Extraterrestrials Probably Haven't Found Us - Yet

kasparn writes "The Guardian today has a story about the Danish astrophysicist Rasmus Bjoerk, who recently conducted simulations on how long it will take to colonize the Milky Way. The basic idea is to send out probes in different directions (including various heights above the galactic plane). He estimates that it will take some 10 billion years to explore 4 % of the Milky Way. Since the age of the Universe is of the same order, his conclusion is that aliens can't have had time required to find us yet."

I should hope so...

[creimer (824291)]

We will be in a lot of trouble if the Cylons find us first.

Eat at Earth

[Dareth (47614)]

We are currently broadcasting the galactic equivalent of "Eat at Earth" sign. Remember we consume "lesser" lifeforms for food. I do love a good steak! Who knows if the aliens who find Earth will consider us as equals or as appetizers.

I am sure their galactic physicians will recommend they don't eat too many humans from the Northwestern Continent due to cholesterol or something, but that they can eat all the yellow humans from the east they want, even if they will be hungry again in a few parsecs.

Duh

[Reality Master 101 (179095)]

Sheesh, talk about "proof by lack of imagination." This is supposed to answer the Fermi Paradox?

You can't explore a galaxy with a handful of probes. 72 probes??? First of all, if you're going to do it that way, you'd create hundreds of thousands of probes, if not millions of probes (mass production would reduce the cost). Second, you still probably wouldn't do it that way. You'd wait until you had the technology to make self-replicating probes, and the galaxy could potentially be explored in thousands of years.

Not impressed by this guy's argument.

Re:Duh

[isomeme (177414)]

You'd wait until you had the technology to make self-replicating probes, and the galaxy could potentially be explored in thousands of years.

Bingo. As usual, Wikipedia has a good article [wikipedia.org] on the topic.

Re:Duh

[myowntrueself (607117)]

You can't explore a galaxy with a handful of probes. 72 probes???
Not impressed by this guy's argument.

He is probably just assuming that the aliens have a pretty much exact parallel to NASA.

Re:Duh

[lucifig (255388)]

Well Darth Vader found Hoth with fewer probes than that and it only took him like 4 minutes.

So I guess you are both wrong.

Re:Duh

[flyingsquid (813711)]

You're right, this guy hasn't thought things through.

Negative. I find your argument untenable. I am in agreement with the Danish monkey-being. Probabilities of non-human life spreading through the Galaxy and discovering primitive monkey-beings in Sol System are minimal. Probability is on the same order of probability of a F'narthag slime-weasel evolving wings and taking flight. It is also highly improbable that extraterrestrial beings would colonize the pathetic planet Earth and blend into the primitive monkey-being society. They would be forced to hide in internet discussion groups and the tech sector so that they are mistaken for geeks when they display lack of monkey-being social skills.

The Galactic Lottery

[neo (4625)]

Come on. 4% is a hell of a lot better than your odds of winning the lottery and that happens *everyday*.

Plus he's not taking into account multiple alien races. So that's like double 4% which is almost 8%. Do that a few hundred times and you get 108%. This guy clearly doesn't understand math.

Wrong, wrong, wrong

[Ignorant Aardvark (632408)]

This figure of taking billions of years to explore the galaxy is utterly wrong. Actually, it only takes a few dozen million years to colonize the entire damn galaxy, which is a lot more effort than merely exploring it.

This figure is based on some very reasonable assumptions. Colony ships travel at much below the speed of light. Each colony gets a thousand years of development time from first colonization before it starts sending out its own colony ships. As you can see, even though it seems quite "slow", thanks to the magic of exponential growth, the entire galaxy is colonized in short order.

We won't merely be discovered if aliens exist - we'll be colonized. That's the most likely scenario for running into aliens. If they never spread beyond their home planet, they'll just be one star out of trillions - but if they do start colonizing, we'd find them everywhere.

I once worked out

[by Anonymous Coward]

Traveling at the speed of light, it would take a quarter million years to reach Andromeda. What's more is that if I went into statis now, the compound interest on my savings would pay for the journey.

It has been done already

[140Mandak262Jamuna (970587)]

The aliens knew they could not send out probes that carry enough energy to beam back the information. So they built generalized adaptive Turing machines, (a machine that can build itself) of incredibly small dimension. They created billions and billions of these machines and scattered them. These machines are so tiny, they get carried by the solar wind and other cosmic radiation.

