Учебная работа. Big Bang theory

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Big Bang theory

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Big Bang Theory

(essay)

A cosmological model to explain the origins of matter,
energy, space, and time, the Big Bang theory asserts that the universe began at
a certain made it possible to peer
further into the universe and process the enormous amounts of data those
observations generated. The term “big bang” comes from its underlying
hypothesis, that the universe has not been eternal but emerged out of a sudden,
almost incomprehensibly vast explosion.

Scientists’ understanding of the Big Bang theory emerges out
of two separate fields of inquiry: theoretical physics and observational
astronomy. According to what are called the Friedmann models, a set of complex
metrics named for Alexander Friedmann, an early twentieth century Soviet
physicist who first developed them, the Big Bang theory fits in with two of the
most important theories of twentieth century physics: the cosmological
principle (which says that basic physical properties are the same throughout
the universe) and Albert Einstein’s General Theory of Relativity of 1915-1916,
which conceives of gravity as a curvature in space and time. That convergence
of ideas, say physicists, provides the theoretical underpinning of the Big Bang
theory.

Astronomers have made their own confirmations of the Big Bang
theory. Analyzing the light coming from other galaxies, they have noted shorter
and longer wavelengths proportional to the distances of the galaxies from
Earth, indicating that they are moving away from the Earth and thus that space
itself is expanding. The existence of cosmic microwave radiation, a remnant of
hot ionized plasma of the early universe offers more proof of the Big Bang, as
does the distribution of heavier and lighter elements through the universe.

Timeline
of the Big Bang

The Big Bang theory hypothesizes that there were time-based
stages in the origins of the universe. The first stage-or, at least, the first
stage that cosmologists can theorize about given current understanding of
physics-is known as the Planck era, after the German scientist of the late
nineteenth and early twentieth centuries who studied the physics that explain
it. The Planck era was extremely brief-just 10-43 seconds (also
known as one Planck time). During this period, all four forces of the
universe-gravity, electromagnetic energy, and the weak and strong nuclear
forces-were theoretically equal to one another, implying that there may have
been just one unified force. The Planck era was extremely unstable, with the
four forces quickly evolving into their current forms, starting with gravity
and then the strong nuclear force (what binds protons and neutrons together in
the nucleus of an atom), the weak nuclear force (associated with radioactive
decay, it is some 100 times weaker than the strong force), and finally
electromagnetic energy. This process is known as symmetry breaking and led to a
longer period in the universe’s history—though, at one millionth of a second,
still extremely brief in ordinary time—known as the “inflation era.”
Physicists, however, are not certain of the energy force that led to this inflation.
At one second in age, the universe now consisted of fundamental energy and
sub-atomic particles such as quarks, electrons, photons, and other less
familiar particles.

The next stage in the Big Bang-lasting for roughly 100,000
years and beginning about three seconds after the Planck era-consisted of the
process of nucleosynthesis, as protons and neutrons came into being and began
to the form the nuclei of various elements, predominantly hydrogen and helium,
the two lightest elements in the periodic table and the two most common
elements in the universe. Yet matter as we know it still did not exist and for
those hundred thousand or so years, the universe essentially consisted of
radiation in the form of light, radio waves, and X-rays. This period, known as
the “radiation era,” came to a gradual end as free floating atomic nuclei
bonded with free-floating electrons to produce the matter with which the
universe would subsequently consist. While time was critical to the process so
was temperature and density, with the various changes corresponding to a
gradual cooling of the universe and the gradual dispersing of matter.

It took some 200 million years for gravity to begin
coalescing these free-floating atoms into the primordial gas out of which the
first stars and galaxies would emerge. Over billions of years, such early stars
and galaxies phased through their lifecycle, using up their nuclear fuel and
collapsing in on themselves, spewing out vast new clouds of matter and energy that
would eventually form new generations of stars and galaxies. The sun around
which the earth and the solar system rotate is one of these later generation
stars, formed roughly five billion years ago.

