I was watching a YouTube video where someone comically said they wanted to travel back in time to see dinosaurs. Brian Greene says it’s not mathematically impossible to travel back in time. But it is impossible to travel back in time, especially to long distant times, because here was not here 65 million years ago. Let me explain.
You find a fossilized dinosaur bone from 65 million years ago, buried a few feet deep in your backyard. Get a time machine, set it for 65 million years ago, and poof! But what are you aiming for? If you aim for the plot of land you are standing on in 2014, you have to realize that the dirt you call terra firma didn’t exist 65 million years ago. It came from plants and eroded rocks and ash and all kinds of things that, for the most part, hadn’t even been born or created 65 million years ago. If you somehow lock your time machine to the fossil itself, the dirt down deep where the dead creature came to rest could have been mud, or a lake, or even an ocean 65 million years ago, so when you arrive you might be under a mile or two of water. Have scuba gear and a diving bell ready.
Another problem is that the Earth’s tectonic plates are always moving. So the chunk of land you’re standing on today could have been a thousand miles north or south or east or west in the distant past. You might have found your bone in Iowa, but turn back the clock 65 million years and you could be standing in Mexico City or Boston.
So what if you used GPS? Without satellites that would be useless. Even if you had an onboard mapping system for your time machine, what determines the GPS coordinates? Magnetic north floats around, changing locations, even experiencing geomagnetic reversals every million years, give or take. So what about using due north as a point of reference? Well, since the Earth’s axial tilt is in motion, you’d have to account for the changes in that tilt over 65 million years, too.
A much bigger problem with time travel is that the Earth ‘s orbit doesn’t exactly repeat itself. We don’t find ourselves in exactly the same spot on the solar system map every January 1st. We get a little closer to the sun, a little farther away. Also, the sun is in orbit around the center of the galaxy, so even if you accounted for the changes in the Earth’s orbit, the sun would have been somewhere else 65 million years ago. As would the Milky Way. And, according to astro-physicists, the fabric of space-time itself is expanding, such that the distances between two set points in space are inherently getting farther and farther apart.
So if you traveled back 65 million years, you’d not only miss the Earth, but also the sun, possibly the galaxy, and you might even materialize in the space in between spaces.
All of this is to say that everything is fluid. So not only can you not go back in time because you’d disrupt the space-time continuum, but you’d also end up hundreds, if not thousands of light years from where Earth was 65 million years ago.
It’s like the idea that there was once a time when times were better. It’s easier to think that people got along at some point in the past, or that leaders were just, or that children grew up pure and hopeful, or that machines started up and ran just the way we expected, or that our ideal political system was fair and balanced. Those things belong in the space between the spaces, and possibly never existed themselves. There’s never been an auto pilot for life, in exactly the same way there’s no chance of going back in time to see a dinosaur.
Make a difference today and let yesterday be dead to you.