Hacking Time: The Twin Paradox and Brute Force Computations

A recent XKCD comic on time complexity inspired me to create and explore a thought experiment: could we hack time to brute-force computations?

The Thought Experiment.

Imagine you have a vital secret locked in a digital vault. Unfortunately, you’ve lost the password. Despite all attempts, there is no way to recover it, so your only option is to brute-force your way in. Unfortunately, even with the world’s most powerful supercomputer, it is estimated that it would take 10,000 years to crack the password. Luckily, you own two essential things: the world’s most powerful supercomputer and a spacecraft capable of accelerating to relativistic velocities (near light speed). So, you set up your supercomputer and start the brute-forcing attempts. Then, you hop in a spaceship. You just so happen to live in a sector of our galaxy that isn’t too far from a black hole, and you take a 5-year trek close enough to the event horizon to distort spacetime but far enough out that your ship can reach exit velocity. You head back home. Back at home, more than 10,000 years have passed, and the flashing on the computer screen is the password it was successfully able to brute force.

How this might work.

As implausible as this thought experiment might sound, it is a variation of the well-established Twin Paradox. In the Twin Paradox, one twin takes a ship capable of traveling near the speed of light out into space and, after some time, comes back to Earth. While the traveling twin only experienced two years of aging, her twin on Earth aged over twenty. This is due to how inertial frames work: accelerating away from and then toward the original twin causes this effect. This asymmetry in the passage of time might be pretty useful to the traveling twin, especially if some costly computation (as measured in time) was in the mix.

Of course, there are countless issues with trying to do this. Here are just a few off the top of my head:

• Accelerating to relativistic speeds is treacherous; using such a device would kill you from radiation exposure. Low energy EMF would blue shift into high energy radiation, and even random hydrogen atoms in space would become ballistic missiles to your ship. But who knows, maybe your spaceship has special radiation shields or something.

• This would be a very lonely way to recover your password. Everyone you know or love will have been long gone. Maybe you could create a space Ark that could hold all the people and things you care about (except your supercomputer)

• Who knows what technology will exist even in 100 years, let alone 10,000? Other methods for recovering your password, such as faster computers and fundamentally new technologies, are very likely. It would make sense to create some “solved early” signal to reduce the travel window if you didn’t need to wait that long.

• It might take longer than 10,000 years. You might want to generalize the “solved” signal so that it can trigger traveling back to your home instead of assuming it is ready. This way, you can hang out near the black hole and watch the universe progress at 2000x speed.

• Keeping a supercomputer running for 10,000 years is no joke. You probably need a fancy foundation to run it or start a cult with a prophecy that you will return in 10,000 years.

That’s it. Just a goofy little thing to think about. What would you do if you could fast-forward the clock?