Fate of the Universe

The Big Bang theory concerns not just the origins of the
universe but its ultimate fate. The critical question, of course, is whether
the universe will continue expanding forever or eventually fall back into
itself, creating, perhaps, the conditions for the next Big Bang. Gravity is the
critical factor here, with three outcomes possible. The first, and most widely
accepted by physicists, is that there is not the critical density, known as
omega and estimated at roughly six hydrogen atoms per cubic meter, necessary to
pull the universe back in on itself. In this model, referred to as the “open”
model, the universe will continue to expand and cool indefinitely. If however,
the density of he universe is greater than omega then the universe will
eventually, after billions of years, collapse in what physicists call the “big
crunch.” A third and highly unlikely possibility is that omega equals precisely
one; in this model, the universe gradually slows and cools to a static state.

While it would seem at first glance that the fate of the
universe-that is, whether matter exceeded omega or not—could be determined by
the admittedly complex but not impossible task of calculating the amount of
matter and dividing it by the dimensions of the universe, in fact, there is a
complicating factor. The galaxies and nebulae, or primordial dust clouds out of
which stars and galaxies, do not pull on themselves or on each another as they
should. That is to say, they behave as if there was more mass and, hence,
gravitational pull than can be observed. For example, the Andromeda galaxy, the
nearest neighbor to our own Milky Way galaxy, is rushing toward us at 200,000
miles per hour, a speed that cannot be explained by the gravitational force of
the matter in the two galaxies. In fact, the two galaxies are coming together
at a pace requiring some 10 times that amount of matter. Physicists offer the
possibility that there is dark matter in the universe, that is, an unknown type
of matter that does not emit or reflect enough electromagnetic energy to be
observable by current means. Such dark matter, according to this hypothesis,
exists in haloes around galaxies and may be what composes black holes and
massive clouds of neutrinos, particles formed from radioactive decay with
little mass and no electric charge. Such dark matter would imply a universe
that eventually collapses in on itself, except for an additional complicating
factor.

Scientists hypothesize that there is also a dark energy in
the universe counteracting both matter and dark matter, a kind of
anti-gravitational force that is also undetectable with existing technology.
While dark matter is believed to constitute 22 percent of the universe, dark
energy is believe to compose 74 percent. These numbers, along with the
difficulties of detecting dark matter and energy make it impossible for
physicists as of the early twenty-first century to come to a definitive
conclusion about the ultimate fate of the universe.

Pre-Twentieth Century Ideas of Universe’s Origins

The origins of creation have, of course, preoccupied humanity
since at least the beginning of civilization itself. Virtually every culture
around the world has created myths to explain how the universe came into being,
even if they did not necessarily comprehend the universe’s magnitude and
complexity. These cosmologies, or explanations for the existence of creation,
generally share four basic ideas. First, there is an intelligence or creator
behind creation. Second, the universe came into being at a specific And the final element was that, once the universe was
created, it remained essentially static—nothing added, nothing taken away, all
matter and energy in perpetual balance. That, too, was the model advanced by
English scientist Isaac Newton in the late seventeenth and early eighteenth
centuries, whose understanding of the laws of the universe dominated physics
for more than 200 years. But even in Newton’s own time, the idea of a
perpetually balanced creation was questioned by some thinkers, who pointed out
that the universe would come apart if just one object should slip out of
balance. And while Newton’s laws attempted to explain how the universe
operated, they did not offer much insight into its origins.

Immanuel Kant, a German philosopher of the late eighteenth
century, was the first major Western thinker to tackle the question that the
Big Bang theory would eventually answer-had the universe always existed or did
it come into existence at a specific Early
Hypotheses

Early twentieth century physicists and astronomers, of
course, would prove Kant wrong. In 1912, an American astronomer named Vesto
Slipher noted a Doppler shift in the wavelengths of light coming from spiral
nebulae, an antiquated term for galaxies, dating from before the existence of
other galaxies was confirmed. (It was American astronomer Edwin Hubble who
first concluded in the mid-1920s that the nebulae were, in fact, galaxies
similar to our own Milky Way.) The Doppler shift, named after Christian
Doppler, the early nineteenth century Austrian mathematician who discovered it,
says that waves alter in relation to the movement of the observer or the object
causing the wave. While Slipher noted that almost all such spiral nebulae were
moving away from the Earth, he failed to reach the conclusion that this meant
the universe was expanding.

