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A Physicist's View of Time

Famous physicists view of time

"The only reason for time is so that everything doesn't happen at once."
Albert Einstein

Time physics is undoubtedly a very difficult subject to comprehend, but noted time-physicists do their best to help us understand it with their theories, equations, speculations, and scientific findings. Though they may not always agree with each other, time-physicists throughout history have continued to spark new interest in exploring the scientific nature of time. They have provided us with innovative and mind-boggling theories to ponder and explore. Sometimes it may seem overwhelming for the average person to wrap their mind around such ideas. However, the goal of this section is to introduce new ideas on time physics to all levels of readers in a relatively simple and comprehensible way. So explore—dive into the complex world of time physics where you can learn about relative and absolute time, question the continuity of time, meet the experts, and ponder the possibility of time travel.

Two Sides of Time: The Basics of Relative and Absolute Time

There are many ways that people can look at time, but the two major classifications that time tends to be grouped under are relative time and absolute time. The main difference between the two is numbers. When categorizing time as relative, there is no use for numbers: there are no dates or quantitative measurements for the passage of relative time. Relative time, also known as chronostratic time, is determined by looking at its relationship to other events. It is usually measured relative to other known events.

Absolute time on the other hand, is its mirror image since it is based entirely on numbers. Absolute time, also known as chronometric time, is usually measured in years, though it can be based on measurements using a combination of time units.

For instance, let's say you wanted to know the age of a fossil. If we knew the age of the rock the fossil was found in, we could determine the age of the fossil, relative to the age of the rock. This is one example of relative time. If we take this example a little bit further, you might qualify the age of the rock the fossil was discovered in based on where the rock was found, since sedimentary rocks are usually deposited in horizontal layers. Since each layer of sediment represents a period in time, you can date the rock relative to its sedimentary layer and classify its age relative to a period in time such as the Mesozoic or the Paleozoic eras. This is an example of relative time since its age is stated relative to some stratification layer or period in time rather than some definite numeric value or year.

On the other hand, you could carbon date the specimen and come up with an exact age, say 15,000 years old. This is an example of absolute time since you will quantify the age with some specific number.

Scientists use both forms of time measurement in their work today, choosing one over the other whenever it suits their purpose better. Einstein brought new ideas to the field of time physics when he began to categorize time as relative in his theory of relativity. Both are equally important parts of the geological time scale, and thus are important factors in geological dating.

Time Bound: The Science of Time Travel

Related quote goes here.
Said Who
There was a young girl named Miss Bright
Who could travel much faster than light
She departed one day
The Einsteinian way
And came back the previous night

A. Buller (Verma - The Little Book of Scientific Principles).

What first comes to mind when you think about time? Many think about things like: how many hours you may need to finish a certain amount of work, or what time your friends are going to arrive, or why time always seems to slip by so quickly. Do you ever stop to think about time in a more scientific sense? In a physical sense? Listen to how one scientist describes time:
“It turns out that, in some sense, we are all time travelers. As you sit at your desk, doing nothing more than clicking your mouse, time is traveling around you. The future is constantly being transformed into the past with the present only lasting for a fleeting moment. Everything that you are doing right now is quickly moving into the past, which means we continue to move through time.” (Bonsor)
Have you ever considered yourself a time traveler or even pondered this very intriguing notion? If you could travel through time, where would you go? What would you see? What would you do? What could you do?

The science of time travel is not a simple one to describe. In the field of time physics, it is undoubtedly a highly debated topic, riddled with contradicting theories and perplexing paradoxes—making it a favorite topic of science fiction writers (Johnson). Questions about time travel have boggled the minds of scientists and lay people alike for years: What would be the consequence of traveling back in time and changing a major event? How many human lives could be saved? How many disasters could be prevented? What if you traveled forward in time and met yourself 5 years from now. Would there be two of you at that meeting? And if the two of you traveled forward in time another 5 years and met yourselves once again, would there be four of you now? Will humans ever achieve the technology necessary to achieve time travel? Should they even try? Questions like these beget more questions and we don't seem to be getting any closer to answering any of them.

