# T is for Timey-Wimey

I’ve always loved the ‘timey-wimey’ stuff, both in fiction and in science. It’s something so basic, part of the structure of reality, yet the more closely you examine it, the stranger time becomes. This is kind of a long winded blog post, and it has a lot of equations in it, which some people find scary, but if you bear with me you’ll find the brain-‘splodey cool bits. Full disclosure – it’s *not* my field of expertise, which means there are undoubtedly parts where I’ve run off with the ‘shiny’ and ignored the actual point. Just doing the best I can with what I have…

## Science

### Relativity

The first, most well known, source of scientific temporal weirdness is Special Relativity. Everyone knows (or at least recognizes) the basic equation:

We’ve all heard that this leads to ‘time dilation’. The formula for time dilation is:

If v (the speed the object is moving) reaches c (the speed of light in a vacuum) then you have a divide by zero error, infinite energy, basically that doesn’t happen.

If v is less than c then your denominator is less than 1, and the two ts don’t match. Your two ‘observers’ experience different amounts of time between the two observed events (whatever they happen to be).

#### FTL (Faster Than Light)

Now SF fans will often tell you that if v is greater than c the two observers will perceive time as going in opposite directions. You can’t blame the SF fans for that, it comes from a vast simplification that scientists often give about why they don’t pay attention to those values. If you actually look at the numbers, though, you’ll see that when v exceeds c (so your observer travels faster than the speed of light). This isn’t a negative number, it’s an *imaginary* number.

Now, imaginary time evokes a lot of really fascinating imagery, but what it refers to here is a mathematical term – a temporal axis which is at a 90 degree angle to regular, everyday time. It’s a lot simpler to see why physicists shake their head at FTL (Faster Than Light) now, because while going backwards in time has an obvious, physical meaning, going *sidewise* in time doesn’t.

#### STL (Slower Than Light)

There is a way that physicists *do* think relativistic time dilation can produce time travel. It involves combining high speed travel and *Wormholes*. Wormholes are a quantum phenomenon which link two points together without traveling through the intervening space. Scaling the quantum wormhole up to a usable size would involve the use of materials which have properties never yet observed, yet entirely consistent with known physical laws. The details are left as an exercise for the student, but *if* such a thing could be found or created, and *if* one end could be put on a space craft and accelerated up to relativistic velocity then returned to earth, going through the wormhole would give you time travel. One limitation would be that the earliest you could travel to would be the point where the timehole was established. Still pretty cool.

### Quantum

Time travel on the quantum scale is pretty much trivial, because if you’re observing on the quantum scale there’s no way to tell which way time normally flows anyway. As far as I know, every quantum reaction is completely reversible. In other words, if you were able to film quantum events, and play the film backwards, it wouldn’t look any weirder than playing it forwards. Personally, I think this is the least weird thing I’ve ever heard about quantum physics, but it does lead us to an interesting question…

### Classical

The second law of thermodynamics states that in a closed system entropy will increase over time. This basically *gives* us “time’s arrow” – time moves towards greater entropy. This just seems to be natural, but given that it’s not observed on the quantum level it could be a ‘local condition’ thing. In the past entropy was so remarkably, blindingly low that it just had to increase from there, but in the future, when the base level of entropy will be higher, maybe that won’t hold true. What will time look like then? What will the world look like then?

### String Theory

Not surprisingly, this gets even weirder. First of all, string theory isn’t really a theory. It’s more of a model kit which looks ** really** promising to build a hypothesis which might conceivably connect the classical, relativistic and quantum equations which describe the world. In other words, it might become the “Unified Theory” Einstein never found, or GUT (Grand Unified Theory) as it’s more often called these days.

In string theory space-time is made up of the vibrations of really tiny (Planck scale) loop like particles. Let me repeat that – the *vibrations* make up space time. So what are they vibrating *in* if it’s neither space or time? String theory also consists of ten (or eleven) dimensions. Four of which are big (three space, one time) and the others loop around themselves. It’s possible that space and time loop around themselves as well, but if they do it’s a *really* big loop.

So there are a lot of people playing around with string theory. I seem to recall, years ago, a paper hit PlosOne which proposed a version of string theory with two temporal axis. I can’t seem to find that link any more, so maybe it’s been lost in the sea of peer review. Which would be a shame, because not only is is super cool, but it puts FTL back on the map, as it were…

## Fiction

I love time travel stories as well. I’ve talked about Doctor Who here before, but there are so many great fictional universes which play around with time travel in one way or another. Some are super cheesy, some are tragic, some hilarious, and all of them wonderfully weird.

Definitely a rabbit hole worth falling down…

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