Big bang Definition and 916 Threads

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.

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  1. thegroundhog

    I Big Bang: Size & Matter of Universe Explained

    I've read that before the big bang all the matter in the universe was contained within an impossibly small space. How can you have matter in a smaller space than if all the space was squeezed out of an atom (or probability cloud if you want to be pedantic). Also, how does it fit it with Pauli's...
  2. K

    B Is the Big Bang only about the observable Universe?

    I was watching a video where Lawrence Krauss describes the big bang in terms of the observable universe. He says regions outside the observable universe need not have come from the big bang. Starts At minute 3.
  3. S

    I Wheeler's Mutability principle and multiple universes?

    Physicist John A Wheeler proposed the "Principle of mutability" which said that it could be the case that the universe would eventually shrink in a "Big Crunch" and the be re-born in another Big Bang. He proposed that the laws of physics (even the considered most fundamental ones) would change...
  4. bland

    I Does 'many worlds', imply worlds before the Big Bang?

    I'm at this point because a whole bunch of audio books I've been indulging in all seem to be converging on Many Worlds, and this has been given extra authority now because Sean Carroll appears to be a convert. I used to wonder if this was actual physics or metaphysics, and I've given up asking...
  5. S

    A Hartle-Hawking sum over all possible metrics?

    Physicists Stephen W Hawking and James B Hartle 1 proposed that the universe, in its origins, had no boundary conditions both in space and time. To do that, they proposed a sum over all compact euclidean compact metrics. I have heard that they only considered these metrics in order to simplify...
  6. I

    I Big Bang singularity: can we say anything about its size?

    The Big Bang is sometimes described as started from a singularity, which I have interpreted as meaning that its characteristics are undefineḍ. If that is the case, can we not even say that the Universe as a singularity was still infinite? Otherwise we are implying that the singularity was...
  7. kolleamm

    B Possibility of Another Big Bang?

    I see all of these videos and ideas on how it appears that the universe will die out with a big freeze since all of the objects are becoming further and further apart and entropy is increasing. Given a very large amount of time practically everything will be too spread out for any star...
  8. J

    B Exploring Big Bang Energy Density: Modern Particle Accelerator Achievements

    How many nanoseconds after the Big Bang was its energy density that achievable in modern particle accelerators?
  9. spacecapitalist

    B I don't understand the evidence or possibility of the Big Bang

    I don't understand how observations of the universe and theories behind the cosmos support the Big Bang Theory. For example, the microwave background could be explained through different mechanisms in space. Couldn't the red shift in galaxies be explained by something that occurred in the...
  10. SteadyStater

    I DDO 68: A Young Galaxy Supporting the Steady State Theory

    Young Galaxy Comes to the Rescue of an Old Theory The Steady State Theory of the universe has taken on a new lease of life with the discovery in 2014 of galaxy DDO 68, a dwarf galaxy 39 million light years away which, based on its structure, appearance and composition, appears to be relatively...
  11. S

    A According to Wilczek, how does quantum mechanics arise?

    According to Nobel laureate Frank Wilczek, the universe emerges from a Grid. This was proposed in his book "The Lightness of Being: Mass, Ether, and the Unification of Forces". He also likes the idea that the universe emerged from a state of "nothingness" (or rather, a quantum vacuum) where...
  12. curious222

    I Uncovering the Mystery: What Existed Before the Big Bang?

    what was it before the Big Bang?can you count one by one?
  13. A

    B Lithium problem in Big Bang nucleosynthesis?

    I frequently read of the problem that the measured primordial abundance of lithium does not match the amount expected by Big Bang nucleosynthesis theory. However, I see also graphs like these which seem to suggest that everything is as expected. Is this a contradiction or am I misreading the...
  14. Moon Shine

    B Why The Big Bang banged and didn’t collapsed into a black hole?

    Summary: The Big Band question. Why don’t we live in a black hole? Or do we? That actually might be a stupid question... so don’t hesitate to tell me that. If all mass of our universe was squeezed into something incredible small (compared the universe size) like maybe a tennis ball or maybe...
  15. P

    B Why do we assume the big bang created matter/antimatter?

    What if pure energy doesn't create matter/antimatter pairs, but entangled matter/matter-wave pairs? Duality is then literally two separate entities. When something becomes observed, the matter-wave becomes one with the particle it "represents". I'd say that would give a galaxy the extra mass...
  16. S

    Does Michio Kaku agree with Lawrence Krauss' concept of nothingness?

    Michio Kaku and Lawrence Krauss are both well-renowned physicists who propose that the universe (or universes) was generated out of nothing. Krauss, in his book "A Universe from Nothing" argued that the universe was probably created by a primordial "nothingness" with no space and time and...
  17. M

    I Is this explanation of "space itself expanding" correct?

