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# Tag Info

45

Much of mass is just binding energy, so in a chemical reaction the electrons rearrange themselves and energy is released and the total mass of the molecules goes down (in an exothermic reaction, for example). The same is true for common nuclear reactions like spontaneous fission of uranium, with the caveat that some important nuclear reactions do involve ...

31

First off, I'd like to point out, because the term comes up often, in strict usage there is no such thing as "pure energy". Energy is not a stuff, as in particles, but a number that is associated with stuff, a quantity, though that quantity can indeed be thought of as acting, given its conservation property, like a sort of intangible "stuff" that you can put ...

18

Einstein, in his famous but rarely-read paper "Does inertia of a body depend upon its energy content?", didn't write that matter (or, better, mass) can be converted into energy. The way he stated its result was: $$\Delta E = \Delta m \cdot c^2,$$ i.e. in the rest frame of any system, variations of mass and variations of energy (of the system) are ...

10

To start with the $m$ in $E=mc^2$ is the relativistic mass, and in particle physics this is out of use it causes confusion. One uses four vectors , where the "length" of the four vector is the invariant mass, uniquely identified with elementary particles, and with systems of elementary particles. Four vectors are good in keeping track of energy, as one of ...

9

The neutrino creating reactions (fusions, decays, and fissions) that take place in the core of the sun are all low enough in energy that they can only produce electron neutrinos. However, neutrinos mix (because they propogate in mass states which do not correspond to the flavor states in which they are produced and detected), and because the energy of the ...

8

The answer as you can see from the comments differs whether you are asking about the residual strong force (nuclear force) or the strong force between quarks inside neutrons and protons. residual strong force You can read a lot on this site about whether the nuclear force is attractive at large distances and repulsive at short distances. Though, this is ...

4

There can also be blackbody (thermal) antineutrino and neutrinos of all flavors, which are emitted during type-II supernovae core collapse. Here is a figure from H.-Thomas Janka, Neutrinos from type-II supernovae and the neutrino-driven supernova mechanism (reprint from: Conference Proceedings Vol. 40: "Frontier Objects in Astrophysics and Particle Physics")...

4

The overall energy yield of the reactions is not so difficult to measure - it simply amounts to measuring the masses of the nuclei and using the Einstein $E = mc^2$ formula - subtract the mass of the nucleus from the sum of masses of protons and and neutrons within it and that is your binding energy. Experimentally this is done using the methods of mass ...

3

You are basically asking about mass energy equivalence, and nuclear reactions. And you would like to know what happens to the (I assume rest) mass and matter in the process. The mass–energy formula also serves to convert units of mass to units of energy (and vice versa), no matter what system of measurement units is used. However, use of this formula in ...

3

I want to address the "repulsive" of color interactions part and why there is not much in literature discussing it. How does "repulsion" work for electromagnetic interactions? two like charges repel the closer they are and if point charges an infinite repulsion would exist in overlap, because of the $1/r{2}$ behavior of the electric field. At the ...

3

As pointed out in PM 2Ring's comment, storage of enriched U-235 is done with great care. This is of particular concern in facilities which either enrich raw uranium or reprocess reactor fuel or the components of decommissioned atomic and nuclear weapons, or where radioactive processing waste is stored. In a process line handling uranium, each machine in ...

2

The reason metal fatigue happens over time is that the material has "memory": solid crystals and their interfaces are deformed and changed, dislocations introduced, and microscopic cracks develop. If you leave the paperclip for some time and then start deforming it again the deformations add up. This does not happen in liquids like water, where molecules ...

