Fr. Z's Blog

That is… gravitational waves exist.

Last night during my sermon for Ash Wednesday, I used an image from Augustine’s Confessions.  Augustine, who authored the unforgettable “our hearts are restless until they rest in Thee”, described us and our love as working like gravity, which in the thought of the ancients was a force within a thing that sought to go to its proper place of balance in relation to all other things.  “Amor meus pondus meum” (conf 13, 9, 10) said Augustine, “My love is my weight” drawing the restless soul to God, the only source of lasting peace. We are all made in God’s image and likeness, made to act as God acts.  He reveals something of His will to us.  When we obey Him we act in accordance with the way He made us and what He intended for us.  All things that live and move and have their being must come to rest in God or forever be in conflict with themselves and the cosmos.

But I digress…

From New Scientist:

Revolution in physics as gravitational waves seen for first time

We just turned the volume up on the sky. Gravitational waves, the booming echoes of massive objects moving all over the universe, have been detected for the first time by LIGO, the Laser Interferometer Gravitational-Wave Observatory, which was recently upgraded.

Gravitational waves are predicted by Einstein’s theory of general relativity, which says that massive objects warp space-time around them. When these objects accelerate, they make gravitational waves: ripples in the fabric of space-time that spread outward, like the wake left behind a boat. [Much as, I think, massive Mass properly celebrated and participated sends “waves” through the cosmos.  Save The Liturgy, Save The World.]

We have been pretty sure they exist for a while – their presence was inferred indirectly as far back as 1974 – but none had been observed directly.

In a press conference today at the National Press Club in Washington DC, which was simultaneously broadcast to the media and other members of the team that made the discovery, the LIGO collaboration announced that they had finally caught a wave.

[…]

This historic signal was produced by a pair of black holes roughly 1.3 billion light years away, one 29 times the mass of the sun and the other 36 times, orbiting each other and then merging into a single black hole.

LIGO’s dual detectors, based in Hanford, Washington, and Livingston, Louisiana, felt the tremors on 14 September 2015 at almost the same instant. Their sensors registered space-time expanding and contracting by as much as a thousandth of the size of a proton – a tiny distance, but 10 times larger than the smallest unit LIGO can measure. [Amazing.]

This was a doubly lucky find: officially, the experiment wasn’t scheduled to begin taking data until four days later, on 18 September, in a run that continued until 12 January 2016. The signal arrived while the detectors were in “engineering mode”, making sure the instruments were running smoothly.

A second stroke of luck was the nature of the signal: it seems that black hole mergers happen more often than we expected.

All objects emit gravitational waves when they orbit each other, including Earth orbiting the sun. But as these two black holes circled each other, the energy they lost to gravitational waves was enough to bring them much closer together – causing them to distort space-time further and emit even more gravitational waves.

That set them on track to collide and merge into one bigger black hole. “It’s a runaway process,” says Frans Pretorius, of Princeton University in New Jersey. “The closer they get, the faster they spin.” Near the end, they were whirling so fast that each orbit lasted just a few milliseconds. [WHOA!  One of these stars is 29 times the mass of your Earth’s yellow Sun and the other 36 times?  And the orbit was in milliseconds?  It is nearly impossible to grasp the force of this… and yet to the least of the angels in the angelic hierarchy such a thing is less consequential to him than a plastic yoyo to us.]

When they eventually merged, the single black hole that remained was 62 times the mass of the sun – three solar masses lighter than the two original black holes combined. That missing mass all went into creating gravitational waves that fluttered space-time like a sheet.

“The total power output of gravitational waves during the brief collision was 50 times greater than all of the power put out by all the of the stars in the universe put together,” said Kip Thorne of Caltech, one of LIGO’s founders. “It’s unbelievable.”  [“Praise ye Him, O sun and moon: praise Him, all ye stars and light.”]

At first, the resulting bigger black hole was lumpy instead of round, and getting rid of the lumps caused it to emit more gravitational waves. It then settled into a sphere and grew quiet. [Each one of us has an influence on the Body of Christ.  Lent should help us to get rid of our lumps so that we can help the Body run more smoothly.  This is not always a gentle process.]

By translating the frequency of the gravitational waves into sound waves, you can actually hear the signal. Physicists call it a “chirp“: a rise in pitch and volume as the black holes circle each other faster and faster.

The chirp from this new signal was very short – “just a thump”, said LIGO spokesperson Gabriela Gonzalez at the press conference.

Listen to the pair of black holes colliding – as detected by LIGO:

UPDATE 12 Feb:

There is a great article at the New Yorker which describes this discovery in more detail along with its tantalizing implications. HERE

Note well that the discovery of the “chirp” came on 14 September 2015. That is the 8th anniversary of Benedict XVI’s Motu Proprio Summorum Pontificum going into effect.

Portentous!