Around the same time, Slipher was making his observations,
Friedmann, the Soviet physicist, explained how Einstein’s General Relativity
Theory might prove that the universe was expanding. Einstein’s theory updated
and revised Newton’s gravitational laws, for conditions where enormous mass and
energy existed. Newton concluded that gravity was a force between two masses;
Einstein argued, correctly as it was proved by later experiments, that gravity
was the warping of space and time caused by mass. While Newton’s model of
gravity was not consistent with the Big Bang theory-since there was no mass in
the primordial state of heat and density at the beginning of time-Einstein’s
allowed for the possibility of gravity itself coming into being, though,
ironically, Einstein himself held to a static view of the universe when he came
up with his General Relativity Theory.

Roughly a decade after Friedmann developed his models out of
Einstein’s General Relativity Theory-models that, while published, generally
got overlooked by other physicists—a Belgian physicist and astronomer Georges
Lemaître, independently coming up with the
same theories as Friedmann, used them to reach the conclusion that had eluded
Slipher-that receding nebulae meant the universe was expanding. In 1931, Lemaître also hypothesized that
the universe must have begun with a single atom, an idea that came to be called
the “cosmic egg” theory. American astronomer Edwin Hubble, the first to realize
that nebulae were in fact other galaxies, also confirmed that the galaxies all
seemed to be moving away from us simultaneously. Extrapolating backward, Hubble
believed that they all had emerged from the same high-density place, exploding
outward in a kind of initial fireball. Hubble made his findings by noting
shifts in the light spectrum of distant galaxies that fit in with the Doppler
effect.

Despite such findings, a competing theory emerged in the
years after World War II,. The “steady state” model, advocated by British
astronomer Frederick Hoyle, held that new matter was created as the universe
expanded. A confirmed atheist, Hoyle rejected the “cosmic egg” theory as it
seemed to imply the existence of a creator. Ironically, it was Hoyle who, in
the 1950s, coined the term “Big Bang,” using it in a radio interview to
ridicule Lemaître’s ideas. To reconcile his constant
universe idea and the observed fact that galaxies were moving away from each
other, Hoyle hypothesized that new galaxies came into being as older ones grew
apart. While later discounted, Hoyle’s work was useful in explaining how matter
and energy came into existence, a key component of the Big Bang theory.

Confirmation of the Big Bang Theory

For two decades the two theories vied with each other, though
Lemaître’s steadily gained more advocates.
The critical confirmation of the Big Bang theory came in 1964. That year, Arno
Penzias and Robert Wilson, two scientists working for Bell Laboratories,
noticed that Background microwave radiation, a residual form of energy from the
Big Bang, permeated the universe, confirming an idea first propounded by Soviet
physicist George Gamow and American physicist Ralph Alpher in the late 1940s.

As the twenty-first century dawns, scientists-like the
ancients long before them—are still grappling with the very moment of
creation, before the radiation, inflation, and Planck eras. Many believe that
unveiling that moment is connected to the development of a Grand Unified
Theory, a single explanation that fits all of the known laws of the
universe-including Einstein’s General Relativity Theory and quantum mechanics,
the study of energy and matter at the sub-atomic level-into a single equation.
As British physicist Stephen Hawking notes, "At
the Big Bang, the universe and time itself came into existence, so that this is
the first cause. If we could understand the Big Bang, we would know why the
universe is the way it is. It used to be thought that it was impossible to
apply the laws of science to the beginning of the universe, and indeed that it
was sacrilegious to try. But recent developments in unifying the two pillars of
twentieth-century science, Einstein’s General Theory of Relativity and the
Quantum Theory, have encouraged us to believe that it may be possible to find
laws that hold even at the creation of the universe."

References

1.       Farrell,
John. The Day without Yesterday: Lemaître, Einstein, and the Birth
of Modern Cosmology. New York: Thunder’s Mouth Press, 2005.

2.       Fox,
Karen C. The Big Bank Theory: What It Is, Where It Came from, and Why It Works.
New York: Wiley, 2002.

3.       Hawking,
Stephen. A Brief History of Time: From the Big Bang to Black Holes. New York:
Bantam, 1988.

4.       Levin,
Frank. Calibrating the Cosmos: How Cosmology Explains Our Big Bang Universe.
New York: Springer, 2007.

5.       Singh,
Simon. Big Bang: The Origin of the Universe. New York: Fourth Estate, 2004.

Учебная работа. Big Bang theory