PBS Space Time

Pin-pricks in the celestial sphere, through which shines the light of heaven? Or gods and heroes looking down from their constellations? Or lights kindled above middle earth by Varda Elbereth and brightened with the dew of the trees of Valinor? Science has long pondered the mysteries of the stars. This is how we finally figured them out.

It’s been 120 years since Henry Cavendish measured the gravitational constant with a pair of lead balls suspended by a wire. The fundamental nature of gravity still eludes our best minds - but those secrets may be revealed by turning back to the Cavendish experiment. That steampunk contraption may even reveal the existence of extra dimensions of space.

This is a map of the multiverse. Or in physics-ese, it’s the maximally extended Penrose diagram of a Kerr spacetime. And in english: when you solve Einstein’s equations of general relativity for a rotating black hole, the universe does not come to an abrupt halt at the bottom of the gravitational pit. Instead, a path can be traced out again but you don't end up in the universe that you started in.

As the 19th century came to a close, physicists were feeling pretty satisfied with the state of their science. The great edifice of physical theory seemed complete. A few minor experiments remained to verify everything. Little did those physicists know that one of those experiments would bring the entire structure crashing down paving the way for the physics revolution of the 20th century.

The universe is precisely 13.8 billion year old - or so our best scientific methods tell us. But how do you learn the age of the universe when there’s no trace left of its beginnings?

From Stargate to Interstellar, wormholes are our favorite method for traveling across fictional universes. But they are also a very serious field of study for some of our greatest minds over the last century. So what’s the holdup? When do we get to wormhole ourselves out of here?

The Milky Way galaxy is relatively calm by the destructive standards of the rest of the Universe, and compared to its own very violent past. But just recently we discovered that its violent past was much more recent than we thought - and could even happen again.

In astronomy we talk about billions of years like it’s no big deal. But how can we be sure about timescales so far beyond the capacity for human intuition? Our discovery of what we now call deep time is very recent - as recent as our discovery of the true spatial vastness of our universe. And it came as scientists tried to measure the age of the Earth. What they found was shocking and humbling.

Normal maps are useless inside black holes. At the event horizon - the ultimate point of no return as you approach a black hole - time and space themselves change their character. We need new coordinate systems to trace paths into the black hole interior. But the maps we draw using those coordinates reveal something unexpected - they don’t simply end inside the black hole, but continue beyond.

If there’s one thing cooler than a black hole it’s a rotating black hole. Why? Because we can use them as futuristic power generators, galactic-scale bombs, and portals to other universes.

This episode of space time is brought to you by the information flowing through an impossibly complex network of quantum entanglement, that just happens to mutually agree that you and I exist inside it. Oh, and Schrodinger’s cat is in here too.

To quote eminent scientist Tyler Durden: "On a long enough timeline, the survival rate for everyone drops to zero." Actually… not necessarily true. If the quantum multiverse is real there may be a version of you that lives forever.