# Size of Nucleus to rest of Atom and other questions **URL:** \ **Category:** Factual Questions\ **Created:** [March 24, 2015, 5:03pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872 "2015-03-24T17:03:12Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Robert163](https://avatars.discourse-cdn.com/v4/letter/r/4af34b/32.png) [@Robert163](https://boards.straightdope.com/u/Robert163)\ **Post date:** [March 24, 2015, 5:03pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/1 "2015-03-24T17:03:12Z")
When I hear statements like, the size of the Nucleus in proportion to the rest of the Atom is like the size of a soccer ball in proportion to the whole stadium… or, statements like, there are more Atoms in your fingertip than there are stars in all of the galaxies of the Universe… well if Atoms are really that small, how can we know for sure that our statements are correct? ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [March 24, 2015, 5:45pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/2 "2015-03-24T17:45:38Z")
Maybe read this article first, and then come back if you have more questions? > **[Atom](https://en.wikipedia.org/wiki/Atom)** > > An atom is a particle that consists of a nucleus of protons and neutrons surrounded by a cloud of electrons. The atom is the basic particle of the chemical elements, and the chemical elements are distinguished from each other by the number of protons that are in their atoms. For example, any atom that contains 11 protons is sodium, and any atom that contains 29 protons is copper. The number of neutrons defines the isotope of the element. > Atoms are extremely small, typically around 100 picomet... ---
**Author:** ![Robert163](https://avatars.discourse-cdn.com/v4/letter/r/4af34b/32.png) [@Robert163](https://boards.straightdope.com/u/Robert163)\ **Post date:** [March 24, 2015, 5:50pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/3 "2015-03-24T17:50:22Z")
> [@Lemur866](#): > > Maybe read this article first, and then come back if you have more questions? > > [Atom - Wikipedia](http://en.wikipedia.org/wiki/Atom) I will. But my real question is, just from curiosity sake… how do we know the physicists have gotten it right, if an Atom is too small to see? ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [March 24, 2015, 6:14pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/4 "2015-03-24T18:14:48Z")
[Images of individual atoms](https://www.google.com/search?newwindow=1&site=&tbm=isch&source=hp&biw=1289&bih=608&q=individual+atoms&oq=individual+atoms&gs_l=img.3..0j0i30j0i24l4.1114.3417.0.4485.16.10.0.6.6.0.89.753.9.9.0.msedr...0...1ac.1.62.img..1.15.775.FG82EBPnP-k). The more general answer to your question is that hidden things can have observable effects which can be predicted by theory and confirmed by experiment. That’s true for atoms, it’s true for the interior of the earth, it’s true for black holes, it’s true for superconducting materials, it’s true for zillions and zillions of things. This is the underlying assumption behind all science and for that matter all knowledge. And the specific answer to your question is answered in the link you haven’t bothered to read. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 24, 2015, 6:38pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/5 "2015-03-24T18:38:06Z")
that true. some physics is big and some small. some biology is big and some small. all of chemistry is small. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [March 24, 2015, 6:45pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/6 "2015-03-24T18:45:02Z")
> [@Exapno\_Mapcase](#): > > [Images of individual atoms](https://www.google.com/search?newwindow=1&site=&tbm=isch&source=hp&biw=1289&bih=608&q=individual+atoms&oq=individual+atoms&gs_l=img.3..0j0i30j0i24l4.1114.3417.0.4485.16.10.0.6.6.0.89.753.9.9.0.msedr...0...1ac.1.62.img..1.15.775.FG82EBPnP-k). Incidentally, “A Boy and his Atom” deserved an Oscar for technical achievement. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [March 24, 2015, 7:08pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/7 "2015-03-24T19:08:41Z")
> [@Robert163](#): > > I will. But my real question is, just from curiosity sake… how do we know the physicists have gotten it right, if an Atom is too small to see? Let’s put it another way. Can you see a radio wave? No, you cannot. So how do you know radio waves exist? Well, you turn on your radio, and sounds come out. So you are using a machine that you built to detect a phenomenon that you can’t detect directly with your unaided senses. Same thing if you look through an infra-red camera. You see an infra-red image that your eyes cannot normally detect. So there are lots and lots of things out there that you can’t normally see, hear, smell, taste, or touch, but they still exist, and you can prove they exist and have certain properties