Four Forces vs. Fifth Force: Physicist's Insight

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In summary, the physicist says that there are only four forces and that for the first time in his life, it struck him as incomplete. He is asking if the force which is causing the universe to expand and which is speeding up, not at least a candidate for a fifth force, can be ruled out. He says that the force depends upon pressure and that with normal matter, which usually has negligible pressure compared to its mass energy, gravity behaves as we would naively expect. However, with radiation, if you have a box full of radiation, then that radiation will exert a pressure on the walls of the box equal to one third its energy density. He says that with dark energy, which has negative pressure, the opposite effect happens:
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Tanelorn said:
Chalnoth thanks for the Jeans length reference, I think this answers questions above that I have had for quite a while. Although, what is the estimated value, it seems like it isn't that large? Wouldnt this be relevant for star formation?
The length depends upon the density. So it is relevant for the formation of objects of all scales, whether asteroids, planets, stars, galaxies, or galaxy clusters. It's just that in an expanding universe, the average density is decreasing, and since it takes larger regions longer to collapse, there is a point where regions don't have enough time to collapse before the expansion lowers the density so far that they can longer collapse (because the Jeans' Length is smaller than the size of the overdensity).
 
<h2> What are the four fundamental forces in physics?</h2><p>The four fundamental forces in physics are gravity, electromagnetism, strong nuclear force, and weak nuclear force. These forces govern the interactions between particles and objects in the universe.</p><h2> What is the difference between the four forces and a fifth force?</h2><p>The four fundamental forces have been extensively studied and are well understood by physicists. A fifth force, if it exists, would be a new fundamental force that is not yet fully understood or incorporated into our current understanding of the universe.</p><h2> How do scientists search for evidence of a fifth force?</h2><p>Scientists search for evidence of a fifth force by conducting experiments and observations that could potentially reveal new interactions between particles. They also study the behavior of the four known forces at different scales and energies to look for discrepancies that could indicate the presence of a fifth force.</p><h2> What are some proposed theories about a fifth force?</h2><p>Some proposed theories about a fifth force include the existence of a new particle, such as a dark photon, that would mediate the force, or modifications to the laws of gravity at very small scales.</p><h2> What are the implications of a fifth force for our understanding of the universe?</h2><p>If a fifth force is discovered and confirmed, it would have significant implications for our understanding of the universe and could potentially lead to new discoveries and advancements in physics. It could also help explain phenomena that are currently unexplained by the four known forces.</p>

FAQ: Four Forces vs. Fifth Force: Physicist's Insight

What are the four fundamental forces in physics?

The four fundamental forces in physics are gravity, electromagnetism, strong nuclear force, and weak nuclear force. These forces govern the interactions between particles and objects in the universe.

What is the difference between the four forces and a fifth force?

The four fundamental forces have been extensively studied and are well understood by physicists. A fifth force, if it exists, would be a new fundamental force that is not yet fully understood or incorporated into our current understanding of the universe.

How do scientists search for evidence of a fifth force?

Scientists search for evidence of a fifth force by conducting experiments and observations that could potentially reveal new interactions between particles. They also study the behavior of the four known forces at different scales and energies to look for discrepancies that could indicate the presence of a fifth force.

What are some proposed theories about a fifth force?

Some proposed theories about a fifth force include the existence of a new particle, such as a dark photon, that would mediate the force, or modifications to the laws of gravity at very small scales.

What are the implications of a fifth force for our understanding of the universe?

If a fifth force is discovered and confirmed, it would have significant implications for our understanding of the universe and could potentially lead to new discoveries and advancements in physics. It could also help explain phenomena that are currently unexplained by the four known forces.

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