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Thread: How do we know?: A conversation about the periodic table

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    How do we know?: A conversation about the periodic table

    So the conversation I had with a couple of people I know on an MMORPG basically centered around fiction and stars.

    The discussion centered around a fictional universe in which there are a ton of "new elements" not exactly found on the current periodic table. In my argument, I pointed out that the elements that we do know about are actually pretty clear; we also understand the process that went into creating these elements, more or less.

    The point was brought up that we simply aren't sure; I brought up spectroscopy and how it can tell the chemical (and thus elemental) make-up of a star, but this was generally seen as irrelevant. The point was, that we simply don't know what's out there in the universe. In the case of Dark Matter, I would definitely agree!

    However, how do we know that the periodic table is sound? How do we know that we will not run into other strange elements out there in the universe? Or are we, and should be, truly uncertain?

    Note that I'm not talking about new ways of combining elements, but new elements altogether.

    Also, I'm aware that all scientific statements are inductive rather than deductive, but I'm simplifying a bit by saying "how are we sure".

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    Well, considering that elements are made up of integer multiples of protons, there's going to be a considerable difficulty slipping any extra ones in except at the very top end. Whenever we try to create elements at the top end, they pretty rapidly decay.

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    Any exceptions on the elements on the top end decaying rapidly?

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    There is an exception, called the 'island of stability'. We are still off the shore of this island in terms of creating its atoms, but the atoms themselves already have expected properties.

    I do want to point out that you're talking about two different things. The periodic table of the elements represents atoms, whereas dark matter does not need to be found on the periodic table. Elementary particles have their own balance sheet.

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    Maybe you're talking about the island of stability? How is spectroscopy irrelevant?

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    The core argument on the other side was that there might be elements floating out there that we don't know about and can have no clue about until we "go out and see them".

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    not really. There should be some elements around element 116 (IIRC) that should be more stable than the elements around them, but that means half-lifes in minutes instead of milli-seconds.

    The structure of atoms is quite well known. Protons and Neutrons inthe nucleus with electrons around. With this structure there isnt any way there could be a new element except ones larger than currently known. When that is considered, for there to be a stable element that we dont know about, there would need to be some rather large fundamental changes in our understanding of physics.

    As for the 'we dont know what is out there!' arguement, that isnt really true. We see alot of the universe, and what we can see is always the same stuff. Stars a billion light years away are the same stuff as the stars around here.

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    Ok, taking a quick look at the Periodic Table I find that some transuranic elements do have long lifetimes, but I'm pretty sure that they don't tend to be created naturally. For example, Curium (247Cm) has a half life of 16 million years, but was first created by bombarding plutonium with alphas.

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    Quote Originally Posted by Lonewulf View Post
    Any exceptions on the elements on the top end decaying rapidly?
    By the "top end" I assume you mean at the high atomic weights, the trans-uranic elements.

    And the answer is yes. There is the so called Island of Stability and there are some indications we are getting close to it. But, one of the things that is not know is, even if exists, how stable these "relatively stable" superheavy elements will be. If their half-lives are measured in seconds or even minutes, they are much more stable than the currently know elements in the 100+ atomic number range. But they still would be too unstable to do much with, or to be expected to be found in nature.

    The science fiction writer Poul Anderson wrote some stories with these concepts in them.
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    Now that we have studied atoms of all the elements that exist naturally
    on Earth, plus many that have been artificially constructed, and know
    what they are made of and how they are put together, we are able to
    define what an element is. An element is a configuration of protons,
    neutrons, and electrons held together by nuclear and electric forces in
    such a way as to be more or less stable.

    Different elements are different because they consist of different
    numbers of protons, neutrons, and electrons. We've found all the
    combinations that are stable. There might be some elements which
    contain large numbers of protons, neutrons, and electrons that are
    somewhat stable. They will be very heavy, and their properties
    can be predicted fairly well.

    Protons and neutrons are made of quarks. "Up" and "down" quarks.
    They could be replaced by more exotic particles that are made of the
    heavier "strange" and "charmed" quarks. But those heavy quarks can
    only be made in very high-energy collisions, and are very unstable,
    falling apart in a tiny fraction of a second. Aside from that, atoms
    made from these heavier quarks would have properties very similar to
    those of ordinary atoms. They would just be heavier.