    Hi, I always used to struggle with the concept of "space itself expanding" (didn't Einstein say that the aether did not exist?) until one day an idea struck me that seemed to explain it all, without any need for complicated math. After talking about it with others, I got some great feedback...
  18. Cerenkov

    B Questions about the Timeline of the Big Bang

    Hello. I'm trying to obtain a better understanding of the earliest epochs of the universe's evolution and have been looking here... https://www.physicsoftheuniverse.com/topics_bigbang_timeline.html https://en.wikipedia.org/wiki/Chronology_of_the_universe...
  19. W

    B Early Predictions of Hot Big Bang CMB: Gamov & Alpher

    As I understand it the fact the COBE measured the CMB to be a perfect black body implies strong evidence for the hot big bang. However, I am wondering what was the earliest prediction that this must be so from big bang cosmology? Does it go all the way back to Gamov and Alpher? is it older ...
  20. CynicusRex

    Can the big bang be compared to how video games start?

    If I understand correctly, when we interpret our data about the universe it seems the big bang came from nothing and threw out everything. Is it reasonable to compare this to a video game? Games also start from nothing and have suddenly loaded everything. If the game's AI was able to analyze...
  21. R

    I Is the Big Bang a White Hole? Exploring Possibilities

    We know that black holes exist in the universe, but white holes don't, as far as we know, Although white holes are not an impossibility in GR. Is it reasonable to ask if the big bang singularity is in fact a white hole, and is the only white hole in the Universe? Is the place where everything...
  22. S

    A Would Wheeler's oscillatory universe model create different laws?

    According to physicist John Wheeler, the universe is part of a sequence of cycles of Big Bangs and Big Crunches, called cyclic or oscillatory universe model (https://en.m.wikipedia.org/wiki/Multiverse (Mentioned in "Classification schemes") According to this author, in each cycle, the laws of...
  23. H

    B Rate of the expansion of the Universe and the Big Bang

    Disclaimer: I am parroting the information in this from articles that I've read. This post is to try to get a better understanding of what they are talking about and if any of it is relevant. I came across an article regarding the Big Bang while looking into the current rate of universe...
  24. L

    B When could life theoretically exist in any star system after the Big Bang?

    Theoretically how many billions of years after the Big Bang when life could theoretically exist in any star system? I am thinking how old they are now. And how big the accelerator they had built to probe the Planck scale. Couldn't very advanced civilization created solar system size...
  25. Sophrosyne

    B The Hubble deep field photos and the edge of the universe

    The Hubble telescope was able to capture images of the edges of our visible universe in its deep space photos. These were among its most breathtaking pictures. They show galaxies from about 14 billion light years away, as well as in the past, from the very beginning of time and space in our...
  26. Ken Lehn

    B Is Dark Energy Born at the Big Bang or Continually Created?

    Was all dark energy "born" at the moment of the Big Bang? Or does it "spring" into existence continually?
  27. F

    I Did Universal Physical Constants Exist at the Big Bang?

    Were the universal physical constants already in place at the instant of the BB? Things like Planck's constant, the speed of light, the various mass of particles, the various force values. Was it possible that the early universe ( the first couple of billionths of a second or so) existed without...
  28. S

    I Will the Big Rip basically be the Big Bang for the next universe?

    I was reading that the Big Rip will cause the whole universe to go singular, which sounds to me like another Big Bang. I was reading up on the Big Rip at Wikipedia, where it says that the observable universe is getting smaller, which makes no sense since the universe is expanding. :oldconfused:
  29. CHOP

    I Expanding universe needs a big bang?

    i have read that it is generally thought to be a consequence of the big bang (so, matter in motion) + something (dark energy) making that matter accelerate. why is the big bang needed in it? can't you just have acceleration? by the way, i am not sure what is intended by 'prefix' beside the...
  30. G

    B 83 quasars right up against the Event Horizon

    A few years ago I became intrigued by articles reporting the discovery of stars very close to the purported Big Bang; 400 million years seems an awful short time for a star to evolve. Then more recently the discovery of 2nd generation - hydrogen, carbon stars - in the same proximity, supposedly...
  31. Brunolem33

    B Questions regarding energy in the universe

    As I am watching the current season of How the Universe Works, I am a bit confused when listening to physicists talking about energy as if it was a thing. The way I understand it, energy doesn't exist by itself, but is rather the result of interactions involving matter. Energy is released...
  32. Michaela SJ

    I Big Bang Confusion: Exploring the Singularity

    (I am not a physicist - so, please be gentle :redface:) I was watching a program last night on the SCI channel, Did the Big Bang Really Happen? and they were describing the 'Singularity' as being this super hot very dense and infinitely small thing. And then when it went through the 'inflation'...
  33. O

    Newton's law of conservation as it applies to the big bang

    I had a thought the other day and I am looking for someone to tell me why it does not work. In consideration of energy be neither created nor destroyed, to me this would say there is not enough energy to continue expanding the universe. I also make the conjecture the gravity never stop...
  34. Marcus Gross

    I Supermassive singularity the cause of the Big Bang?

