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Transit Detection of a Starshade at the Inner Lagrange Point of an Exoplanet
- yodon 9y agoThe article calculates that solar-radiation reducing shields for earth-sized exoplanets (like some propose for mitigating climate change) will be detectable by the next generation of astronomical telescopes.
- deleted 9y ago[deleted]
- weberc2 9y agoI'm confused... Does this mean we are looking for life sufficiently intelligent to build these radiation-reducing shields? Or are we looking for natural shields (i.e., a moon?) that might make a planet naturally resistant to climate change?
- codezero 9y agoPresumably this would detect both, but I think they are operating on the assumption that the shield would be just enough to shield the planet and that finding a moon sitting in L1 orbit that also has that shape would be unlikely. I didn't read the whole thing yet, but maybe they cover this. As with a lot of stuff in space, we assume a lot to be unlikely until we find out that it's not :)
- the8472 9y agoL1 orbits are not stable, so there would be no natural shields. Not for significant amounts of time anyway.
- drostie 9y agoThe L1 point is a saddle point in the local effective potential: it is therefore not stable enough for an object to stay there without station-keeping. So yes, the goal here would indeed be to detect life capable of creating large structures and keeping them actively in orbit. There is some tongue-in-cheekness to this sort of research, but as the abstract notes, also some seriousness. The tongue-in-cheekness is that we're nowhere near being able to build something this large between Earth and the Sun; as the abstract notes, it has to be around as large as the Earth in order to usefully eclipse the Sun; that's a very very large structure, and we're certainly able to get into space right now: and yet we have no prospects even in the next many thousand years for engineering anything at that scale, unless folks are right about an impending technological singularity. The seriousness, on the other hand, comes from one consideration: blotting out the Sun is probably easier than fleeing to nearby star-systems. It's very hard to say exactly how much energy it takes to flee to a nearby star-system, but a lower limit for the technology that I can presently envision is maybe 10^20 J of kinetic energy; my imagination might not be very good though, but I think that's reasonably conservative. Now the solar power irradiating a disk-that-blots-out-the-Sun is known to be 10^17 W or so. So the claim is, to even harvest the level of energy that is required to try and scout out neighboring star systems, one needs Sun-blotting scales of energy-harvesting technology; the length scale could maybe be smaller by a couple orders of magnitude to scout, but one can imagine that the energy needs of billions of entities fleeing their home planet would be several orders of magnitude larger, too.
- taneq 9y ago> blotting out the Sun is probably easier than fleeing to nearby star-systems If we want to later use the sun-blotter as a solar panel to power our interstellar exploits, then yeah. If we just want to make the Earth a little cooler, we'd be far better off seeding the stratosphere with some dust, creating a mini 'nuclear winter' / 'Krakatoa effect' in a controllable way.
- btilly 9y agoYou know, this sounds like a great idea. Maybe we should be building ourselves one of these...
- tensafefrogs 9y agoBut then they could find us.
- mmjaa 9y agoDoesn't matter, still had planet supporting life.
- pavel_lishin 9y agoIf the alternative is them finding a tombstone planet, maybe it's not so bad.
- downrightmike 9y agoNah, we'll just make ours out of a cloud of vanta black, it'll look like a dust cloud.
- jerf 9y agoThis isn't for piddly-ass "climate change" of a handful of degrees, this is "the sun is two times brighter than it was a million years ago and we're no longer in the habitable zone". For our problems shades in Earth orbit would be just fine, and are probably the best solution overall, really, for dealing with climate change. Not just "man-made" climate change, but all climate change, full-stop.
- mmjaa 9y agoLooking for umbrellas in space. What will we think of next?
- a_gopher 9y agoPaper doesn't address what measures the aliens might use to disguise any obvious signature of the starshade. You'd think that the aliens might not be too keen to create huge beacon advertising their presence to all and sundry...
- Eerie 9y agoThere is no stealth in space. Therefore, instead of hiding, the aliens are going to pro-actively fry every competitor civilization by using their solar shades as a Nicoll Dyson Beam... :-) https://www.youtube.com/watch?v=RjtFnWh53z0 https://www.youtube.com/watch?v=RjtFnWh53z0
- logfromblammo 9y agoOne cannot assume that an alien can think in a fashion similar to Earth animals. Humans have the ability to imagine a possibility for which no supporting evidence currently exists--that species alien to our solar system might exist. That ability might not be shared by the species we can imagine. That is, humans can imagine a species that cannot imagine humans. Such aliens would not even realize that building a planet-sized object that cannot be explained by natural processes might present an existential risk. We, of course, are afraid of hypervelocity impact weaponry, even while having no evidence whatsoever that any such weapon exists anywhere in the universe. Of course, that just means that any species that did fear annihilation by near-c rocks smashing into their planet would simply disguise their star shade so well that we could not detect it. Meaning that any solar shade we can detect was not likely built by any species able to think like us. We could clean up by selling them insurance.
