swansont

In 1-D it's the dot product with the unit vector.

You are mixing up the gravitational force and the net force. The gravitational force never changes. The net force, which dictates the acceleration of the object, is the vector sum of all the forces - gravitational and normal force, and any others that might be present.

Apple is mainly a hardware company, not a software company. They don't want you buying hardware from someone else. When they sell their OS separately, it is to people who already own a Mac. The downside is that you can't buy really cheap hardware. The upside is that you don't have as many problems from having cheap hardware (especially from multiple sources that end up being somehow incompatible).

We just had this discussion. Energy doesn't get used up, so there is no need for a source.

Mathematically a shadow is a projection.

The horizontal motion doesn't affect g. The incline affects the vertical acceleration because it adds a force along that axis. vertical acceleration and g aren't the same thing. Neither are "horizontal motion" and "inclined plane."

We have to be looking at the appropriate time, and they have to be sending. If intelligent life arose somewhere that was then sending signals 10 million years ago, we wouldn't see them - we weren't looking then.

Because somebody already builds such a system, and they don't want to go into that business and try to compete.

The acceleration in the direction of the slope is not the same as the gravitational acceleration. it's going to be g* sin (inclination angle) In the vertical direction, you no longer have just g as an acceleration, you also have the contribution from the vertical component of the normal force, which will be g*cos(inclination angle). So the vertical acceleration will end up being g(1-cos(inclination angle)).

The speed is the magnitude of the velocity. If the (instantaneous) velocity is zero, so is the speed.

When you discuss velocity, it always has to be relative to a reference. The ball, after it is thrown, is moving 70 mph relative to the train, because that's what was stated. The train is moving 70 mph relative to the groundm which was also given. If the ball was thrown backward, it is now stationary (in the horizontal axis) relative to the ground. It isn't any more complicated than that. And there's really nothing here that YT hasn't already said.

Almost identical. There are some reaction rates that depend weakly on mass, and thus vary slightly for different isotopes.

I missed that - some people are talking about solar cells, and some are talking about solar sails. Different items. I was thinking "sails" when I responded. But all objects reflect light to a certain degree, though presumably solar cells are optimized for absorption, and sails for reflection.

No. The force is not zero - the "centrifugal force" does not act on the earth. There must be a force acting on the earth, else it would travel in a straight line, per Newton's first law. Centrifugal force is a pseudo force that appears to exist when one is in an accelerating frame of reference, and one still expects Newton's laws to hold. It's also the reaction force to a centripetal force, so it's exerted by the earth, not on the earth.

I think that's shown to be untrue, though, since the Bose-Einstein condensate theory (AFAIK) doesn't modify the EM interaction, and it behaves as advertised. But I'm not sure of the magnitude of the hypothetical effect.

Not only that, it requires Nitrogen bombarded by neutron to form it (typically in the atmosphere), and intake by organisms that intake the atmospheric Carbon. A rock from Mars would be lacking in the Nitrogen atmosphere or the Carbon intake. Even on Earth, Carbon dating is limited to a subset of organic samples.

Right. No excess energy, but they still have energy. But virtual particle "borrow" energy from [math] \Delta E \Delta T > \hbar[/math] The EM force isn't going to stop. Why would the gravitational?

Go here. Pay special attention to the "Doppler shift explanation" section.

They didn't carbon-date the rock. The rock from Mars wuldn't have travelled that fast for very long, and the time dilation would only happen during the travel. And 160,000 mph is only about .00024c, so the effect is minimal.

Iron, nickel, amd cobalt are ferromagnetic elements with Curie points well above room temperature. Gadolinium is ferromagnetic below 16 C. Dysprosium is ferromagnetic below -188 C. Other materials will be attracted to or repel external fields, but will not reatian the properties when the external field is removed. Diamagnetic materials have electrons whose dipoles align with the external field. Paramagnetic materials' dipoles anti-align.