How could "they" find us...!!??

HAZZARD

Lets set aside the question of whether advanced galactic societies would have the slightest interest in our wars, WMD, our pollution problems, our reproductive systems or our cows butts.

The real question is, how would they know about us at all?

There is only one way that they can tell from interstellar distance that intelligent creatures inhabit this planet....RADIO. Our radio signals travel at the speed of light, and this means that even with infinitely fast spacecraft, the aliens cant be much farther off than 15 light-years to have reached our lovely planet by 1947,(Rosswell).

The number of star systems within 15 light-years is about three dozen. There would have to be 10 billion technically sophisticated societies in the Galaxy to have a reasonable chance of finding one camped out among the nearest three dozen stars. Thats optimism of a high level indeed.

What about warp drive...? Lightspeed...? Maybe the aliens can create wormholes and get here in essentially no time....?

It doesnt matter.

Ill worry about how they got here once Im convinced that theyve really made the scene.

To get here they need to know were we are.

Approximately half the U.S. population suspects that extraterrestrials have come to our planet. This is such a controversial (and emotional) topic that its mere mention guarantees a storm of Web chat and high-voltage PMs.

In the end, of course, the matter of alien visitation will be decided by the evidence, not by the intensity of opinion.

While I certainly expect that the Galaxy is home to many advanced societies, the quality of the evidence has so far failed to convince me that any of them have emissaries on our planet.


PS:... I would find myself extremely self centric if I said that there are no other intelligent civilizations out there... I am convinced there are many. But I highly doubt that any of them happened to be so close that they have discovered us in our little, private corner of the galaxy.

whybother

Morbid curiosity, but where did you get that statistic from?

And I'm not totally sure what your question is... if intelligent life existed elsewhere, how could they find us? And you sort of answer it yourself with 'radio waves', so yes, that seems like a valid method, many frequencies of man-made EM transmit through the atmosphere and into space, they could notice.

And as a slight note:
This implies they could be here instantly. I think you meant "near light speed ships" to mainstain some sense of physics.

mgb_phys

It's from an (in)famous CNN poll that said
Not clear how only 54% believe in ET but 64% believe in a coverup!

whybother

That is horrifying... for several reasons...

junglebeast

People will believe what they want to believe regardless of how irrational it is. Just look at religion. At least the people who believe in alien's have latched onto a concept that probably does exist somewhere in the universe, unlike the concept of a god.

moose

An idea is that they just searched some planets they felt could support life.

mgb_phys

"Hitch-hiker's guide to Galaxy" by Douglas Adams (but you all knew that)

junglebeast

The big bang occurred 13.73 ± 0.12 billion years ago.
300 million years after the big bang stars and galaxies started to form.
5 billion years ago the Sun was formed.
3.8 billion years ago the first life forms evolved on earth.
700 million years ago animals have evolved.
600,000 years ago homo-sapiens evolve.

After each mass extinction, evolution rapidly converges to a stable-state global ecosystem, and then minor changes progressively follow. If it weren't for the mass extinctions during the days of the dinosaurs, that stable state might have persisted forever without a highly intelligent race like man ever evolving at all.

On an alternate world, highly intelligent life could have evolved during the "first wave", so lets assume the Earth time for the first wave of animals was typical, and that it takes about 4.3 billion years after a star is formed for the first advanced life forms to evolve on a planet (best case scenario). Then, perhaps the first intelligent life forms evolved in the universe 9.25 billion years ago.

Let's give them another 1 million years to develop space travel, and let's assume they have some very advanced craft that can travel at 5% of the speed of light (this is at the upward end of some theorized future space craft speeds).

(9.25 billion years) * (31556926 seconds / 1 year) * (3x10^8 meters/sec * 0.05 ) * (1 km / 1000 m) ( 1 light year / 9,460,730,472,580.8 km ) = 462 million light years

That means the maximum possible radius that an alien could have come from to visit Earth (if they randomly flew straight for us) would be roughly 462 million light years away -- which is significantly larger than the diameter of our galaxy ;)

HAZZARD

I agree, (and sorry for sometimes rambling on/thinking out loud)... We dont know much about the average lifetime of technological societies, other than the fact that ours has, so far, managed to survive for a century. We also dont know at what rate sentient societies spring up in the Galaxy. But we do know that this rate is surely tied to the frequency with which stars are born. Clearly, a greater flux of new stars will ultimately produce a larger number of planets with thinking beings.

