U.S. CitiesCity-Data Forum Index
Go Back   City-Data Forum > General Forums > Science and Technology
 [Register]
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
View detailed profile (Advanced) or search
site with Google Custom Search

Search Forums  (Advanced)
 
Old 12-18-2012, 10:01 AM
 
Location: Victoria TX
42,668 posts, read 71,653,762 times
Reputation: 35881

Advertisements

Is there any scientific reason why some similar elements are more abundant than others? Why is Iron more abundant than Cobalt, or Aluminum more abundant than Gallium, or Chlorine more abundant than Fluorine? One would assume that in a Big Bang, that elements would sort themselves out in somewhat equal abundances, so what is the reason that an element with an atomic number of X would be so much more abundant than one with an atomic number of Y?

Was it just the laws of chance that they fell that way, or if there were to be another big bang in another universe, would there be a similar distribution of elements, with the same ones rare and the same ones abundant? Could there be, somewhere in this universe (or another one), stars or planets that are made mostly of Gold or Platinum, with very little Iron or Aluminum? Or is there some characteristic of their atomic structure that militates against their widespread random formation?
Reply With Quote Quick reply to this message

 
Old 12-18-2012, 12:10 PM
 
Location: Somewhere in northern Alabama
16,874 posts, read 51,413,686 times
Reputation: 27775
There is no randomness. It has to do with star formation and type. (The following is a very crude approximation, but helps in visualizing the process.) Hydrogen was first after the big poop, (everything was electrons and basic particles, which became hydrogen) and with each generation of stars more of that hydrogen was converted to something else (helium?) and then when that star went nova, the next star formed out of the rubble and converted that into even heavier elements, etc.
Reply With Quote Quick reply to this message
 
Old 12-18-2012, 12:57 PM
 
Location: Cleveland, Ohio
10,836 posts, read 12,886,501 times
Reputation: 7078
I don't get the reasoning for thinking everything would be equal? I would expect the exact opposite, as it is.
Reply With Quote Quick reply to this message
 
Old 12-18-2012, 03:34 PM
 
Location: Victoria TX
42,668 posts, read 71,653,762 times
Reputation: 35881
Quote:
Originally Posted by harry chickpea View Post
There is no randomness. It has to do with star formation and type. (The following is a very crude approximation, but helps in visualizing the process.) Hydrogen was first after the big poop, (everything was electrons and basic particles, which became hydrogen) and with each generation of stars more of that hydrogen was converted to something else (helium?) and then when that star went nova, the next star formed out of the rubble and converted that into even heavier elements, etc.
That doesn't explain any mechanism that would result in a lot of hydrogen skipping Fluorine, and going on to form lots of Cholrine. Once a process was taking place that enabled or caused hydrogen to convert in great quantities into some heavy elements, why did it mostly skip some light elements. Could the hydrogen regeneration process have converted to more Fluorine than Chlorine, or is there some aspect of their atomic structure that favoted some configurations more than others? Lots and lots of Iron, but much less of elements that would have been formed earlier than Iron with smaller atomic numbers.

You are obviously not understanding my question, but I don't know any other way to express it.
Reply With Quote Quick reply to this message
 
Old 12-18-2012, 08:50 PM
 
Location: Somewhere in northern Alabama
16,874 posts, read 51,413,686 times
Reputation: 27775
Since I am obviously not understanding your question, all I can do is point you to a couple of websites that explain element formation.

FORMATION OF THE HIGHER MASS ELEMENTS

Nucleosynthesis - Wikipedia, the free encyclopedia

Note the caption in the second cite:
"The next three elements (Li, Be, B) are rare because they are poorly synthesized in the Big Bang and also in stars. The two general trends in the remaining stellar-produced elements are: (1) an alternation of abundance of elements according to whether they have even or odd atomic numbers, and (2) a general decrease in abundance, as elements become heavier. "
Reply With Quote Quick reply to this message
 
Old 12-18-2012, 09:21 PM
 
Location: Westwood, MA
3,480 posts, read 4,366,329 times
Reputation: 4482
There are two reasons for the observed elemental abundances, how likely they are to be formed and how likely they are to accumulate on solid rocky planets. Understanding the first question explains the observed total abundances (averaged over stars and planets and interstellar and intergalactic gas and dust); understanding the second helps explain how we get from those abundances to what we actually have on Earth.

I'll focus on the total abundance, which is determined by physics. The terrestrial abundance is determined by geology and chemistry.

Almost all the baryons (i.e. nuclear matter) formed after the big bang were in the form of proton, or simple hydrogen. There was a small amount of deuterium, helium, beryllium, and maybe boron formed, as well, but most everything was hydrogen. Star formation and burning converted a lot of that hydrogen into helium. For big enough stars, the helium could be converted into other nuclei, typically near the end of stellar lifetime as hydrogen burning slows and the star contracts. The exact reactions that allow this to happen depend a lot on the particulars of the neutron and proton configuration, so certain states are much more likely (i.e. much easier and more stable) to form. This process of stellar nucleosynthesis explains much of the observed natural abundances, at least up to iron, which is the most stable nucleus.

Almost all elements heavier than iron are formed from supernova synthesis, where the energy in an exploding star is converted into heavy nuclei that is energetically unfavorable for fusion. Again, certain reactions are more favorable than others, which largely explains the abundances we see.

