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ScienceDaily (Apr. 15, 2005) — The concept of time is self-evident. An hour consists of a certain number of
minutes, a day of hours and a year of days. But we rarely think about the fundamental nature of time.
Time is passing non-stop, and we follow it with clocks and calendars. Yet we cannot study it with a microscope
or experiment with it. And it still keeps passing. We just cannot say what exactly happens when time passes.
Time is represented through change, such as the circular motion of the moon around the earth. The passing of
time is indeed closely connected to the concept of space.
According to the general theory of relativity, space, or the universe, emerged in the Big Bang some 13.7 billion
years ago. Before that, all matter was packed into an extremely tiny dot. That dot also contained the matter
that later came to be the sun, the earth and the moon – the heavenly bodies that tell us about the passing of
time.
Before the Big Bang, there was no space or time.
“In the theory of relativity, the concept of time begins with the Big Bang the same way as parallels of latitude
begin at the North Pole. You cannot go further north than the North Pole,” says ​Kari Enqvist​, Professor of
Cosmology.
One of the most peculiar qualities of time is the fact that it is measured by motion and it also becomes evident
through motion.
According to the general theory of relativity, the development of space may result in the collapse of the
universe. All matter would shrink into a tiny dot again, which would end the concept of time as we know it.
“Latest observations, however, do not support the idea of collapse, rather inter-galactic distances grow at a
rapid pace,” Enqvist says.
If you want to know more about the topic, visit Kari Enqvist’s website at ​http://www.physics.helsinki.fi/~enqvist/​.
Adapted from materials provided by ​University of Helsinki​.
QUESTIONS:
1.
2.
What are three ways that time is defined in this reading?
How are space and time related?
What is Time?
by ​Anders Cullhed
28 August 2001
Time is one of the main problems of Western philosophy and literature. Ever since the thinkers of classical
Greece tried to understand the swiftness of our seconds, minutes and hours, the problem of time has haunted
our imagination. It is even more than a problem, it is a mystery.
"What is time? It is a secret - lacking in substance and yet almighty." Those are the words of the German Nobel
Prize winner in Literature, ​Thomas Mann​, in his great novel ​The Magic Mountain​ (1924). Mann was a very
modern writer, and yet his definition of time was more or less the same as the one provided by the Roman
Church Father Saint Augustine in his famous autobiography, ​Confessions,​ more than fifteen hundred years
earlier:
What, then, is time? I know well enough what it is, provided that nobody asks me;
but if I am asked what it is and try to explain, I am baffled.
In ancient Greece, people generally conceived of time as a circle. Hesiod, the famous Greek historian from the
8th century B.C., described five ages of mankind, beginning with the golden age in a remote past, where
human beings lived in peace with each other and in harmony with nature, down to the miserable contemporary
age of iron, characterized by dispute and warfare.
Two hundred years later, the Pre-Socratic philosopher Pythagoras depicted history as one Great Year (in
Latin: Magnus Annus). When such a world historical cycle came to an end, the sun, the moon and all other
planets would return to their original positions. Exactly the same people would return to earth, all that had
happened would happen once again. These so called eternal recurrences (the same things happening over
and over again) have been of great interest to modern writers, such as the German philosopher Friedrich
Nietzsche (pronounced Knee-che), and they have inspired the Irish Nobel Prize winner in Literature, ​William
Butler Yeats​, to some of his great poems: the old city of Troy, famous from Homer’s ​Iliad,​ will burn once again,
and Jason, the mythical hero, will board his ship Argo once again, in quest of the golden fleece:
And then did all the Muses sing
Of Magnus Annus at the spring,
As though God’s death were but a play.
Another Troy must rise and set,
Another lineage feed the crow,
Another Argo’s painted prow (front of a ship)
Drive to a flashier bauble (ornament) yet.
Cyclical and Mythical
The concept of cyclical time, though, reaches far beyond ancient Greece. It is quite common in the
Pre-Columbian civilizations of South and Central America, where it appears in the old Indian cultures of the
Maya and Aztec peoples. The Aztecs made use of a calendar carved in a huge circular stone, the Sun stone,
which nowadays is one of the main attractions of the Anthropological Museum in Mexico City.
Irreversible Process
Nevertheless, throughout medieval and modern Western history time has generally been presented not as a
circle but as a line or, more exactly, an irreversible process with a unique beginning (birth) and a unique end
(death). It is probably Saint Augustine, more than anyone else, who is responsible for this enormously
influential concept of time.
Nevertheless, the very same idea could be updated by the philosophers of the Enlightenment in the 18th
century, who created our modern, non-religious version of time. From now on, time is generally conceived of
as an endless process, without beginning and without end, a neutral course of events, theoretically released
from its old connections with the planets and the seasons of the year, possible to cut up into an infinite number
fractions (years, months, days, seconds, nanoseconds, etc.). This scientific idea of time depends on the
breakthrough of mechanical watches during the early modern period. Even more importantly: writers,
philosophers and scientists have long been able to reconcile it with another great modern idea, that of
progress.
QUESTIONS:
1.
2.
3.
4.
