AstroNews 5/2000

TIME'S ARROW SPECIAL 

TOTAL ECLIPSE OF THE MOON
COMING TO A SKY NEAR YOU

In the wee hours of SUNDAY JULY 16 to be precise. Visible on the WEST COAST of the USA as well as many other places on Earth, like Central Asia and East Africa. Mark your calendar! Find a spot where the skies are clear and the clouds are few. Dress warm. Bring a blanket and a pillow. And don't forget the popcorn.
DETAILS are here!
 

Why is the sky so EMPTY this month? Because there are FEWER stars in the evening sky now than at any other time of the year! There are still plenty of opportunities to check out some dazzlers - like the constellation HERCULES (see below) and all those FUZZY OBJECTS far from our home galaxy of the Milky Way.
 

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Up This Month
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TERRA DAY

Terra has FIVE INSTRUMENTS that measure such things as the moisture content of clouds, vegetation on Earth and sunlight. The data will give scientists a better idea of how Earth's components work together as a system. Scientist will use the data to build computer models of complex Earth interactions. The first model is due in 2005.

The $1.3 billion Terra spacecraft was launched in December 1999 and the mission is expected to last six years.NASA plans to encourage widespread use of information from Terra to provide citizens, businesses and governments with the means to make informed decisions on issues such as health, safety, economic well-being and quality of life.

Terra Website:
http://terra.nasa.gov/

If you've been reading AstroNews you know that WINDOWS and MAC users can download the SETI@home software for free. SETI@home is your best chance at contacting aliens: a SCREEN SAVER that analyzes signals from space and could change our entire civilization! Only 790 k in size and tested by over two million humans - making it the largest supercomputer on earth!

Get SETI@home version 2.04 NOW:
http://setiathome.berkeley.edu

STAY IN TOUCH! Try the long distance services offered by GlobalCom. ANY domestic US calls from ANY phone for only 6.9 cents/min! No more expensive calls! Check out this offer AND MANY MORE at:
http://www.kahl.net/global

SPACE CENTER DOWN UNDER

The approval was the last remaining regulatory hurdle before work could begin on the project later this year, said Asia Pacific Space Center Pty. Ltd. (APSC), which plans to build and run the launch site.

The first commercial launch is expected in early 2003. The space center will be the first of its kind in Australia and will be geared to the geostationary and low-Earth orbit markets.

The remote island, about 2,600 km (1,600 miles) off the country's northwest coast, is close to the equator where rocket launches gain maximum assistance from the Earth's rotation.

Fullgrabe said there would be significant economic benefits for Christmas Island with its population of about 1,275, especially in employment and infrastructure projects. The space center will be built on the south point of the island.
[Source: Reuters]
 
 

CALIFORNIA'S COMMERCIAL SPACEPORT

Operated and managed by Spaceport Systems International, L.P. (SSI), the Spaceport is a major provider of payload processing and launch services for both commercial and government users. SSI is the first federally licensed private "Commercial Space Launch Site Operator" in the United States.

The spaceport is at Point Conception, a Chumash site known as Humqaq (“The Raven Comes”). The Chumash believe that it was at Humqaq that the souls of the dead left the Earth to begin their journey to heaven.

The Chumash were one of the largest native groups in the western US. Today, 200 descendants of the Tsmala Chumash inhabit the 99- acre Santa Ynez Reservation, the only federally recognized Chumash reservation in the US. The majority of the 3,000 descendants of the Chumash live outside the reservation and lack both land and federal recognition.

The coalition between the aerospace industry, local and state politicians, and big business pushed ahead with construction without consulting the Chumash or including them on their planning boards. The Chumash deserve the public’s support in this classic battle between corporate America and a relatively impoverished native population.
[Source: Earth Island Journal, Dr John Anderson]

References:
http://expage.com/socialcom
http://www.earthisland.org/eijournal/fall98/fe_fall98spaceport.html
http://www.calspace.com
 

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AstroTip
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HUNT FOR HERC

How do you find Herc? It's a bit tricky. How good are you at finding stars? Remember how to "Arc to Arcturus" or "Spike to Spica"? If not, you better check the May 1999 AstroNews online for details!

