Mass Effect Field technology and Conservation of Momentum +

[adam_grif]

Does the use of Mass Effect fields preserve CoM and CoE? If so, how?

Canon database on the tech and setting.

I posed this question on the bioware forums, got a whole bunch of "hurr durr its science FICTIONNNNN", but some serious discussions did eventually get going. The obvious option is that if CoM is in effect, using a mass decreasing field will result in a corresponding increase in velocity, and vice versa. But this apparently doesn't seem to be the case in universe, where they use the mass decreasing fields, burn for a while then drop the fields, and their velocity does not change.

But then we have some minor indirect evidence to support momentum being conserved in the disruptor torpedoes + fighters entries, where they claim that the torpedoes need to be ferried because they're so slow thanks to the mass-increasing fields they use. This implies that they can't simply launch them at high speed then apply the field, or if they do it slows them down by doing so. Of course, there is still the obvious stupidity involved in simply not applying the field just before it strikes a hull, but...

Also, craft in FTL drop out of FTL when the fields are no-longer applied.

The most interesting post so far was this one:

The fail is a lot bigger than what you imagine. CoM is preserverd. It cannot not be preserved. Therefore the velocity has to increase. This means that Conservation of Energy is not preserved because the velocity cannot change to make the energy be the same.

Example:
Object mass = 2 kg
Object velocity (relative to itself) = 3 m/s

Momentum: P = mv = 2 kg * 3 m/s = 6 kg m/s
Energy: KE = .5 m*v^2 = .5*2 kg * (3 m/s)^2 = 9 J

If you change the mass to 1 kg, you get
P = 3 kg m/s
KE = 4.5 J

This cannot be. So either something else has to interact witht the system to add the missing energy or the velocity has to change. The velocity has to change to 6 m/s to keep CoM, but it has to change to 4.3 m/s to keep the CoE. An object cannot have two different velocities relative to itself at the same time. Hence, unless they actually come up with a way to add the missing energy, it is epic fail.

Is this accurate? If so, it's quite amusing.

On the consequences of the ME field tech:

If CoM is in effect, then presumably everybody would just use mass lowering fields as a form of reactionless propulsion, only using burns occasionally to kill their momentum and change course. But in-universe, the only reactionless propulsion mentioned is using Eezo cores to induce high mass areas in front of the ship to "pull" them in that direction. If momentum is conserved in this fashion, it also seems that missiles would, unlike what the codex would have us believe, be probably the most useful weapon on the battlefield. They could just drop mass to zoom past PD systems, then go high mass to overwhelm the Kinetic barriers, then detonate.

On the flip side, if CoM isn't in effect, then any old frigate can become a planet shattering weapon. Screw Dreadnoughts being limited by treaties just because they have puny 38 KT rail guns, these are ships that can attain relativistic velocities with ease and can go FTL using the tech. They can just get to 0.99C then drop the fields into reverse to shatter planets. Missiles would be able to smash any ship in any enemy fleet with ease, and no point defense would save you.

Unless I'm missing something obvious, they could also use this to create perpetual motion machines, since the craft are getting a whole bunch of free energy from nowhere.

What are your thoughts on the matter?

[Starglider]

But in-universe, the only reactionless propulsion mentioned is using Eezo cores to induce high mass areas in front of the ship to "pull" them in that direction. If momentum is conserved in this fashion

I can't see how that conserves momentum. The 'high mass area' cannot simply be making existing matter at the front of the ship heavy, that would not cause any net acceleration (since it's functionally equivalent to gluing lead weights to the front of the ship). It must be a completely phantom mass or linear gravity gradient, which is automatically a reactionless drive (this is described as essential to the Normandy's stealth).

Therefore conservation of momentum is gone, and frankly so what. Better to keep conservation of energy for balance purposes, but you could violate that too and not have any horrible problems as long as it is done consistently. Clearly the universe is using different physics to our own, get over it.

On the flip side, if CoM isn't in effect, then any old frigate can become a planet shattering weapon. Screw Dreadnoughts being limited by treaties just because they have puny 38 KT rail guns, these are ships that can attain relativistic velocities with ease and can go FTL using the tech. They can just get to 0.99C then drop the fields into reverse to shatter planets.

Almost all space operate settings have that problem, so it's hardly an issue unique to Mass Effect. Presumably they rely on their fleets to intercept ships that try it, though it's possible that there are planetary scale mass effect defense fields.

Unless I'm missing something obvious, they could also use this to create perpetual motion machines, since the craft are getting a whole bunch of free energy from nowhere.

The fact that they still use conventional fusion and antimatter power sources strongly suggests that the physics keeps CoE but not CoM; thus to change something's effective mass, the field generator must supply or absorb enough energy to make up the KE difference.

[adam_grif]

I can't see how that conserves momentum.

Right, I constructed that paragraph very poorly. The Reactionless propulsion system is not the "fashion in which momentum is conserved", I was referring back to the idea that low mass fields would increase velocity to conserve momentum. The paragraph should make more sense when you read it like that.

Therefore conservation of momentum is gone, and frankly so what. Better to keep conservation of energy for balance purposes, but you could violate that too and not have any horrible problems as long as it is done consistently.

