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fxdung
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In Condensed Matter Physics there are "giant" molecules that are macro bodies(e.g crystals).But why in Nuclear Physics we can not produce a "giant" nucleus?
They exist and are called neutron stars.fxdung said:In Condensed Matter Physics there are "giant" molecules that are macro bodies(e.g crystals).But why in Nuclear Physics we can not produce a "giant" nucleus?
hilbert2 said:There needs to be a binding force that cancels the Coulomb repulsion between protons. In small nuclei it is the strong nuclear force and in neutron stars it's gravitation.
fxdung said:Why there are not too many neutrons in small nuclei?
PeterDonis said:Neutron stars have no protons so there is no Coulomb repulsion to cancel. However, Coulomb repulsion is not the only effect involved. There is also degeneracy pressure, which is what balances gravity in a neutron star.
The Coulomb force only acts between two charged particles.hilbert2 said:But isn't the coulomb force the first thing that has to be overcome when squeezing ordinary matter to neutron matter?
That was already answered: The range of the strong nuclear force is short and Coulomb repulsion (Which has infinite range) is strong.fxdung said:The vinicity neutrons have strong force,why is there a limit to how large nucleus can be(despite of short range force)?
This is not sufficient to answer the query. It only explains why nuclei with many protons cannot exist. But why adding many neutrons to a stable nucleus makes it unstable needs an additional explanation - beta decay. Wikipedia has a good synopsis.Dale said:That was already answered: The range of the strong nuclear force is short and Coulomb repulsion (Which has infinite range) is strong.
That is true, both the strong force and the weak force are important.A. Neumaier said:But why adding many neutrons to a stable nucleus makes it unstable needs an additional explanation - beta decay.
A nucleus with p protons and n neutrons will beta decay if and only if the binding energy of a nucleus with p+1 protons and n-1 neutrons is smaller by more than the mass of an electron.fxdung said:What is the condition for beta decay easily happens?
...because gravitation changes the binding energy balance. (For terrestrial nuclei gravitation is negligible.)fxdung said:And with neutron star this condition does not happen,does it?
There is alpha decay where two neutrons and two protons detach. There can also be neutrons emitted. All that matters is that the sum of the masses of the products be less than the original nucleusfxdung said:why is there not the process that neutrons detach the nuclei, but it must there be beta decay?
fxdung said:In Condensed Matter Physics there are "giant" molecules that are macro bodies(e.g crystals).But why in Nuclear Physics we can not produce a "giant" nucleus?
That is a defensible claim! Although I usually think they look more like pasta or butter, but something food-like.ZapperZ said:You might as well claim that a cow looks like a Frank Gehry building.
hilbert2 said:Even a hypothetical piece of matter composed of only protons would probably keep at constant volume if compressed below its Schwarzschild radius.
fxdung said:What is the degeneracy pressure?
PeterDonis said:No, it would collapse. A static object made of ordinary matter can't remain static at a radius below 9/8 of the Schwarzschild radius for its mass.
Neutron stars have protons - just not as many as neutrons. The interior has many neutrons and a few protons and electrons. The outer parts have nuclei and even regular atoms.PeterDonis said:Neutron stars have no protons so there is no Coulomb repulsion to cancel. However, Coulomb repulsion is not the only effect involved. There is also degeneracy pressure, which is what balances gravity in a neutron star.
mfb said:Neutron stars have protons
mfb said:The outer parts have nuclei and even regular atoms.
The ##O(r^{-6})## part of the van der Waals potential is the attractive portion of it (induced dipole-induced dipole). The repulsive portion is far more complicated, but an exponential works pretty well as an approximation.A. Neumaier said:It is the van der Waals force between neutral matter. This is still more long range (namely ##O(r^{-6})##) than the exponentially decaying strong force.
The repulsive force between neutral atoms is the exchange force due to the Pauli principle. It grows for ##r\to 0## only like ##r^{-1}##. An exponential is a traditional but incorrect approximation.TeethWhitener said:The ##O(r^{-6})## part of the van der Waals potential is the attractive portion of it (induced dipole-induced dipole). The repulsive portion is far more complicated, but an exponential works pretty well as an approximation.
Actually, when gravity is holding them together instead of strong nuclear force (I’m talking about neutron stars) that’s the condition of having a giant atom... because gravity decays much slower than nuclear forces over distances. However, try not to make it too big because it will collapse and becomes a black hole.fxdung said:But why in the Earth we only see a finite number of neutrons in atoms?What is the condition to exist a "giant" atom?
Producing a "giant" nucleus is difficult because it requires a tremendous amount of energy and precision. The nucleus of an atom is made up of protons and neutrons, and adding more of these particles to the nucleus requires a significant amount of energy. Additionally, the particles must be added in a very specific and controlled manner to create a stable and functional nucleus.
While scientists have been able to artificially create nuclei with a higher number of protons and neutrons than naturally occurring elements, these nuclei are still far from being considered "giant." The current technology and understanding of nuclear physics make it extremely challenging to artificially produce a "giant" nucleus in a laboratory setting.
The size of a nucleus that we can produce is limited by the stability of the nucleus. As more particles are added, the nucleus becomes increasingly unstable and prone to decay. This limit is known as the "island of stability," and scientists are still working to understand and potentially reach this limit.
While there are currently no known practical applications for "giant" nuclei, their study can provide valuable insights into the fundamental properties of matter and the forces that govern the universe. It can also potentially lead to new discoveries and technologies in the future.
The term "giant" is used to describe these nuclei because they would be significantly larger than any naturally occurring nuclei. It is a theoretical concept that helps scientists understand the potential limits and possibilities of nuclear physics. While we cannot currently produce them, the pursuit of "giant" nuclei drives scientific research and advancements in the field of nuclear physics.