Tag Archives: SETI

BigBang

Where Are They?

Astrophysics professor Adam Frank reminds us to ponder Enrico Fermi‘s insightful question posed in the middle of the last century. Fermi’s question spawned his infamous, eponymous paradox, and goes something like this:

Why is there no evidence of extraterrestrial civilizations in our Milky Way galaxy given the age of the universe and vast number of stars within it?

Based on simple assumptions and family accurate estimates of the universe’s age, the number of galaxies and stars within it, the probability of Earth-like planets and the development of intelligent life on these planets it should be highly likely that some civilizations have already developed the capability for interstellar travel. In fact, even a slow pace of intra-galactic travel should have led to the colonization of our entire galaxy within just a few tens of millions of years, which is a blink of an eye on a cosmological timescale. Yet we see now evidence on Earth or anywhere beyond. And therein lies the conundrum.

The doomsayers might have us believe that extraterrestrial civilizations have indeed developed numerous times throughout our galaxy. But, none have made the crucial leap beyond ecological catastrophe and technological self-destruction before being able to shirk the bonds of their home planet. Do we have the power to avoid the same fate? I hope so.

From 13.7:

The story begins like this: In 1950, a group of high-powered physicists were lunching together near the Los Alamos National Laboratory.

Among those in attendance were Edward Teller (father of the nuclear bomb) and the Nobel Prize-winning Enrico Fermi. The discussion turned to a spate of recent UFO sightings and, then, on to the possibility of seeing an object (made by aliens) move faster than light. The conversation eventually turned to other topics when, out the blue, Fermi suddenly asked: “Where is everybody?”

While he’d startled his colleagues, they all quickly understood what he was referring to: Where are all the aliens?

What Fermi realized in his burst of insight was simple: If the universe was teeming with intelligent technological civilizations, why hadn’t they already made it to Earth? Indeed, why hadn’t they made it everywhere?

This question, known as “Fermi’s paradox,” is now a staple of astrobiological/SETI thinking. And while it might seem pretty abstract and inconsequential to our day-to-day existence, within Fermi’s paradox there lies a terrible possibility that haunts the fate of humanity.

Enough issues are packed into Fermi’s paradox for more than one post and — since Caleb Scharf and I are just starting a research project related to the question — I am sure to return to it. Today, however, I just want to unpack the basics of Fermi’s paradox and its consequences.

The most important thing to understand about Fermi’s paradox is that you don’t need faster-than-light travel, a warp drive or other exotic technology to take it seriously. Even if a technological civilization built ships that reached only a fraction of the speed of light, we might still expect all the stars (and the planets) to be “colonized.”

For example, let’s imagine that just one high-tech alien species emerges and starts sending ships out at one-hundredth of the speed of light. With that technology, they’d cross the typical distance between stars in “just” a few centuries to a millennium. If, once they got to a new solar system, they began using its resources to build more ships, then we can imagine how a wave of colonization begins propagating across the galaxy.

But how long does it take this colonization wave to spread?

Remarkably, it would only take a fraction of our galaxy’s lifetime before all the stars are inhabited. Depending on what you assume, the propagating wave of colonization could make it from one end of our Milky Way to the other in just 10 million years. While that might seem very long to you, it’s really just a blink of the eye to the 10-billion-year-old Milky Way (in other words, the colonization wave crosses in 0.001 times the age of the galaxy). That means if an alien civilization began at some random moment in the Milky Way’s history, odds are it has had time to colonize the entire galaxy.

You can choose your favorite sci-fi trope for what’s going on with these alien “slow ships.” Maybe they use cryogenic suspension. Maybe they’re using generation ships — mobile worlds whose inhabitants live out entire lives during the millennia-long crossing. Maybe the aliens don’t go themselves but send fully autonomous machines. Whatever scenario you choose, simple calculations, like the one above, tend to imply the aliens should be here already.

Of course, you can also come up with lots of resolutions to Fermi’s paradox. Maybe the aliens don’t want to colonize other worlds. Maybe none of the technologies for the ships described above really work. Maybe, maybe, maybe. We can take up some of those solutions in later 13.7 posts.

For today, however, let’s just consider the one answer that really matters for us, the existential one that is very, very freaky indeed: The aliens aren’t here because they don’t exist. We are the only sentient, technological species that exists in the entire galaxy.

It’s hard to overstate how profound this conclusion would be.

The consequences cut both ways. On the one hand, it’s possible that no other species has ever reached our state of development. Our galaxy with its 300 billion stars — meaning 300 billion chances for self-consciousness — has never awakened anywhere else. We would be the only ones looking into the night sky and asking questions. How impossibly lonely that would be.

Read the entire article here.

