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53

Wow, this one has been over-answered already, I know... but it is such a fun question! So, here's an answer that hasn't been, um, "touched" on yet... :) You sir, whatever your age may be (anyone with kids will know what I mean), have asked for an answer to one of the deepest questions of quantum mechanics. In the quantum physics dialect of High Nerdese, ...

37

Neither of those statements are true. It's an easy approximation to make: a neutron star has all of that 'space' removed from between nucleons --- so we just need to know how big a neutron star of mass equal to the solar system would be. Well, the only significant mass is the sun (jupiter is about 1% the mass of the sun---negligible). If the sun were ...

29

You are right, the planetary model of the atom does not make sense when one considers the electromagnetic forces involved. The electron in an orbit is accelerating continuously and would thus radiate away its energy and fall into the nucleus. One of the reasons for "inventing" quantum mechanics was exactly this conundrum. The Bohr model was proposed to ...

21

I don't think that this is a physics restriction, but one of current engineering capability. As you link points out, using 12 atoms allowed the information to be retained without effecting the information stored next to it. You will also need enough data-mass to allow for the reading and writing of the information without affecting the data next to the one ...

16

No, there aren't any holes like that in the EM spectrum. There are other ways of creating photons than by having electrons bound in atoms transition from one level to another. (For example, you can create pretty much any frequency of photon you want by accelerating a free electron.)

14

Yes, quantum mechanics – even non-relativistic quantum mechanics for several electrons orbiting nuclei – fully, quantitatively, and comprehensively explains all of chemistry (including biochemistry and, in fact, biology). This fact has been known since the late 1920s. To understand the periodic character of the properties of the elements, one must realize ...

14

This is quite far from a silly thought although this is not apparent at first sight. Apart from a couple of details which are well understood and have firm physics behind them - such as the fact that deuterium and tritium exist in some proportion and the hyperfine-structure distinction between ortho- and parahydrogen, as far as we can tell all hydrogen atoms ...

11

Short answer: The space between the nucleus and the electron is not empty space, it is filled with an electron cloud. (You will understand this answer better if you read the long answer) Long answer: Firstly, physics is a description of what we can observe. Depending on the scale of which you are describing, physicists, over the years, have different ...

11

This problem has been extensively studied. These are some references that I think answer various aspects of your question. I would say that it is not exactly a solved problem. In an expanding universe, what doesn't expand? Size of a hydrogen atom in the expanding universe Evolution of the Solar System and the Expansion of the Universe Multiparticle ...

11

For any kind of magnetic data storage you need a magnetic state that is stable over time. The magnetic moment of an isolated single atom does not have any preferred direction, therefore the energy states are degenerated. The 12 atoms used in this experiment is not a lower limit, in principle it can also work with 2 atoms given the right magnetic ...

10

In addition to dmckee's answer this link summarizes the experiments of antiprotons catching protons and neutrons, creating temporary nuclei. It is the symmetric state to the one in the question : an anti-proton-neutron nucleus that lasts for a bit (fig 5.7). Anti-protons can be made in abundance and controlled experimentally because they are charged, ...

10

If you could compress the mass into that small a space, it would collapse into a black hole, at which point the notion of "size" becomes harder to define, with space-time being so warped. The "event horizon" radius would be about 3 km, if I get the formula correctly. The idea of "there's a lot of space in atoms" comes from computations which state that the ...

10

Carbon-14 makes up about 1 part per trillion of the carbon atoms around us, and this proportion remains roughly constant due to continual production of carbon-14 from cosmic rays. The half life of carbon-14 is about 5,700 years, so if we measure the proportion of C-14 in a sample and discover it's half a part per trillion, i.e. half the original level, we ...

9

Let's talk about the balloon first because it provides a pretty good model for the expanding universe. It's true that if you draw a big circle then it will quickly expand as you blow into the balloon. Actually, the apparent speed with which two of the points on the circle in a distance $D$ of each other would move relative to each other will be $v = H_0 D$ ...

9

Okay, so I did some poking around and the 66th-75th editions of the CRC Handbook of Chemistry and Physics all have the incorrect atomic mass of Cu-63 [62.939598], and from 76th edition on they seem to have figured it out. Those isotope mass tables are put together from a number of sources, so it's hard (time consuming) to tell exactly where the error came ...

