Big Bang

The Big Bang theory is the prevailing cosmological model, that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in its present continuously expanding state.

According to the most recent measurements and observations, this original state existed approximately 13.8 billion years ago, which is considered the age of the Universe and the time the Big Bang occurred. After its initial expansion from a singularity, the Universe cooled sufficiently to allow energy to be converted into various subatomic particles.

Quotes arranged in chronological order

• These theories were based on the hypothesis that all the matter in the universe was created in one big bang at a particular time in the remote past.
  • Fred Hoyle, BBC radio broadcast, 1949. Reprinted in April 1949 in The Listener.

• The main efforts of investigators have been in papering over contradictions in the big bang theory, to build up an idea which has become ever more complex and cumbersome.
  • Fred Hoyle, The Intelligent Universe.

• I have little hesitation in saying that as a result a sickly pall now hangs over the big bang theory. As I have mentioned earlier, when a pattern of facts becomes set against a theory, experience shows that it rarely recovers.
  • Fred Hoyle, The Intelligent Universe, Page 186.

• In the beginning there was an explosion. Not an explosion like those familiar on earth, starting from a definite center and spreading out to engulf more and more of the circumambient air, but an explosion which occurred simultaneously everywhere, filling all space from the beginning, with every particle of matter rushing apart from every other particle. ‘All space’ in this context may mean either all of an infinite universe, or all of a finite universe which curves back on itself like the surface of a sphere. Neither possibility is easy to comprehend, but this will not get in our way; it matters hardly at all in the early universe whether space is finite or infinite. At about one-hundredth of a second, the earliest time about which we can speak with any confidence, the temperature of the universe was about a hundred thousand million (10¹¹) degrees Centigrade. This is much hotter than in the center of even the hottest star, so hot, in fact, that none of the components of ordinary matter, molecules, or atoms, or even the nuclei of atoms, could have held together. Instead, the matter rushing apart in this explosion consisted of various types of the so-called elementary particles, which are the subject of modern high­energy nuclear physics.
  • Steven Weinberg, The First Three Minutes: A Modern View of the Origin of the Universe (1977), p. 5

• This circumstance of an expanding universe is irritating.
  • Albert Einstein, quoted in "Have Astronomers" by Robert Jastrow, The New York Times (June 25, 1978)

• To admit such possibilities seems senseless to me.
  • Albert Einstein, quoted in "Have Astronomers" by Robert Jastrow, The New York Times (June 25, 1978)

• Bothers science because it clashes with scientific religion—the religion of cause and effect, the belief that every effect has a cause. Now we find that the biggest effect of all, the birth of the universe, violates this article of faith. . . . what came before the Big Bang is the most interesting question of all.
  • The director of the U.S. National Aeronautics and Space Administration’s Goddard Institute for Space Studies in 1979.^{[citation needed]}

• Ten or twenty billion years ago, something happened—the Big Bang, the event that began our universe. Why it happened is the greatest mystery... That it happened is reasonably clear. All the matter in the universe was concentrated at extremely high density—a kind of cosmic egg, reminiscent of the creation myths of many cultures—perhaps into a mathematical point with no dimensions at all.
  • Carl Sagan, Cosmos (1980)

• The discovery of the Big Bang and the recession of the galaxies came from a commonplace of nature called the Doppler effect. ...An object approaching us at very high velocities is perceive to have the color of its spectral lines blue-shifted. An object receding from us at very high velocities has its spectral lines red-shifted. ...Following a lead by the astronomer V. M. Slipher... Humason and Hubble found, to their amazement, that the spectra of all distant galaxies are red-shifted.
  • Carl Sagan, Cosmos (1980)

• The ideas that prove to be of lasting interest are likely to build on the framework of the now standard world picture, the hot big bang model of the expanding universe. The full extent and richness of this picture is not as well understood as I think it ought to be, even among those making some of the most stimulating contributions to the flow of ideas.
  • Phillip James Edwin Peebles, Principles of Physical Cosmology (1993) Preface

