I've read several other answers on here, but I still don't understand. Why do both fission and fusion release energy? I know the masses drop, but then why do the masses drop on both? Fusion is taking two small nuclei, adding them together, and creating a bigger atom, why should this bigger atom have less energy? Is it because more of the mass gets stored in the strong force? Then what determines how much energy is released?  The same goes for fission. A larger molecules being broke apart will approach a more stable max-energy-per-interaction form. This means that more energy should go into the bonds (I think) which would mean less mass, but still why does energy get released, and not just simply into the bonds?
123738
I understand why fission generates large amounts of energy when the nucleus is split, but then why does fusion generate such large amounts of energy. If fission releases energy when some mass is lost as energy, then shouldn't the fusion process absorb energy to fuse nuclei together?  I also am curious as to where the energy released from fusion comes from, while fission releases some of the energy of the strong nuclear force.
40574
How does  work? I'm wondering why matter and antimatter actually annihilates if they come into contact. What exactly happens? Is that a known process? Is it just because of their different charges? Then what about neutrons and anti-neutrons? I guess that would be about their quarks, but wouldn't it be very unlikely what all of their individual quarks would actually touch the anti-quarks of the other (anti-)neutron at exactly the same time?
45644
I understand that assuming light is quantized implies that if a lower energy interacts with  metal, it is possible that that quanta will not have enough energy to eject the electron. What prevents two quanta from interacting with the electron at the same time, though, and summing to have enough energy to release the particle. Indeed, what if two separate light rays of the same frequency impact the electron, why can't that free it?
11654
We know that the sum of the masses of the quarks in a proton is approximately $9.4^{+1.9}_{-1.3}~\text{MeV}/c^2$, whereas the mass of a proton is $\approx931~\text{MeV}/c^2$. This extra mass is attributed to the kinetic energy of the confined quarks and the confining field of the strong force. Now, when we talk about energetically favourably bound systems, they have a total mass-energy less than the sum of the mass-energies of the constituent entities. How does a proton, a bound system of quarks with its mass-energy so much more than its constituent entities, remain stable? The strong force and other energetic interactions supposedly contribute this mass-energy by the mass-energy equivalence principle, but how exactly does this occur?
106610
My question is loaded with assumptions so to minimize them, I would like to ask it with respect to an electron and anti-electron annihilating.  When I think of annihilation, I think of electron and positron turning into energy where the total energy represents the combined masses plus kinetic energy each particle had prior to the collision and annihilation (Assumption 1).  But, doesn't the field of each charged particle also have an energy content and does this energy content of the charged particle field show up in the final energy?  I have never seen this though, only the sum of the mass energy. (Assumption 2 possibly).  Also, how is it that the masses annihilate if they are not ANTI to each other.  Mass has no opposite like charge does (or other things).  Does the annihilation of the charges also somehow annihilate the masses and if this is the case, that would require energy so this energy should show up somewhere.  Or is there some other opposite "thing" that results in annihilation of mass?  Physicists used to think that electron mass was actually the inertia of moving charge in a field (or something like that).  Is there some kind of connection between mass and charge such that charge annihilation is also mass annihilation?
114425
When an electron absorbs a photon, it gets into a higher energy state and goes into the upper orbit/shell.  Does (rather should) this absorption of energy also have an impact on its mass (although incredibly small)?  Can we even measure the mass of an electron while it is it still bound to the nucleus?
6813
Considering that $7$ TeV is more or less the same kinetic energy as a mosquito flying, why is it considered to be a great amount of energy at the LHC?  I mean, a giant particle accelerator that can only provide 7 TeV of energy? (14 in the mass center, if I understood well). Is it because particles are so small that this amount of energy, in proportions, is then really huge?
64683
When I add up the mass of 6 protons and 6 neutrons in amu, I get a mass that is greater than the mass of carbon. I thought that it should be the other way around, because I have not including binding energy when I add up the mass of the protons and neutrons.  Proton: 1.007276466812 u  Neutron: 1.00866491600 u  6(1.007276466812)+6(1.00866491600)=12.099  Carbon: 12 u  Why is this so?
40049
I would like to know where gravity gets its energy to attract physical bodies?  I know that the law of conservation states that total energy of an isolated system cannot change. So gravity has to be getting its energy from somewhere, or else things like hydropower plants wouldn't be able to turn the power of the falling water into a spinning rotor.  Just to be clear, Lets create an example:  Lets say we have two objects with equal mass close to each other. So gravity does its job and it pulls each other closer, this gets turned into kinetic energy. This is where I'm lost. According to the law of conservation energy can't be created or destroyed and the kinetic energy comes from the gravitational pull so where does the gravitational pull gets its energy.  If that energy isn't being recycled from some where else then that means you have just created energy, therefore breaking the law of conservation.
