seedload wrote: Correction, an EARTH sized bottle of antimatter to levitate a car.
I suspect Enginerd is correct. If 1000kg of matter creates 9,800 newtons of force here on earth, then 1000kg of antimatter should (if this hypthesis is true) create -9,800 newtons. the combo of the two would be 0 and thus G neutral, no? Put it on the sun, the moon, whatever, still balanced forces. ICBW.
I would think that it is the Earth that produces the gravity and the applied force, and it would take a identical mass and volume/ standoff distance of antimatter to balance it out. Consider the Earth and Moon. There is a point between them where gravity balances out to zero. It is a matter of mass and distance . With a negative gravity antimatter would would have to be below the car. The antimatter would push away from the Earth and also push away from the car. A car near the surface of the Earth is hopeless.
But, a satellite very high above the surface of the Earth would benefit from the distance. Say a satellite ~ 30,000 miles above the Earth's surface may only need a chunk of antimatter weighing a few billion tons. to hover in place. Of course then you have to worry about the Earth leaving you behind, and subsequent acceleration from the now dominate chunk of antimatter. And remember, the antimatter will always be trying to accelerate away from the Earth, so I don't know if you could maintain any balance, especially if you got out of the 'car'.
If you are talking about some type of gravitational shielding, not opposition, it might be different.
To error is human... and I'm very human.