They travel at the same speed, in the same medium. c is the speed of light in a vacuum, all EM radiation travels slower in any other medium.
The complicating factor here is that when you have electricity flowing in a wire, the fields are generally mostly outside the conductor, not in it. That is, the signal propagation delay depends more in what you are using as an insulator around wire than the material of the wire. This has had practical consequences in the past; if you replace the insulating jacket of one wire in a twisted pair with a slightly different material, on long runs it will ruin your signal.
EM radiation, whether radio or visible light is photons, and photons only have one speed. However, electrical conduction is the movement of electrons, not photons.
> EM radiation, whether radio or visible light is photons
Is the only part that's not wrong in your post.
Photons only have one speed in empty space. They slow down when traveling through any medium other than vacuum.
> However, electrical conduction is the movement of electrons, not photons.
Electrons move because they influence each other through their fields, which are transmitted by photons. Electrical conduction happens at the speed of the fields, not at the speed of the electrons. When you push one more electron into one side of a conductor, an electron flows out the other side when the fields reach the other side, not when the electron does.
(As an analogy, consider a rubber hose full of steel balls. When you slowly push an additional ball in from one side, another ball starts to fall out of the other side as you push the first ball in, perceptually instantenously⁰, regardless of the speed you are pushing the new ball in.
(0): After a delay of (length of tube)/(speed of sound in steel)
I'm not a physicist, but as far as I know, outside of general relativity electromagnetic perturbations always travel at the speed of light (i.e. to affirm that photons always travel at c is correct).
It's only after the fields interact with electrical charges (atoms and their electrons for example) that a secondary field is induced as these charges begin to oscillate. This field will add over the original field, "shielding" an external observer from the original oscillation and apparently slowing down the propagation of electromagnetic waves.
Looks like the author noticed and changed the title to "Direnv - and reinventing the wheel with envloader". Going by the TLD I initially thought that he's from Germany, but no, "de" are just the last two letters of his surname...
I think that these types of errors are made mainly by native English speakers, as they learn and practice their language mostly 'by ear', without having to think much about the logic behind it.
And this is as much a logical error as grammatical one.
As a (barely) recovery grammar festidian I highly recommend checking out this video by Dr Geoff Lindsey [1]
TLDW: some fascinating realignment of perspective from a linguist about such things [^2], and the - frankly moderately mind-blowing - revelation that despite caring about language I've been gleefully pronouncing "covert" 'wrong' my whole life (and will likely continue to do so)
As an aside: despite caring about "correct" use of language I've always been willing to frivolously split infinitives - it's against the rules, but I think quite an effective evolution of language
Good to have linguists around reminding us to boldly go explore :)
You stretched 500m to 5km but kept only one valve. Why?
And presuming that whole wagon doesn't burst because a couple of bullet holes, is it unrealistic for onboard pressurized tanks to keep up with escaping air while outside is getting pressurized?
> You stretched 500m to 5km but kept only one valve. Why?
This is the worst case scenario by assuming only one valve is functioning. Theoretically, even that could break, but I'll assume there are enough redundant valves that at least one will always work.
> is it unrealistic for onboard pressurized tanks to keep up with escaping air while outside is getting pressurized?
It depends on the size of the hole. A bullet hole for an average train car size would take hours to become deadly and could easily be corrected by onboard air (depending on how much air is onboard), but a gun isn't going to cause a bullet sized hole. It is quite violent. Something like a catastrophic door failure, or derailment, would deplete the oxygen in less than a second. Basically, the inverse of oceangate; instead of everyone imploding, everyone would explode. Since I also suspect there will be valves on the vessel to handle releasing small amounts of gas enroute (to allow adjusting internal pressures to match destination atmospheric pressures), this could also get stuck open.
I suspect, if anyone were to actually do this, they would go for low pressure (like high altitude) instead of a vacuum. The speed of sound is so high, they could easily reach it in the tunnel. Further, people just need oxygen masks instead of dying a horrible death.
Nobody has mentioned this while following along with all the US hyperloop failures, so it is clear nobody has really tried engineering this thing, IMHO, and why I said my original comment about it. If someone were actually engineering the system, these are all pretty obvious things. As described in the original 1800's systems and by Elon, it is an impossible system. I used to think about this thing all the time in the '90s, so maybe I've thought too much about it.
I'm also curious about other issues, like maintaining low atmosphere or a vacuum (these were the key failures in older attempts in the late 1800's) in the tunnel in an energy efficient way. If it can't be kept, things will deteriorate at an accelerated rate, introducing catastrophic failures early in the system lifetime. There is also maintenance and inspections to consider. Not to mention that underground is already dealing with increased pressure from the earth, it also has to support it while maintaining a vacuum. I suspect above-ground tubes are probably far cheaper to build and maintain, but at that point, you might as well build a train.
Since moving to Europe, I can go pretty much anywhere in Europe in a day. Heck, I can get on a train this evening, sleep in a bed on the train, and wake up on the other side of Europe tomorrow morning for breakfast, for a little more than the cost of an average hotel room. Trains are great, well understood, and pretty fast. The problem the US has (as seen with the California high speed rail), is that they 'want it to be all US based' instead of hiring experts from across the ocean who work on these things every day. The US has no experience building high speed networks, which is part of the reason the hyperloop even has a chance at getting money. It's a collaborative Dunning-Kruger effect.
I think if the US can get to the point where they can develop high speed networks, in general, then stepping up to something like the hyperloop is a good idea. Other nations are still working on the hyperloop and they are making good progress, but I'm not as familiar with their details.
His statement was about a certain, obviously real tendency in general, existence of which is reasonable to assume there is enough research about.
He objected not to the unlikelihood of an accidental manipulation, but to the potential flaw in your comparison (which was at best a valid opinion).