No, the box is an essential part of the system. In the thought experiment neither the box nor the photon has mass but both possess momentum since the photon can bounce off the walls of the box. The photon and the box, together, form a system that has mass.

You can see how systems can have mass by rearraning the mass-energy equivalence equation to solve for mass:

m = sqrt(E^2 - (pc)^2) / c

The energy and momentum of a fundamental particle are related so you can't manipulate them independently. But if you have more than one particle it's pretty easy to manipulate the momentum of the system without changing the energy, and thus make m non-zero.

Many teachers, including the pop science variety, like to appeal to your intuition. Sometimes that's okay, sometimes it just stunt's your understanding. Your idea of mass is rooted in pre-20th century physics. The end of the 19th and beginning of the 20th century changed how we think about a lot of things, mass included. You're trying to take your idea of mass as an axiom and make everything else fit. It doesn't. Photons are massless. If they weren't, they would either not travel at the speed of light or have infinite energy. The "thing" that gravitates is energy and various types of energy flux, including momentum. That explains, consistently, how photons can travel at the speed of light, massless particles can interact via gravity, and adding energy to a system can increase its mass.

Energy density, yes.

https://en.wikipedia.org/wiki/...

People used to say "relativistic mass." We've realized that was a bad idea.

I can buy alcohol because I don't live in Saudi Arabia. I can have an OS that doesn't know or care how old I am because I don't live in California. That law literally doesn't apply to me. If I make a distro where I am, why should I bother with age verification at all? It's none of my business if a friend of a friend or a complete stranger decides to download it and install it on a machine in California. Not my circus, not my monkeys.

You can get fired at the drop of a hat for no reason at all. Bosses blow their top over being 1 minute late. Fill out these forms you just filled out last week and again online before you can see the doctor. IRS knows exactly what you made and what you paid in witholding, and what you owe but YOU need to compute it, better not be wrong! Don't be late! Rent and mortgage take up an ever increasing portion of your monthly income (if any). 23 calls a day, mostly scams. You have health insurance even though it was damned expensive, but somehow you still owe a heap of money you don't have after a single visit to the ER.

Meanwhile, you're getting badgered about your "credit score". If you let it get bad everything gets more expensive and it gets harder to get a job (for some reason).

Yeah, you're less likely to actually die today than years ago, but your place in life is far more precarious than it was even 20 years ago. More things demand your attention.

The Chinese have these kinds of robots deploying much larger installations. They also have drones that fly panels into mountainous areas for installation.

Not that I'm knocking it, it's good that they are copying good ideas. The cheaper solar gets the better, and for political reasons stuff like this has to be home grown.

The UK has a head of state (a king) they've spent a thousand years learning should stand around a look pretty with medals and things but that's about it. The US has a head of state (a president) they've spent at least the last hundred years turning into a cult of personality and giving more and more power to.

France has spent a few hundred years violently oscillating back and forth between the two. They've demonstrated it doesn't really matter whether you call it a king or a president, it's how much power you give them.

The first fission reactor in space, the American SNAP-10A had an experimental ion thruster.

Yes, but it didn't go to Mars. That's why I said we didn't have good ion thrusters. The one on SNAP lasted a whole hour and apparently had quite a few problems even then. Getting the things to last long enough and produce enough thrust to be useful even for station keeping is a fairly recent thing.

Topics that do not have much to do with each other at the moment.

While I am not convinced that is the real reason, it would make a lot of sense if it was.

Indeed.

Well, yes. I am aware what the GPL means, but I realize my statement may not have been clear enough. Lets me rephrase that: "A distro that is hard to compile/modify for a regular user".

Interesting. Now /. is not important enough for somebody to get paid to push this crap. Hence I think deeply mentally defective person with delusions of superiority. You know, like the a bit more extreme conservatives. I hear some of them even claim these days that the war with Iran is a good thing and that of course the US will win and everything will be fine afterwards. No actual expert has stated something even remotely like that as the best-case scenario.

The depth of sheer human mental incapability and capability for delusion is truly staggering.

That is why I wrote "And it needs to be done by the right people" ...

Some people are like that: Complete failures at reality perception.

You seem to have slept through that course because you do not even have the very basics right. First, for the El Gamal asymmetric scheme, there is a security proof. This proof does not extend to all possible attacks, but is pretty strong and the limitations can be fixed. Second, AES is a _symmetric_ algorithm. This is so basic that I must conclude you would have failed that course if there was any real examination. And lastly, you seem to have a reading disability, because I did nowhere claim that AES is unbreakable. My claim was that it is not breakable by QC or that it getting breakable by QC would implicate it also is conventionally breakable because QCs cannot practically do brute-forcing of the remaining effective key length.