All Our Yesterdays; All Our Tomorrows

We are all familiar with the concepts of ‘yesterday’ and ‘tomorrow’. We probably use the terms all the time in daily conversation and correspondence. But exactly where do we find ‘yesterday’ or ‘tomorrow’? What exactly is ‘yesterday’ or for that matter ‘tomorrow’? When exactly is ‘yesterday’ or ‘tomorrow’? We use the terms loosely, but pinning them down is elusive.

Actually, to start the ball rolling, the concepts of ‘yesterday’ and ‘tomorrow’ are totally artificial since your today is already someone else’s tomorrow, or someone else’s yesterday, depending on the relative time zones you and that someone else inhabit. Rather, there is a universal ‘now’ (even if it’s noon in one place and midnight 180 global degrees opposite), and at that point defined as ‘now’ there’s what’s past ‘now’ (history) and what’s still ahead of ‘now’ (the future). However, since we are all familiar and comfortable with the terms ‘yesterday’ (history), ‘today’ (now) and ‘tomorrow’ (future), let’s stick with that though they are unnatural time units since they are artificial distinctions or inventions by humans. Other unnatural, artificial, meaningless, manmade time divisions include the second, minute, hour, week, month, decade, century, and related. But there are some natural time divisions: the ever varying day-night cycle and the broad yearly cycle of the seasons are reflected in the natural world, from annual tree rings to the awake-asleep patterns of wildlife. The Lunar cycle is another natural time unit that influences life on Earth but one that has no corresponding manmade equivalent.

Anyway, even though an artificial concept, where does ‘yesterday’ reside? Where are all our yesterdays? Where does ‘tomorrow’ reside? Where are all our tomorrows?

Let’s consider ‘yesterday’ first, but perhaps one needs to start off by distinguishing between a personal ‘yesterday’ and a generic or universal ‘yesterday’, a ‘yesterday’ that contained all things that happened ‘yesterday’ throughout the entire universe.

When it comes to ‘yesterday’, and the day before ‘yesterday’ and the day before that, etc. you could say ‘all our yesterdays’ resides in what someone tells us happened, or what’s recorded in a book or newspaper, or what’s on tape as in a radio show or TV news bulletin. Yet, if you hear that person, read that article, see that TV program that details all things ‘yesterday’, you are hearing, reading, seeing that ‘yesterday’, today, so you are experiencing ‘yesterday’ today. That’s not what we really mean by ‘yesterday’. 

What happened ‘yesterday’, even if you find out something about ‘yesterday’ today, ultimately resides in your mind and in your memory. That’s what makes ‘yesterday’ really real to you. But ‘yesterday’ is even more real if you directly experienced ‘yesterday’s’ happenings ‘yesterday’. Your ‘yesterday’ is your past; your past is contained in your memory.

But where does ‘yesterday’ reside after the oldest person alive who can remember or recall a ‘yesterday’ beyond the recall of any other living person, dies? Then records that detail all our ‘yesterdays’, say an historical museum exhibit, are only experienced afresh today. There’s no way you can deal with a ‘yesterday’ in ancient Egypt in the same way that an ancient Egyptian who lived through that ‘yesterday’ dealt with it.

A universal ‘yesterday’ suggests that not everything that belongs to ‘yesterday’ is known to other people or is written down or otherwise observed or recorded. In fact most of what happened ‘yesterday’ is in total oblivion to all and sundry. 

What if there was absolutely nothing to preserve for posterity an event that happened ‘yesterday’, say a raindrop impacting the middle of the ocean and there’s not even a fish around to see it splash. Or perhaps a meteor impacted the far side of the Moon or several hydrogen atoms fused to create a helium atom in the core of our Sun releasing a photon which has to ‘fight’ it’s way to the surface and escape, but that takes thousands of years, or if inside a faraway star in a faraway galaxy that photon wouldn’t be visible to us (or our descendents) on Planet Earth for maybe millions of years, if ever (since 99.999% of such photons will bypass Earth). Unless there is a cosmic consciousness, that photon will go unobserved and unrecorded, in which case, did the event happen? Does the photon exist? In fact, ‘yesterday’, 99.999% (add at least 100 more 9’s) of events that transpired in the greater Universe went unrecorded and unobserved. So the historical record of ‘yesterday’ is grossly incomplete, unless again you wish to argue that unobserved, even by the humblest of microbes, means it didn’t happen. It’s a variation on the old ‘if a tree falls in the forest and there’s nothing or no one there to observe it, did it make a sound’?

