What is Big bang theory: Definition and 92 Discussions

The Big Bang theory is the prevailing cosmological model explaining the existence of the observable universe from the earliest known periods through its subsequent large-scale evolution. The model describes how the universe expanded from an initial state of high density and temperature, and offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure.
Crucially, the theory is compatible with Hubble–Lemaître law — the observation that the farther away galaxies are, the faster they are moving away from Earth. Extrapolating this cosmic expansion backwards in time using the known laws of physics, the theory describes an increasingly concentrated cosmos preceded by a singularity in which space and time lose meaning (typically named "the Big Bang singularity"). Detailed measurements of the expansion rate of the universe place the Big Bang singularity at around 13.8 billion years ago, which is thus considered the age of the universe.After its initial expansion, an event that is by itself often called "the Big Bang", the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms. Giant clouds of these primordial elements – mostly hydrogen, with some helium and lithium – later coalesced through gravity, forming early stars and galaxies, the descendants of which are visible today. Besides these primordial building materials, astronomers observe the gravitational effects of an unknown dark matter surrounding galaxies. Most of the gravitational potential in the universe seems to be in this form, and the Big Bang theory and various observations indicate that this excess gravitational potential is not created by baryonic matter, such as normal atoms. Measurements of the redshifts of supernovae indicate that the expansion of the universe is accelerating, an observation attributed to dark energy's existence.Georges Lemaître first noted in 1927 that an expanding universe could be traced back in time to an originating single point, which he called the "primeval atom". Edwin Hubble confirmed through analysis of galactic redshifts in 1929 that galaxies are indeed drifting apart; this is important observational evidence for an expanding universe. For several decades, the scientific community was divided between supporters of the Big Bang and the rival steady-state model which both offered explanations for the observed expansion, but the steady-state model stipulated an eternal universe in contrast to the Big Bang's finite age. In 1964, the CMB was discovered, which convinced many cosmologists that the steady-state theory was falsified, since, unlike the steady-state theory, the hot Big Bang predicted a uniform background radiation throughout the universe caused by the high temperatures and densities in the distant past. A wide range of empirical evidence strongly favors the Big Bang, which is now essentially universally accepted.

View More On Wikipedia.org
  1. J

    B Expanding Universe -- What is it expanding into?

    I believe in the Big Bang but I struggle with something. If the Big Bang happened and universe is expanding there has to be something (or really nothing) there for the universe to be expanding into. Any thoughts?
  2. ChrisVer

    A An article on Big Bang theory contradictions

    Hi all, I was reading this article https://asiatimes.com/2020/11/the-big-bang-never-happened-but-fusion-will/ And I got somewhat confused. As most I've been taught that BB has succeeded in giving most of the cosmological predictions that we observe [nucleosynthesis, formation of galaxies, cmb...
  3. LCSphysicist

    I Book to study the big bang theory

    Could you recommend a book to study the big bang theory and the background necessary, mainly in math, to understand the theory rigorously?
  4. T

    B Algebraic Topology in the tv show The Big Bang Theory

    in the tv show "The Big Bang Theory", Sheldon wrote a book called "A proof the algebraic topology can never have a non self-contradictory set of abelian groups". Is this just a random set of words that is meant to sound smart but in reality means nothing or is it accurate? If it is, what does it...
  5. J

    I CMB results cause the contradiction of big bang theory

    - The wavelength of light doesn't change at all in the galaxies because the space of the galaxies doesn't expand. - The wavelength of light should be different when it passes through the galaxy or not. However, this is contradictory to the observed result. So, the big bang theory is wrong.
  6. Maha odeh

    A This is the most active place in the universe

    According to Source: They discover a mega cluster of 14 galaxies that originated only 1400 years after the Big Bang This is the most active place in this universe
  7. DAirey

    I How did time move forward during the Big Bang?

