(page 1 of 3)
Excerpt from wired.com
In the hunt for extraterrestrial life, scientists started by searching for a world orbiting a star just like the sun. After all, the steady warmth of that glowing yellow ball in the sky makes life on Earth possible.But as astronomers continue to discover thousands of planets, they’re realizing that if (or when) we find signs of extraterrestrial life, chances are good that those aliens will orbit a star quite different from the sun—one that’s redder, cooler, and at a fraction of the sun’s size and mass. So in the quest for otherworldly life, many astronomers have set their sights on these small stars, known as red dwarfs or M dwarfs.
At first, planet-hunting astronomers didn’t care so much about M dwarfs. After the first planet outside the solar system was discovered in 1995, scientists began hunting for a true Earth twin: a rocky planet like Earth with an orbit like ours around a sun-like star. Indeed, the search for that kind of system drove astronomers through most of the 2000s, says astronomer Phil Muirhead of Boston University.
But then astronomers realized that it might be technically easier to find planets around M dwarfs. Detecting another planet is really hard, and scientists rely on two main methods. In the first, they look for a drop in a star’s brightness when a planet passes in front of it. In the second, astronomers measure the slight wobble of a star, caused by the gentle gravitational tug of an orbiting planet. With both of these techniques, the signal is stronger and easier to detect for a planet orbiting an M dwarf. A planet around an M dwarf also orbits more frequently, increasing the chances that astronomers will spot it.
M dwarfs got a big boost from the Kepler space telescope, which launched in 2008. By staring at small patch of the sky, the telescope searches for suddenly dimming stars when a planet passes in front of them. In doing so, the spacecraft discovered a glut of planets—more than 1,000 at the latest count—it found a lot of planets around M dwarfs. “Kepler changed everything,” Muirhead said. Because M-dwarf systems are easier to find, the bounty of such planets is at least partly due to a selection effect. But, as Muirhead points out, Kepler is also designed to find Earth-sized planets around sun-like stars, and the numbers so far suggest that M-dwarfs may offer the best odds for finding life.
“By sheer luck you would be more likely to find a potentially habitable planet around an M dwarf than a star like the sun,” said astronomer Courtney Dressing of Harvard. She led an analysis to estimate how many Earth-sized planets—which she defined as those with radii ranging from one to one-and-a-half times Earth’s radius—orbit M dwarfs in the habitable zone, the region around the star where liquid water can exist on the planet’s surface. According to her latest calculations, one in four M dwarfs hosts such a planet.
That’s higher than the estimated number of Earth-sized planets around a sun-like star, she says. For example, an analysis by astronomer Erik Petigura of UC Berkeley suggests that fewer than 10 percent of sun-like stars have a planet with a radius between one and two times that of Earth’s.
M dwarfs have another thing going for them. They’re the most common star in the galaxy, comprising an estimated 75 percent of the Milky Way’s hundreds of billions of stars. If Dressing’s estimates are right, then our galaxy could be teeming with 100 billion Earth-sized planets in their stars’ habitable zones. This illustration shows Kepler-186f, the first rocky planet found in a star’s habitable zone. Its star is an M dwarf. NASA Ames/SETI Institute/JPL-Caltech
To be sure, these estimates have lots of limitations. They depend on what you mean by the habitable zone, which isn’t well defined. Generally, the habitable zone is where it’s not too hot or too cold for liquid water to exist. But there are countless considerations, such as how well a planet’s atmosphere can retain water. With a more generous definition that widens the habitable zone, Petigura’s numbers for Earth-sized planets around a sun-like star go up to 22 percent or more. Likewise, Dressing’s numbers could also go up.
Astronomers were initially skeptical of M-dwarf systems because they thought a planet couldn’t be habitable near this kind of star. For one, M dwarfs are more active, especially during within the first billion years of its life. They may bombard a planet with life-killing ultraviolet radiation. They can spew powerful stellar flares that would strip a planet of its atmosphere.
And because a planet will tend to orbit close to an M dwarf, the star’s gravity can alter the planet’s rotation around its axis. When such a planet is tidally locked, as such a scenario is called, part of the planet may see eternal daylight while another part sees eternal night. The bright side would be fried while the dark side would freeze—hardly a hospitable situation for life.
