CAUTION: Mind-bending concepts ahead... Time Travel Conundrums.

I just finished writing a time travel story, titled The Sorcerer, and so this stuff is on my mind. Let's talk about two problems with logic regarding time travel.

First, let's dismiss the idea of time travel to the FUTURE. We can already travel to the future. For example, every time you are unconscious, you awake in the future having experienced no passage of time. Also, if you get in a spaceship and travel really fast (like half the speed of light), or if you go near a black hole where there is extraordinarily intense gravity, we know that time passes more slowly for you than for people on Earth. Depending on your speed or the intensity of the gravity, you could leave Earth for what seems like only one year to you, but when you return home, hundreds of years have passed on Earth. This method isn't practical, but it is a proven, observable fact resulting from Einstein's theory of relativity.

Even more interesting conundrums come in when we think about traveling to the PAST. Of course, we have no practical concept of ever being able to travel to the past. Probably won't ever happen. However, in the spirit of die-hard sci-fi fans, let's say it IS possible. There are two issues that most time travel stories struggle with.

Issue #1: if jumping back in time is possible, a new timeline has to be created at the moment any person or object arrives in the past. By "new timeline," I mean a new universe. Yes, jumping back in time requires the existence of infinite parallel universes (and there are at least five plausible scientific theories that suggest the existence of multiple universes, including the concept of “daughter universes” suggested by the theory of quantum mechanics).

Why does a new timeline (universe) have to be created upon the arrival of any person or object from the future? Because that arrival changes the events that are happening in the past. Let's say I have a time machine, and I send an iPhone (or a rock, or a hamster, or a person) back in time 100 years. The moment that iPhone appears, it triggers a sequence of events that are different from the other sequence of events that happened in those 100 years.

But that original 100-year series of events has already happened. It's impossible to undo something that has already happened (the disappearing photograph in "Back to the Future" is silly for this reason).

So, the appearance of the object in the past has to create a new timeline (a new universe). Anything can happen in the new timeline. Even if no one ever finds the iPhone in the past, random events will make it so that different events happen in the next 100 years in that timeline.

This is also why, if you could jump to the past, you could never get back to your own place in your original timeline... because the moment you arrive in the past, you are in a new universe. Even if you live another 100 years, you will not end up in the same place you started from. Jumping to the past is basically a one-way trip.

Issue #2:Jumping back in time (or forward, for that matter) is really space travel. Almost all time travel stories ignore this obvious fact. The Earth is moving... really fast. Even if we only consider the Earth's rotation, you are moving at 465 meters per second (1,037 miles per hour) at the equator (a bit slower if you are not at the equator). But remember, the Earth is also orbiting the sun, the solar system is spinning with the entire Milky Way galaxy, and the galaxy is hurtling through space as the entire universe expands. If we only consider our solar system moving in a huge orbit around the center of the galaxy, you are moving at 230 kilometers per second (514,000 miles per hour). Seriously.

So, if I have a time machine and I instantly jump back in time one second, I will appear at least 230 kilometers from where I started, probably somewhere deep in the Earth's crust (ouch) or somewhere beyond the Earth's atmosphere (ouch again). If I jump back in time 100 years, I'll appear 450.6 billion miles from where I started.

See the problem here?

A time machine has to be capable of transporting you across vast expanses of space and placing you at your destination with mind-boggling precision.

Pretty cool stuff, huh?

Image credit:
Clock in the stars - Midjourney