Huh. I always thought that scrith was cool - but now I know it’s cold.
The books point out another problem with unobtainium (called catchcloth in their universe): it significantly reduces your maneuverability options. The momentum vector for absorbed particles is strictly away from the sun. But for reflection, it can be a vector with a 180 degree range. Which means you can head towards the sun, and tack, and do other neat things.
That’s a great book series - someone should make an RPG campaign setting out of it!
If a solar neutrino can pass through a light-year thick block of lead without interacting, how do neutrino detectors on earth capture solar neutrinos? I believe several solar neutrinos are detected each day.
It CAN do that, but if you have a big enough pool of water and you blast it with enough neutrinos (and the sun puts out a staggering amount of them), eventually one of them will interact with the water.
Same principle that a radioactive material with a billion-year half-life will still have detectable decays in the first minute. The half-life, or “light-year of lead” is just an average. Some of the events will happen early. And as Babale notes, there are a staggering number of neutrinos. Nevertheless, it takes a huge detector to capture a reasonable number them.
Obligatory XKCD:
Come to think of it, if you had a supply of both the reflective ultaunobtainium and the absorbtive regular unobtainium, you could make a pretty nice burning-glass. The problem with an ordinary burning-glass (solar-focusing “death ray”) is that, at best, all you can do is couple your target to the radiative surface of the Sun, and so the sun’s surface temperature (a few thousand degrees) is the highest temperature you can possibly hit. But if you make a parabolic mirror out of the ultraunobtainium, and put a lump of the regular unobtainium at the focus, you could instead couple to the core of the Sun, at millions of degrees.
One difficulty would be that, since the core of the Sun is much smaller than the photosphere, your target point would also be correspondingly smaller. And you couldn’t heat up anything but unobtainium directly (though you could still use the hot unobtainium to heat up other things indirectly).
I thought that E = pc was only used if truly massless. If it has any mass no matter how neglectable momentum would be gamma times mv. Is that wrong?
I haven’t done the math, but I suspect that in the limit pc will grow increasingly close to gamma mv
For any particle E/c is sqrt (m^2*c^2+ p^2) so as long as momentum is large relative to mc, E/c will be a decent approximation of p
And if we build it in the next 9 years, it will be a 2020’s-style death ray!
I’ll show myself out.
See the Sudbury Neutrino Observatory for an example: