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ALIENS are surely AMONG US: Average star has TWO potentially Earth-like worlds

Boffin

Isn't a significant moon required to keep the core molten, in order to provide magnetic shielding from the atmosphere stripping solar radiation?

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Mushroom

The molten core is down to radioactive decay of potassium 40, uranium and thorium. That said, there are lots of other theories of why a big moon could help evolution along, e.g. churning up the oceans a lot.

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And stopping the planet from flipping over on its side.

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Sadly not the case,

Our planet does that, Chandler wobble etc. 16000 and 32000 years if you look at the magnetic field and then the actual poles. Evidence can be found in the way magnetic particles are arrayed inside the earths crust, sediments etc. They align one way and in the next layer they are all another.

My geology degree had a piece on it, helps lend evidence to the theory that Atlantis was Antarctica because 10000 years ago it was on the equator. (well people walked on it)

Assuming we live that long as a species it will be 'interesting' day to relay on magnets or electromagnetism.

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Facepalm

Re: Sadly not the case,

Atlantis was Antarctica because 10000 years ago it was on the equator.

Yeah, no man.

I think you missed this by a few orders of magnitude.

Your geology degree must be stamped "university of life".

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Re: Sadly not the case,

We know it is much older based on ice cores alone. The latest estimates place its age at 34 million years old. So no, the planet is wobbling around to place Antarctica on the equator and being Atlantis.

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Re: Sadly not the case,

dunno where you got your geology degree mate but I think you're mixing up two different concepts.

The first is the MAGNETIC poles flipping which they do every half million years or so. You can see that from the identical but mirrored stripes of reversed polarity of iron deposited in oceanic crust at spread zones. It was initially discovered in the Atlantic - searching for submarines they inadvertently discovered evidence of plate tectonics.

The second is another part of the plate tectonic "picture" which is the presence of fossilized sea shells on top of mountains and evidence of fossilised tropical forests in the rock record near Antarctica. Using the current theory that the processes existing today have existed as far back as we can tell, that means that the rocks that make up Antarctica were at one point at the or near the equator, which is 10,00km away (give or take).

Continental plates move at between 2cm & 5cm per year which isn't that fast until you think - "but it's an entire continent moving" at which point you realise that 2-5 cm / year is plenty fast for something that big and solid to be moving relative to everything around it...

So in 10,000 years it will have moved between 20 and 50 metres which is substantial but not quite at the equator. In fact it would take between 200 million and 500 million years - and as I recall the radio isotope dating and other ageing techniques (matching certain global markers like periods of major vulcanicity with specific chemical signatures across multiple rock deposits and types across continents) put the time at around 335 million years ago, from memory.

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Re: Sadly not the case,

So why a down post with no rebuttal or is it a slow Friday?

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Atlantis

Read the Wikipedia page on Atlantis, then we can discuss things in more depth.

Quote from (the first sentence of) the Wikipedia "Atlantis" article (note the word FICTIONAL):

Atlantis is the name of a fictional island mentioned within an allegory on the hubris of nations in Plato's works Timaeus and Critias...

Atlantis=Fiction

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Re: Atlantis

Troy was fiction until someone found it. An "advanced" civilization 10,000 years ago wouldn't need to be all that advanced to seem amazing to others at that time. If they had farming with human built canals, some type of sewers, and skyscrapers as high as three stories they'd seem as advanced compared to others of that time as flying cars and interstellar travel seem to us today.

I suspect there's a lot of history older than 5,000 years old that is lost (probably forever) due to rising sea levels from melting ice sheets. Maybe Atlantis is part of that. Without writing the story would be corrupted a lot over the centuries as it is retold over and over again.

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Re: Sadly not the case,

Not sure where your geology "degree" came from, but if it locates Atlantis in Antarctica I would not surprised if it came in the mail. The "magnetic" reversals are just that, reversals of the magnetic field, not of the entire physical planet. If you simply consider minor physical laws like conservation of intertia and agular momentum and such, it is pretty clear that if a magnetic reversal involved planetary acrobatics, life would not exist. Neither would the planet probably. If it did, it would probably look a lot like Venus.

As it is, the magnetic field takes "excursions" occasionally as well as "flipping,m" and the event 10,000 years ago or so was an "excursion" rather than a full blown inversion. If you like science fiction, try reading Keith Laumer's "The Breaking Earth" which is based on the idea of the actual physical tumbling of the planetary gyros during a magnetic reversal. Laumer took it easy on the physical effects - i.e. the catastrophic picture he presents is no where near as bad as a real event would have been. It is also the only book I known that even hints that an Atlantis-like civilization existed on Antarctica. Are you sure your geology proph didn't have you read that novel?

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MAYBE.

If it has the right minor elements AND a magnetic field, the upper part freezing might magnetize and retain a field. It has for several iron ore deposits.

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Anonymous Coward

Aliens are among us !

If you'd ever watched a parliamentary debate you would already now that Aliens are indeed amongst us !

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Alien

Re: Aliens are among us !

Or work in my office ;-}

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Alien

Re: Aliens are among us !

Oxygen works like hard dope on the lizard overlords controlling the politic-pods. Nothing else occurring in parliament makes sense.

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Alien

Re: Aliens are among us !

You don't think that........... David Ike might be right!?

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Unhappy

Re: Aliens are among us !

Those 'debates' are necessary to ensure that we never get off this rock...

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Alien

Re: Aliens are among us !

Ike doesn't suspect half of it!

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Alien

It's a long way to the chemist, etc...

But space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is.

Humans have been emitting radio waves for about 100 years or so. That means that any intelligent life more than 100 light years away (which is next door in galactic terms) simply won't know we exist, since the signal won't have reached them yet.

Contrary to what the prof thinks, there could be loads of little green men out there, all whizzing about in their flying saucers, and they haven't visited earth yet, since they just haven't found it yet, or when they last looked, it wasn't doing anything interesting.

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Re: It's a long way to the chemist...

Perhaps that's where Lewis has gone.

Where's the Captain Lawrence Oates icon when you need it?

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Re: It's a long way to the chemist...

Meh. As long as Lewis has his towel, he'll be fine.

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Re: It's a long way to the chemist, etc...

...and at density of 1.4E-4 stars/cubic ly and, at 100ly, a spatial volume of

4/3.pi.(100E3) = 4188790 cubic ly

Number of stars within 100ly radius is 4188790 * 1.4E-4 = 586 stars

However, the number stars that are of the right type AND with suitable (goldilocks-zone) planets is VERY small...

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Alien

Re: It's a long way to the chemist, etc...

After all, would you make a detour to look at somewhere whose description reads "Mostly Harmless."?

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DJO

Re: It's a long way to the chemist, etc...

Humans have been emitting radio waves for about 100 years or so.

And we are emitting less and less every year with low power radios, satellites beaming down instead of stuff broadcast everywhere and more and more of what used to be broadcast being transmitted over fibre. In 100 years I doubt we'd be detectable at all.

Another problem is that the same frequencies are used all over the planet for different purposes which is no problem here but from a long way away they will all blur together into a random like noise where any single signal would be as close to impossible to isolate as makes no difference.

The only radio signal that would be detectable over many light years would have to be one broadcast specifically for that purpose and why would anybody do that?

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Coat

Re: It's a long way to the chemist, etc...

I believe they actually did broadcast, from Arecibo I think. I hope it wasn't pointed at anyone a bit dangerous...

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Boffin

Re: any intelligent life more than 100 light years away...

If they are intelligent, surely they would have noticed the spectroscopy of the atmosphere.

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Anonymous Coward

Re: It's a long way to the chemist, etc...

The signals we've made for most of the last 100 years have also been very weak and nondirectional. There's this thing called the inverse square law. I can't be bothered to do the maths, but anybody looking for radio waves from this planet from even a few light years away is going to be looking for tiny signals against the huge background of all the crap spewing out of that big fusion reactor close by, plus the smaller amount of stuff being produced by Jupiter. Even a megawatt or so won't have much effect by the time you reach Proxima Centauri.

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Re: any intelligent life more than 100 light years away...

Certainly far more useful than Radio, which is too short range really.

I think we only recently realised that it was better to do this and we haven't looked at enough planets accurately enough yet.

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Re: huge background of all the crap spewing out of that big fusion reactor close by

In the range of radio frequencies we use for broadcast it isn't a huge background - the Earth actually outshines the sun in that range, so a should produce a nice big spike on any alien's spectrograph.

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Re: It's a long way to the chemist, etc...

"there could be loads of little green men out there, all whizzing about in their flying saucers..."

It's perfectly possible that any hypothetical advanced alien civilisation is beyond the stage where they produce any significant radio emissions because of increased efficiency, better shielding, possibly living underground and/or inside enclosed structures, and also because being paranoid they don't broadcast their presence to other, potentially harmful, aliens. So maybe there's a couple of centuries time window in which transmitted signals can be received by intelligent life somewhere else. Given the insignificance of a couple of centuries compared to a billions-of-years-old galaxy (let alone universe), it's unsurprising that such signals haven't been detected.

Given that transmitting/receiving radio signals is MUCH easier than space travel it would be inconceivable that alien ships suddenly turn up on our doorstep without us ever having picked up any signals. Of course there are plenty of other possibilities of undetected alien life out there:

1. Since the power of signal that is detectable diminishes by distance according to the inverse square law, there is a distance threshold beyond which our puny transmissions become indistinguishable from background noise (and same for signals coming our way)

2. Although the statistical possibility of humans being the first ever* intelligent species in the universe is remote, there is still that possibility that all the other worlds are still at dino-stage of evolution

3. We associate intelligence with technology but tech has as much to do with our opposable thumbs as with our brains. Dolphins are pretty clever but you won't catch them messing around with iPads (insert Douglas Adams quote here)

4. Super-advanced aliens are using comms tech so advanced that even though their signals (and space stations / ships) are all around us but we can't detect them (dark matter? :P)

*of course concepts like 'first ever' become tricky when combined with travel over interstellar distances

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Facepalm

Re: It's a long way to the chemist, etc... @ GedT

except that star distribution is not even, rather clumpy, and simply doesn't work the way you just calculated, spot on.....

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Re: It's a long way to the chemist, etc...

Super-advanced aliens are using comms tech so advanced that even though their signals (and space stations / ships) are all around us but we can't detect them

Super-advanced? You mean the average modern USAlian, I think.

What would be detectable from many light-years out is radio broadcasts using 20th century modulation (AM, FM, SSB etc.), and radar-illumination transmitters. We're already moving away from these. I anticipate that by 2100 broadcast radio will be extinct. Civilian radar may have gone the same way (replaced by GPS and active location transmision by planes to ground control through an evolved internet). That leaves defence radar, and maybe military stealth technology will have rendered that obsolete as well. (Also taking an only slightly longer view of things, either world peace will render defence radar obsolete, or world war will render advanced civilisation obsolete).

Cellphones, wifi etc. are (or rather, will be) undetectable from many light-years out. An efficiently coded signal is almost indistinguishable from noise, absent knowledge of the coding. Also the radio power per channel is at most two watts (usually more like two milliwatts) rather than the megawatts which Radios Moscow and America used to blast out. As the cells get smaller, so do the wattages.

Assuming technology develops along similar lines elsewhere, the era of accidental long-range interstellar signalling probably lasts for about a century whether its civilisation survives for aeons or not. Which is as good a reason as any why we haven't spotted (another) one yet.

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Re: any intelligent life more than 100 light years away...

Intelligent Humans? I think we flatter ourselves. The Dolphins know better.

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Anonymous Coward

Re: huge background of all the crap spewing out of that big fusion reactor close by

"the Earth actually outshines the sun in that range"

I was sufficiently interested to check this. Solar output is very roughly 1027W, and for a black body at this temperature the amplitude at radio frequencies is about 1/1018 and down. So the Sun is producing maybe a few hundred megawatts over the "radio" spectrum, and very little energy at the long end of that spectrum, and you are quite right.