8

In particle physics, you have to be specific about what you mean by breaking down a particle: A neutron in an atom can decay into a proton, an electron, and an electron-antineutrino. But this does not mean that a neutron is made of a proton, an electron and an electron-antineutrino. What the neutron is made of are three quarks (one up and two down). If by ...

8

While quantum mechanics explains the gross features of the periodic system, many fine details of the periodic table of elements are computable numerically from various approximations to QED, but are conceptually ill understood. See, e.g., Eric R. Scerri, How Good Is the Quantum Mechanical Explanation of the Periodic System? Journal of Chemical Education ...

8

As a useable heuristic I would go with something along the lines of the intermolecular forces between the surface molecules of the bodies are comparable to the scale of one-to-one intermolecular forces between nearby{*} molecules due to other components of the same body You could make it a little more strict by replacing "comparable to" with ...

8

In any proper quantum mechanical understanding of the atom, a bound electron does not have a position and follow a path (i.e. have a time-varying position) in the sense that it would have in a classical or semi-classical theory. Instead the electron "has a state" or "occupies an orbital" (an orbital not a orbit!), and because there is not a path there is ...

8

For the first rows in the periodic table, this can easily be explained by the fact that electrons possess four quantum numbers (usually $n$, $l$, $m_l$ and $m_s$). These numbers are restricted as such: $$n = 1, 2, 3, ...$$ $$l = 0, 1, 2, ..., n - 1$$ $$m_l = -l, -l + 1, ..., 0, ..., l - 1, l$$ $$m_s = -\frac{1}{2}, \frac{1}{2}$$ By Pauli's ...

8

If you mean to ask "do the orbital radial probability distributions overlap?", the answer is yes: Image Credit making the electrons in each orbital "meet" at some point As you can see from the image, the electron orbitals are not position eigentstates. If you're imagining two point-like electrons in different orbitals colliding, you're not thinking ...

7

Since both references give the same percentages and the same overall atomic weight, an easy calculation shows that this only works out for the number in the first link, therefore the second decimal should be 2. (And I think it would be nice to contact the webmasters of the second link.)

7

The big change in understanding that happened with Quantum Physics is the idea that the universe is random, rather than clockwork, at its lowest level. The double slit experiment The classic example is that if I fire a particle (e.g. an atom) at board with 2 slits in it, the particle could go through slit A, or slit B, before hitting a plate at the back. ...

7

a great topic. First, ten gigatesla is only the magnetic field near a magnetar - a special type of neutron star. They were discussed e.g. in this Scientific American article in 2003: http://solomon.as.utexas.edu/~duncan/sciam.pdf Ordinary neutron stars have magnetic fields that are 1000 times weaker than that. It is true that in the magnetar stars, atoms ...

7

Its due to the WP-Rayleigh–Taylor instability: it is an instability of an interface between two fluids of different densities, which occurs when the lighter fluid is pushing the heavier fluid. Hot hair raises and colder goes down. A Mushroom cloud formed by hot wet air : google for images or videos of 'Rayleigh–Taylor'

7

Given that the valence quark content of a proton is $(uud)$ and that of a anti-neutron in $(\overline{udd})$ the answer is that sooner later some of the constituent quarks will annihilate and you get a spray assorted particles. The lifetime of such a nucleus will depend on it's orbital angular momentum, with s-states being very short lived and high angular ...

7

Short answer: the strong nuclear force. The strong nuclear force binds nucleons (protons and neutrons) together. It is a very short-range force, which is why it only acts over distances on the scale of atomic nuclei. There is repulsion between the protons, which is why, as the number of protons goes up, more and more neutrons are required to stabilize the ...

7

First you say It's easy to visualise and comprehend the excited states of electrons, because they exist on discrete energy levels that orbit the nucleus By way of preparation, I'll note that in introductory course work you never attempt to handle the multi-electron atom in detail. The reason is the complexity of the problem: the inter-electron effects ...

7

The "removing the space" and "atoms are mostly empty" memes for atomic nuclei are interesting, but I do grit my teeth every time I hear this. A description that fits better with me might be "remove the electromagnetic force". Concepts of size and space of particles are based on how they interact using forces. There is no evidence that fundamental particles ...

7

I think the problem here is with E&M, and it is in the assumptions implicit to the question. Here is the assumption: the electron orbiting around the nucleus has an acceleration. Therefore it radiates and loses energy, until it would collapse with the nucleus. This statement can be demolished in short order, considering the topic of a ...

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