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The Science of Evolution (no politics or religion)

  • #1

    This topic has been created in response to the closure of the previous one on this topic caused by people who ignored the ban on religion and politics in the Off Topic forum.

    To avoid this happening again, I regret to have to point out that anyone who does similarly in this thread will be permanently blocked so the discussion can continue.

    Have fun discussing the science of evolution!

  • #2

       Great, Elroch! I have no doubt that this will be the ultimate scientific thread on the subject.

       May you have 10,000 posts of intellectual discourse, all the while lacking the loutish behavior of the very small minority of malcontents and mayhem causing trolls. Smile

  • #3

       Well, it appears to me that everyone can agree that the Earth is about 4.5 billion years old and that life started around 3.5 billion years ago. Agreed? Points of contention?

       Also, there are three aspects regarding evolution: geophysical, chemical and biological. Where do we start on this thread?

  • #4

    Geophysical...

  • #5

       Jolly good! Are you familiar with Harold Urey and the Urey ratio concerning the structure and evolution of Earth's mantle? If so, explain please.

  • #6

    No matter how hard I try I just can't read the words in that image. But don't worry its on Urey's wikipedia page. I don't know about that, sorry!

  • #7

    I can give you a research papers which may help though...

    http://onlinelibrary.wiley.com/doi/10.1029/2007RG000241/abstract

  • #8

       Perhaps this will be "more better":

  • #9

       Then we also have this:

    Cosmochemistry and the Miller–Urey experiment

    In later life, Urey helped develop the field of cosmochemistry and is credited with coining the term. His work on oxygen-18 led him to develop theories about theabundance of the chemical elements on earth, and of their abundance and evolution in the stars. Urey summarized his work in The Planets: Their Origin and Development (1952). Urey speculated that the early terrestrial atmosphere was probably composed of ammoniamethane, and hydrogen. One of his Chicago graduate students, Stanley L. Miller, showed in the Miller–Urey experiment that, if such a mixture be exposed to electric sparks and to water, it can interact to produce amino acids, commonly considered the building blocks of life.[46]

    Urey spent a year as a visiting professor at Oxford University in England in 1956 and 1957.[47] In 1958, he reached the University of Chicago's retirement age of 65, but he accepted a post as a professor at large at the new University of California, San Diego (UCSD), and moved to La Jolla, California. He was subsequently made a professor emeritus there from 1970 to 1981.[48][49][6] Urey helped build up the science faculty there. He was one of the founding members of UCSD's school of chemistry, which was created in 1960, along with Stanley Miller, Hans Suess, and Jim Arnold.[48][50]

    In the late 1950s and early 1960s, space science became a topical field of research in the wake of the launch of Sputnik I. Urey helped persuade NASA to make unmanned probes to a moon a priority. When Apollo 11 returned moon rock samples from the moon, Urey examined them at the Lunar Receiving Laboratory. The samples supported Urey's contention that the moon and the Earth shared a common origin.[48][50]While at UCSD, Urey published 105 scientific papers, 47 of them about lunar topics. When asked why he continued to work so hard, he joked, "Well, you know I’m not on tenure anymore."[51]

     

    re: http://www.ask.com/wiki/Harold_Urey?o=2801&qsrc=999&ad=doubleDown&an=apn&ap=ask.com

  • #10

    From another discussion, the topic of changes in gene expression in domesticated dogs came up. The point is that although the coding DNA of a dog and a wolf are almost identical, they can be very different both physically and behaviourally. These differences must be largely due to gene expression, which is caused by a combination of the different environment and differences in the non-coding DNA (which we now know has a role in gene expression, affecting the way organisms develop, behave in different environments and adapt to changes during their lifetimes (eg the effects of exercise).

    Here's some research on gene expression relating to the brains of dogs.

    http://www.sciencedirect.com/science/article/pii/S0169328X04001986

  • #11

    so- you know who- sent a bolt of lightning - from who knows where-

    and united various chemical that came from what- to produce a self-replicating carbon molecule that did it all.

  • #12

    In an infinite universe, even the most unlikely molecule will occur somewhere. There is literally nothing too unlikely to happen somewhere: it's just that very unlikely things happen a LOT less (eg they could be way too unlikely to have a reasonable chance of happening in the observable Universe.