Here's a quick summary: locate the Big Dipper high in the north, follow the handle's arc to the bright golden star Arcturus. It's part of Bootes (the Herdsman).

If you continue in this direction you can "Spike to Spica" -- that means head for the bright star Spica. It represents the spike of wheat in the hand of Virgo (the Maiden).

Now go BACK to Arcturus and CONTINUE about the same distance IN THE OTHER DIRECTION. There, you should reach the signature Keystone that represents the body of Hercules. What's a keystone? A wedge-shaped piece at the crown of an arch that locks the other pieces in place - a kind of trapezoid. If this makes absolutely no sense to you then grab a star map!

Remember, later is better than earlier for sighting this Hero: As the night wears on, Vega will rise, and Hercules is halfway between Arcturus and blue-white Vega.

The four stars of Hercules's Keystone have faint limbs trailing off. One of these is usually pictured as a bent knee. Don't worry if you can't find these arms and legs. Just hunt for Herc!

Please SUPPORT ASTRONEWS and use this link:

THE "EYEBALL" NEBULA

Resembling a glowing eye, the nebula was found to be 6,500 light-years away from Earth in a far region of the Milky Way galaxy. Its discovery is helping astronomers map stars in our home galaxy and understand the eventual fate of our own sun.

Planetary nebulas are big, bright clouds of gas and dust that puff out from an exploding, dying sun. They are so named not because they have anything to do with planets, but because of their round shape.

Astronomers are learning a great deal about planetary nebulas at the edge of our galaxy and beyond. But interestingly, they lack some important data about nebulas in our own Milky Way.

NGC 6751 is apparently an odd planetary nebula because it resembles another type of solar explosion called a supernova. It looks like somebody ripped it apart into little pieces. Experts aren’t sure why exactly this particular planetary nebula looks so odd compared to other planetary nebulas.

Astronomers expect that our own sun will someday end up as a similar planetary nebula after it dies. However, because our sun has large gaseous planets like Jupiter and Saturn surrounding it, it might look more like an elliptical egg than a circular eye when it does explode.
 
 

SPACECRAFT BUMPS COMET TAIL

A comet passed through the exact position that Ulysses -- a probe orbiting the sun that studies the solar wind -- occupied. The comet in question was the HYAKUTAKE comet, which was visible to the naked eye from Earth in 1996.

Comets are small icy objects that formed at the dawn of the solar system, some 4.5 billion years ago. As a comet nears the sun, its icy core boils off, forming a cloud of dust and gas called a head, or coma. Comets become visible when sunlight reflects off this cloud. As the comet gets closer to the sun, more gas is produced. The gas and dust is pushed away by charged particles known as the solar wind, forming two tails. Dust particles form a yellowish tail, and charged gas makes a bluish ion tail. A comet's tails always point away from the sun.

Clues about Ulysses’ contact with Comet Hyakutake’s tail began to appear when a team of scientists who were studying charged particles emanating from the sun noticed something odd in their data.

The collision will help comet experts understand the life cycle and fate of comets, which many think of as prehistoric relics from the earliest days of the solar system. In particular, the discovery of such a long comet tail invites astronomers to believe that they may find and study past comets whose tails are still intact.

Today, Comet Hyakutake is far, far away from the Earth: 1.2 billion miles (2 billion kilometers), to be exact. But astronomers speculate that there will always be new comets flying in the vicinity of our home planet. As a result, a cometary impact on Earth is always a possibility and concern. However, scientists now say they may be able to use the results from the Ulysses-Hyakutake finding to study the probability of comets hitting the Earth.
[Source: space.com . 04.07.00]
 

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FAR OUT FACT
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ESREVER NI EMIT

Just moments ago a shell of tortured matter was flying together at 30 000 kilometres a second. Now it has become a star, and the last shreds of glowing debris are being sucked in. With the explosion undone, the star begins the long journey back to the time when it will be UNBORN into the gas and dust of an interstellar cloud.

