What is the Universe expanding into? Theory of Inflation & Standard Cosmological Model

Summary

This video from 'The World Of Science' explores the universe's expansion, comparing it to a balloon's inflation. It delves into Einstein's cosmological constant and Alan Guth's Inflation theory, explaining how a rapid expansion smoothed out the universe's temperature. The script also discusses the concept of 'Inflaton field' and its role in the universe's early stages, the discovery of the Higgs boson, and the mysterious Dark Energy accelerating the universe's expansion. It concludes with questions about the universe's infinite expansion and the possibility of multiple universes, inviting viewers to ponder and engage in the ongoing scientific quest for answers.

Takeaways

• 🌌 The universe is expanding, a concept that differs from other increasing phenomena as it involves the fabric of space-time itself.
• 📚 Einstein's field equations, which unite space and time, suggest that the universe could either expand or contract based on its density.
• 🔍 Russian physicist Alexander Freedman found that the universe could have two solutions: expanding or contracting.
• 💫 Einstein introduced the cosmological constant to counteract gravity and stabilize a static universe, but later called it his 'biggest blunder' after evidence of the universe's expansion was found.
• 🌀 Alan Guth's theory of Inflation proposes a rapid exponential expansion of the universe shortly after the Big Bang, explaining its vastness and uniformity.
• 🧩 The Inflaton field, a hypothetical scalar field, is suggested as the driving force behind cosmic inflation, creating negative pressure similar to dark energy.
• 🤔 The uniform temperature of the Cosmic Microwave Background (CMB) radiation is a mystery explained by the inflationary period allowing for thermal equilibrium across the universe.
• 🔬 The discovery of the Higgs boson in 2012 and its field's role in giving particles mass has led to speculations about its connection to the Inflaton field.
• 🌪 Observations in 1998 indicated that the universe's expansion is accelerating, attributed to the presence of dark energy.
• 🌌 The cosmological constant, once discarded by Einstein, is now considered a possible explanation for the universe's accelerated expansion.
• 🤷‍♂️ The question of what the universe is expanding into remains unanswered, with theories suggesting it could be infinite or part of a multiverse.

Q & A

What does the expansion of the universe imply according to the script?

The expansion of the universe refers to the ongoing increase in the scale of the universe's space-time fabric, which is not the same as any other increasing phenomenon and is often compared to the expansion of a balloon.

What was Einstein's initial belief about the universe's nature?

Einstein initially believed in a static universe, despite formulating the theory of relativity, and introduced the cosmological constant to stabilize the universe against gravitational collapse.

Why did Einstein later call the cosmological constant his 'biggest blunder'?

Einstein called it his 'biggest blunder' after Edwin Hubble's observations confirmed the universe's expansion, making the cosmological constant unnecessary for the explanation.

What is the significance of the Inflation theory proposed by Alan Guth in 1979?

The Inflation theory explains the vastness of the universe and the uniform temperature of the Cosmic Microwave Background (CMB) by proposing a rapid exponential expansion phase shortly after the Big Bang.

What is the role of the 'Inflaton field' in the context of the Inflation theory?

The Inflaton field is a hypothetical scalar field with a false vacuum state that contains a large amount of vacuum energy, creating a negative pressure that drives the rapid expansion of the universe during the inflationary phase.

How does the script relate the Higgs field to the Inflaton field?

The script suggests that there are proposals treating the Higgs field and the hypothetical Inflaton field as one and the same, originating at the Big Bang, driving the universe's expansion, and decaying to form standard particles and giving them mass.

What evidence did astrophysicist Saul Perlmutter and his colleagues provide in 1998?

They provided evidence that the universe is not only expanding but doing so at an accelerating rate, which led to the concept of Dark Energy.

What is Dark Energy and how is it related to Einstein's cosmological constant?

Dark Energy is a hypothetical form of energy that is believed to be causing the accelerated expansion of the universe. It is related to Einstein's cosmological constant as a possible explanation for this acceleration.

What is the current understanding of the contribution of Dark Energy to the universe's total energy?