by observing the effect those things have on things that you can see or hear or smell or touch. Or to put it another different way, go to your kitchen and take out a container of salt. Pour the salt in a pile, and look at it. You can see the salt, right? But can you see the saltiness of the salt? You know that if you taste the salt, you’ll taste saltiness. But if you just use your eyes, it might as well be white sand, or sugar, or crystal meth. Our eyes are just one tool we have to understand the universe. We have other senses that can detect things our eyes can’t detect. Those senses work according to certain physical principles, and if you ever lost your ability to taste there are still chemical or physical tests you could run to distinguish between salt crystals and sugar crystals. And there are lots of things in the universe that we don’t have direct physical senses to detect. But we can still do tests to discover the properties of those things, just like even if we couldn’t taste saltiness we could still figure out ways to tell salt from sugar. ---
**Author:** ![Robert163](https://avatars.discourse-cdn.com/v4/letter/r/4af34b/32.png) [@Robert163](https://boards.straightdope.com/u/Robert163)\ **Post date:** [March 24, 2015, 7:21pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/8 "2015-03-24T19:21:40Z")
> [@Exapno\_Mapcase](#): > > [Images of individual atoms](https://www.google.com/search?newwindow=1&site=&tbm=isch&source=hp&biw=1289&bih=608&q=individual+atoms&oq=individual+atoms&gs_l=img.3..0j0i30j0i24l4.1114.3417.0.4485.16.10.0.6.6.0.89.753.9.9.0.msedr...0...1ac.1.62.img..1.15.775.FG82EBPnP-k). > > The more general answer to your question is that hidden things can have observable effects which can be predicted by theory and confirmed by experiment. That’s true for atoms, it’s true for the interior of the earth, it’s true for black holes, it’s true for superconducting materials, it’s true for zillions and zillions of things. This is the underlying assumption behind all science and for that matter all knowledge. That was a great answer. Thank You. > [@](#): > > And the specific answer to your question is answered in the link you haven’t bothered to read. I tried reading it. But since I’ve slept about 5 hours in the last 48 hours I’m finding it a bit hard to read or think of anything serious at the moment. ---
**Author:** ![Robert163](https://avatars.discourse-cdn.com/v4/letter/r/4af34b/32.png) [@Robert163](https://boards.straightdope.com/u/Robert163)\ **Post date:** [March 24, 2015, 7:24pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/9 "2015-03-24T19:24:22Z")
> [@Lemur866](#): > > Let’s put it another way. Can you see a radio wave? No, you cannot. So how do you know radio waves exist? Well, you turn on your radio, and sounds come out. So you are using a machine that you built to detect a phenomenon that you can’t detect directly with your unaided senses. > > Same thing if you look through an infra-red camera. You see an infra-red image that your eyes cannot normally detect. > > So there are lots and lots of things out there that you can’t normally see, hear, smell, taste, or touch, but they still exist, and you can prove they exist and have certain properties by observing the effect those things have on things that you can see or hear or smell or touch. > > Or to put it another different way, go to your kitchen and take out a container of salt. Pour the salt in a pile, and look at it. You can see the salt, right? But can you see the saltiness of the salt? You know that if you taste the salt, you’ll taste saltiness. But if you just use your eyes, it might as well be white sand, or sugar, or crystal meth. > > Our eyes are just one tool we have to understand the universe. We have other senses that can detect things our eyes can’t detect. Those senses work according to certain physical principles, and if you ever lost your ability to taste there are still chemical or physical tests you could run to distinguish between salt crystals and sugar crystals. And there are lots of things in the universe that we don’t have direct physical senses to detect. But we can still do tests to discover the properties of those things, just like even if we couldn’t taste saltiness we could still figure out ways to tell salt from sugar. Another great explanation. Thank You. ---
