Solving the Twins Paradox

A guide to the fine art of modern debating.

So you want to be a relativist...

Congratulations!  And welcome to the club.  We need all the help we can get.

As a relativist, one of the things you’ll be called on to solve is the Twins Paradox.  That’s that thing where one twin goes out on a rocketship, and you need to explain why he comes back younger rather than the other way round because both twins have the same velocity relative to each other.

Solving the paradox can be tough work and will sometimes require all the bluster and sleight of hand you can summon.  But fear not!  This guide is here to help you come out on top in the most difficult debates.

OK let’s get started.  First up, you need to make yourself appear intelligent.  This is going to require some study on your part.  Ugh!  Yes I know, you don’t like doing that.  But don’t worry because you won’t be learning anything.  You just need to pick up the buzz words like... “Minkowski space”... “Riemannian geometry”... and “spherically symmetric geodesic surfaces” – oooh yeah, I also like that one!

Once you’ve got your phrases, scatter them throughout your discussion at a density no less than one every five sentences.

Make numerous appeals to authority.  Point out that the paradox has already been resolved by many experts and to the satisfaction of the majority. List famous scientists and celebrities who support your position.  Explain that you can only accept arguments that have been approved under peer review.  If the forum allows for it, prefix your profound responses with yawning emoticons and follow up with rolling eyes.

Deliver your replies in a sneering and condescending tone.  Belittle your opponents at every opportunity and rub any mistakes you find in their faces.  Insert as many subtle insults as you can get away with.  Tell them they should be grateful you’re spending your precious time explaining it to them.  Tell them that if they think they’re so smart, why aren’t they winning prizes and that they should go debate Michio Kaku.


At this point you’re probably saying:

‘Errrm thanks, but I already know all that because I do it all the time in my other debates.  Just tell me how to solve this frickin paradox thing.  Because right now I’m in a message board argument with some know-it-all and he’s starting to piss me off !’

OK, OK, hold onto your horses.  I’m getting to that.

Now to actually solve the paradox, the first thing you need do is look for something that makes the situation non-symmetrical.  For example, it could be that the twins experience differing amounts of acceleration.  Or that the Earth twin feels gravity.  Or that rocketboy has run out of clean underwear.  

Really, it doesn’t matter.  Once you’ve identified a difference, point to it and say it is the cause of one-way time dilation without explaining further.

Usually though, the thing you’d point at is acceleration.  So as before, mention that as the reason without further detail and then drop the subject.

If someone should ask, perhaps innocently, what would happen if there was no acceleration?  Like, if the rocket twin was already zooming past Earth at constant velocity when they synchronized their clocks...  Explain that in fact acceleration has nothing to do with it and the real cause of time dilation is due to asymmetric frame shifting.  Whatever that means.

Always surround the word Paradox with quotes.  This makes it look like the matter has already been settled and can be dismissed as self-evident.  If you’re short of time try the standard one-liner:

    ‘There is no "paradox".’

and leave it at that.

Never explain anything in simple terms when you can make it complicated.  For example, instead of describing one clock moving away from another, talk in terms of Minkowski spacetime coordinates, frame translations, and second-order Lorentz derivatives.  The benefit is that people tend to side with the majority viewpoint when confused.  This keeps you one step ahead of the competition.

Length Contraction is your friend.  Learn how to apply it when it suits your argument and leave it out when it doesn’t.  For example you could say the traveling twin experiences time dilation with respect to Earth while the home twin experiences length contraction with respect to the rocket.  Or you could use length contraction to calculate a different expression for speed and hence a different amount of time dilation.  Mix and match as you see fit.

Extremely important however: never be consistent.  Apply either time dilation or length contraction from one end or the other, but not both.  Otherwise your argument falls apart.

Or try the ‘relativity of simultaneity’ argument.  This is a principle that two events in different locations can never be occurring at the same time.  The great thing about it is that no one can disprove it.  Once again though, remain inconsistent in your application of it as you work toward the desired outcome.

Use lots of Lorentz Transforms.  Lorentz transforms make everything nicer.

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By now, hopefully you’ve blown off your opposition and the forum administrator has locked the discussion.

Pat yourself on the back :  you have just solved the Twins Paradox!


But you won’t always be so lucky.  Perhaps due to a few pesky doubters that won’t go away.  Or more likely due to a lazy forum admin.

Time to shift the discussion up a gear.  Time to bring in General Relativity.

The reason for doing this isn’t because you understand the subject but because you hope other people don’t either.  So start with a sweeping statement like:

‘The twins "paradox" is outside the realm of special relativity and needs to be solved by general relativity.’

That usually does it.

Or perhaps not.  Occasionally you’ll come up against someone who does understand the subject and can call your bluff.  They might point out that General Relativity won’t give any different results for the situation in question and that GR doesn’t have an expression of time dilation for linear acceleration without including an arbitrary distance term.

Such people can be very irritating.  But don’t panic!  You’re not trying to fool them, just your audience.

Ignore what they say and discuss the “covariant divergence of the energy-momentum tensor” and “the influence of frame dragging in loop quantum gravity”.  Throw in some tensor symbols with lots of Greek subscripts.

Probably you don’t have a clue what you’re saying at this point.  But that doesn’t matter since most people following will also be lost by now.  As before, the more confusion the better.  Recycle your earlier arguments and continue.

Appeal to the forum administrator.  Insist your opponent is breaking the rules; that the real purpose of this forum is to help students with their homework; that we shouldn’t give out conflicting information because it will end up causing a decline in our education standards, assuming that’s possible.  And therefore it is in the best interests of humanity that everyone stick with the program and that he be booted off the discussion.  Otherwise the stability and funding of the scientific world is threatened and society will fall apart.

That might work.  But then again, the admin might say he’d like to keep the discussion open because it’s interesting.  Remind yourself not to post here again.  Clearly, he doesn’t understand the modern scientific method!

In the meantime you have a problem.  Because you’re on the losing side of an argument and can never admit to being wrong about anything.

Once again though, this shouldn’t be cause for concern.  The rules of Twins Paradox Debating are unclear but it appears the winner is judged as the one who gets in the last word.  This puts you at a distinct advantage.  Because as an anonymous troll, you get to type any drivel that pops to mind, while your opponent has to think things through.

You are now in the final phase of the game.  This can drag on for weeks.  Probably everyone has stopped reading by now.  But who cares.  At some point your opponent will wonder why he’s wasting so much time talking to an idiot and will have to quit.

That makes you the winner!!  Yaaaay!!!