Time can fly. I noticed it when I moved the past few weeks. Another day gone by, and so many boxes to pack!
I would rather have seen the time fly by during a trip to mountain huts in the French Alps or somewhere by the sea. On the other hand, flying was better than crawling between the boxes and the bubble wrap. Not just because I’ve had enough of those boxes, but mostly because it’s often a bad sign when events unfold like in a slow-motion movie – crawling by time doesn’t always bring anything good.
It is of course psychology, the feeling that time is solidifying or just passing by. Like struggling not to waste, wasting, or wasting time, or bending over to gain or stretch time. Time itself flows inexorably and indifferently.
Has she always done that? That was the thought for a long time. The image of the universe was that of a vast, static and unchanging backdrop in which a universal clock ticked the time. As the famous naturalist Isaac Newton put it in his 1687 Mathematical Principles of Natural Philosophy defined: “Absolute space remains, of itself, independent of any external influence, always constant and immovable” and “absolute, true and mathematical time proceeds by itself and of itself uniformly independent of any external influence.”
This means that space and time also differ essentially from each other: space is and remains and you can travel back and forth in it, but traveling through time is impossible. And unlike ‘here’, ‘now’ is gone as soon as you say the word: time is elusive. Or as Church Father Augustine wrote at the end of the fourth century: “So what is the time? When no one asks me, I know; but if I want to explain it to someone who asks, I don’t know.”
Thread without beginning and end?
What does succeed is measuring durations – of a life, a move or any change in the cosmos. Astronomers and other natural scientists have been doing this for millennia. Each orbit of the earth around the sun takes a year, the movement of the moon is related to the months and the rotation of the earth on its axis defines the day which can then be divided into hours, minutes and seconds. Today, the periodic – continuously repeating – movements of vibrating atoms in an atomic clock record that second with extreme precision. The duration of all those repetitive movements is the yardstick against which to measure the duration of all other changes and movements.
Such time measurements would be impossible in a universe where nothing ever happens. Such a universe must be timeless. In the words of that same Augustine: “If nothing were to pass, there would be no past, if nothing to come, there would be no future, if there were nothing, there would be no present.” But even if in a cosmos all movements and events were chaotic, random and crisscross, you could not speak of time as we know it. If you think about it that way, time is a measure of the very changes that are the – in principle predictable – product of cause and effect.
Matter has arranged itself in galaxies that move further and further apart like currants in a rising dough
In concrete terms, this means that with Newton’s laws you can – in principle – predict very precisely at what time a board will fall to pieces on the floor and how hard the board will fall from your hands during packing. The direction of time is determined by the physical concept of ‘entropy’, which can be seen loosely as the sloppiness of nature and which makes processes such as the breaking of a plate irreversible. Time itself then irrevocably strings together in such formulas all successive and ensuing states, from the fall to the smashing of the board. And so, like a thread of sorts, physicists still see time — even though Einstein has made them think about time very differently. So the question in this series is: is that thread in a circle, is that thread infinite, or does that thread have an end and a beginning?
The short answer is: we don’t know. Physicists, cosmologists, and astronomers only know—quite certain—that the universe itself had a beginning. Their ‘big bang model’ is one of the greatest achievements of twentieth-century natural science. It grew out of Einstein’s new way of looking at clocks and time over a century ago. Because light is the fastest way to transfer information and because the speed of light is finite, there is no longer a shared “now,” Einstein showed. If I blink ‘now’, someone across from me sees that blink just a fraction of a second later – and the further they are, the greater the delay, of course.
In the same way the finite speed of light drives the universal clock out of the cosmos, and all points in space get their own clock. In Einstein’s theory, space and time together form a dynamic space-time fabric into which heavy masses such as stars or black holes sink: they stretch space locally and make clocks run slower locally. And along with countless observations and measurements, that concept of stretchable spacetime led to the idea a century ago that the universe itself is dynamic and stretchable. In other words, that once, 13.8 billion years ago, energy, matter, and space-time emerged from a starting point—that Big Bang. And that matter has since arranged itself in galaxies that move further and further apart like currants in a rising raisin bread dough as space expands.
But whether and how ‘time’ started to run during that big bang 13.8 billion years ago? The early moments of the cosmos are literally shrouded in mist: a glowing mist of charged particles—the building blocks of all later matter—absorbed all light and made the universe opaque. And while circumstantial evidence and theoretical predictions can lift a corner of that veil, they fall short of understanding the very earliest moments. They are just as inaccessible as the memories of the first, saved moments of a life beyond language. Also the mathematical language, of the theory of relativity and of quantum mechanics, can only be used from a later moment, ‘in the beginning’, when something already existed. The big bang itself is a singularity: a limit case about which no statement can be made.
It seems better not to fret too much about the nature of time, about eternity and nothing
If intrepid scientists do talk about what may have happened when, while, or even before our universe began to run “our time,” it’s mostly merry speculation. For example, was the starting point of the universe as we know it one point between many points and was it blown up like a super bubble by an accidental ‘quantum fluctuation’? Have more such ‘bubbles’ been blown and is ‘our’ universe part of a vast array of (potential) universes somewhere in more-than-three-dimensional space, as string theory suggests? Is it a link in a chain of universes that expand, then contract, then decay, after which a new universe bounces out, as mathematical physicist Roger Penrose supposes? Or did it emerge as the bulge of another universe and then be cut off like a drop in a lava lamp—a scenario physicist Sean Carroll has suggested?
Five centuries ago, Erasmus mocked in his Praise of Folly already with the contrast between what humans are capable of and what the universe is: „They [de natuurfilosofen] build innumerable worlds as they measure the sun, the moon, the stars, the orbits of the planets with a ruler or tape measure, […] as if they had been secretary of nature itself, the architect of all things, and as if they had come to us from the assembly of the gods.” And despite the success of the big bang model, it is still a hopeless task to really fathom the universe and time: from Earth we cannot see until, let alone beyond, the big bang. And the radius of the ‘visible’ universe is limited by the distance light has been able to travel in 13.8 billion years. What lies further or further back remains obscure.
Brain like galaxy
So it seems especially better not to fret too much about the nature of time, about eternity and nothing, and whether the two might be the same. At best, thinking about this helps to put things like moving boxes and bubble wrap into perspective. At worst, it will drive you crazy. Either way, you’re left with a sense of powerlessness and insignificance: what is a life in relation to 13.8 billion years and everything we can’t know beyond that?
At the same time, the same science that comes up with such intimidating facts and with which Erasmus somewhat poked fun may also give some courage. In his recently published book Fundamentals Nobel laureate and theoretical physicist Frank Wilczek calculated how short a (conscious) thought lasts and how many thoughts people can have in their lives. It will vary from person to person, but Wilczek’s estimate was approaching the billion. That would also include about 100 billion visual impressions – and that number is approaching the number of stars in our Milky Way galaxy. In other words, human life may be less than a fiber in a 13.8 billion year stretch of “time thread”, yet in everyone’s head, and without even being able to pinpoint its exact beginning, a Milky Way galaxy is unfolding. thoughts and impressions – a universe unto itself.