Steady State Theory

Explaining Science

1 Oct 202012:53

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

00:00

🌌 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.

05:02

🌟 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.

10:03

🔍 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

The Steady State Theory was an alternative cosmological model that proposed the universe has no beginning or end and remains unchanged over time. It was popular in the 1950s but has since been largely discredited. The theory was developed by Fred Hoyle, Hermann Bondi, and Thomas Gold in 1948 and is characterized by the perfect cosmological principle, which states that the universe is infinite, unchanging, and homogeneous. The video discusses how this theory was challenged by observations that showed the universe is evolving, such as the discovery of quasars and the cosmic microwave background radiation.

💡Big Bang Theory

The Big Bang Theory is the prevailing cosmological model that explains the origin of the universe as beginning from an incredibly hot and dense state about 13.7 billion years ago. It suggests that the universe has been expanding and cooling ever since. The video script mentions that this theory has been developed and refined over the last 90 years to match observations and is now generally accepted by most cosmologists. It contrasts with the Steady State Theory by positing a creation event and an evolving universe.

💡Georges Lemaître

Georges Lemaître was a Belgian Catholic priest and astronomer who, in 1931, proposed the idea that the universe began with the explosion of something he called the 'primeval atom.' His work laid the foundation for what is now known as the Big Bang Theory. The video script highlights his contribution to the understanding of the universe's origin, which was a significant departure from the static universe view proposed by the Steady State Theory.

💡Cosmic Microwave Background Radiation

The Cosmic Microwave Background Radiation (CMBR) is a faint radiation that fills the universe and is considered a relic from the early universe. It has a nearly uniform temperature of about 2.7 Kelvin above absolute zero. The video script explains that the discovery of this radiation in 1965 was a major blow to the Steady State Theory because it provided strong evidence for a hot, dense early universe, which is a key prediction of the Big Bang Theory.

💡Hubble's Law

Hubble's Law describes the observation that galaxies appear to be moving away from us, with the speed of their recession proportional to their distance. This relationship, discovered in the late 1920s, supports the idea of an expanding universe. The video script uses Hubble's Law to illustrate how the universe's expansion is evidenced by the observation that more distant galaxies are moving away faster, which is inconsistent with the Steady State Theory's claim of a constant universe.

💡Quasars

Quasars are extremely bright astronomical objects that can outshine entire galaxies, yet are very small in size. The video script mentions that quasars are found only at great distances, indicating that they were much more common in the early universe. Their discovery in 1963 provided evidence against the Steady State Theory by showing that the universe has changed significantly over time.

💡Perfect Cosmological Principle

The Perfect Cosmological Principle is a central tenet of the Steady State Theory, stating that the universe is infinite in extent, infinitely old, and remains the same in all directions at all times. The video script explains that this principle implies that the universe does not evolve or change over time, which is contradicted by observations that show the universe is expanding and evolving.

💡Hubble Constant

The Hubble Constant, often denoted as H0, is a measure of the rate of expansion of the universe. It is derived from Hubble's Law and is expressed in units of kilometers per second per megaparsec. The video script uses the Hubble Constant to describe how the speed at which galaxies are moving away from us increases with their distance, supporting the Big Bang Theory's view of an expanding universe.

💡Radio Sources

Radio sources are astronomical objects that emit radio waves. The video script discusses how observations with radio telescopes showed more radio sources at great distances than predicted by the Steady State Theory. This finding indicated that the universe has changed over time, contradicting the theory's claim of a static universe.

💡Matter Creation

In the context of the Steady State Theory, matter creation refers to the continuous creation of matter out of nothing at a very low rate, such as one hydrogen atom per six cubic kilometers per year. The video script explains that this concept was proposed to maintain a constant density in the universe despite its expansion, but it has been disproven by evidence of an evolving universe.

💡Karl Popper

Karl Popper was a philosopher of science known for his concept of falsifiability, which states that a scientific theory must be testable and potentially falsifiable by empirical observations. The video script quotes Stephen Hawking's view that the Steady State Theory was a good scientific theory in Popper's sense because it made definite predictions that could be tested and ultimately falsified by observations.

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.