I think the parameter for the number of planets that can potentially support life per star that has planets may be far larger than past estimates. The basis of this idea is related to atmospheric pressure. It is possible that the earth's atmospheric pressure is very low compared to most planets of it's mass in the galaxy.
The theory that a collision of the Earth with an object the size of Mars in the past created the moon and ripped off much of the earth's atmosphere may explain the anomaly of why less massive Venus has a much higher atmospheric pressure than Earth. Saturn's moon Titan is much less massive than Earth and has an atmosphere that is denser than Earth's.
You need higher atmospheric pressure for liquid water on planets or moons that are located in Goldilocks zones of solar systems.
Typically in the Universe smaller astronomical objects
are more numerous than larger objects, so there are more chances that smaller bodies with atmospheric pressures near Earth's will be in the Goldilocks zones.

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I think the parameter for the number of planets that can potentially support life per star that has planets may be far larger than past estimates. The basis of this idea is related to atmospheric pressure. It is possible that the earth's atmospheric pressure is very low compared to most planets of it's mass in the galaxy.
The theory that a collision of the Earth with an object the size of Mars in the past created the moon and ripped off much of the earth's atmosphere may explain the anomaly of why less massive Venus has a much higher atmospheric pressure than Earth. Saturn's moon Titan is much less massive than Earth and has an atmosphere that is denser than Earth's.
You need higher atmospheric pressure for liquid water on planets or moons that are located in Goldilocks zones of solar systems.
Typically in the Universe smaller astronomical objects
are more numerous than larger objects, so there are more chances that smaller bodies with atmospheric pressures near Earth's will be in the Goldilocks zones.

If I understand your post correctly, you're saying that Earth's atmospheric pressure might be freakishly low for planets of its size and that a typical planet with our sort of atmospheric pressure might be substantially smaller. That's an interesting thought. There's problems with that theory, though.

A planet needs to be massive enough to hold on to the gases in its atmosphere, and the closer it is to its star the more massive it has to be. This is because the individual molecules of gas are in constant random motion and the speed of the motion depends on the mass of the molecule and on the temperature of the gas. Some molecules will actually travel faster than the escape velocity of the planet and can escape from the atmosphere. Earth itself can only hold on to relatively heavy gases like nitrogen, carbon dioxide and oxygen whereas the light gases like hydrogen and helium have escaped long ago. Titan can hold on to its thick atmosphere of nitrogen because it is so cold; if it was magically transported to Earth's distance from the usn, it would blow off relatively quickly.

Another factor is the solar wind. UV rays from the sun can break water molecules into single ions of hydrogen and oxygen, which are charged particles. The solar wind, which is also charged, then picks up these ions and strips them from the atmosphere. Earth's magnetic field protects our water molecules from this fate. Venus and Mars, which have vitually no magnetic field, have also lost most of their water. Now, the reason mass is important here is that to have a magnetic field a planet needs a spinning, liquid, iron rich core. Mars is too small- its core has cooled faster than Earth's and is now only partially liquid, and no longer generates a magnetic field. Venus is the right size but is spinning too slowly for the dynamo effect to work.

I think the parameter for the number of planets that can potentially support life per star that has planets may be far larger than past estimates. The basis of this idea is related to atmospheric pressure. It is possible that the earth's atmospheric pressure is very low compared to most planets of it's mass in the galaxy.
The theory that a collision of the Earth with an object the size of Mars in the past created the moon and ripped off much of the earth's atmosphere may explain the anomaly of why less massive Venus has a much higher atmospheric pressure than Earth. Saturn's moon Titan is much less massive than Earth and has an atmosphere that is denser than Earth's.
You need higher atmospheric pressure for liquid water on planets or moons that are located in Goldilocks zones of solar systems.
Typically in the Universe smaller astronomical objects
are more numerous than larger objects, so there are more chances that smaller bodies with atmospheric pressures near Earth's will be in the Goldilocks zones.

If I understand your post correctly, you're saying that Earth's atmospheric pressure might be freakishly low for planets of its size and that a typical planet with our sort of atmospheric pressure might be substantially smaller. That's an interesting thought. There's problems with that theory, though.

A planet needs to be massive enough to hold on to the gases in its atmosphere, and the closer it is to its star the more massive it has to be. This is because the individual molecules of gas are in constant random motion and the speed of the motion depends on the mass of the molecule and on the temperature of the gas. Some molecules will actually travel faster than the escape velocity of the planet and can escape from the atmosphere. Earth itself can only hold on to relatively heavy gases like nitrogen, carbon dioxide and oxygen whereas the light gases like hydrogen and helium have escaped long ago. Titan can hold on to its thick atmosphere of nitrogen because it is so cold; if it was magically transported to Earth's distance from the usn, it would blow off relatively quickly.

Another factor is the solar wind. UV rays from the sun can break water molecules into single ions of hydrogen and oxygen, which are charged particles. The solar wind, which is also charged, then picks up these ions and strips them from the atmosphere. Earth's magnetic field protects our water molecules from this fate. Venus and Mars, which have vitually no magnetic field, have also lost most of their water. Now, the reason mass is important here is that to have a magnetic field a planet needs a spinning, liquid, iron rich core. Mars is too small- its core has cooled faster than Earth's and is now only partially liquid, and no longer generates a magnetic field. Venus is the right size but is spinning too slowly for the dynamo effect to work.

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The Drake Equation: Adding a METI Factor:

http://www.setileague.org/editor/metifact.htm




.

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"Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind." - Dr. Seuss

A planet needs to be massive enough to hold on to the gases in its atmosphere, and the closer it is to its star the more massive it has to be.

This is a little off the subject but I've often wondered if toward the end of the formation of the sun, the inner planets, especially Mercury, might have actually been gas giants. Mercury is the densest planet in the solar system and could have captured a lot of the gas that was falling toward the sun.

It makes sense that the closer a planet is to its star, the more gas would be available to it during the formation of its solar system. Then when the early sun started radiating - a lot more furiously than it does today - the inner planet atmospheres would be largely blown away toward the outer solar system. Maybe what once was Mercury's is now Jupiter's, leaving Mercury a bare little nut of nearly solid iron.

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I really think it's time to rename the "Drake Equation" to something like "Drakes guess".

There is no science to back up any of this. NONE at all.

It's just a guess.

I really think it's time to rename the "Drake Equation" to something like "Drakes guess".

There is no science to back up any of this. NONE at all.

It's just a guess.

The equation itself is perfectly legitimate. It's the values of some of the parameters that are guesses.

Akhenoten, I enjoyed your post of several paragraphs where you described atmospheric densities in relation to planets' positions in orbit among other factors. Haven't considered those things before. Thanks.

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Founder of BOINC team Objectivists. Oh the humanity! Rational people crunching data!
I did NOT authorize this belly writing!