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In
modern physics, material in the universe is made up of quanta or “particles”
such as electrons, protons and neutrons. These units can be said to relate
through various forces or fields (strong, weak, electromagnetic, gravitational)
for which there are matching “field quanta” such as photons and gluons. These
quanta are usually understood as the particles that make up these fields, and
while things are a bit more complex it is the right basic concept. We have a
lot of experimental proof for these quanta, but there is one that’s often
stated for which we have no experimental proofs, that’s the graviton.

One
of the fundamental methods in quantum field theory is to begin with a wave form
and then “quantize” it by the help of mathematical formalism. In this way you
can display, for example, how photons ascend from the electromagnetic field.
The same method can be applied with the gravitational field. Begin with
gravitational waves, and then quantize it to derive gravitons. But there are
some glitches with this methodology. In quantum field theory all fields act
inside a flat background of space and time (named Minkowski space).
Gravitational waves interfere with space and time itself, so to derive
gravitons it’s often supposed that the gravitational waves are a variation
inside a background of Minkowski space. It this way you can take gravity as a
field within flat space so that you can quantize it.

Of
course, general relativity illustrates that is not how gravity works. Gravity
is a result of space time curvature, so to quantize gravity you would have to
quantize space time itself. Just how that might be done is one of the great
unexplained mysteries in physics. So it’s probable that gravitons don’t exist.
But it’s usually considered that they do, since most physicists ponder that in
the end quantum theory will be at the heart of everything. The present key
approaches to quantum gravity, such as string theory and loop quantum gravity,
forecast the reality of gravitons with the similar characteristics we see in
the simple “quantized wave” method.

Even
if gravitons are there, it’s probable that we would never be able to perceive
them. As one latest paper demonstrated, gravitons would interact so weakly with
masses that you would require something like a Jupiter-mass detector circling a
neutron star. Even then it would take more than a decade to perceive a single
graviton. Even then the noise from particles like neutrinos would wash out your
signal. If there’s no applied way to sense gravitons, does it make any logic to
talk of them as a scientific model?

Perhaps,
assuming they continue inside a robust model of quantum gravity, there may be
secondary ways of proving their actuality. For now, though, they are totally
hypothetical.

This post was written by Usman Abrar. To contact the
writer write to iamusamn93@gmail.com.
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https://www.academia.edu/4168202/Theory_of_Everything_-_4_Dimensional_String_Theory

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