**Author:** ![minor7flat5](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/minor7flat5/32/258_2.png) [@minor7flat5](https://boards.straightdope.com/u/minor7flat5)\ **Post date:** [March 24, 2015, 8:24pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/10 "2015-03-24T20:24:33Z")
Admittedly, that Wikipedia page is a bit intimidating for a full read-through. The answers to these questions come from experimentation. Your nucleus comment is a perfect example. Take a look at [Ernest Rutherford’s Gold Foil Experiment](http://chemed.chem.purdue.edu/genchem/history/rutherford.html)… That was the experiment that helped me get my head around how someone can make statements about invisible things. The quote I have always remembered (taken from the linked page): > [@](#): > > Many years later, reflecting on his reaction to these results, Rutherford said: “It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.” ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 24, 2015, 9:52pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/11 "2015-03-24T21:52:21Z")
> [@Robert163](#): > > I will. But my real question is, just from curiosity sake… how do we know the physicists have gotten it right, if an Atom is too small to see? Because the math works out to a very high degree of precision. Sorry, that is probably not a very satisfying answer unless you are a physicist (in which case it is decidedly satisfying if for no other reason than to validate the years spent trying to make sense of wavefunctions, Hilbert spaces, Wigner and Weyl transforms, renromalization, et cetera) but that’s how it is. Reality, such as it is, is defined by behaving the way that we predict that it should. Just be glad that you don’t live in the Warner Bros. universe. However (read on at peril to your sanity) the reality at a fundamental level is even worse than that. The behavior at the level that quantum mechanical effects dominate is that those particles which make up the atom–electrons, which are fundamental, and protons and neutrons (baryons) that are made up of other fundamental particles called quarks that cannot ever be observed singularly in an “unconfined” (not part of a baryon)–don’t actually exist as “solid” matter at all; they’re actually all just fields, the interaction of which gives the appearance of solidity. See [THREAD=299054]“Why can’t my hand go through my desk?”[/THREAD] I did warn you not to keep reading. Curiosity–and a jerk called Erwin Schrödinger with a penchant for randomly poisoning felines to make a point–killed the proverbial cat. Stranger ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [March 24, 2015, 10:22pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/12 "2015-03-24T22:22:22Z")
Fortunately for cats, Schrödinger only virtually killed abstract cats with mathematical models thereof. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [March 24, 2015, 11:16pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/13 "2015-03-24T23:16:57Z")
> [@Stranger\_On\_A\_Train](#): > > Curiosity–and a jerk called Erwin Schrödinger with a penchant for randomly poisoning felines to make a point–killed the proverbial cat. If I’m reading you right, your objection is to the randomness. I agree completely. Felines should be deliberately targeted en masse. 😃 ---
**Author:** ![Robert163](https://avatars.discourse-cdn.com/v4/letter/r/4af34b/32.png) [@Robert163](https://boards.straightdope.com/u/Robert163)\ **Post date:** [March 24, 2015, 11:19pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/14 "2015-03-24T23:19:34Z")
> [@minor7flat5](#): > > Admittedly, that Wikipedia page is a bit intimidating for a full read-through. > > The answers to these questions come from experimentation. > Your nucleus comment is a perfect example. > > Take a look at [Ernest Rutherford’s Gold Foil Experiment](http://chemed.chem.purdue.edu/genchem/history/rutherford.html)… > > That was the experiment that helped me get my head around how someone can make statements about invisible things. > > The quote I have always remembered (taken from the linked page): > [@Stranger\_On\_A\_Train](#): > > Because the math works out to a very high degree of precision. Sorry, that is probably not a very satisfying answer unless you are a physicist (in which case it is decidedly satisfying if for no other reason than to validate the years spent trying to make sense of wavefunctions, Hilbert spaces, Wigner and Weyl transforms, renromalization, et cetera) but that’s how it is. Reality, such as it is, is defined by behaving the way that we predict that it should. Just be glad that you don’t live in the Warner Bros. universe. > > However (read on at peril to your sanity) the reality at a fundamental level is even worse than that. The behavior at the level that quantum mechanical effects dominate is that those particles which make up the atom–electrons, which are fundamental, and protons and neutrons (baryons) that are made up of other fundamental particles called quarks that cannot ever be observed singularly in an “unconfined” (not part of a baryon)–don’t actually exist as “solid” matter at all; they’re actually all just fields, the interaction of which gives the appearance of solidity. See [THREAD=299054]“Why can’t my hand go through my desk?”[/THREAD] > > I did warn you not to keep reading. Curiosity–and a jerk called Erwin Schrödinger with a penchant for randomly poisoning felines to make a point–killed the proverbial cat. > > Stranger I can definitely understand that experimentation and mathematics will tell us the answer… it’s worked in so many other situations. ---
