Don’t be surprised to see flashing lights behind you and hear a police siren while you read this blog post. And it’s not because that slightly illegal prank you pulled in your youth has finally caught up with you.
Yep. Sitting in your chair, sipping your coffee or munching on your favorite snack, you are moving at a pretty ridiculous clip.
We experience day and night because the Earth rotates. Being an inhabitant of the Earth and subject to its gravity, that means we are spinning along with it. Standing at the equator, you would be moving at the rate of just over 1,000 miles per hour. In the middle latitudes, where most of the human population resides, it’s roughly two-thirds of that, or six-t0-seven hundred miles an hour.
And your mom always complained about you being so slow to get ready for school in the morning!
We can’t stop there, though. We all know the Earth revolves around the sun. How fast does it have to move to do so? Pretty damn fast, as it turns out. In order for the Earth to make a complete trip around the sun in the span of a year, at a distance of ninety-three million miles away from the burning ball of hydrogen, it has to move approximately 66,000 miles per hour.
You’re really booking it! No wonder the cops are after you!
But, back to the headline of this post: time travel. Why is this movement through space important?
Let’s look at one of the most famous examples of time travel from popular culture: Doc Brown’s first experiment with Einstein the dog in Back to the Future. In the movie, Doc sends his pooch, strapped into the famous DeLorean, one minute into the future to arrive at the exact same spot. Yet, in order to do that, he would not only have to travel through time, but space as well. Consider how far you move, sitting in your chair, in the span of a minute.
Rotationally, spinning along with the Earth, you travel ten or eleven miles in that single minute. In addition, you’ve moved about 1,100 miles with the Earth following its orbit around the sun!
“All right then,” you say. “Maybe we can travel through time in exact-year increments.”
Interesting thought, but we’re not done calculating your speeding violation.
In addition to the Earth rotating and revolving around the sun, the sun is also moving at a pretty astounding pace, and dragging all of us with it in the general direction of the star Vega, within the constellation Lyra. That motion is calculated at roughly 43,000 miles per hour. Yet, even that isn’t all. The sun and our solar system also orbit within our Milky Way galaxy as it spins. Our speed as we waltz around the mysteries at the center of our galaxy? Merely 483,000 miles per hour.
That’s over 8,000 miles per minute. And we’re still not done.
The Milky Way itself is also moving, hurtling away from a universal central region we associate with the Big Bang. That speed? 1.3 Million miles per hour, or over 21,500 miles per minute.
So, in a single year— one trip around our sun— the Earth is displaced several billion miles through space from its starting point across a number of vectors of direction.
In order to travel through time to visit our own past or future, we must travel vast distances through space as well. I turned 50 years old this past year. If I wished to witness my own birth, I’d have to not only pass through those years of time, but also half a trillion miles of space!
Don’t get me wrong, I adore time travel stories— I’ve written a few! And Back to the Future is one of my all-time favorites, but it’s also fun to think about the bigger picture of time travel and what it entails. Our universe is an incredibly complex mechanism that we’ve only barely begun to understand. Maybe one day we’ll crack the code that will allow us to bounce around willy-nilly through space and time. Until then, we’ll just have to let our imaginations wander the reaches and laugh at the exploits of Doc Brown and Marty McFly.
“I’m sorry, Officer. I had no idea I was going that fast.”
I remember fondly watching reruns of Star Trek when I was a kid (I’m not quite old enough to remember them airing for the first time, although we were born in the same year!) and Scotty was always one of my favorite characters. His engineering miracles pulled the Enterprise and her crew out of the fire more often than most. Sometimes it seemed like every other episode, Kirk demanded something of Scotty and the ship that had never been done before, and Scotty never failed to deliver.
Warp speed, Star Trek’s version of faster than light travel, was how the Enterprise zoomed around the galaxy. Star Wars had hyperspace. They folded space in Frank Herbert’s Dune stories. Stargates, wormholes, black holes, and numerous other devices have been used in science fiction to get around nature’s cosmic speed limit: the speed of light.
The speed of light is around 186,000 miles per second. Light moves fast enough to circle the Earth more than seven times a second! Why would anyone need or want to travel faster than that? The unfortunate answer to that is space is mind bogglingly big.
The Earth seems very large to us, sitting on its surface. Yet, when we look around in space, we see that the Earth is quite tiny on the cosmic scale of things. And the distances required to move from planet to planet, or star system to star system, are truly enormous indeed. As I mentioned in the last post, it takes radio transmissions, traveling at the speed of light, about fourteen minutes to reach Curiosity on Mars. And Mars is our closest neighbor!
The distance between stars is measured in terms of lightyears; in other words, the distance light can travel in a full year of time. That’s about six trillion miles. The closest stars which are similar to our sun in size and temperature, are ten to twenty lightyears away. In contrast, the first Earthlike planet which astronomers discovered late last year, orbits a star around 600 lightyears away. Think about that. If aliens on that world had a telescope powerful enough to see us, they would be viewing the Earth as it was 600 years ago. Those aliens might be watching the coronation of Henry V in England! In order to communicate with those imaginary aliens, we would have to wait 1,200 years for a message to make that round trip.
In order for science fiction stories to involve extraterrestrials, the vast majority of them have employed some method to circumvent the lightspeed dilemma. In the book I’m currently working on, I’m using a method involving extra dimensions than the three we’re familiar with, but I think I’ll save that discussion for another post. I do hope someday humans can solve the lightspeed riddle. The universe is so vast and interesting, it would be a shame not to be able to explore it.
Beam me up, Scotty!