I have a limited understanding of the physics of it, but as far as I know time dilates at higher velocities. Meaning that time essentially passes slower for objects moving at higher velocities. Why don't FTL travelers using Mass Effect Relays experience this?

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    Duuuh the Protheans obviously solved that issue.
    – Jakob
    Jul 18, 2014 at 7:04
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    I think it has to do with the mass effect and how the relays use it. The relays use the mass effect to create some sort of "low mass" tunnel between them. I think the in-universe explanation would somehow revolve around that. Out of universe, the developers didn't want to deal with it, so they ignored it. Jul 18, 2014 at 13:30
  • In one of his (unjustifiedly) less known works, Albert Einstein demonstrated that objects moving at the speed of plot(tvtropes.org/pmwiki/pmwiki.php/Main/TravelingAtTheSpeedOfPlot) have no relativistic side effects.
    – SJuan76
    Jul 19, 2014 at 11:56

6 Answers 6


If you take special relativity literally, any object observed to be travelling faster than light in one frame can be shown to be not moving(in time) in another frame and traveling backward(in time) in a third frame. Any universe that features faster than light (FTL) travel does not use the physics of our universe. Or if it does, it has to deal with the time travel aspect of FTL travel.

It's safe to say that either:

1) The mass effect speeds are not really faster than light speeds, but only talked about that way in-game.


2) The physics of the game universe are not the physics of our universe.

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    The apparent reverse time travel inherent to theoretical superluminal travel is exactly that -- apparent. If you travel to mars at 2c you can turn around and watch yourself leave, but no matter how fast you travel the guys back home won't be able to see you turn around before you depart.
    – DougM
    Jul 21, 2014 at 4:18
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    @DougM: but a third person, travelling in the opposite direction will see you age from an old man to a baby. Also, if you send a signal to a person travelling at 2c in the opposite direction, you can have them shoot your grandmother before you're born. The effect is really simple if you draw a spacetime diagram. Jul 21, 2014 at 4:41
  • Yes, someone moving 2c away and looking backwards with an infinitely powerful lens can view time flow backwards. But regardless of speed, they cannot arrive back before they left, or arrive early enough to act on a message before it was sent. The impossibility of "move faster than c" is not the same impossibility of "travel backwards in time."
    – DougM
    Jul 21, 2014 at 17:48
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    @DougM: If you can travel in spacelike curves, you very well can go back to where you started, or before where you started. It's just a fact. It's not about powerful lenses or looking backward. It's just the fact that there is no Lorentz-invariant time ordering of spacelike seperate events. If you start letting observers travel along spacelike curves, causality no longer makes sense for those observers. It's not an "apparent" effect. It's a fundamental part of special relativity. Jul 21, 2014 at 18:07
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    @DougM: I have a phd in general relativity, fwiw. You are correct that a FTL drive wouldn't automatically be going backward in time. But if you had several of them, you would be able to work out time paradoxes relatively easily. Jul 22, 2014 at 1:37

It has somthing to do with the "mass effect". I believe It is explained in game. Basically the mass effect field not only makes it possible to travel FTL but it also allows you to harness negative energy which in turn bends space and time into a "pretzel" which basically prevents time dilation. Here is a link to a physicist who can explain it better:


Dr. Michio Kaku is one of the top physicist in the world.

Here is some more info:

"Cosmic strings: Another theory for potential time travelers involves something called cosmic strings — narrow tubes of energy stretched across the entire length of the ever-expanding universe. These thin regions, left over from the early cosmos, are predicted to contain huge amounts of mass and therefore could warp the space-time around them.Cosmic strings are either infinite or they’re in loops, with no ends, scientists say. The approach of two such strings parallel to each other would bend space-time so vigorously and in such a particular configuration that might make time travel possible, in theory."

Source: http://m.space.com/21675-time-travel.html

  • Very good answer, and welcome to the site!
    – Wad Cheber
    Jul 15, 2015 at 9:27

Mass Effect fields work by reducing the mass of anything inside that field. This removes any mass based time dilation, at rest or while moving. With typical relativistic travel, the faster you go, the more energy you need as your mass increases while moving. By reducing that mass to near zero, you reduce energy needs.

But Mass Effect fields also have another effect, as it were. It effectively raises the speed of light, C. As that also changes, the ship inside the field would still be traveling at a low fraction (relative)C, and not experience time dilation from massless high velocity alone.


While I'm not certain, I would think it's because the ships have no mass at all (biotic lifts demonstrate this happening on the battlefield). I'm no physicist, but I would think that relativistic effects are dependent on the amount of energy used to propel something- and with no mass, no energy would be required to propel it. Obviously there are still questions there.

As Prototypetolyfe says, the studio didn't cover this, possibly because it's a lot of trouble, and possibly because you're getting into territory noone has crossed.

And Jakab, spoiler: the Protheans didn't invent Mass Effect technology.

Also, it's not just the relays; relays operate between clusters of stars, but ships in the ME universe all have FTL themselves. I assume the relays just go a lot faster.

