Hacker News Reader

Comment by taliesinb | Hacker News Reader

You can also think of it as magnetic flux lines encountering "drag" as they pass through conductors.

The limiting behavior of this view is in type II superconductors, which entirely "pin" flux lines -- they present an effectively infinite resistance to the movement of flux lines. That's why a magnet levitates over such a superconductor. [1]

You can even image these "vortices" directly [2]

[1] http://en.wikipedia.org/wiki/Flux_pinning [2] http://www.youtube.com/watch?v=7_ZgiumS41Q

View on HN

You might wanna take a look at this video: http://www.youtube.com/watch?v=VyOtIsnG71U

Incredible. For anyone watching, make sure you at least go past 2:20 - that's when they pull out the magnetic rail.

The levitation over a superconductor was the other cool demo that the professor did :).

Lucky kids. When I was in school, the only commercial superconductors were liquid Helium cooled Niobium-Titanium alloys, something not many classrooms could handle. ;-)

Luckily, when I got to programming, we already had zeroes and ones. Imagine our predecessors who had to do it with uppercase o's and lowercase l's...

lOl

Zeroes and Ones? Luxury! In my day we couldn't afford the Ones, we had to make do with just Zeros...

Ha! When I was in school, we had to push the electrons around by hand! You kids had it easy!

You guys had electrons? We had to use scotch tape on a bunch of quarks and give them a half spin and then push them.

Uphill. Both ways.

I'm declaring a winner here ... the only possible thing that could top that is "through three-foot deep snow".

I forget what type we used but it was cooled by liquid nitrogen. That prof. used lots of magnets and superconductors in his research, some cooled by Helium-3. Now that stuff is expensive.

The high-temperature ones were probably Yttrium-Barium-Copper-Oxides (YBCO) I've seen this demo done with them. The magnet's motion is almost undetectable, they appear suspended in the copper pipe until they start to warm up.

http://search.dilbert.com/comic/We%20Didn%27t%20Have%20Zeros (Sept 8, 1992 Dilbert)

Reply on news.ycombinator.com