Gravitational waves and climate change

Since early 2018, I’ve contributed multiple articles to Mercury, the membership magazine for the Astronomical Society of the Pacific (ASP). These articles are only available in full to members of ASP, but recently Mercury has put extensive previews for certain articles up on the website as enticement to join. One of those articles is my piece about the GRACE Follow-On mission, which is simultaneously a project that measures the effects of climate change and is a testbed for the upcoming LISA gravitational-wave observatory.

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The Gravity of Climate Change

For Mercury:

Orbiting spacecraft are an essential tool for mapping worlds in the Solar System, providing information about everything from landforms to magnetic fields. Repeated monitoring helps scientists measure variations in a planet as the seasons change. That’s particularly true for the planet we know best, and one that is experiencing the biggest variations of all the worlds in the Solar System: Earth.

The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission consists of twin space probes designed to measure Earth’s gravity to high resolution. That measurement is important for geology—seismic activity and other substantial shifts in Earth’s crust—but also for tracking shifts in water and ice around the world. Those variations help researchers measure the melting of polar ice, along with more subtle phenomena like the depletion of aquifers in western North America and India, for example.

In addition to its essential work measuring ice melting and climate change, GRACE-FO will test a vital component of the Laser Interferometer Space Antenna (LISA), the planned space-based gravitational wave observatory that will continue the work of LIGO and its Earth-based observatories.

[Read the rest of the preview in Mercury]

Squeezing light to detect more gravitational waves

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This article appeared in the fall print issue of Popular Science, but I missed that this article had also been published online.

Something called ‘squeezed light’ is about to give us a closer look at cosmic goldmines

Gravitational wave detection is going through an even tighter squeeze.

For Popular Science:

In 2015, scientists caught evidence of a ­cosmic throwdown that took place 1.3 billion light-​years away. They spied this binary black-hole collision by capturing gravitational waves—­ripples in spacetime created when massive objects ­interact—​for the first time. But now physicists want to see even farther. Doing so could help them accurately measure waves cast off by colliding neutron stars, impacts that might be the source of many Earthly elements, including gold. For that, they need the most sensitive gravitational-wave detectors ever.

The devices that nab waves all rely on the same mechanism. The U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO) and its European counterpart, Virgo, fire lasers down two mile-plus-long arms with mirrors at their ends. Passing waves wiggle the mirrors less than the width of an atom, and scientists measure the ripples based on when photons in the laser light bounce off them and come back. Ordinarily, photons exit the lasers at random intervals, so the signals are fuzzy.

[Read the rest at Popular Science]

Doing astronomy using gravity

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Astronomy without light

Gravitational waves let us see the invisible universe in new ways

For Astronomy Magazine:

Humans have always practiced some form of astronomy. For thousands of years, that meant observing only the light our eyes could see — either unaided or with a variety of instruments, such as astrolabes or telescopes. The 20th century brought new types of telescopes, which detect light we can’t see: infrared, X-ray, and so on.

Today, we’re witnessing the genesis of a whole new type of astronomy, and this one doesn’t use light at all. It uses gravitational waves.

Read the rest at Astronomy Magazine

A discovery that made a thousand scientists burst into cheers and tears

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Part of one of the mirror assemblies that make up the Laser Interferometer Gravitational-wave Observatory (LIGO) at Livingston, Louisiana. I visited the site in 2012 during the upgrade of the lab to Advanced LIGO. [Credit: moi]

Part of one of the mirror assemblies that make up the Laser Interferometer Gravitational-wave Observatory (LIGO) at Livingston, Louisiana. I visited the site in 2012 during the upgrade of the lab to Advanced LIGO. [Credit: moi]

It’s not every day that we get to usher in an entirely new branch of astronomy. Yesterday, members of the LIGO collaboration announced the first direct detection of gravitational waves, which are a way to study the universe we can’t see using light. Much of my PhD research involved gravitational physics, including a bit of gravitational wave work. I even visited LIGO twice because … well, why not? For that reason, yesterday’s announcement brought tears to my eyes, and I’m not the only one. This is the start of a new in the study of the universe. And here’s what I had to say about it for The Atlantic:

The Dawn of a New Era in Science

By announcing the first detection of gravitational waves, scientists have vindicated Einstein and given humans a new way to look at the universe

For The Atlantic:

More than a billion years ago, in a galaxy that sits more than a billion light-years away, two black holes spiraled together and collided. We can’t see this collision, but we know it happened because, as Albert Einstein predicted a century ago, gravitational waves rippled out from it and traveled across the universe to an ultra-sensitive detector here on Earth.

This discovery, announced today by researchers with the Laser Interferometer Gravitational-wave Observatory (LIGO), marks another triumph for Einstein’s general theory of relativity. And more importantly, it marks the beginning of a new era in the study of the universe: the advent of gravitational-wave astronomy. The universe has just become a much more interesting place. [Read the rest at The Atlantic]

Be very very quiet, we’re hunting gravitational waves

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Gravitational waves and where to find them

Advanced LIGO has just begun its search for gravitational waves

For Symmetry Magazine:

For thousands of years, astronomy was the province of visible light, that narrow band of colors the human eye can see.

In the 20th century, astronomers pushed into other kinds of light, from radio waves to infrared light to gamma rays. Researchers built neutrino detectors and cosmic ray observatories to study the universe using particles instead. Most recently, another branch of lightless astronomy has been making strides: gravitational wave astronomy.

It’s easy to make gravitational waves: Just flap your arms. Earth’s orbit produces more powerful gravitational waves, but even these are too small to have a measurable effect. This is a good thing: Gravitational waves carry energy, and losing too much energy would cause Earth to spiral into the sun. [Read the rest at Symmetry Magazine…]

 

Listening to the sounds of the cosmos

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Last year, I went to a conference in Florida to hear — and in some cases meet — some of the leading thinkers in the study of gravitational waves. These waves are disturbances in the structure of spacetime itself, and could provide information about some exciting phenomena, if we can learn to detect them. The universe as heard in gravitational waves includes colliding black holes, white dwarfs locked in mutual orbits, exploding stars, and possibly chaotic disturbances from the very first instants after the Big Bang. This story marks one of my first big magazine articles, which I wrote for Smithsonian Air & Space magazine.

The Universe is Ringing

And astronomers are building observatories to listen to it

For Smithsonian Air & Space:

Think of it as a low hum, a rumble too deep to notice without special equipment. It permeates everything—from the emptiest spot in space to the densest cores of planets. Unlike sound, which requires air or some other material to carry it, this hum travels on the structure of space-time itself. It is the tremble caused by gravitational radiation, left over from the first moments after the Big Bang.

Gravitational waves were predicted in Albert Einstein’s 1916 theory of general relativity. Einstein postulated that the gravity of massive objects would bend or warp space-time and that their movements would send ripples through it, just as a ship moving through water creates a wake. Later observations supported his conception. [Read the rest at Air & Space….]

If we could only build one huge observatory….

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Q: Suppose we can only build one big telescope. Should we look for life among the stars or the origins of the universe?

I participated in an experts’ roundtable for Aeon Magazine, in which we were asked (more or less facetiously) what single project we would support to settle either questions about the very early universe or the existence of life elsewhere in the cosmos. Of course my real answer is that we should support all the science, because discovery isn’t about looking for one thing, but seeing what new things we can find. Throwing all our money at one big project might accomplish something, but it’s a bad way to do science. But anyway, taking the question for what it is — a fun exercise in wishing — here’s my answer, along with thoughts from Ross Andersen and Caleb Scharf.