Breaking the Speed Limit

We can all agree – 299,792,458 m/s is pretty slow. Time to break physics.

If there are any physicists reading, now would be a good time to stop reading. Also, there are might be a few spoilers for Interstellar ahead.

The speed-of-light is a speed limit for the universe. It’s the speed that photons themselves travel, the very fastest speed that events can traverse the vacuum of space. And if we (as a society) know one thing, it’s that speed limits were made to be broken.

One of the interesting things about faster than light (FTL) travel is that it involves travelling backwards in time. I’m not going to pretend that I know why this happens, but can basically say what it is. Things that are very big (like supermassive black holes) distort the fabric of space-time. All objects do this – we call it gravity. But very very big objects don’t just warp space – they warp time as well. Again, this happens in Interstellar. Half the crew spend 3 hours on a planet inside the time dilation zone (my new favourite phrase) of a supermassive black hole, and when they get back to the mothership the rest of the crew has aged 23 years. This is great if you want to preserve living things for years, but not so great if you get left on a spaceship for 23 years.

But the cool thing is – you don’t need a supermassive black hole to distort space-time in this way. You can achieve the same effect by going really, really fast. And thus we enter the world of special relativity.

One of the cool things about GPS satellites is that they’re the only modern computers that need to factor general and special relativity into their system clocks. They go so fast that they very, very, slightly warp space-time and make themselves go slower (in time terms). The above graph shows this effect – with speed relative to c, the speed of light and time being length of second onboard compared to length of an observer’s second. And as you get to c itself, time stops.

And if you continue this graph past the speed of light (theoretically) time goes backwards.

So I’ve been brainstorming some ways that we could break this number, and will try to find the fault in each of them. Although it is worth saying, some of these methods aren’t actually breaking the speed of light – they just get from A to B faster than light could. Which according to our seriously trippy physics, is basically the same thing

1.  Wormholes

This is one of the two classic sci-fi ways of getting around space fast. The idea of a wormhole does exist in ‘real’ science, but we are yet to actually find one – or prove the existence of one.

A wormhole (or an Einstein-Rosen bridge) is essentially a hole in space-time. According to string theory, there are 11 dimensions – 3 spatial, 1 dimension of time and another 7 ‘weird’ or extraspacial dimensions. It is through these dimensions that a ‘tunnel’ could conceivably exist, allowing us to jump vast distances through our 3 dimensions in relatively short times.

2.  Very Long Stick

This is the classic speed-of-light conundrum. You get a stick a light-minute long and give it a poke. Hypothetically, this would transmit a poke down a 1 light-minute long distance almost instantly.

But…modern physics disproves. This episode of Radiolab explains how even in solid objects, all movement has a time delay. That time delay happens to be the speed of sound in that object. And if we Google the speed of sound in steel…

6100m/s.

Approximately 0.00203471% of the speed of light. Dammit. And even if we use a rod made of diamond (speed of sound 12000m/s) we’re still only at 0.0040027691% of the way there. And that light-minute-long diamond stick, if it was 10 by 10 cm, it would cost about $26,000,000,000,000 (26 trillion dollars). That’s £16,536,915,720,000. So, you might need more than a Kickstarter to try that one.

3.  Whirl the Very Long Stick around Your Head

This would work – you get that stick 1 light minute long. Then you whirl it around your head. If it’s spinning at 1/60 rpm, the end of it will be going at about 113,019,091 m/s – 37.69911083%. Closer! So if we spin at 0.04366666666 rpm, then we get to 100%! So if we can get to 0.04366666667 rpm, then we will have broken the speed of light!

Or not. According to Real Science, the stick would distort and break as it accelerated more and more. Also, it would take lots of energy to get a 5 thousand tonne stick spinning at the speed.

4.  Travel Through the Nether

According to Minecraft logic, if you travel through the Nether (hell dimension) in the x or z (non-vertical axes) planes, travelling 1 metre is equivalent to 8 metres in the normal world (Overworld). So all you have to do is accelerate to a little bit more than 1/8 of the speed of light, then we’ve broken the speed limit. There’s only one problem.

