- 4373 - DARK MATTER - and gravity mystery? - What is it about galaxies and dark matter? Most, if not all galaxies are surrounded by halos of this mysterious, unknown, but ubiquitous material. And, it played a role in galaxy formation. The nature of that role is something astronomers are still figuring out.
------------------ 4373 - DARK MATTER - and gravity mystery?
-
- Today, they’re
searching the infant Universe, looking for the tiniest, brightest galaxies.
That’s because they could help tell the tale of dark matter’s role in galactic
creation.
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- Simulations of
early galaxy formation with computer programs track the circumstances of
galactic births not long after the Big Bang. These programs take into account
previously neglected interactions between dark matter and the primordial
“stuff” of the Universe, hydrogen and helium gas.
-
- How would
interactions between ordinary “baryonic matter” and dark matter make a
difference? In the early Universe,
clouds of gas moved at supersonic speeds past clumps of dark matter. It bounced
off the dark matter. Eventually, after millions of years, the gaseous material
fell back together to form stars in a blast of star birth. The simulations
track the formation of those galaxies right after the Big Bang.
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- The existence of
those smaller, brighter, more distant galaxies could confirm the so-called this
“cold dark matter” model. It suggests that the Universe was in a hot dense
state containing only gases after the Big Bang. Over time, it evolved to a
lumpy distribution of galaxies and eventually galaxy clusters.
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- Stars and galaxies
formed, but the earliest steps likely depend on gravitational interaction with
dark matter. JWST has seen some early
galaxies during its time in operation.
The images it provided are tantalizing hints at what might exist in
earlier epochs and could provide insight into the role of dark matter.
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- The discovery of
patches of small, bright galaxies in the early universe would confirm that we
are on the right track with the cold dark matter model because only the
velocity between two kinds of matter can produce this type of galaxy.
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- JWST began to
look for galaxies that are much brighter than expected. If they exist, that
will likely prove the interactions occurred early in cosmic time. If none can
be found, then maybe scientists still might not understand dark matter
interactions. The big question to answer is, if they exist, then how did they
form so quickly and why are they so bright?
-
- The standard
cosmological model says that the gravitational pull of clumps of dark matter in
the early Universe attracted ordinary matter. Eventually, that caused stars to
form, followed by galaxies. Dark matter is thought to move more slowly than
light. So, astronomers predicted that the star- and galaxy-formation processes
happened very gradually.
-
- What if something
else was going on more than 13 billion years ago? How would that change things?
It was a time before the first galaxies formed. But, it was a time when
ordinary matter in the form of large over densities of hydrogen and helium gas
streamed through the expanding Universe.
-
- It bounced off
slower-moving clumps of dark matter and outran its gravitational pull, at least
for a time. Then, the baryonic matter massed together again, under the
influence of dark matter. That’s when the star birth fireworks began.
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- While the
streaming suppressed star formation in the smallest galaxies, it also boosted
star formation in dwarf galaxies, causing them to outshine the non-streaming
patches of the universe. The accumulated
gas began to fall together after millions of years. That led to a huge burst of
star formation.
-
- Lots of massive
hot, young stars began to shine, out-brilliancing the stars in other small
galaxies. Ultimately what this means is that since dark matter is impossible to
“see”, those brightly shining patches of galaxies could be indirect evidence of
its existence. And, they’d prove the role dark matter played in the creation of
galaxies.
-
- JWST is a perfect
telescope to help see these galaxies. It should be able to peer into regions of
the Universe where tiny infant galaxies are brighter than astronomers expect
them to be. That extreme luminosity will help JWST spot them, showing them as
they looked at a time when the Universe was only a few hundred million years
old.
-
- Because dark
matter is impossible to study directly, searching for those bright patches of
baby galaxies in the early Universe could offer an effective test for theories
about dark matter and its role in shaping the first galaxies.
-
- There are still
more mysteries after we solve dark matter.
What happens inside black holes? How did the Big Bang begin? How do all
forces unite to form the cosmos?
-
- Scientists have
finally cracked how to measure gravity in the quantum world. Using a new
technique they detected weak gravitational pull on a tiny particle. So tiny, in
fact, that it is the smallest mass at which gravitational signals have ever
been recorded.
-
- The technique
involved levitating the particle, weighing just 0.43mg, in extremely cold
temperatures (-273°C). Using levitating
magnets and superconducting devices, they then isolated the vibration of the
particle.
-
- This helped them
measure a weak pull – coming in at just “30 aN”. One attoNewton (aN) is one
quintillionth (1/1,000,000,000,000,000,000) of a Newton (N). The gravitational
force of an apple sitting on a table is roughly 1N, making the pull that the
scientists measured even smaller than the pull of a single bacteria on a
table’s surface.
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- Until now,
scientists have not understood how gravity works at the microscopic level. But
particles and forces at this scale interact differently from regular-sized
objects. Even Einstein was baffled by this: in his theory of General
Relativity, he said that there was no realistic experiment which could reveal
gravity in the quantum world.
-
- Scientists have
tried and failed to understand how gravity and quantum mechanics work
together. Until now. The discovery
makes scientists closer than ever to figuring out how forces at this scale work
and making a so-called 'theory of everything' possible.
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- In the future,
researchers can continue scaling the method down to measure even smaller
particles – bringing science even closer to unravelling the mysterious forces
that govern the Universe. Unravelling
these mysteries will help us unlock more secrets about the universe's very
fabric, from the tiniest particles to the grandest cosmic structures.
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-
February 29, 2024
DARK MATTER - and
gravity mystery? 4373
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