- How is the Kerr metric still used in modern black hole observations like the Event Horizon Telescope?
Gravitational Waves
Ripples in spacetime from accelerating massive objects.
- How did the discovery of the first binary pulsar at Arecibo lead to confirmation of gravitational waves?
- How did Russell Hulse first notice that PSR B1913+16 was actually a binary pulsar rather than an ordinary one?
- Why does a shrinking orbital period between two neutron stars count as evidence for gravitational waves?
- How closely did the observed decay of PSR B1913+16's orbit match Einstein's prediction?
- How many years passed between the Hulse-Taylor discovery and LIGO's direct detection of gravitational waves?
- What astrophysical event produced the gravitational wave signal LIGO detected in September 2015?
- How small was the displacement LIGO's mirrors measured, and how did the detector achieve that sensitivity?
- Why did Einstein himself doubt gravitational waves could ever be observed?
- What produced the gravitational wave signal LIGO detected on 14 September 2015?
- How small was the mirror displacement LIGO had to measure, and why was that so difficult?
- Why did Einstein doubt that gravitational waves could ever be detected?
- How did LIGO's team verify the signal was real and not a false alarm?
- How precise does a LIGO detector have to be to register a gravitational wave, and what does that precision compare to physically?
- What did the September 2015 chirp actually sound like, and what event produced it?
- What role did Barry Barish play that Weiss and Thorne, as theorists, could not have played themselves?
- Why was gravitational-wave astronomy considered a niche, underfunded pursuit for two decades before the 2015 detection?
- What made GW170817 the first confirmed multi-messenger astronomical event?
- What is a kilonova, and what did its spectrum reveal about heavy-element formation?
- How much gold did the neutron-star merger produce, and why is that significant for where gold on Earth originated?
- How quickly did observatories worldwide respond once the gravitational wave and gamma-ray burst were detected?