Ask The Plant: Is Time Linear or Circular? -A confused physicist
Arts & Culture Editor
Is time linear or circular? That's a complicated question. Now I’m really glad I took a physics course last term.
First of all, we know that time is fundamental because it would not slow down if it weren't. Time dilation is a distortion in what we think of as time flow, in high-speed transitions or the presence of strong gravitational fields.
In terms of the universe, according to the general theory of relativity, the density parameter Omega, defined as the average density of the universe divided by a critical density (which is required for the universe to have zero curvature), is related to the curvature of space. If Omega is 1, the curvature is zero, and the universe is flat; if Omega is greater than 1, then there is a positive curvature indicating a closed or spherical universe; if Omega is less than 1, there is a negative curvature suggesting an open universe.
The cosmic inflation model suggests that the Omega conjecture is precisely 1, so the universe actually balances between the two extremes. In that case, it will continue to expand but gradually slows down, and eventually, it will be powerless.
Even with dark matter in the calculations, all matter in the universe, both visible and dark, is only about a quarter of the critical mass required, suggesting a continuously expanding universe.
Oh, I just realised this is a lot of science talk to throw at you early in the morning. Let me try to explain it differently.
Time as we know it in our everyday lives is, essentially, an idea based on a sensation based on an observation, which, in turn, is based on our knowledge and memory of the state or condition before the measurement of that change. Time is the feeling that we experience when we see some kind of change, like movement or a state change.
Linear time is like an arrow launched from the past, crossing the present and heading for the future. Meanwhile, circular time can be likened to circular wheel movement or rhythmic pendulum oscillation.
When people think that celestial changes or seasonal changes associated with the Earth's position around the Sun are time, it's like thinking that a fish swimming in an aquarium is water. In fact, a tank is like space, and water is like time. Water fills the tank, and it's everywhere. If it wasn't, the fish wouldn't be able to move and would be dead, despite all the space in the aquarium.
Time itself is neither linear nor circular. It does not flow or move but allows others to do so. So the cycles we observe have nothing to do with time, except that time will enable them to exist. Time is attached to each part of space, forming a space-time continuum, and as everything moves, vibrates, changes, it is related to the fact that time is a dimension that allows change, and spatial dimensions enable things to be in different places. When these things change position, it's because time allows it to happen. No time, no change, no nothing.
The fact that time doesn't move explains the asymmetry of time or why things never seem to come back. Even though physicists can control their equations backwards and forwards, we will never see that the events that explain these equations happen backwards. That's because time has nothing to do with it. For things to happen in reverse, all the forces and processes that make them happen in a causal order would have to be reversed, and that would never happen. Gravity will not change, your biological processes will not change, the expansion of gases in the blast will not change because there is no causal agent that can force them to do so.
But, hey, ask me this question again when I’m looking at the clock during class, and I would forget all of this and tell you that time actually seems to be moving backwards.