  • I thought it might have something to do with being massless, but that didn't make total sense to me. As I understand it, mass is a factor in time dilation, but just plain velocity is also a major factor, so I'm not sure. I guess I'd need to talk to a real physicist.
    – Scrotinger
    Jul 18, 2014 at 14:04
  • Velocity is an effect, not a cause- the cause is the energy and the mass, and I think that's what also causes the time dilation effect. Large amounts of energy and mass do that- look at black holes, for instance. Maybe, as you say, someone in the field could help more. Jul 18, 2014 at 14:21
  • @Scrotinger - mass only becomes a factor in time dilation if the mass is sufficient to cause gravitational time dilation, even from a perspective where the object is at rest. On the level of individual particles traveling through deep space, mass doesn't enter into time dilation, only velocity does. And time dilation approaches infinity (i.e. clocks approach being frozen) as velocity approaches the speed of light, so real physics doesn't tell you anything about what sort of time a hypothetical FTL particle (a "tachyon") would experience, if it had an internal "time" at all.
    – Hypnosifl
    Jul 18, 2014 at 14:31
  • Real physics does include some theoretical possibility of pseudo-FTL where a ship doesn't move faster than light locally (i.e. light that passes next to it moves faster than it), but the space between it and its destination can be distorted so it can get to otherwise distant locations very quickly, see en.wikipedia.org/wiki/Wormhole#Traversable_wormholes and en.wikipedia.org/wiki/Alcubierre_drive -- in these theoretical solutions the ship needn't experience any different time than observers at rest at the departure point and destination.
    – Hypnosifl
    Jul 18, 2014 at 14:34

There is no evidence that interstellar travel in the Mass Effect universe does not impose time dilation effects; the player never gets a real-time communication while moving at high-velocity relativistic speeds, and the ability to travel faster than light itself minimizes the time-debt. (If it only took me 20 subjective minutes in the citadel's frame of reference to traverse the galaxy, it doesn't matter if my own time frame had 20 subjective minutes or 2.)

For what it's worth, a mass effect that was able to remove a pure 100% of the mass from an object would not be sufficient to exceed c according to Einstein's theory of general relativity. It's not the speed that light just happens to travel; it's the maximum speed that any thing can move between two points. (QM funkyness notwithstanding, as QM begins with changing the meaning of "point", "move", and "thing")

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    Quantum mechanics doesn't allow for superluminal causal influences. Special relativity is built into QFT, and is 100% consistent with it. Jul 21, 2014 at 4:42
  • Unless we're discussing QM or subatomic effects, it's far simpler to handwave it as "it's weird" than cover all bases.
    – DougM
    Jul 21, 2014 at 17:50
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    QM has absolutely zero to do with the question. And is consistent with special relativity. Jul 21, 2014 at 18:09

I have no quote for this theory, but I always thought that it was because of the law of conservation of energy. Let's try a bit of math...

Remember the basic equation:

E = m·c2

Let the mass under a Mass Effect field be: me=k·m, being "k" the strength of the field.

But "E" must be constant in an isolated system such as a spaceship, so it is the light-speed that changes:

E = m·c2 = me·ce2 = k·m·ce2


ce = c·√k

Now, time dilation factor due to relativity is:

λ = √(1 - v2 / c2)

And under a Mass Effect Field:

λe = √(1 - v2 / kc2)

Or if you prefer:

λe = √(1 - (v/√k)2 / c2)

Imagine that you are willing to allow a 1% time dilation. The maximum speed, without a ME, would be about 42.000 km/s. But with a Mass Effect field of k=10-10 you can go up to 420.000.000 km/s. That's about 1400 times the speed of light!!

  • This seems sound but the math is slightly over my head. So with your last sentence, you're saying that with that ME field we can go 1400 time the speed of light and still keep 1% time dilation?
    – Scrotinger
    Jul 18, 2014 at 16:20
  • @Scrotinger - Precisely. Note that this is quite a big ME, so you'll need a starship-size generator.
    – rodrigo
    Jul 18, 2014 at 17:00
  • So then is it feasible that the crew of the Normandy can limit time dilation while using the Mass Effect relays? I imagine the fields created by the relays are quite powerful
    – Scrotinger
    Jul 18, 2014 at 17:56
  • @Scrotinger: Sure, ME Relays must be much, much more powerful. With my ME drive you could get from Sol to Sirius, 8.6 light-years, in about 2 days, piece of cake. But to cross the galaxy (100000 light-years) you would need more than 70 years... Maybe possible... but just think of that minigame!
    – rodrigo
    Jul 18, 2014 at 19:50
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    @Keen - you are talking about the concept of "relativistic mass", but most modern relativity textbooks have dropped this concept and just define the total energy using the equation E^2 = (p^2 * c^2) + (m^2 * c^4), where p is the relativistic momentum p = mv/sqrt(1 - (v/c)^2) and m is the rest mass. This equation works out to be equivalent to the equation E = Mc^2 where M is the relativistic mass, equal to m/sqrt(1 - (v/c)^2).
    – Hypnosifl
    Jul 21, 2014 at 4:27

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