 

BigBang

Active SETI

google-search-aliens

Seventy years after the SETI (Search for Extra-Terrestrial Intelligence) experiment began some astronomers are thinking of SETI 2.0 or active SETI. Rather than just passively listening for alien-made signals emanating from the far distant exoplanets these astronomers wish to take the work a bold step further. They’re planning to transmit messages in the hope that someone or something will be listening. And that has opponents of the plan rather worried. If somethings do hear us, will they come looking, and if so, then what? Will the process result in a real-life The Day the Earth Stood Still or Alien? And, more importantly, will they all look astonishingly Hollywood-like?

From BBC:

Scientists at a US conference have said it is time to try actively to contact intelligent life on other worlds.

Researchers involved in the search for extra-terrestrial life are considering what the message from Earth should be.

The call was made by the Search for Extra Terrestrial Intelligence institute at a meeting of the American Association for the Advancement of Science in San Jose.

But others argued that making our presence known might be dangerous.

Researchers at the Seti institute have been listening for signals from outer space for more than 30 years using radio telescope facilities in the US. So far there has been no sign of ET.

The organisation’s director, Dr Seth Shostak, told attendees to the AAAS meeting that it was now time to step up the search.

“Some of us at the institute are interested in ‘active Seti’, not just listening but broadcasting something to some nearby stars because maybe there is some chance that if you wake somebody up you’ll get a response,” he told BBC News.

The concerns are obvious, but sitting in his office at the institute in Mountain View, California, in the heart of Silicon Valley, he expresses them with characteristic, impish glee.

Game over?

“A lot of people are against active Seti because it is dangerous. It is like shouting in the jungle. You don’t know what is out there; you better not do it. If you incite the aliens to obliterate the planet, you wouldn’t want that on your tombstone, right?”

I couldn’t argue with that. But initially, I could scarcely believe I was having this conversation at a serious research institute rather than at a science fiction convention. The sci-fi feel of our talk was underlined by the toy figures of bug-eyed aliens that cheerfully decorate the office.

But Dr Shostak is a credible and popular figure and has been invited to present his arguments.

Leading astronomers, anthropologists and social scientists will gather at his institute after the AAAS meeting for a symposium to flesh out plans for a proposal for active Seti to put to the public and politicians.

High on the agenda is whether such a move would, as he put it so starkly, lead to the “obliteration” of the planet.

“I don’t see why the aliens would have any incentive to do that,” Dr Shostak tells me.

“Beyond that, we have been telling them willy-nilly that we are here for 70 years now. They are not very interesting messages but the early TV broadcasts, the early radio, the radar from the Second World War – all that has leaked off the Earth.

“Any society that could come here and ruin our whole day by incinerating the planet already knows we are here.”

Read the entire article here.

Image courtesy of Google Search.

BigBang

Revisiting Drake

In 1960 radio astronomer Frank Drake began the first systematic search for intelligent signals emanating from space. He was not successful, but his pioneering efforts paved the way for numerous other programs, including SETI (Search for Extra-Terrestrial Intelligence). The Drake Equation is named for him, and put simply, gives an estimate of the number of active, extraterrestrial civilizations with methods of communication in our own galaxy. Drake postulated the equation as a way to get the scientific community engaged in the search for life beyond our home planet.

The Drake equation is:

N = R^{\ast} \cdot f_p \cdot n_e \cdot f_{\ell} \cdot f_i \cdot f_c \cdot L

where:

N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone); and

R* = the average number of star formation per year in our galaxy

fp = the fraction of those stars that have planets

ne = the average number of planets that can potentially support life per star that has planets

fl = the fraction of planets that could support life that actually develop life at some point

fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)

fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L = the length of time for which such civilizations release detectable signals into space

Now, based on recent discoveries of hundreds of extra-solar planets, or exoplanets (those beyond our solar system), by the Kepler space telescope and other Earth-bound observatories, researchers are fine-tuning the original Drake Equation for the 21st century.

From the New Scientist:

An iconic tool in the search for extraterrestrial life is getting a 21st-century reboot – just as our best planet-hunting telescope seems to have died. Though the loss of NASA’s Kepler telescope is a blow, the reboot could mean we find signs of life on extrasolar planets within a decade.

The new tool takes the form of an equation. In 1961 astronomer Frank Drake scribbled his now-famous equation for calculating the number of detectable civilisations in the Milky Way. The Drake equation includes a number of terms that at the time seemed unknowable – including the very existence of planets beyond our solar system.

But the past two decades have seen exoplanets pop up like weeds, particularly in the last few years thanks in large part to the Kepler space telescope. Launched in 2009Movie Camera, Kepler has found more than 130 worlds and detected 3000 or so more possibles. The bounty has given astronomers the first proper census of planets in one region of our galaxy, allowing us to make estimates of the total population of life-friendly worlds across the Milky Way.

