Weird discrepancy in cosmic measurements has cosmologists puzzled

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The growing crisis in cosmology

For The Week:

How rapidly is the universe expanding?

Since Edwin Hubble first discovered in 1929 that galaxies are getting farther apart over time, allowing scientists to trace the evolution of the universe back to an initial Big Bang, astronomers have struggled to measure the exact rate of this expansion. In particular, astronomers want to determine a number called the Hubble parameter, a measurement of how fast the cosmos is expanding as we speak. The Hubble parameter tells us the age of the universe, so measuring it was a major goal for many astronomers in the latter half of the 20th century.

The problem, however, is that measuring the Hubble parameter is, perhaps unsurprisingly, quite difficult. There are multiple methods for doing so, and modern observatories are coming up with different numbers depending on which method they use. It seems the number obtained based on the appearance of the universe shortly after the Big Bang is significantly smaller than the number obtained when looking at measurements involving objects closer by.

[Read the rest at The Week]

The future of transportation will (probably) not include teleportation

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Why We’ll (Probably) Never Be Able to Teleport

For Curiosity:

For many of us, teleportation would be the absolute best way to travel. Imagine just stepping into a transporter and being able to go thousands of miles in nearly an instant. It’s a staple in “Star Trek” and other science fiction, and a form of it even shows up in “Harry Potter.” In the real world, unfortunately, human teleportation may never be achievable. The reasons for that come from fundamental physics.

[Read the rest at Curiosity.com…]

In awe of the size of this black hole. Absolute unit.

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How Big (or Small) Can a Black Hole Get?

For Curiosity:

The biggest astronomy story of 2019 arguably was the first-ever image of a black hole, captured by a world-spanning observatory made up of dozens of telescopes. One big reason this achievement was so astounding is because black holes are relatively tiny compared to their mass: this black hole is 6.5 billion times the mass of our sun, but in overall size, it’s comparable to the size of the solar system. So what sets the size of a black hole, and how big — or small — can they get? And what does the size of a black hole even mean?

[Read the rest at Curiosity.com]

If the world stopped turning

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What If Earth Stopped Turning?

For Curiosity:

Earth is spinning on its axis, completing one rotation every 23 hours, 56 minutes, and 4.1 seconds. That spin brings us day and night, makes stars appear to rise and set, and contributes to the general habitability of our planet. Rotation plays a role in the tides, along with the circulation of the atmosphere and oceans. So what would happen if Earth stopped rotating? Don’t worry about “how” or “why”; just think about the end result. The consequences tell us a lot about how our planet functions — as well as other worlds in the galaxy.

[Read the rest at Curiosity.com…]

The world … er, the universe is flat!

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What’s the Shape of the Universe? A New Study Is Sparking Debate

For Curiosity:

What is the shape of the universe? The universe is everything that we can observe, so we can’t stand outside it to see if it’s shaped like a ball or a potato chip or something else entirely. That doesn’t mean cosmologists aren’t trying to figure it out, though. It’s an important question, though it forces us to expand our ways of thinking about shape. As it turns out, the answer to the question relates to what the universe is made of and how it began. The issue got some public attention recently when three cosmologists claimed the universe curls back on itself, which contradicts many other observations. So who’s right?

[Read the rest at Curiosity.com …]

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]