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Title: Physics/Relativity/Time Travel - Taking the Cosmic Shortcut The future, Einstein's special theory of relativity, the past, theory of gravitation, black holes, wormholes, negative energy and links.
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TIME_LOOPS An interview with Paul Davies, paradox, wormhole, black hole, Newtonian mechanics and quantum computations.
| The_Time_Machine Einstein's theory, special relativity, communication faster than light, quantum cosmology, interview with Carl Sagan and links.
| Time,_Time_Travel_&_Traversable_Wormholes Links to articles and sites about the possibility and impossibility of time travel.
| Time_Travel Simple explanation, black hole containment device, mathematics, energy equation, chaos and super string theories, power of the crystal, FAQ and links.
| Time_Travel_-_A_Discussion Hyperspace, space-time continuum, black holes, wormholes, parallel universes, quarks, tachyons, quantum and super string theories.
| Time_Travel_-_Fact_or_Fiction The science fiction paradigm, conservation laws, general relativity, paradoxes, tachyons and graphs.
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Taking the Cosmic Shortcut - ABC Science Online
     
This
article originally appeared in the February 2002 edition of Helix.
Imagine
seeing the dinosaurs first-hand, visiting your great, great, great grandchildren
in the 22nd Century, or travelling to the other side of the Milky Way
in an instant. Time travel and wormholes used to belong to the realm of
make-believe. But, with a little inspiration from some creative writers
and thinkers, Elizabeth Warnes says physicists have
begun to show us that science fact can be just as strange as science fiction.
Travelling
into the future...
ONLINE
FORUM
The Lab & CSIRO joined forces to bring
Dr Charley Lineweaver, Professor
Ray Norris, Dr Joss Hawthorne and Tamara
Davis online to discuss the possibilities
and paradoxes of time travel and wormholes.
You
can read what they had to say
here.
Einstein's special theory of
relativity shows that time travel into the future is possible. The theory
demonstrates that the way we perceive time is relative to our motion.
Objects travelling at speeds close to the speed of light (about 300 000
kilometres per second) age more slowly than stationary objects.
In 1975, Professor Carrol Alley
tested Einstein's theory using two synchronised atomic clocks. Carol loaded
one clock onto a plane, which was flown for several hours, while the other
clock remained on the ground. At the end of its flight, the clock on the
plane was slightly behind the one on the ground. Time had actually slowed
down for the clock on the plane. It had travelled forward in time.
Into
the past?
A
black-hole-powered jet of sub-atomic particles travelling at nearly
the speed of light out of the M87 galaxy.
But what about time travel
into the past? In theory, the laws of physics tell us that backward time
travel may be possible. However, there are many problems with putting
these ideas into practice. Ronald Mallett, Professor of theoretical physics
at Connecticut University,
made one of the most promising discoveries to date.
According to Einstein's theory
of gravitation, any object with mass will cause a warp in space-time,
similar to a bowling ball on a mattress. Because space and time has been
stretched, clocks operate slower close to Earth than in the vast areas
between galaxies. Previous theoretical designs of time machines have used
this concept of mass distorting space-time, however they would require
a tremendous amount of energy to work.
Ronald
Mallet's Theoretical Time machine
Ronald Mallett believes that
anything containing energy could warp space-time, and as a result, he
has designed a time machine that uses light, rather than mass.
His theoretical time machine
consists of a ring of two intense beams of light,
Rollover
or click on this image for a closer look at Ronald Mallett's Time
Machine.
circling in opposite directions.
By slowing down the light in an ultra-cold bath of atoms and increasing
the intensity of the beams, space-time inside the ring would become warped.
Eventually, space and time would become so distorted by the circling light
that time would become a dimension similar to space - a dimension that you
could move along! If you entered the ring and walked in the correct direction,
you could walk back through time - maybe even passing yourself as you entered
the ring!
Why
you haven't met someone from the future
However, putting Ronald's theory
into practice presents plenty of problems. For example, the temperature
of the ring would have to be close to absolute zero (-273°C), so humans
would find it difficult to use. It would also be impossible to travel
back to a time before the machine was switched on. This explains why people
from the future haven't visited us - we are yet to build a time machine
for them to exit from.
