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.

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

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.

When you look in mirror, and see what you think is a perfect reflection. You might be looking at universe whose laws are fundamentally different.

There’s this idea that beauty is a powerful guide to truth in the mathematics of physical theory. String theory is certainly beautiful in the eyes of many physicists. Beautiful enough to pursue even if it’s wrong?

Astronomers are the worst at naming things. Dark energy AND dark matter? Who can remember which is which. But perhaps one astronomer has just fixed it, with a theory that says perhaps actually they are they same stuff.

The foundations of quantum theory rests on its symmetries. For example, it should be impossible to distinguish our universe from one that is that is the perfect mirror opposite in charge, handedness, and the direction of time. But one by one these symmetries were found to be broken, threatening to break all of physics along with them.

The search for a single number: the hubble constant, which is the rate of expansion of our universe, has consumed astronomers for generations. Finally, two powerful and independent methods have refined its measurement to unprecedented precision. The only problem is that they don’t agree. This calls into question some of our most basic assumptions about the universe.

Challenge question: if 1kg of apples is $5 and 2kg is $10, how much is -1kg of apples? The answer? Priceless. Because you could use negative-mass apples to build warp drives, travel in time, and construct a perpetual motion machine. In fact that last one will be today’s actual challenge question.

Invisible to the naked eye, our night sky is scattered with the 100s of billions of galaxies the fill the known universe. Like the stars, these galaxies form constellations – hidden patterns that echo the reverberations of matter and light in an epoch long before galaxies ever formed. These are the baryon acoustic oscillations, and they may hold the key to understanding the nature of dark energy.

Hook up an old antenna to your TV and scan between channels. The static buzz you hear is mostly due to the ambient radio produced by our noisy pre-galactic civilization. But around one percent of that buzz is something very different – it’s the cosmic microwave background radiation.

Bad ideas come and go in physics. But there’s one bit of nonsense that is perhaps more persistent than all others: the perpetual motion machine. No working perpetual motion machine has ever been experiment verified. All break the laws of thermodynamics.

The private space-race has been on for a while now. The attention has been on Space-X and Blue Origin with their reusable rockets. But there’s one private space program that’s been doing things a little differently. Richard Branson’s Virgin Galactic isn’t building rockets at all – it’s building spaceships. And I got to sit down and talk to him about it.

The power of Dark Energy may be increasing as the universe ages. Subtle clues are emerging that the accepted model for the nature of dark energy and dark matter may not be all that. We saw the first such clue recently in our recent episode on the Crisis in Cosmology. Today we’re doing a Space Time Journal Club to reveal another clue

Of all the unlikely ends of the universe, the Big Rip has to be the most spectacular. Galaxies ripped to shreds, dogs and cat first living together, then tragically separated by the infinitely accelerating expansion of space on subatomic scales. Good thing it's not going to happen. Or is it?

Have you ever asked “what is beyond the edge of the universe?” And have you ever been told that an infinite universe that has no edge? You were told wrong. In a sense. We can define a boundary to an infinite universe, at least mathematically. And it turns out that boundary may be as real or even more real than the universe it contains.

We live in a universe with 3 dimensions of space and one of time. Up, down, left, right, forward, back, past, future. 3+1 dimensions. Or so our primitive Pleistocene-evolved brains find it useful to believe. And we cling to this intuition, even as physics shows us that this view of reality may be only a very narrow perception.

We’ve been failing to detect dark matter for decades. Finally, the latest failure to detect dark matter may have actually proved its existence. One of these is true: either most of the matter in the universe is invisible and formed of something not explained by modern particle physics OR our understanding of gravity is completely broken.

How do you take a picture of a black hole and what can we learn from it? Our first ever actual bona fide photo of a black hole, made by the Event Horizon Telescope and revealed to the world in a press conference on April 10th. Since then it’s got plenty of coverage, because … I mean look at it. It’s a freaking black hole. It’s black, it’s holey, it’s everything we hoped it would be.