Tag Archives: What-Time

How Fast Does Time Flow?

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Part of the What Time? series, an exploration in science fiction.

Let’s assume time flows in one direction from past towards future. One common analogy is a river carrying the observer from birth to death. Events of life pass from future into the present before departing into the past. The river may seem to flow fast or slow, but we measure the passing of time with the constant beat of a clock. This is the popular view of time in western cultures.

If time flows then how fast does time flow?

Trying to answer the question with “one second per second” presents the problem. We can’t measure something relative to itself. If time flows (or moves) then what is time flowing relative to? What is the bank to the river of time?

Perhaps time doesn’t flow at all and it is the observer moving. What pulls the observer? How fast? This is the same analogy flipped, and doesn’t bring us any closer to answering the question.

In this view of time we divide time into parts: future, present, and past. Future events are undetermined, but predictable given enough information. The past is determined, fixed in place assuming our memories are accurate. Even if the river analogy isn’t a very good one, we are still faced with the question: how fast do these future events arrive? What sort of experiment could we perform that measures time or even shows that time moves at all?

A Logic Problem

Let’s try another approach. Divide time into two segments: the future and the past divided by a line of the present. Choose three events from our observer’s life: college graduation, tenth birthday party, and wedding day. We may mark these events by season, celestial position, or calendar dates. We may find the time of day the bride and groom, holding knife hand-in-hand, slice into the wedding cake. Each event resides at specific places corresponding with other events and never move, assuming we have perfect memory. Given the present resides within the observer’s fifteenth year then wedding day and college graduation are in the future while tenth birthday party is in the past. With the present at age forty-six all three events are in the past.

If past and future are physical parts of space-time then how can these events exist in two places? How can wedding day be in the future and the past. The events never move. They are always in the same position relative to everything else. How do we decide wedding day is in the future and change our minds placing it in the past? What changed? Time, you say?

At any event we always have the same sensation of time flowing. The difference is our memories. Time never changes. Our memories change.

As outside, independent observers how would we label the events? Without being given the “present” we cannot label the events. Since events cannot exist in two places, we cannot place events into future or past.

Does time flow at all?

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What Time? series posts on the 2nd and 4th Tuesday of the month.

Time Travel Movies

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Part of the What Time? series, an exploration in science fiction.

Here in no particular order are some of my favorite time travel (or time related) movies. We will come back to a few of these as we explore time. Video trailers belong to their respective owners.

The Time Machine (1960)

Before Einstein’s famous paper, the H.G. Well’s story shows us that time is relative to the observer.

Back to the Future

Small changes in the past translate into serious alterations in the future.

Bill and Ted’s Excellent Adventure

The fun part of this film is the solving of problems by remembering to travel back in time later to supply the aid.

The Butterfly Effect

The main character travels back to his younger self making small changes altering his present in unintended ways.

Terminator 2: Judgment Day

“There is no fate,” the future and past are changeable.

Star Trek IV: The Voyage Home

Traveling into the future is easy, just go fast. Here, the crew finds a way to travel into the past.

12 Monkeys (1995)

Fate locks the past and future. Do the past or future exist?

What are your favorite time travel or time bending movies?

Twins Paradox

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Part of the What Time? series, an exploration in science fiction.

The Twins Paradox is less of a paradox and more of a time puzzle originally stated by Einstein.

Puzzling Twins

Alice and Angela are identical twins born seconds apart on a shiny afternoon. Growing up, they do everything together including dressing alike. Their mother insists they wear different colored bows in their hair, Alice in a red bow and Angela in pink. Teachers and some of their friends depend on the bows for identification, but their closest friends can tell them apart most of the time. Sometimes they like switching bows and pretending to be the other, especially when taking exams. Angela is the whiz at math.

At the age of seventeen years, Angela announces she intends on traveling to nearby Barnard’s Star as part of her astronomy studies. The university has limited room and cannot include another member on the field trip spanning several years. Although the ship can accelerate to near the speed of light, it must spend several years at the constant velocity before decelerating at the destination where the team will spend two years observing. Alice argues that it would tear them apart taking such a long trip. How could they live without each other? Alice tries and tries, but Angela has made up her mind. Alice waves goodbye to her sister and watches the craft depart the space station.

Thirty-nine years later, red bow long lost, Alice takes her two grown children to meet her sister at the space station. Angela steps off the spacecraft wearing the pink bow in her hair. Angela appears younger than Alice’s own children. Angela insists she has only been away for twelve years, not thirty-nine, and she argues with her much older twin.

What happened?

