The universe as we know it began around 13.75 billion years ago with an event known as the Big Bang. This monumental event marked the creation of space, time, and all the matter that would eventually form the cosmos we see today. The Big Bang theory is the leading explanation for the origin of the universe, although it doesn’t answer every question, such as why it happened in the first place. Instead of asking “why,” scientists focus on “how” the universe came to be.
Scientists, especially physicists and biologists, are fascinated by the origins of life and the universe. They trace back the history of the universe to understand how it evolved into its current state. Recent measurements have precisely dated the universe to be 13.75 billion years old. However, questions about what existed before the Big Bang remain unanswered. What we do know is that the universe was once incredibly hot, dense, and compact, possibly smaller than an atom.
Since the Big Bang, the universe has been expanding and cooling. This expansion allowed complex structures like DNA, planets, stars, and eventually life to form. Scientists study the universe by observing the stars and using advanced machines to recreate conditions similar to those right after the Big Bang.
Two major discoveries support the Big Bang theory. In the 1920s, Edwin Hubble discovered that galaxies are moving away from each other, with their speed proportional to their distance from Earth. This became known as Hubble’s Law. In the 1960s, the discovery of cosmic microwave background radiation provided further evidence, as it is the residual heat from the Big Bang.
When scientists say the universe is expanding, they mean that the space between galaxies is increasing. Galaxies themselves aren’t growing larger; rather, they are moving further apart as space itself expands. This expansion doesn’t mean the universe is growing into something else; instead, space-time itself is stretching.
Einstein’s theory of general relativity, formulated in 1915, remains the best framework for understanding space and time. By applying this theory, scientists can trace the universe’s expansion back to a point of infinite density and temperature, known as a singularity. This singularity represents the universe’s origin, where all matter was compressed into an infinitely small space.
Some theories suggest the existence of parallel universes, which might be as close as a millimeter away but remain undetectable due to the limitations of our senses and the forces that govern our universe. While this idea is speculative, it opens up fascinating possibilities for future research and experimentation.
While the concept of parallel universes remains largely theoretical, the Big Bang theory is well-supported by empirical evidence. The discovery of Hubble’s Law and cosmic microwave background radiation has solidified our understanding of the universe’s origins. Although the universe’s expansion is accelerating, the reasons behind this phenomenon are still being explored.
Thank you for engaging with this exploration of the universe’s beginnings. Stay curious and keep exploring the wonders of the cosmos!
Create a detailed timeline of the universe’s history starting from the Big Bang to the present day. Include major events such as the formation of the first atoms, stars, galaxies, and the solar system. Use visual aids like charts or infographics to enhance your presentation.
Participate in a debate discussing different theories about the origins of the universe. Divide into groups, with each group representing a different theory, such as the Big Bang, steady state, or multiverse theories. Present arguments and counterarguments based on scientific evidence.
Engage in a computer simulation activity that models the conditions of the universe shortly after the Big Bang. Analyze how changes in variables such as temperature and density affect the formation of matter and cosmic structures.
Conduct a research project on cosmic microwave background radiation. Investigate how it was discovered, what it tells us about the early universe, and its significance in supporting the Big Bang theory. Present your findings in a written report or presentation.
Study Einstein’s theory of general relativity and its implications for understanding the universe’s expansion. Work in groups to solve problems related to space-time curvature and gravitational effects. Present your solutions and discuss how they relate to the Big Bang.
**Sanitized Transcript:**
Let there be light. [Music] The moment where space, time, and everything else that came into existence, which would eventually give rise to the present-day cosmos, occurred some 13.75 billion years ago. The prevailing cosmological model explaining the existence of the observable universe from the earliest known periods is known as the Big Bang theory. It is one of the best theories we have in all of science, but of course, it doesn’t explain everything, like why the Big Bang happened in the first place. But maybe the question “why” is not a good question, as it presupposes the universe had a purpose. Perhaps a better question is “how.”
