Scientists Now Searching for "Alien Transit Systems"

Hi again.

I came across the following story today on the site of Scientific American and felt it would be of interest to ATS. Its subject is searching for extraterrestrial intelligence, not by looking for radio messages or their version of television but by looking for the effect of propulsion systems which we our selves know how to make, have built on a small scale and may someday use to traverse the stars.

Papers such as that illustrate some of the "Out of the Box" thinking from scientists which are hoping to answer one of humankind's greatest mysteries. Often people on ATS are unaware of some of these unconventional approaches.

This newer form of SETI rather than looking for technology we currently have which is almost 80 years old, looks for things which we may do in our future which we understand the physics of today.

Those of you who read my ATS thread Denying Ignorance About SETI: It's Not Just About Radio Anymore back in April or when it resurfaced recently are no doubt ahead of the curve and know a little about this. If you didn't read it you may find it interesting after reading the article below.

What prompted the article on Scientific America's site is a new scientific paper published entitled: "SETI Via Leakage From Light Sails In Exoplanetary Systems" - James Guillochon and Abraham Loeb - ArXiv

Here is part of the abstract:

The primary challenge of rocket propulsion is the burden of needing to accelerate the spacecraft’s own
fuel, resulting in only a logarithmic gain in maximum speed as propellant is added to the spacecraft.
Light sails offer an attractive alternative in which fuel is not carried by the spacecraft, with acceleration
being provided by an external source of light. By artificially illuminating the spacecraft with beamed
radiation, speeds are only limited by the area of the sail, heat resistance of its material, and power
use of the accelerating apparatus.

You can read the entire paper at the link above if so inclined.

Here is an excerpt from today's Scientific American article:

Avi Loeb has an unorthodox new idea about how to search for alien civilizations—and it is hardly a surprise. Loeb, who chairs the astronomy department at Harvard University, has spent much of his career thinking about how the first stars came to life after the big bang, and how galaxies were born. But lately he’s become intrigued with the search for extraterrestrial intelligence, or SETI, and he tends to come at it in unusual ways.

Over the past few years, for example, Loeb has suggested searching for aliens by looking for artificial lighting on Pluto, in the admittedly unlikely event that extraterrestrials (ET) have set up an outpost there. He also has proposed trying to detect industrial pollution on distant exoplanets. His latest notion, laid out in a paper he and a co-author just put online: We should look for the microwave beams ETs might use to send light sails wafting between the planets in their home solar systems. “I don’t think it’s nuts,” says Seth Shostak, senior astronomer at the SETI Institute in California. “It’s a clever idea.” Light sails themselves are an actual thing, at least in theory; they use huge sheets of ultrathin Mylar to catch the solar wind, allowing them to carry a payload across interplanetary space without rockets. A prototype is now in the works sponsored by the Planetary Society, which has already flown a test mission and hopes to do a full-fledged demonstration flight next year..

“Unfortunately,” Loeb says, “there’s not enough push in sunlight to provide a very strong acceleration, so one can imagine using artificial radiation instead.” Loeb and his co-author, James Guillochon, a postdoctoral Einstein Fellow at the Harvard–Smithsonian Center for Astrophysics decided that microwaves would be the best candidate, based on efficiency and other factors. To move briskly between planets in an extrasolar system, they figured, you’d need a microwave beam with about a terawatt’s worth of power. “That’s about a tenth of Earth’s entire output,” says Loeb—kind of a lot. But these are aliens he’s talking about, so they could plausibly pull it off, using a powerful ground-based microwave transmitter aimed at the light sail.

Most of that power would be trapped by the light sails. Some, however, would inevitably leak around the edges, so the two astrophysicists did some calculations to see if the leakage could be detected from Earth. Their equations said yes. “It would be easily detectable out to hundreds of light-years away with existing antennas,” Loeb says. The signal would arrive as a burst of energy caused by leakage from one side of the sail, followed by a pause and then a comparable pulse from the other side—a pattern, the authors say, that would distinguish it from natural sources of microwaves.

Continue reading at Scientific American (you'll want to do so before the amount of time the article is available for free expires and it ends up behind a paywall.)

It should be noted that a microwave propelled light sail is on the alien spacecraft portrayed in the Science Channel's educational and entertaining series "Alien Encounters" which ran for several seasons.



The ship arrives in Season 1, Episode 2 which is embedded here:



It should be noted that the paper linked above is not the first time this type of search has been suggested. In a casual search on NASA's Astrophysics Data System (ADS) at Harvard University I found a paper published the year I was born, 20 years ago in 1995. It is entitled Detection of Extraterrestrial Civilizations via the Spectral Signature of Advanced Interstellar Spacecraft by Robert Zubrin. It was published by the Journal of the Astronomical Society of the Pacific as part of their Conference Serie. It was originally presented at the 1993 Bioastronomy Symposium, held in Santa Cruz, California, August 16-20, 1993

Almost exactly 22 years ago!

Here's a little bit of the abstract:



BTW: That journal was edited by Seth Shostak who was relatively unknown outside of science circles then but is fairly well known as the public face of SETI today due to his many TV and radio appearances.

What about Robert Zubrin?

If Robert Zubrin's name sounds familiar it is because he is the same American engineer named Robert Zubrin whose "Out of the Box" 1990 proposal to get a human mission to Mars with technology of that time called Mars Direct was enthusiastically received but due to political naivety (he did not advocate using the ISS to support such a mission for example) his plan was not adopted. Zubrin founded The Mars Society whose advocacy of Mars exploration is part of the reason why it enjoys political support in Congress. He also wrote the book The Case For Mars.