Short Answer

Angela’s trip experiences a time-dilation effect. From my “Quick, Dirty Relativity Review,” we know that time is relative to the observer verified using highly accurate clocks. One consequence is that observers moving at significantly different rates will appear to age differently. Both twins age normally and experience the normal passing of time. Since both twins move at significantly different rates, their frames of time relative to each other differ. Time is relative to the observer.

If motion is relative than why isn’t the time-dilation effect relative?

The Paradox

From Alice’s frame of reference, Angela is moving and her time appears slowed by time dilation. From Angela’s frame of reference, Alice is the one moving. (Recall that a reference frame tells us that science experiments gives the same results in uniform motion as if we were sitting still. This doesn’t apply to accelerating objects.) Why isn’t time-dilation effect relative? The answer is the accelerating part of the trip. Einstein brought up this twins puzzle pointing out it isn’t really a paradox. Acceleration isn’t relative.

Math

Assuming the space craft can accelerate without squishing the passengers to death, let’s try using numbers to see how this works. Angela spent three years at Barnard’s Star, the same in Alice’s reference since Barnard’s Star system and Earth are nearly relative to each other in motion. Travel time for Angela is nine years (four and half each way) while the trip from Alice’s reference is thirty-six years (thirty-nine minus three.) Disregarding time for acceleration, we can use the following formula to find out how fast Angela’s ship travels where td is time dilation and v/c is percentage speed of light:

The time dilation (td) from Angela to Alice is 9 / 36 or 0.25. This gives us a velocity of 0.9825% speed of light. Mighty fast! Getting up to that speed safely would actually take a long time without some kind of anti-squishing technology!

Quick, Dirty Relativity Review

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Part of the What Time? series, an exploration in science fiction.

Relativity

Size is relative. Speed is relative. In my story, “Dunston Monster,” some of the characters refer to Sebastian as a giant while others just think he’s very big. Comparing to a tree, Sebastian is short. Scientist measure everything relative to something. A car travels 70 km in an hour (70 km/h or average 1200 m/s.)

Relative Measurement

  • Distance measured relative to a standard such as a meter (m.)
  • Velocity measured relative to distance per time standard: m/s.
  • Acceleration measured relative to m/s/s or m/s2

A train travels 40 km/h and Jason walks in the aisle towards the front of the train. Of course, we assume the train travels 40 km/h relative to the ground. If Jason walks at 4 km/h relative to the train, then Jason moves at 44 km/h relative to the ground. Simple, right?

Theory of Relativity

Actually, two theories, Special and General. We will deal with the Special Theory of Relativity by Einstein which generalizes Galileo’s relativity principal stating that the laws of physics are the same in all inertial frames of reference.

Brief History Lesson

Scientists wanted to know how fast light travels. The problem: relative to what? Earth zips around the sun, and the sun speeds through the universe. Someone suggested a solution: measure light from a star in the same direction as Earth travels then in the opposing direction. Much like Jason on the train, some arithmetic should leave us the answer of light traveling relative to some “ether.”

It didn’t work out. In every direction scientists measured the same velocity of light coming from distant stars. Scientists scratched their heads.

Einstein suggested a logical conclusion: time is relative to the observer. No matter how the observer travels, the observer will always measure the same speed of light.

Proof of Time Relativity

Using atomic clocks, scientists have compared measurements between an observer on the ground and an observer traveling around the globe on the airplane. The clocks disagreed. The larger the difference in motion, the more the clocks disagree.

Time is Relative

Space-Time Light Cone

In our exploration of time, we should keep this mind. Time is relative to the observer. Standing on Earth, we may safely assume our observations are the same. Even traveling in airplanes, the differences are so tiny that we’ll never notice. Traveling in spaceships is a different story.

Now we may interpret time as a 4th dimension to our spatial dimensions. Since imagining four dimensions is a challenge, we can draw a diagram using only one of the spatial dimensions on one access and time on the other. Apply it to the other two spatial dimensions. We end up with a light cone defining future, past, and elsewhere.

We can’t reach elsewhere using normal traveling means. Why? The Theory of Relativity gives us the equation, E = mc2 where E is energy, m is mass, and c is the speed of light. The problem is accelerating mass to the speed of light requires infinite energy. Our future travelers will need to find another way to reach elsewhere, or be patient and reach

Light Cone for Mars and Earth

the same spatial location inside the future cone.

What happens now? Let’s say a robot on Mars breaks and sends a distress signal. Now for the robot is different than now for the observers on Earth. Seen in the diagram, the observers on Earth don’t find out about the problem until 20 minutes later relative to the robot. The present is relative.

Fun Time Facts

  • Light from the sun takes about 8 minutes to reach Earth.
  • Light from the next closest star takes 4 years.
  • Chatting with an astronaut in Saturn orbit requires over 2 hours to hear the reply.

