Assuming Aliens are trying to detect "Earth" like planets

a reply to: Xeven

Determining the size and motion of the moon or an exomoon
that exhibits the same properties as Earth's wobble, I think would do it, along with an atmospheric spectroscopy revealing a similar composition to Earth's. Even if it were to turn out to be a water world without surface landmasses, that would about do it I think.

Single Giant moon in similar proximity and configuration would be helpful to produce another Earth-like world.

originally posted by: Xeven
Assuming Aliens are trying to detect "Earth" like planets, what could we do to Earth or our Solar System to say YEP there is intelligent life over here?

Increasing the human collective conscious may be a start. Considering some may carry more telepathic attributes of communication and may already know the presence of human existence but avoid due to the immature energy detected.
Greed-racism-wars political or religious based may be signs of a immature species still experiencing species self hatred behavior.
So logically if humanity cannot even find peace for itself why or how could it find peace with them?

a reply to: Ophiuchus 13


Maybe they know we are here but are simply not interested?

a reply to: oldcarpy

Sounds plausible.
Could also be they have interest many are not aware of and prefer not to disturb in mass but contact/interact more directly on individual bases with some receptive.

I wouldn't draw too much attention to ourselves.

They may come and blow up the Earth to make room for an intergalactic highway.

Never know...

a reply to: Terminal1


Or perhaps they'd like to come and meet us but they think they'll blow our minds?

a reply to: Xeven

The Methane that's abundant in our atmosphere would be a dead giveaway that this planet holds life. Also this would have been present 100's of millions of years. So the likelihood is that they already know about us and have done for a long time! Wow, a scary thought hey?

originally posted by: Soylent Green Is People
-- If the aliens lived within 100 Light Years of Earth (which is practically next door in galactic scales) them they could potentially be able to detect our radio waves -- although the signal would be very weak 100 LY out.


-- If the aliens lived, say 250 light years or so away (still pretty much in in our galactic neighborhood), then a spectrographic analysis of the light from our atmosphere might allow them to detect the industrial gases in our atmosphere our civilization has been producing since about the industrial revolution, which would be another sign to them that Earth has a civilization of some kind.


-- If the aliens lived, say 2000 light years or so away, which is still only about 2% of the way across the galaxy, then a spectrographic analysis of the light from our atmosphere might allow them to detect the burning of wood in our atmosphere that they might perceive as a sign to them that Earth has a some kind of intelligent life that has harnessed fire -- but would not necessarily be a technological civilization.

A radio wave would still take 100 years to travel 100 light years and would likely not even be able to be detected due to the medium of space it travelled trough. Cosmic radiation and other noise would distort it.

At 250 LY the light from the sun is not detectable, so a spectrographic analysis of the atmosphere of earth is laughable sci-fi handwaving magic from too much TV/Film. Might as well use the force.

At 2000 LY who the # is even going to know that earth exists if the sun is a dark spot in the blackness of space. Where is this spectrographic magic from, what Show/movie on youtube sold this big bag of woo?

a reply to: And Why

Sorry, no.

The dimmest star the naked eye can see is around +6.0 magnitude.

At 33 light years away, the sun would appear as a +4.8 magnitude, visible to the naked eye.

The sun would be just visible to the naked eye at about 50 light years.

After that, you'd need a telescope to see it.

Give a telescope a large enough mirror and you'd be able to see things that are very, very dim.

Using a pair of binoculars, you can see things as dim as +10 magnitude.

With a 50cm telescope, you can see things as dim at +15 magnitude.

Ah...but now we switch to a digital camera hooked up to a telescope and make the telescope even bigger.

How about 150cm? Your camera would catch things as dim at +22 magnitude.

Now yes, if there is something in the way, say a nebula cloud, it would block the visible light. But as long as it's not blocked, and you have something that is big enough to collect the light (large telescope) and something that can be very sensitive to light (digital camera), you'd be able to see the sun from very, very far away.

originally posted by: And Why

originally posted by: Soylent Green Is People
-- If the aliens lived within 100 Light Years of Earth (which is practically next door in galactic scales) them they could potentially be able to detect our radio waves -- although the signal would be very weak 100 LY out.