When Einstein developed his theory of relativity, he brought the concept of time into a new light. His findings became the spark that prompted a fascination with the possibility of time travel. Einstein’s theory of relativity defined time as a fourth dimension, thereby transforming three-dimensional space into four dimensional space-time (Johnson). This transition had a significant effect on the research of many experts in the field of time-related physics. One well-known part of the theory of relativity proposed that nothing could move faster than the speed of light. This hypotheses is important for time travelers because it helps explain why a person who travels through space at the speed of light might return home to a completely different world. Why is this so? According to the theory, it's because time slows down for the space traveler in comparison to the passing of time on Earth (Sagan). According to Einstein's calculations, an event that took a day to complete by someone standing on the earth, would only take 12 hours to complete if they were traveling at 87% of the speed of light. If you could build a spaceship that could travel even faster, things get even more exciting. An event (like a birthday) that takes 1 year to complete on earth, would take only 8 hours to complete if you could travel at 99.99995% of the speed of light, according to Einstein. The potential benefits to those who can travel at speeds close to the speed of light are enormous. Traveling at those speeds, you could travel for a week and come back to earth 20 years from now.

Thus, scientists today are able to imagine the distinct possibility of traveling through time into the future. Time travel into the past is another issue altogether and the mathematics here are much more complicated, more theoretical and less hopeful for the time traveler. Whether we want to travel into the future or back into the past, it all comes down to our ability to travel close to the speed of light. How can humans travel into the past, or even significantly far into the future, if they cannot break the speed of light? After viewing the research of various scientists in the field, one will discover that many share the following opinion, despite all of the doubts and paradoxes on time travel: “...the disturbing reality is that the laws of physics do not prevent time travel” (Gawande 58). If this is true, then why haven’t humans started time-traveling yet?

The answer is simple: we still do not have all of the answers on time travel and— more importantly—we do not have the technology. Some theories on time travel focus on the usage of black holes as a means of transport from one time to another. Theoretically, black holes have the ability to create a tunnel through space-time (Johnson). Wormholes constitute a similar theory, which says that two incredibly large masses applying force to space-time could create a tunnel connecting these two points in space (Bonsor). String theory is another theory that relates directly to time travel by accepting the notion of dimensions beyond the four we know: three special ones and time. The fact remains however, that no matter which theory scientists choose to promote, they do not have the necessary technology to turn these theories into anything more than advanced speculations. Some day, scientists may be able to obtain this technology, answer all of the questions and erase the paradoxes, and thereby make time travel a reality.

The Ever-Elusive Path of Time: A Question of Time Continuity

Linear Time
In addition to being relative or absolute, time can also be seen as circular or linear. As mentioned in the "Perspectives of Notable Time Physicists" section, Newton initiated the concept of linear time. Linear time is typically considered a Western perspective on time. It is a perspective on time which takes human influence out of the picture, as it rejects human perception and general feeling of control over the passage of time (Randall). It presents time as an orderly procession from past, to present to future. This also relates to the concept of the arrow of time, which describes time’s constant forward-moving nature. It is essentially reinforcing the fact that time always moves forward and never backward.

A common example of this is a cup which falls off a table and breaks: an occurrence that many people will witness at some point within the course of their lifetimes. Yet we never see a shattered cup rise from the floor and fly back up onto the desk, reassembling itself in the process. The only way humans can observe such a phenomenon is to watch video footage in reverse. Immanuel Kant, a famous German philosopher and expert on the subject (“Immanuel”), has presented the following definition of linear time: “in linear terminology the past is thus determined as ‘what no longer exists’ and future as ‘what does not yet exist.”

When compared to circular time, linear time is both the more widely accepted view of time and also the older one. Circular time is quite different from linear time in that it is cyclical and takes into account the human perception of the passage of time and our role in it. Circular time can be likened to the age-old question: which came first, the chicken or the egg. If you think of time more like a circle, since life is cyclic, there is always a chicken and there is always an egg present. Which came first is relative, similar to the way Einstein's theory revealed that the past and present are relative to some point of reference. Circular time is therefore cyclic and repetitive and tied to the changing of seasons and the cycles of birth, death, and often—in a more religious sense—rebirth or resurrection (“Definitions”). As with relative and absolute time, both of the linear and circular definitions of time are called upon to support different theories, depending on which definition of time is more applicable to that particular theory.

