- 3956 - DARK MATTER - to explain the Universe? Einstein was right about invisible dark matter, a massive new map of the universe suggests. Light produced just 380,000 years after the Big Bang was warped by the universe's dark matter exactly the way Einstein predicted it would be.
------------ 3956 - DARK MATTER - to explain the Universe?
- Astronomers
have made the most detailed map ever of mysterious dark matter using the
universe’s very first light, and the "groundbreaking" image has
possibly proved Einstein right yet again.
The new image, made using 14 billion-year-old light from the turbulent
aftermath of the Big Bang, shows the enormous matter tendrils that formed not
long after the universe exploded into being.
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- It turns
out the shapes of these tendrils are remarkably similar to those predicted
using Einstein's theory of general relativity.
The new result contradicts previous dark matter maps that suggested the
cosmic web. the gigantic network of crisscrossing celestial superhighways paved
with hydrogen gas and dark matter that spans the universe, is less clumpy than
Einstein's theory predicted.
-
- This new
result shows that both the 'lumpiness' of the universe, and the rate at which
it is growing after 14 billion years of evolution, are just what you'd expect
from our standard model of cosmology based on Einstein's theory of gravity.
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- Scientists
think that the universe that formed after the Big Bang teemed with matter as
well as antimatter particles, which are identical to their matter counterparts
but with opposite electrical charges.
-
- Because
matter and antimatter annihilate each other when they collide, if both were
made in equal measure, all of the universe's matter should have been
annihilated. However, the rapidly expanding fabric of space-time, along with
some helpful quantum fluctuations, kept pockets of the universe's primordial
plasma intact.
-
- Then,
according to the rules set out by Einstein's theory of relativity, gravity
compressed and heated these plasma pockets so that sound waves, called baryon
acoustic oscillations, rippled outward from the clumps at half the speed of
light. These gigantic waves pushed out matter that hadn't already been sucked
in on itself, creating the infant cosmic web: a series of thin films
surrounding countless cosmic voids, like a nest of soap bubbles in a sink.
-
- Once this
matter cooled, it coalesced into the first stars, which pooled into matter-rich
galaxies at the meeting points of the web's tangled strands. But in the past, astronomers studying the
cosmic web found what seemed to be a massive discrepancy, the matter was
significantly more evenly distributed and less lumpy than expected. It was an
ominous sign that existing cosmological models were missing important physics.
-
- The Atacama Cosmology Telescope (ACT) in Chile,
which scanned a quarter of the entire night sky from 2007 to 2022. Using its
incredibly sensitive microwave detector, the telescope picked up light from the
cosmic microwave background radiation (CMB), the universe's very first light
made just 380,000 years after the Big Bang, and used a process called
gravitational lensing to map the concentrations of matter in the CMB.
-
-
Gravitational lensing is a phenomenon in which light moving through a
region of space-time warped by powerful gravitational fields travels, in a
curve, warping and twisting through a gigantic funhouse mirror until it emerges
as a stretched-out arc called an Einstein ring.
-
-
Gravitational lensing can detect dark matter, which makes up 85% of the
universe's matter but cannot be directly observed. The new map contradicted previous ones made
with visible light from galaxies, and showed that Einstein's original theory was
far more accurate than first thought.
-
- Astronomers
estimate that roughly 85% of all the matter in the universe is dark matter,
meaning only 15% of all matter is normal matter. Accounting for dark energy,
the name astronomers give to the accelerated expansion of the universe, dark
matter makes up roughly 27% of all the mass energy in the cosmos.
-
- Astronomers
have a variety of tools to measure the total amount of matter in the universe
and compare that to the amount of "normal" (also called "baryonic")
matter. The simplest technique is to compare two measurements.
-
- The first
measurement is the total amount of light emitted by a large structure, like a
galaxy, which astronomers can use to infer that object's mass.
-
- The second
measurement is the estimated amount of gravity needed to hold the large
structure together.
-
- When
astronomers compare these measurements on galaxies and clusters throughout the
universe, they get the same result: There simply isn't enough normal, light-emitting
matter to account for the amount of gravitational force needed to hold those
objects together.
-
- Thus, there
must be some form of matter that is not emitting light: dark matter.
-
- Different
galaxies have different proportions of dark matter to normal matter. Some
galaxies contain almost no dark matter, while others are nearly devoid of
normal matter. But measurement after measurement gives the same average result:
Roughly 85% of the matter in the universe does not emit or interact with light.
-
- There are
many other ways astronomers can validate this result. For example, a massive
object, like a galaxy cluster, will warp space-time around it so much that it
will bend the path of any light passing through an effect called gravitational
lensing. Astronomers can then compare the amount of mass that we see from
light-emitting objects to the mass needed to account for the lensing, again
proving that extra mass must be lurking somewhere.
-
- Astronomers
can also use computer simulations to look at the growth of large structures.
Billions of years ago, our universe was much smaller than it is today. It took
time for stars and galaxies to evolve, and if the universe had to rely on only
normal, visible matter, then we would not see any galaxies today. Instead, the
growth of galaxies required dark matter "pools" for the normal matter
to collect in.
-
- Cosmologists
can look back to when the cosmos was only a dozen minutes old, when the first
protons and neutrons formed. Cosmologists can use our understanding of nuclear
physics to estimate how much hydrogen and helium were produced in that epoch.
-
- These
calculations accurately predict the ratio of hydrogen to helium in the
present-day universe. They also predict an absolute limit to the amount of
baryonic matter in the cosmos, and those numbers agree with observations of
present-day galaxies and clusters.
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-
Alternatively, dark matter may be a misunderstanding of our theories of
gravity, which are based on Newton's laws and Einstein's general
relativity. Astronomers can tweak those
theories to provide explanations of dark matter in individual contexts, like
the motions of stars within galaxies. But alternatives to gravity have not been
able to explain all the observations of dark matter throughout the universe.
-
- All the
evidence indicates that dark matter is some unknown kind of particle. It does
not interact with light or with normal matter and makes itself known only
through gravity.
-
- In fact,
astronomers think there are trillions upon trillions of dark matter particles
streaming through you right now. Scientists
hope to nail down the identity of this mysterious component of the
universe soon.
-
April 12, 2023 DARK MATTER
- to explain the Universe? 3956
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--- Thursday, April 13, 2023 ---------------------------
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