 
Science news on Phys.org
Many people don't survive, of course!

I think it must be something to do with the difference in size and the resistivity of the structures. Trees explode because the water inside them boils rapidly and produces steam. This is because the produce of Volts and Current (defined by the overall length and the resistance) - the Power Dissipated - is high enough to boil the relatively small amount of water in the tree. (Less water implies a higher resistivity)
For an animal body, the volts are lower (it's a shorter structure and the voltage relates to the Field times the length) and the resistance is much lower (mostly water with dissolved salts). This suggests to me that there will be less actual Power involved; not enough to actually boil your insides.
There is also the 'skin effect' which determines the depth at which a pulse of current or and AC signal passes through a conductor. It stays just on the surface of a very good conductor. I think, therefore, that there will be more current flowing through the inside of a tree than of a human.

Otoh, plants don't have a delicate nervous system and, if they don't actually explode, they tend to stay alive and produce green shoots from some of the shattered stump. Animal hearts can just stop from the electric shock.
 
All that is true, but trees are not always destroyed. A hot strike will explode a tree as you say, but a cool strike will set it on fire. We can survive a very small current thru the heart, or sometimes a very large current. In the band in between we are dead. They have different theories as to why that is. Depending on the actual path the lightning takes, the actual current thru the heart can be high, low, or the fatal in between. In most cases of human strikes, the human is only a small part of the path as the air around us is ionized and becomes very conductive.
 
How often are people DIRECTLY struck by the main path of the lightning and not an "offshoot" path? Perhaps the difference is that trees commonly take the full brunt of the strike since they are taller and wider while people are usually only indirectly struck?
 
Thread 'A quartet of epi-illumination methods'
Well, it took almost 20 years (!!!), but I finally obtained a set of epi-phase microscope objectives (Zeiss). The principles of epi-phase contrast is nearly identical to transillumination phase contrast, but the phase ring is a 1/8 wave retarder rather than a 1/4 wave retarder (because with epi-illumination, the light passes through the ring twice). This method was popular only for a very short period of time before epi-DIC (differential interference contrast) became widely available. So...
I am currently undertaking a research internship where I am modelling the heating of silicon wafers with a 515 nm femtosecond laser. In order to increase the absorption of the laser into the oxide layer on top of the wafer it was suggested we use gold nanoparticles. I was tasked with modelling the optical properties of a 5nm gold nanoparticle, in particular the absorption cross section, using COMSOL Multiphysics. My model seems to be getting correct values for the absorption coefficient and...
Back
Top