Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 05/11/2015 21:50:02
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Ian Scott asked the Naked Scientists:
Hi Chris and team
I am wondering why we consider that energy is derived from changes in small mass changes dm as in nuclear reactors (E = dm x c^2) but is it correct that matter and anti matter collisions release all their "mass energy" when they collide due to having opposite electric charge. If so, why isn't electric charge postulated as the source of energy, leaving mass as some accidental by-product.
It is perfectly possible for incomplete or incorrect theories to predict outcomes that corroborate experiment. For example, time dilation with gravitational gradients on earth has been measured using laser interferometry. However true this appears, it doesn't support energy from mass as Einstein claimed nor deter suggestions that energy could actually be an electrical effect. Or is there a third explanation? Or are both mass and charge instigated in energy release? Great program though Chris and team and I am sure of a fascinating reply.
What do you think?
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is it correct that matter and anti matter collisions release all their "mass energy" when they collide?
Yes, all the energy of the particle+antiparticle gets converted from one form (mostly mass) into another form (eg gamma rays).
is it correct that matter and anti matter collisions release all their "mass energy" when they collide due to having opposite electric charge?
No, the electric charge is not the primary source of the energy.
This is illustrated by the collision of neutral particles & their anti-particles (eg neutron+anti-neutron), where all the energy of the particle+antiparticle gets converted from one form (mostly mass) into another form (eg gamma rays).
If so, why isn't electric charge postulated as the source of energy, leaving mass as some accidental by-product.
With charged particles, the electrical potential energy is certainly a component of the initial energy, but usually a small contributor.
Another contributor is the kinetic energy of the particles; but unless the particles come out of a particle accelerator, this is a fairly small contribution.
Another contribution is gravitational potential energy between the particles, but this is negligible compared to any electrical potential energy.
time dilation with gravitational gradients on earth has been measured using laser interferometry. However true this appears, it doesn't support energy from mass as Einstein claimed
This is not an experiment that I would expect to convert measurable amounts of energy from one form to another.
However, take two orbiting neutron stars, and this has been shown to illustrate radiation of gravitational waves and time dilation. The same effect occurs for photons passing through Earth's gravitational field, but the effect is far too small to measure.
it doesn't ... deter suggestions that energy could actually be an electrical effect.
Transformation of Energy is one effect of electrical interactions. Take an electron and a proton - their opposite electric charges attract, and the interaction releases one or a couple of photons totalling 13 eV (electron-volts, a unit of energy).
However, the mutual annihilation of an electron and a positron releases around 1,022,000 eV.
The mutual annihilation of a proton and an antiproton releases around 1,876,000,000 eV.
The contribution of the electric field to the total released energy is miniscule.
The energy involved in nuclear interactions is really huge - far more than other types of interactions that play with electric charges, like electricity supply, chemistry, biology, geology and optics.
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Evan
"However, the mutual annihilation of an electron and a positron releases around 1,022,000 eV.
The mutual annihilation of a proton and an antiproton releases around 1,876,000,000 eV."
What is the figure for neutron and antineutron annihilation please?
I note that no mention is made of the collapsing of the magnetic force of repulsion that pushes the charges apart inside an isotope. As the gamma rays given off are electromagnetic then surely it is the the annihilation of that magnetic energy that is releasing in the form of nuclear energy.
In other words mass is made of magnetic energy and E=mc^2 is then easy to understand
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What is the (energy) for neutron and antineutron annihilation please?
You can find this easily, by looking in Wikipedia for a Neutron (http://en.wikipedia.org/wiki/Neutron).
On the right-hand side, there is a list of characteristics of fundamental particles.
Under Mass, find the line that states 939.5654133(58) MeV/c2. This is the energy-equivalent of a neutron.
The energy-equivalent of an antineutron is identical to a neutron.
So the energy released by the mutual annihilation of these uncharged particles is 2x939.5 = 1878 MeV, or slightly more than a reaction between the charged proton & antiproton.
Not that antineutrons are easy to generate, or that it is easy to collide an antineutron and a neutron...
the magnetic force of repulsion that pushes the charges apart inside an isotope
I would have said that most of the repulsion between protons is Electric Force (but it is related to Magnetism).
And the attraction between protons & neutrons is from the Strong Nuclear Force, which overrides the electric force (at least in stable atoms).
As the gamma rays given off are electromagnetic then surely it is the annihilation of that magnetic energy that is releasing in the form of nuclear energy
Gamma rays are high-frequency nuclear radiation which is given off by nuclear isomers (http://en.wikipedia.org/wiki/Nuclear_isomer)when the nucleons change orbitals (just like visible light is given off when electrons change orbitals). This is done without changing the nature of the nucleus, ie it remains the same isotope of the same element.
Gamma Rays from nuclear isomers have typical energies around 1-2 MeV, and they have not been observed above 10MeV.
The energies of gamma rays or nuclear reactions are relatively small compared to the energy released by antiparticle collisions.
The classic nuclear reaction that people would like to harness is 4 Hydrogen atoms→ 1 Helium atom.
The atomic mass of a Hydrogen atom is: 1.008, and for Helium is: 4.002602 (1 amu=931.3 MeV)
4x1.008 - 4.0026 = 0.0294 = 27.4 MeV, the "missing mass"
This reaction releases about 27MeV of energy, but the majority of the mass-energy (3,728 MeV=99.3%) remains in the Helium atom. However, all of this energy is released in antiparticle annihilations.
The energy involved in nuclear interactions is really huge
I should have added: But the energy involved in matter/antimatter annihilation is far greater!
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I had always considered that the nuclear energy had come from the loss of neutron mass as this would not effect the balancing of electric charges. However, to inflate the universe after the big bang, we need to split space into positive and negative charged volumes and thus create something. But surely if we collapse identical amounts of that negative and positive matter and anti-matter back together again we will only have the temperature and spin energies as the e/m charge/matter components will annihilate?