The question for scientists, particularly physicists and biologists interested in the fundamentals of life, is how it all came to be. The Earth is populated by so many wonderfully diverse organisms, and from a physicist’s perspective, you want to go back all the way to the beginning. This is a picture of the origin and evolution of the universe as we know it now.
We made a spectacularly precise measurement of the age of the universe quite recently. The current number is 13.75 billion years old. So, the picture is that 13.75 billion years ago, the universe began. Why? We don’t know. We don’t know the answer to questions such as what happened before the Big Bang. I get asked that a lot, and the answer is we don’t know. It’s current research, but we do know that the universe was extremely hot, dense, and small 13.75 billion years ago. In fact, everything we can see in the universe today was probably compressed into something smaller than an atom.
It’s a tremendous thought, but what we know is that the universe expanded and cooled ever since. As it cooled, complex things began to crystallize out. From that ball of energy 13.75 billion years ago, we get things like DNA, planets, stars, and people. How do you go about finding out? One way is to look up at the stars; the other way is to build machines that can explore the universe by recreating the conditions that were present close to the Big Bang.
The idea that the universe began as an unfathomably single point and then expanded to grow as large as it is today is truly mind-boggling. But that’s what the evidence strongly suggests happened. Just because something is unimaginable to us does not mean it can’t be reality. To quote Neil deGrasse Tyson, the universe is under no obligation to make sense to you.
Two major scientific discoveries provide strong support for the Big Bang theory: Hubble’s discovery in the 1920s of a relationship between a galaxy’s distance from Earth and its speed, and the discovery in the 1960s of cosmic microwave background radiation. When scientists talk about the expanding universe, they mean that it has been increasing in size ever since the Big Bang.
But what exactly is getting bigger? Galaxies, stars, and planets are getting bigger, but their size is controlled by the strength of the fundamental forces that hold atoms and subatomic particles together, which hasn’t changed. Instead, it’s the space between galaxies that’s increasing; they’re getting further apart as space itself expands. If that’s the case, one might wonder what the universe is expanding into.
The standard answer, as best we know at the moment, is that it doesn’t expand into anything because it’s space itself—and actually, space-time, if you talk to Einstein—that’s expanding. So, it’s not the right picture to think of the Big Bang in a pre-existing space. It seems that, as far as we know, space and time began at the Big Bang and have been stretching ever since.
Another related idea is where the Big Bang happened. You might think, “Well, we’re in this big box of the universe; did it happen over there or over there?” It happened everywhere because all the space was made at the Big Bang. So, the Big Bang happened everywhere; it’s very difficult to picture that.
The theory that deals with this, the underpinnings, is called Einstein’s theory of general relativity. He wrote it down in 1915, and it’s still our best theory of space and time, the theory upon which all these interesting and strange ideas rest. Extrapolation of the expansion of the universe backwards in time using general relativity yields an infinite density and temperature at a finite time in the past.
In physics, a singularity is an infinitely small space. Within this small space exists infinite gravity and density. In fact, gravity within a singularity is so great that not even light can escape from it. The Big Bang was the ultimate extreme; simply put, the entire universe was jammed into an infinitely small space, which gave way to infinite temperatures, density, and pressure.
As counterintuitive and strange as these ideas may sound, they have a firm theoretical framework based on our understanding of the laws of physics. Our natural instincts and senses have no ability to grasp infinite density, but there are even more bizarre and astonishing ideas than this. Our universe may not be unique; there could be parallel universes out there.
Imagine that we’re not in this three-dimensional space; just forget one of the dimensions. Imagine we lived on the surface of a sheet of paper, and the forces of nature, particularly light, traveled on the sheet. Then there’s another force called the nuclear force that sticks atomic nuclei together. Imagine that only works on the sheet as well.