How did Thomas Mann define time? What about St. Augustine?
People in ancient Greece saw time as circular (a circle). What did they mean by this?
What did Pythagoras mean by “Magnus Annus”?
How does the modern version of time differ from the ancient Greeks and the pre-Columbian civilizations
of Central and South America?
A Quest to Save His Father
Ronald Mallett, Professor at the University of Connecticut, has used
Einstein’s equations to design a time machine with circulating laser beams.
While his team is still looking for funding, he hopes to build and test the
device in the next 10 years.
With a brilliant idea and equations based on Einstein’s relativity theories,
Ronald Mallett from the University of Connecticut has devised an experiment
to observe a time traveling neutron in a circulating light beam. While his team
still needs funding for the project, Mallett calculates that the possibility of time
travel using this method could be verified within a decade.
Black holes, wormholes, and cosmic strings – each of these phenomena has
been proposed as a method for time travel, but none seem feasible, for (at
least) one major reason. Although theoretically they could distort space-time,
they all require an unthinkably gigantic amount of mass.
Mallett, a U Conn Physics Professor for 30 years, considered an alternative
to these time travel methods based on Einstein’s famous relativity equation: E=mc​2​.
“Einstein showed that mass and energy are the same thing,” said Mallett, who published his first research on
time travel in 2000 in ​Physics Letters​. “The time machine we’ve designed uses light in the form of circulating
lasers to warp or loop time instead of using massive objects.”
To determine if time loops exist, Mallett is designing a desktop-sized device that will test his time-warping
theory. By arranging mirrors, Mallett can make a circulating light beam which should warp surrounding space.
Because some subatomic particles have extremely short lifetimes, Mallett hopes that he will observe these
particles to exist for a longer time than expected when placed in the vicinity of the circulating light beam. A
longer lifetime means that the particles must have flowed through a time loop into the future.
“Say you have a cup of coffee and a spoon,” Mallett explained to ​PhysOrg.com​. “The coffee is empty space,
and the spoon is the circulating light beam. When you stir the coffee with the spoon, the coffee – or the empty
space – gets twisted. Suppose you drop a sugar cube in the coffee. If empty space were twisting, you’d be
able to detect it by observing a subatomic particle moving around in the space.”
And according to Einstein, whenever you do something to space, you also affect time. Twisting space causes
time to be twisted, meaning you could theoretically walk through time as you walk through space.
“As physicists, our experiments deal with subatomic particles,” said Mallett. “How soon humans will be able to
time travel depends largely on the success of these experiments, which will take the better part of a decade.
And depending on breakthroughs, technology, and funding, I believe that human time travel could happen this
century.”
Step back a minute (sorry, only figuratively). How do we know that time is not merely a human invention, and
that manipulating it just doesn’t make sense?
“What is time? That is a very, very difficult question,” said Mallett. “Time is a way of separating events from
each other. Even without thinking about time, we can see that things change, seasons change, people change.
The fact that the world changes is a feature of the physical world, and time is independent of whether or not we
have a name for it.
“To physicists, time is what’s measured by clocks. Using this definition, we can manipulate time by changing
the rate of clocks, which changes the rate at which events occur. Einstein showed that time is affected by
motion, and his theories have been demonstrated experimentally by comparing time on an atomic clock that
has traveled around the earth on a jet. It’s slower than a clock on earth.”
Although the jet-flying clock regained its normal pace when it landed, it never caught up with earth clocks –
which means that we have a time traveler from the past among us already, even though it thinks it’s in the
future.
Some people show concern over time traveling, although Mallett – an advocate of the Parallel Universes
theory – assures us that time machines will not present any danger.
“The Grandfather Paradox [where you go back in time and kill your grandfather] is not an issue,” said Mallett.
“In a sense, time travel means that you’re traveling both in time and into other universes. If you go back into
the past, you’ll go into another universe. As soon as you arrive at the past, you’re making a choice and there’ll
be a split. Our universe will not be affected by what you do in your visit to the past.”
In light of this causal “safety,” it’s kind of ironic that what prompted Mallett as a child to investigate time travel
was a desire to change the past in hopes of a different future. When he was 10 years old, his father died of a
heart attack at age 33. After reading ​The Time Machine​ by H.G. Wells, Mallett was determined to find a way to
go back and warn his father about the dangers of smoking.
This personal element fueled Mallett’s perseverance to study science, master Einstein’s equations, and build a
professional career with many high notes. Since the ‘70s, his research has included quantum gravity,
relativistic cosmology and gauge theories, and he plans to publish a popular science/memoir book this
November 2006. With help from Bruce Henderson, the ​New York Times​ best-selling author, the book will be
called ​Time Traveler: A Physicist’s Quest For The Ultimate Breakthrough.​
By Lisa Zyga, Copyright 2006 PhysOrg.com
QUESTIONS:
1.
2.
3.
4.
5.
How does Professor Mallett propose to construct a time machine?
How will Mallett know if his time machine is successful?
What did the clock on the airplane experiment prove?
What is the “Grandfather Paradox”?
Why does Mallett want to create a time machine?