Two Plus Two Older Archives  

Go Back   Two Plus Two Older Archives > Other Topics > Science, Math, and Philosophy

Reply
 
Thread Tools Display Modes
  #21  
Old 12-28-2005, 11:20 AM
hmkpoker hmkpoker is offline
Senior Member
 
Join Date: Jan 2005
Location: New Jersey
Posts: 116
Default Re: Book: Rare Earth: Why Complex Life is Uncommon in the Universe

[ QUOTE ]
You wouldn't accept that a car just fell together, you know that it was designed.

[/ QUOTE ]

No, but I can pretty easily accept that a tree did. Trees seem to come about in the absence of a creator.
Reply With Quote
  #22  
Old 12-28-2005, 01:46 PM
Guest
 
Posts: n/a
Default Re: Book: Rare Earth: Why Complex Life is Uncommon in the Universe

[ QUOTE ]
Let me explain something to you godboy. Your arguments are correct. Thje philosophers who are trying to refute you are incorrect. You are wrong in your conclusions but not for the reasons these philosphers talk about. Rather it is because of the fact that the miraxculous things you see around you are NOT nearly as unlikely or coincidental as they appear to the scientifically uneducated. A simple example is the beauty of bubbles or snowflakes or mountains. Same goes for your eclipse example.

Believe me if you were arguing with physicists or molecular biologists rather than philosphers, you would no longer feel that your ideas are on firm ground.

[/ QUOTE ]
This is one my favorite posts of yours.

Of course, it's a fact that all life today evolved from single cells a long time ago. Only those ignorant of biology say otherwise. The evidence is simply overwhelming and irrefutable.

But you have to admit that currently, abiogenesis (random molecules -> first cell) looks like a long shot. There are several stages in this process that we can't find a plausible mechanism for. Of course the dots will be joined eventually (just look at the history of biology), but until then we must concede that it does appear highly improbable. The theists still get to put their "God of the Gaps" in there for now.
Reply With Quote
  #23  
Old 12-28-2005, 02:16 PM
TimM TimM is offline
Senior Member
 
Join Date: Jan 2004
Location: New York
Posts: 147
Default Re: Book: Rare Earth: Why Complex Life is Uncommon in the Universe

[ QUOTE ]
But you have to admit that currently, abiogenesis (random molecules -> first cell) looks like a long shot. There are several stages in this process that we can't find a plausible mechanism for. Of course the dots will be joined eventually (just look at the history of biology), but until then we must concede that it does appear highly improbable.

[/ QUOTE ]

Not at all. Even the authors of Rare Earth admit that this process occurred very quickly on Earth - nearly the exact instant that life became possible, on a geologic timescale. There is a good chance that independently evolved microbial life is present on several other bodies in our own solar system.

Note that anyone using the Rare Earth hypothesis to argue for intelligent design is arguing for a flavor of ID where some creator simply set the initital conditions of our solar system (or the entire universe) in such a way that we would evolve.

Some have argued that even if we accept the Big Bang theory, we have to believe it was caused by an intelligent creator, since had the physical constants of our universe varied by the slightest amount, life would not be possible. But again this proves nothing. For example, our (finite) universe could be part of an infinite meta-universe where universes are randomly created with every possible set of initial conditions. And, of course, only the ones with perfect physical constants get noticed.
Reply With Quote
  #24  
Old 12-28-2005, 05:51 PM
David Sklansky David Sklansky is offline
Senior Member
 
Join Date: Aug 2002
Posts: 241
Default Re: Book: Rare Earth: Why Complex Life is Uncommon in the Universe

"What do have to say about the physicists or molecular biologists in support of the intelligent design theory?"

Of those who have Nobel Prize type qualifications few, if any believe in ID. And those who do, believe it for different reasons than your flawed probabilistic ones.
Reply With Quote
  #25  
Old 12-28-2005, 09:45 PM
TimM TimM is offline
Senior Member
 
Join Date: Jan 2004
Location: New York
Posts: 147
Default Re: Book: Rare Earth: Why Complex Life is Uncommon in the Universe

Bad Jupiters, no Jupiters?

Are planets like Jupiter rare or common? Are they necessary for complex life to evolve in a system, yet more likely to be detrimental than helpful?

The authors argue that a large Jupiter-like planet in a stable, fairly distant, circular orbit is necessary for complex life to develop on one of the inner planets of a system. Such a planet would sweep the inner solar system leaving it relatively clean of many of the comets and asteroids which could sterilize the planet by collision. I am going to argue that Jupiter sized planets in orbits exactly where the are needed may be common. But it is also possible that without a Jupiter, it would simply take longer for the early bombardment of a new planet to slow down enough so that life can develop. Right now this is just speculation but perhaps it could be tested with computer simulation. In any case it does allow for the possibility that nearby Jupiter sized planets are not an absolute necessity for complex life.

Ward and Brownlee cite the fact that, so far, all programs to detect extra-solar planets have found only Jupiter sized planets in either very close or very elliptical orbits around their star. These so called "bad Jupiters" should interfere with any planets in a star's habitable zone enough to prevent the possibility of complex life forming there. But the reason these are the only extra-solar planets we detect, is that they are the only kinds we could detect at the time Rare Earth was written. We see these bad Jupiters in about 5% of the nearby star systems, while in the remaining 95% we detect nothing. The authors admit it is quite possible that many of the remaining 95% have planetary systems similar to our own, since we cannot detect those at the distances of nearby stars.

Finally, theories of planet formation suggest that Jupiter like planets will form exactly where they are needed to support life on the inner planets: just outside the star's habitable zone, and the ones that are in closer or more elliptical orbits are those that migrate there by chance gravitational interactions.

"In disks as massive as the minimum-mass disk for the Solar system, gas giants can form only slightly outside the “ice boundary” at a few AU."

"We also examine the dynamical evolution of protoplanets by considering the effect of orbital migration of giant planets due to their tidal interactions with the gas disks, after they have opened up gaps in the disks. The effect of migration is to sharpen the boundaries and to enhance the contrast of the planet desert. It also clarifies the separation between the three populations of rocky, gas-giant, and ice-giant planets."

- Towards a Deterministic Model of Planetary Formation I: a Desert in the Mass and Semi Major Axis Distributions of Extra Solar Planets - S. Ida and D. N. C. Lin

This suggests that "good Jupiters" might not be so rare after all.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 06:15 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.