What is Time?
What is Time?
Most people would say that “time” is something measured by a clock. Physicists, in an attempt to be more precise, say that a second is equal to 92 billion vibrations of a cesium atom. Digital clocks are based on the vibrating frequency of a quartz crystal in the shape of a tuning fork. All digital watch designers use the same frequency, one that is too high for use to hear. At this frequency, the prongs vibrate 32,768 times every second. However, clocks, vibrations of cesium atoms and quartz crystals are merely a measure of time. They do not regulate the speed of time, nor even inform us about the nature of time.
Time is an artificial human construct, based on the rotation of the Earth on its axis, and the rotation of the Earth around the sun. It offers a convenient way to schedule meetings. On a space ship beyond the solar system, there is no sun rise nor sun set, but the crew still uses clocks to indicate bed time, meal time etc. But if their clocks suddenly stopped, would time still exist out there in space? Time as conceived here on Earth would not exist. The rotation of planet Earth light-years away from where they are in space would be meaningless for the crew. Nevertheless, the crew does get older, so obviously time is passing for them. They are beyond the solar system and without functioning clocks or cesium atoms. Their only measure of time for them is their rate of metabolism, the rate at which they age.
What Regulates the Speed of Time?
Your age is defined as the amount of time that you have experienced. The amount of time you have experienced is equal to the number of times you have lived through a rotation of the Earth around the sun. As I write this, I am 87 years old according to Earth time. I have experienced 87 rotations. If I were living on Venus, time would pass more quickly. I would age faster, since a year on Venus is equal to only 225 Earth days. I would be 141 years old (365/225 = 1.62. 1.62x87 = 141). If I were living on Mars, time would pass more slowly, and I would age more slowly. A year on Mars is equal to 687 Earth days, so I would be 46 years old (365/687=.53, .53x87=46).
Does this mean that if I wanted to live longer, I should move to Mars?
No, because time as we think about it here on Earth is relative to this planet on which we are living. If I lived on Mars, and thus was 46 years old, I still would look and feel like an 87-year-old on Earth. If I lived on Venus, I still would take a walk every day, even though I was 141 years old.
So from the point of view that time is relative, we could say that the speed of time depends on the planet on which we live. But from the point of view of aging, it is not at all relative. It is deterministic, and depends on the rate that our biological systems deteriorate, and that depends on the speed of entropy, the tendency of everything to disorganize and decompose. Time will end when entropy is maximum.
Einstein concluded that space and time, rather than separate and unrelated phenomena, are actually interwoven into a single continuum that spans multiple dimensions. Gravitational pull regulates the speed of time throughout the universe. The closer one is to a black hole, the slower that time will pass. If a space ship left planet Earth, passed close to a black hole, and then returned, the crew would have aged less than people remaining on Earth. The crew’s great grandchildren may have already passed away.
The Speed of Time
Thermodynamic theory says time is the rate of entropy, the rate of energy transformations from energy in the form that can perform work to dissipated energy, commonly known as heat. What determines the speed of entropy? Odum and Pinkerton (1955) proposed that the speed of entropy depends upon the efficiency with which energy in a system is transformed. In living creatures, energy is transformed from high quality glucose to heat during metabolism. In a system with high efficiency transformations, the speed of entropy is faster than in a system with low efficiency transformations. Between humans, there is only a small variation in the efficiency of transformations. However, between humans and other animals, the difference in efficiency can be much greater. For example, dogs age about five times faster than humans because the efficiency of their energy transformations is higher. The efficiency in elephants is lower.
But now suppose that neither I nor any other living creature ever existed. Would there still be such a thing as time? The answer would have to be no, because there would be nothing to disorganize or decompose. If only lower forms of life existed but not humans, would time exist? The answer would have to be yes, since the existence of time depends on the energy transformations in living bodies. The existence of time depends on the existence of living beings. If all life on Earth suddenly ended, there would be no such thing as time.
Some scientists say that time is independent of life. Entropy is continually degrading our solar system, and the sequence of events that contribute to the degradation is the essence of time. So the rate that the sun is burning out is a measure of time, but that is not a very practical measure. Others say that the rate that the universe is expanding is a measure of time. They say that the universe is about 13.8 billion years old. The problem here is that our solar system did not exist until 4.5 billion years ago, and life did not exist until about 3.8 billion years ago. Before then, there was no such thing as a “year”. If time does not exist in the absence of life, or before the birth of the solar system, how can astronomers say that the universe is about 13.8 billion years old? It is a meaningless statement.
Could evolution of life in a distant galaxy have proceeded more rapidly than evolution here on Earth? This could mean there are more intelligent forms of life elsewhere in the Universe with greater capabilities for space travel.
From outside the Universe, the speed of time is absolute, so all life has had equal time to evolve. But according to Einstein, time is relative and depends upon the movement of galaxies in space relative to each other. A billion years could pass more rapidly in a distant galaxy relative to a billion years here on Earth, so creatures that exist there today would have had more time to evolve. But while there could be higher forms of life in other galaxies, it is unlikely they could visit us because the galaxies are moving away from us at the speed of light or faster. Within our galaxy, there could be forms of life that evolved as they did here on Earth, but the nearest exoplanet is 4.2 million light years away. It would take evolutionary time to get there.
Ecological Significance here on Earth
Why, as an earth-bound ecologist, am I interested in time and how the speed of time is regulated? Because it bears upon Odum’s hypothesis that it is the efficiency of energy transformations that regulates the speed of time, and that management of resource systems such as agriculture are more efficient when energy transformations are slower (contrast industrial agriculture where transformations are fast but inefficient, with organic agriculture where transformations are slower but more efficient). His “Optimum Efficiency for Maximum Power Output” means the efficiency of a system that is maximizing power output (productivity), such as a monoculture of corn supplied with high inputs of fertilizers and pesticides. It is a low efficiency system compared to an organic farming system with low energy inputs and high efficiencies of energy conversions but lower power output.
Odum, HT, Pinkerton RC 1955. Time’s speed regulator: The optimum efficiency for maximum power output in physical and biological systems. American Scientist, Vol. 43, No. 2 pp. 331-343
I found your forum only today, and the first I saw was this question. I have also thought about it a lot, and the results have been laid out in my book "What a Coincidence! On Unpredictability, Complexity and the Nature of Time" ( https://link.springer.com/book/10.1007/978-3-658-40671-4).
- In this book, I am trying to introduce average readers (even such readers who have no natural science background, but are perhaps economists, literature science educated, teachers, philosophy lovers with no idea about physics or else) into non-equilibrium thermodynamikcs and entropy, finally culminating into a new hypothesis about the question"what is time".
My hypothesis isnot so far from what you wrote ("time is the rate of entropy", "speed of entropy"). My proposal is:
- Time is an emergent phenomenon *caused* (brought to existence) by the flow of entropy. That means, if a lot of entropy is flowing, then a lot of time flow is generated; if less entropy flow is happening ==> less time. In equilibrium, when a system came to equilibrium standstill, no entropy flow (no change in entropy) ==> no time.
Your example with Mars and Venus (apart from inhabitability) does not satisfy me, for several reasons. In my hypothesis, the core is: time is not a phenomenon which is identical everywhere, but dependant upon entropy flow.
- hence in a slow moving glacier, time is slow;
- in and out of a slowly growing plant like a 5,000 years old pine tree in the Californian White Mountains, entropy flow is small (not "slow", but "small", small amounts of J/K units), while in a quickly growing bamboo in China, a lot of entropy is generated ==> time is passing by very quickly for this bamboo - but not for us as observers!
I would be happy to send you this special chapter in my book, if you like.
Dr. Bernhard Wessling