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]

Why falsifiability is a false guide to what is and isn’t science

I had a liberal arts education, which means that I mostly use what I learned to post nonsense on Twitter. However, thanks to my advisor, I got a solid grounding in the philosophy of science. While I’m certainly no philosopher myself, I also (hopefully) have a less simplistic view of how science works and doesn’t work than what is often presented as the “scientific method” and suchlike. For Symmetry, I got a chance to talk a little about how “falsifiability” is widely promoted as a way to tell what is scientific and what is not, and why it’s actually a poor criterion, both from a philosophical and scientific point of view.

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Falsifiability and physics

Can a theory that isn’t completely testable still be useful to physics?

For Symmetry Magazine:

What determines if an idea is legitimately scientific or not? This question has been debated by philosophers and historians of science, working scientists, and lawyers in courts of law. That’s because it’s not merely an abstract notion: What makes something scientific or not determines if it should be taught in classrooms or supported by government grant money.

The answer is relatively straightforward in many cases: Despite conspiracy theories to the contrary, the Earth is not flat. Literally all evidence is in favor of a round and rotating Earth, so statements based on a flat-Earth hypothesis are not scientific.

In other cases, though, people actively debate where and how the demarcation line should be drawn. One such criterion was proposed by philosopher of science Karl Popper (1902-1994), who argued that scientific ideas must be subject to “falsification.”

[Read the rest at Symmetry Magazine]

Seeing the unseeable: humanity’s first image of a black hole

Yesterday, the Event Horizon Telescope collaboration released the first image of a black hole humanity has ever seen. That simple-looking image represents a century of scientific work: from the first theoretical calculations describing black holes; to the earliest hints that every large galaxy contains a supermassive black hole at its heart; to the technological advances needed to network a world-spanning array of radio telescopes. When I was in college and graduate school, many people thought this very thing was impossible — I know I did. I am happy to say I was wrong then, and this picture of the 6.5 billion solar-mass black hole at the heart of the galaxy M87 is the most thrilling image of my scientific and science-writing career thus far.

the black hole at the center of the M87 galaxy, as seen by the Event Horizon Telescope

The first image humanity has ever captured of a black hole: the supermassive black hole at the heart of the M87 galaxy. [Credit: Event Horizon Telescope]

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The incredible story behind our first image of a black hole

For the first time ever, scientists have captured a direct image of a black hole. The image, captured by the Event Horizon Telescope, allows us to see something that was thought to be invisible

For WIRED UK:

A black hole is invisible by nature. One of the strangest predictions to come out of Albert Einstein’s theory of general relativity, a black hole emits no radiation we can detect, and it swallows up everything that falls on it, matter and light alike. The boundary of a black hole — its event horizon — is a border that can only be crossed from the outside to the inside, not in reverse.

So it might seem paradoxical to talk about capturing an image of a black hole, but this is precisely the mission of the Event Horizon Telescope (EHT). Today, April 10, 2019, will go down in history as the day EHT scientists released the very first direct image of a black hole.

It’s not one in our own Galactic centre, but is at the centre of the galaxy M87 – a resident of the neighbouring Virgo galaxy cluster, which is the home of several trillion stars. The feat marks the first time in history that astronomers have seen the shape of an event horizon. It’s an unprecedented map of gravity at its strongest, involving hundreds of astronomers, engineers, and data scientists from around the world.

[Read the rest at WIRED UK…]

The weird new physics of neutrinos

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Already beyond the Standard Model

We already know neutrinos break the mold of the Standard Model. The question is: By how much?

For Symmetry Magazine:

Tested and verified with ever increasing precision, the Standard Model of particle physics is a remarkably elegant way of understanding the relationships between particles and their interactions. But physicists know it’s not the whole story: It provides no answer to some puzzling questions, such as the identity of the invisible dark matter that constitutes most of the mass in the universe.

As a result, in the search for physics beyond the Standard Model, one area of notably keen interest continues to be neutrinos.