To answer your original question, if there were a universe with the exact same physical constants then the stellar abundances would likely be very similar. It's the reactions that determine these abundances and those would be the same. If the physical constants (G, e, h, etc.) were different, you could expect a change in the abundances but you would still see a dramatic decrease in abundance with increasing mass. It would be interesting to see how much one would have to change the coupling constants to make something like Be more plentiful, but that's something beyond my ability to calculate. I don't see anything that would make Pt more abundant than H, though. (Also, in that universe, the properties of Be and Pt would likely be much different, as well)
Reply With Quote Quick reply to this message
 
Old 12-18-2012, 09:59 PM
 
Location: Victoria TX
42,668 posts, read 71,653,762 times
Reputation: 35881
Quote:
Originally Posted by jayrandom View Post
The exact reactions that allow this to happen depend a lot on the particulars of the neutron and proton configuration, so certain states are much more likely (i.e. much easier and more stable) to form. )
There is the answer I was looking for. There are certain atomic configuration states that are more likely to fall into place and/or remain stable. Did I get that right?

In other words, I gather, if our present universe collapsed back into its singularity and Big-banged again, the next version would probably have an approximately similar pattern of relative abundance of elements (at comparable age), since all the physical laws of that Universe would be the same ones that govern this one. Because some atomic configurations are more likely to prevail than others.

Leading to this question: How well do we know those atomic configuration limitations, and does that "law" as we understand it leave us with any elements whose abundances are inexplicable outliers to that theory. Is anybody scratching their head saying they can't understand why there is so much or so little Xy in the universe in violation of this apparent principle?
Reply With Quote Quick reply to this message
 
Old 12-19-2012, 05:34 AM
 
Location: Westwood, MA
3,480 posts, read 4,366,329 times
Reputation: 4482
Quote:
Originally Posted by jtur88 View Post
There is the answer I was looking for. There are certain atomic configuration states that are more likely to fall into place and/or remain stable. Did I get that right?

In other words, I gather, if our present universe collapsed back into its singularity and Big-banged again, the next version would probably have an approximately similar pattern of relative abundance of elements (at comparable age), since all the physical laws of that Universe would be the same ones that govern this one. Because some atomic configurations are more likely to prevail than others.

Leading to this question: How well do we know those atomic configuration limitations, and does that "law" as we understand it leave us with any elements whose abundances are inexplicable outliers to that theory. Is anybody scratching their head saying they can't understand why there is so much or so little Xy in the universe in violation of this apparent principle?
First, to be clear, this has to do with nuclear configurations (meaning protons + neutrons) not atomic ones (meaning nuclei + electrons). You're essentially asking how well nucleosynthesis theory describes observed elemental abundances. It's not my field so I don't know for sure, but I think there is pretty agreement between theory and observation and I'm not aware of any gaping holes in the current understanding.

As to your second question, which is whether a different universe would have similar abundances, that involves both nuclear theory, which is pretty well worked out, and high energy cosmology which is not. If the new universe had the same fundamental constants (for the four forces and the masses of the fundamental particles) then nuclear theory predicts similar abundances. The trans-iron elements are formed in very abrupt and rare events, so the exact abundances may differ slightly, but that is a minor detail.

High energy theory, however, isn't sure that the fundamental constants in our universe are the only possible fundamental constants. Essentially they're isn't a good explanation for why they are what they are and there's no reason to think that they are the only ones a universe could have. With different constants the nuclear theory could change significantly and effect both the nuclear and gravitational processes that
govern nucleosynthesis. It's possible a universe like that would have only hydrogen, or it's possible a universe could have lots of Be (there isn't much in the current universe) or that Fe wouldn't be the most stable nuclear configuration.
Reply With Quote Quick reply to this message
 
Old 12-19-2012, 09:48 PM
 
Location: Victoria TX
42,668 posts, read 71,653,762 times
Reputation: 35881
Thanks, good answer. Just for clarity, I was not asking about a different universe, but about this same universe, after a hypothetical withdrawal to a singularity, and then another big bang of the same universe, starting a new cycle, which would presumably be governed by the same natural laws.
Reply With Quote Quick reply to this message
 
Old 12-19-2012, 11:14 PM
 
Location: Westwood, MA
3,480 posts, read 4,366,329 times
Reputation: 4482
Quote:
Originally Posted by jtur88 View Post
Thanks, good answer. Just for clarity, I was not asking about a different universe, but about this same universe, after a hypothetical withdrawal to a singularity, and then another big bang of the same universe, starting a new cycle, which would presumably be governed by the same natural laws.
It's not clear if our current constants would carry through a singularity, which is why I hedged my earlier statement. Assuming they do you should get the answer you're looking for.
Reply With Quote Quick reply to this message
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.

Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.


Reply
Please update this thread with any new information or opinions. This open thread is still read by thousands of people, so we encourage all additional points of view.

Quick Reply
Message:

Over $104,000 in prizes was already given out to active posters on our forum and additional giveaways are planned!

Go Back   City-Data Forum > General Forums > Science and Technology
Follow City-Data.com founder on our Forum or

All times are GMT -6.

2005-2018, Advameg, Inc.

City-Data.com - Archive 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 - Top