-- If the aliens lived, say 250 light years or so away (still pretty much in in our galactic neighborhood), then a spectrographic analysis of the light from our atmosphere might allow them to detect the industrial gases in our atmosphere our civilization has been producing since about the industrial revolution, which would be another sign to them that Earth has a civilization of some kind.


-- If the aliens lived, say 2000 light years or so away, which is still only about 2% of the way across the galaxy, then a spectrographic analysis of the light from our atmosphere might allow them to detect the burning of wood in our atmosphere that they might perceive as a sign to them that Earth has a some kind of intelligent life that has harnessed fire -- but would not necessarily be a technological civilization.

A radio wave would still take 100 years to travel 100 light years and would likely not even be able to be detected due to the medium of space it travelled trough. Cosmic radiation and other noise would distort it.

Yes -- Like I said, the signal would be very weak. A large radio antenna would be needed to receive it as anything more than just noise. A dish larger than Arecibo or the new Chinese FAST 500-meter dish would probably be needed, but there is no reason to believe that such a radio telescope is impossible.

At 250 LY the light from the sun is not detectable, so a spectrographic analysis of the atmosphere of earth is laughable sci-fi handwaving magic from too much TV/Film. Might as well use the force.

Telescopes are not "laughable sci-fi handwaving magic".

Obviously, telescopes can see stars that are too dim to see by our eyes. We can easily see (and analyze) the light from sun-like stars that are 200 LY away with our current visible light telescope technology.

If we were 200 LY away from the Sun, we would be able to look back and see the Sun using the visible light telescopes that we currently have.

At 2000 LY who the # is even going to know that earth exists if the sun is a dark spot in the blackness of space. Where is this spectrographic magic from, what Show/movie on youtube sold this big bag of woo?

Similar response to the one above. We can see (and analyze) the light from sun-like stars that are 2000 LY away with our current visible light telescope technology.


In fact the Kepler space telescope has found several planets orbiting sun-like stars that are 2000 LY away or more. And Kepler uses the "Transit" method to find planets, so by definition of the "Transit Method", Kepler was able to detect the light from those sun-like stars that were 2000+ LY away.

a reply to: And Why

Another way to figure it out is to use the Distance Modulus formual:

m-M = 5 log r - 5

M = absolute magnitude.
m = apparent magnitude.
r = distance in parsecs

1 parsec = 3.26 light years.

So, we know the sun's absolute magnitude is 4.8, and we also know that the dimmest star the human eye can see is +6.0.

and to find the answer we can move the equation around:

(m-M)/5 + 1 = log r

Convert the log to an exponent:

r = 10^((m-M)/5+1)

Plug in our numbers:

r = 10^((6-4.8)/5+1)

Then do the math (make sure you stick with the order of operations), and you get:

r = 13.378 parsecs

13.378 x 3.26 = 43.633 light years.

That's pretty darn close to 50 light years.

That's with the naked eye.

So let's change it up a bit, let's go with that 150cm telescope and a digital camera with a really sensitive CCD sensor. We'll say +22 magnitude is the limit for that set up. How far would be the farthest to detect the sun's light?

Do the math again:

r = 10^((22-4.8)/5+1)

r = 27542.287 parsecs

or

r = 89,830.925 light years

So someone, on some planet, with a really good telescope and camera equipment would be able to detect the sun from almost 90,000 light years away, as long as there was no interstellar dust in between the two of us.

a reply to: RAY1990
The trouble is with burying your head in the sand is your ass is sticking up and you wont see when they come to shaft you. Why does everyone assume all the while that any aliens will be hostile. Judging a different species with our own failings is the height of hypocrisy.

originally posted by: AnkhMorpork
a reply to: Xeven

Determining the size and motion of the moon or an exomoon
that exhibits the same properties as Earth's wobble, I think would do it, along with an atmospheric spectroscopy revealing a similar composition to Earth's. Even if it were to turn out to be a water world without surface landmasses, that would about do it I think.

Single Giant moon in similar proximity and configuration would be helpful to produce another Earth-like world.

We've only just proved that there is water inside the mantle of the moon. And that is from lunar samples from the 1970's.

news.nationalgeographic.com...

We also know that there are underground lava tubes on the Moon's surface, so therefore, there must be underground caverns as well. And they could retain water.

