My Daily Inquirer

The end of the world as we know it cannot be avoided, but it can be predicted, according to a group of astrophysicists who see a 50 percent chance of the final countdown ending in 3.7 billion years.

"Time is unlikely to end in our lifetime, but there is a 50 percent chance that time will end within the next 3.7 billion years," according to the team of US and Japanese scientists, who are challenging a long-standing theory of the universe.

While scientists have long concluded that the universe is expanding, and will do so for an infinite period of time, the researchers say the very rules of physics suggest that "an eternally inflating universe" is far from given.

"The point of this paper is to show that certain methods and assumptions that have been widely used by physicists for years -- most prominently, the use of a time cutoff in order to compute probabilities in an eternally inflating universe -- lead to the conclusion that time will end," Raphael Bousso of the University of California, Berkeley told AFP.

"In other words, the time cutoff, which we may have thought was just a calculational tool, actually behaves like a physical event, whether we like it or not," said Bousso, lead author of the study published on arXiv.org

Current theories of the universe begin with the "Big Bang," which cast our living space into being some 13.7 billion years ago in a massive explosion.

Since then, theorists have assumed the universe will simply continue to expand forever, but have also used a theoretical expiration date to help calculate the laws and rules of physics.

But Bousso and his colleagues says the discipline simply cannot have it both ways.

He cautioned however that the complex thought experiment and calculations proposed by the research could not be used to draw definitive conclusions.

"It's very important to understand that we are not saying that we are certain of the conclusion that time will end (though we cannot rule out that it may be correct)," he wrote.

But he said even if the theory was false, discovering why that was the case would help scientists better understand the universe.

"In science, this kind of reasoning is often valuable: you realize that your reasonable-seeming theory predicts something that sounds crazy, so you have to come to grips with that," he told AFP.

"Either you have to abandon the theory, or you have to understand why the crazy-sounding thing may not actually be so crazy."

For astrophysicist Charles Lineweaver, of Australian National University's Mount Stromlo Observatory, Bousso's conclusions are simply incorrect.

"Bousso's average life of a universe is a set time, only because that's what happens when you introduce a cutoff point to get a reasonable probability," he told ABC Television.

"It's a statistical technique being taken probably too seriously," he added.

But Bousso said he and his team had not invented or introduced anything.

"These cutoffs have been used by many leading physicists for years," he told AFP. "We merely pointed out that it's not such an innocent thing to do.

"The cutoff on time is inevitably physical and hence requires a physical justification. It cannot be considered a mere mathematical trick."

Source: http://ph.news.yahoo.com/afp/20101016/tts-science-us-japan-astrophysics-972e412.html

A small asteroid passed within the moon's distance from the Earth on Wednesday morning, and another will do likewise later in the day, space watchers say.

The double encounter is an unusual event that shows the need for closer monitoring of near space for Earth-threatening encounters, according to NASA.

The objects don't pose a threat to Earth, and they will not be visible to the naked eye, said Donald Yeomans, manager of NASA's Near Earth Program, which tracks potentially hazardous asteroids and comets within 28 million miles of Earth.

The objects are visible from Earth as tiny specks of light with the help of moderately sized amateur telescopes, he said.

Near-Earth asteroid 2010 RX30, which is estimated to be 32 to 65 feet in diameter, passed within 154,000 miles of Earth at 5:51 a.m. ET Wednesday, the website PopFi.com confirmed.

The second object, 2010 RF12, estimated to be 20 to 46 feet in diameter, will pass within 49,088 miles of Earth at 5:12 pm ET.

In case you were wondering, that means the two asteroids will pass within 0.6 and 0.2 lunar distances from the Earth, respectively.

Roughly 50 million objects pass through near-Earth space each day, Yeomans said. But what makes this situation noteworthy is that these two asteroids are passing so close to Earth on the same day and that NASA spotted them so far in advance.

"Things like this happen every day that we simply don't know about because we don't have the telescopes large enough to find them or surveys that are looking full-time," he said. "This demonstrates the system's working on some level, but we need larger telescopes and more of them to find objects that are coming this close."

The Catalina Sky Survey near Tucson, Arizona, discovered both objects Sunday morning during a routine monitoring of the skies, NASA said.

The Minor Planet Center in Cambridge, Massachusetts, first received the observations Sunday morning, determined preliminary orbits and concluded both objects would pass within the distance of the moon about three days later.

Yeomans described the discovery as a warning shot in a field of study of low-probability events with global, high-impact consequences. He said that it was only when scientists began looking for near-Earth objects in the 1990s that they realized there was a "problem."

"We have only recently appreciated how many of these objects are in near Earth's space and [it's] best that we keep track of them and find them," he said. "I think this is Mother Nature's way of firing a shot over the bow and warning Earth-based astronomers that we have a lot of work to do."