- 4508
- GRAVITY - can
it exist without mass? If gravity can
exist without mass, that could explain Dark Matter. Dark Matter is Nature’s poltergeist. We can
see its effects, but we can’t see it, and we don’t know what it is. It’s as if
Nature is playing tricks on us, hiding most of its mass and confounding our
efforts to determine what it is.
-
------------------------------------ 4508
- GRAVITY - can
it exist without mass?
-
- It’s all part of the Universe’s “missing
mass” problem. Actually, it’s our problem. The Universe is what it is. It’s our
understanding of the Universe, mass, and gravity that’s the problem. And a
solution is proving to be elusive.
-
- Whatever the missing mass is or whatever
causes the effects we observe, we have a placeholder name for it: “dark
matter”. And it makes up 85% of the matter in the Universe.
-
- Could dark matter be primordial black holes?
Could it be axions? How about WIMPS? Are dark photons its force carrier?
There’s lots of theoretical thought but no conclusion.
-
- Our hunt for dark matter may be off-track.
Instead of looking for a type of particle, the solution might lie in a type of
topological defect found throughout the Universe that has its roots in the
Universe’s early stages.
-
- Dark matter has a binding effect on
structures like galaxies. Astronomers know that galaxies don’t have enough
measurable mass to hold themselves together. By measuring the mass of the stars
and gas in galaxies, it became clear that the visible components of the
galaxies don’t provide enough mass to hold themselves together. They should
simply dissipate into their constituent stars and clouds of gas.
-
- But galaxies don’t dissipate, and scientists
have concluded that something is missing. Another solution to the gravitational
field equations of general relativity, the simplified version of which,
applicable to the conditions of galaxies and clusters of galaxies, is known as
the “Poisson equation”, which gives a
finite gravitation force in the absence of any detectable mass.
-
- The nature of dark matter (DM), defined as
an unknown component of the cosmic substratum responsible for the extra
gravitational field that binds galaxies and clusters of galaxies, has been an
enigma for more than a century.
-
- Phase transitions in the Universe are
episodes when the state of matter in the Universe changes. Not locally but
across the entire cosmos. One example is when the Universe cooled enough to
allow the strong force to bind quarks into protons and neutrons.
-
- The topological defects could have formed
during one of these phase transitions. These defects can take the shape of
shell-like compact regions where matter density is much higher. When arranged
in concentric rings, these defects behave like gravity but don’t have mass.
-
- Topological effects are very compact
regions of space with a very high density of matter, usually in the form of
linear structures known as “cosmic strings”, although 2-D structures such as
spherical shells are also possible. The shells consist of a thin inner layer of
positive mass and a thin outer layer of negative mass; the total mass of both
layers, which is all one could measure, mass-wise, is exactly zero, but when a
star lies on this shell it experiences a large gravitational force pulling it
towards the center of the shell.
-
- So, despite our inability to measure the
mass, it’s there, and other objects respond to it. Mass warps space-time and
affects even massless photons. That fact underlies our ability to use
gravitational lensing. We use the mass of galaxy clusters in gravitational
lensing. A set of spherical shells could cause the same effect.
-
- Gravitational bending of light by a set of
concentric singular shells comprising a galaxy or cluster is due to a ray of
light being deflected slightly inwards, towards the center of the large-scale
structure, or the set of shells as it passes through one shell. The sum total effect of passage through
many shells is a finite and measurable total deflection which mimics the
presence of a large amount of dark matter in much the same way as the velocity
of stellar orbits.
-
- Since astronomers measure galaxy and galaxy
cluster masses by measuring the light they deflect and the way they affect the
orbit of stars, astronomers could be measuring topological defects rather than
particles that comprise dark matter.
-
- Both the deflection of light and stellar
orbital velocities is the only means by which one gauges the strength of the
gravitational field in a large-scale structure. In 2022, researchers discovered a giant arc
in the sky. It spans 1 Gigaparsec and is nearly symmetrical. It’s one of
several large-scale structures that seems to go against the Standard Model and
the Cosmological Principle it’s based on.
-
- The observation of giant arcs and rings
could lend further support to the proposed alternative to the DM model. If these shells exist, their alignment would
also govern the formation and shape of galaxies and clusters. Future research
will determine exactly how these shells form.
-
- A contentious point is whether the shells
were initially planes or even straight strings, but angular momentum winds them
up. There is also the question of how to confirm or refute the proposed shells
by dedicated observations.
-
- Of course, the availability of a second
solution, even if it is highly suggestive, is not by itself sufficient to
discredit the dark matter hypothesis.
It could be an interesting mathematical exercise at best. But it is the first proof that gravity can
exist without mass.
-
-
June 23, 2024 GRAVITY
- can it exist without mass? 4508
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--------------------- --- Sunday, June 23, 2024
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