- 4314 -
HISTORY OF THE
UNIVERSE. Here is the model we
have for universe creation at this time.
It is called the “Big Bang model”.
It states that the universe began as an incredibly hot, dense point
roughly 13.7 billion years ago.
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------------------------- 4314 - HISTORY OF THE UNIVERSE.
- The most distant
light we can see is the “cosmic microwave background” (CMB), which has taken
more than 13,000,000,000 years to reach us. This marks the edge of the
observable universe, and while you might think that means the Universe is 26
billion light-years across, thanks to cosmic expansion it is now closer to 46
billion light-years across.
-
- Most cosmologists
think the Universe is much larger than our observable corner of it. That what
we can see is a small part of an unimaginably vast, if not infinite creation.
-
- There are several
reasons why cosmologists think the Universe is large. One is the distribution
of galaxy clusters. If the Universe didn’t extend beyond what we see, the most
distant galaxies would feel a gravitational pull toward our region of the
cosmos, but not away from us, leading to asymmetrical clustering. Since
galaxies cluster at around the same scale throughout the visible universe. In
other words, the observable universe is “homogenous and isotropic”.
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- A second point is
that spacetime is “flat”. If spacetime weren’t flat, our view of distant
galaxies would be distorted, making them appear much larger or smaller than
they actually are. Distant galaxies do appear slightly larger due to cosmic
expansion, but not in a way that implies an overall curvature to spacetime.
Based on the limits of our observations, the flatness of the cosmos implies it
is at least 400 times larger than the observable universe.
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- “Inflation” would
make the CMB temperature uniform. Then
there is the fact that the cosmic microwave background is almost a perfect
blackbody. There are small fluctuations in its temperature, but it is much more
uniform than it should be.
-
- To account for
this, astronomers have proposed a period of tremendous expansion just after the
Big Bang, known as “early cosmic inflation”. We have not observed any direct
evidence of it, but the model solves so many cosmological problems that it’s
widely accepted. If the model is accurate, then the Universe is on the order of
1,026 times larger than the observable universe.
-
- Although string
theory is often presented as a physical theory, it’s actually a collection of
mathematical methods. It can be used in the development of complex physical
models, but it can also just be mathematics for its own sake.
-
- If early cosmic
inflation is true, we should be able to observe its effect through
“gravitational waves” in the somewhat near future. If that fails, it might be
worth looking more closely at string theory models.
-
- The Big Bang model
was not an explosion in space, as the theory's name might suggest. Instead, it
was the appearance of space everywhere in the universe. According to the Big Bang theory, the
universe was born as a very hot, very dense, single point in space.
-
- The cosmic
microwave background contains the afterglow of light and radiation left over
from the Big Bang. This relic of the Big Bang pervades the universe and is
visible to microwave detectors, which allows scientists to piece together clues
of the early universe.
-
- In 2001, NASA
launched the “Wilkinson Microwave Anisotropy Probe” (WMAP) mission to study the
conditions as they existed in the early universe by measuring radiation from
the cosmic microwave background. Among other discoveries, WMAP was able to
determine the age of the univers, about 13.7 billion years old.
-
- When the universe
was very young, something like a hundredth of a billionth of a trillionth of a
trillionth of a second, it underwent an incredible growth spurt. During this
burst of expansion, which is known as “inflation”, the universe grew
exponentially and doubled in size at least 90 times.
-
- The universe was
expanding, and as it expanded, it got cooler and less dense. After inflation, the universe continued to
grow, but at a slower rate. As space
expanded, the universe cooled and matter formed.
-
- Light chemical
elements were created within the first three minutes of the universe's
formation. As the universe expanded, temperatures cooled and protons and
neutrons collided to make deuterium, which is an isotope of hydrogen. Much of
this deuterium combined to make helium.
-
- For the first
380,000 years after the Big Bang, however, the intense heat from the universe's
creation made it essentially too hot for light to shine. Atoms crashed together
with enough force to break up into a dense, opaque plasma of protons, neutrons
and electrons that scattered light like fog.
-
- About 380,000
years after the Big Bang, matter cooled enough for electrons to combine with
nuclei to form neutral atoms. This phase is known as "recombination,"
and the absorption of free electrons caused the universe to become transparent.
The light that was unleashed at this time is detectable today in the form of
radiation from the “cosmic microwave background”.
-
- The era of
recombination was followed by a period of darkness before stars and other
bright objects were formed. Roughly 400
million years after the Big Bang, the universe began to come out of its dark
ages. This period in the universe's evolution is called the age of
“re-ionization”.
-
- During this time,
clumps of gas collapsed enough to form the very first stars and galaxies. The
emitted ultraviolet light from these energetic events cleared out and destroyed
most of the surrounding neutral hydrogen gas. The process of re-ionization,
plus the clearing of foggy hydrogen gas, caused the universe to become
transparent to ultraviolet light for the first time.
-
- Data from older
missions like WMAP and the “Cosmic Background Explorer” (COBE), which launched
in 1989, and missions still in operation, like the Hubble Space Telescope,
which launched in 1990, all help scientists try to solve the most enduring
mysteries and answer the most debated questions in cosmology.
-
- Our solar system
is estimated to have been born a little after 9 billion years after the Big
Bang, making it about 4.6 billion years old. According to current estimates,
the sun is one of more than 100 billion stars in our Milky Way galaxy alone,
and orbits roughly 25,000 light-years from the galactic core.
-
- The sun and the
rest of our solar system was formed from a giant, rotating cloud of gas and
dust known as the “solar nebula”. As gravity caused the nebula to collapse, it
spun faster and flattened into a disk. During this phase, most of the material
was pulled toward the center to form the sun.
-
- In the 1960s and
1970s, astronomers began thinking that there might be more mass in the universe
than what is visible. Vera Rubin, an astronomer at the Carnegie Institution of
Washington, observed the speeds of stars at various locations in galaxies.
-
- Basic Newtonian
physics implies that stars on the outskirts of a galaxy would orbit more slowly
than stars at the center, but Rubin found no difference in the velocities of
stars farther out. In fact, she found that all stars in a galaxy seem to circle
the center at more or less the same speed.
-
- This mysterious and
invisible mass became known as “dark matter”. Dark matter is inferred because
of the gravitational pull it exerts on regular matter. One hypothesis states
the mysterious stuff could be formed by exotic particles that don't interact
with light or regular matter, which is why it has been so difficult to detect.
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- In the 1920s,
astronomer Edwin Hubble made a revolutionary discovery about the universe.
Using a newly constructed telescope at the Mount Wilson Observatory in Los
Angeles, Hubble observed that the universe is not static, but rather is
expanding.
-
- Decades later, in
1998, the prolific space telescope named after the famous astronomer, the
Hubble Space Telescope, studied very distant supernovas and found that, a long
time ago, the universe was expanding more slowly than it is today. This
discovery was surprising because it was long thought that the gravity of matter
in the universe would slow its expansion, or even cause it to contract.
-
- Dark energy is
thought to be the strange force that is pulling the cosmos apart at
ever-increasing speeds, but it remains undetected and shrouded in mystery. The
existence of this elusive energy, which is thought to make up 80% of the
universe, is one of the most hotly debated topics in cosmology.
-
- While much has
been discovered about the creation and evolution of the universe, there are
enduring questions that remain unanswered. Dark matter and dark energy remain
two of the biggest mysteries, but cosmologists continue to probe the universe
in hopes of better understanding how it all began.
-
-
-January 10, 2023
HISTORY OF THE
UNIVERSE. 4314
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