I don't understand how CoE could be in effect but not CoM. Does not an object have vastly higher KE than it has any right to when we use the momentum violations to turn the frigates into big missiles?

It seems the two are inevitably related, with Momentum being mv and KE being .5 mv^2.

Clearly the universe is using different physics to our own, get over it.

Right, because this is a thread about me complaining that it doesn't have the same physics as real life? Yawn. I'm trying to work out how exactly the universe is supposed to be working based on the information we have to work with. If this was just a realism bitchfest then I'd be bringing up ridiculous things like squad mates being resurrected by the power of Unity and Friendship, people getting blown back fifty feet and flung into the air at a high speed by a shotgun that clearly does not have that much recoil, the silliness involved in having dozens of alien races all discussing how much they hate humanity for being an upstart race, and holding said conversations in fluent unaccented English, etc etc.

But it's not.

Almost all space operate settings have that problem, so it's hardly an issue unique to Mass Effect. Presumably they rely on their fleets to intercept ships that try it, though it's possible that there are planetary scale mass effect defense fields.

Yes I know it's not unique.

There aren't any FTL sensors that I'm aware of (they use LADAR + thermal scans if I recall correctly), therefore the poor man's RKV's described above *should* be unstoppable in that regard. The only way I can think of is to prevent them from getting beyond your local Relay, but there is a relay every few Star systems and the FTL drives can reportedly cover a dozen lightyears in a single day's cruise.

So really, it seems more like a case of "You don't need to see our doctrine. These aren't the tactics your looking for."

The fact that they still use conventional fusion and antimatter power sources strongly suggests that the physics keeps CoE but not CoM; thus to change something's effective mass, the field generator must supply or absorb enough energy to make up the KE difference.

Is that even possible given that it can make things go FTL?

Actually, does anybody know how it does make FTL work in the first place? I don't see how reducing mass allows that, because even 0.00000001 grams still takes infinite energy to reach C doesn't it?


Tangent:

I was thinking about the similarities between this and the Redemption Ark style Inertia Suppression. Although they seem similar in concept, there is nothing reported in ME about the profound physiological changes involved.

[Ford Prefect]

holding said conversations in fluent unaccented English, etc etc.

That's explicitly the result of extremely common translator devices, some of which exist as subdermal implants. You actually have to download updated translation software in the Bring Down the Sky DLC mission, because your translator doesn't have the particular Batarian dialect used by the terrorist group Shepard and crew are fighting. There's also an Esperanto-esque trade language, but that would automatically be translated for Shepard as well.

[adam_grif]

holding said conversations in fluent unaccented English, etc etc.

That's explicitly the result of extremely common translator devices, some of which exist as subdermal implants. You actually have to download updated translation software in the Bring Down the Sky DLC mission, because your translator doesn't have the particular Batarian dialect used by the terrorist group Shepard and crew are fighting. There's also an Esperanto-esque trade language, but that would automatically be translated for Shepard as well.

I believe you, but I don't at all recall reading anything like that in any of the codex entries.

[Starglider]

I don't understand how CoE could be in effect but not CoM. Does not an object have vastly higher KE than it has any right to when we use the momentum violations to turn the frigates into big missiles?

When conservation rules are violated in an apparently isolated system, we can retain them by postulating an unseen connection to another system element. For example, if deflector shields in most sci-fi settings appear to violate CoM considering only the projectile and the shield, but typically the momentum is actually transferred to the shield generator by the exotic/unknown physical mechanism that creates the shield effect.

In MA, CoM does not seem to apply at all. From a Netwonian perspective CoE can still apply, if the kinetic energy gained or lost when particles change (effective) mass is balanced by a coresponding energy gain or surplus in the shield generator. MA fields also seem to decay on their own, probably by absorbing or dumping energy into the environment. There may be problems reconciling this with mass energy equivalence - maybe solvable by divorcing gravitational mass from inertial mass, I'm not sure.



It seems the two are inevitably related, with Momentum being mv and KE being .5 mv^2.

Clearly the universe is using different physics to our own, get over it.

Right, because this is a thread about me complaining that it doesn't have the same physics as real life?

The person you quoted seemed to have that problem, going on about things that 'MUST APPLY', when they must do no such thing since MA isn't hard sci-fi.

Actually, does anybody know how it does make FTL work in the first place? I don't see how reducing mass allows that, because even 0.00000001 grams still takes infinite energy to reach C doesn't it?

I seem to recall reading that the effect changes the local speed of light in proportion to the mass scaling. Probably on a forum somewhere though, so treat that as speculation.

[Ford Prefect]

I believe you, but I don't at all recall reading anything like that in any of the codex entries.

Do you have Bring Down the Sky? If not, you can't get the Codex entry that explains this.

I seem to recall reading that the effect changes the local speed of light in proportion to the mass scaling. Probably on a forum somewhere though, so treat that as speculation.

No, that's pretty much stated within the game's Codex. It says something like 'as the subjective speed of light is raised within the field' when talking about how emissions are redshifted/blueshifted when FTL is in use.

[adam_grif]

I believe you, but I don't at all recall reading anything like that in any of the codex entries.

Do you have Bring Down the Sky? If not, you can't get the Codex entry that explains this.

No, my 360 isn't even connected to the internet because my Ethernet cables are about a foot too short to make the distance.