Inside Timeless Minds: Notable Time Physicists

In the field of time physics, there is no lack of scientists and theories working to explain our universe. Is it possible for the average person to comprehend the level of thought of a time physicist? Wouldn’t it be wonderful to be able to see the world through their eyes? We may never be able to possess the genius of Einstein or the creativity of Newton, but we can learn from their perspectives and insights. In this section, we’ll explore the lives and ideas of four of the world’s most notable time physicists: Isaac Newton, Albert Einstein, Erwin Schrödinger, and Stephen Hawking. All of these scientists have changed the world of time physics in their own unique way and have introduced new ways of thinking to the field. Take a look and find out how.

Famous physicists view of time - Isaac Newton

If I have ever made any valuable discoveries, it has been owing more to patient attention, than to any other talent.
Isaac Newton

Isaac Newton: English (born December 25, 1642; died March 20, 1727)

When Isaac Newton was born, he was destined to enter into a world of new ideas. When Newton was young, the church and state were entwined in troubling power struggles throughout England and other areas in Europe. At the ripe age of 12, Newton was attending school and living in the home of an apothecary, where he developed a love for science. At 19, he entered Trinity College at Cambridge University. Eight years later he became professor of mathematics there and continued in that position for the next 27 years. During this time, he catapulted into becoming a key part of the small-scale scientific revolution that was brewing in parts of Europe during this era. Although his primary interest was in the field of optics, his major and most well known contributions consisted of his work done with the laws of gravity and mechanics.

Considered by many to be one of the most important scientists of all time, Newton applied his work to time physics by laying down the foundation for the mechanics and mathematics of time. By presenting us with his basic laws, including his important 2nd law of motion F = ma (force equals mass times acceleration), Newton provided the world of science with a mathematical and linear perspective of time. There was no room for human perception in his formulas. According to his theories, time in relation to space (or distance traveled) could easily be plotted and graphed out on a Euclidean coordinate plane; he saw a linear relationship between the two. In fact, he himself said that, “Absolute, true and mathematical time, of itself and from its own nature, flows equably without relation to anything external” (“How Newton Modeled Time”).

In a way, Newton made time a global concept. His logic was simple enough that it could be applied, as is, to our entire universe with little room for doubt or error. His ‘clockwork universe’, for example, described time as something which remained constant, no matter what speed or location it held in space (“Newton’s Universal”). We recall that in Newton’s time, it was assumed that nothing could travel faster than the speed of light, and consequently, neither he, nor his fellow scientist, ever considered introducing such a possibility when developing their theories on time. As a result, Newton’s theories became outdated when Einstein proposed his theory of relativity. Still, Newton’s contributions were extremely valuable to those who followed.

Famous physicists view of time - Albert Einstein

"The important thing is not to stop questioning. Curiosity has its own reason for existing."
Albert Einstein

Albert Einstein: German (born March 14, 1879; died April 18, 1955)

Einstein was born in 1879 to a South German family. He was born in Ulm, but his family moved to Munich when he was rather young. He developed an interest in mathematics and science at an early age, but if took him longer than most children to learn other common things such as learning how to speak his own language properly. At one point his parents worried that he may have had a learning disability, but Einstein simply had a different learning style and different interests than most. Though Einstein had a reputation for being a poor student through most of his early childhood and in spite of significant doubts his parents had about his academic potential, he eventually astounded them all by going far beyond anything they could have imagined and becoming a leader of leaders in his field.

The most important contribution Albert Einstein made to time physics was his famous theory of relativity. Einstein’s theory of relativity presented a variety of ideas, one of the most important being that time is relative to the physical universe—a physical universe being defined by the presence of movement, matter and consciousness. In accordance with Einstein’s theory, the passage of time will differ for objects which move at different velocities through space. An interesting paradox, commonly referred to as the “Twin Paradox”, arose out of Einstein’s theories. This paradox addressed the problem of relative age between a set of twins. If one twin were to remain on Earth while the other traveled into space, the space-traveling twin would return to Earth younger than the twin who remained on Earth. This is because the space-traveling twin experienced a slowing-down of time while moving through space, which in turn altered the relative ages of the twins when the space-traveling twin returned to Earth. Each twin perceives a different amount of time has passed.