    You might find other particles that go together in ways different from
    the ways atoms go together on Earth, but they either are astonishingly
    rare at the surfaces of planets and stars and in nebulae and deep space,
    or they are completely invisible, neither giving off, absorbing, reflecting,
    nor refracting light. Otherwise we would see them.

    -- Jeff, in Minneapolis

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    Quote Originally Posted by korjik View Post
    As for the 'we dont know what is out there!' arguement, that isnt really true. We see alot of the universe, and what we can see is always the same stuff. Stars a billion light years away are the same stuff as the stars around here.
    Yes, this was a major problem I had with their argument, but they argued that we simply do not know if a star over there is the same as a star over here. I'm not sure what they knew what I meant when I mentioned spectroscopy, which would explain why they dismissed it so quickly.

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    Quote Originally Posted by Lonewulf View Post
    Yes, this was a major problem I had with their argument, but they argued that we simply do not know if a star over there is the same as a star over here. I'm not sure what they knew what I meant when I mentioned spectroscopy, which would explain why they dismissed it so quickly.
    I generally agree with the problem you are having with the explanation.

    However, if one wanted a science fiction type of hand-waving.... If I remember Poul Anderson's stories I mentioned, there was a naturally occurring source of Island of Stability elements. It was a planet orbiting a supernova remnant, at a considerable distance (think Neptune or further). When the supernova went off, it was a large gas giant, that basically got stripped down to its core. The planet's core got "painted" with a lot of the stuff from the supernova and apparently the supernova process could create transuranics.

    Now, I suspect this is all based in little or no actual physics, but it is an interesting idea. And such a body would be virtually invisible to our spectroscopic techniques, as are currently most exo-solar planets.
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    Quote Originally Posted by Swift View Post
    The science fiction writer Poul Anderson wrote some stories with these concepts in them.

    I believe Nick van Rijn was in that one. His novel Mirkheim was based on the same idea, with a battle over an exceptional world loaded with "island of stability" elements.

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    Quote Originally Posted by Van Rijn View Post
    I believe Nick van Rijn was in that one. His novel Mirkheim was based on the same idea, with a battle over an exceptional world loaded with "island of stability" elements.
    He was. I was wondering when you would show up.
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    I may have to read these novels you guys are talking about. They sound intriguing.

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    Quote Originally Posted by Lonewulf View Post
    I may have to read these novels you guys are talking about. They sound intriguing.
    I remember really liking them, but it has been a long time. But now I think I need to do some re-reading.
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    We can strip electrons off atoms one at a time due to the increasing ionization energies, and measure the charge to mass ratio of the resulting ions by sending them through a magnetic field and measuring the deflection. Combine measurements of multiple ionizations, and you can measure the possible atomic masses and the the nuclear charge of each element. The nuclear charge is always an integer multiple of the charge of a proton, the atoms of a given element all have the same nuclear charge, and only atoms of a given element have that nuclear charge.

    So, we do know with great certainty that there are no gaps within the table. There's just no way to squeeze another element in there. You can't get lighter than hydrogen, so the only thing left is to add super-heavy elements on to the end...and those elements are not known for long life. The island of stability is real, but even those elements are still expected to have rather short lifetimes...the stability is relative to other superheavy elements, which tend to decay in seconds or minutes...and as others have said, they're not easy to make. There's things like positronium and dark matter, but those aren't new elements, they're different kinds of matter that don't have any place on the periodic table.

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    Quote Originally Posted by Lonewulf View Post
    The core argument on the other side was that there might be elements floating out there that we don't know about and can have no clue about until we "go out and see them".
    I hate that argument so much. It's always, to me, a sign of ignorance of what we already know and how we know it.
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    Quote Originally Posted by Swift View Post
    I generally agree with the problem you are having with the explanation.

    However, if one wanted a science fiction type of hand-waving.... If I remember Poul Anderson's stories I mentioned, there was a naturally occurring source of Island of Stability elements. It was a planet orbiting a supernova remnant, at a considerable distance (think Neptune or further). When the supernova went off, it was a large gas giant, that basically got stripped down to its core. The planet's core got "painted" with a lot of the stuff from the supernova and apparently the supernova process could create transuranics.

