Albert Einstein once said, “The only reason for time is so that everything doesn’t happen at once.” I think it would be hard for us to imagine reality without time, but apparently physicists could just as easily describe reality with or without time. Think of an observer sitting on a mountaintop outside of time seeing our meandering along between birth and death as a squiggly line between points A and B.
So much has been written about time, about its being incorporated into the fabric (space-time) upon which are hung the sequins of matter and energy, about the relativity of it, about its being the 4th dimension, about its exploding into existence only after the Big Bang, and about the possibility of traveling forward or backward in it.
But what is time, really? Isn’t it time for a reality check?
Time is just one damn thing happening after another, whether its particles and energy flying out of the Big Bang or a clock ticking away the seconds or our neural synapses firing off in various parts of our brains. Time is not a superhighway you can drive forward or backward on.
Time travel might be theoretically possible, but I wouldn’t hold my breath waiting for it to happen. Given our reality checked definition of time, for us to go backwards in time would require someone to reverse the direction, position, and state of every particle and energy wave in the universe, including you and me, back to what they were at the time he or she wanted to return to. The same level of difficulty would be entailed in travelling into the future faster than we normally move from the present into the future. For us to go forward or backward in time even one moment would require all the energy in the universe. Imagine how much energy would be required to go back 13.8 billion years to see the Big Bang happen: more than all the available energy in our current universe. How about travelling back in time to before the Big Bang? End of the road. Run out of time.
The only way you could travel back in time without affecting me, or vice versa, would be for us to live in separate universes.
If time is just one damn thing happening after another, can we know for certain the sequence in which those things happen, what happens before what? Not necessarily. Einstein shows how two observers, one standing and the other moving, could see two things happening and disagree on which happened first. All that implies is that we should be a little more humble about our measurements, because all our measurements are relative. Can we even know that just one thing has happened? Again, not necessarily. Schrödinger explains how, at a certain level (very small), a thing consists of all its possible states, living and dead, like Schrödinger’s Cat, and only becomes a single state, living or dead, when measured or observed. This has something to do with the paradoxical behavior of light when measured as a wave function or as discreet particles, like photons. According to Quantum Mechanics, at the sub-particle level, all matter exists as a wave function. The wave passes through all the possible states of the sub-particle. When we observe or measure the wave we intersect with it. The intersection of a wave is a point, a particular state. The wave existed in all its states up until the point at which it was observed and it continues to exist after being observed. It even exists in all its states while it’s being observed. Quantum Mechanics works so well at the sub-particle level but there’s no reason it shouldn’t work just as well at the macro level (our level).
A great idea for a Hawaiian tee-shirt: “I’m a wave, so surf me”.