Another perspective on Time Travel

"The short answer is that time travel into the future is not only possible, it's been done, and we've known about it for over a century," says Davies. "The reason that the public doesn’t seem to know about it is because the amount of time travel involved is so pitifully small that it doesn't make for a 'Doctor Who' style adventure."

A phenomenon called time dilation is the key here. Time passes more slowly the closer you approach the speed of light -- an unbreakable cosmic speed limit. As such, the hands of a clock in a speeding train would move more slowly than those in a stationary clock. The difference would not be humanly noticeable, but when the train pulled back into the station, the two clocks would be off by billionths of a second. If such a train could attain 99.999 percent light speed, only 1 year would pass onboard for every 223 years back at the train station.

WATCH VIDEO: Is time travel possible? Theoretical physicist Michio Kaku explores the possibilities.

But speed isn't the only factor that affects time. On a much smaller scale, mass also influences time. Time slows down the closer you are to the center of a massive object.

"Time runs a little bit faster in space than it does down on Earth," Davies says. "It runs a little faster on the roof than it does in the basement, and that's a measurable effect."

A clock aboard an orbiting satellite experiences time dilation due to both the speed of its orbit and its greater distance from the center of Earth's gravity.

"Both gravity and speed can give you a means of jumping ahead," Davies says. "So in principle, if you had enough money, you could get to the year 3000 in as short a time as you like -- one year, one month, whatever it takes. It is only a question of money and engineering."

SLIDE SHOW: Which time traveling movies are the most feasible? We ask physics author Ron Mallett for his top 5 sci-fi films.

Forward, not back?

Time travel into the future is an established and fundamental aspect of Albert Einstein's theory of relativity. Scientists have tested and retested this in both experimental and practical settings. But what about time travel in the opposite direction?

"Going back in to the past is a whole different kettle of fish." Davies says. "There's nothing in Einstein's theory, which is the best theory that we have about the nature of time, which precludes it. There's nothing in even his general theory of relativity, published in 1915, which precludes travel back into the past, but many scientists are deeply uneasy about it because of all the well-known paradoxes that it unleashes."

For instance, imagine going back in time and killing your own mother. Then she'd never give birth to you, and just how would you have been able to travel back in time to commit matricide in the first place?

WIDE ANGLE: Is sci-fi time travel possible?

Wormholes as spacetime shortcuts

Davies surmises that, given our current understanding of the nature of time and physics, time travel into the past simply isn't possible. But the universe is full of mysteries, and one of them -- the hypothetical wormhole -- might just permit such a journey.

"This is a little bit like a tunnel or shortcut between two distant points," Davies says, "So for example, if I had a wormhole here in my hotel room and I jumped through it I wouldn't come out on Pennsylvania Avenue, I'd maybe come out near the other side of the galaxy."

Scientists have theorized that such a shortcut through time and space could be turned into a time machine.

"If a worm hole could exist and could be traversable, then it would provide a means of going back in time," Davies says. "So it all hinges on whether stable wormholes are a reality or if there's some aspect of physics -- not relativity, because there's nothing wrong from that point of view -- but some other aspect of physics might intercede and prevent the wormhole from forming. That's an open question."

World-famous theoretical physicist Stephen Hawking has proposed that wormholes occurring at a quantum level could theoretically provide a foothold for time travel, but University of California at Santa Barbara physicist Andrew Cleland urges caution on that front.

"I'm an experimentalist, and physics is ultimately an experimental science," Cleland says. "Any predictions that are made based on mathematics or on philosophical or intellectual speculation have to pass the test of experiment, and I am certainly not aware of any experiment that demonstrated the possibility of traveling backward in time."


Cause and effect

Cleland also points out that the fundamental principle of causality stands in the way of travel into the past. The entire universe, as we understand it, is beholden to this rule.

"Something occurs first and the outcome of that occurrence happens afterward," Cleland says, "and there has never to my knowledge been an experiment that came out different from that. I am not aware of any experimental tests of quantum mechanics that have shown any violation of causality, in spite of the fact that many experiments could reveal such a violation."

Still, in the same way that time dilation isn't flashy enough to seem like time travel into the future, the public often overlooks a very common means of "traveling" into the past.

