Einstein was right about ripples in spacetime!


Gravitational waves are real, and scientists have detected them. In the video above, PBS Space Time explains the discovery by researchers at the Laser Interferometer Gravitational-Wave Observatory (LIGO). From the New York Times:

A team of physicists who can now count themselves as astronomers announced on Thursday that they had heard and recorded the sound of two black holes colliding a billion light-years away, a fleeting chirp that fulfilled the last prophecy of Einstein’s general theory of relativity.

That faint rising tone, physicists say, is the first direct evidence of gravitational waves, the ripples in the fabric of space-time that Einstein predicted a century ago (Listen to it here.). And it is a ringing (pun intended) confirmation of the nature of black holes, the bottomless gravitational pits from which not even light can escape, which were the most foreboding (and unwelcome) part of his theory.

More generally, it means that scientists have finally tapped into the deepest register of physical reality, where the weirdest and wildest implications of Einstein’s universe become manifest.

Below, NASA's animated simulation of the black holes merging and releasing the gravitational radiation (background here):

above image credits: R. Hurt/Caltech-JPL Read the rest

"Squeeze the butt, squeeze the legs, breathe..."


Depending on whether your sound is on or off, this fellow is either painfully enduring or tremendously enjoying high G-force training. (YouTube) Read the rest

A gravity map of the Moon

Gravity isn't uniform. Denser planets and objects in space — that is, things with more mass to them — experience a stronger pull of gravity. But even if you zoom in to the level of a single planet (or, in this case, our Moon), gravity isn't uniform all the way around. That's because the mass of the Moon isn't uniform, either. It varies, along with the topography. In some places, the Moon's crust is thicker. Those places have more mass, and thus, more gravitational pull.

This map, showing changes in density and gravity across the surface of the Moon, was made from data collected by Ebb and Flow — a matched set of NASA probes that mapped the Moon's gravitational field before being intentionally crashed on its surface last December. By measuring the gravitational field, these probes told us a lot about how the density of the Moon varies which, in turn, tells us a lot about topography.

You can read more about the probes (and see some videos they took of the lunar surface) at the NASA Visualization Explorer. Read the rest