[dekhn]

Few, if any; instead, it's typically the propagation of an electromagnetic wave that transmits a signal: https://en.wikipedia.org/wiki/Speed_of_electricity

[sethammons]

This veritasiun is relevant, complete with reddit discussion:

https://www.reddit.com/r/engineering/comments/qxrsrp/the_big...

What if you made a really big circuit consisting of a battery, switch, lightbulb, and a wire that goes out 300k km on either side making a circuit that should take 1s at the speed of light to travel through. How long after closing the switch will it take for the light to go on?

[reaperman]

“Few”, yes. But definitely some. I don’t think you can have propagation of EM wave through a conduit without at least pushing one electron into the conduit and removing one electron from the other side of the conduit.

[dekhn]

Yes, but it's subtle; see https://en.wikipedia.org/wiki/Drift_current and https://en.wikipedia.org/wiki/Drift_velocity and https://en.wikipedia.org/wiki/Electron_mobility for more details

I was pretty surprised about this since I had mistakenly believed that electrons had a velocity near the speed of light, which I think is only true in particle accelerators.

[reaperman]

Indeed - I thought most college Physics 2 courses teach that electrons actually move quite slowly through conductors. It’s the “wave” which propagates near the speed of light, not the particles.

[dekhn]

My mistake was being a biologist, and skipping or sleeping my way through the EE part of physics :) and then saying the wrong thing in front of some very smart people

[reaperman]

Lord, I make that mistake on HN nearly every month. At least you didn’t have a “Putnam award” moment:

https://news.ycombinator.com/item?id=35079

[dekhn]

I've had something similar- when I was deciding what grad school to go to, I was explaining how RNA enzymes work to some professor at UC Boulder, who ended up being Tom Cech (who won the Nobel for discovering RNA enzymes); he had to correct a lot of the details I messed up. I ended up going to UCSF and fortunately didn't try to explain prions to Stanley Prusiner.

In short, nearly everything I have learned is from saying dumb things in front of very smart people who instantly understood my misunderstanding and knew exactly how to explain it so I understood. That includes Sanjay Ghemawat and Jeff Dean telling me "your idea isn't so good, it's n-squared, here's a linear solution"

[pyinstallwoes]

what is the electromagnetic wave made of, what's the substrate it is composed of and moving through?

[dekhn]

The wave is electromagnetic energy passing through a waveguide (typically copper) mediated by electrons. See https://en.wikipedia.org/wiki/Waveguide