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Author Topic:   How is Natural selection a mechanism?
JonF
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(2)
Message 120 of 191 (816065)
07-28-2017 3:13 PM
Reply to: Message 118 by AndrewPD
07-28-2017 2:09 PM


Science isn't settled by lists. But any "evolutionist" could sign that with a clear conscience.

https://en.m.wikipedia.org/...entific_Dissent_From_Darwinism

quote:
The listed affiliations and areas of expertise of the signatories have also been criticized,[1][12] with many signatories coming from wholly unrelated fields of academia, such as aviation and engineering, computer science and meteorology.[38]

In addition, the list was signed by only about 0.01% of scientists in the relevant fields. According to the National Science Foundation, there were approximately 955,300 biological scientists in the United States in 1999.[39] Only about 1/4 of the approximately 700 Darwin Dissenters in 2007 are biologists, according to Kenneth Chang of the New York Times.[12] Approximately 40% of the Darwin Dissenters are not identified as residing in the United States, so in 2007, there were about 105 US biologists among the Darwin Dissenters, representing about 0.01% of the total number of US biologists that existed in 1999. The theory of evolution is overwhelmingly accepted throughout the scientific community.[21] Professor Brian Alters of McGill University, an expert in the creation-evolution controversy, is quoted in an article published by the NIH as stating that "99.9 percent of scientists accept evolution".[40]

The list has been criticized by many organizations and publications for lacking any true experts in the relevant fields of research, primarily biology. Critics have noted that of the 105 "scientists" listed on the original 2001 petition, fewer than 20% were biologists, with few of the remainder having the necessary expertise to contribute meaningfully to a discussion of the role of natural selection in evolution.[11][12]

Critics have also noted that the wording and advertising of the original statement was, and remains, misleading,[11] and that a review of the signatories suggested many doubt evolution due to religious, rather than scientific beliefs.[12] Robert T. Pennock notes that rather than being a "broad dissent", the statement's wording is "very narrow, omitting any mention of the evolutionary thesis of common descent, human evolution or any of the elements of evolutionary theory except for the Darwinian mechanism, and even that was mentioned in a very limited and rather vague manner." He concludes that it is not in fact a "radical statement".[41]


Note especially the last paragraph.

Of course any discussion of that meaningless list would be incomplete without Project Steve. 1,417 scientists have signed:

quote:
Evolution is a vital, well-supported, unifying principle of the biological sciences, and the scientific evidence is overwhelmingly in favor of the idea that all living things share a common ancestry. Although there are legitimate debates about the patterns and processes of evolution, there is no serious scientific doubt that evolution occurred or that natural selection is a major mechanism in its occurrence. It is scientifically inappropriate and pedagogically irresponsible for creationist pseudoscience, including but not limited to "intelligent design," to be introduced into the science curricula of our nation's public schools.

And each and every one is named Steve or some variant, including the renowned Professor Steve S. Steve . Approximately 1% of scientists are named Steve, so the signatories represent only a tiny fraction of scientists who would sign that statement.

(In case you haven't figured it out, the list is a joke mocking the foolish DI list and others creationists have produced.)


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JonF
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Posts: 5717
Joined: 06-23-2003
Member Rating: 2.3


Message 121 of 191 (816066)
07-28-2017 3:18 PM
Reply to: Message 120 by JonF
07-28-2017 3:13 PM



Prof. Steve S. Steve.

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JonF
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Posts: 5717
Joined: 06-23-2003
Member Rating: 2.3


Message 160 of 191 (816427)
08-04-2017 9:56 AM
Reply to: Message 155 by AndrewPD
08-03-2017 9:27 PM


A Refrigerator is intelligently designed. I don't see how the sun reduces entropy simply by giving off energy.

It doesn't. The energy given off by the sun has a temperature, that of the Sun, , and the Earth absorbs it. Since the average temperature of the Earth is not increasing (significantly) all that energy must be radiated back into space, but at a much lower temperature. That reduces entropy. on the Earth.

Does Life On Earth Violate the Second Law of Thermodynamics? is a pretty good resource.

Does it reduce entropy on Mars?

Yes.

Also entropy under one description relates to degrees of freedom. This is the example given in a gas. So it is statistically unlikely that all the molecules in a gas will go into one corner of a jar because there are to many other possible arrangements. So entropy reflects the unlikelihood of certain formations or order when there is a huge range of other probabilistically available outcomes.

The earth is not a gas, nor do the ideal gas laws cover this situation. The statistical view of entropy does cover this situation, but the Earth-Sun-Space system is so complicated we can't even think about beginning to try to apply it.


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JonF
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Posts: 5717
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Message 161 of 191 (816428)
08-04-2017 10:04 AM


On the Earth's entropy
In the seventh message at Evidence, Gordon Davisson provides a good explanation:

quote:
Well, actually, don't do that math, because what I just said isn't entirely accurate. The "heat flows" involved aren't happening under sufficiently near-equilibrium conditions to have a well-defined temperature in the right sense for the equation I gave to apply. The radiation from the Sun is pretty close to a 6,000K blackbody spectrum, and blackbody radiation carries entropy S=4E/3T, so you can get a good idea of the entropy carried by sunlight from that. The entropy carried by radiation leaving Earth is much harder to analyse: there's some reflected sunlight (that no longer matches a blackbody spectrum), and a lot of thermal emission following a wide assortment of non-blackbody spectra. But I think I can get a pretty safe lower bound on it...