    OK so, I was wondering could the reason that our universe was in a hot dense state prior the the Big Bang Be because of it was actually a huge singularity that had no more mass to swallow up? And what caused this is that a type of matter or subatomic particle interacted with a different...
  35. J

    I Relativistic Reference Frames and the Big Bang?

    Peeling this out into its own thread for clarity: How is time dilation of extreme reference frames (photons, black holes, intergalactic space-time) taken into account in Big Bang cosmology? Since from the POV of a singularity or a photon, their clocks have effectively stopped and any lower...
  36. 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...
  37. F

    I Time Before Big Bang: Relational Dynamics & Singularities

    I have stumbled upon this article, which sounds a bit too fantastic to me. For one, because I can't imagine others haven't tried this before, and secondly: Will there be any chance to link this with actual observations which are suited to distinguish these solutions from more common ones...
  38. RandyD123

    B Big Bang Theory: If There's No Center, How Is Universe Infinite?

    The "big bang" suggests that everything came from a single point. If this is true that how can there be no center? And if everywhere is the center, then the universe by definition has to be infinite. And if the universe in infinite, then how did it become that way?
  39. Andy_K

    B Expansion or Attraction: What's Driving Our Universe?

    First of all, sorry for my naive question here which likely doesn't make sense. The universe is currently expanding with galaxies receding from each other at increasingly faster pace. Is it possible that the universe is a closed hypersphere system, where galaxies are actually not actively...
  40. Green dwarf

    B Was the universe is infinitely large at the big bang?

    My understanding is that the universe seems quite likely to be flat, and therefore infinite. Following an infinitely large object back in time to the big bang, it would never become finite. (However many times you divide infinity by 2, it is still infinity.) We tend to picture the big bang as...
  41. 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.
  42. nomadreid

    I Infinite range of E-M field vs finite age of particles

    It is said (hopefully no need to give references for such a common statement) that the electromagnetic field of a given charged particle is infinite in range (albeit converging to zero as the distance goes to infinity). However, given that charged particles apparently did not exist at the...
  43. Cerenkov

    B Standard Big Bang model vs Inflationary model

    Hello. I have some questions concerning the Standard Hot Big Bang model versus the Inflationary model. I've read that the Standard model cannot solve the Horizon and Flatness problems but Inflationary cosmology can. Firstly, is this so? Any replies that are pitched at my basic level of...
  44. Ebanflo

    I Is any attention being given to Conformal Cyclic Cosmology?

    Conformal Cyclic Cosmology, or CCC, is a hypothesis put forward by Roger Penrose in the early 2000s. My understanding of physics is lacking so my explanation will not be that clear, but I will summarize it here. Essentially, the existence of a previous spacetime, or "aeon," is postulated. This...
  45. Inani Schroedinger

    I Is the expansion actually accelerating? Or does it just appear so?

    I pulled this quote from an article on the Hubble Constant: "...for example, if the Hubble Constant was determined to be 50 km/s/Mpc, a galaxy at 10 Mpc, would have a redshift corresponding to a radial velocity of 500 km/s." In this illustration provided from the article, if this was the...
  46. O

    I Creation of matter in the big bang

    Hi, http://curious.astro.cornell.edu/about-us/101-the-universe/cosmology-and-the-big-bang/general-questions/570-where-did-the-matter-in-the-universe-come-from-intermediate The website given above says that the matter was created via pair production process (like electron anti-electron...
  47. rumborak

    I If all of spacetime was created with the Big Bang....

    ...why do people like Stephen Hawking talk about things/events "before" the Big Bang? If time (as part of spacetime) was created with this event, it also marks the point in time that had no "before", doesn't it?
  48. C

    I Time Since Big Bang: One Moment Everywhere?

    Is the time since the Big Bang the same for every point in our universe? If so, does that imply there really is a "present" moment everywhere and not just in my immediate locality?
  49. C

    B Was the Big Bang simply "Distant Traffic"?

    We keep hearing that "It all started with the Big Bang" and how "Everything was compressed into an infinitely small dot" and suddenly it expanded. Personally, I've wondered if this is more of a misinterpretation of distance, just as the headlights of heavy traffic on the highway looks like a...
  50. Islam Hassan

    I Big Bang Singularity vs Black Hole Singularities

    Is there a fundamental difference between the (speculative) understanding of a singularity arising from the creation of a black hole and the singularity which we think may have been at the origin of the Big Bang? Noteably, would there be two basic theoretical types of singularities...
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