According to the standard cosmological model and current measurements, Dark Energy contributes approximately 68% of the total energy in the present-day observable Universe.

What does the script suggest about the universe's expansion and its implications for its size?

The script suggests that the universe's expansion implies that space-time is changing, and while some theories propose a multiverse model with multiple bubble universes, the exact nature of what the universe is expanding into remains unknown.

How does the script encourage viewers to engage with the content?

The script encourages viewers to comment with their thoughts on the Big Bang and the universe's expansion, to give a thumbs up if they found the video helpful, and to share it with friends, as well as to subscribe for more content.

Outlines

00:00

🌌 The Expansion of the Universe and Einstein's Cosmological Constant

This paragraph delves into the concept of the universe's expansion, questioning its similarity to other increasing phenomena and whether it's akin to a balloon's expansion. It introduces Einstein's field equation, which describes space-time as a fabric influenced by matter, and the subsequent discovery by Alexander Freedman that the universe could either expand or contract based on its density. The narrative also touches on Einstein's struggle with the idea of a static universe and his introduction of the cosmological constant to counteract gravity and stabilize the universe. The concept of negative pressure from quantum field energy, which could be responsible for an anti-gravity effect, is also discussed. The paragraph concludes with Einstein's eventual rejection of the cosmological constant after Edwin Hubble's observations of the universe's expansion.

05:02

🚀 Inflation Theory, the Inflaton Field, and the Accelerating Universe

The second paragraph explores Alan Guth's theory of cosmic inflation, which posits a rapid exponential expansion of the universe shortly after the Big Bang, addressing questions about the universe's vastness and uniform temperature. This inflationary phase is said to have occurred 10^-32 seconds after the Big Bang, allowing for a brief period of connectedness and thermal equilibrium across the universe, resulting in the uniform temperature observed in the Cosmic Microwave Background (CMB) radiation. The 'Inflaton field' is introduced as a hypothetical scalar field responsible for this inflation, with a false vacuum state that creates negative pressure, driving the universe's expansion. The paragraph also discusses the decay of the Inflaton field into fundamental particles and draws a parallel with the Higgs field, which imparts mass to particles. Finally, it touches on the discovery of the accelerating expansion of the universe and the concept of 'Dark Energy,' which may be explained by Einstein's previously discarded cosmological constant. The current understanding suggests that dark energy constitutes 68% of the universe's total energy content, and the paragraph concludes with philosophical musings on the nature of the universe's expansion and the possibility of a multiverse as suggested by string theory.

Keywords

💡Universe Expansion

The term 'Universe Expansion' refers to the ongoing increase in the size of the universe. It is a central theme of the video, illustrating the idea that the universe is not static but is continuously growing. The script discusses the historical understanding of this phenomenon, from Einstein's field equations to the observational evidence provided by Edwin Hubble, which confirmed the universe's expansion.

💡General Relativity

General Relativity is Einstein's theory that describes gravity not as a force but as a curvature of spacetime caused by mass. In the script, it is mentioned as the framework within which the universe's expansion was initially conceptualized, with space and time being unified into a single entity that can be altered by the presence of matter.

💡Cosmological Constant

The 'Cosmological Constant' is a term introduced by Einstein in his field equations to represent a form of anti-gravity that would counteract the attractive force of gravity and maintain a stable universe. The script describes how Einstein later referred to it as his 'biggest blunder' after the discovery of the universe's expansion, but it has since been repurposed to explain the accelerated expansion due to dark energy.

💡Inflation Theory

The 'Inflation Theory' proposed by Alan Guth suggests a period of rapid expansion in the early universe, which solved several puzzles, including the uniformity of the cosmic microwave background (CMB) temperature. The script explains how this theory posits that the universe expanded exponentially in a very short time after the Big Bang, leading to a vast and homogenous cosmos.

💡Inflaton Field

The 'Inflaton Field' is a hypothetical scalar field that Alan Guth proposed to drive the inflation of the universe. It is characterized by a false vacuum state with a large amount of vacuum energy, which creates a negative pressure that pushes the universe outward. The script describes how this field decayed to produce the fundamental particles we know today.

