Gravitational waves are ripples in the fabric of space. Waves that originated in the early universe could carry important information about the phenomena that occurred there.
An illustration showing neutron stars merging into a black
hole, as gravitational waves ripple outward (Image credit: L. Rezolla (AEI)
& M. Koppitz (AEI & Zuse-Institut Berlin)) |
Ripples in space-time known as gravitational waves could
help reveal the secrets at the dawn of time, just moments after the Big Bang,
new research suggests. And physicists say they can learn more about these
primeval gravitational waves using nuclear fusion reactors here on Earth.
In a new study, physicists used equations that govern how
electromagnetic waves move through plasma inside fusion reactors to create a
theoretical model for how gravitational waves and matter interact.
That, in turn, could reveal a better picture of the earliest
moments in time.
Moments after the Big Bang, the universe was permeated by a
soup of hot, ultradense primordial plasma that sent powerful gravitational
waves rippling out into the cosmos.
These ancient gravitational waves would have propagated
throughout the universe and should still be present today, so the mutual
influence that matter and gravitational waves had on each other in the
universe's infancy would leave observable traces in both. Working backward from
those observable traces could reveal a better picture of that early period.
"We can't see the early universe directly, but maybe we
can see it indirectly if we look at how gravitational waves from that time have
affected matter and radiation that we can observe today," said Deepen Garg,
a graduate student in the Princeton Program in Plasma Physics and lead author
of the study, in a statement.
An illustration showing waves of space-time rippling away
from two colliding neutron stars (Image credit: NASA) |
A matter of great gravity
According to Einstein's theory of general relativity,
massive bodies interact gravitationally by deforming space around them,
generating ripples in space-time called gravitational waves that travel at the
speed of light.
Until now, physicists have used detectors such as the Laser
Interferometer Gravitational Wave Observatory (LIGO) to hunt gravitational waves
born in the collisions of black holes. These cosmic cataclysms generate the
most powerful gravitational waves, and they travel from the collision region to
Earth in a vacuum, meaning that to describe them, physicists need only model
the physics of these ripples in empty space.
However, when the universe was in its infancy, huge amounts
of matter moved around, generating gravitational waves that had to propagate
through a primordial plasma, which would have interacted with the waves,
altering their shape and trajectory.
To calculate how this primordial plasma would have affected
these ancient gravitational waves, Garg and his supervisor Ilya Dodin carefully
analyzed the equations of Einstein's theory of relativity, which describes how
the geometry of space changes as matter moves through it. Under certain
simplifying assumptions about the physical properties of matter, they could
calculate how gravitational waves and matter affect each other.
The team based part of their equations on the propagation of
electromagnetic waves in plasma. This process not only occurs under the surface
of stars, but also in fusion reactors on Earth.
"We basically put plasma wave machinery to work on a
gravitational wave problem," Garg said.
Although scientists have taken an important step toward
computing the measurable effects that gravitational waves and primordial plasma
may have had on each other, they still have a lot of work to do. The scientists
still need to make more accurate and detailed calculations in order to get a
better picture of what these ancient gravitational waves would look like today.
"We have some formulas now, but getting meaningful
results will take more work," concluded Garg.
The findings were published in The Journal of Cosmology andAstroparticle Physics.
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