Would it be possible to (re)build a Mass Relay?

Question

Spoilers warning: I'll be spoiler tagging any Mass Effect 3 spoilers, but anything from ME/ME2 won't be spoiler tagged. You've been warned.

In the Mass Effect universe, the primary means of interstellar travel is by a system of Mass Relays. Faster than light travel does exist, using similar technologies based on mass effect fields, but the relays are much more efficient for interstellar travel given the immense distances between inhabited systems in the galaxy.

In the "Arrival" DLC for Mass Effect 2, we actually see the destruction of one of the relays. Also, in Mass Effect 3,

the beam careated by the Crucible and the Citadel in the game's final sequence destroys (presumably) all of the mass relays throughout the galaxy.

The races of the galaxy have been studying the mass relays and using mass effect technology for hundreds of years. Humans have been examining and using the beacon on Mars, which originally led them to the Charon relay itself. In Mass Effect 3, we also discover that

the Asari have been gathering information and technology from a Prothean Beacon for an unknown amount of time, providing for their technological advancement.

Given the familiarity of the races with the mass effect fields and the relays themselves, what are the chances of a relay, or relay system, being built by the races of the galaxy? This would obviously be no small undertaking, but is it ever commented on? Has it ever been tried?

Answer 1

Yes, given the time the Oldest Galactic races have had to study the Relay Network, it is likely, given the time, they could replicate the hardware and computing power needed to create the Mass Relay network. However, there would likely still need to be developments done since part of the goal of the network was to keep races from WANTING to create new or divergent technologies that would compete with the Relay Network. This played into the goals of the Reapers in the first place.

When a species created technologies that might compete with the network or triggered enough of the network that they might be a threat, they were wiped out by the Reapers. Species that were destroyed had no trace of what happened to them, keeping their destruction mysterious.

The creation of the existing network took thousands of years to create, setup and maintain before it could be allowed to run unattended for millennia while the Reapers slept in Dark Space. The very idea of creating a competing network probably never serious occurred to anyone as long as the existing network was functional.

From the Mass Effect Wiki:

According to the Catalyst, the Reapers destroy advanced organic life in order to preserve a fragile balance. The Reapers believe that without the extinction cycles, synthetic intelligence would completely annihilate all organic life. This is because of a natural tendency to chaos; organics will always create synthetics and synthetics will always rebel against them. The Reapers also believe that destroying advanced civilizations is the only way to allow new civilizations to come into existence. The Reapers leave no evidence of their conquest, nor of their existence – only desolate, barren ruins of those who came before.

Now that the Mass Relay network is no more, the Galactic Races will have to come together to decide:

• Do we develop faster drive technologies? Since the threat of the Reapers would be over (hopefully) there would be no artificial force retarding the development of new technologies. This might allow the Galactics to discover something completely new and unheard of by the Reapers. Or it might not. Perhaps the Reapers have already taken that path and decided there wasn't anything so that may explain part of the reason for the Relay network.
• Do we build a new mass relay network? The technology is available, understood and likely able to be done, but even with the fastest drives and building technologies, it would be tens of thousands of years before a comparable network would come into existence. More than likely the most central worlds would be connected first and the rest of the network would come into existence where needed.
• There would also be the question of whether the Reapers were right. Do artificial intelligences created by organic races always rebel and destroy their masters? Since the Reapers were disrupting the natural processes in the galaxy, could it be possible their assumption was correct? And if so, what will the Old Galactics do to prevent this from happening...

Answer 2

As @user13285 points out, the mass relays were merely damaged, not destroyed (but he left out the important fact that you must have the Director's Cut DLC). Also according to the Director's Cut endings, we apparently have at least enough knowledge of how they work to repair them (albeit slowly).

BioWare retconned them in the Director's Cut because it was established in the Arrival DLC for Mass Effect 2 that the energy released by destroying a mass relay can wreck an entire system, which is why Shepard was relieved of duty between ME2 and ME3. He deliberately detonated a mass relay in a batarian-colonized system to stall the arrival of the Reapers, resulting in the complete destruction of the colony (about 300,000 batarians, if I remember correctly). Had he been anyone else (and had he not had the backing of Admiral Anderson), he would probably have been court-martialed.

Also of note, even without the relays, we still have FTL, just not at the incredible speed that travelling via relay would permit. I don't know if this is from a canon source or not (probably not), the top speed is between 0.15 ly/hr, to about 0.4 ly/hr, depending on the size of the ship and whether or not it has any special upgrades such as the oversized Eezo core of the Normandy. So, although the relays can't be used until they're repaired, at least nobody's stranded.

Answer 3

The relay network was damaged, not destroyed, and in answer to the orginal point, it is possible to create relays, the first game is proof of that it can be done, seeing as the protheans made a small, one step off a fully functioning mass relay and that is only because they ran out of time to make the citedal relay send them back.