"In a sense, astronomers are always traveling backward in time, but it is in a way that most people are not so excited about," Cleland says. "When we measure the cosmic microwave background, we're looking back more than 10 billion years in time. That's how long it took for the light to reach us."

A number of questions about time travel remain unanswered. Will time tourists from the future ever show up to help us out? We'll just have to wait and see. But if they come here using a wormhole time machine, we'll have to build one first. After all, you couldn't cross a bridge if only one side had been completed, right?

"Theoretically, it would take more than 100 years to create a 100-years' time difference between the two ends of a wormhole," Davies says, "so there's no way that our descendants could come back and tell us we're wrong about this."

Time Travel Impossible, Say Physicists (Submitted by Couloir Hanson)

A group of physicists from the Hong Kong University of Science and Technology have conducted research that allegedly proves time travel is a scientific impossibility by demonstrating that nothing can move faster than the speed of light.

The experiment allowed scientists to observe single photon particles at their maximum speed for the first time and also confirmed that a single photon moves just as fast as the speed of light in vacuum, if not up to 500 nanoseconds slower in certain conditions, according to PC Magazine.

With photons being a basic unit of electromagnetic radiation, or light, the research proves that light cannot move faster than light itself, making it impossible for anything else to move faster than light and debunking the theory of time travel.
The research findings detail that photons obey the laws of physics laid out in the principle of causality in Einstein’s theory of relativity. This states an effect cannot occur before its cause. Only the violation of this law would allow the possibility of time travel.
“By showing that single photons cannot travel faster than the speed of light, our results bring a closure to the debate on the true speed of information carried by a single photon,” said Professor Shengwang Du, lead researcher on the team.
The theory of time travel became especially popular 10 years ago when scientists observed “superluminal” behavior in the photons of optical pulses that seemed to move faster than the light, according to BBC News.

What is the Closest Star to Earth? (Submitted by Jimena Casas)

”What is the closest star to Earth?” is a trick question. Our Sun is by far the closest star to us. So, all games aside, let’s look at the stars outside of our solar system that are closest to Earth.
The closest star to our Sun would be one of the three in the Alpha Centauri system. The system is only 4.27 light years from the Sun. Alpha Centauri A is the primary in the system. It is slightly larger than our Sun. It has a similar yellowish color with a stellar classification of spectral type G2 V. It also rotates every 22 days compared to 25 for the Sun. The secondary, Alpha Centauri B, is slightly smaller and has a spectral type of K1 V. It is orangish-yellow compared to the primary. It is 90% as massive as our Sun and about 14% smaller in radius. It rotates every 41 days. The third in the system is called Proxima Centauri. It would technically, be the closest single star to our Sun at 4.22 light years.
After you move past the Alpha Centauri group, the next closest star to Earth, 4th closest overall, would be Barnard’s Star. This a spectral type M4 Ve star that is about 6 light years from the Sun and is located in the constellation Ophiuchus. It has received more hours of study than any other M class star because of its proximity. E.E Barnard discovered the star and measured its proper motion at 10.3 arcseconds per year. To date, this is the largest known proper motion of any star in relation to our Sun.
Next we move to Wolf 359. This star falls in the spectral type M6.5 Ve and is located in the Leo constellation. It is around 7.6 light years from the Sun. It is one of the faintest and lowest mass stars known. Absorption lines showing the presence of water and titanium have been observed in the star’s spectrum. It has a stronger magnetic field than our Sun, so it can undergo sudden increases in luminosity lasting for several minutes.
Those are the five stars closest to the Sun. Here are the next five:

• Epsilon Eridani
• 61 Cygni
• Procyon
• Tau Ceti
• Kruger 60

According to NASA data, there are 45 stars within 17 light years of the Sun. There are thought to be as many as 200 billion stars in our galaxy. Some are so faint that they are nearly impossible to detect. Maybe, with technological improvements, scientists will find even closer stars.

Largest Water Mass in Universe Discovered (Submitted by Anabella Gomez)

A reservoir of water that is 100,000 times the mass of the sun has been detected by an international team of astronomers in a vapor cloud surrounding a quasar 12 billion light years distant. As well as the huge quantity of water, the quasar - named APM 08279 5255 - also emits formidable amounts of energy.

