PBS_SpaceTime

It turns out that "nothing" is one of the most interesting somethings in all of physics.

To repeat the space time maxim: it’s never aliens … until it is. So let’s talk about ‘oumuamua.

How did life on Earth get started? Did life on Earth originate on another planet? Either Mars, or in a distant solar system? Could Earth life have spread to have seeded life elsewhere? Let’s see what modern science has to say about the plausibility of panspermia.

The days of oil may be numbered, but there’s another natural resource that’s never been touched, Asteroids.

Since the discovery of the Higgs boson, physicists have searched and searched for any hint of new particles. That search has been fruitless. Until, perhaps, now. Today on Space Time Journal Club we’ll look at a paper that reports a compelling hint of a new particle outside the standard model: the sterile neutrino.

Our laws of physics are equations of motion, along with some associated constants. We’ve talked about the symmetries of these equations, and how they lead us to conserved quantities. But this is just the tip of the theoretical iceberg - sometimes investigating the symmetries of these equations predicts entirely new physics. The standard model of particle physics is a remarkable example.

Entropy is surely one of the most intriguing and misunderstood concepts in all of physics. The entropy of the universe must always increase – so says the second law of thermodynamics. It’s a law that seems emergent from deeper laws – it’s statistical in nature – and yet may ultimately be more fundamental and unavoidable than any other law of physics.

The second law of thermodynamics – the law that entropy must, on average, increase – has been interpreted as the inevitability of the decay of structure. This is … misleading. Structure can develop in one region even as the entropy of the universe rises. Ultimately, entropy is a measure of the availability of free energy – of energy that isn’t hopelessly mixed in thermal equilibrium.

The Sun: an entity worshipped as a god throughout time and across cultures. The source of all life and sustenance for our little blue space rock, and also a force of unthinkable destructive power. But soon humanity will reach out its collective hand and come closer to touching the Sun than we ever have before with the launch of the Parker Solar Probe.

Quantum field theory is notoriously complicated, built from mind-bendingly abstract mathematics. But are the underlying rules of reality really so far from human intuition? Or are physicists just showing off? For better or worse, the physicists are definitely on the right track. We know this because the predictions of quantum field theory stand up to experimental test time and time again.

We live in an unusual age – the age when the stars still shine. We should count ourselves lucky – nearly all of future history will be dark. But events will still unfold in that long, cooling darkness, and civilizations may endure. So how will the universe and its far-future denizens spend eternity?

Black Holes should have no entropy, but they in fact hold most of the entropy in the universe. Let’s figure this out.

Billions of galaxies, each with billions of stars, each with … rather a lot of particles in them. And then there's dark matter, black holes, planets, and the particles and radiation in between the stars and galaxies. But… is the universe actually made of stuff? An increasing number of physicists view the universe – view reality as informational at its most fundamental level.

Between them, general relativity and quantum mechanics seem to describe all of observable reality.

On this Space Time Journal Club we look at how gravitational waves can be used to search for extra dimensions of space!

Physics seems to be telling us that it’s possible to simulate the entire universe on a computer smaller than the universe

Why strings? What are they made of? How did physicists even come up with this bizarre idea? And what’s all this nonsense of extra dimensions?

The silence of the galaxy and the resulting Fermi Paradox has perplexed us for nearly 50 years. But our most recent surveys of the Milky Way finally allow us to draw scientific conclusions about the depressingly persistent absence of aliens.

Let me tell you a story about virtual particles. It may or may not be true.

Some see string theory as the one great hope for a theory of everything – that it will unite quantum mechanics and gravity and so unify all of physics into one glorious theory.

With the large hadron collider running out of places to look for clues to a deeper theory of physics, we need a bigger particle accelerator. We have one - the galaxy.

The laws of physics are the same everywhere in the universe. At least we astrophysicists hope so. After all, it’s hard to unravel the complexities of distant parts of the universe if we don’t know the basic rules. But what if this is wrong? There is a hint of evidence that the fundamental constants that govern our universe may evolve over time, and even from one location to another.

The Kepler mission has determined that terrestrial planets are extremely common, and may orbit most stars in the Milky Way. But these planets are difficult to directly image because they’re dense and small. Our Sun is about ten billion times brighter than Earth. Train a distant telescope on us, and it will be overwhelmed by the Sun’s rays. So how can we find terrestrial planets around stars light

In this video, we discuss the reports about the detection of a pair of supermassive black holes orbiting only one light year apart from each other. Studying the dance of these giants should tell us a ton about how black holes grow.

Lurking in the depths of the mathematics of Einstein’s general relativity is an object even stranger than the mysterious black hole. In fact it’s the black hole’s mirror twin, the white hole. Some even think that these could be the origin of our universe.