    As I understand it, time runs backwards inside a black hole. If the universe were far denser than a black hole when the universe was a fraction of a second old, then how did physical processes ever move forward? That is, how can a clock advance in something as dense as the initial universe?
  8. K

    The Big Bang: Exploding the Myth of a Center in Space and Time

    I am wondering, if the big bang was an explosion how can it be that all of the space and time was created simultaneous. Because an explosion have a center, but everywhere is the center of the universe.
  9. I

    B Big Bang theory and the known universe

    I just want to verify from physicists whether what I have read in this article is true: http://www.astro.ucla.edu/~wright/infpoint.html It says: The Universe was not concentrated into a point at the time of the Big Bang. But the observable Universe was concentrated into a point
  10. arivero

    Exploring the Scientific Accuracy of Whiteboards in The Big Bang Theory

    Any pointers about where to get information and perhaps pictures of the different whiteboards shown in Big Bang Theory? I am particularly interested on the season where Sheldon abandons string theory; the boards for this chapter (155, season 7 ep 20, aired 10th April 2014) seem to show some...
  11. P

    B Are all galaxies moving away from the Milky Way?

    Once again I am reading and trying to understand more about the different theories of the beginning of time/space. I don't know why I never thought about this, but they say that galaxies are moving further and further away. One day we will not be able to see them because they moved so far. My...
  12. Robin04

    I Time translation symmetry and the Big Bang

    Hi, As I know we now think that time translation is not a symmetry of spacetime because of the Big Bang, so we cannot say that our physical laws are applicable at every point in time. But then isn't the developing of the Big Bang theory against this asymmetry?
  13. Bran

    B Book recommendations for Big Bang Model?

    A recent discussion at the Expanding from and eventually to a singularity thread has been both interesting and informative, and it has shown me very clearly that I would benefit from a few good books, rather than the piecemeal approach I've been taking to understanding singularities and the Big...
  14. E

    Light beams, from the present to the time of the big bang

    Regarding expansion, from the present to the past: Do light beams (generally) converge to a single point, in the remote past, as geometry and matter was also condensed to a single point, prior to the big bang? Thank you.
  15. vinicius0197

    What does the big bang theory really tells us?

    I know there is a lot of misconception amongst the general public involving the big bang theory. Most people outside the scientific community still believe that the big bang theory says that the all the universe - and not just the observable one - started from a single point, and that the...
  16. gleem

    The Big Bang Theory a Fairy Tale? So says presidential candidate Ben Carson....

    So says Ben Carson. an entertaining commentary on His beiefs http://www.newyorker.com/news/news-desk/ben-carsons-scientific-ignorance?intcid=mod-most-popular more authoritative critique While He seems to have a live and let live philosophy i.e. I believe what I want to and you believe what...
  17. yazanhomsi

    The Inflationary and The Big Bang Theory

    Hello everyone, My question is: The big bang model proposes that the rate at which the universe is expanding is now decelerating. The inflationary theory proposes that the speed of expansion and separation started out slow and now it is accelerating. But as we know, recently it has been found...
  18. Comfort_Cube

    Is the Big Bang Theory the end of time, not beginning?

    I am by no means familiar with anything in quantum physics, so bear with me. This recent experiment that proved that future events can affect the past for an atom got me thinking, does that mean that, the timeline of atoms is the opposite of ours, and that the end of time for them is what we...
  19. T

    Inside the big bang were their other sub big bangs?

    As the question says. Sorry if it seems like a dum question!

    Big Bang Theory Explained: Is It Disproved?

    I just read an article saying that scientists disproved The Big Bang Theory. Is this true? and please run me through the whole "big bang theory" in brief as I'm no expert but just a school student.
  21. RandyD123

    Is the "Big Bang Theory" is on it's last breath?

    My guess is that the "Big Bang" theory is on it's way out and that it's only a matter of time before we realize that there is so much more we don't know than what we think we know...
  22. H

    What new theories are being proposed to explain the beginning of the universe?

