No, once more: there is no such thing as absolute velocity. What's Sirius got to do with it? We're talking Newtonian physics here: at the scale of this experiment, the influences of Sirius, Sun or Moon may be safely neglected.
So you say. If I must consider the motion of the planet, then why not?
Talking about wind being a velocity makes no sense.
Good, you agree, though it is treated in this thread (countless examples) as if it were, and the the reason I say the treadmill is a failure.
Wind is moving air; the air has a velocity relative to the ground, and since the air has mass we can use this relative movement as a source of energy.
No, the energy comes from the sun. The air is a conveyor. The air molecules have momentum, that is it. The energy is not "relative to the ground". The air molecules have momentum, the remainder is interpretation, and dependent upon circumstance.
The air alone is not the source of energy: the energy is coming from the movement of a mass of air relative to the ground.
Without a ground, there can be no extraction, then?
The energy can be re-circulated by thermal contact, a process of indeterminate velocity. What are the relative velocities of clouds of random objects?
There is not a constant relation between the velocity of the air and the energy we can extract from it: if we want to extract more energy from a wind at a given speed, we use a bigger propeller.
I could take a snapshot of the wind driving a cart, add up all the vectors (all dimensions and local turbulence) and get 10kmh. A moment later, the same process may yield 4kmh. "Wind Velocity" is notional.
Energy can be extracted in other ways, without moving components, and there is a limit to the extraction. See Maximum Power Theorem.
No, the situations of ball hitting spaceship and spaceship hitting ball are identical.
If we are on Earth and throw a ball at a house, the ball does not have constant velocity: it is accelerated by gravity. Since the ball is accelerating, it does not define an inertial frame of reference. Whatever frame of reference we choose, we will see the acceleration of the ball in a vertical direction, so it will look like a ball being thrown through the air.
Let's say I agree that they are the same.
I asked you before to tell me how it could be otherwise. How can you make the house hit the ball, without changing something?
A few years ago, I worked on a small magnetic "shuttle". A 3.5kg mass, traveling along a track at 30m/s. I did the calculations from the ground.
OK, I could put myself on the shuttle, and do it from there, so I invert the appropriate signs. Pointless, but OK.
If now I get the bright idea that that is "the same as" holding the shuttle and moving the base, do you see any problems? The base, I estimate from memory, would have a mass of at least 3000Kg.
The views do remain "equivalent" only if you change nothing in the process. Yes, two "equivalent views" but also two "physical models" (systems).
So,
Sirius does have more effect upon the cart, than the theorem itself. Do you appreciate that an idea can be correct, but trivial?
Have you considered the possibility that your interpretation could be wrong?
Yes, but ask Spork.