In any event, perhaps this photon event is an example of ‘yesterday’ and ‘tomorrow’ merging – a ‘yesterday-tomorrow’ connection. A photon created ‘yesterday’ (sometime in the past) but not observed until ‘tomorrow’ (sometime in the future) is still just a single timeline event. In fact, ‘yesterday’ and ‘tomorrow’ are always linked because what happened ‘yesterday’ has a direct causality bearing on what will happen ‘tomorrow’. So in one sense ‘yesterday’ resides in ‘tomorrow’, and ‘tomorrow’ will in turn reside in tomorrow’s ‘tomorrow’. On a human level, a dance between the sheets ‘yesterday’ can result in quite another event nine months worth of tomorrows later!

Where does ‘tomorrow’ (the future) reside? Well, as hinted at above, the future resides in what happened ‘yesterday’. That’s the generic or universal future. What of your personal future? Where does that reside? There’s only one place your personal future resides – inside your mind.

You can imagine the Sun rising ‘tomorrow’, but until it actually does happen that event is all in your mind, but of course when it does happen it’s no longer ‘tomorrow’ is it? ‘Tomorrow’ never actually comes around, just morphs into today. But sooner or later all your personal mental ‘tomorrows’ come to an end, at least that’s the accepted wisdom.

Your future ceases when you’re declared brain dead, or does it? Not entirely, for each and every elementary particle (electrons, etc.) that makes up what was you in your past still has a future – another case of the ‘yesterday and tomorrow’ connection – as those bits and pieces have had as many ‘yesterdays’ as there were ‘yesterdays’ and will have as many ‘tomorrows’ as the Universe allows for. Some of those bits and pieces were no doubt once part of a ‘yesterday’ pre-you life (or even non-life) form and will no doubt become a part of a post-you ‘tomorrow’s’ life form (or non-life form), so you were part of someone or something else’s immortality and you in turn will be immortal as bits of you will become incorporated into other pieces of matter and energy, ‘tomorrow’. 

In summary, your personal ‘yesterday’ is just a memory, housed and locked away in your mind. Your personal ‘tomorrows’ are just patterns of thought and probabilities, possibilities, even near certainties, but only near certainties as nothing is ever set absolutely in concrete (death and taxes excepted). What may, or may not have happened unobserved in your non-personally experienced ‘yesterday’ resides in your imagination. What may or may not happen unobserved outside of your personal world ‘tomorrow’ is also within your imagination. So where does your ‘yesterday’ and ‘tomorrow’ reside – in your mind and nowhere else.

Time & Time Travel: Part One

WHAT IS TIME? ‘What is time?’ exactly is a question that has been pondered and debated for probably thousands of years by some of the finest minds ever produced, without any definitive resolution. So, I’m NOT going to pretend that this is THE ANSWER – the be all and end all to the question. It’s my thoughts, which hopefully are as valid as anyone else’s!

It has been said that time is just nature’s way of preventing everything from happening at once! But the word ‘happening’ is significant because if something happens, something changes. To my way of thinking, time is synonymous with change; time is a measurement of change; change gives the concept of time tangible meaning. If nothing ever changed, if nothing ever happened, it would be meaningless to talk about time. Time is just our informal perception or more formal measurement of rate of change. Rates of change vary depending on how fast you travel relative to some other frame of reference (Theory of Relativity) so the time intervals that measure that rate of change vary accordingly. I also can’t help but wonder whether, speaking of things relative, whether one could insist on a constant rate of change that’s made constant because your rate of time varies, or the more common view from day-to-day experience that rate of time is constant but rate of change varies.

It’s not difficult to understand why you are not aware of time passing when you sleep. It’s because you’re not aware or cognoscente of anything changing while you’re asleep. In fact, sleep is a way of achieving time travel. You go to sleep at 11 pm. Next thing you know its 7 am and you’ve traveled eight hours into the future seemingly instantly!

Thusly, I conclude that time doesn’t have a separate reality. I mean you can’t weigh time, it has no mass, it has no charge or energy, it isn’t a force and has no particle associated with it, you can’t put time to any physical use, nor can you manipulate time. You certainly can’t bottle and sell it! It’s about as intangible a something as the Universe allows.

Did time exist before there was anyone around to put a label to it? I mean in a pre-life era, change certainly took place – rocks eroded, the tides ebbed and flowed. But was there time? I suggest the answer is no in that it takes a certain level of intellect to recognize change or rate of change. A rock doesn’t perceive time, nor does the beach upon which the tides act. The changes are physically real enough, but it takes something as complex as a living organism (not of necessity just a human organism) to perceive and understand change, and rate of change, which – human beings – for lack of a better word we call it all happening in a concept called ‘time’.

By analogy, there is the oft quoted puzzle of there being this tree in a forest which falls. Does the falling/fallen tree produce any sound if no one (meaning humans) is around to hear it? (Of course there would be animals (bears, deer, possums, birds, etc.) that would hear the sound, but let’s suppose that the forest contains just plants which I assume we can agree on, can’t hear. Now regardless of whether any animals are around or not, the falling tree will produce vibrations in the air (usually air, but vibrations can be equally transmitted in a liquid or solid medium). But vibrating air isn’t by itself sound. Sound is the perception (and possible interpretation) of those vibrations, and that takes a detection device and software (ears and a brain). So, there is no sound without ears and a brain, although the vibrating air is quite real regardless.