    I was watching the news the other day and saw an article about scientist rethinking on the big bang. The article stated that some scientist believe that there had be something else that occurred for everything to evolve as far as it has in the amount of time since the so called big bang. Can...
  23. adoion

    Explaining the Big Bang: The Science Behind the Universe's Rapid Expansion

    hi, 1. radiation travels faster than matter. 2. our Earth was formed much after the big bang. The big bang goes like this. At some point in time and in some point in space (witch we cannot determent so we just leave the location open and say it could have happened anywhere) all the matter...
  24. F

    Theories on the beginning of the universe before the Big Bang Theory

    Hello everybody, I'm doing a little research for an Astrophysics course and I am supposed to talk about some older theories that have been developed to try to explain the beginning of the universe before the big bang theory became widely accepted. Sadly, when I look for them, most of what I...
  25. B

    Question about Big Bang Theory

    Hello Physicists First time poster. To give you some background I'm an electrical engineer so i have some basic understanding of physics up through relativity/quantum. I had a thought just occur to me that isn't very easy to google an answer for so i thought I'd come to the experts here. my...
  26. MarkFL

    MHB Season premiere of "The Big Bang Theory" tonight

    I understand that Penny and Sheldon have become close while Leonard has been at sea...something strange happens between Howard and his mother...Raj is still lamenting the fact that his neurotic girlfriend is gone... The season premiere airs at 8 pm ET on CBS, and the second episode of the...
  27. Q

    What evidence supports the big bang theory?

    off the top of my head: - isotropic microwave radiation corresponding to 3.73K blackbody curve - hubble's law - red shift of galaxies - 3:1 ratio between hydrogen and helium, and the relative abundance of them is there any more? and also, can someone explain the hydrogen-helium ratio thing...
  28. B

    A couple of questions about The Big Bang Theory

    I understand the concept used here, but am unsure about how scientists can be so sure of the actual age of our universe. They explain it by saying it's like pressing rewind, based on the speed that galaxies are moving away from our own, but I don't understand how you can press rewind to find...
  29. V

    Flat universe and big bang theory

    Hello everybody! This is my first post! I was wondering about the fact that we have measure our universe to be flat very accurately. This means that it is also infinite and if it is infinite now it was infinite from the beginning! This means that at bb the time collapses but not the space...
  30. J

    If the universe is infinite, then the big bang theory can't be correct

    Is this true? Because if it were infinite, how would it start at a small singularity? I mean it didn't start out at a finite size then grow to infinity right?
  31. V

    Universe older than thought? Or big bang theory wrong?

    It is thought that the universe is roughly 14 billion years old (soon) and that all matter came from a singularity (big bang). But even if we assume that all matter moved at the speed of light at some point, there simply wasnt enough time for the matter to spread over the area it is today in...
  32. Low-Q

    Big Bang theory vs. the universe as we know it

    I have a question you might have a good answer to. I hear astronomers keep saying that the universe as we know it was created by a big bang. One single point that exploded. If every known matter was flying off from the same point, how can it happen that there are stars, meteors, planets...
  33. MarkFL

    MHB For viewers of "The Big Bang Theory"....

    With which character do you identify most closely? For me it is Leonard, while I do have some of Sheldon's traits, I am not nearly as eccentric (or asexual (Tmi)) as he is.
  34. Mohamad&Issa

    Big Bang Theory: Force & Surface Questions

    Hi, The theory about big ban says that there were high temp. and high pressure. But pressure=force/surface I want to ask about the the force. Force of what? Is it the force of gravity? And is the surface for the atoms? Thanks.
  35. T

    Does the big bang theory conflict with the law of conservation?

    Perhaps I misunderstand the big bang theory but doesn't it basically hold that nothing existed prior to the big bang? If there truly was no energy or mass prior to the big bang then doesn't that conflict with the law of conservation of mass and energy?
  36. S

    Need Big Bang Theory Evidence for a school debate.

    Need this for a school project ASAP. I am looking for information that prooves parts of the the big bang theory were real. If possible I will need sources for this. I am giving a debate on wheather or not it is real. I am the pro side. Help much appreciated, thanks.
  37. J

    How does the Big Bang Theory explain the creation of matter from energy?

