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Now that we know how to detect exoplanets by their effect on the star's wavelength, what are the implications to the Drake equation? [1]

Originally, we estimated that habitable planets were very rare. Then we discovered exoplanets, and soon after, habitable exoplanets.

Drake also started by looking for radio signs of intelligent life. Now we humans use frequency-hopping burst digital transmissions and the power level is much lower, so detecting another planet by its radio signature seems a lot less likely.

Since earth has been habitable for at least 3 billion years [2], what is the probability that intelligent life (in our galaxy) is aware of this planet and wants to look at it? My back-of-napkin estimate is that we are out on a limb of the galaxy and therefore very visible.

[1] http://en.wikipedia.org/wiki/Drake_equation

[2] http://en.wikipedia.org/wiki/History_of_Earth

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> "what are the implications to the Drake equation?"

I'm not a fan of the Drake Equation. The "equation results" section of the wikipedia page shows the range of variability: there may be anywhere from hundreds of millions of civilizations in our galaxy, to maybe we're the only one in the entire universe (a difference of close to 30 orders of magnitude), based on different guesses for some of the other parameters. Both sets of numbers are using the current understanding that we can discover exoplanets etc. and that they're not terribly rare. Prior to that understanding, estimates varied by another 5-10 orders of magnitude.

In other words, these newer discoveries don't get us particularly close to a definitive answer from the Drake Equation. We still don't know whether there's intelligent life at millions of stars in each of billions of galaxies, or if it's possibly just us.

The only sort of data that would let us actually use it to generate a meaningful answer would be the discovery of more intelligent life.

> The only sort of data that would let us actually use it to generate a meaningful answer would be the discovery of more intelligent life.

Yes but since we don't have any of those discoveries the Drake equation is really the best we can do right now.

I think what he is saying is that the Drake Equation does not get us anywhere useful. A theory that has such a wide range of outcomes does not eliminate much - and most science is eliminting options not demonstrating a truth.

In fact the less-than-helpful results are a useful reminder of Karl Poppers maxims

'Trying is the first step to failure'

-- Homer Simpson

The Drake equation was meant to be illustrative; lowballing everything (particularly the L term, since we were in the midst of the maddest of MAD at the time) and still coming up with a non-zero value was really the point. As long as what you're plugging in isn't on the order of "the Scriptures say it can't be, therefore it's zero", you will arrive at a non-zero value, and that makes at least the attempt to find and make contact with other technological civilizations reasonable.

> "coming up with a non-zero value was really the point."

When you're multiplying a bunch of non-zero quantities, that's the only possibility. It's not really illustrative or useful, though -- particularly because the range of possible estimates still includes "we are alone in the universe".

You don't need the Drake Equation to tell you that it's reasonable to explore and search.

One thing we can still be very confident about: if there is other life out there, it's not significantly any more intelligent than we are. (See Robin Hanson's Great Filter argument: http://webcache.googleusercontent.com/search?q=cache%3Ahttp%...)

Maybe I missed it but may I suggest one extra filter to be applied - once a civilisation reaches a level of technological sophistication, it finds the base code for the matrix, works out how to dial out and leaves, going up to the pan-galactic teenagers bedroom we are running in.

Thus the answer to Drake and the filter question is no one is around because there is an exit to a more interesting universe.

You've sparked two thoughts in me:

1) "I truly wish I could answer that question." - Having recently re-kindled an interest in space left dormant since childhood, I'm thinking this is the kind of thing I could happily dedicate my life to.

2) "I wonder if a hybrid of Google Answers and Kickstarter to answer this kind of interesting question could thrive?" - Apparently, there have been a few attempts at the latter part at least[1][2], but the list of projects is pretty short. Crowd-funded research with open-access findings seems like potentially wonderful thing.

1: http://www.petridish.org/projects/all

2: http://www.iamscientist.com/projects

What kind of periodic wobble would our Sol produce from our very-many body solar system? Would it be easy to decipher, or easier to catalog as background noise?

Maybe we'll start seeing advances in telescopic technologies and analyses in the years to come -- to pick up on more complex periodic motion of the more complex solar systems.

Just got me thinking, there might be some interesting results from making these kind of observations from say Voyager distance and scaling the resolution of the measurements accordingly to match our results of far more distant system.

Not knowledgable enough in the area to know if this would be worth doing.

If a clone of our Solar System were out in space our chances of detecting it would be extremely low.

In order to detect Venus or Earth it would require around a 1 in 100 chance alignment of the orbital plane relative to the observer to be detectable via the transit method. Jupiter would be detectable through radial velocity techniques but it would take a minimum of 12 years to confirm a single orbit and more likely it would take at least 2 orbits for a proper confirmation. And even so it would be a coin flip on whether the orbital plane was aligned properly to be detectable at all.

With the increased sensitivity of the new instrumentation used to detect the Alpha Centauri B planet things are improved slightly but still the chances of detecting an Earth-clone via radial velocity aren't that great.

Where are you getting your chances from? Is there some theoretical limit on the sensitivity of the radial velocity technique, independent of current technology?

(edit): This spectrometer is supposed to be capable of detecting an earth-clone, starting around 2016:

http://en.wikipedia.org/wiki/ESPRESSO

This graph shows its predicted sensitivity (green line for a sun-like star), compared to exoplanets previously detected by the same method (gray circles), and solar system planets for reference:

http://espresso.astro.up.pt/images/content/science/image012....

http://espresso.astro.up.pt/science.php?show=chapter3

You can get a rough estimate of the chances of being able to observe a planet via the transit method by dividing a star's diameter by half of the orbital diameter of the planet (for Earth it's something like a 1:300 chance).

For radial velocity the signal detected is proportional to the sine of the orbital inclination. The detectability of Jupiter depends highly on which instruments are being used for observation. My "coin flip" estimate was just a SWAG. If you make use of the best radial velocity detection systems today which have a sensitivity of around 1 m/s and compare that against the maximum 13 m/s radial velocity that Jupiter imparts on the Sun then you end up with much higher chances of detection (80+%) assuming a random relative orbital inclination, but that assumes there aren't any other sources of noise involved.

With one star, they teased out nine different planet orbits from its wobble:

http://en.wikipedia.org/wiki/HD_10180

This is the Fermi Paradox ( http://en.wikipedia.org/wiki/Fermi_paradox ). The more we learn about space, the more clear it becomes that extraterrestial life is more likely. But where the hell are they?!

The estimated number of potentially habitable planets (planets within the goldilocks zones of their stars) is enormous.

https://www.youtube.com/watch?v=SMUDXO4xkW8

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