The idea is certainly not without merit, but searching for microwave beams or any other concentrated frequency used to propel light sails is essentially searching for nano-scale needles in a galactic haystack. They would necessarily be laser-like beams with tight focal widths, so unless they're aimed pretty much at us, good luck. Not saying that if it's possible to stack that particular aspect of the search onto another that it's not worth it. It would certainly be a far more definitive sign than most. But it's an incredible longshot, to say the least.

a reply to: pfishy

They would necessarily be laser-like beams with tight focal widths, so unless they're aimed pretty much at us, good luck.

In which case, we would be expecting visitors.
The Mote

originally posted by: pfishy
The idea is certainly not without merit, but searching for microwave beams or any other concentrated frequency used to propel light sails is essentially searching for nano-scale needles in a galactic haystack. They would necessarily be laser-like beams with tight focal widths, so unless they're aimed pretty much at us, good luck. Not saying that if it's possible to stack that particular aspect of the search onto another that it's not worth it. It would certainly be a far more definitive sign than most. But it's an incredible longshot, to say the least.

Beamwidth spreads with distance though, even with lasers. This is even more the case with Microwaves (handy calculator here). So it would not necessarily have to be pointed directly at us but just in our general direction.

It's worth a look. Not looking when we have the capability to do so would guarantee we wouldn't find one.

a reply to: JadeStar

Definitely not saying it's not worth searching for. Just that it holds very small odds compared with the much wider search SETI is currently performing.

a reply to: pfishy
I just have to bring this to the table.
seti.harvard.edu...

Pretty early work by a man I know:
J. D. G. Rather, "Lasers revisited: their superior utility for interstellar beacons", Journal of the British Interplanetary Society, Vol. 44, No. 8, pp. 385-392, August, 1991.

originally posted by: pfishy
a reply to: JadeStar

Definitely not saying it's not worth searching for. Just that it holds very small odds compared with the much wider search SETI is currently performing.

Without knowing how widespread such spacecraft are we can not make any determination of the odds of detecting one. And this type of search is part of the wider search not to the exclusion of it.

It all falls under the SETI umbrella. No one knows what aliens might do so we should look for whatever is detectable.

SETI by its nature has very small odds but its potential reward is the reason for doing it.

originally posted by: Phage
a reply to: pfishy
I just have to bring this to the table.
seti.harvard.edu...

Pretty early work by a man I know:
J. D. G. Rather, "Lasers revisited: their superior utility for interstellar beacons", Journal of the British Interplanetary Society, Vol. 44, No. 8, pp. 385-392, August, 1991.

Excellent paper. It's often referred to.

Charles H. Townes the inventor of the laser was the first to advocate looking for lasers and masers for ET.

a reply to: JadeStar

I understand the nature of SETI, and the fact that any intelligent species is using our same tech is small odds. They are just listening for what we can detect, based on our own technology. I'm just pointing out that searching for a microwave or other em beam to power a light sail is incredibly small odds, even compared to the rest of their mission. Simply due to the inherent directionality of it.

originally posted by: pfishy
a reply to: JadeStar

I understand the nature of SETI, and the fact that any intelligent species is using our same tech is small odds. They are just listening for what we can detect, based on our own technology.

Which is about all anyone could do. And since their technology no matter how advanced would exist in the same universe with the same laws of physics its reasonable to assume some of it would be detectable.

a reply to: pfishy
So why not look for anything that may have any chance of being detected?
It's obviously a long shot. So what? If it happened to be detected, it would a pretty clear signal.

This is another "Made to Fail" SETI distraction.

Microwaves used for Sails?! Propulsion emissions?! Are these thespians serious?! Sure let's look for starfaring, alien civilization who employ either mirror technology, or assume their advanced propulsion even emits harmful waste, fallout, or signatures. Sure, advanced life uses propulsion that normally sterilizes fertile ground, or contaminates environments and their indigenous constituents. Makes perfect sense! Who scripts this chaff?

Want confirm alien life? Deregulate civilian enterprise of space travel and communication. Remove government influence and their corporate puppets.

a reply to: Phage

I'm not saying it shouldn't be looked for. Never said anything of the sort, Phage. I'm just remarking on the odds of finding it. Heck, if I had any actual say, I'd triple the NASA budget and give 2 billion a year to SETI. It's damned important science. I'm only saying that searching for the particular beams to power light sails is a serious longshot. But I'm not saying they shouldn't. I actually admire the bit of genius involved in figuring out that we should even look for them.

a reply to: pfishy

It is a long shot. But long shots have been know to pay off. No?

a reply to: pfishy

It is a long shot. But long shots have been know to pay off. No?

a reply to: JadeStar

Absolutely. But a sufficiently advanced civilization may also be using tech based on laws we haven't learned yet. Again, not saying it isn't worth it. I've always been a fan of SETI. Heck, I ran that SETI@home program/Screensaver for 5 years, despite the unrealistic resource drain. Look for everything! Maybe we will detect a species that farts in VLF. I don't discount much of anything. Except maybe VLF farts.

a reply to: Phage

Absolutely. Again, not knocking the idea at all. Just remarking on the odds. If someone had thought to look for this, and they WEREN'T doing it, I'd take issue.

I have to admit, I was half hoping the OP article would be about distortions in spacetime due to frequent warp travel through certain areas, and a method to search for it. TNG really set the bar too high for my science fantasies.

Why not look for gravitational disturbances and/or warping of spacetime? (assuming we can even somehow watch for that). I would assume that "light sails" wouldn't be used by a truly interstellar alien civilization. We should be looking for the equivalent of a "warp signature" from Star Trek, no?

a reply to: MystikMushroom

The idea is to look for any advanced civilization.
We know a light sail is a feasible means of travel. Not so much that other thing. But similarly, unless they were headed right for us, such a disturbance would be highly transitory. Only visible as it passed between a star and the Earth.