One of these Turing machines reached Earth about 4 billion years ago. It first had to start by building very simple amino acids, then it graduated to proteins, then to RNA and then to DNA, and then these DNA machines built bodies around them and started using natural selection to evolve into more and more capable organisms. The final aim of these DNA structures is to build powerful radio beacons and send the information back to the original aliens who created these molecules and scattered them to the (solar) wind.

Re:Based on poor assumptions

[QuantumG (50515)]

Yeah, imagine a civilization that, having discovered enlightenment, actually embraced it and dedicated their industrial base to further it, instead of shuffling it off to the minor specialists who they then make beg for funding, typically by militarizing their research.

Re:Based on poor assumptions

[BadERA (107121)]

Psssh, enough of that hippie dudley do-right love and flowers attitude, that will get you nowhere in this life.

(That said, I totally agree with you.)

Re:Based on poor assumptions

[teslar (706653)]

Why 1/10th c? Why not 99% of c? Why not faster than c?

You're still thinking Star Trek when you should be thinking Stargate.

1. Obtain a good enough understanding of space-time to create wormholes to any destination you want.
   
2. Make a list of all destinations you are aware of.
   
3. Send a probe to all of them, evaluate each destination and scan for more destinations from there.
   
4. Go to step 2.

Space ships are just such a small-planet-with-water way of thinking.

SURVEY

[russ1337 (938915)]

I reckon theres a Slashdot survey on the best way to explore:

How would you prefer to travel?

a. A blue Police Box that can traverse space and time, with a hot British former 'teen star' that is obviously in love with your weirdness.
b. A big ancient ring that can take you anywhere where there is a corresponding ancient ring, but you keep bumping into Egyption dog people who try to kill you.
c. A large dinner shaped spaceship that does warp factors, but you get to shoot at klingons and make sexy time with green chicks (remember its all about the Journey!) Just dont get assimilated by Bjork!
d. Travelling with the Robinson family and a stupid robot that shouts "Danger" long after it stopped being funny. Oh and a pedophile.
e. In a ship that can make the Kessel Run in less than twelve parsecs - With a great big hairy Wooky and a gay robot.
e. Spending time on the only ship to have survived an attack by robots with KITT in their face, where it is a daily battle to stay alive.
f. On a moon that was flung out of orbit by a massive thermonuclear explosion initiated by the build up of magnetic radiation, which there is much debate as to it being caused by global warming.
g. Traveling across universes with a guy that looks like Mike Moore, where each new universe you 'slide' into is exactly like being on LSD.
h. On a ship with a dorky hologram an evolved cat, a computer with an IQ of 6000 and a very stupid robot, but every day is hilarious!
I. The space shuttle. (yawn)

Re:Based on poor assumptions

[Nyeerrmm (940927)]

Also, assuming they use some kind of rocket technology (that is, technology that shoots stuff out one side to propel the vehicle in the other), 1/10 c is much more realistic than something approaching c. Assuming a technology that has 100 times the specific impulse as our current vehicles (the best ion thrusters get ~4500 s,) I get using the rocket equation that the initial mass to move 1 ton of cargo is:

1/10 c: 3.263e29 tons .99 c: 1.534e292 tons

Even then this seems absolutely ridiculous. If you used a matter/antimatter reaction so that your propellant was pure electromagnetic radiation (thus your exit velocity is c), you'd get these results

1/10 c: 1.105 tons .99 c: 2.69 tons

Of course, these are not adjusted for relativity, since I don't know any simple equations to do that. I would imagine (as a wild-ass guess) that the 1/10 c estimates are close, but the .99 c results are off by thousands of orders of magnitude.

Basically all I'm saying is that 1/10 c seems fairly reasonable. It's not feasible given our current technology, but its within reason. If you start looking at things like space-time warpage, then we have no idea on any usage or capabilities, so any kind of theory based on it gets even further and further from reality.

By the way, I am a rocket scientist, but only a student, and not a physicist at all, only an interested amateur.

Re:Based on poor assumptions

[gobbo (567674)]

But the bad assumption remains: rocket technology. Like I said, who's to say they haven't gone further with physics, or pursued a different, or completely unthought-of (to us) means of travel?