So, let's take a stab at doing the (right) math. The solar constant at Earth's orbit is 135.30 mW/cm^2 = 1353 W/m^2 (all data is from the _CRC Handbook of Chemistry and Physics_, 57th edition; this value is from page F-200). Earth's cross section is 1.27e14 m^2 (Pi*R^2, where R = 6371 km; page F-175). Earth's total insolation is then solar constant * cross seaction = 1.73e17 Watts. At 6000K, using S=4E/3T, that comes to 3.83e13 W/K (or if you prefer, 3.83e13 J/K per second) of entropy received by Earth from the Sun.

As for the outgoing entropy... since I'm going for a lower bound, I'll ignore the contribution from reflected sunlight, and just count the entropy of thermal radiation from Earth. Since Earth isn't a decent blackbody, I can't even calculate that properly, but I claim that the entropy must be at least E/300K (based on the idea that most of the radiation is produced spontaneously at temperatures below 300 Kelvin -- if that's not enough information for you to figure out my reasoning, I'll try to explain later). Earth's albedo is around .36, meaning around 36% of the sunlight reflects off and 64% (1.1e17 W) is absorbed; for present purposes I'll assume the same amount is emitted (although I understand it's actually a little higher). Divide that by 300K and we get at least 3.7e14 W/K (or 3.7e14 J/K per second) leaving Earth. That's almost 10 times the amount we receive from the Sun, and the actual figure is probably noticeably higher than what I calculated here.

If you want the net entropy flux for Earth, you should also count matter flows (meteorites and cosmic rays incoming, helium outgoing, neutrinos in then right back out, etc), but I suspect those are negligible compared to the flux due to light. If you'll go along with me on that, we can treat 3.7e14 W/K - 3.83e13 W/J = 3.3e14 W/K as a plausible lower bound on Earth's net entropy efflux.

Plugging that into the second law tells us that Earth's entropy could be decreasing by up to 3.3e14 J/K per second (or more! ). How fast (or even if) Earth's entropy is actually decreasing depends on how much entropy is produced by irreversible processes on (and in) Earth. If it's produced faster than it leaves, it'll build up and Earth's entropy will increase. If production lags behind exports, Earth's entropy will decrease. The second law won't tell you which if these is happening, all it'll tell you is that while entropy can be produced, it can never be destroyed.

I suspect that the Earth's total entropy is actually fairly constant, since the Earth (overall) maintains a fairly steady state. Its entropy may be increasing a little at present due to global warming, and it probably decreases a bit going into ice ages. The (direct) effect of evolution on Earth's entropy is negligible. Earth is mostly rock (in various phases) with a bit of water and a little air on top; living organisms make up only a tiny part of Earth, and their contribution to Earth's entropy will be similarly tiny.



  
JonF
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Posts: 5717
Joined: 06-23-2003
Member Rating: 2.3


(1)
Message 162 of 191 (816429)
08-04-2017 10:05 AM
Reply to: Message 157 by Riggamortis
08-03-2017 11:00 PM


Re: 2nd Law
The second law applies to all systems. The dS >= Q/T formulation applies only to closed systems.

This message is a reply to:
 Message 157 by Riggamortis, posted 08-03-2017 11:00 PM Riggamortis has responded

Replies to this message:
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JonF
Member
Posts: 5717
Joined: 06-23-2003
Member Rating: 2.3


(1)
Message 167 of 191 (816482)
08-05-2017 8:46 AM
Reply to: Message 165 by Riggamortis
08-04-2017 10:02 PM


Re: 2nd Law
The equation boils down to "entropy must incease or remain the same", and in reality it never stays the same.

Your reference goes on the say "Since entropy gives information about the evolution of an isolated system with time, it is said to give us the direction of "time's arrow". They do not address the information of an open system's evolution with time. IMHO they don't make this sufficiently clear.

How does a refrigerator relate to any of this?

See the second box in your reference. Refrigerators move heat from a colder reservoir to a hotter one, which is impossible if the system is isolated. They reduce the entropy inside them at the expense of increasing the entropy outside them by more, for a*net* increase in entropy. So entropy flows out of the system due to the work preformed and the system is not isolated.

In this case the entropy equation is:

dS = Q(within the system)/T(within the system) + Q(to the outside)/T(outside)

and as long as the appropriate work is performed by some engine the second term is negative and overrides the first for a net decrease of entropy in the refrigerator.

See Does Life On Earth Violate the Second Law of Thermodynamics? for a moderately technical discussion; you may not be able to follow it all the way through but the beginning is the key.


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JonF
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Posts: 5717
Joined: 06-23-2003
Member Rating: 2.3


Message 168 of 191 (816483)
08-05-2017 8:49 AM
Reply to: Message 166 by Riggamortis
08-04-2017 11:11 PM


Re: Entropy
Pretty much anything Man does doesn't affect the entropy of the Earth significantly, which is the entropy of the entire mass of the earth. Even the mass of the oceans is insignificant. What we do is just too small scale.

Heat flows and temperatures are another story.

{ABE} Oh, and, all the Sun's energy that isn't reflected or otherwise prevented from being absorbed by something on the Earth winds up as heat. The path it takes to get there (Solar cells, ..) doesn't matter.

Edited by JonF, : No reason given.


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