"here endeth the lesson"????
How did the topic get left so far behind?
currawong:
A geo-synchronous orbit allows a satellite to maintain a position over the earths surface because its radial speed matches the rotation of the earth. Ie one orbit every 24hrs. The satellite has no idea what the earth is doing underneath it, all it knows is the centrifugal force due to its speed is almostly perfectly equal to its weight.
On the way to the moon, there is a process of acceleration underway the whole time. For the first phase, the ship is under the influence of earths gravity and is slowing down as soon as the rocket engines cease to fire. Eventually, it enters an area where the influence of the moons gravity is predominant. Now it is increasing velocity again. The whole package is always subject to acceleration due to the sum total of the gravitational influences on it and therefore the men inside experience "weightlessness".
Are you serious with the moon mass remark? Of course not!! You know perfectly well the moon, having less mass of its own, exerts a lesser gravitational force upon the mass (unchanged) of the astronaut, who weighs less as a result...!!
Soulman to futher define what you said, Mass is predominantly a measurement of the amount of matter of a body;
Inertial Mass (IE inertia) is a measure of a bodys resistance to changes in velocity.
In a closed environmment (ie the airliner) the downward force (lift) produced by the birds will offset the reduction of weight on the floor by the birds being "in flight". This is in keeping with a High School physics principle called "Conservation of Energy".
Try picturing a helicopter inside the airliner (I know it's unreal but then so's some of the physics being discussed here) instead if you don't agree. There is no net change in energy besides the "fuel" being used by the birds or whatever being converted to waste. How could there be?
Also, don't forget, it's not just the "downwash" but the "suction" effect on the ceiling of the aircraft of the air being pulled downward.
If there was, then we would have massive savings in fuel costs being enjoyed by the airlines... all the passengers seats being suspended in the cabin by helium balloons like that Larry guy in LA with the Darwin Award. Trolleys "floating" down the aisle, etc, etc.
Jumping up and down in a subway train and not flying off the back of the train is a different effect in principle.
Birds flying through a C-5 from one end to the other are a totally different effect to the original question.
As for Superman\'s abililty to fly, this is a totally different prospect.
You see, in the early 20th century, he
couldn\'t actually fly, he could only "leap one-eighth of a mile; hurdle a twenty-Story building . . . raise tremendous weights . . . run faster than an express train.”
By the \'40s or so, with comic-book competition heating up, Superman\'s strength and powers began to change for the better.
Initially his abilities were put down to having been born to a race that lived on a planet with a gravity well stronger than ours. This seemed to keep the punters happy.
Years later, someone noticed that he seemed to have no difficulty in changing direction in mid-leap. The yellow sun/red sun theory came into play and soon Superman could fly, rather than just jump a long way.
No one ever bothered to explain the physics involved in dealing with the force of gravity needed to allow such proportionally more powerful acts of strength or, indeed, in creating a starship that could escape such gravity.