Everything moves. We know of no object – not one – that doesn’t spin on its own axis while also whizzing through space. It’s a hurry-up universe.
Speed often provides clues to an object’s nature. For example, our planet travels at a devilishly fast speed of 66,600 miles per hour. Interestingly, every Solar System body must move at roughly this same speed when it’s our distance from the Sun. Therefore, anything that collides with us – like the Geminid meteors this Tuesday night, December 13 – zoom at this velocity too.
But are they traveling alongside us, like adjacent horses on a carousel, or meeting us head-on, like in a game of chicken? Since comets and their debris can orbit in any direction, some do barely catch up to us from behind and streak slowly through our sky. Next week’s meteors hit us sideways, which makes them impact at around 22 miles per second: still rather slow. (Look for them any time after nightfall – although a bright Moon will limit their numbers.)
By contrast, August’s Perseid meteors slam into us head-on with a ferocious combined speed – theirs plus ours – of nearly twice our orbital velocity: 37 miles per second. Suddenly it makes sense that, on any given night, meteors are much faster after midnight. Those are the ones hitting us head-on. That’s because our part of Earth then faces forward, in the direction that we’re traveling.
Once in a Blue Moon, something hits us with a seemingly impossible speed. Then we know that it must have been freshly whipped like a slingshot by an encounter with Jupiter, or else that it’s an intruder from beyond the Solar System. Cosmic rays are like that. They’re too fast to be from around here. But even within our galaxy, there’s a speed limit. It’s 600 miles per second. If anything were to go faster, it would escape the Milky Way.
We can access a faster realm only by observing other galaxies. The universe’s expansion means that for every million light-years of distance, galaxies rush away from us 14 miles a second faster. This is called the Hubble Flow (even though Edwin Hubble was a haughty control freak who reportedly never flowed with anything). Just remember 14: For example, any galaxy 100 million light-years away whooshes at 14 x 100 = 1,400 miles per second. Simple.
Do the math, and galaxies around 13.3 billion light-years must apparently zoom away at the speed of light: 186,282 miles per second. Do they?
Absolutely. But how can anything go faster than light? It is here that we invoke our Einsteinian escape clause. We say that the galaxies barely move. Rather, space itself is inflating. The galaxies just sit inertly, like Scrabble-players waiting for a vowel.
But how can space expand? Isn’t space nothingness? How can nothingness do anything?
Turns out that space is not nothing. There’s no such thing as nothing. (Meditate on that one, Grasshopper.) Space has properties. Virtual particles pop in and out of it. An inconceivably powerful “vacuum energy” pervades its every nook and cranny. And it’s expanding wildly.
Back in our own local sandbox, where we cannot blame squirmy space for the perceived motions of things, any increase in speed also boosts an object’s mass. Einstein insisted that a hurled baseball is a bit heavier than one sitting at home in a drawer. This is why we only compare objects when they’re all at rest in a lab. A quick brown fox is heavier than a lazy dog.
Moreover, all moving objects have kinetic energy. Make anything stop, and it suddenly releases this energy (as the dinosaurs noticed when a giant meteor slammed into their favorite Mexican beach). But when we discuss the kinetic energy of moving atoms, we give it a different name: We call it heat.
The fact that everything is moving, spinning or jiggling means that stupendous energies are everywhere. And since the universe’s total energy never decreases in the slightest, it means that the Cosmos must exist forever. It strongly suggests that the universe is eternal.
Yes, there’s much that we can infer from the endless varied motions that pervade Earth and the heavens.