Space Being Warped by Black Holes

The greatest discovery of the 21st century (so far) is leading to even more discoveries. LIGO is back online with upgrades. And it’s being enhanced by a network of pulsars.

The greatest discovery of the 20th century is probably the breakthrough that the universe is expanding, leading directly to understanding the Big Bang, the structure of the cosmos, and the fate of everything.

The expanding universe is a prediction of Relativity, one so extreme that even Einstein had trouble accepting it at first, until Edwin Hubbell provided data on other galaxies. It founded the field of cosmology.

The greatest discovery of the 21st century is also from Relativity. 

I was lucky enough to have a courtside seat to the incredible, sustained application of creative genius that led to the discovery of gravitational waves in 2015. Titanic events across the universe could now be directly observed for the first time.

In 1915 Einstein published his epoch making theory of Relativity. One of its many incredible predictions is every object in the universe gives off invisible gravitational waves. These are subatomic oscillations so tiny that it seemed it would be physically impossible to detect them.

In the nineteen eighties I begin attending a series of lectures by the the great physicist and cosmologist Kip Thorne, at Caltech. He had a clear, mathematically precise vision of a system to detect gravitational waves. He called it LIGO, which is an abbreviation for Laser Interferometry Gravitational Observatory.

Building LIGO

This was a entirely new and almost unimaginable kind of observation that had nothing to do with seeing light or x-rays other kinds of Electromagnetic phenomenon. For example, gravity waves carry information on where they came from, and pass through matter unaffected. This was a new way of sensing the universe by detecting the expansion and contraction of spacetime itself.

Kip Thorne proposed a revolutionary, very new kind of observatory that could measure disturbances in the size and shape of the universe on a scale far smaller than the width of a proton. It would enable us to measure the universe expanding and contracting from gravitational waves beaming towards us from every direction. 

The first person to think of an interferometer to measure gravity waves was Rainier Weise at MIT, who at the time did not realize that it would require invention of several new technologies to achieve this.

LIGO makes its measurements by splitting a laser beam into two and bouncing the resulting beams between two heavy mirrors at either end of a long vacuum tunnel. Tiny differences in the arrival time of the beams occur thanks to the stretching and squeezing of spacetime between the ends of the pipe. This measurement is called “interferometry”.

The incredible scope and clarity of Kip’s vision rendered every other creative genius I’ve met a touch quaint and conservative. He wanted to measure what was happening on the other side of the universe, and he had a step by step plan on how to do it.

Over time he was able to persuade other scientists and congress people that a plan to build the largest, most complex machine ever made by humans, to measure something we didn’t know for sure existed, was a great idea to spend billions on.

Each time I saw him speak, there were more insights, new plans, and concrete steps towards building LIGO. An international team of researchers was gradually assembled. But after a time, funding dried up. The only institution in the world that was willing to support research on gravitational waves was Thorne’s own Caltech, which to this day has a large financial endowment and will support extreme research.

Thorne realized that to be successful, the experimental scientists at LIGO would need a clear prediction of what they were looking for. This was a phenomena that no one had ever seen. So Kip began expanding the field of numerical relativity from a theoretical niche, to building fantastic 3-D models of spacetime that eventually became both the basis for great scientific discoveries, and part of popular culture in sci-fi movies.

Each time he presented one of these breakthroughs, it was astonishing. It was almost surreal to be sitting in the audience and see the presentation of something that truly had never been thought of before that completely changed our view of the universe. 

The first time I saw a 3D color simulation of what would happen when two black holes spiraled towards each other and merged it was almost like science fiction — astonishing!

Kip was always modest and eager to share credit. The smartest person in the room was also the most generous and collaborative.

Thorne and lead experimenter Barry Barish knew that the first two generations of LIGO would not yield anything except engineering data. Despite this, they were able to secure funding for two five mile long laboratories In Washington and Louisiana to reliably measure fluctuations in the size of spacetime that were a thousand times smaller than a proton, coming from points of origin billions of light years away.

The first detection of a gravitational wave happened during the first part of the first run of the third generation. The shape of the waveforms they detected precisely matched the model for the collision of two large black holes. This happened in 2015, but they kept it quiet for months until they were certain they had ruled out any other possible explanation before publishing. 

The discovery was announced in 2016 and was front page news in news outlets all around the world. The following year they were awarded the Nobel prize. The closest analogy to the event would be being alive in 1604 when Galileo discovered that Jupiter had moons! It was an impressive discovery with reaching consequences.

No one alive today has any idea what the knowledge of gravitational waves will help us accomplish in the future. The breakthrough brings us a huge step closer to a theory of everything and the possible discovery of other universes.

LIGO has come back on line after another round of upgrades, and the system should now be detecting black hole, neutron star, and supernova explosions almost on a daily basis, from across the entire known universe. It should even be capable of giving detailed measurements of Dark Energy.

The most-recent upgrades of both LIGO and the European version called Virgo has been to build extra 1000-foot-long vacuum pipes. With mirrors at the ends, to store an auxiliary “squeezing beam” for 2.5 milliseconds before injecting it into the interferometer. Squeezing light makes it a little more predictable and have less noise from quantum fluctuation, making the observatory more sensitive and accurate.

A Network of Pulsars

The LIGO (Laser Interferometer Gravitational-Wave Observatory) upgrade network of pulsars is an exciting development in the field of gravitational wave detection. Pulsars are highly precise celestial clocks that emit regular pulses of radio waves. By monitoring the timing of multiple pulsars spread across the sky, scientists can detect the subtle changes in their arrival times caused by gravitational waves passing through space.

This upgrade to the LIGO network will greatly enhance our ability to detect gravitational waves. By incorporating pulsars into the network, we can increase the number of observable events and improve the accuracy of measurements. Pulsars have a unique advantage over traditional detectors, as they can provide continuous monitoring of the sky and are not reliant on specific events occurring.

This upgrade is significant because it will allow us to gather more data on gravitational waves, leading to a deeper understanding of their sources and properties. It may also help us to detect new types of astrophysical objects or phenomena that produce gravitational waves.

One major hope is to pick up the gravitational signal of a collapsing star before it manifests as a supernova explosion — a feat that will be possible only if the collapse occurs somewhere in our own galaxy. Another ambition is to sense the continuous gravitational waves produced by roughness in the surface of a pulsar, a spinning neutron star that emits pulses of radiation.

This is the next phase in gravitational wave observations, one that should allow us to actually detect waves from the big bang and other large events. This will ultimately require building a space observatory, one that Thorne calls LISA. Laser Interferometer Space Antenna, set for launch by NASA in 2035.

Astronomers have only observed a single event in both gravitational waves and visible light to date: the merger of two neutron stars seen in 2017. But from this single event, physicists were able to study the expansion of the universe and confirm the origin of some of the universe’s most energetic events known as gamma ray bursts. They were also able to measure the speed of gravity, which is the speed of light, as predicted.

I was privileged to see Kip Thorne’s final lecture at Caltech where he summarized some of his accomplishments, including the only time machine design that’s been published in the scientific literature as an actual working time machine (as well as the very funny conclusion of the bet he won with Stephen Hawking on black hole energy, which involved giving Thorne a subscription to Penthouse Magazine, much to his wife’s disgust.)

There will be plenty of new and surprising science coming from LIGO, including predicting the most massive cosmic events. And black hole mergers, the oldest on record was discovered last week at the start of the new run. More here on the Caltech LIGO web site.

The whole point of science is to expand and improve on what any individual or group could do, to understand all — yet it’s important to acknowledge and remember our great individuals. Kip Thorne is one of them. I’d love to hear what he has to say about the latest discoveries.

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