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Robin Bland

Update to the Drake Equation?

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Come across this and thought it was interesting. The fact that we only have human civilization as a comparison always makes me laugh. 

https://www.inverse.com/article/14957-drake-equation-revision-hugely-ups-odds-intelligent-extraterrestrial-life-exists

 

Frank Drake authored that equation back in 1960, and yes, considering the wealth of information we've received from Kepler, Hubble and tremendous advances in extrasolar planet discovery (thousands of confirmed exoplanets since 1995), I would imagine it's more than time to dust off some of those musty old variables.   And if we discover life beyond Earth within our own solar system (such as subsurface life on Europa or Mars), the odds of life throughout the universe double

Very exciting time to be an astronomy (or astrobiology) geek! :thumbup:

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In physics, a theory is not like a theory in literature, but is a testable series of opinions based on educated guessing, or something like that. The Drake Equation is outdated as back then nobody had actually confirmed any extrasolar planets. Of the thousands we have measured by the two basic methods, the orbits (transit?) and wobbles of stars and dip in light (brightness?) ones, only a few are in line with us to see, well not see, detect, and even fewer are in the habitable zone.

This equation is mathematical, but I am not so good at math. Anyway, I figure the equation is part of a theory about the presence of life in the universe. Since it is a thought experiment, until ET shows up there is no way to prove it. Even if ET did show up, it would be one species, making it possible for there to be many more. (I am ignoring the conspiracies about UFO's because that would not enter into the equation, as it is not theory but is just not provable, ergo nobody has actually captured an alien saucer or pilot, not really). It would not be applied to the equation.

Given the tens of millions of stars in our barred spiral galaxy, and given the location that the sun orbits within it, in a green zone of its own, not too far out, not too close to the center, there should be thousands if not tens of thousands of stars with some form of life, if not more, and on some of them, maybe hundreds, maybe more, advanced civilizations beyond us.

However, civilizations like ours, 0 on the Karashev scale, there are likely hundreds of thousands, never able to visit us but out there.

I have wondered if the SETI group is just not using the right instruments to detect them. Surely one of those close by stars used something like radio, but what if they didn't?

 

 

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 Of the thousands we have measured by the two basic methods, the orbits (transit?) and wobbles of stars and dip in light (brightness?) ones, only a few are in line with us to see, well not see, detect, and even fewer are in the habitable zone.

^ That's not entirely accurate; the dip in starlight when a planet crosses it's disk is called the Transit method; the 'wobble' is Perturbation (the measure of gravitational influences on a star by something other than another massive body; i.e. something 'planet-sized.').  

But there are many more methods of indirectly measuring/observing extrasolar planets; such as ellipsoidal variations (to measure the orbit length/distance), relativistic beaming (light variations from a 'tugged' star), pulsar timing, gravitational micro-lensing (an ability predicted by Albert Einstein), and many more.

There is also (when conditions are just right) the Direct Imaging method.  So far, only a few planets have been directly imaged near their relatively dim parent stars; such as this extrasolar planet orbiting the brown dwarf of HD3651 (below):
 

061019192358_1_540x360.jpg

I have wondered if the SETI group is just not using the right instruments to detect them. Surely one of those close by stars used something like radio, but what if they didn't?

^
That's old SETI; I used to donate to SETI and the radio searches are just one method.  There is also SETI Optical; which uses laser optical messaging.  SO not only has the advantage of broadening a beam the further out it goes, but it also doesn't have the rapid signal degradation of radio waves.  

There is also the possibility that radio or optical means may not be so 'obvious' to other lifeforms.  

What if the intelligent life were similar to our marine life here on Earth, such as whales or dolphins?  Intelligent creatures but without hands, opposable thumbs or the ability/habitat to create/harness fire and technology?   Or... maybe we're the only species in the immediate stellar neighborhood to use something as quaint and old fashioned as radio.   

But SETI's been at it for quite a while now; it's safe to say that if a comparable technological species to ours within 40 light years of us were transmitting in analog radio or television formats?  SETI might have heard something by now.   Still, 40 light years out from Earth is bubkes in a galaxy that is 100,000 light years across.  Then again, even our own planet no longer uses analog television transmission since everything went digital, so who knows?   Maybe they 'went digital' 10,000 or 50,000 years ago...?

 

 

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Hammer   

I'm doing a radio communications course right now so just for fun I calculated the Free Space Path Loss between Earth and Trappist-1. 

FSPL (general formula) = 32.44 + 20LOG(distance in Kilometers) + 20LOG(frequency in MHz)

FSPL(to Trappist) = 32.44 + 20LOG(3.737*10^14 KM) + 20LOG(1420 MHz) = 386.9 dB of loss

Roughly every 3dB of loss halves the power of the signal.

10 LOG (x) = 386.9 dB

10^(386.8/10) = x  (Free Space Path Loss in ratio)

x = 4.786 * 10^38  so a signal leaving Trappist-1 would be 4.786 * 10^38 times less powerful when it reaches Earth.

Of course, there are other factors at play. The source transmission could be in Megawatts (10^6 Watts) and we can pick up picoWatts (10^-12 Watts) just fine. The larger the receiving dish, the larger the gain in dB which would cancel out some of the FSPL. 

The way some people talk though, it's like the general public thinks we can just point a dish at some far away object and we should be receiving their TV programs. Not only could their transmitters be too weak, they could be broadcasting at other frequencies that we aren't scanning. SETI just picked 1.42 GHz because there is less interference from interstellar gas at that frequency. They could be broadcasting at 10 GHz and we wouldn't see it. We use radio bands from the 8 KHz range up to around 275 GHz so it's likely that another civilization would use the whole spectrum too.

 

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So they need to get cracking and build a lunar station observatory that would be free of interference, scan the whole spectrum, and sill is some alien tv. But since spam is the universal constant on the current digital internet, they would likely send us theirs in return, and their shipping stories and cat videos. But what they call a cat might be a 9 foot teddy bear with six inch fangs.

Edited by Chimera82405

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Hammer   
On 3/11/2017 at 11:13 AM, Chimera82405 said:

So they need to get cracking and build a lunar station observatory that would be free of interference, scan the whole spectrum, and sill is some alien tv. But since spam is the universal constant on the current digital internet, they would likely send us theirs in return, and their shipping stories and cat videos. But what they call a cat might be a 9 foot teddy bear with six inch fangs.

Although we can't do anything about the massive free space path losses, the bigger the receiving dish, the larger the gain. As dish receiver gain increases, weaker signals can be detected. The radio astronomy dishes are massive, the largest one is in China and is 1/3rd of a mile across. There's no way they are building something that big on the Moon in the foreseeable future. 

Also, we aren't even close to scanning the entire spectrum in every direction. They picked a small chunk of the spectrum which experiences less interference called 'the water hole'. All that received data needs to be crunched by computers using complicated math called FFT's, this isn't like tuning in your radio and hearing a voice or music... 

If you want to help out the effort, download the BOINC screensaver and help crunch radio telescope data for SETI@Home. Perhaps your computer screensaver will find ET.

http://boinc.berkeley.edu/

https://setiathome.berkeley.edu/#

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