Alternate reality

"Look, I know this is hard for you to understand. But according to quantum theory, for every possible universe there are an infinite number of variations, diverging in every choice we make, like forks in the road."

- An alternate Samantha Carter (SG1: )

According to the quantum theory, there are not one, but an infinity of alternate realities or parallel universes in which many different variations can occur from one to another at some point, changing the fate of the aforesaid reality and making them different to the other ones.

Overview
A long time ago, Albert Einstein has predicted the whole concept of quantum physics in his relativity theory, including the alternate reality and timeline theories, and according to some scientists, there are an infinite number of dimensions, each of them with a different version of reality. Some realities are almost identical, others are completely different, depending of the choices and decisions made throughout the timeline. Each universe evolves concurrently on the same timeline basis (SG1:, , , ).

Discovering
The theory has become fact in 1997 when Daniel Jackson touched a quantum mirror on P3R-233. He instantly switched to another dimension and experimented a very different version of Earth in which the Goa'uld invaded and destroyed all main Earth cities. He met alternate versions of George Hammond who was a colonel and not a general, Catherine Langford who was still part of the Stargate project (SG1: ), Samantha Carter who was a civilian and not a military, and Jack O'Neill who was a brigadier general and not a colonel. According to Jackson, everything is the same, but different (SG1: ).