Yeah, I did not think it a good idea to do so. I was more or less fishing for a way to detect life out there by thinking about the problem in reverse.

How do we notify the universe we are here? If we figure that out we might figure out what to look for out there to find other life.

Seems like finding anything beyond 50ly is pretty bleak unless we learn to fold space or something

originally posted by: Xeven
Given our current technology is there anyway we can highlight our Solar System as having life?

Put up a big sign that says, "ALL YOU CAN EAT FREE!"

originally posted by: RAY1990
Eventually it'll end up with a bitter ending. We won't last forever on earth.

Our sentient robots will be taking over pretty soon, too. And maybe they'll have a better chance at interacting with any aliens (if there are any). They could certainly go into "stand-by" mode and ride a slow rocket to nearby stars a lot easier than we could. In a few thousand years, they could be crawling all over the galaxy.

No, we're not built for long space travel. Science killed that buzz for us.

How about nuclear explosions which emit gamma rays? We've detected a lot of strange stuff out there like the planet that appears to have a Dyson sphere around it. I would think that if anyone out there had advanced detector technology, that they would have detected something from this sector - perhaps not our exact location - but just like us speculating on interesting finds, they probably suspect there's something out there.

Watching Nuclear War From Across the Galaxy
With the right telescope and a lot of luck

A team of astronomers recently tried to determine whether Trinity’s light might be cosmic in a different sense. The Trinity test involved only one explosion. But if there were many more explosions, involving many more nuclear weapons, it might generate enough heat and light to be seen from nearby stars, or from the deeper reaches of our galaxy—so long as someone out there was looking.

www.theatlantic.com...


Observational Signatures of Self­Destructive Civilisations

1epartment of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK15
0BT
2: UK Centre for Astrobiology, University of Edinburgh, Edinburgh, EH9 3FD
3: SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St
Andrews KY16 9SS
4: Carl Sagan Institute, Department of Astronomy, Cornell University, Ithaca NY, 14853

arxiv.org...

What we need for close up inspection of exo-planets, both in the visible and electrochemical, radiowave spectrum, that would allow us to determine if we were looking an a truly Earth-like world, is a GAINT TELESCOPE in orbit around the sun not far from Earth, maybe even exploiting the three-body dynamics of the Earth, moon and sun, to stabilize it.

What's needed is a baseline of such telescopes who's images are combined using parallax. You could run it in collaboration with earth-based systems like the Square Kilometer Array in Australia and South Africa, and use super computers to track all the incoming data of the Galactic Survey.

This is coming on stream in the next 10-20 years (the SKA), so most of us or many of us (touch wood) are apt to see the day in our own lifetime.

But if they want to probe deep space on a relatively affordable budget (think of what could have been done with the 4 trillion spent on the unnecessary wars of late) - they should expedite it and add the deep space radio and optical telescope(s) components. Think 12 Hubbles and radio telescopes with a 144X power over that of the Hubble or any radio telescope on Earth at this time, maybe higher, maybe 1000X..

It's a no brainer.

This would give us access to deep space (with an "eye" bigger than the whole earth), over an above a complete and total survey of the Milky Way Galaxy, with the ability to identify other Earth-like worlds, even if to get a true Earth-like world, with a stable, temperate climate and liquid water over 90% of the surface, while retaining what for an inner planet is a relatively high rate of rotation, and without tidal locking, will require an almost identical earth-moon-sun configuration.

Multiple small moon systems, or even life on exo-moons, where it exists is likely to occur in bands on such worlds, where one half the planet might be continually engulfed in storms, or frozen, depending on it's tilt and orientation to it's host sun.

Earth is a true wonder, and such worlds would be exceedingly rare.

If the galaxy is an evolutionary spiral, then we're probably more apt to find such worlds around the same perimeter on the various galactic arms, and that's where we should be looking I think when we get the glasses to really look and hopefully to find and discover including the discovery that Earth is a true marvel and wonder due to it's particular if not entirely unique Earth-Moon-Sun configuration.

The aliens would simply use an "eye" the size of our solar system, to find them all, or maybe they know how to map spacetime and the zero point field to predict precisely where such worlds will exist, then zero in on them.

Nothing like actually going there for a soil sample and a cow tongue though..

a reply to: Xeven

And if you could, would you want to?