Yearly Archives: 2016

Gravitational waves detected. Einstein was right … again

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Clifford Will

Clifford Will is the Editor-in-Chief of Classical and Quantum Gravity

As if celebrating the 100th birthday of general relativity weren’t enough, the LIGO-Virgo collaboration has provided “the icing on the cake” with today’s announcement of the first direct detection of gravitational waves. At press conferences in the USA and Europe, and in a paper in Physical Review Letters published afterward, the team announced the detection of a signal from a system of two merging black holes.

The signal arrived on 14 September, 2015 (its official designation is GW150914), and was detected by both the Hanford and Livingston advanced detectors of the LIGO observatory (the advanced Virgo instrument in Italy is not yet online). It was detected first by Continue reading →

Life-altered cosmologies

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Jay Olson

Jay Olson (lecturer at Boise State University) seeks to minimize a convenient reserve of free energy.

A few assumptions regarding life and technology translate into new cosmological solutions.

For the universe as a whole, will the next several billion years be any different from the last several billion years? What kinds of things could make it different? Something like a phase transition or a big rip would definitely break up the monotony, but that kind of thing seems unlikely to happen any time soon. Barring that, we can expect cosmic acceleration to push a bit harder, galaxies to get a bit dimmer, black holes to get a bit fatter.  It’s mostly a boring, predictable, stable time for the cosmos.

Then again, there is something a little different happening now. It hardly seems worth mentioning. It takes a while for the universe to produce enough heavy elements to form earthlike planets. And then, judging by our Continue reading →

The Universe is inhomogeneous. Does it matter?

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Yes! The biggest problem in cosmology—the apparent acceleration of the expansion of the Universe and the nature of dark energy—has stimulated a debate about “backreaction”, namely the effect of inhomogeneities in matter and geometry on the average evolution of the Universe. Our recent paper aims to close a chapter of that debate, to encourage exciting new research in the future.

Although matter in the Universe was extremely uniform when the cosmic microwave background radiation formed, since then gravitational instability led to Continue reading →