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I don't think it's possible to detect a 200uA current across the resistor immediately after the switch is turned on. If I understand it correctly, then this would mean that information is being sent faster than the speed of light. Surely this small instant current must be caused by some kind of capacitance or interference.
I don't think it's possible to detect a 200uA current across the resistor immediately after the switch is turned on. If I understand it correctly, then this would mean that information is being sent faster than the speed of light. Surely this small instant current must be caused by some kind of capacitance or interference.
The long wires act as transmission lines with an easily calculated impedance of ~1 kΩ. When you close the switch, you generate a pulse - a very broadband AC signal - which starts to travel around the circuit. While the pulse is traveling in the line, the line's inputs see the line impedance. So you get the car battery in series with 2x the line impedance in series with the impedance of the light bulb. This directly tells you the amplitude you're going to see near-instantly at the light bulb. Light bulbs are usually low-impedance (e.g. a 10 W, 12 V light has a hot resistance of around 14 Ω), so you're only going to see a tiny pulse on the light bulb. After the pulse has traveled the length of the line and back the impedance seen across the line inputs is the short at the end in series with the conductors resistance of the line itself; in a heavily mismatched setup you're going to see some more reflections going back and forth, this causes the stair-stepped rise over multiple bounces when you do this experiment with "realistic" values.
It's basically a slightly unconventional TDR - time-domain reflectometry - setup.
Anyone care to give us a Too Long; Didn't View?
Earlier quoted context omitted.
200uA of current flows through the lightbulb instantly, but it doesn't reach full current until speed of light delay.
I don't think this is possible. If it were true, then you could add a transistor and an LED on the other side of the 1000M wire, and light up the LED instantly as soon as you press the switch. (Transistors and LEDs only take a few nanoseconds to turn on.) It's not possible to send any kind of signal or information faster than the speed of light.
I'm a big fan of AlphaPhoenix's content. He deserves to be in the big leagues of science YouTubers with SmarterEveryDay, Veritasium, Mark Rober and 3B1B.
Physics Explained is great physics channel that doesn't shy away from math, with derivations of many fundamental equations. His most recent one deriving the Chandrasekhar limit on white dwarf stars from relatively basic physics is great!
The Efficient Engineer is a really good one for clear concise explanations of mechanical engineering principles.
That Veritasium video is one of the most controversial educational videos I've seen. I think one of the issues with it is that it's a bit pedantic, but also ignores other issues, that invites other people to be pedantic about it.
It’s not pedantic. EMI “teleporting” outside of wires is a real world issue that engineers deal with constantly. FCC certification is almost entirely about this phenomenon. It’s just told in a confusing controversial way.
That Veritasium video is one of the most controversial educational videos I've seen. I think one of the issues with it is that it's a bit pedantic, but also ignores other issues, that invites other people to be pedantic about it.
That Veritasium video is one of the most controversial educational videos I've seen. I think one of the issues with it is that it's a bit pedantic, but also ignores other issues, that invites other people to be pedantic about it.
As much as I love Veritasium, I feel the OP video is better than his. Actually doing the experiment is really good, and it honestly feels like he was fishing for another debate like the faster than wind car by giving only a super theoretical and unintuitive explanation. (I don't have any real evidence of that, but it does /feel/ like it.) I also wonder what would happen if, instead of a setup like this: ┏───────light…