What is time, exactly?
I have been annoyed to no end by physicists' (Hi, Kamagut) use of the term 'space-time continuum' and the use of hard mathematics to "prove" that time is malleable, ooh time is a stream (implying here that you can travel up and down it. More on this later) ooh time can move faster or slower depending on where you are (they could be having a rather misplaced point here), ooh black holes change time because apparently they can see the way light changes its path (they call it bending here to be clear.1 Wait, it's actually gravitational lensing. Eh, same thing) among other stories.
This has actually annoyed me because I have sat down to think about it and have concluded that these people need to change the way they think about time and rewrite the equations of relativity.
I want to muddy the waters here a little bit before I start: I am a creationist.
Good
First of all, what is the space-time continuum? Is it a must for those to be tied together? If it is, then it is this way: for things to exist, things must be in motion. For you to be alive, your heart must beat. The water in your blood must flow. The electrons and ions in your nervous system must move from one place to another blah blah blah...ad infinitum. Add these pieces of motion to external objects and systems (including other human beings for the purpose of this essay) and you get what? The universe.
What would happen if everything suddenly stopped moving? What would happen if the electrons, quarks, protons and other quantum particles stopped moving? First, all living matter in the universe would die instantly. Second, questions: would the universe collapse? Would it suddenly expand? Would it explode because all this energy needs somewhere to go? Would these events, sequentially, lead to the "big bang"?
Secondly, maybe someone said "time is a stream" to mean once it goes it goes if you get what I mean. However, the recurrence of events makes people think that maybe somehow time ties back to itself and suddenly the past and the future are one. Despite the rampant homosexuality running around the planet, I am yet to meet Alexander the Great or Lot's wife or even see them, so I will relegate this idea to fiction where it belongs (again, you will see why shortly).
This essay touches on a lot of things, wueh! Do I want to think about all of them? I think I have to. Let me see.
First of all (again), I want to speak about light. I am thinking about visible light which runs 300,000 kilometres per second in a vacuum. This light also oscillates, leading to the conclusion that it is a wave. But is it? The photons are particles, right? If you throw a stick in a pool of water and you see it bobbing up and down, is the stick a wave?
Now pretend the stick I mentioned above is a photon of light and the water does not exist but its motion does. What do you get? So, if this particle is moving along happily in some random corner of space and nears a black hole, what will happen? Since the photon in this case also spins in a specific direction, it acts like Earth and creates a force of attraction that makes it liable to be pulled by a strong enough object which is also in motion itself. Thus, on approaching the black hole, said photon gets to a point in space where it feels the black hole's pull but is too far, too fast and too light to be pulled in completely. However, due to the pull, its path has changed so when we look at it, it looks like a footpath which goes round a tree and we can see and say, "Ah! A black hole." But where is time in all this?
At this point, our dear physicists say that time moves faster near the event horizon than, say, a healthy distance away and therefore the equation of special relativity must hold.
But what is time?
I used to think of time as the distance between events, which raises the question: What is an event? An event is an action. Which means, something must move for something to occur. For you to think, your brain cells must necessarily throw calcium and potassium at each other. So, things must move, which also takes time. I know. I know. We are together here. I was also wrong.
So, what is time? Time is the distance between states. By using the analogy of the minute hand of a clock moving from 12 to 6, he says time changed because the state of the clock changed.2
So, what is state? Let us go back to form one. All matter is made up of discrete particles which carry information in discrete units called quanta. Metadata, in short. This information is basically certain characteristics that are observable, even measurable. For example, an electron has a charge which is given a unit of -1 for practical purposes, a direction of spin (like the way the earth spins), an amount of energy (in this case the power of the wave it is riding on) all of which we have tried hard to quantify and have realised, wueh! If you do, the electron's information changes because WE ARE USING METHODS THAT INTERACT WITH THE PARTICLE TO OBSERVE IT! So, the spin reverses and all of a sudden we have ruined a perfectly good experiment. Not to worry, that was not our topic for today.
Now, since this electron (for example) has a given quantum state of spin -1 (this one means left or right. Knock yourself out), charge -1, speed 170000km/s, exists somewhere specific in space and has x amount of energy, we can say time starts when it has those characteristics. Once it moves, at least one of them will change. For instance, it might be on a trough of the wave it is riding on when in the beginning it was on a crest (see? Waves) and be a million kilometres away when we look at it next. What changed? Its state. Since the particle must always be in motion for its existence to make sense, its characteristics will always be changing and as a result we have the phenomenon we call time.
Now you see where creationism comes in. Per the Good Book, the first thing God did was to create time. When He created daytime, he made definite boundaries which could be interpreted as change in state. No light - Night. Light - Day. First day. Simple. The world's information changes as it spins. As it does, information coming in from the universe also changes; we move closer to the sun, we move further away from it, Orion comes into view, we see the dust in the Milky Way, the moon goes to Afghanistan, comes back to Timbuktu and so on regularly enough that we can look at the way light reflects from the moon or where it is in the sky and say, "Ah! Mama Nani is raining tonight."4
So therefore state is information. Since you must move, something about you must change. We interpret the distance between these changes as time.
I am using the word distance since Point A minus Point B is similar to Information A minus Information B.
Now, where were we?
For time travel to occur, we must then have a snapshot of all states of everything in the universe at all times and store them somewhere. This requires that we first create copies of the matter and energies involved and give them these states as they happen. After that, we make it so that these two universes are tied together and one (an intelligent being, doesn't matter who) can jump into the copy at any point and make a change (or not), which change must (or not) reflect in this original universe. Do you see a problem?
Merely interacting with this universe EVEN TO OBSERVE means that its state will change, which makes it a corrupted copy of the original, and if it is entangled with this one? Kwisha sisi.
Do you see why time travel cannot happen? No? Let me show you.
This universe is made up of things which behave as if they were told to behave that way. They have definite characteristics which make them exist in a certain form. These things interact according as they were made to behave. In such an orderly universe, intelligent beings that think (sometimes) have been housed. If these or other beings are allowed to change its state, what will happen to the others? Who will take responsibility?
Let's say you can change the state of the universe perfectly instead so nobody notices you travelled back in time which means you press the rewind button on everything that exists. What now? You have the same problem as before. The mere fact of your existence and/or observation at that point in time changes the state of the universe and affects everything there and downstream.
If you are a 'good' person and somebody "travels through time", then, your state will be affected. Your ancestors might be destroyed entirely.
Therefore, if you are a being with the power to make such a thing happen, you have to impose very hard limits to what can be done within it to prevent chaos from flooding the universe. Would you do it?5
Next question. Does the speed of time change? This one should be obvious. Again, our able physicists have talked about "an observer" when speaking about gravitational lensing and the event horizon which makes sense because if you stand by the road seeing a Mercedes moving at 180 kiloetres per hour you will be like, "Wueh! That car is moving quickly" but if you are inside it you might not notice at all. So, what then?
The measurement of time is an arbitrary activity, much like the measurement of distance. Just as you can measure the distance between your elbow and your middle fingertip and call it a foot (don't) or a step and call it a metre (again, don't), you can measure the time it takes you to jump up and down exactly once and call it a second. The march of time does not change; it is your measurement and comprehension that do.3