Posts Tagged ‘time’

The Spacetime Diet: Redistributing the Fat of the Universe

October 29, 2017

If you’ve had your nose in spacetime physics at all, you’re familiar with the idea that when you move really fast, other objects look thinner. Or, relatively, you look thinner from the viewpoint of someone else’s reference frame.

This is called the Lorentz-FitzGerald contraction. When you observe a moving object, it appears shorter, or thinner, along the axis of its motion relative to you. Likewise, you appear thinner relative to the moving object (who does not feel thin at all). There’s a formula for this, but it’s irrelevant for the discussion below.

You also appear to gain mass (using a similar formula). This is also irrelevant for the following discussion, but I thought I’d toss it out there.

So here’s the rub. You will often hear someone say or write, “When an object nears the speed of light, the universe flattens to a thin sheet from the viewpoint of an observer on that object.”

Just to clarify, this is bullshit. If you are cruising along at near-light speed, then all matter, relative to your frame of reference, is moving in the opposite direction at near-lightspeed. That’s okay so far. Except, the universe is expanding. And the farther out you go, the faster it’s expanding, such that there are regions of space expanding away faster than the speed of light (the expansion of “space” is apparently able to ignore the whole “speed of light” limit thing; go figure).

So when you attain a certain velocity, you become stationary relative to another part of the universe that is moving away from Earth at the same speed. There is no shortening of length or thickness for that object, that part of the universe.

Take the Andromeda Galaxy for example, moving toward us at 110 kilometers per second. When we measure the galaxy in the direction of its travel, along its axis of motion, it’s foreshortened in that direction. Now, fire up your rockets so you’re traveling at 100 kilometers per second in the same direction, and Shazam! The entire galaxy poofs back out to its real shape in its own frame of reference that happens to coincide with your own. Relative to you, the Andromeda Galaxy is no longer moving.

So, back to the expanding universe; as your spaceship speeds up more and more, there’s always a part of the universe that’s moving at the same speed at which you are traveling (a comoving reference frame). It won’t look compressed or thinner or foreshortened at all. In fact, if we take the viewpoint that all parts of the universe are essentially equal, (that is, there is no “center” of the universe) then the universe doesn’t compress into a pancake at all as you near the speed of light; it’s just that the non-foreshortened part of it, the part that matches your current velocity, is farther and farther away from you. But the overall volume will appear unchanged.

 

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Causality Paradox? What causality paradox?

September 11, 2017

I can’t call this real physics, this is just pure and wild speculation. I had a funny idea today about whether or not you can go back in time and shoot your grandfather, thus keeping yourself from ever being born. Ethical questions aside, I thought of a possible solution to the whole “paradox” issue.

First, if you aren’t familiar with the Grandfather Paradox, you can read up on the subject at Wikipedia at https://en.wikipedia.org/wiki/Grandfather_paradox.

Start with the idea that we are always travelling at the speed of light. You, the Sun, the Earth, your brother Bob, everything is travelling at the speed of light through the time dimension, all going the same direction so your relative speed is zero. This is a pretty common concept in modern physics, so I’m not going to expand on that here. Just more physics weirdness.

So, let’s say I get the dubious urge to go murder my grandfather at some time in the past, before I was born. Using some fantastic time machine, I go back in time to when Grandpa was just a young fella and shoot him. What happens then?

Well, imagine that space and time are a 4-dimensional matrix, but that changes made in the matrix can only propagate forward at the speed of light. Remember, that’s how fast we move through time. Eventually, the change (where I no longer exist) reaches the point where I would have gone back in time, but the particles that would have made up my body go shooting forward past that point and never go back. Well, they aren’t “shooting forward” so much as redirecting the world line of their old path at the speed of light. Now, instead of making a U-turn and heading toward their fate with my grandfather, the bullet-magnet, they continue forward in time. The old worldline going backwards collapses/disappears at the speed of light and eventually catches up to where Granddad is, and lets him live. I’m born again! And I foolishly decide, again, to go back in time and kill my granddad.

What does this result in? An oscillation. The world line shifts back and forth between the two realities, carrying the data from both possible realities, like a sine wave on a current. Just as a single electrical sine-wave can contain positive and negative values as it propagates through a wire, so can events toggle on a worldline as that worldline propagates through time. Even past the point where I made my fateful decision, the world line is toggling back and forth; both realities are true, taking their turn as the decision I made causes both of them to be real. The duration of this toggling or oscillation would be twice the duration of the time from when I went back in time to when I snuffed Gramps; the duration of the whole loop.

It’s my belief (not necessarily shared by many others) that we live in a four-dimensional space time that exists perpetually as a 4D matrix, and that what we perceive as our consciousness exists at each point along that worldline. There is the version of you that you perceive now, and the version that existed when you kissed your wife for the first time, savoring the moment you’ve forgotten. Kind of a repetitive immortality.

But what I’m suggesting above is that multiple realities can exist on a single worldline; you don’t need multiple universes dividing every time a critical decision is made or a quantum observation collapses a wave function, or a bit of antimatter goes back in time and changes an existing chemical configuration. Both events occur and exist on a changing, fluctuating, dynamic 4D worldline. There’s the version of you that remembers killing your Grandfather, and the version that never existed, propagating through time, one behind the other forever on the oscillating world line.

The normal view of a 4D worldline is of a static deterministic universe, bound by the future and past configuration of an unchanging worldline. Another view is that every decision, human or quantum, splits the universe into a multiverse, a crowded infinity of infinities. This version allows us to stick with one universe, but to modulate our worldline to allow multiple realities to exist along a single timeline.

Possibly, an outside observer could interface with either version of your reality, based on where he encounters your worldline from his own worldline. Could that be the “collapse of the wavefunction” we talk about? Good grief, that would make the Schroedinger’s Cat conundrum actually possible. Dead and alive! I always thought of it as complete nonsense.

One issue with this model is that each worldline, as it moves from one reality to another, may have to move instantaneously from the collapsed worldline to the new worldline. I think. No real way to test it, that I can imagine. Mmm…maybe pick a subatomic decay process that can have multiple durations, then have someone record the decay time data, then take off (with that data) somewhere at high-speed so your worldline is no longer in sync with the experiment’s original timeline, fast enough that the time separation is greater than the decay time variance. Then, come back and see if the recorded time is the same as it was before; you’ll have two sets of readings of the duration of a single decay, and they might not agree. Wouldn’t that be something?