When I was in school, I used to stay with one of
my classmates whose parents were cowherds. I used to bathe beside a water well
in their village home at 5 am under an open sky before we both cycled to school
at 7 am
There under an open sky in the early morning sky I
could see the Milky Way and countless stars twinkling up there. I wondered if
there was life out there among so many, many stars. It was then that I started
to have an early interest in astronomy.
I thought then all those stars were what heavens have.
Today, astronomers estimate there could be as much as 10 trillion, trillion (1
followed by 26 zeros) other stars or worlds up there. Is that all we could
visibly see even with our best ground-based and orbiting telescopes or even
theoretically estimate? All those visible stars, and galaxies are
made of protons, neutrons, and electrons bundled together into atoms.
I then wrote an article on particle physics two ago, followed by another article on quantum mechanics only last evening. In the article on particle physics, I briefly mentioned a Switzerland-based nuclear
research facility called European Organization for Nuclear Research (CERN)
where particle physics is carried out.
Today, I am going to write a little about dark matter
and dark energy in the universe, an area scientists have some idea what they might be.
One leading hypothesis is that dark matter consists of
exotic particles that don't interact with normal matter or light but that still
exert a gravitational pull. Several scientific groups, including one at CERN's
Large Hadron Collider, are currently working to generate dark matter particles
for study in the lab.
One of the most surprising discoveries of this century
is that this ordinary, or baryonic matter makes up less than 5 percent of the
mass of the universe.
The rest of the universe appears to be made of a
mysterious, invisible substance called dark matter (25 percent) and a force
that repels gravity known as dark energy (70 percent). This is what I shall be writing now.
Unlocking the Mystery:
Scientists have not yet observed dark matter directly.
It doesn't interact with baryonic matter and it's completely invisible to light
and other forms of electromagnetic radiation, making dark matter impossible to
detect with current instruments. But scientists are confident it exists because
of the gravitational effects it appears to have on galaxies and galaxy
clusters.
Dark matter and dark energy are two of the most
mysterious and fundamental components of our universe. They are both critical
to our understanding of cosmology, yet neither has been directly observed.
Let’s dive into what each of these is, their importance, potential
applications, and references for further reading.
What is Dark Matter?
Dark matter is a form of matter that does not emit,
absorb, or reflect light, making it invisible to electromagnetic observations.
It is called "dark" because it doesn't interact with electromagnetic
forces, meaning it doesn’t emit light, radio waves, or any other form of
radiation detectable by our current instruments. However, it exerts
gravitational effects on visible matter, such as stars and galaxies.
Evidence for dark matter comes from observation. The
first is shown by the galaxy rotation curves. By this we mean that the rotation
speed of galaxies cannot be explained solely by the visible matter they
contain. Stars at the outer edges of galaxies rotate faster than can be
accounted for by the gravitational pull of visible matter alone. This suggests
the presence of an unseen mass—dark matter.
The second evidence is gravitational lensing where
light from distant galaxies is bent more than it should be by the gravitational
fields of galaxy clusters. This bending suggests the presence of much more mass
than is visible, implying dark matter.
The third evidence we have come from the Cosmic
Microwave Background (CMB). The CMB, the afterglow of the Big Bang,
contains slight temperature fluctuations that reflect the distribution of
matter in the early universe. These fluctuations suggest that about 27% of the
universe's mass-energy content is dark matter.
But what is the importance of dark matter in
astronomy? Dark matter plays a critical role in the formation of cosmic
structures. Its gravitational influence is believed to have led to the
formation of galaxies, galaxy clusters, and large-scale structures in the
universe. In the field of cosmology, the presence of dark matter is essential
for the current standard model of cosmology, known as the Lambda-CDM model,
which explains the evolution of the universe from the Big Bang to its current
state.
Currently, dark matter has no direct application or
usefulness because it hasn’t been detected in a way that would allow us to
manipulate or harness it. However, understanding dark matter could
revolutionize physics by uncovering new particles or forces and leading to new
technologies.
What about Dark Energy? What is it?
