Steady State Theory
Summary
TLDRThis video explores the steady-state theory, an alternative to the widely accepted big bang theory, which posits an unchanging, infinitely old universe. Developed by Hoyle, Bondi, and Gold in 1948, it suggests continuous creation of matter to maintain a constant density despite expansion. However, evidence from radio sources, quasars, and the cosmic microwave background radiation contradicts this theory, leading to its decline in favor of the big bang model, which describes a universe that began hot and dense 13.7 billion years ago and has been expanding and cooling since.
Takeaways
- 🌌 The Steady State Theory was an alternative to the Big Bang Theory, proposing an infinite, unchanging universe without a beginning or end.
- 🔍 The Big Bang Theory, first proposed by Georges Lemaître in 1931, suggests the universe began from an explosion of a 'primeval atom' and has been expanding since.
- 📊 The Big Bang Theory aligns with observations and has been refined over 90 years to explain the universe's origin and current state.
- 📖 The Perfect Cosmological Principle central to the Steady State Theory posits the universe is the same in all directions at all times, with no evolution or change.
- 🌟 The Steady State Theory predicted continuous creation of new stars and galaxies to maintain a constant density, even as the universe expands.
- 🌌 Hubble's Law, discovered in the late 1920s, indicates that galaxies move away from us, with speed proportional to their distance, supporting the expanding universe concept.
- 📈 The universe's expansion was visualized in an animation, showing galaxies moving apart and decreasing in density over time according to the Big Bang Theory.
- 💥 The Steady State Theory was challenged by observations of more radio sources and quasars in the early universe, indicating change over time.
- 🌡️ The discovery of the cosmic microwave background radiation in 1965 provided strong evidence against the Steady State Theory, as it is a relic from the early, hot universe.
- 🔨 The Steady State Theory was ultimately discredited by evidence of an evolving universe and the inability to explain the cosmic microwave background radiation.
- 👤 Stephen Hawking acknowledged the Steady State Theory as a good scientific theory due to its testable predictions, despite being falsified.
Q & A
What is the Steady State Theory?
-The Steady State Theory is an alternative to the Big Bang Theory, suggesting that the universe is infinite in extent, infinitely old, and remains the same in all directions at all times. It was developed in 1948 by Fred Hoyle, Hermann Bondi, and Thomas Gold.
What is the central principle of the Steady State Theory?
-The central principle of the Steady State Theory is the Perfect Cosmological Principle, which states that the universe does not evolve or change over time.
How does the Steady State Theory explain the universe's expansion?
-In the Steady State Theory, the universe's expansion is balanced by the continuous creation of new matter, maintaining a constant overall density.
What is the significance of the Big Bang Theory's development over the years?
-The Big Bang Theory has been refined over the years to match observations, stating that the universe originated from an incredibly hot and dense state 13.7 billion years ago and has been expanding and cooling ever since.
What evidence supports the Big Bang Theory over the Steady State Theory?
-Evidence such as the discovery of the cosmic microwave background radiation, the observation of more radio sources at greater distances, and the presence of quasars in the early universe support the Big Bang Theory, indicating that the universe has changed over time.
What is Hubble's Law and how does it relate to the universe's expansion?
-Hubble's Law states that the further away a galaxy is from us, the faster it appears to be moving away. This relationship, discovered in the late 1920s, supports the idea that the universe is expanding.
What is the cosmic microwave background radiation and why is it significant?
-The cosmic microwave background radiation is a weak radiation that fills all of space and has a uniform temperature of 2.7 degrees above absolute zero. It is significant because it is a relic from the early universe, supporting the Big Bang Theory.
How does the Steady State Theory explain the creation of new stars and galaxies?
-The Steady State Theory suggests that new matter is continuously created out of nothing at a very small rate, eventually forming new stars and galaxies, maintaining a constant density over large regions of space.
What is the role of the Hubble constant in understanding the universe's expansion?
-The Hubble constant, denoted as H naught, represents the rate of expansion of the universe. It is crucial in determining the relationship between a galaxy's distance from Earth and its speed of recession.
Why did the Steady State Theory become obsolete despite its elegance?
-The Steady State Theory became obsolete due to observational evidence that contradicted its predictions, such as the discovery of the cosmic microwave background radiation and the changing number of radio sources and quasars over time.
What did Stephen Hawking say about the Steady State Theory?
-Stephen Hawking noted that the Steady State Theory was a good scientific theory in the sense that it made definite predictions that could be tested and potentially falsified, which they ultimately were.
Outlines
🌌 The Steady State Theory vs. Big Bang Theory
This paragraph introduces the Steady State Theory as an alternative to the Big Bang Theory, both of which explain the universe's origin and fate. The Steady State Theory, popular in the 1950s, suggests an infinite, unchanging universe. It was proposed by Fred Hoyle, Hermann Bondi, and Thomas Gold in 1948, based on the cosmological principle. The Big Bang Theory, however, posits that the universe began from an explosion of a 'primeval atom' and has been expanding and cooling since. Observations since the 1920s support the universe's expansion, leading to the Big Bang Theory's acceptance by most cosmologists. The paragraph also discusses the implications of this expansion, such as galaxies moving away from each other, and introduces Hubble's Law.