Ronald hopes that travellers
from the future may be able to overcome these difficulties and use the
rings of light that we construct today as portals to our time.
Wormholes
So, you want to travel across
the universe without wasting years in a space ship? Wormholes might just
be the answer.
The universe appears as three
dimensions in space (up-down, left-right, and forward-backward) and a
fourth dimension known as time. Wormholes are connections between two
different places in space and time. Although this is difficult to visualise
in four dimensions, it is easier to see in two.
Imagine two points on an enormous
sheet of paper, several metres apart. You could travel between the points
by following a line on the piece of paper. Alternatively, you could fold
the paper over so that the two points touch. By folding the paper, you
are making a 'wormhole' in the two-dimensional paper world.
Although there is no experimental
evidence for the existence of wormholes, theorists believe that they may
exist. Wormholes first appeared possible in Einstein's theory of gravity,
in 1913.
However, physicists had almost
forgotten about them until the mid-eighties, when Carl Sagan included
them in his novel Contact, wherein Ellie Arroway, the main character in
the book, travels to the centre of our galaxy through a wormhole. A scientist
himself, Carl wanted to describe the wormhole with as much scientific
accuracy as possible. He asked Kip Thorne, a physicist at the California
Institute of Technology, to examine the general properties necessary for
a wormhole to stay open.
Negative
energy
Circinus,
a 'seyferts' type of galaxy, which has a compact centre and is believed
to contain massive black holes.
To be stable wormholes need
lots of negative energy - a rather exotic commodity in the universe. Such
energy has not yet been found, but quantum mechanics suggests that it
does exist. The problem is that we don't know whether the laws of quantum
mechanics allow enough negative energy to be concentrated in such a way
as to allow wormholes to exist.
Although wormholes could exist
throughout the universe, one possible location is at the centre of black
holes. Travelling through one of these might prove extremely difficult
however, since the wormhole would be so unstable that it would collapse
as soon as a spaceship (or even a ray of light) entered it. This is because
there would not be enough negative energy to hold it open.
Recently, a group of scientists
claimed they found a way of detecting the entrances and exits to wormholes.
A wormhole contains enough negative energy, also known as exotic matter,
to cause passing rays of light to be deflected away. This effect is similar
to gravitational lensing, which occurs when light from a far away object
is bent by the gravity of a massively heavy object, such as a wormhole,
black hole or other 'heavy' object. The lensing reveals a distinctive
pattern that astronomers are able to detect.
Gravitational
lensing occurs when light from a far away object is bent by the gravity
of a massively heavy object, such as a wormhole
But don't pack
your bags for a wormhole holiday just yet. Current research indicates
that it is impossible to open wormholes bigger than 10-35 metres. Therefore,
it will take more creative thinking before any scientist or novelist can
fit a human into a wormhole - especially one that small!
Online
Forum
Read what some
big names in astrophysics have to say about the possibilities
and paradoxes of time travel and wormholes on this joint Lab and CSIRO
forum.
More
Information
Double
Helix Magazine
Time
travel
Dr
Karl explains the complexities of the fourth dimension - time.
Jump on board the Kinetic
City's Lab Car where you can have fun with forces, defy gravity and
test the laws of physics.
Examine the ins
and outs of wormholes and time travel with the Science Show's Unknown
Reporter.
Physicist Paul Davies describes
to Robyn Williams the ideas in his new book, "How
to Build a Time Machine".
Wormholes
Read how the Australian
National University Physics department compares wormholes in science
fiction to those in reality.
All you wanted
to know about wormholes revealled to you in a student slide
show.
Chat about wormhole
theory with some friends of Sydney University.
See what
other theorists have to say about Russian expert in relativity, Sergei
Krasnikov's work.
 
Published 21/2/2002
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The | future, | Einstein's | special | theory | of | relativity, | the | past, | theory | of | gravitation, | black | holes, | wormholes, | negative | energy | and | links. |
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