But none of these are settled issues, and some studies suggest they may not be as big of a problem as previously thought, says astronomer Aomawa Shields of UCLA. For example, habitability may depend on specific types and frequency of flares, which aren’t well understood yet. Computer models have also shown that an atmosphere can help distribute heat, preventing the dark side of a planet from freezing over.
news.nationalpost.com Humanity may have already created its own nemesis, Professor Stephen Hawking warned last week. The Cambridge University physicist claimed that new developments in the field of artificial intelligence (AI) mean that within a few decades, computers thousands of times more powerful than in existence today may decide to usurp their creators and effectively end humanity’s 100,000-year dominance of Earth.This Terminator scenario is taken seriously by many scientists and technologists. Before Prof. Hawking made his remarks, Elon Musk, the genius behind the Tesla electric car and PayPal, had stated that “with artificial intelligence, we are summoning the demon,” comparing it unfavourably with nuclear war as the most potent threat to humanity’s existence.Aside from the rise of the machines, many potential threats have been identified to our species, our civilization, even our planet. To keep you awake at night, here are seven of the most plausible. 1. ASTEROID STRIKEOur solar system is littered with billions of pieces of debris, from the size of large boulders to objects hundreds of kilometres across. We know that, from time to time, these hit the Earth. Sixty-five-million years ago, an object – possibly a comet a few times larger than the one on which the Philae probe landed last month – hit the Mexican coast and triggered a global winter that wiped out the dinosaurs. In 1908, a smaller object hit a remote part of Siberia and devastated hundreds of square kilometres of forest. Last week, 100 scientists, including Lord Rees of Ludlow, the Astronomer Royal, called for the creation of a global warning system to alert us if a killer rock is on the way.Probability: remote in our lifetime, but one day we will be hit.Result: there has been no strike big enough to wipe out all life on Earth – an “extinction-level event” – for at least three billion years. But a dino-killer would certainly be the end of our civilization and possibly our species.
Getty Images / ThinkStockAn artist's depiction of an asteroid approaching Earth.
2. ARTIFICIAL INTELLIGENCEProf. Hawking is not worried about armies of autonomous drones taking over the world, but something more subtle – and more sinister. Some technologists believe that an event they call the Singularity is only a few decades away. This is a point at which the combined networked computing power of the world’s AI systems begins a massive, runaway increase in capability – an explosion in machine intelligence. By then, we will probably have handed over control to most of our vital systems, from food distribution networks to power plants, sewage and water treatment works, and the global banking system. The machines could bring us to our knees without a shot being fired. And we cannot simply pull the plug, because they control the power supplies.
Warner Bros.When artificial intelligence becomes self-aware, there is a chance it will look something like this scene from Terminator 3.
Probability: unknown, although computing power is doubling every 18 months. We do not know if machines can be conscious or “want” to do anything, and sceptics point out that the cleverest computers in existence are currently no brighter than cockroaches.Result: if the web wakes up and wants to sweep us aside, we may have a fight on our hands (perhaps even something similar to the man vs. machines battle in the Terminator films). But it is unlikely that the machines will want to destroy the planet – they “live” here, too.
3. A GENETICALLY CREATED PLAGUEThis is possibly the most terrifying short-term threat because it is so plausible. The reason Ebola has not become a worldwide plague – and will not do so – is because it is so hard to transmit, and because it incapacitates and kills its victims so quickly. However, a modified version of the disease that can be transmitted through the air, or which allows its host to travel around for weeks, symptom-free, could kill many millions. It is unknown whether any terror group has the knowledge or facilities to do something like this, but it is chilling to realize that the main reason we understand Ebola so well is that its potential to be weaponized was quickly realized by defence experts.Probability: someone will probably try it one day.Result: potentially catastrophic. “Ordinary” infectious diseases such as avian-flu strains have the capability to wipe out hundreds of millions of people.
Handout/AFP/Getty ImagesLaboratory technicians and physicians work on samples during research on the evolving Ebola disease in bats, at the Center for Emerging and Zoonotic Diseases research Laboratory of the National Institute for Communicable Diseases in Pretoria on Nov. 21, 2011.
