and continuously corrected. Any inconsistencies would ruin the system’s accuracy, big time.
And always remember: We’re not talking about the warping of an actual entity called time. We’re noticing only that events unfold at more leisurely rates, or more hurriedly, than they did before, relative to others. This remains a central point. A hawk flaps its wings slowly, whereas a hummingbird’s wings beat furiously. Sure, we could bring our concepts of time into the discussion, yet we needn’t do so. The event is one thing. How we categorize or measure it is another.
For those who may imagine that such “time warps” are only a mind game, a mere theory, the fact is, Einstein’s time dilation even causes death. When cosmic rays (highly energetic particles striking our atmosphere) collide with molecules in the upper layer of air, they break atoms apart like a cue ball smashing a stack of billiards. The resulting rain of subatomic particles includes some that can be lethal to humans if they strike the wrong bit of genetic material. These muons dash through our bodies constantly, causing some of the spontaneous natural cancers that have always plagued our species. Over 200 of these penetrate each of our bodies every second—more if you live higher up, like in dangerous Denver again. The point is, muons, intermediate in mass between protons and electrons, exist for just 2 microseconds before decaying into harmless by-products. And a few microseconds is not long enough for them to make it all the way to Earth’s surface and into our cells, even though they travel a hefty fraction of the speed of light.
Muons should decay so quickly after being created thirty-five miles up, they ought not be able to reach us. They should never arrive here. They should not cause us any trouble. But they do. What we count as a few microseconds becomes a longer period of time to the muons. Long enough to live on and on. Their time has slowed because of their high speed. To us observing it, the muon’s life has been extended—and ours perhaps shortened. Yet from the particle’s perspective, time passes normally.
There are places in the universe where only a single second of events pass while a million years’ worth of activities simultaneously elapses here on Earth. Yet both feel a normal passage of time.
So observers in different places experience out-of-sync sequences. If the rate of the passage of events depends on factors like the local gravity and one’s speed, how can there be a stable commodity called time?
Exploring this, physicists look to see if time is critical, or even has existence, in their physics equations—or whether what has been spoken of as time is merely the fact of change, long represented by the capital Greek letter delta: ∆. Doing so, they find that Newton’s laws, Einstein’s equations in all his theories, and even those of the quantum theory that came later, are all time symmetrical. Time simply plays no role. There is no forward movement of time. Many in the physical sciences thus declared time to be nonexistent.
As Craig Callender wrote in 2010, in Scientific American2:
The present moment feels special. It is real. However much you may remember the past or anticipate the future, you live in the present. Of course, the moment during which you read that sentence is no longer happening. This one is. In other words, it feels as though time flows, in the sense that the present is constantly updating itself. We have a deep intuition that the future is open until it becomes present and that the past is fixed. As time flows, this structure of fixed past, immediate present and open future gets carried forward in time. This structure is built into our language, thought and behavior. How we live our lives hangs on it.
Yet as natural as this way of thinking is, you will not find it reflected in science. The equations of physics do not tell us which events are occurring right now—they are like a map without the “you are here” symbol. The present moment does not exist in them, and therefore neither does the flow of time. Additionally, Albert Einstein’s theories of relativity suggest not only that there is no single special present but also that all moments are equally real.
Philosophers generally agreed. After all, the past is just a selective memory; your recollections of an event are different from mine. Both memories are simply that—signals from brain cells, neurons firing in the present moment. If the past is an idea that can only occur in the here and now, and the future is also just a concept happening strictly in the present, there seems nothing but now. Always. So is there really a past and a future? Or just a continuum of present moments?
This debate is not new. As we’ve seen, several classical Greek writers believed that the universe is eternal, with no origins at all. Possessing such an infinite past with no beginning made time seem meaningless. Eternity, after all, is fundamentally different from “time without end.” Even as long ago as the fifth century b.c.e., Antiphon the Sophist, in his work On Truth, wrote, “Time is not a reality, but a concept or a measure.”
In the town of Elea, Parmenides seconded this in his poem, On Nature, in a section titled “The Way of Truth,” in which he stated that reality, which he referred to as “what-is,” is one, and that existence is timeless. He called time an illusion.
Soon after, still in the fifth century b.c.e, in that same Greek town of Elea, the famous Zeno created his enduring paradoxes, which in the next chapter will provide critical instruction on how to tell the difference between the conceptual realm of ideas and math versus the actual physical world. (This will resolve that old nagging paradox of the tortoise racing the hare, which has been filed in your brain all these years in a section devoted to “miscellaneous mental torment.”) Zeno will also help show us how neither time nor space are actual physical entities.
In sharp contrast to the carefree Greek musings on eternity, medieval theologians and philosophers tended to see God alone as infinite. To them, His creation, the universe, must therefore indeed have a finite past, a specific moment of birth, and an assumed expiration date. By this reasoning, time is part of the cosmos and thus is itself finite.
Enough philosophizing. Though such debates continue today, they’ve been offered only to illustrate how time’s reality, so assumed by the public, continues to be seriously doubted among people with excessive leisure time who ponder such things. More central for us, it is doubted even in the mainstream of science. And it is the science alone that we will now continue to pursue as we heat up our hunt for a definitive resolution to the time business—our first key to understanding existence, death, and our true relationship with the cosmos.
We must shift to the only place in science where a directionality of time is assumed to be needed: the field of thermodynamics, whose second law involves a process called entropy. This natural inclination to go from order to disorder necessitates an “arrow” or direction to time. If such an arrow exists, then time is a real item after all and will disconcertingly tick away the remaining minutes of your life.
We’d better hurry up and get to the bottom of this. We’ll call on real people who helped clarify what’s going on. This odyssey will lead from Parmenides and Zeno, whose world was very different from ours, to nineteenth-century Europe and a name known to every physics student—the brilliant, fascinating, but ultimately tragic Ludwig Boltzmann.
2 http://www.scientificamerican.com/article/is-time-an-illusion/.
ZENO AND BOLTZMANN
4
Life . . . presupposes its own change and movement,
and one tries to arrest them at one’s eternal peril.
—Laurens van der Post, Venture to the Interior (1951)
We should probably begin with Parmenides, who was born around 515 b.c.e. in Elea, on the Greek mainland. He is known for founding Eleaticism, which quickly became one of the leading pre-Socratic schools of Greek thought. But though only small fragments of his principal work—the lengthy, three-part On Nature—survive, there’s really no need to complicate what