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The Drake Equation Revisisted

dryson

GROUP: Members

POSTS: 749

Report this Sep. 07 2013, 11:46 am

http://www.space.com/22648-drake-equation-alien-life-seager.html


Astronomers have found that 6 percent of all red dwarf stars have an Earth-sized planet in the habitable zone, which is warm enough for liquid water on the planet’s surface. Since red dwarf stars are so common, then statistically the closest Earth-like planet should be only 13 light-years away


I would have to add that a White Dwarf in close proximity to an Earth like planet orbiting a Red Dwarf would make for a better case of the planet being habitable or already having life present on it.


White Dwarfs emit oxgen and carbon that are two of the main factors involving life as both components are present in every living creature on Earth.


Once the oxygen and carbon molecules would reach the Earth like planet orbiting the Red Dwarf they would cool to the point of being able to be combined with other molecules necessary to create life with the Red Dwarf providing enough warmth to keep things moving around where life would be chase other life and consume it for energy instead of such molecules being frozen and remaining dormant without any activity.

eutychus

GROUP: Members

POSTS: 124

Report this Sep. 09 2013, 6:07 pm



In the '50s an astronomer named Frank Drake came up with what is known as the Drake equation to calculate the potential planets in our galaxy capable of supporting life as we know it. The equation goes as follows:

N* x fs x fp x ne x fi x fc x fl = N

N*= stars in our galaxy
fs= fraction of sun like stars
fp= fractions of stars with planets
ne= planets in a star's habitable zone
fi= fraction of habitable planets where life does arise
fc= fraction of planets inhabited by intelligent beings
fl= percentage of a lifetime of a planet marked by a communicative civilization
N= numbers of planets with intelligent life
Keep in mind that little was known regarding most of these variables in the 50s. There was no Hubble and there was no estimation of planetary masses orbiting around other stars so many assumptions were made.

By the late 90s, evolutionary biologists Peter Ward and Donald Brownlee revised this equation to place it more in line with current understandings of cosmology. They have named this updated equation the Rare Earth Equation.

N* x fp x fpm x ne x ng x fi x fc x fl x fm xfj x fme = N

N*= stars in our galaxy
fp= fractions of stars with planets
fpm= fraction of metal rich planets
ne= planets in a star's habitable zone
ng= stars in a galactic habitable zone
fi= fraction of habitable planets where life does arise
fc= fraction of planets with life where complex metazoans arise
fl= percentage of a lifetime of a planet marked by the presence of complex metazoans
fm= fraction of planets with a large moon
fj= fraction of solar systems with Jupiter-sized planets
fme= fraction of planets with critically low mass extinction events
N= number of planets with intelligent civilizations

Ward and Brownlee admit that this is a sketchy equation, though less sketchy than Drake's. They have left out some factors whose effects can't as yet be determined, such as the effect of repeated ice ages, and inertial interplay between celestial bodies within a solar system. But they contend that even from sparse data a general signal may be perceived. And yes, this is using Earth as a model for a life bearing planet. Terra-centric perhaps, but it's the only model available to us. And as with any equation, when any term in the equation approaches zero, so too does the product. Earth may be one of a very few planets capable of supporting life. Admittedly, this model presupposes animal life. I am fully aware that there could be types of life that would not fit any definition we use (It’s life, Jim, but not as we know it!). I really think that life is the exception rather than the norm, even by evolutionary standards, which do not presuppose a creator with a bias towards life. I personally lean towards a designer rather than chance.


 


Now to the explanation of the terms-


 


N*- we will limit our discussion to this galaxy. Isn’t that a big enough sample?


fp- not all stars will have planets. A star must be of sufficient mass for planets to form and then hang around after their formation.


fpm- if the star from which planets form is not metal-rich, planets with an outer lithosphere upon which water may form are not likely.


ne- There is a very narrow band around any star that will constitute a habitable zone. Any planet forming outside this zone is not likely to have liquid water. Prospects for life are not good.


ng- there are places in the galaxy that are less conducive to the formation of life. Anywhere life formed in the galactic core where radiation is much more intense, they would have to develop sunscreen with an spf of several million long before the wheel.


fi- life simply is not going to happen everywhere. Water won’t form every time a planet in the right place does.


fc- bacteria may be living, but if they never organize professional sport teams, are we really going to consider them alive? If the basic portions of life do not gain complexity, creatures of even greater complexity may never arise.


fl- complex  metazoans that die out the first time the tide rises a little too high simply don’t have the stuff required to make it any further up the food chain.


fm- If there is no moon, there are no tides, and tidal pools are thought to be likely pots in which life potentially ferments. Also, the moon takes a lot of hits intended for us. There are no seas on the dark side. Just lots of meteor strikes.


fj-You need a large gravity well farther out in a solar system to attract objects capable of crossing the orbit of a life bearing planet at the wrong time. Note the Shoemaker-Levy comet impact on Jupiter in the early 1990s.


fme- too many mass extinction events will eventually wear down any life form to the point where it finally gives up trying.


A cassette guy in an I-pod world

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