swansont

Magnetic forces do no work - the force is always perpendicular to the velocity vector. Thus, they cannot alone be used for propulsion.

I think he's referring to the radioactive boy scout though the article mentions radiation 5 doors away, not 5 blocks.

Assuming I did my calculations correctly, you get about 27.5 mW/g from Ra-226. Make sure that turbine is small and well-lubricated.

I'd guess that the alphas are ionizing or at least exciting the electrons above their metastable state, which means the material can't fluoresce the way it usually does.

BA in physics. MS and PhD in atomic physics.

Alphas deposit a lot of energy in a short distance. Most likely they are destroying whatever molecules that are in the sticker, rather than just exciting an electron like is supposed to happen.

"All science is either physics or stamp collecting" (or something close) is a quote from Ernest Rutherford. If you disagree, take it up with him.

The HLA gene in humans has 59 alleles - that is, 59 different versions of this one gene. The minimum population that can contain 59 alleles is 30. How could Noah and his family have possessed all of those variants? There are many example of multiple alleles in other animals, which is even more problematic if you have just a mating pair, rather than a family. It is often argued by creationists that mutations are always harmful. How does one explain this discrepancy?

11' tall - citation? The current trend of getting taller is about good nutrition. The moon is currenty receding at about 4 cm a year. To assume that it's doing so in a linear fashion is folly. But, at that rate, it would have been 40,000 km closer a billion years ago. But since the current configuration of continents and oceans gives really efficient tidal coupling, the rate at which we transferred angular momentum to the moon would have been smaller in the past. Interesting, yes; but not, I think, for the reasons you imply.

No, U-238 has a half life of about 4.5 billion years. The half life of U-235 is about 700 million years.

UF6 is a gas (under the right conditions) It's formed so that one can use gas membrane diffusion or gas centrifuge for the enrichment of uranium.

The one that was moving with respect to the earth ran slower than the one that was fixed. But, as has been mentioned, in some of these experiments, GR effects were also present - clocks that move to a weaker gravitational potential will run faster, and that may end up being the larger effect. (and there is also the Sagnac effect present because we're in a rotating coordinate system) To clarify about the acceleration - if the clocks were compared during the experiment, each one would see the other as running slow. It is only because one clock was accelerated to move fast and again accelerated to slow down that it ends up running slower than the fixed clock. There need not be any measurable GR effects for this to hold.

And rockets, and they do it all the time now with GPS satellites.

You can add to your KE if you do it right. The symmetry of losing as much energy as you gained is true for a stationary planet, but if you approach in the direction of the orbit, you can gain extra energy (the planet keeps moving away, so you spend more time/travel a longer distance accelerating toward it). The trick is that it is asymmetrical in our frame, so the energy lost is smaller than the energy gained. Here is amore complete explanation.

Consider that you need to give whatever chunk of material you want to eject the required escape velocity without frying it. "Unlikely" is an understatement.

How would you get a tidal lock with no tides? Tides are a consequence of there being elasticity in the surface of the planet/moon. As long as a force is exerted, there is a tide.

The object will tend to speed up as it approaches the earth. But unless it loses energy along the way, it won't be captured.

But to any extent this happens, it does so radially WRT the sun, and thus it doesn't exert a torque.

Technically potential energy is shared between the objects in the system, but when the masses are so different we usually "assign" the energy to the smaller. But yes, all objects affected by gravity have some amount of gravitational potential energy.

The earth rotates because it has angular momentum, and that's a conserved quantity in the absence of an external torque. We are transferring some angular momentum (and energy) to the moon through tides, so I imagine the same is happening with the sun at a smaller scale. (The moon is currently receding at ~ 4 cm/year). It doesn't take any energy to rotate - the energy is already there. It would take energy (and a torque) to increase the rotation, and energy would have to go somewhere if the rotation rate decreased.

Gravitational force is infinite in range, but decreases in strength as 1/r2

The formula you want is F=dP/dt, which i the source of the well-known F=ma, or force is mass X acceleration. But that assumes constant mass (so dP/dt =m(dv/dt), or ma), and isn't useful in this case. Rearrange it and you get F= v (dm/dt), where dm/dt is the rate at which mass is ejected and v is the speed, which is assumed constant.

Travel in 3D leads to collisions, which will tend to eliminate the particles in these orbits, over time.