    I feel some scientists have been a bit glib to claim that life arises as long as the basic pretexts of it are available (the right mix of elements, general conditions like temperature and pressure). It is entirely plausible that it is very unlikely (but not impossible) to arise even then, and that Earth was a lucky planet in a very big Universe.

    Analogies of this can be found even in deterministic systems like cellular automata such as Conway's Game of Life. These can produce very sophisticated phenomena, including a completely general computer (i.e. the equivalent of a Turing machine). If you produce a large enough version of this automaton with entirely random initial conditions (think "distribution of matter"), somewhere in it such a machine will appear. The same applies to EVERY possible phenomenon that can occur in such a system, of course.

  • #13

       Elroch, congratulations in that this thread was locked and is now unlocked! So, let's get back in and show that you can conduct a science thread without religion and politics, as you've stated.

  • #14

       I just discovered this interesting data in regard to the content of the universe 13.7B years ago vs. today:

    re: http://en.wikipedia.org/wiki/File:080998_Universe_Content_240.jpg

  • #15

       I thought that it was interesting that the universe today consists of only 4.6% atoms!

       Here is something also interesting:

    re: http://commons.wikimedia.org/wiki/WMAP#mediaviewer/File:CMB_Timeline75.jpg

  • #16
  • #17
    pawnwhacker wrote:

       I just discovered this interesting data in regard to the content of the universe 13.5B years ago vs. today:

     

    re: http://en.wikipedia.org/wiki/File:080998_Universe_Content_240.jpg

    Interesting. The ratio of dark matter to "atoms" (i.e. ordinary matter, excluding neutrinos) has stayed almost constant.

    I think the change in photons is because these charts are in units of energy, and the CMB has been redshifted a lot. For neutrinos it may be the same, because almost all of the energy of neutrinos at that very early time was kinetic.

    Not sure exactly when the time pinpointed is, but I suspect it is just after the "time of last scattering".

  • #18

       I still find it incredible that the universe consists of around 5% atoms and 75% dark energy and dark matter. There is still almost nothing known about both dark energy and matter. In fact, "hypothetical" is used freely when this subject is mentioned:

    In physical cosmology and astronomydark energy is a hypothetical form of energy which permeates all of space and tends to accelerate the expansion of the universe.[1] Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate. According to the Planck mission team, and based on the standard model of cosmology, on a mass–energy equivalence basis, the observable universe contains 26.8% dark matter, 68.3% dark energy (for a total of 95.1%) and 4.9%ordinary matter.[2][3][4][5] Again on a mass–energy equivalence basis, the density of dark energy (1.67 × 10−27 kg/m3) is very low: in the solar system, it is estimated only 6 tons of dark energy would be found within the radius of Pluto's orbit. However, it comes to dominate the mass–energy of the universe because it is uniform across space.[6]

    re: http://www.ask.com/wiki/Dark_energy?o=2801&qsrc=999&ad=doubleDown&an=apn&ap=ask.com

  • #19

       I must add...

       This, which I posted directly above, is also astounding to me. It says that there is only an extremely small amount (about 6 tons) of dark energy nearby...yet it permeates the rest of the universe.

       Wow! What does this mean for us in our solar system? What would it mean if we were to encounter massive amounts of it if we were to travel in a spacecraft and be in the midst of it? How can energy be weighed (the 6 tons mentioned above)?

  • #20

    First, it's worth noting that the average energy density of every single type of energy is very, very low. And the Universe is very, very big. So our distorted view of a region of very high matter density is misleading.

    Cool question about energy being weighed. I think the proper way to work it out is using general relativity: dark energy is a term in the Einstein field equations.

    But it's basically a pressure of the vacuum, a scalar quantity which corresponds to an energy density in the same way as the pressure of a gas is associated with a potential energy density. Such a pressure can be used to do work by expansion. [A weird thing about dark energy is that it keeps appearing, like a well that never runs dry,which is why that component of energy keeps going up]. If I understand correctly, all the types of energy are balanced by a gravitational energy which can be thought of as negative with respect to its value if nothing was near anything, which makes the Universe flat. Heck, the Universe is weird.

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