Conventional Effects That Mimic Anti-gravity Effects
- Magnetic levitation suspends an object against gravity by use of electromagnetic forces. While visually impressive, gravitation itself functions normally in such devices. Various alleged anti-gravity devices may in reality work by electromagnetism.
- A tidal force causes objects to move along diverging paths near a massive body (such as a planet or star), producing effects that seem like repulsion or disruptive forces when observed locally. This is not anti-gravity. In Newtonian mechanics, the tidal force is the effect of the larger object's gravitational force being different at the differing locations of the diverging bodies. Equivalently, in Einsteinian gravity, the tidal force is the effect of the diverging bodies following different paths in the negatively curved spacetime around the larger body.
- Large amounts of normal matter can be used to produce a gravitational field that compensates for the effects of another gravitational field, though the entire assembly will still be attracted to the source of the larger field. Physicist Robert L. Forward proposed using lumps of degenerate matter to locally compensate for the tidal forces near a neutron star.
- Ionocraft, sometimes referred to as "Lifters", have been claimed to defy gravity, but in fact they use accelerated ions which have been stripped from the air around them to produce thrust. The thrust produced by one of these devices is not enough to lift its own power supply. Specifically, a special type of electrohydrodynamic thruster uses the Biefeld–Brown effect to hover.
Read more about this topic: Antigravity
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