(If parallel universes do exist, did they all start simultaneously? I mean, let's assume that the universe originated from a singularity. Were there any parallel universes at that point? That would not be very logical and it would also imply that there is a parallel universe in which our universe never existed.)

It is thought that the event called the “Big Bang” was the start of not only this worldline or universe but all worldlines and all universes that make up the superuniverse. It is also thought that the superuniverse can be imagined as an expanding sphere with the big bang in the center.
Individual worldliness (or timelines as you call them) can be imagined as lines originating at the center and “trending” toward spiraling around the sphere until they reach the edge. The individual worldlines expand in length and widen as you follow them from the center. Each individual “moment” or “event” on a world line has infinite possibilities or outcomes. Imagine this as a single point with infinite lines shooting away from it, which in turn are made up of points with their own possibilities and outcomes. Now, remember, these individual worldliness with all these points and possibilities are defined by their ability to hold there inhabitants to timelike trips only (no faster than light travel).

Now consider the reality of a spinning or electrified black hole (Kerr). Penrose diagrams of these oddities show mathematically that you can make simulated spacelike trips (faster than light) through the singularity without being destroyed. In order to do this without wiping out most modern physical laws, you must travel to an alternate worldline or universe. Therefore, if multiple worldlines exist, infinite worldlines exist.

In trying to imagine a superuniverse with infinite possibilities and worldlines, I think of a room with mirrors on all the walls. You are aware of your captivity but as you look in the distance, you see an infinite number of “yours” in an infinite number of mirrored rooms. The gravity distortion machine allows you to “step” out of your room and into another next to you. The closer you are to your original room, the closer it looks like yours, the farther away, the stranger it looks to you.

(…If I go forward on this world line, the future will not be my future. I get home by going back to 1975 before I arrived and then going forward to 2036.")

A few people have asked me about this statement so I will try to clarify it.

On my worldline (A) in 2036, I was given a mission in 1975.

I turn my machine on and jump to another worldline (B) in 1975 with about a 2% divergence from (A).

From the very point I turn my machine off on (B), I create a new worldline just because I’m there. This line can be described as (C) and started when I got to (B).

I am now doing my mission on line (C) in 1975 when I discover a very a good reason to go forward on (C) and see what happened. I turn my machine on and go forward on (C) to the year 2000.

When I turn it off, I start another line called (D). So from my perspective, here we are on line (D) in the year 2000. In order to go home to line (A) I must turn my machine on and go back on (D) until I reach (C) which in turn would take me back to (B) which in turn takes me to a point before I arrived on (B) then I go forward from the point I arrived on (B) back to (A).

If all this isn’t enough to get your head spinning…here are some issues we’re dealing with in 2036.

1. Did your worldline (D) exist at all before I got here from (C)? (personally I don’t see how it couldn’t)

2. What happens at the end of a worldine at the edge of the superuniverse?

3. If there are infinite worldlines and infinite possibilities and an edge to the superuniverse, doesn’t that mean occurring events on worldliness are staggered as they reach the edge? (time could end at any moment without warning).