Category Archives: Time Travel

A silhouette of a person with a clock face behind them, symbolizing the concept of time and human existence.

Theoretical Foundations for Time Travel (Why time travel is possible!)

Categories, Physics, Time Travel, , , , , , , ,

This post is based on material from chapter 1 of my new book, How to Time Travel.

Einstein’s special and general theories of relativity underpin the science of time travel. They are briefly presented here as theoretical evidence that time travel is real. In addition, Del Monte’s existence equation conjecture is presented as theoretical evidence that time travel is real.

1. Einstein’s special theory of relativity—The scientific community considers the special theory of relativity the “gold standard” of scientific theories. It has withstood over one hundred years of experimental verification. In addition to yielding the most iconic scientific equation of all time, E = mc2, it also gave us our first insight into the scientific nature of time and predicted time dilation, both conceptually and mathematically. Time dilation is the experimentally verifiable difference of elapsed time between two events as measured by observers, when either one or both observers are moving relative to each other at a velocity near the speed of light. It is an experimental fact that the second hand on a clock moving at a velocity close to the speed of light moves slower than a clock at rest. Time dilation is real and implies forward time travel. For example, if you board a spacecraft capable of traveling at 650 million miles per hour, a one-day journey measured by a clock onboard the spacecraft would be equivalent to the passage of one year on Earth. Time dilation experiments are routinely performed using particle accelerators, which we will discuss later in this chapter.

2. Einstein’s general theory of relativity—Numerous aspects of the general theory of relativity have been verified. For our purposes regarding time travel, it is important to focus on only two:

* Gravitational time dilation—Gravitational time dilation suggests that two observers differently situated from gravitational masses will observe time differently. For example, a clock closer to the Earth will run slower than a clock farther from the Earth. The stronger the gravitational field, the greater the time dilation. This has been experimentally verified using atomic clocks, and we will discuss the results later in this chapter.

* Closed timelike curves—There are numerous solutions to Einstein’s equations of general relativity that delineate the world line of a particle is closed, returning to its starting point. In the general theory of relativity, the world line is the path the particle traverses in four-dimensional spacetime. For example, when the particle starts out, it has four coordinates, three dimensional coordinates and one temporal coordinate. Here is a simple analogy. You are in a specific place, definable by three spatial coordinates, reading this book at a specific time, a temporal coordinate. If the world line of a particle returns to its starting point, the particle is said to have returned to its past, suggesting backward time travel is theoretically possible. However, to date, we have not been able to experimentally verify that this aspect of Einstein’s general theory of relativity is true. As previously discussed, there is evidence that the “arrow of time” can be twisted, and that events in the future can influence past events. However, this is not conclusive experimental proof that backward time travel is possible.

3. Del Monte’s existence equation conjecture—In summary, the existence equation conjecture is derived from Einstein’s special theory of relativity and predicts that a mass requires energy to move in time. If additional positive energy is added to the mass, for example, by accelerating it in a particle accelerator and increasing its kinetic energy, the mass will move more slowly in time. I interpret this as the fundamental explanation of time dilation. An interesting aspect of the existence equation conjecture is that it suggests adding negative energy to a mass will cause the mass to move backward in time. Since today’s science has been unable to produce and manipulate negative energy, this last point has not been experimentally verified. (Note: An entire chapter is devoted to explaining the existence equation conjecture in the referenced source, How to Time Travel)

Source: From chapter 1 of How to Time Travel: Explore the Science, Paradoxes, and Evidence (September 2013), Louis A. Del Monte (Amazon)

Image: Book Cover How to Time Travel

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

The Time Uncertainty Interval – The theoretical limit to measuring time

Categories, Time Travel, , ,

This post is based on material from my new book, How to Time Travel, available on Amazon.com.