What would happen if there were another sheet, another universe, just floating a millimeter away? You wouldn’t see it because light is confined to your sheet; you wouldn’t feel it because the forces don’t come off the sheet. It could be there. If that’s true, we can try to do experiments to see how we might detect it, but it’s not really well known.
There are some signatures of these extra dimensions that you can see at the Large Hadron Collider at CERN. It’s very speculative stuff. I find it remarkable that there’s another universe a millimeter away from your head in a big sheet stretching out infinitely in all directions, and you just don’t perceive it because the forces that hold us together don’t travel from one sheet to the next.
Of course, it would be extremely difficult, if not impossible, to prove the existence of other universes if they do not interact with our own universe. However, if a theory comes along that is extremely accurate in describing how our own universe operates and also predicts the existence of other parallel universes, it would be reasonable to infer their existence despite the lack of physical data.
To a layperson, it may seem that physical cosmology is producing all sorts of stories without any backing of actual data, but that could not be farther from the truth. For example, the Big Bang theory, although dismissed by Einstein in the 1920s when it was first proposed, later gathered firm ground.
Early in the 20th century, the universe was thought to be static, always the same size, neither expanding nor contracting. But in 1924, astronomer Edwin Hubble used a technique to measure distances to remote objects in the sky. He discovered that the speed at which astronomical objects move apart is proportional to their distance from each other. In other words, the farther away objects are from Earth, the faster they are moving away from us. This became known as Hubble’s Law.
Hubble’s Law allowed astronomers to calculate how long ago galaxies started moving apart, which provides an estimate of when the Big Bang occurred and how old the universe is. Then, in 1964, the cosmic microwave background radiation was discovered, which is the leftover heat radiation from the Big Bang. So, we had irrefutable physical evidence to suggest the Big Bang happened.
Since then, theoretical physicists have described in great detail the evolution of the universe from its very first moments after the Big Bang. It was also found that the expansion of our universe is accelerating, but the cause of it remains unknown, and we will explore the possible answers in another video.
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Big Bang – The theoretical event marking the origin of the universe, characterized by an initial singularity from which space, time, and matter emerged. – According to the Big Bang theory, the universe began approximately 13.8 billion years ago from an extremely hot and dense state.
Universe – The totality of space, time, matter, and energy that exists, including all galaxies, stars, and planets. – The study of the universe involves understanding its vast structure and the fundamental forces that govern it.
Expansion – The increase in distance between any two given gravitationally unbound parts of the universe over time. – The discovery of the universe’s expansion was a pivotal moment in cosmology, providing evidence for the Big Bang theory.
Galaxies – Massive systems consisting of stars, stellar remnants, interstellar gas, dust, and dark matter, bound together by gravity. – The Milky Way is one of billions of galaxies in the observable universe, each with its own unique properties and structures.
Evidence – Observable data or phenomena that support or refute a scientific theory or hypothesis. – The cosmic microwave background radiation serves as crucial evidence for the Big Bang theory.
Relativity – A fundamental theory in physics, formulated by Albert Einstein, describing the gravitational force as a curvature of spacetime caused by mass and energy. – Einstein’s theory of relativity revolutionized our understanding of space, time, and gravity.
Singularity – A point in space-time where density becomes infinite, such as the center of a black hole or the initial state of the universe in the Big Bang theory. – The concept of a singularity challenges our understanding of physics, as conventional laws break down under such extreme conditions.
Cosmic – Relating to the universe or cosmos, especially as distinct from Earth. – Cosmic phenomena, such as supernovae and black holes, provide insights into the life cycles of stars and the dynamics of galaxies.
Radiation – The emission or transmission of energy in the form of waves or particles through space or a material medium. – Cosmic microwave background radiation is a remnant from the early universe, providing a snapshot of its infancy.
Origins – The point or place where something begins, arises, or is derived, particularly in the context of the universe or celestial bodies. – Understanding the origins of the universe involves studying the conditions and processes that led to the formation of galaxies and stars.
