# How much more precise would LIGO have to be?

The planets and a spinning black hole both drag their local frames and thus generate gravitational waves The amplitude should be proportional to the size of the celestial body, while the frequency of those waves should be related to how fast the object is spinning.

Let say I wanted to hear our planets gravitational "song". How precise would. LIGO have to be to measure the gravitational waves of the earth so they could be converted to an audible form?

• According to this answer, Earth's revolution around the Sun emits around 196 watts in gravitational waves. We won't be able to build a detector (in space) that could detect that radiation anytime soon. ;) – PM 2Ring Apr 10 at 12:06
• Rotating objects symmetric about their rotation axes do not emit gravitational waves. This pushes the power of the emitted gravitational waves in the cases you consider to absolutely negligible numbers. – Void Apr 10 at 16:23
• But the earth is not symmetric. Even if it was wouldn't have to emit some sort of gravitational wave as a result of frame dragging. – user33995 Apr 11 at 2:15

## 1 Answer

It depends what you mean by "gravitational emanations". There is a significant amount of "gravity gradient noise" at low frequencies ($$<20$$ Hz) caused by the test masses being pulled back and forth by changes in gravitational field associated with seismic motions of the ground around the detector. This noise is similar in magnitude (at low frequencies) to the seismic noise itself (once it has been damped by the test mass suspension and quadruple pendulum arrangement). Arguably therefore, this has been "detected" already.

But perhaps this isn't what you mean. Perhaps you mean the gravitational waves associated with the Earth's rotation and its small departure from spherical symmetry, or the waves associated with its acceleration caused by the Moon and Sun? All of these effects are at frequencies many orders of magnitude below LIGO's sensitivity window (roughly 10-3000 Hz) and could never be detected on Earth because of the aforementioned seismic and gravity gradient noise which grow with decreasing frequency.

• So we would first have to park it in orbit no get away from interferance? Assuming you were to do that, how sensitive would LIGO havE to be to detect the earth's gravitational waves? – user33995 Apr 11 at 2:20