What is Time?

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.

What regulates the speed of time here on Earth?

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. However, clocks and cesium atoms 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. What then regulates the passage of time for the crew?

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. 1.62×87 = 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, .53×87=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.

What determines the speed of entropy? Odum and Pinkerton (1955) proposed that the speed of entropy depends upon the efficiency of which energy in a system is transformed. In living creatures, energy is transformed from high quality glucose in carbohydrates to heat during metabolism. This degradation of energy is due to entropy. In a system with high efficiency, the speed of entropy is faster than in a system with low efficiency transformations. In 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 creatures ever existed. There would be nothing to disorganize or decompose. Would there still be such a thing as time?  I would say no. If only lower forms of life existed but not humans, would time exist? I would say yes. But the consciousness of time, just like the consciousness of death, would not exist. The existence of time depends on the energy transformations within living bodies, but is independent of the consciousness of time. Consciousness of time (and also of death) depends on the existence of human brains. Metabolic energy transformations are the essence of life

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.  Others say that the rate that the universe is expanding is a measure of time. Either case makes no difference to the crew on the space ship. 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 grow older is the same as that which would occur on Earth (except if they passed near a black hole in which case they would age more slowly).  But if the crew all died, time aboard the space craft (as humans perceive time) would cease to exist. Actually, time would continue until their bodies decomposed, since entropy is time’s regulator.  Time would cease only when decomposition is complete and entropy is maximum. The existence of time depends on the existence of living beings. Since our galaxy is hurtling through space, planet Earth is a type of space ship. If all life on Earth suddenly ended, there would be no such thing as time, at least as far as the human brain could comprehend it.

Ecological Significance

Why, as an 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. (Rate of power output may be lower on in a young organic farm, but as soil organic matter accumulates, power output may reach levels of chemical intensive farming).


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