Dark energy is a mysterious force that is driving the
accelerated expansion of the universe. Unlike dark matter, which clumps and
exerts gravitational attraction, dark energy appears to have a repulsive
effect, working against gravity to push galaxies apart.
What evidence do we have for dark energy? Observations
of distant supernovae in the late 1990s revealed that the universe's expansion
is accelerating, contrary to the expectation that gravity would slow it down.
This acceleration suggests the presence of dark energy.
Scientists now think that the accelerated expansion of
the universe is driven by a kind of repulsive force generated by quantum
fluctuations in otherwise "empty" space. What's more, the force seems
to be growing stronger as the universe expands. For lack of a better name,
scientists call this mysterious force dark energy.
Unlike for dark matter, scientists have no plausible
explanation for dark energy. According to one idea, dark energy is a fifth and
previously unknown type of fundamental force called quintessence, which fills
the universe like a fluid.
Many scientists have also pointed out that the known
properties of dark energy are consistent with a cosmological constant, a
mathematical Band-Aid that Albert Einstein added to his theory of general
relativity to make his equations fit with the notion of a static universe.
According to Einstein, the constant would be a repulsive force that counteracts
gravity, keeping the universe from collapsing in on itself. Einstein later
discarded the idea when astronomical observations revealed that the universe was
expanding, calling the cosmological constant his "biggest blunder."
Now that we see the expansion of the universe is
accelerating, adding in dark energy as a cosmological constant could neatly
explain how space-time is being stretched apart. But that explanation still
leaves scientists clueless as to why the strange force exists in the first
place.
The other evidence we have like dark matter also comes
from Cosmic Microwave Background (CMB). Detailed measurements of the CMB
suggest that dark energy makes up about 68% of the universe's total energy
density. The other evidence comes from the large-scale distribution and
clustering of galaxies on large scales which is consistent with the presence of
dark energy.
The importance of dark energy will enable us to
understand what will finally happen to our universe. Dark energy is crucial in
determining the ultimate fate of the universe. If dark energy continues to
dominate, the universe could keep expanding indefinitely, leading to scenarios
like the "Big Freeze" or "Heat Death."
Dark energy is often associated with the
cosmological constant (Λ), a term Einstein introduced in his equations of
General Relativity. Understanding dark energy could provide insights into the
fundamental nature of space-time.
As far as applications and usefulness to us is
concerned, I really cannot see any direct application of dark matter and dark
energy at the moment unless we are able to harness them for future energy
requirements when our Sun dies out in another 5 billion years. Our Sun is
already in its middle age. After the hydrogen runs out, there will be a period
of 2-3 billion years whereby the sun will go through the phases of
star death. By then probably mankind would have the technologies to harness the
dark energy which make up an impressive 70 % of all the energy in this
Universe. Understanding this could lead to profound changes in our
understanding of the universe and potentially new technologies.
Unfortunately, humanity may only last for another 2 or
3 centuries more, for reasons I have already written several articles about our
fate here in this blog post of mine
References for Further Reading
- Books:
- “The 4 Percent Universe: Dark Matter, Dark
Energy, and the Race to Discover the Rest of Reality” by Richard Panek.
- “Dark Matter and Dark Energy: The Hidden 95% of
the Universe” by Brian
Clegg.
- Scientific Papers and Articles:
- “A Brief History of Dark Matter” by J. W. Moffat, published in the European
Journal of Physics (2011).
- “Dark Energy and the Accelerating Universe” by S. Perlmutter, B. Schmidt, and A.
Riess, Nobel Lecture (2011).
- Websites:
The
visible universe—including Earth, the sun, other stars,
and galaxies—is made of protons, neutrons, and electrons bundled
together into atoms. Perhaps one of the most surprising discoveries of the 20th
century was that this ordinary, or baryonic, matter makes up less than 5
percent of the mass of the universe.
The
rest of the universe appears to be made of a mysterious, invisible substance
called dark matter (25 percent) and a force that repels gravity known as dark
energy (70 percent).
