Fast Radio Bursts from Extragalactic Light Sails

Manasvi Lingam, Abraham Loeb
We examine the possibility that Fast Radio Bursts (FRBs) originate from the activity of extragalactic civilizations.
Our analysis shows that beams used for powering large light sails could yield parameters that are consistent with FRBs.
The characteristic diameter of the beam emitter is estimated through a combination of energetic and engineering constraints, and both approaches intriguingly yield a similar result which is on the scale of a large rocky planet.
Moreover, the optimal frequency for powering the light sail is shown to be similar to the detected FRB frequencies. These `coincidences’ lend some credence to the possibility that FRBs might be artificial in origin.
Other relevant quantities, such as the characteristic mass of the light sail, and the angular velocity of the beam, are also derived.
By using the FRB occurrence rate, we infer upper bounds on the rate of FRBs from extragalactic civilizations in a typical galaxy.
The possibility of detecting fainter signals is briefly discussed, and the wait time for an exceptionally bright FRB event in the Milky Way is estimated.
Read more at https://arxiv.org/pdf/1701.01109.pdf

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Aside

Type III Societies (Apparently) Do Not Exist

Brian C. Lacki
Whether technological societies remain small and planet-bound like our own, or ultimately span across galaxies is an open question in the Search for Extraterrestrial Intelligence. Societies that engineer on a galactic scale are classified as Type III on Kardashev’s scale. I argue that Type III societies can take the form of blackboxes, entire galaxies veiled in an opaque screen. A blackbox has a temperature that is just above that of the cosmic microwave background. The screen can be made from artificial dust pervading the galaxy.
I show that there is enough material in galaxies to build blackboxes if the dust is fashioned into dipole antennas. The thermal emission of a blackbox makes it a bright microwave source. I examine the Planck Catalog of Compact Sources to constrain the abundance of blackboxes. None of the 100 GHz sources has the spectrum expected of a blackbox. The null result rules out shrouded galaxy clusters out to z ~ 1 and shrouded Milky Ways out to (comoving) 700 Mpc. The reach of the results includes 3 million galaxies containing an estimated 300 quadrillion terrestrial planets, as well as tens of thousands of galaxy clusters.
Combined with the null results from other searches for Type III societies, I conclude that they are so rare that they basically do not exist within the observable Universe. A hypothesis of “Cosmic Pessimism” is discussed, in which we are alone, our long-term chances for survival are slim, and if we do survive, our future history will be checkered. Our loneliness is suggested by the lack of Type III societies.
I discuss the remaining forms of Type III societies not yet well constrained by observation. I argue that the ease of building blackboxes on planetary and Solar System scales may lead, within a few centuries, to environmental catastrophes vastly more devastating than anything we are doing now, boding ill for us.
Read more at http://arxiv.org/pdf/1604.07844v1.pdf

The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies

I.  Background and Justification

J. T. Wright, B. Mullan, S. Sigurðsson, M. S. Povich

We motivate the Ĝ infrared search for extraterrestrial civilizations with large energy supplies.
We discuss some philosophical difficulties of SETI, and how communication SETI circumvents them.
We review “Dysonian SETI”, the search for artifacts of alien civilizations, and find that it is highly complementary to traditional communication SETI; the two together might succeed where either one, alone, has not.
We discuss the argument of Hart (1975) that spacefaring life in the Milky Way should be either galaxy-spanning or non-existent, and examine a portion of his argument that we dub the “monocultural fallacy”.
We discuss some rebuttals to Hart that invoke sustainability and predict long Galaxy colonization timescales.
We find that the maximum Galaxy colonization timescale is actually much shorter than previous work has found (109 yr), and that many “sustainability” counter-arguments to Hart’s thesis suffer from the monocultural fallacy.
We extend Hart’s argument to alien energy supplies, and argue that detectably large energy supplies can plausibly be expected to exist because life has potential for exponential growth until checked by resource or other limitations, and intelligence implies the ability to overcome such limitations.
As such, if Hart’s thesis is correct then searches for large alien civilizations in other galaxies may be fruitful; if it is incorrect, then searches for civilizations within the Milky Way are more likely to succeed than Hart argued. We review some past Dysonian SETI efforts, and discuss the promise of new mid-infrared surveys, such as that of WISE…
… Read more at http://arxiv.org/pdf/1408.1133v1.pdf