The next question, which I can't answer, is how much of the energy produced by terrestrial radio stations actually ends up propagated into space. Taking the solar emission of radio waves, a very rough indeed calculation gives me around 10-35W/sq M for the radio spectrum at the distance of Proxima Centauri, with less than 10-37 over the "ordinary" radio spectrum. Given that photons at this frequency range are pretty weak, what sort of detection and resolution could be expected? I know we can identify a comet lander by just three pixels, but we at least had an idea of where it was.

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Linux

Re: It's a long way to the chemist, etc...

Plus you have the signal strength to consider. Will aliens 1000 light years away be able to become addicted to our crap network TV shows? I rather doubt it. I would be surprised if our emissions are recognizable as such even 100 light years out.

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Re: It's a long way to the chemist, etc...

"when they last looked, [Earth] wasn't doing anything interesting."

Wake me up when it starts.

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Alien

Re: It's a long way to the chemist, etc...Sub MM Radio...

since 2007 Sub-Milameter (150-250 terahertz) transmissions to "Out There" have come from several places world-wide ( Russian RT-70 radio telescopes and others) using Terrawatt level CPA's (Chirp Pulse Amps)... with a protocol known as Astro-Pules we may be able to at least "see" comm of others...progress ?? the Astro-Physics folks aren't talking...Scientific Method Rules apply... caveiat ?? :-) ...RS.

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Windows

Re: It's a long way to the chemist, etc...Sub MM Radio...

Prime directive of the commentariat: "Any poster using ellipsis more than once in a text is to be regarded with suspicion and any attempts at communicating with said poster shall be curtailed (exceptions apply if said text consists of citations of government-issued drivel and marketdroid droppings) "

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Re: It's a long way to the chemist, etc...

How about sending out a bunch of nuclear bombs and shoot them off where it's safe? They could spell out CQ DX in Morse code. They oughta be able to see that.

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Joke

@Electron Shepherd

"simply won't know we exist, since the signal won't have reached them yet."

Unless they have been wandering far and near exploring the universe. This would require they have interstellar transportation.

"or when they last looked, it wasn't doing anything interesting."

You mean yesterday?

Actually any aliens with any sense would avoid Earth at all costs. Humans would infect their minds with greed and violence etc.

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Boffin

Our moon also gives help spin-stabilize us to stop the planet from flipping over. Mars seems to have changed axis by about 60degrees over the long term

Perhaps also very important for long term development:

- large magnetic field to keep ionizing radiation from the solar wind off

- large tides pushing movement of animals to the land

- active (but not too active) tectonic plates stopping the whole planet being covered in a shallow sea (great for dolphins, but not space-faring species)

-having massive outer planets (picking up some infalling comets)

-being at the edge of the galaxy (being far from nasties like gamma ray bursts and supernovae)

-not being in a dense cluster (interaction with other stars messing with planetary orbits)

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if we expend vast amounts of time, effort and resources killing eachother in war and terrorism etc (not to mention animals for sport/fun), i'm sure we wouldnt think twice about blowing up any alien species that came within range - if they are clever enough to get here, they're smart enough to stay away

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Joke

Or maybe they found out that we are made of meat...

They're Made Out of Meat...

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Trollface

Charles Stross suggests that neighbors are ISIS-like and abhorrent

Sagan sighs. “Okay, play it your way.” He closes his menu. “Ready to order?”

“I believe so.” Gregor looks at him. “The spaghetti al’ polpette is really good here,” he adds.

“Really?” Sagan smiles. “Then I’ll try it.”

They order, and Gregor waits for the waiter to depart before he continues. “Suppose there’s an alien race out there. More than one. You know about the multiple copies of Earth. The uninhabited ones. We’ve been here before. Now let’s see…suppose the aliens aren’t like us. Some of them are recognizable, tribal primates who use tools made out of metal, sea-dwelling ensemble entities who communicate by ultrasound. But others–most of them–are social insects who use amazingly advanced biological engineering to grow what they need. There’s some evidence that they’ve colonized some of the empty Earths. They’re aggressive and territorial and they’re so different that…well, for one thing we think they don’t actually have conscious minds except when they need them. They control their own genetic code and build living organisms tailored to whatever tasks they want carrying out. There’s no evidence that they want to talk to us, and some evidence that they may have emptied some of those empty Earths of their human population. And because of their, um, decentralized ecosystem and biological engineering, conventional policy solutions won’t work. The military ones, I mean.”