- downrightmike 9y agoThey may not need imagination if they can build dyson spheres, new telescopes could help verify where we should put our efforts at contact: http://www.sciencealert.com/researchers-just-found-a-second-dyson-sphere-star http://www.sciencealert.com/researchers-just-found-a-second-...
- ceejayoz 9y agoI'm not sure how you propose a species that can't imagine things that don't exist would advance technologically to space travel.
- ChuckMcM 9y agoHere I was hoping that Kepler had found a star shade. Interesting point that at some point your observing apparatus gets good enough that you can 'see' the structures built by sufficiently advanced civilizations (sure they cloak their ships in orbit but you can see how they make their home world comfy!) At one of the SETI seminars there was a discussion about when would be the "right" time to alert a newly discovered intelligent species that they aren't alone in the universe. There was a lot of back and forth about indigenous tribes in the Amazon, some of who learned of other tribes by the arrival of missionaries, some by loggers, and some who were out walkabout and came upon the strangers. How you meet outsiders has a different impact on how it affects you. So if you were aliens and you didn't want to 'alarm' or 'damage' humans, what would you use as a signal that it was probably a good time to say "Hello" ? I've always felt that once you could detect they were having conversations on other planets you would now "know" we weren't alone and someone could appear in orbit and say Hi. Others felt it would only be safe if humans felt reasonably confident in their own ability to meet them at their level (so perhaps at least colonies on other solar system bodies). One person at our table was firmly in the only when it is unavoidable, which is to say they are about to send a probe to an inhabited planet or come across a construction like a station that is not easily concealed or moved.
- maxerickson 9y agoThe capability represented by interstellar travel is absolutely terrifying. Especially if it involves anything more than a beeping solar sail.
- westbywest 9y agoThe sci-fi series Three Body Problem sustains the argument that intelligent civilizations evolve into being compelled to mask their existence from interstellar detection, as a matter of survival. General idea is there are always bigger in the ocean, and the time required for interstellar travel is so long that non-zero probability of any newly detected life being hostile becomes intolerable. I.e. civilizations survive over Gyr timescale by concealing themselves, and destroying any neighbors who make themselves observable.
- E6300 9y agoI know I'm gonna get downvoted for saying this, but this is kinda dumb. Might as well look for Dyson spheres by looking for gravitational lensing around dark spots in the sky.
- ansible 9y agoThis is some interesting speculation, and I applaud the researchers who think of things like this to look for. I still estimate that by the time a civilization has planetary-scale engineering capability, that they won't need to make things like starshades. If you have molecular nanotechnology, you can either adapt yourselves to whatever location you find, or just skip the biological body business, and directly upload your consciousness to a computer network. The 2nd option is far more mass and energy efficient to support large numbers of sophonts, and I expect that any civilization to endure long enough will have the majority of its population living online instead of offline. If that even ends up being a thing, and they all don't just merge into a single entity (going in the direction of Star Trek's borg).
- InclinedPlane 9y agoWe could make starshades today if we made it a priority. It would take a shade roughly only about 0.09% the size of the cross-section of the Earth to change the climate as much as all of our CO2 emissions. That's only a roughly 200km in radius shade. If we were spending, say, a trillion dollars a year (1.3% of global GDP, a sum less than what is spent on many other things) we could almost certainly build and launch such a structure in at most a few decades.
- marcus_holmes 9y agoI always think of the "they're made of meat" story when considering this [1]. How do we even know what life looks like out there? Or what it has turned itself into in order to survive, travel and spread? Or even what it started out as? We can't even talk with dolphins, even though we have a very recent evolutionary common ancestor. They're sentient life, tool-users, do we think they'd build a starshade to solve this problem? Shame we can't ask them, or understand their answer. We know trees are alive, we know they communicate with each other. We don't think they're sentient. But how would we know? What would a sentient tree do differently from a non-sentient tree? What would a sentient tree do about the sun getting hotter? Even if they started out like us, the evolutionary responses to living on other planets will change them. We're adapted to the conditions on Earth. If we live on other planets with different conditions then we will adapt, because that's what we do. We don't know how far those changes will go, because all the life we've ever seen has been adapted to Earth. Maybe high-gravity humans are less like sci-fi dwarves and more like Pratchett trolls. We seem to be expecting sentient life out there to resemble us and have similar solutions for their problems. This seems dumb to me. 1: http://www.terrybisson.com/page6/page6.html http://www.terrybisson.com/page6/page6.html
- graycat 9y agoSo why has ET not used something like a Dyson sphere or a starshade to send us light signals as a form of "Hello"? Maybe because by the time a planet is able to send such signals, they have discovered better means, faster than light speed, communications. So, the "Hello" communications have been coming to us for maybe millions of years, but like our planet before we understood radio, we can't detect their communications.
- downrightmike 9y agoWe may even misinterpret the "Hello" signals because we don't understand their mathematics. They could very easily be sending a "Hungry" signal, because they are a race of locust.