Scientists could find alien life within 40 years

… says royal astronomer

The Queen’s astronomer Martin Rees Photo: Jay Williams

Martin Rees, former president of the Royal Society, said evidence of whether beings exist not only beyond earth but beyond our solar system, could be found in that time, a newspaper reported.
Lord Rees said he believed that astro-physicists could be able to view images of distant planets outside the solar system as soon as 2025. This could potentially lead to the discovery of some form of life on them.
When asked what changes could be expected in science in the next 40 years, he said understanding more about the “origin of life, the place where it exists, and whether aliens exist, is going to be crucial”, the Daily Mail reported.
The astronomer was speaking at the launch of Professor Stephen Hawking’s new series Grand Design, due to begin next Thursday on the Discovery Channel.
Lord Rees, who has been Astronomer Royal – a senior position within the Royal Household offering advice to the Queen on astronomical matters – since 1995, said: “Within 10 or 20 years we will be able to image other planets like the earth, orbiting other stars.
“That will be a really exciting subject to see if there is evidence for [extra-terrestrial] life or not.”
However it was suggested earlier this year that rather more earthbound concerns may hold such research back.
It emerged in June that astronomers scanning the universe for signs of extra-terrestrial activity were facing a financial crisis that threatened to stall the 52-year search for intelligent life beyond Earth.
The respected SETI Institute in California will be forced to curtail radio telescope operations, which search space for signals from other worlds, unless it can plug a multi-million dollar funding gap.
Read more: telegraph.co.uk

A Career Waiting for E.T. to Phone

Elwood H. Smith – Copyright 2012 The New York Times Company

By DENNIS OVERBYE

Jill Tarter once complained to me that she had no poetry in her soul.

It was 1990, and NASA was getting ready to undertake a survey of the 1,000 nearest stars, looking for radio signals from aliens. Dr. Tarter, then 46 and a researcher at NASA’s Ames Research Center in Mountain View, Calif., was in charge of it.

“I can’t say what they will be like,” she sighed, when asked to speculate about the nature and motives of these putative aliens.

She was far too busy worrying about how to recognize a signal, not to mention how to avoid being fooled by the kid next door or a stray weather or spy satellite.

For some three decades, Dr. Tarter, now 68, has been the person most likely to be the first to know if we make contact with E.T. — the one who will sound the alarm, spreading the news that We Are Not Alone.

Now Dr. Tarter is stepping away from the radio telescope, retiring from her post as the director of the Center for SETI Research at the SETI Institute in Mountain View. SETI, of course, refers to the search for intelligent life in the universe.

“The SETI Institute has a good pension plan — we’re grown-ups,” she said by telephone recently.

There will be a dinner and speeches in her honor at SETIcon, a gathering of astronomers, astronauts and science-fiction fans in Santa Clara this weekend.

“I hope it’s not a roast,” she said.

Dr. Tarter never did get to deliver the news that we have company. But this, she contends, is not disappointing. What would be disappointing is if humans were not able to search for their neighbors at all.

Over the decades she has brooked few distractions from that quest.

When a reporter (O.K., it was me) once described Dr. Tarter’s blond hair tied with a pink ribbon into a ponytail, she cut her hair short.

When the SETI researchers got a new radio telescope for their search — the Allen Array, at the University of California’s Hat Creek Observatory in Northern California — she got a pilot’s license so she could make the trip from her Berkeley home in one hour instead of six.

Jodie Foster’s performance as an astronomer who does make contact, in the movie “Contact,” was largely based on time she spent with Dr. Tarter.

Three times, Dr. Tarter says, she has thought we had made contact, but hard-boiled caution prevailed. Once was in France in 1980, when she and her team had to wait for a suspicious source to pass over their telescope, and Dr. Tarter was afraid to go to sleep. “I had to stay up for three days, afraid my French colleagues were going to call up Le Monde,” she said.

Another time, while she was observing with a radio telescope in West Virginia, Dr. Tarter went so far as to alert colleagues in California of an auspicious signal — and then forgot to call back when she discovered it was a satellite.