Time, to by way of thinking, is akin to sound; change is akin to the vibrating air. The former two are perceptions of physical events; the latter two are the real physical events.

You’d think that therefore time wouldn’t exist in a vacuum or at a temperature of absolute zero, as how could anything change in a vacuum which contains nothing or at absolute zero when all motion ceases? Ah, enter the weird and wonderful world of quantum physics and discover that quantum activity, happenings, change, motion, etc. exists even in a perfect vacuum and even at absolute zero. Therefore, time exists as well. There seems to be no way to ever shut down quantum activity, so we’re in no danger of ever having our perception of time cease.

The shortest (quantum) unit of time possible is just that interval below which no possible change can happen. In other words, even the quickest ever possible change one can imagine takes an absolute minimum amount of time.

Change also implies there must be causality – there must be a cause that produces an effect, or in other words, something is affected by something else that occurred previously. Going from cause to effect implies a change and a time interval must have taken place into which that change fits. This introduces the commonly used phrase ‘arrow of time’. If time is our perception of change, then what is the ‘arrow of time’? Methinks it’s the reality that on the macro scale at least change happens only in one direction – cause precedes effect; effect follows cause, and that’s change. Examples of such one way cause and effect change include dropping the china cup and it breaks. A broken cup does assemble itself and then leap off the floor into your hand. Humans tend to be conceived, get born, grow up and age. Hair turns gray (or falls out), you get wrinkles and liver spots, and you die. You don’t rise from the grave, re-animate, and age backwards towards childhood and pop back into the womb! A hot cup of coffee cools off to room temperature. A cold cup of coffee doesn’t heat up by itself; even if there’s potential energy enough in the environment (air molecules flying around) to theoretically heat it up.  In other words, you can’t unscramble (or un-boil) an egg. 

Further readings about time:

Lockwood, Michael; The Labyrinth of Time: Introducing the Universe; Oxford University Press, Oxford; 2005:

PRESENT TIME: THE CONCEPT OF ‘NOW’: Does the present actually exist? We speak of it was if it does. But does it? Now I’m sure there’s no debating that there is a past, and that there will be a future. I’m sure there’s no debating that five years ago exists in the past; five years on from when you read this is clearly the future. What about five months ago, or ahead?  What about five days or five hours or five seconds? Is half a second ago the past? Is half a second hence the future? Of course it is. In fact, I suggest you can split units of time ever shorter and shorter, but still admit that ‘ago’ means past; hence means future, even if 0.000005 of a second ago really is past, and 0.000005 of a second hence is the future. So where comes the ‘now’ or the present?

While there is a past, and will be a future, there really does exist a present. There apparently is such a thing as the shortest interval of time and nothing shorter can exist in reality. That shortest interval of time is known as Planck-Wheeler time, below which time as we know it ceases to exist. It’s about 10 to the minus 43^rd of a second. That’s how long your present lasts for! One Planck-Wheeler time unit behind you is now forever locked in as part of your unalterable past. One Planck-Wheeler time unit ahead, is still part of your malleable (free will?) future.

Even without resorting to quite such a tiny present, physics logic suggests that you really are an isolated individual that cannot share the present with the rest of the world. Lets imagine this couple, say we call them Clive and Jane, sitting down for their evening meal. Clive says to Jane, “pass the salt please darling”. Now Clive utters that phrase in his present and Jane hears it in her present. But both presents aren’t simultaneous. When Jane hears it in her present, it’s simultaneously Clive’s past because it takes time for sound to travel from voice to ear (and light from mouth to eye). Actually, when Jane hears the word “salt”, “pass the” is already in her past while “please darling” is still in her future. In other words, Clive and Jane can’t ever share the same present even though both pass through identical simultaneously now’s.

Here’s a form of time travel. When Jane looks in a mirror, the image she sees in her present is actually of herself from her past – an ever so slightly younger version of herself because it takes an interval of time for the light to be reflected off Jane, onto the mirror, reflected off that, and back to Jane’s eyes.

In summary, nothing you see or hear has the exact same reality that you perceive in your present because there has been a time lag and things change over time – even incredibly short intervals of time. A common example is looking at a distant star. The star you see in you’re here and now isn’t the same star that exists in that same here and now. You’re looking at a star, which, for all you know, just may no longer exist!

Of course you do live your entire life in the actual ‘now’ – you certainly don’t literally live in any part of your past nor your future. Your life, your lifetime of ‘now’, is a string of Planck-Wheeler time units.

To be continued…