In the old days they had used the time machine to set a two-milligram test mass alongside itself.

Super-stable laser beams would flash back and forth between the test masses to measure the effect of gravitational waves on them.

More recently, it has been measured for test masses aboard the satellite Gravity Probe B to a precision of better than 0.3%.

In the other case, another possibility was considered: releasing a test mass, and observing its movement near the target asteroid.

This means that a test mass or charge will not feel any force inside the shell.

Lead sheathed in soft iron was our test mass.

That ten billion metric tons of neutronium, now, that you were using for a test mass.

The majority of modern gravimeters use specially-designed metal or quartz zero-length springs to support the test mass.

Absolute gravimeters provide such measurements by determining the gravitational acceleration of a test mass in vacuum.

This type of gyroscope uses a pair of test masses which are driven to resonance.