Unlocking
the Mystery
Scientists
have not yet observed dark matter directly. It doesn't interact with baryonic
matter and it's completely invisible to light and other forms of
electromagnetic radiation, making dark matter impossible to detect with current
instruments. But scientists are confident it exists because of the
gravitational effects it appears to have on galaxies and galaxy clusters.
For
instance, according to standard physics, stars at the edges of a spinning,
spiral galaxy should travel much slower than those near the galactic center,
where a galaxy's visible matter is concentrated. But observations show that
stars orbit at more or less the same speed regardless of where they are in the
galactic disk. This puzzling result makes sense if one assumes that the
boundary stars are feeling the gravitational effects of an unseen mass—dark matter—in a halo around the galaxy.
Dark
matter could also explain certain optical illusions that astronomers see in the
deep universe. For example, pictures of galaxies that include strange rings and
arcs of light could be explained if the light from even more distant galaxies
is being distorted and magnified by massive, invisible clouds of dark matter in
the foreground-a phenomenon known as gravitational lensing.
Scientists
have a few ideas for what dark matter might be. One leading hypothesis is that
dark matter consists of exotic particles that don't interact with normal matter
or light but that still exert a gravitational pull. Several scientific groups,
including one at CERN's Large Hadron Collider, are currently working to
generate dark matter particles for study in the lab.
Other
scientists think the effects of dark matter could be explained by fundamentally
modifying our theories of gravity. According to such ideas, there are multiple
forms of gravity, and the large-scale gravity governing galaxies differs from
the gravity to which we are accustomed.
Expanding
Universe
Dark
energy is even more mysterious, and its discovery in the 1990s was a complete
shock to scientists. Previously, physicists had assumed that the attractive
force of gravity would slow down the expansion of the universe over time. But
when two
independent
teams tried to measure the rate of deceleration, they found that the expansion
was actually speeding up. One scientist likened the finding to throwing a set
of keys up in the air expecting them to fall back down-only to see them fly
straight up toward the ceiling.
Scientists
now think that the accelerated expansion of the universe is driven by a kind of
repulsive force generated by quantum fluctuations in otherwise
"empty" space. What's more, the force seems to be growing stronger as
the universe expands. For lack of a better name, scientists call this
mysterious force dark energy.
Unlike
for dark matter, scientists have no plausible explanation for dark energy.
According to one idea, dark energy is a fifth and previously unknown type of
fundamental force called quintessence, which fills the universe like a fluid.
Many
scientists have also pointed out that the known properties of dark energy are
consistent with a cosmological constant, a mathematical Band-Aid that Albert
Einstein added to his theory of general relativity to make his equations fit
with the notion of a static universe. According to Einstein, the constant would
be a repulsive force that counteracts gravity, keeping the universe from
collapsing in on itself. Einstein later discarded the idea when astronomical
observations revealed that the universe was expanding, calling the cosmological
constant his "biggest blunder."
Now that we see the expansion of the universe is
accelerating, adding in dark energy as a cosmological constant could neatly
explain how space-time is being stretched apart. But that explanation still
leaves scientists clueless as to why the strange force exists in the first
place
From
Chat GPT
We
were talking about particle physics yesterday. We also talked about
Switzerland-based nuclear research facility have some social media users on
edge. In their view is CERN, also known as the European Organization for
Nuclear Research.
CERN
The
visible universe—including Earth, the sun, other stars,
and galaxies—is made of protons, neutrons, and electrons bundled
together into atoms. Perhaps one of the most surprising discoveries of the 20th
century was that this ordinary, or baryonic, matter makes up less than 5
percent of the mass of the universe.
The
rest of the universe appears to be made of a mysterious, invisible substance
called dark matter (25 percent) and a force that repels gravity known as dark
energy (70 percent).
Unlocking
the Mystery
Scientists
have not yet observed dark matter directly. It doesn't interact with baryonic
matter and it's completely invisible to light and other forms of
electromagnetic radiation, making dark matter impossible to detect with current
instruments. But scientists are confident it exists because of the
gravitational effects it appears to have on galaxies and galaxy clusters.
