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Author Topic:   Atheistic, Theistic, YEC or OEC -- That is the Question?
Dr Cresswell
Inactive Member


Message 11 of 18 (33630)
03-04-2003 1:01 PM
Reply to: Message 9 by Philip
03-03-2003 11:13 PM


Philip, there are some very obvious problems with some points on that site you linked to.
Take this point (which you implied refered to caesium clocks and E=mc2, though I don't see the connection) for example
quote:
11 . Some who believe in an old universe have a different explanation. Those isotopes are extinct because so much time has passed. However, this explanation raises a counterbalancing question: How did those isotopes, and 97% of all elements, form? The standard answer is that these elements appeared during supernova explosions. This is actually speculation, because essentially no supporting evidence has been found. Besides, all supernova remnants we see in our galaxy appear to be less than 10,000 years old. This is based on the well-established decay pattern of a supernova’s light intensity in the radio-wave frequency range.
The problem here is two fold;
1) that the overwhelming majority of supernovae occured early in the life of the galaxy when it was dominated by massive stars (we know that from studies of very distant galaxies), and so the contribution of modern supernovae to the abundances of heavy elements is minor.
2) by their very nature supernovae remnants disperse with time, and so the absence of really old remnants is hardly surprising. And the 10000 year age is wrong too - "Tycho's Star" in Cassiopeia exploded at least 20000 years ago, and SN1987A in the LMC about 169000 years ago.
Alan

This message is a reply to:
 Message 9 by Philip, posted 03-03-2003 11:13 PM Philip has replied

Replies to this message:
 Message 14 by Philip, posted 03-14-2003 7:02 PM Dr Cresswell has replied

  
Dr Cresswell
Inactive Member


Message 17 of 18 (34444)
03-15-2003 3:48 AM
Reply to: Message 14 by Philip
03-14-2003 7:02 PM


Re: Higher elements
The only production mechanism for significant quantities of heavy elements (basically anything above He) is fusion within stars - though there are some isotopes that can be formed by other processes, 14C and 36Cl through the action of cosmic rays for example or various anthropogenic sources. Stellar fusion can generate elements upto iron, but beyond that the reaction is no longer energetically favourable. Within the core of a massive star, however, with the loss of suitable fuel for fusion the collapse will be so rapid and generate such heat that energetically unfavourable fusion will occur and produce considerable quantities of heavier elements. The final stage of the collapse will be the point where the core density gets so high that protons transmute into neutrons producing a blast of neutrinos and a shockwave that ejects most of the core and outer layers of the star. This is what is called a supernova.
Clearly the rate of supernovae in the galaxy is currently far too low to account for the amount of heavy elements we observe here. However, observations of galaxies much younger than our own shows conclusively that they're dominated by super-massive stars that will very quickly collapse and go supernova. There is no reason to believe that this galaxy was any different when formed than other galaxies. This gives a consistant picture of the evolution of the galaxy - supermassive stars which rapidly go supernova seeding the galaxy with heavy elements, which in turn get incorporated into later stars (note: the presence of trace amounts of heavy elements affects the fusion inside stars, and as such would encourage the formation of smaller stars rather than the early generations of supermassives).
So to address your points 1 to 4 - heavy elements were formed in the nuclear furnaces of supermassive stars in the early stages of the galaxy and dispersed by supernova explosions (with small quantities from more recent supernovae). They weren't captured by our solar system - they were part of the cloud of hydrogen and dust from which our solar system formed.
Alan

This message is a reply to:
 Message 14 by Philip, posted 03-14-2003 7:02 PM Philip has not replied

  
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