The quasar's energy output - equal to that of 1,000 trillion suns - is generated by matter spiraling into a supermassive black hole at the center of the quasar. At a distance of 12 billion light years from Earth, the new observations reveal the object at a time when the universe was very young - perhaps only 1.6 billion years old.
The water vapor measured in the quasar represents the largest mass of water ever found, according to the astronomers. In an astronomical context, water is a trace gas, but it indicates gas that is unusually warm and dense. "The water measurement shows that the gas is under the influence of the growing black hole, bathed in both infrared and X-ray radiation," said study leader Matt Bradford of Caltech.
"These findings are very exciting," added co-discoverer Jason Glenn, from the University of Colorado. "We not only detected water in the farthest reaches of the universe, but enough to fill Earth's oceans more than 100 trillion times."
Most of the water in our own galaxy is frozen into ice and is found only in a limited number of regions, unlike the water in the distant quasar which appears to be distributed over hundreds of light years.
The water measurement, together with measurements of other molecules in the vapor source, suggests there is enough gas present for the black hole to grow to about six times its already massive size. Whether it will grow to this size is not clear, however, as some of the gas may end up forming stars instead, or be ejected from the quasar host galaxy in an outflow.
The discovery was made with a spectrograph called Z-Spec operating in the millimeter wavelengths (between infrared and microwave) at the Caltech Submillimeter Observatory, a 10-meter telescope near the summit of Mauna Kea, on the big island of Hawaii. Z-Spec's detectors are cooled to within 0.06 degrees Celsius of absolute zero in order to obtain the exquisite sensitivity required for these measurements.

The discovery highlights the utility of the millimeter and submillimeter band for astronomy, which has developed rapidly in the last two to three decades. To achieve the potential of this relatively new spectral range, astronomers, including the study authors, are now designing CCAT, a 25-meter telescope for the high Chilean Atacama desert. With CCAT astronomers will discover some of the earliest galaxies in the universe, and will be able to study their gas content via measurements of water as well as other important gas species.

10 Amazing Astronomy Facts (Submitted by Maricris Losilla)

Even though man has studied the heavens for thousands of years, we still know very little about the Universe we live in. And as we continue to learn more, we are consistently amazed, and sometimes confused, by what we learn. Here is a collection of amazing, interesting, and strange astronomy facts, in no particular order.

• Scientists believe that we can only see about 5% of the matter in the Universe. The rest is made up of invisible matter (called Dark Matter) and a mysterious form of energy known as Dark Energy.
• Neutron stars are so dense, that a soup can full of neutron star material would have more mass than the Moon.
• The Sun produces so much energy, that every second the core releases the equivalent of 100 billion nuclear bombs.
• Galileo Galilei is often incorrectly credited with the invention of the telescope. Instead, historians now believe the Dutch eyeglass maker Johannes Lippershey as its creator. Galileo was, however, probably the first to use the device to study the heavens.
• Black Holes are so dense, and produce such intense gravity, that even light can not escape. Theoretical physicists predict that there are situations under which light can escape (which is called Hawking radiation).
• Light from distant stars and galaxies takes so long to reach us, that we are actually seeing objects as they appeared hundreds, thousands or even millions of years ago. So, as we look up at the sky, we are really looking back in time.
• The Crab Nebula was produced by a supernova explosion in 1054 A.D. The Chinese and Arab astronomers at the time noted that the explosion was so bright, that it was visible during the day, and lit up the night sky for months.
• Shooting stars are usually just tiny dust particles falling through our atmosphere. Comets sometimes pass through Earth’s orbit, leaving trails of dust behind. Then as Earth plows through the dust in its path, the particles heat up, creating the streaks in the night sky.
• Even though Mercury is the closest planet to the Sun, temperatures can reach -280 degrees F. Why? Since Mercury has almost no atmosphere, there is nothing to trap heat near the surface. So, the dark side of Mercury (the side facing away from the Sun) is very cold.
• Venus is considerably hotter than Mercury, even though it is further away from the Sun. The thickness of Venus’ atmosphere traps heat near the surface of the planet.

Atlantis has landed, ending NASA's shuttle era

CAPE CANAVERAL, Florida, July 21, 2011 (Reuters) — The space shuttle Atlantis returned from NASA's final shuttle mission on Thursday, ending a 30-year era that opened the space frontier, exposed its dangers and established a toehold for future endeavors beyond Earth.

