Fast Radio Bursts from Extragalactic Light Sails

by DeusExMachina • 9 years ago

77 94 9 years ago

kangnkodos• 9 years ago

If we are receiving the FRBs, the focused beam must be pointed towards earth. So the spaceships with light sails must be headed in the direction of earth. Get ready for the invasion!

throwaway76455• 9 years ago

Or the FRBs are built using the least efficient beam design ever constructed ;)

Gravityloss• 9 years ago

I think the beam spreads a lot because

1. the wavelength is relatively long, because you want a sparse microwave sail

2. the antenna is of finite size

3. the distance involved is intergalactic

gwern• 9 years ago

Shades of Larry Niven.

M_Grey15• 9 years ago

Protectors or Kzin? Either way, we're done.

rikkus• 9 years ago

Or reflecting off the sail. Or diffracting around it.

misja111• 9 years ago

No because they are only short bursts. If they were guiding a spaceship in our direction then we would observe them as a constant source of light.

eunoia• 9 years ago

Only if they were aiming at where we are now, which doesn't make sense. They would have to aim the craft at where we are going to be in X years. X being the duration of the voyage.

Come to think of it, even if they were aiming directly at where we are now I would assume the light source would still be occulted regularly by everything between us and them.

yazaddaruvala2• 9 years ago

Gotta remember, if we are seeing light intentionally or unintentionally, they pointed these sails to our current position, almost X years in the past. Where X is the distance in light-years.

colanderman• 9 years ago

Well that's silly. How do they plan to decelerate?

valarauca1• 9 years ago

If you project a large magnetic field the extra-solar ionized gas (intergalatic, between stars) can exert a fair amount of drag.

A lot of people talk about bussard collector (magnetic scope for hydrogen/helium) to power fusion. But instead of collecting gas use it as a drag chute.

evgen• 9 years ago

You have two sails in concentric rings that are connected, with your craft attached to the outer ring. When you want to decelerate you disconnect the two rings and and tweak the reflection of the inner ring to be somewhat outward focused and give the inner ring a little push. As it moves forward the energy bouncing off the inner ring is directed backwards to the outer ring, which slows. As long as the inner ring reflect more energy backwards (and to the outer ring) than the outer ring is getting from your source the outer ring slows down. Really hard to describe, but easy to draw. First proposed by Robert L. Forward.

yazaddaruvala2• 9 years ago

Why do you think its "man"ed?

It could be an intra(inter)-galactic ballistic missile (i.e. no deceleration);

Arizhel5• 9 years ago

I for one welcome our new lightsail-powered overlords.

throwaway76455• 9 years ago

Didn't read the article, but it's always fun following these lines of thought. We have no evidence of life outside earth, but darn it...we can't be the only ones here...I mean we can, but that just doesn't sit well with me. I wonder if almost any civilization would end up using lightsails powered by beams or if many skip it in favor of some other technology.

adrianN2• 9 years ago

I like to think that black hole propulsion is the way to go

https://arxiv.org/abs/0908.1803

saalweachter• 9 years ago

Fusion candles.

https://www.schlockmercenary.com/2003-08-03

felipemnoa3• 9 years ago

It will probably be something similar to this [1] that allows humans/aliens to travel to distant worlds. As per my limited understanding, nothing can move faster than light in space-time, but it seems that it may be possible for a space-time wave to move faster than light. We would just ride that wave.

[1] https://en.wikipedia.org/wiki/Alcubierre_drive

AnkhMorporkian• 9 years ago

That requires the existence of exotic matter, something that really isn't known to exist at all, and it'd be pretty surprising if it did. Pretty much all FTL schemes require some exotic thing that's unlikely to actually be feasible in our universe.

M_Grey15• 9 years ago

Remember that any such device allows you to travel backwards in time. Does it still seem so plausible to you when you realize that 'c' isn't some kind of cosmic speed limit, but the speed of causality in the universe?

okket• 9 years ago

Still unlikely, see the Fermi Paradox and The Great Filter

http://waitbutwhy.com/2014/05/fermi-paradox.html

throwaway76455• 9 years ago

Favorite of mine. The author did a tremendous job.

openasocket7• 9 years ago

I've always wondered if we're already observing evidence of extraterrestrial civilizations, we just think it's some natural phenomenon. All of astronomy is based on observation, if we mistake alien activity for a natural process it could completely screw up our understanding of what's going on. For instance, maybe Quasars are artificial super-structures, created as a power source, or a beacon to signal other civilizations (similar to the signals SETI broadcast) or something else.