All attempts in science to define time fail. Instead, we describe how time behaves during an interval, a change in time. We are unable to point to an entity and say “that is time.” The reason for this is that time is not a single entity, but scientifically an interval. We cannot slice time down to a shadow-like sliver, a dimensionless interval. In fact, scientifically speaking, the smallest interval of time that science can theoretically define, based on the fundamental invariant aspects of the universe, is Planck time.

Planck time is the smallest interval of time that science is able to define. The theoretical formulation of Planck time comes from dimensional analysis, which studies units of measurement, physical constants, and the relationship between units of measurement and physical constants. In simpler terms, one Planck interval is approximately equal to 10-44 seconds (i.e., 1 divided by 1 with 44 zeros after it). As far as the science community is concerned, there is a consensus that we would not be able to measure anything smaller than a Planck interval. In fact, the smallest interval science is able to measure as of this writing is trillions of times larger than a Planck interval. It is also widely believed that we would not be able to measure a change smaller than a Planck interval. From this standpoint, we can assert that time is only reducible to an interval, not a dimensionless sliver, and that interval is the Planck interval. Therefore, our scientific definition of time forces us to acknowledge that time is only definable as an interval, the Planck interval.

Since the smallest unit of time is only definable as the Planck interval, this suggests there is a fundamental limit to our ability to measure an event in absolute terms. This fundamental limit to measure an event in absolute terms is independent of the measurement technology. The error in measuring the start or end of any event will always be at least one Planck interval. This is analogous to the Heisenberg uncertainty principle, which states it is impossible to know the position and momentum of a particle, such as an electron, simultaneously. Based on fundamental theoretical considerations, the scientific community widely agrees that the Planck interval is the smallest measure of time possible. Therefore, any event that occurs cannot be measured to occur less than one Planck interval. This means the amount of uncertainty regarding the start or completion of an event is only knowable to one Planck interval. In our everyday life, our movements consist of a sequence of Planck intervals. We do not perceive this because the intervals are so small that the movement appears continuous, much like watching a movie where the projector is projecting each frame at the rate of approximately sixteen frames per second. Although each frame is actually a still picture of one element of a moving scene, the projection of each frame at the rate of sixteen frames per second gives the appearance of continuous motion. I term this inability to measure an event in absolute terms “the time uncertainty interval.”

Please feel free to browse How to Time Travel.

A silhouette of a person with a blank face in front of a large clock, set against a swirling cosmic background.

How to Time Travel: Explore the Science, Paradoxes, and Evidence

Categories, Time Travel, , , , , , , ,

Here is the entire introduction from my new book, How to Time Travel. Enjoy!

Introduction

Few subjects evoke more emotion than time travel, the concept of moving between different points in time in a manner analogous to moving between different points in space. Humankind’s fascination with time travel dates back thousands of years. Although there is no consensus recognizing which written work was the first to discuss time travel, many scholars argue that the Mahabharata, from Hindu mythology, is the first, dating between 700 BCE (Before the Common/Current/Christian Era) and 300 CE (Common/Current/Christian Era). The Mahabharata, which is one of the two major Sanskrit epics of ancient India, relates the story of King Revaita, who travels to heaven to meet the deity Brahma. When King Revaita returns to Earth, he is shocked to learn that many ages have passed. In today’s science, we would assert King Revaita experienced time dilation.

What is time dilation? It is a scientific fact that time moves slower for any mass accelerated near the speed of light. If that mass were a clock, for example, the hands of the clock would appear to be moving slower than a clock in the hand of an observer at rest. That phenomenon is termed time dilation. If King Revaita used a spaceship capable of speeds near the speed of light to visit Brahma, a roundtrip journey that would appear to King Revaita to take one year would result in a time passage of thirty years on Earth. This may seem like science fiction, but time dilation is a well-established, experimentally verified aspect of Einstein’s special theory of relativity; more about this later.

