Why the Earth moving is not a Time Traveller’s problem (probably)

For the 7th of December #TimeTravelAuthors question set by Julie Bihn, will be (unless any of you go back and change it) the question of the Earth moving. I shall make the case that this is not a problem at all. Or, rather, I will make several independent cases.

“But the Earth moves, so if you travelled in time, you’d end up in space.” Thoughts?

Julie Bihn‘s question for day 7 in December in the original timeline

Here are NNNN reasons why I think this might not be a problem for your Sci-Fi story.

Reason 1: Screw it. Write it the fun way anyway.

There is a lot to be said for fun stories without overthinking everything. So what if the hard sci-fi fans moan? We’re not predicting the future, we’re telling stories to entertain and amuse our readers.

Reason one is – this is not a problem if you decide it’s not a problem.

Reason 2: Gravity

In General Relativity, space-time is bent by gravity. Time passes every so slightly differently for satellites than on Earth. The difference is tiny but it does exist.

If spacetime is shaped by gravity, why should a non-standard journey through it not also be shaped by gravity? The reason you don’t end up in space is because you travel in time relative to the Earth’s centre of mass.

Reason 3: Magnets

The Earth has a strong magnetic field which contains the passage between times within itself. The reason you don’t end up in space is because of the powerful influence of a planet-sized magnet. This has the added benefit of being plausible enough to get the story onto the interesting bits.

This is pretty close to what I used in my as-yet-unnamed novel. (It’s written but I’ve got a fair bit of tightening up to do).

In this particular story, the method of time travel is through spheres which link two points in time and space. They are spheres because a hole in a three-dimensional space would be three-dimensional too. These spheres (called portals, tunnels, or wormholes depending on who you ask) are strongly influenced by magnets or even just sizable lengths of steel or iron.

Reason 4: Yeah, that’s weird we thought it would be a problem too

The reason time travellers don’t end up in space is unknown. It turns out it just isn’t a problem. Some very smart people worried about that no end but it just turned out to be perfectly fine.

There is nothing wrong with lampshading the expectation and getting on with the fun stuff of the actual story.

For those who might not know, lampshading is a trope where you recognise that the mic is in the shot and you hang a lampshade on it so we can all pretend that it is a lamp. In other words, you acknowledge the issue and then dismiss it as something the author has clearly understood and fixed. This allows us to suspend our disbelief and just enjoy the story.

Here is a TV Tropes link if you have a spare couple of hours.

Reason 5: We thought of that already.

The movement of the Earth has already been factored into the calculations. The reason that ending up in space is not a problem is that some very smart people already did the maths.

This works because the smart people are very smart and have no intention of explaining it right now because there’s not enough time.

Reason 6: The unobtainium compensator takes care of that

There is some complex or eldritch device that protects against that sort of nonsense. A bit like fuel injection systems, we don’t really know how they function but we are glad they work.

This has the advantage of possible trouble for the heroes went he device is broken, stolen, or is otherwise offline. Thus they are forced to solve the problem without time travel this time.

Reason 7: What are you talking about – there’s no such thing as absolute motion

This reason argues that the frame of reference is all wrong for that ending up in space nonsense and our time travel just does not work like that.

This is similar to reason one where we just say “shut up” and get back to the adventure. It was such an important point that I felt it deserved mentioning twice.


Your story does not have to please everyone. Strictly speaking, it doesn’t have to please anyone. We’re dealing with time travel fiction here. Hard Sci-Fi gatekeepers need not apply. Besides, those guys are probably explaining Primer to each other with interesting diagrams – we’re safe to just have a fun story.

When you write the story, you get to decide what is and is not a problem your characters must overcome. If space and planetary motion are not important to your story then don’t worry about them. It is your story, write it how you want to.

Anyway, my little rant aside, what explanations does your time travel story have? How do you solve the ending up in space “problem”? Drop a comment (or a mention) and let me know your thoughts.


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