With signals from 4 satellites one can triangulate oneself in 3D space, with 5 signals, in 4D! (3D + time). I once did the math and astounded myself that it worked.
It will get another signal from another satellite, which could have the timestamp before X, because it left earlier and took longer to get to your receiver.
As I said, if you do the math, with 5 signals you can then determine your location in 3D space, and time!
No, GPS positioning uses the precise time information encoded in the data from the satellites.
GPS doesn't use the strength of the signal at all. Instead, each signal contains precise information about the current time at the highly-accurate atomic clocks onboard the corresponding satellite (plus some important metadata about each satellite, including things like their orbit parameters). If the receiver already knew the precise time, it could calculate the distance to each satellite from the difference between the true time and the received time (and the speed of the light), and 3 satellites would be enough to triangulate its position. Since the receiver usually doesn't know the precise time, it needs an extra satellite because there are now 4 unknowns (3 for its position plus 1 for the current time).
(Obviously, that's a very simplified explanation, there are plenty of other things which complicate the calculations.)
Wrong. Utterly wrong.
what you did wasn't that -- but I would just like to point out that simple concise explanations helps the community as a whole; it's not just the ignorant that lose out.
Yes, I know it's likely not your job to educate, and maybe it's a bother that someone acts expert on something that they're clearly not -- but those that care to educate serve everyone in the context of an online forum, not just the naive or ignorant.
I'm no GPS expert, I've read some of the theory had enough of a working understanding to deal with tactical navigation systems, but that was in my past. I remember using El-Rabbany's "Introduction to GPS" text.