Space shuttle Atlantis STS-135 lands at the Kennedy Space Center in Cape Canaveral, Florida July 21, 2011. REUTERS/Scott Audette

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NASA workers lined the runway at the Kennedy Space Center in Florida before dawn to greet Atlantis and its crew after a 13-day cargo run to the International Space Station and to mark the conclusion of the shuttle program after 135 flights.
"I saw grown men and grown women crying today, tears of joy to be sure," said shuttle launch director Mike Leinbach. "Human emotions came out on the runway today. You couldn't suppress them."
Sailing through an unusually clear and moonlit night, Atlantis commander Chris Ferguson gently steered the 100-tonne spaceship high overhead then dived toward the swamp-surrounded landing strip a few miles (kilometers) from where Atlantis will go on display as a museum piece.
Double sonic booms shattered the silence, the last time residents will hear the distinctive sound of a shuttle coming home.
Ferguson eased Atlantis onto the runway at 5:57 a.m. EDT, ending a 5.2 million mile (8.4 million km) journey and closing a key chapter in human space flight.
"Mission complete, Houston," Ferguson radioed to Mission Control.
Kennedy Space Center director Bob Cabana told reporters: "It's been our number one goal the last couple of years to safely fly out the shuttle program and we accomplished that."

How does watching too much TV affect you?

HealthDay News

Too Much TV Raises Risk of Diabetes, Heart Disease, and Death

An analysis found that two hours of TV per day increases the chances of health problems by up to 20 percent.

By Maureen Salamon, HealthDay News

Tuesday, June 14, 2011 (HealthDay News) — Couch potatoes beware: All those hours in front of the TV may be making you sick, or even killing you.
Watching television for two to three hours or more per day is linked to significantly higher risks of developing diabetes and heart disease and dying from all causes, according to a new analysis from the Harvard School of Public Health.
Noting that Americans watch an average of about five hours of TV per day — the most common daily activity aside from working and sleeping — researchers analyzed data from eight studies done between 1970 and 2011 on the association between TV viewing and incidence of type 2 diabetes, fatal or nonfatal cardiovascular disease and all-cause mortality.
Two hours of daily television watching was tied to a 20 percent greater risk for diabetes, a 15 percent higher chance of cardiovascular disease and a 13 percent elevated risk for all-cause deaths, according to the new Harvard meta-analysis, a type of research that pools data from different studies on an issue and analyzes them to look for statistical trends.
The findings are published June 15 in the Journal of the American Medical Association.
"The results really are not surprising at all. We already know that people who watch a lot of TV are more likely to eat an unhealthy diet and be obese," said senior study author Dr. Frank B. Hu, a professor of nutrition and epidemiology. "The message is actually quite simple . . . those who watch a lot of TV should cut back on TV watching and do more of something else."
Americans are hardly extraordinary in being glued to the tube. Hu pointed out that many people around the world structure their days in a similar fashion, with Europeans and Australians respectively spending an average of 40 percent and 50 percent of their daily free time watching television.
Prior research has established the negative health effects of TV viewing, including associations with less physical activity and unhealthy eating, such as higher consumption of fried foods, processed meat and sugar-sweetened beverages and lower intake of fruits and vegetables. Cancer incidence has not typically been studied in relation to TV watching, Hu said.
"There's no question this paper draws attention to the number of studies now that all seem to show the same thing," said Dr. Martin Abrahamson, chief medical officer of the Joslin Diabetes Center in Boston. "There are always limitations to these meta-analyses, but I think they're telling us a message we need to take heed of."
Based on disease incidence in the United States, Hu and his colleague, Anders Grontved, estimated that each two-hour increment of TV watching each day was linked to an absolute risk of 176 new cases of type 2 diabetes, 38 new cases of fatal cardiovascular disease and 104 new cases of all-cause mortality among 100,000 people per year.
Abrahamson and Hu agreed that the particularly ominous influence that TV has on diabetes incidence is due largely to its link to obesity, one of the biggest contributors to diabetes.
They also said that those who spend several hours per day exercising may be able to offset the negative health effects of prolonged TV watching, but that few tend to split their time equally between the two disparate activities.
"Certainly any physical activity would be beneficial regardless of the amount of TV you watch," Hu said. "But the reality is that people spend almost five hours a day watching TV. How much exercise do they do? There is a huge imbalance."