2

The decay must satisfy both the conservation of energy and conservation of linear momentum. I will not use a relativistic treatment here. Assume that an amount of energy $E$ is liberated (converted from rest energy to kinetic energy) during the fission. We can then write down both conservation equations, CLM: $m_{1}v_{1} = m_{2}v_{2}$ COE: $\frac{1}{2}m_{... 2 Graeme Heald seems to be a kook with an engineering degree. Physics Essays is basically a vanity-publishing operation. E.g., it has published papers by kooks like Adrian Sfarti and Mike Fontenot. The Penrose singularity theorem doesn't apply to fermions This is not true. The only condition on the matter fields is the null energy condition. The WP ... 2 If you had a$1M_{\odot}$star made of pure He, then it would not have a radius of$1R_{\odot}$. Assuming that it could find a way to cool, then it would continue to contract in size until its core become hot enough to ignite the triple alpha nuclear reaction that starts to transform the He into Carbon. I am unaware of any numerical models which hypothesize ... 1 The critical mass can be estimated as follows: You take a subcritical mass of given shape and strike it with a brief pulse of fast neutrons. This induces a burst of fission activity inside the subcritical mass, the size of which is measured. You repeat the experiment many times with a slightly larger pulse of neutrons each time and record the responses, ... 1 Any estimate of a critical mass is going to require a mixture of theory and experimental data. Nuclear physics was in a very primitive stage in 1945, e.g., the nuclear shell model by Maria Goeppert Mayer et al. was not really developed in any mathematical detail until about 4 years later. The WP article "Critical mass" actually has quite a nice treatment of ... 1 I think it is technically incorrect to say that gravity "overpowers" neutron degeneracy, from any given local frame on the neutronium bulk, pressure doesn't magically surge or drop when the event horizon is formed. Black holes do not form because of some failure in the ability of the exclusion principle to keep fermions from overlapping In other words, it ... 1 if they are suggesting the theoretical formation of heavy elements in a new type of periodic table similar to the proposed antimatter table or are they only suggesting a new type of exotic matter, such as dark matter? Neither. The existence and properties of antimatter elements is trivial theoretically. They have the same properties as normal matter. Dark ... 1 You might profit from the Introduction to unitary symmetry book by P Carruthers in learning the index language of tensoring SU(N) representations, but it is obvious from your comments that this would be runaway overkill, as you just want quark wavefunctions of hadrons, gotten far more directly and, in the case of SU(2), same as in undergraduate QM spin ... 1 One has to clarify what quantum mechanics means. It means that the appropriate solutions of the QM differential equations define the interactions, definite wavefunctions$ψ$which will give probability distributions for the system under study by using$ψ^*ψ$. That is what can be measured, not an orbit, but an orbital. In this framework, there are bound ... 1 How can I decide if there should or should not be term corresponding to the relative angular momentum? In particular why isn't it there on the gamma decay problem? Such a term should always exist, but the orbital angular momentum might not change. This may be the case in the decay you refer to, but you haven't given any information about it. In the ... 1 Considering a radioactive nucleus, let the initial number of nuclei be$N_o$with its disintegration constant$\lambda$. From it's first order decay/radioactive decay law,$N(t)=N_o e^{-\lambda t}$( let this be equation$\boxed{1}$) is the number of nuclei left at a general time t. The lifetime of each$dN\$ nuclei which decays at a given instant is NOT the ...

1

Each unstable nucleus, in a given sample of radioactive matter consisting of nuclei of the same type, decays after a certain period of time. If you add up all those times and then divide the sum by the number of unstable nuclei in the beginning you obtain the average time for an unstable nucleus to decay. This average time is often called the (average) ...

1

The graphite displacer improved the efficiency of the cycle by improving the geometry and 'coupling' between the upper and lower active sections of the core when the control rod was fully withdrawn. At the 'full out' position the displacer improves the flux pattern and reduces the amount of heat absorbed by the Control Rod Channel Cooling System. Allowing ...

1

Liquid water both moderates and captures neutrons. Steam (gaseous water) does neither to any effect. At the initiation of the "pump run-down test" there was very little steam production in the fuel channels (thermal power <7%). An expected consequence of the "test" was a drop in Steam Separator (and reactor coolant) pressure as the #8 Turbine-Generator ...

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