Empirical Earth · Gravity, Buoyancy & the Air

LIGO — catching ripples in spacetime with a giant Michelson interferometer

The claim

“Gravity is unproven and 'gravitational waves' are just physicists seeing patterns in noise.”

What is true

It is the same instrument Michelson built in 1887, scaled up, and it confirms gravity is a real, dynamic field.

What is measured

LIGO’s two detectors ~3,000 km apart catch the same gravitational wave within ~10 ms, the light-travel time between them, which fixes the source on the sky.

What would show this is wrong

a gravitational-wave signal reaching the two detectors with a lag longer than their light-travel separation (~7 ms).

Sources

  1. LIGO & the first gravitational-wave detection. Twin 4-km Michelson interferometers at Hanford (WA) and Livingston (LA), ~3,002 km apart, detected GW150914 on 14 Sep 2015 (two black holes of link
  2. GW170817 — the multi-messenger neutron-star merger. On 17 August 2017 LIGO and Virgo detected a binary neutron-star merger ~130 million ly away; Fermi caught the gamma-ray burst 1.7 s later link
  3. The LIGO–Virgo–KAGRA network & catalogue. Advanced LIGO (US), Virgo (Italy) and KAGRA (Japan) observe jointly; multiple detectors localise sources by arrival-time differences, and hundreds o link
  4. LIGO built straight through Earth’s curve. Over each 4 km arm, a straight line in vacuum departs from the Earth’s surface by about 1.25 m. LIGO’s beam tubes were aligned to the light’s strai link
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