by Shane L. Larson
Zen gardens are a Japanese artform from the Fourteenth Century known as karesansui. Constructed of white sand, stones, and small amounts of vegetation, the karesansui are an abstract expression of the Buddhist perception of Cosmic beauty in the natural world. One of the defining elements of this artform is the raking of the sand, leaving waves and ripples on the gardenscape. Small alterations to the garden, such as placing a single new stone in the sand or changing the location of the stone, has profound effects on the rake pattern and completely changes the appearance of the garden. In many ways, the Zen garden has captured the essence of the most important perception that humankind has ever had about the Cosmos — everything is connected.
One of the most awesome capabilities of science is the power to accurately imagine the future. The Laws of Nature, when coupled with a few observations of the world, can illuminate how small changes to the world affect everything. The complexity of such questions can be enormous, but the ideas and their implications can be simple and profound, like the addition of a single stone to a Zen garden.
Nature has three fundamental constants that govern the way physical systems interact and respond to stimuli. We can imagine a Universe, different from our own, where the values of these constants are slightly different; the Laws of Nature are the same, but the strength of the interactions change. Small changes to three small numbers, like the addition of three stones to a Zen garden, can completely change the nature of the Cosmos. The three constants are known as the Planck constant, the speed of light, and the gravitational constant. The Planck constant governs the scale of interactions on the most minute scales imaginable, controlling how big packets of energy can be and how atoms are allowed to spin and orient themselves to one another. The speed of light establishes the fundamental relationship between space and time. The gravitational constant embodies how strongly bits of matter and energy attract one another, sealing the ultimate fate of the Universe. Physicists believe that the value of each of these constants was fixed during the Big Bang. Many observations have been made trying to ascertain whether these constants have changed over time, but to date every experiment has pointed toward one conclusion: the fundamental constants are constant. But we can imagine what the world would be like if they were not constant, or if they had different values than they have today.
The Planck constant plays a fundamental role in many phenomena associated with the microscopic world of atoms. What would happen if the Planck constant were 400 times larger than its current value, increasing from 0.000000000000000000000000000000000662 in metric units (6.62 x 10-34) to 0.000000000000000000000000000000265 (2.65 x 10-31) in metric units? Making such a simple change, transforming one small number into another seemingly small number would spell the end of atoms in the Universe, leaving us with only free electrons and bare atomic nuclei. The amount of energy it requires to pull an electron away from an atomic nucleus depends on the Planck constant; increasing the value of the Planck constant dramatically reduces the amount of energy required. Consider the most tightly bound electron in the naturally occurring elements: the 92nd electron of the uranium atom, the last electron left when all the rest of its family have been stripped off of the parent uranium. In our Universe, this last electron of uranium can only be blasted away with a gamma ray photon, exceedingly energetic and exceedingly rare. But if the Planck constant were 400 times larger, the same job could be done with an infrared photon, easily generated by the remote control for your television set. Uranium (and every other atom in the Universe) would be ionized by a diffuse background of infrared light; atoms as we know them would cease to exist. You’re reading this because the Universe fixed the value of the Planck constant at 6.62 x 10-34, not 2.65 x 10-31, allowing a few atoms created in the early Universe to merge together and form a little blob that we call “your eyeball.”
Imagine another world where the speed of light was not 300 million (300,000,000) meters per second, but much slower, say 10 meters per second. What would the world be like? There would be obvious differences. If you were out in your backyard playing croquet after sunset, and asked someone to turn on the back porch light so you could see the last wicket, there would be a noticeable delay before the light from the porch reached you. The delay would be more noticeable for the Sun. It would take light about 475 years to make the journey from the Sun to the Earth, a voyage that currently takes the warm light of a summer afternoon only 8 minutes to make. But there would be other important consequences that would be even more profound in our daily lives. The laws of Nature will not have changed, so special relativity would still be important, only now the size of relativistic effects would grow enormously, altering our day to day interactions with Nature. One of the most important effects of special relativity is time dilation, the phenomena that moving clocks tick more slowly than stationary clocks. This phenomena is generally only important for sub-atomic particles, as they spend much of their lives cruising around at a significant percentage of the speed of light. But in our different Universe, where the speed of light is only 10 meters per second, time dilation would be evident on everyday voyages, such as a trip in the family car to visit the grocery store. What would only seem to be 20 minutes to those of you riding in the car, would seem like 45 minutes to someone standing on the sidewalk as you drive by. With a slow speed of light, the time we share with each other changes dramatically depending on how fast we travel about in our busy lives. In this other-Cosmos, when you travel, time slows down for those of you on the journey. In our world, when you take a long business trip across the country and back, you return home to find your children (more or less) the same age as when you left home because the speed of light was long ago fixed at a value of 300 million meters per second, well beyond the speeds that humans experience every day.
What about the gravitational constant? It is incredibly tiny, with a value of 0.0000000000667 (6.67 x 10-11) in metric units. Can changing such a tiny number really change the world so much? Suppose it were twice as large, 0.000000000133 (1.33 x 10-10) in metric units. This would increase the strength of gravity by a factor of two. Each morning, your bathroom scale would read twice what it does now. Carrying a box up a flight of stairs to your new apartment would be much harder. But these are mundane matters; the strength of gravity has an important, if obscure, impact toward life on Earth. About 200 million years after the Big Bang, the first stars began to form. The progenitor of most stars is a condensing object known as a protostar, a violent storm of collapsing gas that hungrily sweeps up loose bits of material that it compresses, under the force of gravity, until it ignites in an explosion of nuclear fire. The continuing force of gravity keeps the cores of the star hot and burning throughout their long lives, until all their hydrogen fuel is exhausted and they die in a cataclysmic explosion known as a supernova. Everything that we know, all the common atoms and substances that you and me and rocks and kangaroos are made of, are created in supernova explosions and cast back out into the Cosmos, where they ultimately form a new generation of stars with their attendant worlds, one of which we call Earth. All of this, is made by gravity.
If gravity were twice as strong as it was today, the parent stars that made the Sun may have collapsed to black holes, never exploding and creating all the carbon and silicon and oxygen and potassium that makes us up. If gravity were twice as strong as it was today, the Sun itself may have been a much larger star, having had the power to suck up more gas into its progenitor protostar. Larger stars burn hotter than the Sun, and would have baked a young Earth to the point where it could never support life as we know it. Larger stars burn much faster, dying spectacular stellar deaths after only millions of years, not billions like the Sun — if gravity was much stronger, the Earth that we know would have been destroyed by the death of the Sun aeons ago.
I’m a physicist because more than 13 billion years ago, the Universe decided the value of the three fundamental constants should be 6.62 x 10-34, 300 million, and 6.67 x 10-11, allowing the creation of atoms that self-assembled into a blob called “me.” The three constants of Nature are single stones, placed in the vast rock garden of the Universe, fixing the patterns of Nature that swirl around them. One small change to their values, and everything that we know may never have existed at all. What a close call.