J.C.MacSwell

Even in Newtonian mechanics the forces remain the same and do not reverse with time reversal. Attractive forces remain attractive, and repulsive forces remain repulsive.

Sorry. Bad joke.... 28 billion is twice 14 billion which is roughly the time from the apparent Big Bang. If your assumption is correct about expansion and entropy increasing being linked, then we could very well be in a contraction stage but not know it as our brains would be in reverse.

Didn't we have this discussion 28 billion years ago, except this time we are having it forwards?...or is it backward this time?

Thanks... the angular momentum referred to is quantized and also non-classical, correct? In String theory it would be assumed to be in extra dimensions? Any room for the photon to be hiding in there? (I know the last answer is no, because that is not what we call a photon...but all the little quantized bits and pieces seem to be conserved)

So the photon's energy and momentum is absorbed...what happens to it's spin??...is this absorbed as well?...I'm thinking this should be conserved as well...somehow...

Well... I've certainly managed to fend off a 5 ton boat (and much larger in calm conditions), moving at slow speed, from a dock or wharf... It's all a matter of how hard you push, for how long, and how fast it is moving/converging. a=F/m

Well, if they're not there now and neither is the former moon, what else can one conclude??

Hardly makes it worth while.

from above: "explaining why they never venture far from the particles producing them" Doesn't that imply a distance limit to the Coulomb forces? And if they fizzle away exponentially in time, why is it an inverse square law?

Doesn't the best theory we have as to how things all started violate conservation of energy in a pretty "blatant" manner?

Only got that far, but that's an interesting way of looking at it. It probably falls outside the definition of "natural selection" (just a guess, as I'm not an expert) but in many ways it's the same thing.

If the true wind disappears you have no energy source but your momentum (kinetic energy) relative to the ground. Since you still have drag your device will eventually come to rest. Also, you certainly can go upwind at faster than windspeed. (been there, done that, as has Sisyphus in iceboats...unless his iceboat was a real beater ) As for the bolded, the device would "know" it is moving over the ground, as the energy source it uses to maintain it's speed or accelerate is the kinetic energy of the wind relative to the ground, and the energy it expends in traction would be vehicle relative to ground. So it would "know" if it was true or apparent wind.

The old "paired molecules splitting and meeting back together after traveling different paths" explanation leads to problems. It has erroneous assumptions leaving it only partially correct. Most sails can be made to work quite well. There really is no debate outside of how best to explain things. Newtonian explanations are correct if the right assumptions are in place. Bernoulli's Principle is based on certain idealized assumptions and is in agreement with and based on Newton's laws.

Well, we know we have done it in iceboats...sailed with the downwind velocity vector greater than the wind velocity...and two iceboats on opposite tacks can maintain their combined c.g going straight downwind at greater than windspeed... Are the turbine blades accomplishing essentially the same thing? ' Have to think about it... Now this makes sense. The propeller must be variable pitch. It must be maintained by dynamic braking on the wheels, which drive the propeller which seemingly gathers energy...even though at windspeed the "relative to vehicle" energy source is the road, not the wind. The blades simply push with more net force than the force of the dynamic braking, using the energy of the wind relative to the road, even when the vehicle speed matches the wind and there is no available wind energy relative to the vehicle. Actually it wouldn't have to be variable pitch either, even at the start, though it would be more effective. Energy is a very relative thing.

No. I meant upwind. Is there something unique about sailboats? I have an iceboat, fairly common design, that will go faster than the windspeed. In light air it will go upwind much faster than downwind. While it will not go directly upwind, it gets there by tacking, and the speed made good to windward is greater than the true windspeed in many conditions. I can't see how you could maintain downwind faster than the wind though.

I don't see anything controversial. It has to be fairly efficient to go upwind faster than the wind, but it certainly can be done. At some point the drag increases too fast for the increase in available wind energy, but this does not necessarily happen at the same speed (while opposite direction) as the wind. "Impossible" would be having it work in no wind, even after pushing it to get started. Also, a flat plate can generate lift, though it is not very efficient.

Worse case scenario is we calculate the trajectory to be on path to hit us, we come up with some wonderful plan to get it off course, execute it perfectly through a heroic international effort just in time, then realize it would have missed us... just prior to our compete and utter demise. (dibs on any movie rights and royalties)

Just think about this for a second. Why does the space ship not get pushed up against the astronaut in his orbit? (Same reason as explained by the previous replies, they are in free fall together)

If any two separated points, R1 and R2, are on the x axis and are simultaneous in the rest frame, they will be simultaneous in the moving frame if and only if the relative movement is orthogonal to the x axis. (ill worded, see Swantsont below) Events on the x axis would not be simultaneous in both frames unless the relative movement is orthogonal to it.

You may want to re-think your assumptions. The OP stated that the friction coefficient would be the same in each case.

I volunteer as treasurer. Send me the $20 and I'll let everyone know when we have enough for the first flight.

So event 1 and is in event 2's past, and event 2 is in event 1's past and they can transmit information instantly between them?

The explanation sounds weak, but what do you expect from a guy that subdivides every time he's indecisive? Hopefully he came up with something better in the "Other Worlds".

More mass and closer to the earth?

Not as effectively, though I think it can still work well when a cold drink "sweats". A cold drink can still be below the dew point on a hot dry day, can it not?