Maybe you need a Slashdot License. They come from the Ministry of Housinge.

There is no theoretical reason that a room-temperature superconductor cannot exist.

Room-temperature superconductors would be really cool. It's not clear that electromagnetic propulsion gets you to orbit, though. Once there, sure it works.

Multiple-Tesla fields that are changing their orientation rapidly in time aren't particularly healthy to be around. Induced currents in your nerves, heating, etc. That MRI field is acceptable because it's DC. That is, if you don't have any ferromagnetic objects on you.

No, the superconductors are not simple magnets.

What's on the tele then?

Rockets being the only solution does not automatically mean rockets are a viable solution. Please quit ignoring the real challenges presented.

Unfortunately, this can't be approached as an engineering problem and get the result you would like. It needs to be approached as a problem in fundamental research of the physics underlying our world.

There were lots of efforts to miniaturize the vacuum tube. They only resulted in smaller tubes. It took new insights in fundamental physics before people could understand how to make a transistor. There were many experiments with germanium (a natural semiconductor) that could have led to the transistor before 1947 if anyone had understood what was happening.

Some steel. Not all of them. That's why the refrigerator magnet doesn't stick to that silver door.

A field strong enough to work on water would kill you first.

Look at the amount of money made on oscillococcinum, and you might agree it's a successful hack to make money from the stupidity of others.

This would be cool if it was more than a stage trick. The superconductor needed to do this used to be mail-ordered from Edmund Scientific. So lots of hackers were doing levitation demonstrations in the 90's. People think it's cool because they've not lived through that, or have forgotten it.

It works on the principle of superconductors excluding a magnetic field. When they are cooled to liquid nitrogen temperatures. Steel is low in ferromagnetism and isn't as good a conductor as copper so it's not as good for making electromagnets.

Well, I did that once with a bottle of liquid nitrogen from Airco and a superconductor I bought from Edmund Scientific. This was before there was a Slashdot. So, no, not impressive.

Before someone makes a working hoverboard, we will first hear about the principle that makes it possible. Because one that's practical is almost guaranteed to get someone a Nobel Prize. And certainly Lexus would go for that if they could.

No new principles lately. There is an existing principle of magnetic repulsion that would work only in an extreme condition. One requiring really special stuff buried in the street, and probably including liquid nitrogen to keep it working for even a short time and a few feet.

So, it's a gimmick.

The article claims that NTP is the cause of the leap second. NTP is just a protocol that handles keeping computer clocks in sync with each other and with the official time (UTC, IIRC).

If NTP handles leap seconds by increasing update frequency and then coming to the conclusion: "Whoa! my offset just went from 0.3 ms to 1000.25 ms, lets step the clock a second once we're sure this was not a fluke measurement". then that's a bad way of handling it in my opinion. (also suddenly speeding up does not provide a smooth-enough transition).

One of the things that is bad about this is that when normal operation can handle (the bandwidth of) most hosts updating every 1024 seconds, and a few hosts (just rebooted, just installed, sync lost, whatever), now all of a sudden a synchronized (pun intended!) attack will take place where many many hosts will increase their update frequency by several order-2 magnitudes.

For google, they internally have needs for synchronized clocks. Why I don't know, and I don't care. They have decided to handle the leap second in a more controlled way. It's actually not that hard. Just make sure that everything syncs off one level-0 server, and during the 20 hour period leading up to the leap second, add a variable number of microseconds to the exported time.

The thing that people-who-don't-know-better are suggesting is that the second will be the same all the time.

They think that nothing bad will come from "thirty years from now, the sun is in the south at 11:59:30" (assuming an average of 1 leap-second per year).

(I can't think of anything bad that would happen... but I know my limitations. It's probably annoying as hell to /some/ fields of research or something....)

Suppose I have a variable A that ends up with the value Y*X. (Y might be a difficult calculation). Next I want to calculate B = A/X .

This could happen for example when I'm doing physics calculations where the parameter X eventually cancels out.

Anyway, this will end up with B = Y if you do the math and cancel out the X. However, if you let a computer follow through with the calculations, when X=0, you'll end up with a variable A with the value zero. And if you assign a value of "1" to 0/0 you'll silently get a wrong result when Y != 1.

So: The computer should throw an error. There is no way a compiler can come up with a reasonable answer for the variable B.

If you want it your way, you write B = X?A/X:1; If you want get rid of that expression everywhere in your code, you get a few choices. In C++ you could probably define a "myfloat" that overloads the division operator. Or you could make a "mydiv" function.

"Hacker's Keyboard" has a number row, tab, and arrows.