Considerations in Sci-Fi Writing

  • Can’t describe spaceship accelerating beyond light speed.
  • Faster than light (FTL) travel is impossible for mass. Find other way.
  • What would warp-speed (or sub-warp) look like?
  • Traveler in other star system can’t use the radio to communicate with Earth.

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What Time? series posts every 2nd and 4th Tuesday of the month.

Newtonian Time

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Part of the What Time? series, an exploration in science fiction.

Let us generalize a moment.

The Background

In the 17th century industrialization sprouted leading to 19th century railroad domination linking commerce across the map. Scheduling trains increased the need for time zones. Higher precision clocks allowed ships improved navigation across the sea. Clocks became important including today as we schedule our every minute.

Before the machinery took over, physicist Isaac Newton introduced the Laws of Motion. According to our science definitions, “laws” explain observations without understanding why. Every action has an equal and opposite reaction. An object in motion stays in motion until an outside force acts upon it. The Law of Gravity predicted planetary positions and falling objects. These beautiful laws allowed us to build wonderful things. It also gave us a sense of precision and logic.

The Stage

Newtonian physics (classical,) became common sense. (Not for everyone, some students still get confused.) Newton’s math and physics allows us to predict the future, where a cannon ball will land, planetary positions, or the moon phase on a given date. Recording the past to help predict the future entrenched us in the idea that the past is set and the future is uncertain, but predictable with enough data (from the past.) Law-like principles ruled.

With increased precision, more trains, clocks ticking away in (near) synchronous, the drum beat of time hardened “common sense” time into our lives.

Tick-tock, tick-tock.

“Common Sense” Time

I call this, Newtonian Time. It isn’t Newton’s fault. I don’t blame him. For Westerners, the roots of “common sense” time was already there. I call it Newtonian Time because it fits with Newtonian Physics, or classical physics.

Time is an assumption, and in this perception, time passes at a constant beat.

Tick-tock, tick-tock, tick-tock.

All of classical physics depends on this constant beat along with the assumption that the past is unchangeable and the future is predictable. This leads to the impression of time’s arrow. We feel pulled down the river of our lives unable to escape the flow or stop the beating drum, like our hearts, pounding away until the end.

Under this perception of time we assume time is the same for everyone.

Even in Newton’s day, scientists noticed problems. One glaring puzzle keeping astronomers curious for years: the planet Mercury refused prediction under classical physics. That is another story: Relativity.

Learn More

  • About Time by Paul Davies, “Chapter 1: A Very Brief History of Time”
What Time? series posts on 2nd and 4th Tuesday of the month.

What Time? Series Introduction

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Time is the great assumption in science, a mystery. There is no scientific definition or accepted theory. Time has been the subject of philosophical debate for millennia, and all we have are vague notions, psychological feelings, stories, and an assumption about the passing seconds. And time is so much fun for fiction.

What is time?

This series will explore the science of time in fiction including the Draco Torre stories and popular titles. The purpose is not to master physics, but to explore concepts within science fiction. Posts will be reasonably basic and include references to more detailed sources. Some of the topics we will explore:

  • paradoxes
  • time experiments
  • time travel
  • memory
  • perceptions of time
  • novels

Your comments are welcome in each discussion including sharing your favorite novels, topic requests, and thoughts on the current topic.

Contents

What Time? series is on a break until Fall 2010.

2010 Preview

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Flash Stories

Frequency of #fridayflash posts will depend on time and feedback. Flash fiction is not my strongest area. If readers enjoy them, I’ll post more. Otherwise expect fewer flash stories while I concentrate on other topics. To start the year, the young Sebastian Rhemus will continue his adventure in a short serial. Tags: Flash Fiction, Sebastian Rhemus, Story Category: Stories

My first novel

I’ve been sitting on a completed novel, Raven Memory, for some time now deciding what to do with it. I want to release it on my time and terms. Future posts will include art, video, and sample chapters. Sometime in the next year I will release Raven Memory to the world. Tags: Raven Memory, Draco Torre Category: Novels

What Time? Series

Appearing on 2nd and 4th Tuesday of each month, this series takes a look at the science of time and relation to my novels. We will explore perceptions of time, memory, time travel, paradoxes, and other mysteries. Each post will keep the science basic providing references to more extensive information. Tags: What-Time, science Category: Science

The Usual

Other posts about reading and writing will continue. With all kinds of new reading devices, there should be plenty to discuss for the next few years. New technology allows new forms of storytelling. I’m very interesting in seeing what develops.

Feel free to join the discussion at any time including older posts.