[ejobozkv] Communication by gravitational waves

Create a gravitational wave emitter for broadcasting to the universe.

Gravitational waves are easily generated and travel at the speed of light.  Unlike electromagnetic waves, they are not blocked by material in the way, e.g., the planet earth.

Place a cylindrical or spherical mass on a plane.  The plane's slope is mechanically controlled causing the mass to roll back and forth in a timed sequence corresponding to the message being broadcast.  Repeat the message many times so that the receiver can separate signal from noise using the Fourier transform.  (The little rolling ball has to compete against the natural background noise of, say, black hole mergers.)

It is curious that relatively large gravitational waves (if using a large mass) can be generated by seemingly very small adjustments to the plane.  Where does this energy come from?

Similarly, a pendulum which can be stopped.  Maybe something involving flowing water between basins, but I'm not convinced that'll be as energy efficient.

For this application, we want the repetition period of our emitter synchronized with TAI not UTC.

If willing to deal with manually moving a mass, a car is probably the most massive object a regular person can easily move.  Even easier, though less massive, is moving one's own body.  These could be fun group activities.  Dance Dance Revolution (DDR).

Absent such deliberate broadcasts, what would an alien astronomer observe about gravitational radiation emitted from earth?  Perhaps someday we will build fantastically sensitive gravitational wave observatories and discover that the gravity channel is and has always been full of aliens broadcasting to each other.  We didn't see anything in the electromagnetic spectrum because communicating via EM was universally considered stupid.