In the Standard Model, neutrinos come in three kinds, or flavors: electron neutrinos, muon neutrinos and tau neutrinos. This mirrors the other matter particles in the Standard Model, which each can be organized into three groups. But some experiments have shown hints for a new type of neutrino, one that doesn’t fit neatly into this simple picture.

[Read the rest at Symmetry Magazine]

Om nom nom: a black hole ate a star and left crumbs for us to see

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And if I can be shameless: Forbes pays according to traffic, so the more of you who click on the link below and read my stuff, the better they pay me. Ahem.

A Black Hole Ate A Star And Left Crumbs Of Light For Astronomers To Discover

colliding galaxies Arp 299

The colliding galaxies Arp 299, as seen in visible light (the background) and X-rays (red, green, and blue foreground). [Credit: NASA, JPL-Caltech, GSFC, Hubble, NuSTAR]

For Forbes:

Astronomers captured the last moments of an unlucky star that got too close to a black hole. However, they didn’t know that’s what we were seeing right away, because the whole scene of carnage was hidden by clouds of gas and dust. Now, with multiple types of observations and more than ten years of data, we have new insights into the way black holes shred stars, as reported in a new paper in Science.

Black holes, like Cookie Monster, are notoriously messy eaters. That’s good for astronomers, though, because the cosmic crumbs a black hole spills during its meal emit a lot of light. If a star gets too close to a black hole, the gravity tears it to pieces in an act known as “tidal disruption”, but only part of the star’s material actually falls in. (This is a more extreme version of the same forces that raise tides on Earth, and which destroyed a small moon to create Saturn’s rings.) The rest of the star gets channeled into a powerful jet that streams away from the black hole back into space.

[Read the rest at Forbes…]

How to find newborn planets without seeing them

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And if I can be shameless: Forbes pays according to traffic, so the more of you who click on the link below and read my stuff, the better they pay me. Ahem.

Astronomers Use The Doppler Effect To Find Three Newborn Planets

For Forbes:

We can’t witness the birth of our own Solar System, but the Atacama Large Millimeter/submillimeter Array (ALMA) is providing a picture of how it may have happened. ALMA spotted signs of three giant planets forming around a young star in our cosmic neighborhood. The technique astronomers used to study these planets is one that can be used to find other newborn worlds, and see exactly how clouds of gas and dust turn into something like the Solar System.

The star, which astronomers gave the memorable name HD 163296, is only about 4 million years old, which in cosmic terms makes it a baby. Researchers used ALMA to take detailed images of the disk of dust and gas surrounding the star, which showed three gaps. By studying the motion of carbon monoxide gas within the disk, the astronomers showed it was being moved by massive objects living in those gaps — a telltale sign of newborn planets. These findings were published in a pair of articles in Astrophysical Journal Letters.

[Read the rest at Forbes…]

Planet Nine or Planet Nein? The quest to understand the weird outer Solar System

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And if I can be shameless: Forbes pays according to traffic, so the more of you who click on the link below and read my stuff, the better they pay me. Ahem.

One Big Planet Nine, Or A Swarm Of Small Icy Worlds?

For Forbes:

The outermost Solar System is a confusing and complicated place. Once you get Neptune, the comets, Kuiper belt objects, and other small icy worlds orbit the Sun in odd patterns. A few of those, including the very distant world known as Sedna, have orbits that make very little sense compared with other Solar System inhabitants. For that reason, some astronomers think there’s a Planet Nine hiding far beyond Pluto’s orbit: a giant world roughly 10 times the mass of Earth.

But a new study by University of Colorado researchers proposed an alternative explanation. Astronomer Ann-Marie Madigan and her student Jacob Fleisig realized they could reproduce the strange orbits of icy worlds just by the way they interact with each other: no Planet Nine necessary. The idea is they sometimes swarm (in a broad sense) during their orbits, and when multiple Moon-sized bodies are in the same general region, it’s enough to kick other worlds like Sedna into their wild trajectories. It’s an eminently sensible explanation, and since two years of hunting for Planet Nine haven’t turned up anything, the hypothesis is definitely worth pondering more. However, we haven’t seen enough of these small worlds yet either, so the race is now on to see which explanation is correct.

[Read the rest at Forbes…]