swansont

Do you mean if one of the objects can break in an inelastic collision? Sure. Drop a glass and it will inelastically collide with the floor, and probably break.

The HUP falls directly out of the Fourier transform between conjugate variables. As Atheist said, the use of photon recoil is just a way to visualize it, as it were.

I disagree. They more accurately reflect your ability to do well on tests (or other assignments), which is, in part, due to learning. I've seen students breeze through classes with little to no effort and get good grades, and some put forth a lot of effort and do horribly. Some students don't test well. Others only think that's the problem.

New cells use existing atoms and molecules. I echo Sayo's query. "The creation process" reminds me of this Sidney Harris cartoon - I think you need to be more explicit in step 2.

There's also the fact that the ground state energy has a finite value. The electron can be in the nucleus - it just can't stay there. (It doesn't generally combine with the proton because the weak force has a short range, and because it may not be energetically allowed.)

gradient is normal, not tangent. Not sure I understand the question regarding PE.

F = -grad(U) for conservative forces. U is potential energy.

Yes, of course we are. But not because of the acceleration we're discussing.

There will be some variation due to the eccentricity, but as that is small, so are the speed variations (which are periodic, as you say) The earth is always accelerating toward the sun, and vice-versa. The magnitude of those accelerations are different by the ratio of the masses. If I've done my calculation right, the earth is accelerating at about 6 mm/s2 toward the sun. The sun's acceleration will be almost six orders of magnitude smaller, and I'm ignoring the effects of other planets (which are cumulative, since a is a vector)

As JaKiri pointed out, the idea of lift did exist. Thus it became an engineering problem as to how to create the lift with a machine.

That's a very important point. It's the fact that we can do reactions that change a system's energy that cause the mass to changes. The equation itself doesn't guarantee it. It's the existence of forces between particles that allow the energy of the system to change.

This is a "public" forum. Though you may have intended the question to be directed to me, it is really directed to the whole forum population, seeing as it was a matter of fact and not opinion. Anyone can answer, and the point Tycho made is valid. I might have added "Doesn't anyone Google anymore?" or some other comment had my sarcastic tendencies not been dulled by a head cold.

I posted a link before.

Now all you have to do is detect it above the noise.

"Change in" is usually defined as "final - initial"

They are the same - a photon is a photon - but being "virtual" brings with it certain conditions.

10.4 minutes for a free neutron.

Free protons are stable (or have a reeaally long half-life). But protons in a nucleus can decay, and will decay, if there is an energetically favorable neutron energy level available. The half-life depends on the structure of the nucleus.

Of course there is. The normal force will have a horizontal component.

Neutrons alway beta decay into an electron, proton and antineutrino. Protons always beta decay into a neutron, positron and neutrino.