💡Cosmic Microwave Background (CMB)

The 'Cosmic Microwave Background' (CMB) is the thermal radiation left over from the early universe, which has a uniform temperature of approximately 2.7K throughout the universe. The script uses the CMB to illustrate the uniformity of the universe's temperature before the inflationary phase and how it remains constant due to the rapid expansion.

💡Dark Energy

Dark Energy is a hypothetical form of energy that is believed to be responsible for the observed acceleration in the expansion of the universe. The script mentions that dark energy contributes a significant portion of the total energy in the observable universe and that it may be related to the cosmological constant.

💡Higgs Field

The 'Higgs Field' is a field of elementary particles throughout space that is responsible for giving particles mass. The script draws a parallel between the Higgs field and the Inflaton field, suggesting that they might be the same field that originated at the Big Bang, expanding the universe and giving particles mass.

💡Big Bang

The 'Big Bang' is the prevailing cosmological model for the beginning of the universe, suggesting a singularity from which space, time, and matter expanded. The script discusses the Big Bang as the starting point for the universe's expansion and the subsequent inflationary phase.

💡String Theory

String Theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. The script briefly mentions string theory in the context of a multiverse model, where multiple bubble universes could exist in a higher-dimensional hyperspace.

Highlights

The universe is expanding, a concept that differs from other increasing phenomena.

Einstein's field equation suggests space-time can be altered by the presence of matter.

Freedman's solution to the field equation revealed two possible universe states: expanding or contracting.

Einstein introduced the cosmological constant to counteract gravity and stabilize a static universe.

Einstein later abandoned the cosmological constant after Hubble's discovery of the universe's expansion.

Alan Guth's theory of Inflation explains the rapid exponential expansion of the universe shortly after the Big Bang.

The Inflation theory addresses the uniform temperature of the Cosmic Microwave Background (CMB) across the universe.

Guth proposed the 'Inflaton field' as a hypothetical scalar field responsible for the inflationary phase.

The concept of a 'false vacuum state' with high vacuum energy leading to negative pressure was introduced.

The decay of the Inflaton field post-inflation led to the creation of fundamental particles.

A connection between the Higgs field and the Inflaton field is proposed, suggesting a unified origin.

Evidence from 1998 suggests that the universe's expansion is accelerating, introducing the concept of Dark Energy.

Dark Energy is hypothesized to be the cause of the universe's accelerated expansion.

Einstein's cosmological constant is revisited as a possible explanation for Dark Energy.

Current measurements indicate Dark Energy contributes to 68% of the total energy in the observable Universe.

The question of what the universe is expanding into remains unanswered, with theories suggesting it could be infinite.

String theory presents a model with multiple bubble universes expanding into extra dimensions.

The video encourages viewers to stay curious and scientific while awaiting further evidence and discoveries.

Transcripts

You may have heard of the universe expanding. Is the expansion of the universe same

as any other increasing phenomenon? Is it really like balloon expanding? And if it is

expanding, what is it expanding into? Let’s try to understand it in this video. My name

is Mason and you are watching, The World Of Science!

Let’s dive back into history. Einstein gave the field equation that proposes that space

and time being one unified entity, its fabric can be changed due to the presence of

matter around it. When Russian physicist Alexander Freedman solved the equation, he

found out that the universe of general relativity will have two types of solutions, one

expanding and one contracting, depending upon the density of total material present in

the universe. But Einstein on other hand, was struggling with other problem related

to same phenomenon. He also believed in the static

nature of universe despite formulating Relativity that is the very antithesis

of classical mechanics. But if universe is static spherical ball of vastness and everything

is being pulled towards with force of gravity, wouldn't there be some point in future

that all matter fall eventually to the centre of

universe and universe will finally collapse. He was not willing to accept it, so he

introduced a new mathematical constant in the equation, the cosmological constant.