With that kind of data in hand, Sara Seager at the Massachusetts Institute of Technology reckons the Drake equation is ripe for a revamp. Her version narrows a few of the original terms to account for our new best bets of finding life, based in part on what Kepler has revealed. If the original Drake equation was a hatchet, the new Seager equation is a scalpel.

Seager presented her work this week at a conference in Cambridge, Massachusetts, entitled “Exoplanets in the Post-Kepler Era”. The timing could not be more prescient. Last week Kepler suffered a surprise hardware failure that knocked out its ability to see planetary signals clearly. If it can’t be fixed, the mission is over.

“When we talked about the post-Kepler era, we thought that would be three to four years from now,” co-organiser David Charbonneau of the Harvard-Smithsonian Center for Astrophysics said last week. “We now know the post-Kepler era probably started two days ago.”

But Kepler has collected data for four years, slightly longer than the mission’s original goal, and so far only the first 18 months’ worth have been analysed. That means it may have already gathered enough information to give alien-hunters a fighting chance.

The original Drake equation includes seven terms, which multiplied together give the number of intelligent alien civilisations we could hope to detect (see diagram). Kepler was supposed to pin down two terms: the fraction of stars that have planets, and the number of those planets that are habitable.

To do that, Kepler had been staring unflinchingly at some 150,000 stars near the constellation Cygnus, looking for periodic changes in brightness caused by a planet crossing, or transiting, a star’s face as seen from Earth. This method tells us a planet’s size and its rough distance from its host star.

Size gives a clue to a planet’s composition, which tells us whether it is rocky like Earth or gassy like Neptune. Before Kepler, only a few exoplanets had been identified as small enough to be rocky, because other search methods were better suited to spotting larger, gas giant worlds.

“Kepler is the single most revolutionary project that has ever been undertaken in exoplanets,” says Charbonneau. “It broke open the piggybank and rocky planets poured out.” A planet’s distance from its star is also crucial, because that tells us whether the temperature is right for liquid water – and so perhaps life – to exist.

But with Kepler’s recent woes, hopes of finding enough potentially habitable planets, or Earth twins, to satisfy the Drake equation have dimmed. The mission was supposed to run for three-and-a-half years, which should have been enough to pinpoint Earth-sized planets with years of a similar length. After the telescope came online, the mission team realised that other sun-like stars are more active than ours, and they bounce around too much in the telescope’s field of view. To find enough Earths, they would need seven or eight years of data.

Read the entire article here.

Image courtesy of the BBC. Drake Equation courtesy of Wikipedia.

BigBang

Looking for Alien Engineering Work

We haven’t yet found any aliens inhabiting exoplanets orbiting distant stars. We haven’t received any intelligently manufactured radio signals from deep space. And, unless you subscribe to the conspiracy theories surrounding Roswell Area 51, it’s unlikely that we’ve been visited by an extra-terrestrial intelligence.

Most reasonable calculations suggest that the universe should be teeming with life beyond our small, blue planet. So, where are all the aliens and why haven’t we been contacted yet? Not content to wait, some astronomers believe we should be looking for evidence of distant alien engineering projects.

From the New Scientist:

ALIENS: where are you? Our hopes of finding intelligent companionship seem to be constantly receding. Mars and Venus are not the richly populated realms we once guessed at. The icy seas of the outer solar system may hold life, but almost certainly no more than microbes. And the search for radio signals from more distant extraterrestrials has so frustrated some astronomers that they are suggesting we shout out an interstellar “Hello”, in the hope of prodding the dozy creatures into a response.

So maybe we need to think along different lines. Rather than trying to intercept alien communications, perhaps we should go looking for alien artefacts.

There have already been a handful of small-scale searches, but now three teams of astronomers are setting out to scan a much greater volume of space (see diagram). Two groups hope to see the shadows of alien industry in fluctuating starlight. The third, like archaeologists sifting through a midden heap on Earth, is hunting for alien waste.

What they’re after is something rather grander than flint arrowheads or shards of pottery. Something big. Planet-sized power stations. Star-girdling rings or spheres. Computers the size of a solar system. Perhaps even an assembly of hardware so vast it can darken an entire galaxy.

It might seem crazy to even entertain the notion of such stupendous celestial edifices, let alone go and look for them. Yet there is a simple rationale. Unless tool-users are always doomed to destroy themselves, any civilisation out there is likely to be far older and far more advanced than ours.

Humanity has already covered vast areas of Earth’s surface with roads and cities, and begun sending probes to other planets. If we can do all this in a matter of centuries, what could more advanced civilisations do over many thousands or even millions of years?