NOTE: I don't know nearly enough about astronomy to speculate which phenomena could be potentially artificial, but I do think it is a distinct possibility.

kator2• 9 years ago

Maybe I'm just crazy but there are a list of things I hope we figure out in my lifetime, and extraterrestrial intelligence is right up there in the top ten.

M_Grey15• 9 years ago

I think that's one of those things that's better to have been born well after (assuming a good outcome) or born well before (assuming a bad outcome). It's really hard imaging the transition as anything other than misery and chaos.

fsloth2• 9 years ago

Uh, why would proof of extra terrestrial intelligence induce misery and chaos?

anigbrowl4• 9 years ago

I'll take chaos over an oppressive order any day.

njx• 9 years ago

You should read Far Journeys by Robert Monroe

fractallyte• 9 years ago

An earlier exploration of this idea, but in a science fiction novel: Time is the Simplest Thing, by Clifford D Simak (https://en.wikipedia.org/wiki/Time_is_the_Simplest_Thing)

pklausler• 9 years ago

Maybe we have figured it out, and just don't like the answer.

(Short answer: we're alone, or at best among the very first tech civilizations in our galaxy. Longer version: given sufficient time and space, even the most unlikely possibility will take place with probability near 1. If there have been technical civilizations in galactic history at a level slightly above our own or better, it's near certain that somebody would have launched a self-replicating interstellar "Bracewell - von Neumann" probe, and they'd saturate the galaxy for the rest of time. We don't see them, though.)

AbrahamParangi• 9 years ago

There's also the Three-body problem (https://en.wikipedia.org/wiki/Three-body_problem) answer: anyone who knows what's good for them is hiding. Any interstellar-civilization which reveals its presence is destroyed in a first strike by another civilization in hiding. Any self-replicating probes are also hiding (because there's no meaningful distinction between a self-replicating probe and an interstellar civilization anyway).

downrightmike2• 9 years ago

Top 1

jlebrech• 9 years ago

I've often thought to ask whether we'd even come up with technology to pick up fast moving objects in space heading towards us even before we have the capacity to travel at those speeds ourselves.

we've always observe things in nature and then replicated them, if we saw something move faster than light that would advance our technology even if it's just by knowing it exists elsewhere.

kator2• 9 years ago

More than once I've been in a meeting where someone said "But competitor A spent 1 Billion dollars building that". And I would quip back "And now we know it can be built and it won't take a billion dollars to do it".

I agree, the real value is know something is possible from there all things related make more sense and many decisions can be made based on that one fact.

undersuit• 9 years ago

When I saw this new article start popping up yesterday it reminded me of the book Starfarers by Poul Anderson. Strange radiation signatures are detected in space, scientists figure out it is alien tech, and then figure out how to reverse engineer it.

openasocket7• 9 years ago

extragalactic travel seems to be a really dangerous and difficult prospect. The journey will take millions of years (assuming no FTL travel), and there's basically nothing in between. Even if your species is immortal or something, there's serious risks. You need to bring everything to need for the journey, including energy, because there aren't any stars you can stop at along the way to gather solar energy. You'd have to be very careful planning things so you don't wind up stranded partway.

pavel_lishin6• 9 years ago

I think that when they say "intergalactic", they're not referring to ships crossing between galaxies - they just mean that the signals we're detecting (which may be light-sail 'engines') come from outside the Milky Way. The ships themselves could just be cruising between stars within those galaxies.

openasocket7• 9 years ago

Well, now I feel dumb. I should have read beyond the abstract before commenting!

riskable• 9 years ago

If you're effectively immortal why would you want to hang around the same place forever? You wouldn't. In fact, you might hope for "something to happen" along a 100,000-year trip just to shake things up a bit!

Also, don't assume that alien life is like ours. It could be many orders of magnitude more efficient and in all likelihood isn't even biological in nature if they've reached the point where a million-year journey is feasible. It could just be a bunch of AIs constantly re-making themselves from resources they pass by as they coast through the universe.

