What is Time?
Chapter 1: The Nature of Time
The past existed, but that does not mean it still exists.¹ There is a distinction between having existed and existing now; otherwise, one could use money already spent in the past to pay for something else in the present.² While we possess memories, records, and other evidence of the past, these are all present-day manifestations of past events and experiences.³ In essence, evidence of the past is part of the present. Therefore, although the past existed, it does not exist in the present.
Similarly, although the future will exist, it is not accurate to say it exists now. The future represents potentialities or a range of possibilities yet to be realized.⁴ Consequently, because neither the past nor the future exists in the present moment, only the present moment itself exists.⁵
We can remember past events or anticipate future ones, but these are all mental constructions occurring in the present.⁶ Evidence of past events, such as photographs or historical records, exists now as physical or digital objects.⁷ Technology and science operate not because the future exists, but because the present moment is continuously changing in predictable ways, according to the laws of physics, or logos.⁸
Therefore, only the present moment exists. This present moment is eternal and perpetually changing, and what we refer to as time is a method to measure the rate of the present moment’s change.⁹ This is exemplified by the statement:
“According to the most accurate cesium atomic clock in the world, one second is equivalent to 9,192,631,770 cycles of the radiation produced by the transition between two energy levels of the cesium-133 atom.”¹⁰
Time exists, but it is not something mysterious. Instead, time is a construct we humans have invented and agreed upon to rhythmically measure the pace of space’s change with discrete units in a manner that is useful to us.¹¹ Time is to change what the metric system is to space: a tool we have created to organize our experiences, make sense of the world around us, and measure its rate of change.¹²
Therefore, the so-called “arrow of time” is merely a misnomer.¹³ In reality, the way the present moment changes follows an order governed by the laws of physics, or logos.¹⁴ Logos is the mechanism by which changes unfold.¹⁵ It is not that “time only moves forward”; such a statement lacks meaningful substance.¹⁶ Time does not “flow” or travel anywhere; rather, time is a measurement system we have developed to gauge the rate of change, without possessing any inherent direction — neither backward, forward, nor sideways.¹⁷ Time is to change what the metric system is to space: a tool we use to understand the relative change of phenomena with respect to our experiences.
Chapter 2: Cyclical Change
Change in the universe is predominantly cyclical, and perhaps entirely so.¹⁸ We have been able to devise measurement systems like “time” precisely because of the cyclical nature of change.¹⁹ For instance, one second is defined as 9,192,631,770 cycles of radiation corresponding to the transition between two energy levels of a cesium-133 atom.²⁰ These regular, repetitive cycles of radiation provide a reliable and consistent reference for measuring the rate of change. By observing these repetitive events, we have established various units and standards to quantify and comprehend the ever-changing world around us.²¹
Many living organisms exhibit daily cycles known as circadian rhythms.²² These internal clocks regulate sleep-wake patterns, hormone secretion, and other physiological processes.²³ From birth to growth, reproduction, and death, the life cycles of plants and animals follow orderly patterns that contribute to the overall balance of ecosystems.²⁴
The concept of a day is derived from Earth’s rotation on its axis.²⁵ One day represents the time it takes for Earth to complete one full rotation, resulting in the cycle of day and night.²⁶ The changing seasons, driven by Earth’s axial tilt and orbit around the Sun, bring about variations in temperature, weather conditions, and the behavior of flora and fauna.²⁷ Plants follow specific flowering and fruiting cycles influenced by factors such as day length and temperature, allowing us to cultivate and harvest crops and vintages.²⁸ For example, the grape harvest season signals the beginning of wine production, which itself follows cyclical processes.²⁹
The gravitational pull of the Moon and the Sun causes ocean tides, with predictable high and low cycles occurring throughout the day.³⁰ The Sun undergoes various cyclical changes, such as the 11-year solar cycle, during which solar activity, sunspots, and solar flares follow a recurring pattern.³¹ Astronomical phenomena like pulsars and binary stars exhibit incredibly precise and regular cycles, akin to the ticking of a cosmic clock.³²
Just as the metric system provides a framework to organize and comprehend measurements in space, our time measurement system serves as a tool to understand and navigate the cyclical nature of the ever-changing present moment.³³ Units of time — seconds, minutes, hours, days, months, and years — allow us to quantify and make sense of the rhythms and patterns in nature, including the changing of seasons, lunar phases, solar cycles, and the life cycles of organisms.³⁴
