Looking for the fifth dimension with wrinkles in spacetime

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Are We Closer to Finding a Fifth Dimension?

For The Daily Beast:

In Madeleine L’Engle’s classic novel A Wrinkle in Time, the characters travel from one place to another in space using a hidden fifth dimension, which they use to “wrinkle” the fabric of space and time. In the book and upcoming movie, this travel is more mystical than it is science. However, some scientists think there might be extra dimensions beyond the four (three space plus one time) that we’re familiar with—and those dimensions might affect the way gravity works.

But how can we know for sure? One way to check uses the collision of two neutron stars, as detected by the gravitational wave observatories LIGO and Virgo in 2017.

While they found no sign of a fifth (or sixth or seventh or…) dimension, researchers—who recently posted their work on the website arXiv—were excited.

That’s because looking for extra dimensions is difficult. We only see three dimensions in space (length, width, and depth) and one in time on the scale of the everyday; if a fifth dimension exists, it has to be hiding from us. That pushes any detectable consequence into the realm of the very small—the regime of particle physics and string theory—or the very large, where LIGO and other astronomical measurements come in.

[Read the rest at The Daily Beast]

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Why physicists hate time

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Wait a second: What came before the big bang?

Not everyone thinks the universe had a beginning.

This story originally appeared in the print edition of the September issue of Popular Science. This week, it appeared online with enhanced graphics. The text is by PopSci editor Rachel Feltman and me; the art is by Matei Apostolescu.

Cosmologists used to think the universe was totally timeless: no beginning, no end. That might sound mind-melting, but it’s easier on the scientific brain than figuring out what a set starting point would mean, let alone when it would be. So some physicists have cooked up alternative cosmological theories that make time’s role seem a little less important. The concepts are as trippy as those black-light posters you had in college.

[read the rest at Popular Science]

Forging dark matter in the Big Bang

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The origins of dark matter

Theorists think dark matter was forged in the hot aftermath of the Big Bang

For Symmetry Magazine:

Transitions are everywhere we look. Water freezes, melts, or boils; chemical bonds break and form to make new substances out of different arrangements of atoms. The universe itself went through major transitions in early times. New particles were created and destroyed continually until things cooled enough to let them survive.

Those particles include ones we know about, such as the Higgs boson or the top quark. But they could also include dark matter, invisible particles which we presently know only because of their gravitational effects.

In cosmic terms, dark matter particles could be a “thermal relic,” forged in the hot early universe and then left behind during the transitions to more moderate later eras. One of these transitions, known as “freeze-out,” changed the nature of the whole universe. [Read the rest at Symmetry Magazine]

The search for magnetic monopoles, the truest north

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The hunt for the truest north

Many theories predict the existence of magnetic monopoles, but experiments have yet to see them

For Symmetry Magazine:

If you chop a magnet in half, you end up with two smaller magnets. Both the original and the new magnets have “north” and “south” poles.

But what if single north and south poles exist, just like positive and negative electric charges? These hypothetical beasts, known as “magnetic monopoles,” are an important prediction in several theories.

Like an electron, a magnetic monopole would be a fundamental particle. Nobody has seen one yet, but many—maybe even most—physicists would say monopoles probably exist. (Read the rest at Symmetry Magazine…)

Confused about the Big Bang? Start here

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The Big Bang is the central concept in cosmology — the study of the whole universe — but it can be confusing to a lot of people. In fact, it’s a little unfair: some of the confusion comes from us cosmologists. In my latest for Symmetry, I try to sift out some of the important concepts and hopefully clear up some of the confusion.

Five facts about the Big Bang

It’s the cornerstone of cosmology, but what is it all about?

For Symmetry Magazine:

Astronomers Edwin Hubble and Milton Humason in the early 20th century discovered that galaxies are moving away from the Milky Way. More to the point: Every galaxy is moving away from every other galaxy on average, which means the whole universe is expanding. In the past, then, the whole cosmos must have been much smaller, hotter and denser.

That description, known as the Big Bang model, has stood up against new discoveries and competing theories for the better part of a century. So what is this “Big Bang” thing all about? [Read the rest at Symmetry Magazine]

Finding all the matter in the cosmos — even the invisible stuff

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“Weak Lensing” Helps Astronomers Map the Mass of the Universe

By making galaxies a little bit brighter, it points the way to elusive galaxies and lets us detect that most mysterious of substances: dark matter

For Smithsonian Magazine:

In ordinary visible light, this cluster of galaxies doesn’t look like much. There are bigger clusters with larger and more dramatic-looking galaxies in them. But there’s more to this image than galaxies, even in visible light. The gravity from the cluster magnifies and distorts light passing near it, and mapping that distortion reveals something about a substance ordinarily hidden from us: dark matter.

This collection of galaxies is famously called the “Bullet Cluster,” and the dark matter inside it was detected through a method called “weak gravitational lensing.” By tracking distortions in light as it passes through the cluster, astronomers can create a sort of topographical map of the mass in the cluster, where the “hills” are places of strong gravity and “valleys” are places of weak gravity. The reason dark matter—the mysterious substance that makes up most of the mass in the universe—is so hard to study is because it doesn’t emit or absorb light. But it does have gravity, and thus it shows up in a topographical map of this kind.

The Bullet Cluster is one of the best places to see the effects of dark matter, but it’s only one object. Much of the real power of weak gravitational lensing involves looking at thousands or millions of galaxies covering large patches of the sky. [Read the rest at Smithsonian Magazine]

BICEP3: Revenge of the telescope

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Dusting for the fingerprint of inflation with BICEP3

A new experiment at the South Pole picks up where BICEP2 left off

For Symmetry Magazine:

When researchers with the BICEP2 experiment announced they had seen the first strong evidence for cosmic inflation, it was front-page news around the world. Inflation is the extremely rapid expansion of space-time during its first split second of existence, proposed to explain a number of puzzling properties of the universe, making the BICEP2 results a really big deal. Over the following months, though, the excitement evaporated: After combining their data with other experiments, the BICEP2 team showed that most or all of the signal attributed to inflation was likely produced by galactic dust inside the Milky Way.

But traces of inflation could still be hiding in the data, and that’s why scientists haven’t given up yet. BICEP3, the upgraded version of BICEP2, began collecting data yesterday. The first observations using the fully updated equipment will run through November. [Read the rest at Symmetry Magazine]