    How does the BB theory allow for the creation of matter. Bt this I mean the sub atomic particles that make up atoms i.e. the quarks and electrons. From what I have read it seems to assume that they already pre-existed and condensed out of the fireball to form atoms.
  38. K

    Exploring the Origins of the Big Bang Theory

    In school we are talking about the big bang, and it made me think. What if the cause of the bang was from a group of galaxies before us, very similar to us, and it was expanding just like our, but then we hit a "border", which caused a reverse action. Making that universe compact together and...
  39. M

    How fringe are alternatives to the Big Bang Theory?

    To my understanding, The Big Bang Theory (BBT) is considered the standard, mainstream theory explaining the origin of the universe. I know that there are alternative theories, and my question is, how discredited, fringe, or false are these theories considered, if at all? Alternatively, how...
  40. F

    What evidence supports the validity of the Big Bang theory?

    I think Big Bang theory is valid because of Inflation theory, it states that universe expanded faster than a light(right?) and that theory can solve the problems that Big Bang had: the Flatness and the Horizon problem. Another reason is Cosmic Microwave Background Radiation, which is first...
  41. Vorde

    Big Bang Theory and Shape of the Universe

    Is the big bang (referring to the well-established theory of post-Planck time evolution) compatible with any model of a finite universe that isn't spherical in topology? It seems to me that the big bang theory requires that the universe be finite in volume and the only way that seems feasible...
  42. J

    Exploring the Wonders of Science: The Big Bang Theory

    I apologize upfront due to my weak knowledge on the magnificent science. What i am studying now compared to the cutting edge of science is like a huge giant compared to a small little ant. Recently watched the great video of "through the wormhole", realized that dark energy is expanding the...
  43. maverick_starstrider

    In Big Bang Theory (the show) what are their jobs?Serious

    In "Big Bang Theory" (the show) what are their jobs?Serious Seriously, they're clearly not post-docs and they're clearly not professors. What job is there for a physicist at a university beyond that?
  44. E

    Watch Family Guy: The Big Bang Theory

    Just wanted to say the new Family Guy episode is brilliant! Episode is called The Big Bang Theory, even if you don't like family guy this episode is going to become a classic for anyone even remotely bothered about science. Watch It! Chris
  45. M

    12 year old savant provides possible debunking of Big Bang theory.

    Source: http://www.indystar.com/article/20110320/LOCAL01/103200369 http://www.dailymail.co.uk/news/article-1369595/Jacob-Barnett-12-higher-IQ-Einstein-develops-theory-relativity.html Thoughts?
  46. zonde

    Exploring Misconceptions of the Big Bang Theory

    I read this in article "Misconceptions about the big bang" that was mentioned in another thread: "For example, when a star explodes as a supernova, it brightens and then dims — a process that takes about two weeks for the type of supernova that astronomers have been using to map out space...
  47. E

    Where Can I Find Reliable Scientific Quotes for My Big Bang Theory Coursework?

    I am doing my science coursework on the Big Bang Theory. Do you know any reliable websites where i can use quotes from scientists to help back up the information i have gathered? Thankyou
  48. P

    The Big Bang Theory: Was There No Space?

    Big bang suggests that there was only a concentrated mass.was there no space?If there was no space where did it come from?[i mean what makes space?].time also started after big bang.how did it start? Don't u guys think there's somethin missing in this theory?
  49. C

    Is Everything in the Universe Made of Wavelengths?

    Hi guys, just a quick post about the big bang theory and other possible theories. I am by far no scientist, nor do I work in a scientific environment. I am simply amazed by the creation of the universe and sadly think about it on a regular basis. One thing I could not understand was how all the...
  50. J

    Questioning the Big Bang Theory

    I am having problem with understanding the concept of big bang theory. Actually I don't believe in the theory. How can we say that this universe was formed because of a big explosion? We can't answer the question what happened before that.