They might not even have a destination! They could literally just be a bunch of machines that "live" in space. Floating around from place to place, grabbing resources from asteroids as they go by.

Lastly, in regards to energy: Why assume solar? Once you've reached speed you're not going to slow down much. Just leave the sails open to protect your craft from debris. I'd also expect a nuclear battery in such a craft to power on-board components. There's plenty of radioactive material in space to draw from for renewal as well. You also don't have to worry about disposal! Just toss it towards the nearest star system or asteroid belt and get a bit of thrust out of the action :)

openasocket7• 9 years ago

I was talking about traveling between galaxies, my understanding is there's essentially nothing between them: no asteroids to mine. So you'd need to bring everything you might need in advance. But maybe I'm wrong, maybe there is a decent amount of debris floating between galaxies?

They could literally just be a bunch of machines that "live" in space. Floating around from place to place, grabbing resources from asteroids as they go by.

Whenever I think of what an advanced civilization would look like, I picture something like this (though not necessarily just machines). Something semi-nomadic, an entire civilization of ships in a big fleet, wandering together through the galaxy, stopping at various systems to gather some resources or explore the planets. Maybe the fleet breaks up and goes in different directions for a time, and rendezvous later.

kamaal• 9 years ago

There was this movie called 'Oblivion', one of the concepts suggested in the movie was- Interstellar travel being so hostile for biological life only real and practical way of ever encountering a life form would be in the form a machine/AI.

You don't need to travel in your biological bodies. You can upload your brains to the AI and then have the machine basically run forever. The machine becomes your universe, and it figures out how to best survive in the universe(Mine planets, asteroids, prepare better versions of it self etc etc)

jbmorgado2• 9 years ago

I'm as Astronomer. I think it's very interesting to read about these kind of scenarios in novels, but I don't think they have a place in a scientific publication.

We are researchers, we try to explain the universe by improving our understanding of the physical processes that lie behind what we observe. The moment we bring aliens or gods into the picture to explain something for which we don't have an answer, we are doing a disservice to science.

pavel_lishin6• 9 years ago

It doesn't sound very scientific to automatically discount an act of an intelligent being as the source of some phenomenon.

fusiongyro3• 9 years ago

What sounds more scientific to you: "we don't know what causes effect A" or "we postulate elves are causing effect A"?

xenophonf• 9 years ago

The letter itself says:

  Although the possibility that FRBs are produced by
  extragalactic civilizations is more speculative than
  an astrophysical origin, quantifying the requirements
  necessary for an artificial origin serves, at the very
  least, the important purpose of enabling astronomers to
  rule it out with future data.

Never mind the fact that it makes testable predictions:

  It should be possible to distinguish between FRBs of
  natural and artificial (light sail) origin based on the
  expected shape of the pulse, as the beam sweeps by to
  power the light sail.  More specifically, the sail
  would cast a moving shadow on the observed beam,
  thereby leading to a diffraction pattern and multiple
  peaks in the light curve based on the sail geometry.
  A series of short symmetric bursts would be observed as
  the beam’s path intersects with the observer’s line of
  sight.  Hence, looking for similar signatures in the
  signal could help determine whether FRBs are powered by
  extragalactic civilizations...

anigbrowl4• 9 years ago

We should always look for the simplest explanation but be willing to acknowledge and embrace our ignorance too.

Your attitude turns people off science; it's a plodding, unimaginative attitude that pours cold water on every novel idea without even bothering to explore it properly. The history of science is full of discoveries resulting from accident or whimsy, and I think speculation is an important exercise. Nobody ever got to the top of a mountain by meticulously documenting every step of the route.

So there's a risk you'll pin some hopes on an idea that turns out to be wrong. That shouldn't be bad for your career unless you do it all the time. A scientist who is never wrong about anything isn't taking any risks.

jbmorgado2• 9 years ago

Now-a-days with the social networks, everything seems to be about excitement for some people, but the scientific method survived almost two centuries very well without it, thank you very much.

If you want that kind of excitement, try other area, in here, the only excitement comes from finding an answer to a problem based on science, not in some sci-fi novel.

P.S.: The simple explanation in this case is of course some physical process we can't understand. Not an alien civilization making planet sized machines to power their spaceships. This ain't star wars.

Fast Radio Bursts from Extragalactic Light Sails

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