    Now, I suspect this is all based in little or no actual physics, but it is an interesting idea. And such a body would be virtually invisible to our spectroscopic techniques, as are currently most exo-solar planets.
    http://en.wikipedia.org/wiki/Supernova_nucleosynthesis

    It does have some basis in physics

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    Lonewulf, are they arguing that there might be an element somewhere within the bounds of the current periodic table--say, between Carbon and Silicon--that we just haven't seen yet?

    Or are they arguing that there might be an element somewhere beyond the upper boundary of the periodic table that we haven't seen yet?

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    Actually, the overall lines of their argument were that, in general, we don't know what's out there because we haven't seen it with our own eyes. But in this specific sense, they were arguing that we do not know if the stars out there are totally different than our own sun, or that we do not know if those stars may very well have produced different elements than what we are familiar with.

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    Samuel R. Delany's 1968 novel "Nova" used the plot device of increasingly stable superheavy elements as the atomic number increased beyond 300. The trans-three-hundred elements, collectively known as Illyrion, were generated in the cores of stars and were a valuable resource used for power and space travel. The story focuses on a Moby Dick-like quest to capture large quantities of Illyrion as a star goes nova rather than mine trace quantities from planetary sources.

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    Quote Originally Posted by Lonewulf View Post
    Actually, the overall lines of their argument were that, in general, we don't know what's out there because we haven't seen it with our own eyes. But in this specific sense, they were arguing that we do not know if the stars out there are totally different than our own sun, or that we do not know if those stars may very well have produced different elements than what we are familiar with.
    Have they ever looked at the sky at night? Then they've seen it with their own eyes. Astronomers & physicists have as well through telescopes and other instruments. All of the stars we've observed behave in similar ways. The absorbtion spectra (and emission spectra) of every star observed (and the number is huge) behave in the same way as the sun does. All of these can be explained by the known periodic table of elements. I agree with Gillian. Arguments like these ignore all that we do know and the conclusions that we can draw from it.
    "I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." - William Thompson, 1st Baron Lord Kelvin

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    Like my kid asking what other ways a 4x4 blue Lego block can possibly be connected to a 4x4 red one.

    That's it, kid. You've exhaustively explored the solution space.

    It's another step toward adulthood.
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

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    Quote Originally Posted by Lonewulf View Post
    Actually, the overall lines of their argument were that, in general, we don't know what's out there because we haven't seen it with our own eyes. But in this specific sense, they were arguing that we do not know if the stars out there are totally different than our own sun, or that we do not know if those stars may very well have produced different elements than what we are familiar with.
    Do these same people wonder if the people on the TV can see them. I mean, if we can see them, why can't they see us??

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    Quote Originally Posted by 01101001 View Post
    Like my kid asking what other ways a 4x4 blue Lego block can possibly be connected to a 4x4 red one.

    That's it, kid. You've exhaustively explored the solution space.

    It's another step toward adulthood.
    That's probably where they were coming from. But they were also possibly looking to "the local geek" to entertain them with more imaginative speculations. Such as maybe weak/strong/unusual circumstance interaction between baryonic and nonbaryonic (dark) matter. Though they probably didn't know thats what they were looking for beyond entertainment from the local geek.

    Like the kid who is really looking to dad for more imaginative suggestions for lego blocks than "exhausting the solution space for connecting a 4x4 blue Lego block to a 4x4 red one". He just doesn't know what to ask for. Even a kid intuits that there's more to lego blocks (and more to dad) than that. He's right about legos. He's not neccessarily right about dad.

    That's another step toward adulthood too.

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    In a way, it's a valid and even insightful question, recognizing the possibility of "unkown unknowns" as opposed to "known unknowns". The only problem is that this just doesn't happen to be a context in which such thinking is applicable, because too much of the subject is known and rather little is unknown.