4. NUCLEAR WARThis is still the most plausible “doomsday” scenario. Despite arms-limitations treaties, there are more than 15,000 nuclear warheads and bombs in existence – many more, in theory, than would be required to kill every human on Earth. Even a small nuclear war has the potential to cause widespread devastation. In 2011, a study by NASA scientists concluded that a limited atomic war between India and Pakistan involving just 100 Hiroshima-sized detonations would throw enough dust into the air to cause temperatures to drop more than 1.2C globally for a decade.Probability: high. Nine states have nuclear weapons, and more want to join the club. The nuclear wannabes are not paragons of democracy.Result: it is unlikely that even a global nuclear war between Russia and NATO would wipe us all out, but it would kill billions and wreck the world economy for a century. A regional war, we now know, could have effects far beyond the borders of the conflict.
AP Photo/U.S. Army via Hiroshima Peace Memorial MuseumA mushroom cloud billows about one hour after a nuclear bomb was detonated above Hiroshima, Japan Aug. 6, 1945.
5. PARTICLE ACCELERATOR DISASTERBefore the Large Hadron Collider (LHC), the massive machine at CERN in Switzerland that detected the Higgs boson a couple of years ago, was switched on, there was a legal challenge from a German scientist called Otto Rossler, who claimed the atom-smasher could theoretically create a small black hole by mistake – which would then go on to eat the Earth.The claim was absurd: the collisions in the LHC are far less energetic than those caused naturally by cosmic rays hitting the planet. But it is possible that, one day, a souped-up version of the LHC could create something that destroys the Earth – or even the universe – at the speed of light.Probability: very low indeed.Result: potentially devastating, but don’t bother cancelling the house insurance just yet.
CERN)/MCTThis is one of the huge particle detectors in the Large Hadron Collider, a 17 mile-long tunnel under the French-Swiss border. Scientists are searching for evidence of what happened right after- and perhaps before- the Big Bang.
6. ‘GOD’ REACHES FOR THE OFF-SWITCHMany scientists have pointed out that there is something fishy about our universe. The physical constants – the numbers governing the fundamental forces and masses of nature – seem fine-tuned to allow life of some form to exist. The great physicist Sir Fred Hoyle once wondered if the universe might be a “put-up job”.More recently, the Oxford University philosopher Nick Bostrom has speculated that our universe may be one of countless “simulations” running in some alien computer, much like a computer game. If so, we have to hope that the beings behind our fake universe are benign – and do not reach for the off-button should we start misbehaving.Probability: according to Professor Bostrom’s calculations, if certain assumptions are made, there is a greater than 50% chance that our universe is not real. And the increasingly puzzling absence of any evidence of alien life may be indirect evidence that the universe is not what it seems.Result: catastrophic, if the gamers turn against us. The only consolation is the knowledge that there is absolutely nothing we can do about it.
AP Photo/Oculus Rift/FoxThis photo shows a scene fromX-Men: Days of Future Past virtual reality experience. Oxford University philosopher Nick Bostrom has speculated that our universe may be one of countless "simulations" running in some alien computer, much like a computer game.
7. CLIMATE CATASTROPHEAlmost no serious scientists now doubt that human carbon emissions are having an effect on the planet’s climate. The latest report by the Intergovernmental Panel on Climate Change suggested that containing temperature rises to below 2C above the pre-industrial average is now unlikely, and that we face a future three or four degrees warmer than today.This will not literally be the end of the world – but humanity will need all the resources at its disposal to cope with such a dramatic shift. Unfortunately, the effects of climate change will really start to kick in just at the point when the human population is expected to peak – at about nine billion by the middle of this century. Millions of people, mostly poor, face losing their homes to sea-level rises (by up to a metre or more by 2100) and shifting weather patterns may disrupt agriculture dramatically.Probability: it is now almost certain that CO2 levels will keep rising to 600 parts per billion and beyond. It is equally certain that the climate will respond accordingly.Result: catastrophic in some places, less so in others (including northern Europe, where temperature rises will be moderated by the Atlantic). The good news is that, unlike with most of the disasters here, we have a chance to do something about climate change now.
AP Photo/Charles Rex ArbogastFloodwaters from the Souris River surround homes near Minot State University in Minot, N.D. on June 27, 2011. Global warming is rapidly turning America the beautiful into America the stormy and dangerous, according to the National Climate Assessment report released Tuesday, May 6, 2014.