7223
My question isn't how they receive the energy to jump, but why.  When someone views an element's emission spectrum, we see a line spectrum which proves that they don't exist outside of their orbitals (else we would see a continuous spectrum).  Electrons can be released in the form of beta decay, thus proving that they are capable of traveling outside of orbitals contrary to the statement my teacher said that they stay within orbitals. Then, to add to the confusion, the older model of rings floating around a nucleus has, from what I can tell, been outdated, which would support this model. My teacher's explanation was that the electrons made a quantum jump of some kind. How do electrons move between orbitals or do we know how they jump, excluding the reason that energy causes them to jump, and why are positrons formed sometimes instead of electrons in Beta decay?  When I'm asking "how do electrons jump" I would like to know how an electron can jump between each orbital such as how it moves and how it knows where to jump since it appears to be a jump where the electron doesn't slow into a orbital position. Specifically how they jump what is this Atomic electron transition, I understand that they jump and that they do this through absorbing and releasing energy but what is this Atomic electron transition other than what is already on the wikipedia article .
11628
If you take any large nucleus and add protons to it, the electrostatic repulsion between them will make the nucleus more unstable, because the electrostatic force between them is more repulsive at a greater distance than the strong force is attractive  So how come if you add more neutrons, which don't have a charge and so there is no electrostatic force, the nucleus still becomes more unstable?  Also why aren't there groups of neutrons bound together, so purely neutron nuclei (because they are neutral, I'm guessing they couldn't form atoms, because of the electrons needed for an atom)
22331
Given that the sun’s temperature is lower than the temperature needed to fuse two protons. How does the sun provide enough energy for this fusion to happen?  Has it do something with tunneling and $E = mc^2$ ? I just can´t seem to understand the concept. If someone could simplify this for me, I would be grateful.   From this , it says " The fusing of two protons which is the first step of the proton-proton cycle created great problems for early theorists because they recognized that the interior temperature of the sun (some 14 million Kelvins) would not provide nearly enough energy to overcome the coulomb barrier of electric repulsion between two protons. With the development of quantum mechanics, it was realized that on this scale the protons must be considered to have wave properties and that there was the possibility of tunneling through the coulomb barrier.".   I was reading through this and my belief was that the sun actually provided a high enough temperature to fuel fusion, however after reading this I am quite confused.
21899
The question itself is pretty self explanatory. I asked this to my chemistry teacher when he was doing the photoelectric effect while teaching atomic structure, and he just shrugged it off.  One possible mechanism that I thought up, is an atom with a unpaired electron (say hydrogen) to absorb one photon, and jump to a higher energy level, and then just immediately be hit by another photon with a different energy which raises it to an even higher level. Then finally the electron falls back into its proper non exited state releasing not two but only one photon which has the energy of both the initial photons, ideally combining photons.  Is this mechanism correct? Does it occur in nature? Do photons have other ways in which they merge? or do they not merge at all?
57073
Electrons   have a much bigger charge density as the protons (and especially lead nuclei), aren't compound particles as the protons (and especially lead nuclei) are able to get a much bigger energy with the same fields as the protons (and especially the lead nuclei).   Why seems common for the big colliders after the LEP to use protons (and much bigger nuclei)?  Reacting comments: Yes, to get good experimental data about quark matter they need a lot of hot quarks (= collided big nuclei). But to create new particles, the energy per degree of freedom needs to be maximized, and this maximum is at the single particle with the highest charge density, and this is the electron.
2418
I am a bit confused regarding the nuclear fusion that occurs during star formation. For example, suppose there is a huge hydrogen cloud. It gets more mass and therefore pulls in more and more hydrogen, but it could just do this endlessly and get endlessly big. What causes it to stop growing? Is it because of the heat generated by the huge mass?
7239
I see that many websites and magazines with physics thematic are pretty excited about mining Helium 3 isotope on the Moon. But this seems to be a very hard-to-get resource. For more than one reason:  There is not too much of it on the moon.  0.007% of the moon soil. Transport to earth would be also very VERY complicated in my opinion.  to take care of the harvesters.  Deuterium can be found in the seas as &quot;heavy water&quot;. No spaceships needed. Now even when we get the Helium-3, I have a strong suspicion that it contains less energy than Deuterium but it will require more energy to start the fusion. Why I think it needs more initial energy to start the fusion?  Deuterium contains one proton and one neutron. That makes a +1e core. Helium 3 has 2 protons and one neutron - That's +2 core.  Now the worst problem with fusion reaction is, that once you pull the atoms so close, that the  no longer shield the polarity of the protons they start repelling with electric force. Now if you're trying to pull +1 and +1 together it seems much easier than pulling +2 and +2 together. Just think about the standard equation: $F_e = k*\frac{|Q_1*Q_2|}{r^2}$ where $k$ is the permittivity constant and $Q_{1,2}$ are the proton charges. Repelling force must be 4 times as large.  Why I think it contains less energy? This is even simpler to explain. In the fusion process we merge smaller cores to create larger. We normally start with hydrogen and create helium. Now when we already have Helium fused, it means that we missed one step in the fusion. Why would we do that? Can't actually Helium 3 core be one of cores that are created in Hydrogen fusion?
33265
I wanted to know that if FIRE is Matter or Energy. I know that both are inter-convertible. but that doesn't mean there is interconversion taking place just like nuclear fusion or fission. If it is matter, then its has to occupy space and have mass. I really doubt that fire has mass. If it is energy, then i don't get it. Please enlighten me from my ignorance.