If the big bang theory was the beginning of all, why scientists claim that the only producers of heavy metals are super massive stars?
I’m no physicist; however, I do have an interest in physics. I’ve learned recently that science shows that through supernovae from super massive stars, we get heavy metals (iron, lead, etc.). This is due to the extreme mass which creates enough gravitational force to continue fusion after the “fuel” (hydrogen and helium) is burned and contain the stars intact during the process since fusing heavier elements creates more energy therefore more outward force. Since scientists claim that the big bang created all, why is there no evidence, or debate for that matter as to why heavy metals didn’t exist before super massive stars could form and create those metals. Or even more so, why aren’t all the elements out there heavy metals? My question, though possibly flawed, is spawned from my recent knowledge and also from when I was in Junior High. At that time, I “learned” that the combined mass of the universe before the big bang was so compressed that it was as small as the period at the end of this sentence. If that’s the case why do they say that when this incredible “explosion” occurred that the only elements in existence after the big bang were “light” elements like helium and hydrogen? Am I crazy for asking that kind of question, or are they all wrong?
7 comments:
Is there another physicist that reads this blog?
I'm trying to figure out how to answer your questions without turning this into the longest comment ever posted.
Answer Part 1: The Big Bangy Beginning.
Temperature is a measure of the average kinetic energy of a material. The hotter something is, the faster its little atoms move. In the time immediately after the big bang everything was so hot nothing could stick together. Electrons and protons were flying around so fast they did not form atoms, and if they did, ever so briefly, another particle would soon crash into it and knock everything apart.
As things expand, they cool (provided no outside energy is added). At a certain point, things cooled enough that simple atoms started forming, mostly H and He.
So we are left at the end of the big bang with a whole universe full of H and He. Pretty boring.
Answer Part 2: Fusion
"The sun is a mass of incandescent gas, a gigantic nuclear furnace where hydrogen is built into helium at temperatures of millions of degrees." -- They Might Be Giants
The basic idea of fusion is that in combining the nuclei of two atoms, one new different atom is formed. But nuclei are surrounded by electrons. These electrons repel each other and produce a pretty effective barrier preventing fusion, which is what keeps everything from fusing around us. Stars are hot. (Remember, hot = moving fast on an atomic level.) So inside stars, atoms are constantly fusing. Fusion, like chemical reactions either requires or produces energy. If the fusion inside a star required energy, with each fusion event the star would cool until it quickly got cold enough that the atoms slowed down until they didn't fuse anymore. Lucky for those of us that depend on the sun for survival, fusion usually released energy. Nuclei keep releasing energy as they grow bigger . . up to a point. And that point is iron. Stars can survive and produce light and heat until they convert everything to iron, and then they're done. Of course this is the simplified version.) In reality, stars start to flame out before everything is converted to iron as it just runs out of fuel to keep itself going.
Answer Part 3: Supernova
"Champagne supernova in the sky" -- Oasis
The heat from a star makes it want to expand. It's own gravity makes it want to collapse. As long as the star is burning brightly, shining for the whole world to see it strikes a balance between the expansion and contraction. Once the fusion process dies down, gravity starts to take over. Provided the conditions are right (code for: I'm refusing to provide more detail) the star will collapse and go supernova. Basically, the mass of the star all starts falling in to the center. The star has a massive amount of gravitational potential energy. It collapses in on itself and suddenly exerts huge pressures and temperatures on the core. There is so much energy available that two things happen. First, fusion can occur that normally isn't energetically favorable. Iron and carbon and sodium atoms can start combining to form gold and tin and xenon. Then those can combine to form cesium or uranium or even more exotic elements. The other thing that happens is all the remaining light elements (hydrogen and helium) fuse in one big last gasp reaction. It's like your car as it's about to run out of gas decided to toss the last half gallon in your engine all at once and make your whole car explode. It's quite a way to go. All this fusion unleashes an enormous amount of energy (as much as our sun might produce in 10 billion years) and the star explodes. The explosion spews the guts of the star across the universe. So, dying stars (well, some dying stars) make heavy metals. So why isn't everything a heavy metal?
Answer Part 4: Fission
Fission is where the nucleus of an atom splits apart into two (or more) new atoms. I suppose any atom could split, but it only releases energy for atoms larger than iron. This is why you only hear about Uranium and Radon and such elements undergoing fission and breaking down into more "normal" elements. The break even point is iron. I'm not sure why, but the iron-56 nucleus is the most energetically stable. Atoms bigger than Fe-56 tend to undergo fission, atoms smaller than Fe-56 undergo fusion.
So the follow up question is naturally, "So why isn't the whole universe made of iron?"
My answer: give it time. As far as I understand it, provided the universe continues to expand, everything has got to end up as iron. Of course, it would take an infinite amount of time to get there, and were only a few billion years towards infinity, so we've still got a long ways to go.
There. I don't really remember what the questions were that I started out trying to answer, but I think I might have answered them. Feel free to ask more questions.
So, are you saying that matter was in a state beyond plasma in the big bangy theory? I suppose that's possible since we have no way to know or see what the state of matter was at the time. It seems that it takes a bit of guesswork.
From wikipedia article on the big bang: "Extrapolation of the expansion of the universe backwards in time using general relativity yields an infinite density and temperature at a finite time in the past." The idea that the early universe was extremely hot is central to the idea of the big bang theory.
It takes energy to compress something. That energy has to go somewhere. Usually when you compress something, like air, to put it in your tires, the temperature of the air in the tire goes up, but only slightly. This is because the air is able to give the heat away to the tire and it seeps out into the rest of the world. But we have no way of conceiving of energy leaving the universe. A compressed universe simply had to be hot, and it's been cooling ever since it started expanding.
And we do have evidence. The universe is filled with what is know as the Cosmic Microwave Background Radiation (CMB or CMBR). No matter where you look in space, there is a permeating background radiation to the tun of 2.725 kelvin. No matter where you look this value does not change by more than about 0.000018 K. It is extremely isotropic and an evidence of the temperature of the universe when it was about 380,000 years old. At that time the temperature was about 3,000 K, when the plasma of the early universe cooled until it became favorable for electrons to combine with protons and form hydrogen atoms. "Most cosmologists consider this radiation to be the best evidence for the Big Bang model of the universe." (wikipedia)
I would suggest the wikipedia articles on the "Cosmic Microwave background Radiation" as well as the "Big Bang" article and the "Graphical timeline of the Big Bang". I suppose I could provide links, but you should be able to find them readily.
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