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Ask Slashdot: How Could We Actually Detect an Alien Invasion From Outer Space?
First time accepted submitter defiant.challenged writes As I was watching another sci-fi blockbuster about aliens wanting to harvest the life stock population on earth for their energy since we are such a robust species, I was wondering how likely and easy/difficult it would be currently to actually detect an outer space invasion (fleet). I am a firm believer that if we would be invaded, we would not stand a chance and would probably not even hit a single ship when it comes to fighting them. The aliens in the movie had the capability to space-jump right into our solar system and even very close to earth. My question is how good are we at the moment in detecting an alien ship/fleet that jumps into our solar system. Do we have radio dishes around the globe such that we can detect objects in space in all longitude and latitude degrees? I know we have dishes pointing to the skies but how far can they reach? Do we have blindspots perhaps on the poles? I also wonder if our current means, ie radio signals, are relatively easy to be compromised with our current stealth technology? To formulate it in more sci-fi terms, how large is our outer space detection grid, and what kind of time window can they give us?
Email Elon, see what he thinks.
Frankly, any aliens able to travel here from another world are so far ahead of us, it wouldn't make any difference if we detected them or not.
However, you asked the question... so...
Our space detection system is largely aimed at Earth. For example, to warn of us of ICBM launches the first system put into space was called MIDAS between 1960 and 1966.
http://en.wikipedia.org/wiki/M...
The GPS satellites have nuclear detonation detectors, which doesn't do any good, but it another example of how our systems are aimed at Earth.
All the stuff pointed out into space, like the Hubble Space Telescope, are designed to see VERY far away and aren't looking for ships. Given the small likely size of any ships compared to planets and moons, we aren't likely to be able to see them even if we're looking for them, until they are on top of us.
After all, we still don't have a telescope that can see the moon landing sights. Pictures taken from sats in lunar orbit have gotten some pictures, but they aren't as good as you'd expect.
http://en.wikipedia.org/wiki/T...
This is the best image I could find of Apollo 11's landing site, and this was after the LRO was moved into a lower orbit:
http://featured-sites.lroc.asu...
Yea, you can tell what it is, because you know what you're looking at, but if you didn't even know where to look? You could stare at the moon for a month with such a camera and see nothing.
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TL;DR - We likely would have no notice whatsoever of aliens until they entered orbit of Earth, and even then, it is just as likely to be a random person with a telescope who spots them as anyone from the government.
Unless of course they can be seen with the naked eye, if their ships are big enough and they are in low orbit, that is possible.
Just because the hypothetical aliens are ahead of us in some respects (e.g. the ability to practically travel across interstellar distances) it does not necessarily follow that they would be ahead of us in all others. For instance, consider Harry Turtledove's short story The Road Not Taken which is based around a premise that humanity overlooked a blindingly simple technique for manipulating gravity that put our technological development onto a completely different track than the invaders of the story.
UNIX? They're not even circumcised! Savages!
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The usual example given to illustrate an Outside Context Problem was imagining you were a tribe on a largish, fertile island; you'd tamed the land, invented the wheel or writing or whatever, the neighbors were cooperative or enslaved but at any rate peaceful and you were busy raising temples to yourself with all the excess productive capacity you had, you were in a position of near-absolute power and control which your hallowed ancestors could hardly have dreamed of and the whole situation was just running along nicely like a canoe on wet grass... when suddenly this bristling lump of iron appears sailless and trailing steam in the bay and these guys carrying long funny-looking sticks come ashore and announce you've just been discovered, you're all subjects of the Emperor now, he's keen on presents called tax and these bright-eyed holy men would like a word with your priests.
Banks goes on to note that most civilisations tend to encounter an Outside Context Problem only once, at the point where that particular civilisation ends or is subsumed into the more powerful one. (Incidentally this is also the title of a series of eBooks by Christopher Nuttall which are satisfyingly geeky.)
Of course, there are plenty of fictional examples of invasion, I guess ranging from the barely-competent aliens in Niven & Pournelle's "Footfall" (who were easily detected) and the almost-Gods of Arthur C Clarke's "Childhood's End" who basically just turned up without warning. It's too varied a field to come up with an idea of how we could detect them.
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While that is a nice hopeful story, and while I suppose ANYTHING is possible...
It isn't very probable...
Besides, even if they were at our level of technology, if they have starships, then they have nuclear weapons. They don't have to invade, they can simple drop rocks or nukes on us to accomplish the same thing, and there wouldn't be anything we could do about it...
Unless of course, someone had a Mac laptop and was a cable repair man! :)
it's highly unlikely that space travel can be accomplished without huge amounts of EM radiation.
Why? Why is it unlikely? We have really no idea how to travel faster than light, like so many things, I suspect it is something we haven't even thought of... like how silly airplanes looked, until they actually flew and pretty fast they didn't look anything like the silly 19th century attempts to fly.
What was missing was power, lots of power, in a lightweight package.
Even once we had airplanes, you have only a lifetime from 1903 to 1969, yet people in 1903 couldn't have dreamed of what the Saturn V would look like or how it would work.