**Author:** ![PatriotGrrrl](https://avatars.discourse-cdn.com/v4/letter/p/9dc877/32.png) [@PatriotGrrrl](https://boards.straightdope.com/u/PatriotGrrrl)\ **Post date:** [March 24, 2015, 11:35pm UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/15 "2015-03-24T23:35:59Z")
Or rather “the answer” is the best explanation we have for so many, many observations and experimental results. You could explain everything by saying we are all living in the Matrix and reality is all an illusion, but that is not as useful as believing that there are things like atoms and radio waves. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 25, 2015, 12:25am UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/16 "2015-03-25T00:25:09Z")
The small-nucleus theory has a pretty straightforward explanation. Let’s suppose you have a stadium-sized… thing of unknown composition. All you know is its mass–which isn’t much. If that mass were evenly distributed, you’d have something close to a vacuum inside. You don’t know that it’s evenly distributed, though. So you do what any red-blooded American would do: you shoot it. Over and over until you’re bored. Mostly, you get the expected result: the bullets pass straight through, completely unaffected. This is consistent with the idea that the object is just lightly filled with some substance, and that your bullets barely interact with it. However, every so often–maybe one in a billion–your bullets bounce back! This couldn’t possibly happen if your object is all wispy mass. So you have another theory: what little mass you have is concentrated in the center in a hard lump. It’s not much; just a small steel ball at the center of your stadium. Most of the time, you just miss it completely. But every so often your bullet hits it and ricochets back toward you. That one-in-a-billion chance proves that there is a dense lump in the middle of your object. Even though you can’t actually see it, there’s no other way to get that kind of ricochet, so you know it must be there. This is more or less just what happened with Rutherford’s gold-foil experiment that **minor7flat5** mentioned, and disproved the so-called “plum pudding” model, which claimed that the mass (and positive charge) was all spread out over the inside of the atom. Alpha particles (the “bullets”) bounced back, proving that a dense nucleus existed. In general, physicists love shooting particles each other. The study of _scattering_ is how they figure out what’s going on. ---
**Author:** ![Robert163](https://avatars.discourse-cdn.com/v4/letter/r/4af34b/32.png) [@Robert163](https://boards.straightdope.com/u/Robert163)\ **Post date:** [March 25, 2015, 1:17am UTC](https://boards.straightdope.com/t/size-of-nucleus-to-rest-of-atom-and-other-questions/715872/17 "2015-03-25T01:17:01Z")
> [@Dr.Strangelove](#): > > The small-nucleus theory has a pretty straightforward explanation. > > Let’s suppose you have a stadium-sized… thing of unknown composition. All you know is its mass–which isn’t much. If that mass were evenly distributed, you’d have something close to a vacuum inside. > > You don’t know that it’s evenly distributed, though. So you do what any red-blooded American would do: you shoot it. Over and over until you’re bored. > > Mostly, you get the expected result: the bullets pass straight through, completely unaffected. This is consistent with the idea that the object is just lightly filled with some substance, and that your bullets barely interact with it. > > However, every so often–maybe one in a billion–your bullets bounce back! This couldn’t possibly happen if your object is all wispy mass. > > So you have another theory: what little mass you have is concentrated in the center in a hard lump. It’s not much; just a small steel ball at the center of your stadium. Most of the time, you just miss it completely. But every so often your bullet hits it and ricochets back toward you. That one-in-a-billion chance proves that there is a dense lump in the middle of your object. Even though you can’t actually see it, there’s no other way to get that kind of ricochet, so you know it must be there. > > This is more or less just what happened with Rutherford’s gold-foil experiment that **minor7flat5** mentioned, and disproved the so-called “plum pudding” model, which claimed that the mass (and positive charge) was all spread out over the inside of the atom. Alpha particles (the “bullets”) bounced back, proving that a dense nucleus existed. > > In general, physicists love shooting particles each other. The study of _scattering_ is how they figure out what’s going on. Wow thanks so much for explaining that!!!