That’s in Minecraft. Dammit.

5.  Warp Speed

This is the other classic sci-fi way of getting around. You invent a new branch of physics that allows you to accelerate a ship through some other dimensional weirdness to get much faster than light speed. Only that would basically involve re-writing the laws of physics. Even more than anything else in this article.

6.  Teleportation

Current rules teleportation involves transmitting the data to a point where it is reconstructed by whatever quantum machine, Star Trek style. So if we presume that the quantum data is being transmitted by radio waves, they are going at the speed of light. You could might be able run a quantum data cable (whatever that is) through a wormhole to another point in space. But that would be a Nether-like transmission from two re/deconstructor stations, not a beam-me-up-Scottie type of teleportation. And is cheating.

7.  Time Travel (sort of)

Is it me, or is the physics getting dodgier as the article goes on? If you travel to a place using cryo-storage, or radio wave teleportation, or whatever, and then time-travel back to just after you left, that would work. Only it involves time travel.

8.  Do a Gravity Assist around a Black Hole

This is what the crew of the Endurance try in the film Interstellar. They need to get from A to B, with B being on the other side of a supermassive black hole, with not enough fuel to get there conventionally. So they do a dive into the black hole, past the event horizon (apparently it’s a ‘passive’ black hole, so that works) and out the other side. If you could actually do that, you would in theory surpass the speed of light as you go into the black hole. But I think that would involve going dead on into the singularity, not skimming the surface. And you would have to dive into a black hole. Headfirst. And try to get out again. Good luck with that.

9.  Just Get a Really Big Engine

Obviously. If you just get a bigger and bigger engine, you wouldn’t actually be able to break the speed of light. As you get closer and closer to c, the speed of light, the amount of energy you need to go faster increases exponentially. And the amount of energy needed to accelerate from a speed very slightly less than c to is actually infinite. So no matter how much rocket fuel you are using, you can’t break the speed limit.

10. Mess Around with Space-Time

Believe it or not, this is what NASA are currently working on. The rule is that physical matter can’t travel faster than light through spacetime. So using some creative (by which I mean probably bogus) physics, they’ve managed to use that rule to their advantage. They can (or can’t, but want to) create a bubble of extra space time around the object they’re moving. Then you move the object so that it’s moving at, say 0.6through the bubble. Then, using whichever branch of creative physics you want, you move the bubble through regular spacetime at 0.6c. So relative to the spacetime bubble, the object isn’t breaking the speed of light – but relative to us, it’s moving at 1.2c. Three cheers for NASA and creative physics.

The problem is, at time of writing, it doesn’t work. Making the spacetime bubble doesn’t really work, and getting any object up to even 0.51c would take a lot of energy, and so far they’re only trying to move individual quarks. So don’t go and book a NASA FtL holiday anytime soon.

So it turns out, you can’t break the speed of light. We’re stuck within the confines of the future light cone. Or are we?

Taychons are entirely theoretical particles, that can go faster than light. There are lots of physicists who condemn the idea of taychons, with lots of problems with the actual idea of faster-than-light travel – breaking the chain of causality being the main one. So we might actually be able to break the speed of light and travel backwards through time. But on the internet, however…

Scwoom (generic time travel/warp speed noise).

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3 thoughts on “Breaking the Speed Limit

  1. The easiest way to go back in time is to pass through the event horizon of a black hole. If going faster than light-speed means going back in time, and because the event horizon marks the distance from a black hole where gravity = speed of light, then everything inside a black hole goes back in time.
    Now all you need is some negative-mass matter, which, since likes attract and opposites repel with gravity, would push you back out. Alternatively, you could create your own gravity waves to counter that of the black hole.
    Either way, you might end up re-emerging earlier than you had entered (or something).
    Man, gravity is weird…

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    • Gravity is indeed weird. I get how using a black hole to accelerate past light speed would work, if it didn’t involve going into a black hole. And even if negative-mass matter or gravity waves were theoretically real, I prefer to go with insanely wild fake physics than almost real physics (unless it almost almost works).

      Like

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