By inventing the concept of time, we can synchronize our actions with the cyclical behavior of the universe, optimize our lives, and predict celestial events.³⁵ Tracking the motion of planets, anticipating the rising and setting of the Sun and Moon, and planning our activities accordingly are all made possible through time measurement.³⁶ This system enables precise and accurate observations and experiments, granting us the power of prediction.³⁷ By understanding the precise ways in which the present moment changes, we have advanced in fields like technology, astronomy, physics, biology, and climatology.³⁸
This regularity showcases the beauty and elegance of the cosmos, enabling us to study and understand it with scientific rigor and predictability, which we harness for technological advancement.³⁹ Our ability to measure change using the time system, and to predict celestial, planetary, and biological changes, is founded on the consistency of these natural cycles.⁴⁰
Time, as employed by scientists, is fundamentally a system of measurement based on cyclical processes. Units of time such as seconds and days are defined by counting repetitions of periodic phenomena. For instance, a second is defined by a specific number of oscillations of radiation corresponding to the transition between energy levels in a cesium-133 atom:
1 second = 9,192,631,770 cycles of radiation of the cesium-133 atom
(BIPM 2019)
Similarly, a day is determined by one complete rotation of the Earth on its axis. In essence, these units are derived from counting cycles of recurring events. When physicists incorporate time into their equations, they are comparing rates of change in processes to these standard cycles, effectively measuring how one process unfolds relative to another. (Rovelli 2018) This practice underscores that time, in scientific terms, is a tool for quantifying change rather than an independent entity.
Chapter 3: Time as a Parameter of Change Across Physics
Across all branches of physics — from classical mechanics to relativity and quantum mechanics — time consistently appears in equations as a parameter for quantifying rates of change. In classical mechanics, time measures how positions and velocities of objects change, as seen in Newton’s laws of motion. (Newton 1687) In quantum mechanics, time acts as an external parameter governing the evolution of quantum states. (Sakurai and Napolitano 2017) Even in Einstein’s theory of relativity, where time and space are intertwined, time functions to describe how processes vary relative to different frames of reference, not as a traversable dimension. (Einstein 1916)
The Absence of Time as a Traversable Dimension
Notably, there is no experimental evidence supporting the notion of time as a traversable dimension. Experiments demonstrating time dilation — such as those involving particle accelerators or precise atomic clocks on GPS satellites — measure variations in the rate at which processes occur under different conditions like velocity or gravitational strength. (Hafele and Keating 1972; Ashby 2003) These observations reflect changes in processes, not movement through a temporal dimension. The so-called “time dilation” is better understood as a discrepancy in the rate of change between two systems due to relative motion or gravitational potential, aligning with the view that time measures change.
Time, as explored in this article, is best understood not as an independent, flowing dimension, but as a sophisticated system humans have devised to measure and comprehend the cyclical and ever-changing nature of the present moment. By recognizing time as a tool for quantifying change, we can better appreciate the intricate patterns and rhythms that govern the universe, enhancing our ability to navigate, predict, and innovate within it.
Now the question is: what is change?
I wrote three articles explaining the nature of change:
Changism: Change and Time in a Presentist Universe https://sergio-montes-navarro.medium.com/change-and-time-in-a-presentist-universe-3aec919829ae
Changism 2: The Bewitchment of Language in Physics https://sergio-montes-navarro.medium.com/changism-2-the-bewitchment-of-language-in-physics-79acaf69757f
Changism 3: Timeless Eternal Change https://sergio-montes-navarro.medium.com/changism-3-timeless-eternal-change-b87ef0e2780b
References
Newton, I. (1687). Philosophiæ Naturalis Principia Mathematica.
Sakurai, J.J., & Napolitano, J. (2017). Modern Quantum Mechanics.
Einstein, A. (1916). Relativity: The Special and the General Theory.
Hafele, J.C., & Keating, R.E. (1972). “Around-the-World Atomic Clocks: Predicted Relativistic Time Gains.” Science.
*Ashby, N. (2003). Relativity in the Global Positioning System. Living Reviews in Relativity.
Rovelli, C. (2018). The Order of Time. Riverhead Books.
BIPM (2019). The International System of Units (SI).