In 1960, the physicist Freeman Dyson pointed out that if alien civilisations keep growing and expanding, they will inevitably consume ever more energy – and the biggest source of energy in any star system is the star itself. Our total power consumption today is equivalent to about 0.01 per cent of the sunlight falling on Earth, so solar power could easily supply all our needs. If energy demand keeps growing at 1 per cent a year, however, then in 1000 years we’d need more energy than strikes the surface of the planet. Other energy sources, such as nuclear fusion, cannot solve the problem because the waste heat would fry the planet.

In a similar position, alien civilisations could start building solar power plants, factories and even habitats in space. With material mined from asteroids, then planets, and perhaps even the star itself, they could really spread out. Dyson’s conclusion was that after thousands or millions of years, the star might be entirely surrounded by a vast artificial sphere of solar panels.

The scale of a Dyson sphere is almost unimaginable. A sphere with a radius similar to that of Earth’s orbit would have more than a hundred million times the surface area of Earth. Nobody thinks building it would be easy. A single shell is almost certainly out, as it would be under extraordinary stresses and gravitationally unstable. A more plausible option is a swarm: many huge power stations on orbits that do not intersect, effectively surrounding the star. Dyson himself does not like to speculate on the details, or on the likelihood of a sphere being built. “We have no way of judging,” he says. The crucial point is that if any aliens have built Dyson spheres, there is a chance we could spot them.

A sphere would block the sun’s light, making it invisible to our eyes, but the sphere would still emit waste heat in the form of infrared radiation. So, as Carl Sagan pointed out in 1966, if infrared telescopes spot a warm object but nothing shows up at visible wavelengths, it could be a Dyson sphere.

Some natural objects can produce the same effect. Very young and very old stars are often surrounded by dust and gas, which blocks their light and radiates infrared. But the infrared spectrum of these objects should be a giveaway. Silicate minerals in dust produce a distinctive broad peak in the spectrum, and molecules in a warm gas would produce bright or dark spectral lines at specific wavelengths. By contrast, waste heat from a sphere should have a smooth, featureless thermal spectrum. “We would be hoping that the spectrum looks boring,” says Matt Povich at the California State Polytechnic University in Pomona. “The more boring the better.”

Our first good view of the sky at the appropriate wavelengths came when the Infrared Astronomical Satellite surveyed the skies for 10 months in 1983, and a few astronomers have sifted through its data. Vyacheslav Slysh at the Space Research Institute in Moscow made the first attempt in 1985, and Richard Carrigan at Fermilab in Illinois published the latest search in 2009. “I wanted to get into the mode of the British Museum, to go and look for artefacts,” he says.

Carrigan found no persuasive sources, but the range of his search was limited. It would have detected spheres around sunlike stars only within 1000 light years of Earth. This is a very small part of the Milky Way, which is 100,000 light years across.

One reason few have joined Carrigan in the hunt for artefacts is the difficulty of getting funding for such projects. Then last year, the Templeton Foundation – an organisation set up by a billionaire to fund research into the “big questions” – invited proposals for its New Frontiers programme, specifically requesting research that would not normally be funded because of its speculative nature. A few astronomers jumped at the chance to look for alien contraptions and, in October, the programme approved three separate searches. The grants are just a couple of hundred thousand dollars each, but they do not have to fund new telescopes, only new analysis.

One team, led by Jason Wright at Pennsylvania State University in University Park, will look for the waste heat of Dyson spheres by analysing data from two space-based infrared observatories, the Wide-field Infrared Survey Explorer (WISE) and the Spitzer space telescope, launched in 2009 and 2003. Povich, a member of this team, is looking specifically within the Milky Way. Thanks to the data from Spitzer and WISE, Povich should be able to scan a volume of space thousands of times larger than previous searches like Carrigan’s. “For example, if you had a sun-equivalent star, fully enclosed in a Dyson sphere, we should be able to detect it almost anywhere in the galaxy.”

Even such a wide-ranging hunt may not be ambitious enough, according to Wright. He suspects that interstellar travel will prove no harder than constructing a sphere. An alien civilisation with such a high level of technology would spread out and colonise the galaxy in a few million years, building spheres as they go. “I would argue that it’s very hard for a spacefaring civilisation to die out. There are too many lifeboats,” says Wright. “Once you have self-sufficient colonies, you will take over the galaxy – you can’t even try to stop it because you can’t coordinate the actions of the colonies.”

If this had happened in the Milky Way, there should be spheres everywhere. “To find one or a few Dyson spheres in our galaxy would be very strange,” says Wright.

Read the entire article after the jump.

Image: 2001: A Space Odyssey, The Monolith. Courtesy of Daily Galaxy.