The fabric of the Universe, spacetime, is a tricky concept to understand. But we’re up to the challenge. Image credit: Pixabay user JohnsonMartin.

Ask Ethan: What Is Spacetime?

It’s the most fundamental fabric of the Universe itself. But how does it work?

“‘Space-time’ — that hideous hybrid whose very hyphen looks phoney.”
-Vladimir Nabokov

When it comes to understanding the Universe, there are a few things everyone’s heard of: Schrödinger’s cat, the Twin Paradox and E = mc². But despite being around for over 100 years now, General Relativity — Einstein’s greatest achievement — is largely mysterious to everyone from the general public to undergraduate and graduate students in physics. For this week’s Ask Ethan, Katia Moskovitch wants that cleared up:

Could you one day write a story explaining to a lay person what the metric is in GR?

Before we get to “the metric,” let’s start at the beginning, and talk about how we conceptualize the Universe in the first place.

Quanta, whether waves, particles or anything in between, have properties that define what they are. But they require a stage on which to interact and play out the Universe’s story. Image credit: Wikimedia Commons user Maschen.

At a fundamental level, the Universe is made up of quanta — entities with physical properties like mass, charge, momentum, etc. — that can interact with each other. A quantum can be a particle, a wave, or anything in some weird in-between state, depending on how you look at it. Two or more…