Where are all the aliens? We fight and fight as we do

If the galaxy is a two-day event and it took only a few decades to visit the moon and launch space stations, why had not it landed a foreign spacecraft on the White House lawn?

We must be the only recruits in the cosmic neighborhood, as many astrophysicists have proposed for decades. But a new analysis by a team led by the astrophysicist of the University of Rochester Adam Frank suggests a more sophisticated analysis of the old paradox. Scanning the galaxy road and establishing a unified galactic empire may be inevitable for a monolithic super-culture, but most cultures are neither monolithic nor exaggerated – at least if our experience is any guide. Spacecraft collapses. Overactive stars bake differently the desired targets. Economic crises and government decommissioning kill island ships before they begin.

Using a mixture of theory and simulation published last week in the arXiv paper database, under peer review, Frank and his colleagues explore the essential middle ground between a barren and full-filled galaxy where some cultures can succeed many constellations without creating a spatial and temporal strangulation across the entire Milky Way.

Astronomers have just begun to search for stars for tech signs (so-called technical signature), so few feel frustrated by the silence so far (a common quip confesses that it now bets the aliens to come to the conclusion that dolphins do not exist after scanning a value of a lake of ocean water). What maintains optimistic in the evening is the argument originally developed in 1975.

Even with the snail's rhythm, the thought is that the galaxy is so old that any technology species should have had enough time to radiate to every galaxy star. However, we do not see data from old or present foreign cities here on Earth – a remark called "Fact A." Academics have poured buckets of ink trying to solve this puzzle, known as the paradox Fermi, with explanations ranging from humanity placed in a retention, to all others waiting for hibernation for a universe that will cooler computers better their.

Many of these solutions are based on speculation about how aliens behave, who never sat well with Frank: "One of the things we always broke when people talked about the paradox Fermi was that there was always such a fantastic out -sociology".

Instead, Frank and his colleagues created the most comprehensive model in an effort to get rid of the imagination from science and answer a question: Of all the possible galaxies that we could live, what are the elements consistent with Real A?

Some possibilities make this analysis separate. For one, the researchers included in their simulations the fact that the stars are actually approaching. "Even if you do not have a ship, you are traveling freely in the galaxy," says Jason Wright, co-author and astronomer at Penn State University. "Every 100,000 years around a new star is the closest one so you can get to it."

The team estimated that for a civilization that uses ships a few tens to thousands of times as vintage Voyager detectors, the drifting stars shorten the time it would take to spread across the galaxy in a few hundred million years. In other words, if you compress the existence of a galaxy in a calendar year, anyone starting ships by January 7 could reach every astral system by January 14th. Now, on December 31st, it's definitely too late.

This quick transit time deepened the mystery of Real A, until the researchers added two more real-world checks. First, as Frank says, good planets can be hard to find. Some stars have no planets. Many planets may not suit your needs. Or, your dream planet may already be occupied.

Second, no single habitat can endure forever, as humanity realizes quickly. Spreading to other stars may extend the overall life of the culture, but once a new settlement is born, its days are numbered. It can last for hundreds of thousands or millions of years, but at some point a disaster will almost certainly take it out.

Taking into account a range of living lives, fractions of suitable planets, return times between spurts and other factors, the team calculated how much of the galaxy would end up in billions of potential galaxy stories and found three broad categories. The first two represent common sense solutions to Fermi Paradox: If good planets are abundant and survival is easy, the galaxy will have to overflow with life. If the opposite is true, nobody gets too far.

Many of their simulations, however, fell into a third category – a Galaxy that remains partially established indefinitely. Accelerating the galaxy in fast waves can be easy, but managing this territory is then impossible. The settlements are dying, drifting, and huge spaces return to their uninhabited. Some migrate, others do not.

"You can end up with this loose network of settlements," says Wright, "where the overall galaxy is arranged, but a given star at any given time may not be."

We can be found in one of the zones that have remained untouched for at least millions of years (writers point out that if the Earth hosted a settlement deep in its geological past, no sign would remain today). If this happens, F does not need any explanation.

Some still prefer other ways of resolving Fermi's paradox, such as Anders Sandberg, a researcher at Oxford's Institute of the Future of Humanity in England, who suggests life may be just rare. He would like to see Frank's simulations expand to cover a wider range of possibilities. "It's a great model," Sandberg writes in an e-mail, "but the writers limit themselves to a fairly narrow corner of the space."

Astronomer Jill Tarter, whose work inspired the novel by Carl Sagan Communication, praised the team's ability, but questioned how far the theoretical analyzes can reach. "They are smart folks and probably got the right math," he writes in an e-mail, "What this means in the absence of data."

The authors agree that no amount of theory can replace the actual research but says that this analysis strengthens their optimism that technological life could exist in our galaxy and their belief that the astronomical community should seek it. Frank underlines the explosion of known planetary systems, with about 4,000 exoplanets discovered since 1992, and looks to researchers who develop the ability to study these worlds in detail.

"We will look at these atmospheres and find out if they have oxygen and methane," says Frank, "and we can go through a technical signature. For the first time in millennia, protesting for life on other planets, we live in a time when we really have data. "