Is someone running the film backwards for comic effect? Not necessarily. In 1999, Lawrence SCHULMAN of Clarkson University in Potsdam, New York dropped a bombshell. He showed that regions where TIME FLOWS in the NORMAL direction can COEXIST with regions where it FLOWS BACKWARDS!! There could be places, perhaps even within our Galaxy, where stars unexplode, eggs unbreak and living things grow younger with every second.

To understand how time could run backwards, you need to understand why it has a preferred direction at all. Physics say particles of matter don't care what direction time runs in: any interaction between two particles could happen just as easily in reverse. (Some nuclear interactions do show a small bias, but no one has found a way to turn this into an arrow of time.)

But when you have a lot of particles instead of just two, things change. Messy, disordered states tend to develop from tidier ones. This tendency is called the thermodynamic ARROW OF TIME. Physicists say that ENTROPY - a measure of disorder - always increases. "It's easy to break an egg, difficult or impossible to put the pieces back together," says Schulman.

Say the air in a large room is confined in a 1-metre cube in one corner, then released. It is perfectly possible that, after five minutes, the air molecules will all be back in the same 1-metre cube. Perfectly possible but hugely IMPROBABLE, because there are far more ways to arrange the individual molecules when they are spread out than when they are confined. In fact, the most disordered state-in which the air molecules are spread more or less evenly throughout the room-can be achieved in far more ways than any other state. "This is the second law of thermodynamics," says Schulman, "which seals the fate of Humpty Dumpty."

However, argues Schulman, a reverse arrow is perfectly possible: "It's all down to the 'boundary conditions'-the external constraints imposed on the system." In the room, the air has to be in the 1-metre cube only at the start of the five-minute period. There is no constraint on it at the end of the five minutes-the system can find its own final state.

But say a final condition is imposed. After five minutes, the air molecules have to be back in the 1-metre cube. On Earth, this is clearly an artificial situation. But for Schulman, it is perfectly legitimate to consider such a state of affairs. "There is no reason in principle why the Universe might not have a future boundary condition imposed on it," he says.

The future condition would constrain the molecules to follow only a tiny subset of trajectories, ending up in the 1-metre cube. From our point of view, time would be running backwards.

But there's an objection to having forward and backward time regions in the same universe. Surely the arrow of a reverse-time region would be wiped out by the slightest interaction with a normal-time region, leaving a completely disordered system with no arrow at all?

Imagine a GAME OF POOL in which the triangle of balls is struck by the cue ball and scattered around the table. Now imagine the reverse-time scenario. For the balls to follow the precise trajectories necessary to finish in a triangle will take a MONUMENTAL amount of coordination. The slightest disturbance will spoil it. Any interaction with a region with normal time-for instance, the smallest cry of amazement from someone watching-could vibrate the air, nudge the balls and wreck everything. So the backward arrow of a reverse-time region would be instantly destroyed by any interaction with a normal-time region.

Schulman sees a flaw in this idea. The two systems are on an EQUAL FOOTING, so the reverse-time region is AS LIKELY to destroy the arrow of the normal-time region as vice versa. "All we can say is that if the two regions interact their arrows will either both be destroyed or both survive."

Most physicists would have put good money on the former possibility. But Schulman's startling conclusion is that as long as the interaction between the two regions is weak, both arrows will survive. He bases this claim on a simple computer model that allows him to set up weakly interacting systems with opposite arrows of time and see what happens.

