How many people were in the Atlantis Expedition and lived on Atlantis?

Question

The city of Atlantis looks to be rather sizable and the nighttime shots of Atlantis almost always shows lights on all over the city, implying it is fully occupied. But I can't imagine the IOA/Airforce having the ability or being able to afford to send more than a couple thousand folks (nor does it even look like it's that much on the show). I realize the Athosians also lived on Atlantis for a while, but the lights are still always on all over the city on night shots even after they left.

How many lived on Atlantis? And as a follow on, assuming Atlantis wasn't at 100% capacity, why would they waste all that power on lights, etc when it always seems there's a shortage of power on every other episode?

Answer 1

Atlantis is stated to have the internal volume of the city of Manhattan! (At least according to the Stargate Wiki) That's a lot of space. But we never see more than about 50 people on the ship at once, unless they are invading or being refugees.

So why is everything so lit up? Two reasons:

The Atlantis crew don't have full control of the city. They turn it on, it surfaces, and starts coming to life. Many of the bottle show plot points on Atlantis comes down to them discovering yet another feature or system which is online that they didn't know about. Not having full control over the city, the lights come on. I imagine there's a light switch in every room, and that you could turn them off if you wanted to. You'd want to avoid simply switching off chunks of the power grid, though, because you don't know what that might turn off. It might end up bad. So Atlantis is as the Lantians left it; lights on and all. So why don't they care?

ZPM's contain MASSIVE amounts of power. Yes, the show worries a lot about how much power is being pulled from their ZPMs, but keep in mind: three ZPMs kept a forcefield intact for 10,000 years at the bottom of the ocean, and still had enough power to surface the city, throw upt he shield at least one more time, and run life support in the city. The one thing they are not worried about is power usage. Lighting is the second most efficient conversion from electricity we have (the first is electric heat), and the cost of running all the lights compared to, say, the Stargate itself (being as Atlantis has to power the Dial Home Device from the ZPM as well, and the DHD powers the gate...), it's a rounding error.

The lights are on because it's too much effort to turn them off.

Answer 2

The real world explanation from "Hollywood" is that it looks a lot better to have the city skyline illuminated broadly so that the size and scope and enormity of the city would appear easily in the tiny time alloted to the intro and other city shots. That said, the in universe explanation is still pretty simple.

The city, being huge and mostly automated, has a lot of moving parts and sub systems that need to be validated and tested on a regular basis. It is very likely that the city, as part of the standard diagnostics that the central computer performs, would schedule regular tests of systems that had not been used frequently. That way, if those systems were called upon, the city would know they would be fully ready and able to respond as needed. Lights are an important sub system. Thus, one could assume that the city shots taken at night were taken during times that the tests were being performed and if the camera had remained pointed at those areas of the city for an extended period of time, the lights would have switched off as tests completed.

Any defective lights would be noted and automated repair systems would correct the issues at the next opportunity.

The number of people: about 50 as mentioned previously, but increasing to eventually around 75 Earth personnel as the importance of the expedition increased and the galactic bridge was completed. An additional 20-200 humans from alien planets depending on the point in the timeline.