The Sun is only slightly older in astronomically speaking than is the Earth. The Sun, the Earth, and all the other planets in our solar system formed from the same common stuff: remnants of older stars. Our Sun is a third generation (or even more) star. The first generation of stars formed from the elements created during the big bang itself: hydrogen, helium, a tiny bit lithium, and nothing else. These stars were large (very large) and hence (very) short-lived. The deaths of these stars produced some metals (anything above helium is a metal to an astronomer), but not much beyond oxygen. Even a little metal changes how stars burn and evolve. The next generation of stars, which formed from the blown-up remnants of the first generation of stars, burned and evolved a bit differently than did that very first generation. When they died they produced elements even further up the periodic table. Our Earth (and everything in the solar system) is the product of at least two supernovae.
billvon The dust cloud that we (i.e. humans, earth, the sun) came from was created at least in part by a supernova; that's where all those heavy elements came from. ...................................................... I like the idea , but as an explosion supernova , before supernova , would not all hydrogen get consumed and form all other elements , so where did our star ( sun ) got its hydrogen to burn ? :shrug:
Well: 1) It's hard to imagine the violence of a supernova; even atomic structures are disrupted as the star collapses at one quarter the speed of light and reaches temperatures of 100 billion degrees K. Much of that matter is torn apart and ends up back at hydrogen (i.e. just one proton.) 2) Even stars that go supernova still have a lot of hydrogen in their outer shell, and this is ejected either before the star goes nova or as it's happening. 3) Interstellar space is full of free hydrogen just wandering around. It's not very dense, but give a dust cloud a billion years to attract it all and you can build up quite a lot of hydrogen.
Ooh, those impudent bastards! May God sting their toes. Actually, what I meant was: so there was a universe before the universe? I thought it was just a collection of unknown and unknowable matter that blew the hell up one day.
The part about the sun being a third-generation star? Yes. Here is a short description of the process. This is also covered in a previous post on this thread. No, it's the same universe. The stars are not all going nova and giving birth to the next generation at the same time. You need to take a stroll over to the Cosmology board to catch up on that subject. At this point the cosmologists seem to be saying (I have great difficulty understanding them) that there was nothing before the Big Bang--literally "nothing" in every scientific and philosophical sense, not even a space-time continuum. The way I put this is that time has an Absolute Zero, just like temperature. To ask "what was the universe like before the Big Bang" is as meaningless as asking "how does matter behave when its temperature drops below absolute zero?" Of course I graph time on a logarithmic scale, so the moment of the Big Bang is at minus infinity. This should make it easier to study, since everything happened so fast in those days. I still hold out hope for my hypothesis based on the Second Law of Thermodynamics. It says that entropy increases with time, but not monotonically at the local level. Local reversals of entropy are possible and no one has said that there is a limit on their size. So there may have been nothing for googolplexes of years, yet suddenly one day there was a local reversal of entropy and the universe that we know and love popped into existence. Yes, a rather large local reversal of entropy, but there's no law against it.
Yes and no. Some cosmologists do talk about a "before the big bang". E.g., is our universe a zero-energy quantum fluctuation of some other universe? Definitely not standard ΛCDM big bang cosmology, but not crackpot either. A bit too conjectural and not near enough evidence from my perspective, but definitely not ruled out. Not necessarily the best comparison. There are quantum mechanical systems, real ones at that, that can only be interpreted as having negative temperature. Systems with negative temperature are not colder than absolute zero. They are in fact hotter than any system with a positive temperature. That said, what you said about generations of stars is correct. We are talking generations of stars here, not generations of universes. The universe doesn't end just because some star goes supernova.
So what are we going to have next, imaginary numbers for temperatures? Please Register or Log in to view the hidden image! Even if the Big Bang is Absolute Zero, perhaps we'll discover that time, too, can be negative.
I don't think such system need to be "quantum mechanical" because they can have huge numbers of particles and large masses, but will not argue this point. I just want to mention that ALL lasers have "super thermal" upper state populations. Depending on how you want to define their temperatures this is either negative or greater than plus infinity temperature, but of course it is wrong to assign any temperature to these non-equilibrium systems. PS in post 21, DH is speaking of "generations" as any reasonable, non-astronomer would. I.e. generation 1 comes before generation 3 etc. But for astronomers Generation 3 comes before generation 1. This is because before telescopes stars visible to the human eye were all that was known -Then more distant stars were discovered and they were the 2nd generation, etc. When telescopes were able to look back in time to the original stars, they were called "generation 3" Thus for astronomers the sun is a Gen 1 star. They also call elements like carbon, oxygen, etc. "metals" -seriously they do. This is because they consider "Metals" to be made by the original "third generation" stars that only had hydrogen or helium, but near end of their life may have "cooked" some iron or lighter elements in terminal fusion cycles. The biggest and hottest original 3d generation stars can also make small amounts of post iron elements by "endothermic cooking" but most post iron elements are made during supernova explosions. The lighter elements (but heavier than He) are mainly made by fusion cycles in big stars not supernovas
I used generation the way I did because I thought it would have just been confusing to use the correct terminology, which does not involve the word "generation" at all. Instead, astronomers call stars such as ours with significant metalicity (anything above helium) in their outer atmospheres as Population I, stars with low metalicity as Population II, and the hypothetical first stars as Population III.
Our planet Earth is a third planet in the solar system. It has undergone several geological changes before it evolved to its present form. To know more about how the Earth was formed. The Earth, at the beginning, was very different from what it is now. It did not have any atmosphere or water bodies. The common belief of scientists is that our planet earth was formed some 6 million years ago. The sun, the planets and their satellites in our solar system were all formed due to the contraction of solar nebula. Solar nebula, from which our solar system is said to have formed, was a huge mass of spiral cloud made up of dust particles and various types of hot gases. The constituent elements of the solar nebula were mainly hydrogen and helium and some other heavier elements. Solar nebula began its contraction about 6 million years ago. During the contraction process, its temperature came down and it began to rotate very fast. As a result of cooling, shrinking and rapid rotation, the outer part of the cloud got detached from the main body in the form of rings.
Please do not use language like that. This is how journalists confuse people. While it is correct that scientists believe this, the reason is that it has been proven true beyond a reasonable doubt. It should be presented to laymen as a fact, not a belief. This is why laymen think there is room for doubt in everything from relativity to global warming.
The Earth was formed 4.5 BILLION years ago. 6 million years proved beyond doubt? But the dinosours died out 60 million years ago......
Here are some links to back that up: http://en.wikipedia.org/wiki/History_of_the_Earth http://en.wikipedia.org/wiki/Dinosaur
6 million years ago? Pfff! I have shirts older than that! Please Register or Log in to view the hidden image!
Gee. Guys, actually before Charles Darwin die, he said that he didn't really believe in evolution even though he have invented the evolution. Believe it or not, the earth is only 6 million years old, not 4.5 billion.
The normal practice on this science forum is to cite a source when you make a claim especially one as idiotic as that.
