The many satellites used in the Global Positioning System are constructed so that their onboard clocks are synchronized with clocks on earth. In order for this to be possible, the satellite clocks are manufactured so that if placed in the same inertial frame as clocks on earth, the satellite clocks will run at a different rate. This is necessary to correct for what relativistic effect(s)?

1. There is no such thing as a “GPS satellite.” The GPS system depends on precise atomic clocks, but they are located in Boulder, Colorado.

2. They have to be adjusted only for their altitude above the earth, which affects the rate at which the clocks run, according to the theories of Gravity of Newton and Einstein.

3. They are adjusted to compensate for Time Dilation (Special Relativity) and for the effects of differing gravitational acceleration on clocks (Einstein’s Theory of Gravity, aka General Relativity). For satellites of earth, these effects are very small, but have to be corrected for.

4. They don’t need to be adjusted at all, but do have to be carefully designed to work in the vacuum of earth orbit. Relativistic effects under these conditions are too tiny to notice.

5. They move so fast in orbit that extreme Time Dilation has to be allowed for.

When electromagnetic radiation passes through a conductor, its presence is detected by the fact that it oscillates the electrons in the conductor, producing an AC current... as in an antenna. How do we detect that gravitational radiation is passing through an object?

1. The wave causes clocks to stop, momentarily.

2. The wave bends laser beams so that they move in a circle.

3. The wave causes a very tiny oscillation in the local temperature of the system the wave passes through.

4. The wave causes clocks to run much faster than normal.

5. The wave causes conduction electrons to spin in tiny circles.

6. The wave causes physical objects to change very slightly in size.

7. The wave causes clocks to run much slower than normal.