Dark
matter and dark energy are two of the most mysterious and fundamental
components of our universe. They are both critical to our understanding of
cosmology, yet neither has been directly observed. Let’s dive into what each of
these is, their importance, potential applications, and references for further
reading.
Dark
Matter
What
is Dark Matter?
Dark
matter is a form of matter that does not emit, absorb, or reflect light, making
it invisible to electromagnetic observations. It is called "dark"
because it doesn't interact with electromagnetic forces, meaning it doesn’t
emit light, radio waves, or any other form of radiation detectable by our
current instruments. However, it exerts gravitational effects on visible
matter, such as stars and galaxies.
Evidence
for Dark Matter:
- Galaxy Rotation Curves: The rotation speed of galaxies cannot be
explained solely by the visible matter they contain. Stars at the outer
edges of galaxies rotate faster than can be accounted for by the
gravitational pull of visible matter alone. This suggests the presence of
an unseen mass—dark matter.
- Gravitational Lensing: Light from distant galaxies is bent more than it
should be by the gravitational fields of galaxy clusters. This bending
suggests the presence of much more mass than is visible, implying dark
matter.
- Cosmic Microwave Background (CMB): The CMB, the afterglow of the Big Bang, contains
slight temperature fluctuations that reflect the distribution of matter in
the early universe. These fluctuations suggest that about 27% of the
universe's mass-energy content is dark matter.
Importance
of Dark Matter:
- Structure Formation: Dark matter plays a critical role in the
formation of cosmic structures. Its gravitational influence is believed to
have led to the formation of galaxies, galaxy clusters, and large-scale
structures in the universe.
- Cosmology: Dark matter is essential for the current
standard model of cosmology, known as the Lambda-CDM model, which explains
the evolution of the universe from the Big Bang to its current state.
Applications
and Usefulness:
Currently,
dark matter has no direct application because it hasn’t been detected in a way
that would allow us to manipulate or harness it. However, understanding dark
matter could revolutionize physics by uncovering new particles or forces and
leading to new technologies.
Dark
Energy
What
is Dark Energy?
Dark
energy is a mysterious force that is driving the accelerated expansion of the
universe. Unlike dark matter, which clumps and exerts gravitational attraction,
dark energy appears to have a repulsive effect, working against gravity to push
galaxies apart.
Evidence
for Dark Energy:
- Accelerating Universe: Observations of distant supernovae in the late
1990s revealed that the universe's expansion is accelerating, contrary to
the expectation that gravity would slow it down. This acceleration
suggests the presence of dark energy.
- Cosmic Microwave Background (CMB): Detailed measurements of the CMB suggest that
dark energy makes up about 68% of the universe's total energy density.
- Large-Scale Structure: The distribution and clustering of galaxies on
large scales are consistent with the presence of dark energy.
Importance
of Dark Energy:
- Fate of the Universe: Dark energy is crucial in determining the
ultimate fate of the universe. If dark energy continues to dominate, the
universe could keep expanding indefinitely, leading to scenarios like the
"Big Freeze" or "Heat Death."
- Cosmological Constant: Dark energy is often associated with the
cosmological constant (Λ), a term Einstein introduced in his equations of
General Relativity. Understanding dark energy could provide insights into
the fundamental nature of space-time.
Applications
and Usefulness:
Like
dark matter, dark energy has no direct applications currently. However,
understanding it could lead to profound changes in our understanding of the
universe and potentially new technologies.
References
for Further Reading
- Books:
- “The 4 Percent Universe: Dark Matter, Dark
Energy, and the Race to Discover the Rest of Reality” by Richard Panek.
- “Dark Matter and Dark Energy: The Hidden 95% of the
Universe” by Brian Clegg.
- Scientific Papers and Articles:
- “A Brief History of Dark Matter” by J. W. Moffat, published in the European Journal of Physics (2011).
- “Dark Energy and the Accelerating Universe” by S. Perlmutter, B. Schmidt, and A. Riess,
Nobel Lecture (2011).
- Websites:
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