🌟 The Expansion and Density of the Universe
This paragraph delves into the implications of the universe's expansion on the density and distribution of galaxies. As the universe expands, the average distance between galaxies increases, leading to a decrease in matter density. The Steady State Theory maintains that the universe's overall density remains constant by continuously creating new matter, even as it expands. This theory suggests that new stars and galaxies form at a rate that balances the fading of older stars, keeping the universe's appearance consistent over time. The paragraph also contrasts this with the Big Bang Theory, which implies a changing universe over time, and highlights the role of the Hubble constant in measuring the rate of expansion.
🔍 Observational Evidence Against the Steady State Theory
This paragraph discusses the observational evidence that led to the decline of the Steady State Theory. Radio telescope observations revealed more radio sources at greater distances than predicted by the theory, suggesting a changing universe. The discovery of quasars, extremely bright objects found only at great distances, further indicated a universe that evolves over time. The most significant evidence against the Steady State Theory came from the discovery of the cosmic microwave background radiation in 1965. This radiation, predicted by the Big Bang Theory and detected accidentally, is nearly impossible to explain under the Steady State Theory. By the early 1970s, the Steady State Theory was largely abandoned in favor of the Big Bang Theory, although it is acknowledged for its scientific merit in making testable predictions.
Mindmap
Keywords
💡Steady State Theory
💡Big Bang Theory
💡Georges Lemaître
💡Cosmic Microwave Background Radiation
💡Hubble's Law
💡Quasars
💡Perfect Cosmological Principle
💡Hubble Constant
💡Radio Sources
💡Matter Creation
💡Karl Popper
Highlights
The steady-state theory was an alternative to the Big Bang theory, suggesting the universe is unchanging and infinitely old.
The Big Bang theory, proposed by Georges Lemaître in 1931, describes the universe's origin from a hot and dense state 13.7 billion years ago.
The Big Bang theory is currently accepted by most cosmologists, having been developed and refined over the last 90 years.
The steady-state theory was developed in 1948 by Fred Hoyle, Hermann Bondi, and Thomas Gold, based on the cosmological principle.
The cosmological principle posits that the universe is infinite, unchanging, and homogeneous in all directions and times.
The steady-state theory suggests new stars and galaxies are continuously created to maintain a constant density in large regions of the universe.
Hubble's law, discovered in the late 1920s, indicates that galaxies move away from us, with speed proportional to their distance.
The Hubble constant measures the rate of the universe's expansion, as shown in the relationship between distance and recessional velocity.
The steady-state theory implies a constant matter density despite the universe's expansion, achieved by continuous matter creation.
The Big Bang theory predicts a decrease in matter density and galaxy count in a given space as the universe expands.
Observations with radio telescopes found more radio sources at great distances, contradicting the steady-state theory.
The discovery of quasars in 1963 provided evidence of a changing universe, as they are only found in the early universe.
The cosmic microwave background radiation, discovered in 1965, is a relic from the early universe, supporting the Big Bang theory.
The steady-state theory struggles to explain the origin of the cosmic microwave background radiation.
By the 1970s, the steady-state theory was largely discredited due to observational evidence supporting the Big Bang theory.
Stephen Hawking acknowledged the steady-state theory as a good scientific theory for its testable predictions, despite being falsified.
