swansont

We had a gamma/beta badge and a neutron badge (later combined into one) that we had on whenever we were inside the fence that cordoned off the cyclotron. Those were turned in when you left and swapped out periodically (monthly?) to be read. I never had occasion to see anything turn black, though. When we were running a radioactive beam into our lab, we had the pencil-shaped dosimeters that we could read ourselves, to measure current dose. I also used a digital dosimeter that beeped as it counted each 0.1 mSv when we were running an experiment with a large background.

By what reckoning was Fermat's last theorem proven in ten years? Fermat wrote his little note in 1637!

I used Ci when I was teaching for the Navy. Since then, I've been doing mostly atomic physics, so it really hasn't come up a whole lot. Besides, a Bq is a dps, so it's pretty boring and useless. (it reminds me of a government program, for some reason) I did get mixed up with the whole Sievert vs REM thing, but avoided it mainly by staying away from the hot spots when I was at TRIUMF. Zero dose is zero dose, no matter what the scale...

Somehow I think using a scifi movie - especially one where "alien technology" is used to get around physical limitations - to demonstrate physics principles is a bad idea. Here are some examples of what NOT to try to explain in movies, using actual math and physics.

This was on a repeat of "House" I saw the other night (new TV show in the US) It's called a myoclonic jerk. The conjecture given on the show is that sometimes, when you fall asleep your heart rate and breathing slow too quickly, and your brain interprets this as dying rather than sleep, so it "kick starts" you. It's TV, so who knows how well they did their research. More, but of course, on the web you get both wheat and chaff. lots more from the national institute of health One thing they (NIH) mention in that it can happen from hypoxia (lack of oxygen to the brain), so the conjecture that the brain sees its supply diminish and causes the jerk isn't without at least some merit, in my layman's opinion.

A pinhole camera works basically because the hole screens out any nonparallel rays. If you draw a ray diagram, you'd see that every point on the objects maps to only one point on the image, if the pinhole is infinitely small. It's not, so there will be some blurring. But if the object is far away, the blurring is minimal. You can see a diagram showing this here

"EM" and "ionizing" are not mutually exclusive. All photons are EM radiation. Photons above an eV or so (blue end of visible, and above, in frequency or energy) can be/are ionizing. Microwaves and mobile phones do not emit ionizing radiation, and so would not be detectible with a G-M tube.

Scientific theories have to do more than explain - they have to predict. I can explain just about everything with invisible pink fairies, and you can't disprove their existence. But it's useless as a theory, as there is no predictive power, and nothing that is explained that isn't already. (feel free to substitute the deity of your choice into that) It's hypothesis for the moment, and to promote it as anything more, as JaKiri implied - is dogma.

You will cause rotation because there is a torque, but you may also cause center-of-mass motion. It depends on the specifics of the problem.

Can't tell you why spin exists, but it does. And so some materials can have the unpaired spins line up, and the atoms form a regular structure, so that the fields add up and are permanent (below the Curie temperature, i.e. the thermal motion doesn't disrupt the alignment)

It would work if the "antifreeze" had a large heat capacity, so it would be able to release a lot of energy without cooling very much. Which means it's not antifreeze in the same sense as your car's radiatior, where you lower the freezing point of the liquid. It's not so important, as you rightly point out, that the liquid not freeze. You want to keep the metal warm. The problem with running the scoop under water to warm it is that you get ice crystals forming on the ice cream. Yecch. I have wondered why they don't inductively heat the metal - put on a system like electric toothbrush chargers with a heating element in the scoop. Keep it warm so it scoops better, and it's sealed up so there's no shock hazard.

Ah, yes, the old "it's all guesswork, so my guess is as good as anybody's" canard. Haven't heard that one in a little while. It's so nice to reminisce around Christmas and New Year's day.

One problem with this situation is that, ignoring air resistance, launching from a cannon into an elliptical orbit has the tendancy to make the projectile return to its place of launch, i.e. the orbit passes through the earth. Air resistance may modify this, but I wouldn't be surprised if you needed a course correction at some point to "circularize" the orbit.

I assume Vox means initial velocity, x component, and the poster is unfamiliar with using either the "math" markups or the "sub" tags. v0x

Start by drawing a free-body diagram.

How would spinning mercury make a mirror, in space?

It's not so much about whether or not the lifter technology works - it appears to. The question is how useful it is (thrust/mass, and whether it requires an atmosphere to work) and why some people tout it as "antigravity."

(emphasis added) Two issues jump to mind: 1. Lasers don't give you a parallel beam - they do diverge. 2. How do you aim the weapon? The image you see is where the target was when the light left, not where it is now, and how do you figure out how to aim where the target will be, at large distances?

Not easily deflected. Neutron magnetic moment = 9.6623707e-27 ± 4.0e-33 J/T It's not zero.

How so? Especially once you've accepted the term "real numbers."

OK, now we're in the "speed of thought" thread, but that's...OK. I actually was thinking of this thread when I said I gave some examples.