The Physics of Mass Effect
If you haven't played any of the Mass Effect games, you really should. However, sometimes the physics of the very wonderfully developed fictitious future galaxy doesn't quite hold up. In this case, the very effect they've named the games after. Now, I'm not going to discuss Element Zero or the idea of manipulating mass (which is the titular Mass Effect), but rather how this manipulation doesn't make possible many of the things they claim it does. But first, let's start with a primer for those of you whop haven't played the games, or didn't pay a whole lot of attention to the sciency stuff in them:
In Mass Effect, a rare substance called Element Zero is used to manipulate the mass of matter within a field. This manipulation can make things either more or less massive, and this convenient plot device is the basis for most of the future technology of the games. For example, FTL travel and the Mass Relays. Now, I'm not going to get into how FTL travel, regardless of method, causes causality issues, that's a topic for another post. What I will talk about here is how manipulating mass will not even allow for FTL travel. The FTL drives in the ships in Mass Effect manipulate mass within a small bubble of spacetime (a Mass Effect Field) to supposedly increase the local speed of light, and allow a ship to move much faster than the speed of light in the normal vacuum. This is sort of how the Star Trek warp drive (or the real-life theoretical Alcubierre drive) works, but I'm at a complete loss as to how manipulating mass within a field will increase the local speed of light. I suppose I should explain why.
Light can be described as a particle or a wave. As a particle, it's massless. Due to a lot of somewhat complicated physics involving Maxwell's equations and electromagnetism, it moves at exactly 2.99x108m/s, also known as c, in a vacuum. There are a few other massless particles (which carry forces in the Standard Model), which also move at precisely c. In other mediums, c is slower. However, no massive particle (a particle with mass) can ever attain, let alone exceed, c, as the more you accelerate, the more energy you need to keep accelerating, and it would take infinite energy to get to c. But the point is that light moves at its absolute fastest in a vacuum, and space is a vacuum. Moving through mass just causes it to slow down, so manipulating mass wouldn't really be able to increase the local speed of light. Nut, if you were able to increase the local speed of light, there is a chance that FTL method would work. Which is a neat idea, and somewhat sound physically. Unlike the Mass Relays.
Mass Relays are the building blocks of galactic civilization in the Mass Effect universe. They allow for instantaneous transportation between points in space separated by hundreds or thousands of light-years, without experiencing nasty effects like time dilation. Now, how they work is also related to Mass Effect. What they supposedly do is create a Mass Effect field between them, and reduce all mass within the field to 0, supposedly allowing anythign within this "tunnel" to be accelerated to speeds far greater than that of light. This idea, however, doesn't really work (though it's a good try). First of all, without mass, acceleration becomes... problematic. First, you may have noticed that I already mentioned above that all massless particles travel at a constant speed of c, and always c. This means that, within the tunnel, the ship would simply travel at the same speed as light, taking hundreds or thousands of years to get to its destination. "Ah," you may say if you're clever, "but you said that light travels at different speeds in substances! A change in velocity is acceleration!" Yes, that is true, but, more technically, the photon is absorbed by the substance, and another is emitted. No actual acceleration of the individual photon. A photon always will travel at the local speed of light, and never change. And the fact that they would have to move at c, and only c, brings up the other problem with Mass Relays: time dilation.
I know, I know, Mass Relays explicitly are supposed to prevent time dilation, but time doesn't really care all that much about your mass. As you go faster, time behaves differently. This, to put it simply, is to keep the speed of light absolute. No matter how fast you're going, light will always move away from you at 2.99x108m/s. Ignoring, for now, the more complex parts of special relativity as it relates to how exactly time and reference frames work (you don't say time is different for you, it's always those losers in other reference frames who time is misbehaving for), I'll bring up the equation for time dilation as it relates to speed:
This basically relates your time to an outside observer's time, with your relative velocity being v. Now, obviously, if you simply plug in c for v, you get an undefined answer (because you're dividing by zero), so, to get a notion of what one would experience if they were to somehow attain the speed of light, we need to take the limit as your velocity approaches c (in non-math terms, we look at the trend as v increases towards c, and extrapolate for the undefined value):
Oops, we've now experiences infinite time in our briefest of sojourns at light-speed. The universe would have died around you as you attempted to navigate the Mass Relay.
Now, this is just me being kind of nit-picky about Mass Effect. I love the games, and how deep the lore is in their fictional universe—if it wasn't so expanded, I wouldn't have been able to thoroughly trash it like I did here. And it violating physics doesn't stop the games from being good—just about every sci-fi book, movie, or game ignores or changes physics at some point. But it would be super-cool if things like the Mass Relays could exist, and we could go out and explore the galaxy. Also, Element Zero and Mass Effect also would allow for negative mass, which is just so awesomely weird that I may have to talk about it in a subsequent post. But for now, I'm off to go play Mass Effect again. And you should play it, too.