What is the star formation rate? Well, there are roughly 200 billion stars in the Milky Way, and that means that the average rate over the last 13 billion years has been about 15 new stars per year. Anyone whos used a radio telescope to study galaxies knows that when you examine a big spiral like the Milky Way, you find that the total amount of interstellar gas is typically a few percent of the mass of all the stars. Since interstellar gas is the stuff from which stars are built, its obvious that theres little material around today for constructing new ones. Clearly, this must affect the number members for our club of intelligent beings. And not to the possitive.



And about this "cover up" mentality. It is dismaying that many people assume proof that were not alone would cause governments to cover up the facts. I dont believe this for a second.

Consider the 1938 radio broadcast of War of the Worlds. Some Americans mistook the fictional Martian invasion for news, and fled their homes. Would a real discovery of extraterrestrials occasion a breakdown in public order?

This seems highly unlikely. Picking up a signal from space is different from watching aggressive aliens land in the pastures. Its difficult to imagine galactic beings would ever charge across the dark deserts between the stars merely to harass the inhabitants of a small planet.

I think that IF we ever detect a signal from other worlds would be wondrous. It would show that the appearance of life on this world and its slow, uncertain path to us - creatures that can comprehend their own existence - is not some improbable miracle, but a frequent occurrence.

In the 17th century, when early telescopes were revealing great clouds of stars, French mathematician and philosopher Blaise Pascal wrote that the enormity of space terrified him.

Space is enormous. To learn that others are out there would be a comfort.

junglebeast

Although stars are being born and die all the time, a galaxy does not just grow linearly with time like that. In the same way that our solar system formed from a large nebula of gas, causing all the planets to accrete simultaneously, I think the galaxy itself would have formed all the stars in it simultaneously to start with.

Anticitizen

There's also acceleration times to consider, and deceleration times, if we assume they bothered to slow down and not just zoom by at 5% C. That shortens the radius quite a bit.

DaveC426913

Your premises go awry here. We don't search for intelligent life, we search for signs of any life, and explore. Why would they be any different?

So, they detected our oxygen atmo, which pushes out the timeline to more than a billion years.

junglebeast

Good point...and just look how excited scientists are to discover exoplanets of roughly the correct size and distance from their stars. If we had the technology for interstellar travel, we would be interested in visiting almost all of those exoplanets even before knowing their atmospheric composition. So..this could give motivation to aliens to start heading in our direction even before photosynthesizing plants start oxygenating our atmosphere.

DaveC426913

That was kind of what I was suggesting, but I think you may be carrying it too far.

If we presume an level of technology capable of getting them across interstellar distances, we should be able to presume that they've got planet-spotting down pat (where as we are in the infancy of both). Only really unique planets (such as ones supporting life) would stand out of the crowd.

junglebeast

Planet spotting isn't without it's own fundamental limitations. If the interference and scattering of light waves makes the signal to noise ratio small enough beyond some distance that, by Shannon's theory, it would be impossible to detect the relevant information from beyond a certain distance.

HAZZARD

Sure, any advanced ET could spectroscopically sample the light reflected from our atmosphere, and learn that it has large quantities of oxygen and methane, tell-tale markers of biology. If biology is common in the universe, then Earth might be just another entry in a long list of "living worlds" compiled by ET.

Its discovery might not excite them very much?

But lets say they have some kick a** planet-finding telescopes, they could find our planet from hundreds or even thousands of light-years distance. For them to see the Great Wall of China, the lights from our cities, or even the cities themselves, would be extremely difficult.

Not to mention that the light carrying the immage would be hundreds or even thousands of years old. And that meens no Great Wall of China and no light from our citys, right.

If they exist at all...?

Who knows, we might be the only intelligent life in the entire universe?

DaveC426913

If I read your logic correctly, you're assuming these guys are evolving around a Population III (first gen) star, which is virtually impossible. I think we have to assume a Population I star, which greatly shortens the time available.