Because we inhabit Earth—a single body moving at one speed—we do not directly notice Einstein’s theory in our everyday lives. Due to the basic nature of the theory of relativity, it was a difficult topic for the average person to understand. In one instance however, Einstein cleverly made his theory clear to the layperson: “When a man sits with a pretty girl for an hour, it seems like a minute. But let him sit on a hot stove for a minute and it's longer than any hour. That's relativity” (Mirsky). Einstein’s theories are widely accepted today and the theory of relativity is often linked to the possibility of time travel in the future.

Famous physicists view of time - Erwin Schrödinger

"We must not wait for things to come, believing that they are decided by irrescindable destiny. If we want it, we must do something about it.
Erwin Schrodinger

Erwin Schrödinger: Austrian (born August 12, 1887; died January 4, 1961)

Erwin Schrödinger was born in Vienna in 1887. While growing up, Schrödinger was passionate about learning, especially when it came to the subjects of science, ancient grammar, and German poetry. It was said however that, like many students in his day and around the world today, he was not particularly fond of memorizing facts and figures. Still he was a dedicated scientist and citizen, and he led a busy life while constantly pursuing new experiences. At the age of 19 Schrödinger entered the Technical College of Vienna. In addition to keeping up his studies, he also served as an artillery officer during the First World War. In the years following his schooling at Vienna, he became an assistant to a variety of physicists who helped him on his way to becoming one of the most important minds in time-physics. During this time he worked on research and the writing of many scientific papers.

In 1935, Schrödinger published a paper describing one of the problems inherent with some of his theories on quantum mechanics. In it he described the following “Schrödinger’s Cat” experiment, which has become one of the most well known paradoxes in quantum theory and was meant to show that quantum mechanics does not always apply to larger and more concrete things. The experiment involves a cat being put into a metal box with a radioactive substance and a vial of hydrocyanic acid. As this radioactive substance decays, there is a 50% chance that it will emit an atom over the course of an hour. If that happens, a hammer will break the vial, a deadly gas will be emitted, and the cat will die. The conflict herein is this: unless they open the box, the observer cannot know if the atom was released and the cat is alive or dead. Therefore, according to quantum law, the cat is both alive and dead at the same time. The logic behind this conclusion goes something like this:

■Before the box is opened, the fate of the cat is based on the state of the radioactive substance.
■Experiments in quantum physics have shown that atomic particles can be in multiple locations at the same time.
Therefore, until an observer opens the box to ascertain the health of the cat at that moment in time, since the atomic particle exists in multiple states, and since the cat's health is dependent on the state of the atomic particles, the cat's health (living or dead) is in multiple states and consequently is both alive and dead at the same time. Schrödinger argued that this was nonsense and that it was an example of trying to apply the laws of quantum mechanics to situation where it shouldn't be applied.

An additional contribution that this Austrian physicist provided to the field of time physics was an equation bearing his name: the Schrödinger equation. It explained how a wavelength changes over a period of time. Quantum mechanics itself gives the probability that a certain measurement will be made, or that a certain outcome will occur (“Schrödinger’s Cat for a 6th Grader”). As a result of all of his diligent and innovative works, Schrödinger won the Nobel Prize in physics in 1933 (“Erwin”) and is known as the father of quantum mechanics.

Famous physicists view of time - Stephen Hawking

"Newton's law of motion put an end to the idea of absolute position in space. The theory of relativity gets rid of absolute time."
Stephen Hawking

Stephen Hawking: English (born January 8, 1942 in Oxford, England)

Stephen Hawking is a renowned physical theorist and professor of mathematics at Cambridge University. Though he is widely known for his contributions to the fields of quantum gravity and cosmology and his study of black holes, he is probably best known for his novel, A Brief History of Time. This book was an instant hit—reaching the bestsellers list in America and Britain and remaining there for several years. He wrote the book for laymen to help them understand questions that were being posed by the scientific community at that time. The popularity of the book and the impressive number of copies sold clearly attest to the fact that interest in the concepts of time and time physics is high and increasing. A Brief History of Time covered a majority of Hawking’s research, including the existence of black holes, the origin of the universe, the nature of time, and string theory. In it he also explored the nature of singularity, or points in space-time where all physical laws break down. Black holes, string theory and singularities have all been closely linked to various time travel theories.