It is not rational to assume that unknown technology means godlike abilities.
Nonsense, sure it does...
I am quite sure that if you went back 500 years and took modern technology with you, it would look quite "godlike" to those people.
If we can detect exoplanets, what makes you think that we wouldn't be able to detect alien ships?
For one thing, the planets are in one place, stay in one place (well, in orbit) for a long time, they aren't trying to avoid detection, and they are really big. They also have an effect on something even bigger that is its own light source, a star.
Starships fit none of those parameters. Even more, we aren't even looking for starships and if we were, we don't know what to look for. We DO know what to look for when it comes to stars and planets.
I once had two ducks. I wondered what I looked like to my ducks. I decided that I look like a duck. All the extra powers that make me more than a duck - speech, thinking, telphones, etc. - are beyond the duck's imagination. To a duck, I look like a duck.
Then I wondered what an alian would look like to me, a human. I decided that an alien would look just like another human. So I began to wonder what advanced characteristics I couild watch out for. Successful businessman, good luck, healthy long life, mysterious origin, that sort of thing.
I found one. At the time he was my boss. He pretends to be Chinese, but hey, what westerner really knows what Chinese people look like?
They have landed already; and they are friendly. I was friendly to my ducks, and that Chinese family is friendly to me.
Just because the hypothetical aliens are ahead of us in some respects (e.g. the ability to practically travel across interstellar distances) it does not necessarily follow that they would be ahead of us in all others.
Uh, yes, it absolutely does. If they have mastered interstellar travel, then then there is no way that they will be behind us in any other aspect.
On the positive side, this also probably means that they'd have nothing to gain by coming here or killing us off.
The better analogy would be near-earth objects. Even still, they stay in (sort of) fixed orbits, generally close to the orbital plane of the planets, and don't try to avoid detection. Yet we're nonetheless pretty terrible at detecting "ship-sized" NEOs. If by "ship-sized" one means "aircraft carrier-sized", odds are better than not that it wouldn't be spotted until it was within the orbit of the moon. If we're talking "space shuttle sized", it probably wouldn't be spotted until it got near LEO.
We gotta go to a crappy town where I'm a hero.
But a space-jumping fleet of invading space aliens is? Did you even read the summary?
Actually, it is very probable indeed... just not HERE!
Space is big, really big, unbelievably big... Odds are, somewhere out there, "space-jumping fleet of invading space aliens" DOES exist. Odds of them being ANYWHERE NEAR HERE? Almost zero.
Two separate points. :D
We have problems spotting and tracking 1km-long rocks in space beyond the Earth's orbit. We literally get taken by surprise by large rocks and their orbits all the time, whizzing around our solar system without us knowing they're there.
We're also not looking for those kinds of things, as such. A ship of some description able to sense us from afar and come into the system probably wouldn't jump in at the third planet out by default. They'd probably jump in off-axis, far away, and we'd be hard pushed to spot anything of space ship size (http://io9.com/nasa-spots-a-po...
That wasn't spotted for ages, discovered only in 2013, when it was only 10 times the moon's distance away (nearly a Mars distance). It was spotted only by something looking for near-earth objects and only because it looked like its natural trajectory may bring it close to Earth in the next 100 or so years. It's 650 metres long, orbits every three years and could weigh tens or hundreds of thousands of tons.
We can't see this kind of stuff. The angles and chances are just too small and anything that settles into a natural orbit is basically indistinguishable from a rock. It wouldn't take much for something to jump in just outside the outer planets and settle, say, a Saturn distance away, probably off-axis (hiding in-axis may well give shadows etc. that give it away and we likely look at the planets and other things in our axis more than elsewhere) and we'd never spot it. Never. If we did, we'd think it was a rock.
From there, a basic telescope (or a pair of binoculars) would be able to light us up like a Christmas tree, show us to be particularly interesting, and a simple radio antenna would be able to prove that their was life on here, while at the same time being basically invisible to us without even trying.
Any civilisation with a 1km intra-system space-ship capability likely has much better tech than a $200 telescope and a satellite dish connected to a radio scanner, They'd know we were here, and be able to observe us for centuries, long before we ever would know they were there - and we'd probably NOT know they were anything other than a rock.
The distances are too immense, the angles involved far too tiny once you get out past the moon, and there's just too much stuff moving about if you have a sensitive instrument. Hell, we don't even reliably know what everything in EARTH ORBIT is, let alone trying to go out to even a Moon-distance or Mars-distance or Neptune-distance.
Basically, we would never know. The only way to get to the point we would know would be to colonise enough of the solar systems to provide mapping and triangulation of the entire space in-between, And even then, you probably could still hide if you were at all careful.
The invasion starts in a forest near a small polish village, and the aliens transform into local people they just saw passing by, thus totally hiding their alien presence. But then they meet a drunkard, who bears a grudge against one of the people they have turned into anyway. Their biogenic attack weapons (a swarm of insect-like stitching and poisoning robots) turn back because they can't get through the ethylalcohol cloud surrounding the prospective victim, and the drunkard gets agitated because they aliens don't really react when he yells at them. Their weapon detecting device doesn't warn about the knag lying wayside, and the drunkard takes it and hits them on the head, while they still try to get their translation device to decipher the messages he was mumbling at them - thus killing the aliens and fighting off the alien invasion.