HERE'S HOW IT WORKS. Take a square 1 unit on each side, and add a particle with coordinates x and y. Move the particle by repeatedly replacing x with x + y and y with x + 2y, and discarding any integer parts of the results (so x and y stay in the range from 0 to 1). The particle will flit about the square chaotically. "This mimics the essential BEHAVIOR OF A GAS PARTICLE, while being a lot simpler than reality," according to Schulman.

To set up two gases with opposite arrows of time, Schulman imposes appropriate boundary conditions. In one model gas, the particles start in one corner of the square and spread out until they are completely disordered. They have a "normal" arrow of time (that is, the same arrow as us). In the other, Schulman imposes the final condition that after, say 20 moves, corresponding to 20 time steps, the particles are all in the corner of the square. This system has a backward arrow of time. Call the normal-time region ALICE and the reverse-time region BOB.

The next step is to LET ALICE AND BOB INTERACT. Schulman tweaks the coordinates of each normal-time particle according to the coordinates of the reverse-time test particle, and vice versa.

When Schulman lets both systems run, he finds that neither arrow of time is destroyed by the other. "All that happens is that Bob adds a bit of noise to Alice and Alice adds a bit of noise to Bob," says Schulman. The two arrows of time are remarkably robust.

"I had no idea when I started my work that this would be the outcome," he says. "The result surprised me as much anyone else." But this surprise, he adds, comes from a prejudice against future boundary conditions. Once you are used to the idea of matter having some MEMORY of what we call its future, it ceases to surprise. From our point of view, the memory of future organisation drags any reverse time region in the direction of increasing order, despite any small disturbances from our own "normal" region.

The paper has created quite a stir. "This is very cool stuff indeed," says Max Tegmark of the University of Pennsylvania. At the Technion-Israel Institute of Technology, where Sculman began this work, Amos Ori agrees. "Schulman has shown that the consistency of a model with two simultaneous time arrows can be explored by relatively simple means. This is a very important observation."

And he has some equivocal support from David Pegg of Griffith University in Brisbane. "I see no obvious flaw in the calculations Schulman has done. He makes his case quite well and I am willing to accept it, at least until convinced otherwise."

Other physicists don't believe that Schulman's computer model is relevant to the real world. According to Paul Davies of the University of Adelaide, a real physical system with a backward arrow would be so fantastically SENSITIVE to an outside influence that it would be easily destroyed. "Imagine a box of gas with molecular velocities reversed to bring about an ordered state," he says. "The gravity of a single electron at the edge of the observable Universe is enough to throw out the motion of a given molecule by 90 degrees after only 20 or so intermolecular collisions. That's pretty sensitive."

CROSSING THE DIVIDE

Surprisingly, Schulman does not dispute Davies' point. "He's absolutely right. But the very set-up of his thought experiment, with initial conditions only, precludes an opposite-directed arrow," he says. "My result applies when boundary conditions are imposed at two separate times."

Some might attack the realism of Schulman's interaction, which he admits is an abstract mathematical one and not related to a real physical force such as gravity. "Nevertheless, I maintain that the interaction is adequate for treating the conceptual issue of the effects of future-conditioning," he says.

So could we actually see reverse-time beings if they exist, and maybe even wave to them? Remarkably, Schulman says yes. Using a theory originally developed by Richard FEYNMAN and John WHEELER, which treats light waves travelling in both time directions on an equal footing, he shows that forward and reverse regions could communicate by light signals.

But COMMUNICATING with the other side has its DANGERS. If  normal-time Alice were to see rain pouring out through reverse-time Bob's window, she could wait until before the rain started and shout to Bob to close his window. "So did Bob's floor get wet or not?" says Schulman.

Perhaps something intermediate happens which smears out the paradox. "Alice sees the window open, shouts to Bob but the message gets blurred and Bob doesn't close the window," says Schulman.

And there's another, more disturbing possibility. "If you impose initial and final boundary conditions, it may turn out that the events described simply can't happen," he says. "In mathematical terms, they are simply not a solution." In other words, we might just be fated not to cause any paradoxes.

