Dave_Oblad » January 30th, 2021, 5:27 pm wrote: I clicked on the link you provided and found some good stuff, including what I was saying about the 4D shape being conical. I will have to go back and read more than just chapter 7.

As I recall, the 3D shape is conical when going from the bottom to top or more like a hemisphere when expanding- and like the top of a sphere when contracting. The end result is a complete sphere or Faradave's layered onion.

I added the link to Rudy Rucker’s model because I find it to be a possible extension of Faradave’s onion model where the onion represents one cycle of time from Big Bang to Big Crunch. If the onion rebounds from its Big Crunch the result would be a new Big Bang and the creation of a whole new universe with possibly little resemblance to the previous cycle.

The second universe could collapse and rebound into a third universe and the cycles could continue ad infinitum with a series of universes connected by a single timeline. Rucker calls this a “string of pearls model” or, with Faradave’s onion, a “string of onions.” This is a linear 3D understanding of how our universe may be part of a continuous cycle of universes rather than a one-time event.

The timeline of a “string of onions” can be joined into a continuous circle within a 3D torus to represent a never-ending circle of possible universes going around and around. This is Rucker's model of a torus-shaped multiverse that contains all possible universes... past present and future. He simplifies this model as a single 4D hypersphere since a torus in 3D space becomes a 4D hypersphere when rotated through one more dimension just as a 2D circle becomes a 3D sphere when rotated through one more dimension. This is Rucker’s idea of the universe as a 4D sphere but he describes it as a torus because a torus is easy for us Spherlanders to visualize.

I like to imagine Rucker’s model as a washing machine with an agitator in the center and the universes are like articles of clothing going around and around. They expand as they move to the outside and contract as they move to the center and, at the very center, is the Big Crunch-Big Bang where everything dies and is reborn.

In Rucker’s model, an observer’s location in the greater of a 4D spacetime determines whether their universe appears to be either be expanding or contracting. Any motion away from the center expands and any motion back to the center contracts but there is no actual expansion or contraction of the 4D sphere itself. There are just different densities depending on their distance from the center where everything contracts to a point.

I like to imagine Rucker’s model as a washing machine with an agitator in the center and the universes are like articles of clothing going around and around. They expand as they move to the outside and contract as they move to the center and, at the very center, is the Big Crunch-Big Bang where everything dies and is reborn.

In Rucker’s model, there is no need for dark energy to accelerate the expansion of space because the expansion of space is an illusion and it takes no energy to accelerate an illusion. The 4D hypersphere that contains our universe neither expands nor contracts.

Rucker's 4D model is a timeless hypersphere using Block Time but his writing was before the term "Block Time" became popular.

Dave_Oblad » January 30th, 2021, 5:27 pm wrote:A quick point in regards to Relativity: It should be possible to make an instrument that quickly outputs its Velocity through Space with no outside references. How? Remember the Centrifuge Experiment with 2 clocks, 1 on the Arm and 1 at the center. These two clocks will run at different rates. If one can mathematically remove the temporal effect of being a clock that is under rotational acceleration (which would be a constant if the whole experiment was not accelerating) then the difference between the two (atomic) clocks would produce a value that can only occur at 1 specific velocity.

Because the equation for Time Dilation is non-linear, there can only be one place on that curve where both clocks agree about their relationship. That place on the curve is the actual velocity of the instrument through Space. Clever physics folks would probably be able to find a better more compact design that yields faster results.

The two clocks on the centrifuge could be synchronized so they both read the same time but the problem remains that there is no way of knowing the absolute velocity of the clock in the center. The measured difference in time would be relative to the center clock and the center clock’s absolute velocity relative to the universe is a big unknown.

I don't see how a calculation could be done to give you the absolute velocity of the center clock.