Is Time Reversible?

by Madeleine Kando

I was in the midst of a belated spring-cleaning in my house and suddenly found myself confronted with boxes full of photographs. The past was oozing out of those boxes and I couldn't stop the flow. Being the child of a photographer, this is hardly surprising, but it really felt like a tsunami, to the point where I had to remind myself that these snapshots weren’t real. These moments were gone, flushed away in the stream of the river of time.

Since the birth of photography, the past has had free entrance to the present; no more borders so to speak. Like the Schengen Agreement between the EU countries, the past can go anywhere it pleases, even into the future if it wants. My grandson will be rummaging through these boxes, wondering what happened to this young, beautiful 20-year old woman and how she managed to turn into this old, wrinkled person whom he calls ‘Oma’.

Before the birth of photography, people had to rely on rare and expensive paintings to look into the past, which most of them couldn’t afford. The majority of people relied on their memories to conjure up the past, but otherwise it just stayed conveniently hidden. The past knew its place and didn’t infringe on the present.

But what IS the present, really? Doesn’t the present, as soon as it appears, become the past? By the time I type “p-a-s-t,” the point in time I am referencing has already past. The present is never really there, is it? (See: There is no Now)

People say that the past and the future don’t really exist. The past is gone and the future hasn’t happened yet. So if the past, the present and the future don’t exist, how can time exist at all?

Boy, I am really trying desperately to avoid something here. If I were younger, I wouldn’t bother with all this hypothetical rigmarole. I would just live my life and not try to justify what happens to us as time passes. But since I am NOT younger and I have enough time on my hands to bore you with stories about time, let me go on.

According to the block universe theory, all space and all time (the past, the present and future) exists at once. If you could look down onto ‘space-time’ from a large distance, you could see time and space spread out, starting at the Big Bang all the way into the future.

Imagine a loaf of bread (three-dimensional space), which you can cut into slices. Depending on where you exist on the loaf, your slice of ‘present’ could coincide with Beethoven’s ‘present’, your twin sister’s ‘present’ or your future grandchildren’s ‘present’. They are all out there, co-existing.

So in that kind of universe, I could sift through those boxes full of photographs, but they would contain an infinite amount of photographs, including many taken in the future. Some of them would be shots when I am 90 years old, some of them showing my grandson’s graduation from college in 2040, some of them of my great-granddaughter celebrating her birthday on Mars in 2070.

It’s all fine and dandy to talk about loaves of bread, no matter how you slice it (no pun intended), the block universe theory doesn’t explain why, for us mere mortals, time seems to flow in one direction. Why do I remember the past and not the future? Why do I feel my butt getting soar, the longer I sit typing this story? It’s due to the schizophrenic world we live in. Quantum mechanics tells us that time is reversible, which means that on a sub-atomic scale, time can go either forward or backward.

So, how come I am not reverting back to the wrinkle-free diva that I was 30 years ago?

This is due to the difference between quantum mechanics’ time reversibility principle and the second law of thermodynamics, which says that entropy (read chaos), increases over time. On a day-to-day scale of our existence, time, unfortunately is not reversible. Buildings decay, clutter in your neatly organized office piles up and our bodies decay over time. That’s why time flows one way and we don’t find pictures of ourselves as 90-year olds in our family albums.

It’s really all the fault of the uncertainty principle of quantum mechanics. Particles aren’t sure where they are or whether they are at all. They only have ‘probabilities’. It is as if they are waiting for something else to tell them what to do. When they find another particle, they ‘entangle’ themselves, (see: New Quantum Theory Could Explain the Flow of Time), like 2 lovers in an embrace, and no matter how far apart they are, they will always know what the other one is doing. Einstein called it ‘spooky action at a distance’. A cup of hot coffee left standing in a room will eventually cool down until the coffee and the room will reach equilibrium, where both will have the same temperature.

So, my body increases in entropy because over a lifetime it entangles itself with my surroundings. I eat, breathe, get upset about my phone bill and worry about this and that. If I lived in a vacuum, I probably would not age that fast, but since the universe is going from a state of low entropy (the Big Bang) to a state of high entropy (the future) and I am what is called an ‘open system’, my body is subject to the same laws as the universe, hence the arrow of time.

But let’s say that my body could spontaneously rejuvenate itself. Would that mean that time is reversible? The reversal would not erase the event of my body ageing. The rejuvenation would be a new event, which happens after it. Time would just march on, it wouldn’t reverse itself.

No matter how you look at it, we are stuck with the irreversibility of time, for better or for worse. It’s time we accepted that fact. leave comment here