None of them was E.T. calling. Each one was another way to be fooled, another addition to Dr. Tarter’s checklist, another necessary step along a path that may or may not have an ending.

It was in the 1970s while she was pursuing a Ph.D. in astronomy at the University of California, Berkeley, and raising a daughter that she first heard of SETI: the idea that lonely species could bridge the voids between stars with radio waves. She fell in love with it after reading a NASA report on the subject edited by Barney Oliver, the former head of research at Hewlett-Packard. Reassuringly, Dr. Oliver was a crusty gear head who had made himself and others rich, not the sort of man given to romantic fantasies. Hard-boiled, you might say.

Dr. Tarter said she considered herself lucky to have been born when the issue of life in the universe had become a scientific instead of a philosophical or religious one. “For the very first time we had technology where we could do an experiment instead of asking priests and philosophers,” she said.

“It might take multiple generations,” she added, “but there were no reasons not to start with the tools I have.”

The NASA survey that Dr. Tarter led began with great fanfare on Columbus Day of 1992, the 500th anniversary of the great explorer’s arrival in the Americas — a day that she called the high point of her life, a monument to human curiosity. “I felt so proud,” she recalled.

A year later it was over, canceled at the behest of a senator, Richard Bryan of Nevada, who was skittish about “little green men.”

With help from Silicon Valley friends, Dr. Tarter and her colleagues at the institute took the search private and, over time, began to expand it farther out in space, to stars identified by the Kepler spacecraft as having planets.

Last year, however, the recession left the University of California with no money to operate Hat Creek Observatory, and the Allen Array had to be shut down, a moment that Dr. Tarter called the low point of her career.

“To have built that beautiful instrument and then have to turn it off, that hurt,” she said.

The Allen Array is now back on the cosmic search job, thanks to a deal to share observing time on it with the Air Force. But to Dr. Tarter the whole affair was a wake-up call: SETI needs a permanent endowment. “It’s on my to-do list,” she said last winter.

So she is not moving far, just down the hall, to concentrate on fund-raising. It’s time, she said, to go calling on Silicon Valley 2.0.

The search, she explained, is “too long and too difficult. If we want to attract the best and brightest, we want to be able to say, ‘It’s O.K., they can plan on raising a family.’ ”

Once upon a time it was a crazy, romantic idea, perhaps nothing better than wishful thinking. It still is, but it makes us feel bigger and more grown-up just to try. And now it comes with grown-up benefits, like a retirement plan.

There might or might not be poetry in her soul, but Dr. Tarter’s whole career has been a poem.

Read more: www.nytimes.com

Galactic exploration by directed Self-Replicating Probes

… and its implications for the Fermi paradox

Martin T. Barlow
This paper proposes a long term scheme for robotic exploration of the galaxy,and then considers the implications in terms of the `Fermi paradox’ and our search for ETI. We discuss the parameter space of the `galactic ecology’ of civilizations in terms of the parameters T (time between ET civilizations arising) and L, the lifetime of these civilizations. Six different regions are described….
(…)

Figure 1: Galactic ecology parameter space

(….)
Conclusion
Consideration of the points above, and Figure 1, leads to three broad categories of answer to Fermi’s question:
(F1) They have not visited us because they do not exist. (Regions R1 and R2.)
(F2) The ‘zoo hypothesis’: their probes are watching us now (Regions R3 and R4.)
(F3) They have not visited us because civilizations are all too short lived (Regions R5 and R6).
Of these, possibility (F3) relies all all civilizations being short lived, while the zoo hypothesis appears to be deeply unpopular (partly I suspect because it compromises human dignity.) The analysis above reduces the force of some of the objections that have been made to the zoo hypothesis, since in both cases R3 and R4(ii) we would lie in the zone of control of just one ETI.
If we exclude (F2) and (F3), then we are left with (F1), to which there are no objections except that it is uninteresting. It is worth noting that while astronomers have frequently given rather large values to fci – typically in the range 0.01–0.1, many evolutionary biologists have been much more pessimistic. Even if one is not convinced by all the arguments in [10], it seems very possible that the development of intelligent life requires evolution to pass through several gateways, and hence that fci is very small.

Read more: http://arxiv.org/pdf/1206.0953v1.pdf