So, how would a reverse-time region arise? Schulman says such regions may exist for the same inexplicable reason that regions of normal time exist. But there is one more concrete possibility: perhaps we live in a Universe whose expansion from a BIG BANG will one day be reversed into a contraction down to a "BIG CRUNCH", a sort of mirror-image of the big bang in which the Universe was born 13 billion years ago. Although the latest cosmological evidence is AGAINST this, the question isn't settled.

In 1958, Thomas Gold of Cornell University argued that the thermodynamic arrow of time would reverse during the contraction phase, creating order out of chaos. Gold's reasoning turned out to be flawed, but in the 1970s, Schulman used his own model to show that the conclusions were right. As the big bang and big crunch are both highly ordered (all the matter is in a small volume), thermodynamic arrows of time should point away from both ends. The arrow of time depends on the expansion or contraction of the Universe. "Coffee cools because the quasar 3C 273 grows ever more distant," says Schulman.

Of course, if you were alive during a cosmic contraction phase you would see nothing untoward-you'd have the same arrow as most of the matter in the Universe, and it would look like expansion (see Diagram). Stepping outside the Universe, the situation appears perfectly symmetrical; it makes just as much sense to call either end the big bang or the big crunch.

A bizarre consequence of Schulman's theory is that some reverse-time regions from a future contracting phase of the Universe could have survived until today-and could be only a few tens of light years away. "Some bits of the Universe might have reverse arrows while other bits with forward arrows might survive well into the contraction phase."

As the "turnaround" time when the Universe's expansion turns into contraction could be many hundreds of billions of years away, any stars would have burnt out. Unfortunately, there would be little prospect of seeing stellar unexplosions or backwards people among such cold stuff. "We would still feel their gravity, though," says Schulman. "Such reverse-time matter would have all the attributes of the invisible, or 'dark', matter thought to make up most of the mass of our Universe."

COLLIDING MATTER

Another possibility is that in the 13 billion years since the big bang most of the Universe's matter has collided with reverse-time matter from the future. The result of such collisions would be matter in "equilibrium" with no time direction. "Once again, it would appear exactly like dark matter," says Schulman. Other physicists are sceptical. "I doubt that this has anything to do with the dark matter problem," says Tegmark.

So what would it be like in a region that is changing its time direction? Would exploding things suddenly start unexploding? And what would happen to the minds of beings around at the time? Sadly, it would be rather undramatic. For a particular area to change its arrow, it would first have to go through a period of maximum disorder where there could be no stars or explosions or structured, working minds. But if you survived for long enough, you might be able to watch the Universe around you starting to contract, and most of its matter going into reverse.

If all this is getting a bit difficult to stomach, there is A WAY TO TEST IT-even if we can't spy on a nearby backwards planet. "Things happening today could be influenced by boundary conditions at the end of the Universe," says Schulman. What he has in mind are ultra-slow processes.

In the 1970s, John Wheeler of Princeton University suggested observing the decays of atomic nuclei with ultra-long half-lives, perhaps many tens of billions of years. The suggestion was that the normal exponential decay would be modified by exponential "undecay" and that this might actually be observable in a sample of a few kilograms in the laboratory. Possible candidates are rhenium-187 and samarium-147, which have half-lives of about 100 billion years.

Unfortunately, Wheeler was too optimistic. For an experiment of a sensible duration, a few years, say, you'd need roughly the total supply of these isotopes in the Universe to see deviations from exponential decay.

"A far better bet is galaxy clustering," says Schulman. He believes that the way galaxies cluster together could be affected by a future contraction phase. Unfortunately, he has not yet worked out what form this effect might take.

But over the past few years, a small group of of physicists have been claiming that the Universe has an inexplicable FRACTAL structure. Most cosmologists disagree, partly because they have no way to explain such a bizarre pattern. But say there is something in it. Could it perhaps be a MEMORY OF THE FUTURE?
 
 

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