The gravitational field around Mars would have a slingshot effect on a spacecraft, hurling it back toward earth with additional velocity.
Its gravitational field thus bends and focuses the light from the distant object, making it appear closer than it really is.
Flying in formation, they could map the gravitational field of an asteroid or moon by monitoring tiny changes in their relative positions.
The vehicles reach about 50 miles above the Earth, so they have no need to clear the gravitational field and require much less fuel.
The hope is that the strength of the gravitational field across such short distances will be radically different from that experienced between bodies further apart.
The technique employed to find the new planet uses the gravitational field of a star like a lens - magnifying the light from a distant background star.
The gravitational field between the two black holes was so strong that it had never been possible to test Albert Einstein's theory of General Relativity in such an extreme situation.
The problem becomes less acute once they've cleared the atmosphere, but the high speeds required to escape the Earth's gravitational field (more than 6.8 miles per second) necessitate an enormous amount of energy.
At Oort-cloud distances, the strength of this combined gravity adds up to the same sort of force as that exerted by the solar gravitational field, enfeebled as it is by its remoteness from the sun.
The craft itself may not survive this, but it gives the project's engineers a chance to practise landing a spacecraft remotely on a relatively small target with a gravitational field that varies immensely from one place to another.
"This means that by watching what happens to the positions of the quasars on the sky as the gravitational field of Jupiter moves past their line-of-sight, the scientists can test other aspects of the general relativity theory, " says Professor Shanks.
Indeed, some at the meeting argued that if aliens were to use an astronomical phenomenon called gravitational lensing (in which the gravitational field of the sun bends and amplifies radio waves and light from Earth), human signals could be amplified to the point where even the light from cities would be visible.
ECONOMIST: An argument over whether to send messages to aliens
For GPS, this is an enormous issue because it turns out that the clocks on the satellites drift by almost 40, 000 nanoseconds per day relative to the clocks on the ground because they are high above the earth's surface (and therefore in a weaker gravitational field) and are moving fast relative to the ground.
Building a human-sized wormhole, for example, would require harnessing vast amounts of peculiar quantum field energy and deploying gravitational stabilizing technology that would need the resources of a cosmic super-civilization.
The coil is suspended in an external magnetic field and the current running through it adjusted so that the attraction between the two magnets balances the gravitational force on the suspended mass.
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