No kidding. "If we put a thousand horses on a carriage, it still won't be fast enough to lift from the ground. But if we could discover the rumoured winged horse, we can do it."

Something tells me that we're a couple of paradigms away from comprehending galactic distances as attainable. Propellant propulsion systems are to interstellar travel what horses are to flight.

Re:How close minded can one be?

[Rurouni_Jaden (846065)]

"If an alien race has had advanced technology for 100,000,000 Trillion years, then they'd have plenty of time (and would probably have technology more advanced then sending out physical "probes")."

when they show up, please ask them how they survived the big bang.

Irrelevant to the Fermi Paradox

[careysub (976506)]

The study in question does not even address the Fermi Paradox in any meaningful sense, much less "resolve" it. In fact, if this study is being offered as a resolution of the Fermi Paradox then it suggests the researcher does not understand why the Fermi Paradox is a paradox at all.

The fundamental difficulty with any explanation offered for the complete absence (so far) of any sign of other intelligent life in the universe is that the proposed explanation has to be universally valid.

The span of time for colonization, or dispersal of replicating probes, or of building vast telescopically detectable artifacts is so great that even one single exception from any proposed explanation would be capable of generating ubiquitous evidence in a tiny fraction of the life of the Universe.

Simply describing some model for exploration, and then arguing that this model won't do the job says nothing about other models. This study apparently does not consider the geometric growth that occurs with any exploration program that uses some form of replication of explorers, for example. If replication is thought to be impossible then the study would have the high hurdle of convincingly demonstrating this. (The material evidence of life on Earth seems to argue persuasively against it though.)

Arguments that "interstellar travel is impossible" would qualify for explaining why alien artifacts aren't being found locally (but do not address communication signals or telescopically detectable artifacts), but require convincing arguments that this is indeed true. On the contrary, physics does not seem to make this impossible at all, just very costly and slow. Too costly and slow for anyone to bother? Not even one single civilization?

The Fermi Paradox seems to be telling something important about the Universe. If only we knew what it is...

Re:Heh

[pbrammer (526214)]

They want all of our "base"?

Re:Heh

[tha_mink (518151)]

Bitten by the ole RTFA bug eh. The quote from the article is

He found that even if the alien ships could hurtle through space at a tenth of the speed of light, or 30,000km a second, - Nasa's current Cassini mission to Saturn is plodding along at 32km a second - it would take 10bn years, roughly half the age of the universe, to explore just 4% of the galaxy. His study is reported in New Scientist today.

No mention of colonization there.

Plus

Mr Bjork confined the probes to search only solar systems in what is called the "galactic habitable zone" of the Milky Way, where solar systems are close enough to the centre to have the right elements necessary to form rocky, life-sustaining planets, but are far enough out to avoid being struck by asteroids, seared by stars or frazzled by bursts of radiation.

So there's that too. Looks like you should have taken a look at the article first.

Re:Well, DUH!

[Ignorant Aardvark (632408)]

To be pedantic ... the absolute minimum time to explore the whole galaxy from Earth is about 80,000 light-years, because the farthest part of the galaxy is about 80,000 light-years away from us. Although to be even more pedantic, double that, because you can't really say you've explored until the information about what you've found has made it back to you.

So, yeah, you can't explore the galaxy in only a few thousand years.

Re:That's assuming...

[Marxist Hacker 42 (638312)]

Worse than that- the researcher assumes:

1. That they can't develop PROBES that travel faster than 1/10th the speed of light.
2. That probes of this form that would keep running long enough would be so massively expensive that even the most ambitious race would only be able to build 8 of them (He does address this complaint, and also considers 200 probes instead of 8, and von Neuman machines instead of static probes, neither of which drop the figures below 4x10^6 years to explore a mere 4% of the Galaxy).
3. He doesn't even consider non-material, photon-based probing methods, which would increase the rate of exploration by a factor of 10.

Re:That's assuming...

[hjo3 (890059)]

"photon-based probing methods"

You mean looking at stuff through a telescope?

Re:That's assuming...

[Dr. Spork (142693)]

More puzzlingly, he assumes these probes can repair themselves for and keep running for billions of years, but they can't self-replicate. Really? If the probe can repair every potential internal probem on its own, the capacity to self-replicate should come almost for free.