Gregor watches Sagan’s face intently as he describes the scenario. There is a slight cooling of the exobiologist’s cheeks as his peripheral arteries contract with shock: his pupils dilate and his respiration rate increases. Sour pheromones begin to diffuse from his sweat ducts and organs in Gregor’s nasal sinuses respond to them.

“You’re kidding?” Sagan half-asks. He sounds disappointed about something.

“I wish I was.” Gregor generates a faint smile and exhales breath laden with oxytocin and other peptide messengers fine-tuned to human metabolism. In the kitchen, the temporary chef who is standing in for the regular one–off sick, due to a bout of food poisoning–will be preparing Sagan’s dish. Humans are creatures of habit: once his meal arrives the astronomer will eat it, taking solace in good food. (Such a shame about the chef.) “They’re not like us. SETI assumes that NHIs are conscious and welcome communication with humans and, in fact, that humans aren’t atypical. But let’s suppose that humans are atypical. The human species has only been around for about a third of a million years, and has only been making metal tools and building settlements for ten thousand. What if the default for sapient species is measured in the millions of years? And they develop strong defense mechanisms to prevent other species moving into their territory?”

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Re: Charles Stross suggests that neighbors are ISIS-like and abhorrent

Which is disturbing. But his other suggestion as to the nature of our cosmic neighbours is almost as bad:

"I will by return of signal send you the [symbol: process][symbol: data] to install on your [empire/civilization/polity] to participate in this scheme. You will then construct [symbol: inferred, interstellar transmitter?] to assist in acquiring [ownership signifier] of [compound symbol: inferred, bank account of absent galactic emperor]."

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Anonymous Coward

Re: Charles Stross suggests that neighbors are ISIS-like and abhorrent

Perhaps we could apply this in reverse. Perhaps out there is a civilisation that uses high level nuclear waste as a currency, and we can fool them into taking it without getting anything back in return.

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Ogi
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Re: Charles Stross suggests that neighbors are ISIS-like and abhorrent

Well, seeing as what we call "nuclear waste" is in fact nuclear fuel that we couldn't burn in the reactor (hint, if it is radioactive, it still has energy in it) it is perfectly plausible that our nuclear waste to be usable in fuel in more advanced nuclear reactors.

The technology exists already, from what I remember, only the US (of nations that have the technological capability) does not reprocess spent fuel, but rather just dumps it into long term storage.

http://en.wikipedia.org/wiki/Breeder_reactor#Fuel_efficiency_and_Types_of_Nuclear_Waste has some info on reactors which can make use of nuclear waste to generate more heat.

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Anonymous Coward

Re: Charles Stross suggests that neighbors are ISIS-like and abhorrent

high level nuclear waste as a currency

Not sure why they would like to take containers of EUROs?

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Re: Charles Stross suggests that neighbors are ISIS-like and abhorrent

He's also contributed at least two more scenarios:

"Saturn's Children" / "Neptune's brood". Our successors are AIs which we created as our slaves. We then go extinct (as slave-owning societies always have done in the past, on a non-global scale). They're out there, colonizing the galaxy and trying to reincarnate homo sapiens (from DNA codes, with a degree of success), for quasi-religious reasons!

Accellerando, in which human beings are supplanted by evolved digital corporations which no longer need to preserve their human customers. These denizens of "Economics 2+" turn the entire solar system into computronium (solar-powed computing substrate) and don't travel, because they always seek the most bandwidth-rich environment, ie nearest to Sol.

The first pair of books are amusing and less implausible than most interstellar SF. Accellerando will haunt your imagination. Both recommended.

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ADC

Re: Charles Stross suggests that neighbors are ISIS-like and abhorrent

Then there's the Greg Bear/Forge of God/Anvil of Stars scenario.

That we don't see other civilisations because the hunter-killer self-replicating machines got there first.

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