Arguably, the greatest single written work that laid the foundation to fire the imagination of today’s generation regarding time travel is H. G. Wells’s classic novel, The Time Machine, published in 1895. It has inspired numerous popular movies, television programs, novels, and short stories. Why are we humans so obsessed with time travel? It appears to be an innate longing. How many times have you wished that you could go back to a specific point in time and select a different action? We all do it. Consider the number of times you have replayed a specific situation in your mind. Psychologists tell us we replay an event in our minds when the outcome is not finished to our satisfaction. This has accounted for numerous nights of tossing and turning. Another common need is to seek answers to important questions from a firsthand perspective. Perhaps you would like to be a witness during the resurrection of Christ, or be a witness behind the grassy knoll during the Kennedy assassination. Perhaps you miss a loved one who has passed on, and you would like to go back in time to embrace that loved one again.

Some of us also dream about time travel to the future. What outcomes will result from our decisions? Imagine the prosperity and happiness that could be ours if we were able to travel to the future. We would be able to witness the outcome of any decision, return to the present, and guide our lives accordingly. Picking the right profession or choosing the right mate would be a certainty. We could ensure there would be no missteps in our life. A life of leisure and prosperity would be ours for the taking.

It is little wonder that many people ask this deceptively simple question: Is time travel possible? The majority of the scientific community, including myself, says a resounding yes. The theoretical foundation for time travel, based on the solutions to Einstein’s equations of relativity, is widely accepted by the scientific community. The next question, which is the most popular question, is how to time travel. Of all the questions in science, the keyword phrase “how to time travel” is close to the top of Internet search engine searches. According to Google, the largest search engine in the world, there are 2,240,000 worldwide monthly searches for the keyword phrase “how to time travel,” as of this writing. Unfortunately, it is the most difficult question to answer.

Obviously, interest in time travel is high, and what people want to know most is how to time travel. This high interest, combined with the intriguing real science behind time travel, is what inspired me to write this book.

At this point, I would like to set your expectations. We are going to embark on a marvelous journey. We will examine the real science of time travel, the theoretical foundation that has most of the scientific community united that time travel is possible. We will also examine the obstacles to time travel, and there are many. However, even in the face of all the obstacles, most of the scientific community agrees it is theoretically possible to time travel. The largest issue in time travel is not the theoretical science. It is the engineering. Highly trained theoretical physicists understand the theoretical science of time travel. However, taking the theory and building a time machine capable of human time travel has proved a formidable engineering task. It has not been done, but we are amazingly close. We have already built time machines capable of sending subatomic particles into the future. If you will pardon the pun, it is just a matter of time before we engineer our way through the time travel barrier and enable human time travel.

In setting your expectations, I promise you significant insight into the real science of time travel and an equally incredible insight into the obstacles to time travel. I cannot promise that with this knowledge you will be able to overcome the obstacles and engineer how to time travel. However, you may be the one person destined to harness the science, glean the engineering simplicity, and journey in time. There is only one way to find out, namely, read on.

To browse the book free on Amazon, click this link: https://amzn.to/1dWyEkp

science of time & time dilation

The Philosophy of Time and Time Travel – Part 2/2 (Conclusion)

Categories, Time Travel, , , , ,

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

Let us examine the three major philosophical schools on the nature of time and their implications regarding time travel.

1. Presentism theory of time

The presentism theory of time holds that only the present is real. The past is over. Therefore, it is no longer real. The future has yet to occur. Therefore, the future is not real. Presentists argue that our mind remembers a past and anticipates a future, but neither is real. They are mental constructs.

Arguably, the most famous presentist is Augustine of Hippo (a.k.a. St. Augustine), who compared time to a knife edge. The present represents a knife edge cutting between the past and future. Ironically, this means Augustine of Hippo is not real, since he lived and died in the past. Therefore, should we study Augustine of Hippo, who, by his own philosophy, is not real? Of course, I am only being contentious to make a point.

Presentism has a large following, especially among Buddhists. Fyodor Shcherbatskoy (1866–1942), often referred to as the foremost Western authority on Buddhist philosophy, summed up the Buddhist view of presentism with these few words: “Everything past is unreal, everything future is unreal, everything imagined, absent, mental…is unreal…Ultimately real is only the present moment of physical efficiency.” Uncountable millions of Buddhists still ascribe to this view of time and reality.