This constant denotes some kind of negative Gravity that will push the incoming

matter pulled down by positive gravity and thus stabilizing the universe. Space is

apparently filled with energy of quantum fields and this energy has a uniform negative

pressure. This negative pressure is responsible for this hypothetical anti-gravity. But in

Freedman’s solution there was no need of any constant and universe was already

expanding. Einstein later dropped this insertion and called it his “biggest blunder” after

Edwin Hubble observed the expansion of universe astronomically and derived a

mathematical relation for the same. Fast forward to 1979, physicist Alan Guth

proposed his most famous theory of Inflation. He was actually focussing on basic

questions related to cosmos such as why the universe is so vast. Another question

he was worried about was if the universe started with big bang and is expanding ever

since, no part of universe had ever been connected to each other yet every part has

same equilibrium temperature of 2.7K i.e. the temperature of Cosmic Microwave Background

(CMB) radiation around the universe. His study showed that the big bang

was followed by a period of rapid expansion in which the universe inflated exponentially

and this smears out the irregularities, forming a homogenous and vast

cosmos. The volume of universe expanded by a factor of 10^78, thus explaining

the vastness, and this inflationary phase was not instantly at the point of origin but

10^-32 seconds after the big bang. There was a

limited time period before this inflation started for every point in universe to have

certain time of connectedness and were thermally at equilibrium. As it expanded

during inflationary phases, the equilibrium remained and hence CMB is at uniform

temperature all over the universe. For inflation to happen, he proposed a new

hypothetical scalar field called “Inflaton field”. This hypothetical field has a false

vacuum state with a large amount of vacuum energy and this creates a negative

pressure similar to the cosmological constant of Einstein that will push the universe

outward. Every vacuum state corresponds to lowest possible energy present in that

particular point or region but as we know there is nothing called certainty at quantum

scale, so there always exist certain possibility of having some non-zero states in some

vacuum states and those regions which have non-zero potential energy are called false

vacuum state. Since vacuum always tends to zero, to minimise the energy present in

that region, space-time will expand. More there be the volume, less will be the density.

At the beginning, there was only inflaton field and as the universe expanded, this field

decayed to produce the fundamental particles we know today. If you have heard about

Higgs field, they have similar properties of being eternally present and at false vacuum

state. The particles interacting with the field gets Higgs field value which can be

interpreted as acquiring mass. Consequently, there are various proposals of treating

Higgs field and hypothetical Inflaton field as one and the same field that originated

at the big bang, then is expanding the universe,

further decaying to form standard particles and giving mass to them. Higgs was

just a hypothetical particle since 1964 until in 2012 it was physically discovered.

In 1998, astrophysicist Saul Perlmutter along with his colleagues provided evidence

that universe is not only expanding but expanding with an acceleration. But what is

causing this acceleration? Is there any extra energy present in the universe that is

pushing universe away? The solution proposed that there is some hidden energy and it

was named Dark Energy. Interesting thing is that, the same cosmological constant

Einstein first added and then removed, can now finally be used. Although universe is

expanding without the use of cosmological constant, this can be used to explain

accelerated push. So was Einstein right? Yes but not in the way he thought of using it.

Assuming that standard cosmological model is correct, the best current measurements

indicate that dark energy contributes 68% of the total energy in the present-day

observable Universe. But the question remains, if universe is expanding, what is it

expanding into? There is nothing in the universe that is expanding, neither you, nor me

and not even any heavenly bodies but it is the space-time framework of the universe

that is changing. Taking the balloon as an example, we are not outside the universe to

observe it expanding, we are inside it. This posits new problems like if universe is

expanding unto itself, then universe must be infinite and the answer for this is that

we don’t know as of now. Some theories do give

a solution like string theory which presents a model of cosmology containing multiple

bubble universes in the

hyperspace, so each universe can expand into the extra dimension available just like

cookies are baked in a microwave. This may be true but we don’t have evidences to

prove that. In science, lack of evidence doesn’t mean the absence of evidence. Let’s

hope in some time in future we get the answers until then we can keep wondering.

I hope you enjoyed this video. Comment below your thoughts about the Big Bang and

expansion of our Universe. If you found this video helpful, please leave a thumps up

and share this with your friends. Do check out other videos on our channel. Make sure

you subscribe The World Of Science for more such interesting videos. Until next time,

stay scientific!