If physics doesn't allow for it, it doesn't allow for it anywhere. It doesn't matter how large the Universe happens to be.
It's a cute concept, but the simple fact is, if you have some simple technology for gravity control that can take a primitive society whizzing around the cosmos, then that primitive society wouldn't be using flintlocks for battle. Because if you control gravity to the point that you can hop some primitive ship in and out of gravity wells and move at relativistic speeds then you're controlling *vast* amounts of energy to do so. And there's no way such a species is going to only make use of this vast amount of energy in their spaceships but not their weapons - even if they're only kinetic impactors.
We gotta go to a crappy town where I'm a hero.
By the same logic, there's also a room of moneys with typewriters somewhere turning out all the great books
Thanks to the Internet, we now know that's not true.
...gis sdrawkcab (usually not responding to ACs; don't bother posting as AC)
people in 1903 couldn't have dreamed of what the Saturn V would look like or how it would work.
Funny that you chose 1903 as your date, since that was the year Tsiolkovsky published The Exploration of Cosmic Space by Means of Reaction Devices, wherein among other things were mentioned that escape velocity could be achieved with a multistage rocket fueled by liquid oxygen and liquid hydrogen.
So yes, at least one person in 1903 not only could have dreamt, but did dream and explicitly state how rockets like the Saturn V would look and work.
"Total destruction the only solution" - Bob Marley
if something isn't forbidden by the laws of physics ...
FTL travel, or even FTL communication, is forbidden by the laws of physics. Light speed limitations lead to boring science fiction, so FTL travel is common in sci-fi, where starships travel at the speed of plot. But there is no evidence that it will ever be possible in reality, and plenty of evidence that it will not.
The real alien threat is not a giant fleet of starships coming out of hyperspace, but a small probe filled with nanobots.
No, that doesn't make any sense, and I'd like a citation to that theory. Something is stealthed if you don't see it. To not see it requires no more than not looking at it. It is certainly allowable by the laws of physics that we don't look at something.
In fact, to suggest an old theory that says stealth of any kind is impossible not only imagines a theory that doesn't exist, but it violates the very principles of empiricism, thereby undermining the entirety of Physics with every other science to follow.
"I am quite sure that if you went back 500 years and took modern technology with you, it would look quite "godlike" to those people."
Don't behead me until your sailors have seen this! A little box, which I carry around with me everywhere, that knows its own position to within mere feet! All I do is press this button, tap right here, and --
Oh, wait --
Actually travelling faster than light isn't really forbidden. What's impossible is accelerating to or past light speed. (Your mass will increase infinitely as you accelerate requiring an infinite amount of fuel.) However, you could theoretically start faster than light. The equations lead to an imaginary number which leads to some debate as to what that means. Interestingly, if you were going faster than light, you'd encounter the same effects (divided by the square root of -1) slowing down to light speed that we encounter speeding up to light speed. However, you could reduce those effects by travelling even faster.
We haven't detected anything travelling faster than light, but that could just be a limitation of our detection capabilities rather than a limitation of the Universe.
My sci-fi novel, Ghost Thief, is now available from Amazon.com.
There was a time in the development of the universe where space and time itself essesntially expanded faster than the speed of light. It is pretty widely accepted physics. But this inflationary period after the big bang wasn't technically "faster" than light travel, because the definition of "faster" was bound up in the expansion of space and time. (If the space-time I am standing in expands, am I "moving"?) So, there is a physical process where matter and energy do something like faster than light travel, but not really. I imagine we could better understand this inflationary process and exploit it in the future to do something that isn't technically "travel". Many things that have been impossible in the past are now possible (space travel). But many things that were impossible in the past remaln impossible (FTL travel). We don't know what the future science will be. So it is best to keep an open mind and not assume anything one way or another, with a bias towards "I won't believe your claims until you demonstrate them to skeptical physicists who subsequently change their minds. Currently, no reputable physicist believes inflation makes faster than light travel possible.Experimental results, or it didn't happen."
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http://en.wikipedia.org/wiki/Action_at_a_distance could be used as to communicate.
No it can't. Although entangled particles can interact, you cannot use the channel to communicate. Any "message" sent looks like random noise. It is only when you compare it after-the-fact that you can see the FTL influence.
It is like you have two perfect random number generators, and you can switch from one RNG to the other, and have the change happen instantly light years away. But on the other end, they just see a continuous stream of random numbers. If you can latter look at the stream of numbers, you can see that the switch happened at faster than light speed, but no useful information was communicated.
No, because the people at the end points can't control what they measure their entangled particles to be. There's no information transmitted in the process, all you get to do is:
1. Measure the entangled property, say, the spin, on Earth.
2. Be like: Wow, on Pluto that must've given <opposite property>.
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