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science of time & time dilation

The Philosophy of Time and Time Travel – Part 1/2

Categories, Time Travel, , , ,

This is taken from Appendix 4 my new book, How to Time Travel, to be published by early September 2013.

What does philosophy have to do with science? The answer is simple. Your philosophy of time will determine whether you believe time travel is even a scientific possibility. Of the three major philosophical schools on time, only one allows for the possibility of time travel to both the past and future. From this standpoint, it is critical that you know the major philosophies of time and know where you stand on the subject.

Philosophers have been pondering the nature of time for thousands of years. A philosophy of time weaves through almost every ancient culture. For example, the earliest view of the nature of time by a Western philosopher dates back to ancient Egypt and the Egyptian philosopher Ptahhotep (2650–2600 BCE). Indian philosophers and Hindu philosophers also wrote about time dating back to roughly the same period. The ancient Greek philosophers, such as Parmenides, Heraclitus, and Plato, wrote essays about the nature of time roughly around 500 BCE to 350 BCE.

Many early writers questioned the nature of time, the cause of time, and the unidirectional flow of time, often referred to as the “arrow of time.” One of the most interesting aspects when studying the philosophy of time is that some cultures, like the Incas, dating back to about the thirteenth century, considered space and time woven together. Centuries before Einstein published his now-famous special theory of relativity, which scientifically unified space and time (i.e., spacetime), the Incas philosophically unified space and time into a single concept called “pacha.”

There is a question about time that has ancient roots and that continues to trouble modern scientists and many religions, namely: Did time have a beginning? Through the ages, philosophers and scientists have struggled with this question, and no widely accepted answer has emerged. Not surprisingly, the “time had no beginning” camp, which originated with the ancient Greeks, held solid ground for over several millennia. The Greeks were formidable philosophers. However, the emerging world religions, including Judaism, Christianity, and Islam, slowly chipped away at the Greek philosophy of an infinite past. They simply taught that a deity made the world, and this suggests a beginning of time. Religious philosophers backed these teachings. Christian philosophers, such as John Philoponus, Muslim philosophers, such as Al-Kindi, and Jewish philosophers, such as Saadia Gaon, argued mathematically that infinities do not exist in reality. If you accept this premise, logically you are backed into a corner and must concede that time had a beginning. In other words, if infinities do not exist in reality and are merely a mathematical construct, then time cannot have an infinite past. This argument was refined and became known as the “argument from the impossibility of completing an actual infinite by successive addition.” Simply stated, you cannot complete infinity by adding successive events. Since an infinite past would imply the addition of success events, it ruled out an infinite past. Some notable scientists aligned with this thinking, the most famous today being Stephen Hawking, who argued that time began with the big bang. Dr. Hawking believes that events before the big bang have no observable consequence. It is not clear that this proves time had a beginning. Other physicists, such as Lawrence Krauss, author of A Universe from Nothing (2012), and I, author of Unraveling the Universe’s Mysteries (2012), argue events occurred that preceded and caused the big bang, which implies time preceded the big bang. It does not prove, though, that time has an infinite past or a beginning.

Almost all of us believe we understand time. In fact, when first asked a question about the nature of time, most of us will begin to explain it. However, as we attempt to explain it, the complexity of time’s nature emerges. Augustine of Hippo (354 CE–430 CE), known to Christians as St. Augustine, eloquently made this observation: “What then is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not.” The most difficult thing I encountered regarding the nature of time was trying to explain it to my six-year-old grandchild. That is when Einstein’s famous quote hit home: “If you can’t explain it to a six-year-old, you don’t understand it yourself.”

Fortunately, though, as the sands of time counted millennia after millennia, three major philosophical schools on the nature of time emerged. We will examine them and discuss their implications regarding time travel in our next post.

Close-up of a large clock face with Roman numerals illuminated by warm golden light.

The Science of Time – Part 1/3

Categories, Time Travel, , , , ,

The Science of Time: This is taken from appendix 5 of my new book, How to Time Travel, which will be available on Amazon in early September 2013.

From a practical standpoint, the science of time started with Isaac Newton in the seventeenth century, but underwent dramatic changes early in the twentieth century, when a little-known patent examiner published a paper in the Annalen der Physik in 1905. The paper contained no references, quoted no authority, and had relatively little in the way of mathematical formulation. The writing style was unconventional for a scientific paper, relying on thought experiments combined with verbal commentary. No one suspected that the world of science was about to be changed forever. The little-known patent examiner was twenty-six-year-old Albert Einstein. The paper was on the special theory of relativity, which quietly led to the scientific unification of space and time, and the scientific realization that mass is equivalent to energy. The ink of this one paper rewrote the science of time. However, we are getting a little bit ahead of ourselves. Let us go back and start with Isaac Newton.

The English physicist Isaac Newton (1642–1727) was the greatest and most famous scientist of his time, and with good reason. He is widely credited with playing a key role in the scientific revolution, hailed as the beginning of modern science. His most important work, the publication of Philosophiæ Naturalis Principia Mathematica, Latin for Mathematical Principles of Natural Philosophy, in 1687 set forth his famous three laws of motion (the foundation of Newtonian mechanics), along with his theory of gravity (Newton’s law of gravity). Newtonian mechanics and Newton’s law of gravity are still taught in high school and college science classes. Newton also contributed to optics and shared the invention (along with Gottfried Leibniz) of calculus, a critical branch of mathematics used in advanced science to this day.

Let us ask the key question: How did Newton scientifically view time? Newton thought of time as an absolute. He believed that time passed uniformly, even in the absence of change. Newton’s thoughts about the science of time would go something like this: The world is changing at varying rates, but time passes uniformly. The world stops changing completely, but time passes uniformly. Any event that occurs at a single point in time occurs simultaneously for all observers, regardless of their position or relative motion. Newton’s view of time as an absolute became a cornerstone of classical physics and prevailed until the early part of the twentieth century. In our everyday world, this view of time makes complete sense. Newton’s science of time only breaks down when observers are at vastly different distances from an event, or when the event or the observers are moving near the speed of light relative to one another. Obviously, this did not occur in the real-world situations of Newton’s era. In addition, the speed of light was not a consideration in Newtonian mechanics. Remarkably, Newtonian mechanics is still a highly successful theory for predicting and explaining typical real-world phenomena.

This next part of the story may surprise you. Newton is widely viewed as one of the most influential scientists of all time. His scientific accomplishments and writings make a strong case that his view of time as an absolute was his original work. However, this is probably not entirely true. The concept of time being an absolute actually started with Galileo.

Galileo was a brilliant Italian physicist, mathematician, astronomer, and philosopher. Galileo and Newton never met in person, since Galileo died the same year Newton was born, 1642. However, Galileo’s scientific writings not only played a role in the scientific revolution, but it is likely Galileo played a major role in shaping Newton’s thinking. In fact, the coordinate transformation methodology that treats time as an absolute is termed the Galilean transformation. Let us understand how this came about.

Time is an absolute (Galilean transformation)

There appears little doubt that Newton’s science of time was significantly influenced by Galileo’s 1638 Discorsi e Dimostrazioni Matematiche (Discussions on Uniform Motion), since Newton’s and Galileo’s views of time are essentially identical. For example, the transformation of the time coordinate from one frame of reference to another, regardless of the relative motion of either frame, left the time coordinate unchanged. As mentioned above, this type of coordinate transformation is termed the Galilean transformation, and it works as long as the frames of reference move at low velocities. This begs a question. What happens as the frames of reference move at velocities close to the speed of light? To address this question, we need to discuss the Lorenz transformation. Stay tuned for The Science of Time – Part 2/3.