A cogent philosophical argument can be made for presentism, but presentism is problematic from a scientific viewpoint. When we discussed the special theory of relativity, we learned that the present is a function of the position and speed of the observer. Therefore, what is the present to one observer may be the past to another.

From the standpoint of time travel, presentism renders the question “how to time travel” moot. If we embrace presentism, there is no past or future, and time travel is meaningless. Fortunately, though, other philosophies of time open the door to time travel. Let us examine the next one.

2. Growing universe theory of time

This theory of time is also referred to as “growing block universe” and “the growing block view.” However, regardless of the name, they all hold the same philosophy of time. The past is real, and the present is real. The future is not real. The logic goes something like this: The past is real because it actually happened. We experience it, and we document it. We call it history. The present is real because we experience it. We often share the present with others. The future is not real because it has not occurred.

Why do all the names for this theory of time start with the word “growing”? The concept is that the passage of time continually expands the history of the universe. Actually, this is logical. The history of the world, and the universe, continues to expand with the passage of time. The history section of any library is destined to grow with time.

In this philosophy of time, only time travel to the past makes sense, since for growing-universe philosophers, the past is real. We cannot time travel to the future, since the future has yet to occur. Therefore, it is not real.

As logical as this theory of time may appear, there is scientific evidence that the future is real and can influence the present. We discussed this evidence in the section titled “Twisting the arrow of time” in chapter 1. Now, let us examine the last significant philosophy of time.

3. Eternalism theory of time

The eternalism theory of time holds that the past, present, and future are real. The philosophy of this theory rests on Einstein’s special theory of relativity. Essentially, the special theory of relativity holds that the past, present, and future are functions of the speed and position of an observer.

While Einstein never equated time with the fourth dimension, Minkowski’s geometric interpretation of Einstein’s special theory of relativity gave birth to four-dimensional space, with time as part of the fourth dimension. In Minkowski’s interpretation, often termed “Minkowski space” or “Minkowski spacetime,” the fourth dimension includes time and is on equal footing with the normal three-dimensional space we currently encounter. However, Minkowski’s fourth dimension borders on the strange. In Minkowski spacetime, the fourth dimension, X4, is equal to ict, where i = √-1, an imaginary number, c is the speed of light in a vacuum, and t is time as measured by clocks. The mathematical expression ict is dimensionally correct, meaning that it is a spatial coordinate, not a temporal coordinate, but is essentially impossible to visualize, since it includes an imaginary number. What is an imaginary number? It is a number that when squared (multiplied by itself) gives a negative number. This is not possible to do with real numbers. If you multiply any real number, even a negative real number like minus one, by itself, you always get a positive number. Therefore, it is impossible to solve for the square root of minus one.

Although we can express it mathematically as √-1, it has no solution, and it is termed an imaginary number. Does that mean Minkowski was wrong about the fourth dimension? Actually, it does not. It does say that it is a mathematical construct, and intuitively, for most of us, impossible to visualize. However, the special theory of relativity continues to be taught using Minkowski spacetime, which the bulk of the scientific community considers a valid geometric interpretation. In either its algebraic form, as first presented by Einstein, or its geometric form, as interpreted by Minkowski, the majority of the scientific community considers the special theory of relativity the single most successful theory in science. It has withstood over a century of experimental investigation, and it is widely considered verified.

Because of its scientific underpinnings, the eternalism theory of time is widely accepted in the scientific community. If we adopt the eternalism theory of time, then time travel to the past or future becomes equally valid. In addition, no scientific theory contradicts or prohibits time travel. Said more positively, based on Einstein’s theories of relativity, which lay a theoretical foundation for time dilation (i.e., time travel to the future) and closed timelike curves (i.e., time travel to the past), most of the scientific community would support the scientific possibility of time travel.

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.