    Quote Originally Posted by aastrotech View Post
    ...Such as maybe weak/strong/unusual circumstance interaction between baryonic and nonbaryonic (dark) matter.
    Other possibilities do come to my mind: matter based on quarks in pairs, quadruplets, hexes, or such instead of trios; matter based on quarks other than the up & down and/or leptons other than the electron (imagine a cluster of charms, stranges, and muons in the exact counter part arrangements to our carbon & oxygen atoms; would they still combine to form a c-s- equivalent to carbon dioxide?); whole atoms, molecules, or planets of antimatter (antiprotons, antineutrons, positrons); matter with various degrees or types of quantum entanglement or coherency, like Bose-Einstein condensates...

    However, this broadening of the scope of the question doesn't help much; it still lies mostly in the realm of known answers, whether because we know why it wouldn't work or because we've already seen it and know what it's like. But there are a few things in there that even the latest science can't answer, like why antimatter is so uncommon and whether it would really be such a perfect mirror of normal matter on complex large scales or not.

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    Quote Originally Posted by Lonewulf View Post
    Actually, the overall lines of their argument were that, in general, we don't know what's out there because we haven't seen it with our own eyes. But in this specific sense, they were arguing that we do not know if the stars out there are totally different than our own sun, or that we do not know if those stars may very well have produced different elements than what we are familiar with.
    Well this just shows they are very ignorant of physics. When you talk about the elements the science is about as sound as you can get. It isn't as complicated as lets say molecules and things like protein folding.

    The periodic table is a definition of Atoms. Atoms are defined by the number of protons they have. Protons are baryons that interact with all 4 forces (Gravity, Electromagnetic, Weak and Strong forces). Protons have a very definite charge due to the 3 quarks that they are made up of. There has never been a test that goes against the standard model when it comes to the basic physics of atoms.

    So carbon is defined by having 6 protons. It doesn't matter how many electrons or neutrons it has. It is still carbon. We can even predict attributes of the other isotopes of carbon very well along with the isotopes. An isotope is defined by the number of neutrons it has.

    Atoms don't interact long term with other types of matter besides electrons. IE a photon, neutrino, etc don't "attach" themselves to a atom giving it different qualities. Generally speaking any interaction causes a immediate change in the atom that results in some other type of atom.

    With that definition claiming that an atom on some other star with 6 protons would be something other then carbon is just pure ignorance about the science. It is literally like saying "You don't know there aren't invisible pink unicorns on that star just making it look the way it does."

    As it has been said before, everywhere we look in the universe we see signs that the baryonic matter acts the same not only everywhere we look but, since light is of finite speed, every "when" we look.

    So from them if they don't understand spectroscopy then point them to the wiki, try to explain it yourself or give up and realise they are just wilfully ignorant. I understand where they are coming from because when I was 6 I had similar thoughts brought on by sci-fi. By junior high though I understood enough about physics to understand why my old ideas would not hold up.

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    Quote Originally Posted by Amber Robot View Post
    Do these same people wonder if the people on the TV can see them. I mean, if we can see them, why can't they see us??
    I believed this when I was 4. I remember thinking that people where actually in there. Then again I didn't really think that cartoons where not real. Man my parents never had the types of conversations I've had with my son when he was 4. I had a talk to him about how you shouldn't do the stuff you do in GTA3 in real life and he looked at me with that look of disgust and said "Dad! It's just a game!" I don't think my parents talked to me much when I was a child...that could be a good thing

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    Quark elements

    What do you think could be the names of quark elements?

    I mean, we have not been able to synthesize quarks. This is hard because of quark confinement - separating coloured particles takes more energy than creating quark-antiquark pair that neutralizes the colours to white.

    But if colour is conserved, and electric charge certainly is conserved, what are you going to do with a free quark which has no mate in the entire Universe? You cannot neutralize a quark. A free up quark is charge +2/3... add an electron, and you get an ion with charge -1/3. An ion whose spectroscopic properties can be predicted from quantum mechanic and electromagnetism (with a small uncertainty due to unknown rest mass of a free up quark) - and whose chemical properties are strictly predictable from first principles.

    If you dissolve some up quarks in water and apply electric current, will the up quark go to cathode (charge +2/3) or anode (quark plus electron give charge -1/3)?

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