Transcripts
[Music]
this video
talks about the steady state theory it's
an elegant alternative to the big bang
which describes not only the origin of
the universe
but its ultimate fate it was very
popular
amongst astronomers in the 50s but is
now
obsolete
it's been known since 1929 that the
universe is expanding
in 1931 the belgian catholic priest
and astronomer georges lemaitre proposed
that the universe began
with the explosion of something he
called the primeval atom
over the last 90 years this theory
which is now called the big bang theory
has been developed
and refined to match observations
it states that the universe originated
from an incredibly hot
and dense state 13.7 billion years ago
and it's been expanding and cooling ever
since
the big bang theory is now generally
accepted by most cosmologists
however for a while an alternative
theory
the steady-state theory was very popular
this theory was developed in 1948
by fred hoyle
hermann bondi and thomas gold
at the heart of the steady-state theory
is the perfect
cosmological principle this states the
universe is
infinite in extent infinitely old
and if you take it as a whole it's the
same in
all directions at all times in the past
and at all times in the future
in other words the universe doesn't
evolve
or change over time
clearly if we take a relatively small
region of the universe
such as the neighborhood of the sun in
the milky way
then this does change over time as
individual
stars burn up the fuel and die and
eventually become objects such as black
dwarfs
neutron stars and if they're massive
enough even black holes
the steady-state theory predicts however
if we take a large enough region of
the universe perhaps hundreds of
millions of light years across
new stars and indeed new galaxies
are continually created all the time
at just the rate needed to replace the
stars which have used up the fuel and
have stopped shining
so over this very large region of space
again we're talking hundreds of millions
of light years across
the average amount of light emitted
doesn't change over time
our milky way galaxy is a typical large
spiral galaxy
and is believed to contain over 400
billion stars
the observable universe is composed of
hundreds of billions
of galaxies
as i mentioned before it's been known
since the late 1920s
that the universe is expanding this
means that when we look at distant
galaxies
they appear to be moving away from us
the further away a galaxy is from us
the faster it appears to be moving away
this relationship which is known as
hubble's law
is shown in simplified form in the
diagram
the horizontal axis gives a distance
from the earth
in megaparsecs where a megaparsec is
3.26 million light years
megaparsec is a unit often used by
astronomers when
measuring very large distances on
galactic scales
the vertical axis gives the speed in
kilometers per second
that the galaxy is moving away from us
the rate of expansion which is the slope
in the graph
is given by something called the hubble
constant
which is normally called h naught
in this very simple animation i'm going
to show you what happens
assuming the big bang theory is correct
over tens of billions of years
if we take a small region of space and
you imagine
each white ellipse is a galaxy then
as the universe expands the average
distance between
galaxies increases there are fewer
galaxies in a given region of space
and the density the average density of
matter
in this given region of space drops
in the steady state theory even though
the universe
is expanding its overall density remains
constant
the theory achieves this by assuming
that new matter
is continuously created out of literally
nothing
at the incredibly small rate of one atom
per hydrogen per six cubic kilometers of
space
per year this matter
eventually forms new stars and new
galaxies
and if we take a large enough region of
space
the density which is the amount of
matter in a given volume
doesn't change over time
if we rerun the animation assuming the
steady-state theory is correct
over billions of years and once again
you imagine
each small white ellipse is a galaxy
then as the universe expands new
galaxies
shown as yellow ellipses are created
from this created matter
and the total number of galaxies in the
region of space
doesn't actually change
indeed if the steady state theory were
true
then an observer would measure the same
values of
the average density of the universe
the average distance between galaxies
the average brightness of galaxies and
how the speed
the galaxies are moving away from each
other varies
as the distance this is the relationship
known as the hubble constant in all
regions of the universe
at any time in the past no matter how
far
back we go or any time in the future
in the steady state theory the universe
is
infinitely old and unchanging
one of the most elegant features of the
theory is that because the universe is
infinitely old
the question of its origin just doesn't
arise
it has always existed in its current
form
this contrasts with the big bang theory
um where is a creation event occurred
causing the universe to come into being
similarly the question of his ultimate
fate doesn't arise either
it will always exist
[Music]
[Applause]
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firstly observations taken with radio
telescopes
show there are more radio sources a long
distance away from us
than would be predicted by the steady
state theory
by a long distance i mean billions of
light years
because of the time it takes light to
reaches
when we look at objects billions of
light years from us
we're looking back billions of years in
time
so what these observations were saying
is there are more
cosmic radio sources billions of years
ago
than there are now this suggests
the universe is changing over time
which contradicts the steady-state
theory
another piece of evidence to discredit
the theory
emerged in 1963 when a whole new class
of astronomical objects
called quasars were discovered
quasars are incredibly bright objects
which can be up to a thousand times
brighter than our milky way galaxy but
they're very
small compared to the size of a galaxy
quasars are only found at great
distances from us
meaning that the light from them was
emitted billions of years ago
the fact that quasars are only found in
the early universe
provides very strong evidence that the
universe
has changed over time
however the real nail in the coffin of
the steady state theory
author's discovery in 65 of the cosmic
bike microwave background radiation this
is a weak
radiation which fills the whole of space
and is the same in all directions
it has the same spectrum as an object of
a temperature
of 2.7 degrees above absolute zero
in the big bang theory this radiation
is a relic or a snapshot from the time
the universe was young and hot and
interestingly it was predicted
in 1948 almost 20 years before its
accidental discovery
however in the steady state theory it is
almost impossible to explain the origin
of this radiation
for the reasons given above by the early
1970s
the steady-state theory was no longer
accepted
by the vast majority of cosmologists
and the big bang theory is now generally
believed to explain the origin of the
universe
however despite this it can still be
argued that the steady-state theory is a
good
theory as illustrated by the words of
stephen hawking
the steady state theory was what
karl popper would call a good scientific
theory it made definite predictions
which could be tested by observation
and possible falsified
unfortunate further theory
they were falsified
[Music]
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you
関連動画をさらに表示
The Steady State Theory of The Universe
What Is the Steady-State Theory in Cosmology?
Comparing The Big Bang and The Steady State Theories
SHS Earth and Life Science ELS Q1 Origin of the Universe
The Big Bang Theory Exploring the Origins of the Universe (4 Minutes)
LESSON ON THE ORIGIN OF THE UNIVERSE AND BIG BANG THEORY | IN FILIPINO
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