• Once we overcome our fear of being tiny, we find ourselves on the threshold of a vast and awesome Universe that utterly dwarfs—in time, in space, and in potential—the tidy anthropocentric proscenium of our ancestors. We gaze across billions of light-years of space to view the Universe shortly after the Big Bang, and plumb the fine structure of matter. We peer down into the core of our planet, and the blazing interior of our star. We read the genetic language in which is written the diverse skills and propensities of every being on Earth. We uncover hidden chapters in the record of our origins, and with some anguish better understand our nature and prospects. We invent and refine agriculture, without which almost all of us would starve to death. We create medicines and vaccines that save the lives of billions. We communicate at the speed of light, and whip around the Earth in an hour and a half. We have sent dozens of ships to more than seventy worlds, and four spacecraft to the stars. We are right to rejoice in our accomplishments, to be proud that our species has been able to see so far, and to judge our merit in part by the very science that has so deflated our pretensions.
  • Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space (1994) p. 53

• The first, and main, problem is the very existence of the big bang.
  • Andrei Linde, quoted in the article The Awesome Universe; What the Big Bang Explains—What It Doesn’t, in the Awake! magazine, January 22, 1996.

• One may wonder, What came before? If space-time did not exist then, how could everything appear from nothing? . . . Explaining this initial singularity—where and when it all began—still remains the most intractable problem of modern cosmology.
  • Andrei Linde, quoted in the article The Awesome Universe; What the Big Bang Explains—What It Doesn’t, in the Awake! magazine, January 22, 1996.

• [Big Bang theory] suggested that matter and motion originated rather as Genesis [in the Bible] suggests, ex nihilo, out of nothing, in a stupendous explosion of light and energy.
  • Newsweek magazine of November 9, 1998.

• The forces loosed were—are—remarkably (miraculously?) balanced: If the Big Bang had been slightly less violent, the expansion of the universe would have been less rapid, and would soon (in a few million years, or a few minutes—in any case, soon) have collapsed back on itself. If the explosion had been slightly more violent, the universe might have dispersed into a soup too thin to aggregate into stars. The odds against us were—this is just the right word—astronomical. The ratio of matter and energy to the volume of space at the Big Bang must have been within about one quadrillionth of 1 percent of ideal.
  • Newsweek magazine of November 9, 1998.

• Take but degree away (see above, the one quadrillionth of 1 percent margin for error), . . . and what follows is not just discord but eternal entropy and ice. So, what—who?—was the great Tuner?
  • Newsweek magazine of November 9, 1998.

• The big bang theory does not describe the birth of the universe … Another theory describing even earlier times will be needed to explain the original creation of the universe.
  • Reported in its January 1999 issue the magazine Scientific American.

• I'll say only this: if we're going to throw the idea of the Big Bang overboard, we won't have much left of current astrophysics and cosmology
  • Charles Sheffield, The Spheres of Heaven (2001), ISBN 0-671-31856-X, p. 334 (Chapter 23)

• There are some questions that scientists can never answer, “It may be that the Big Bang happened 12 billion years ago. But why did it happen? . . . How did the particles get there in the first place? What was there before?” Utley concludes: “It seems . . . clearer than ever that science will never satisfy the human hunger for answers.”
  • Tom Utley quoted in the article How Did the Universe and Life Originate?, in the Awake! magazine, June 8, 2002.

• The big bang and the steady state debate in some ways echoed that between the ideas of Anaximander and Anaxagoras from two and a half millennia earlier. Anaxagoras had envisaged that at one time "all things were together" and that the motive force for the universe originated at a single point... Anaximander on the other hand wanted a universe determined by "the infinite" and needed an "eternal motion" to explain the balancing process of things coming into being and passing away in an eternal universe... ancient philosophy was debating the alternatives of a creation event starting the universe from a single point versus a continuous creation in an eternal universe.
  • David H. Clark & Matthew D. H. Clark, in Measuring the Cosmos: How Scientists Discovered the Dimensions of the Universe (2004).

• We are privileged to be part of the first generation who can claim to have a respectable, rational, and coherent description for the creation and evolution of the universe. The Big Bang model offers an elegant explanation of the origin of everything we see in the night sky, making it one of the greatest achievements of the human intellect and spirit. It is the consequence of an insatiable curiosity, a fabulous imagination, acute observation and ruthless logic.
  Even more wonderful is that the Big Bang model can be understood by everyone.
  • Simon Singh, Big Bang: The Origin of the Universe (2004)

• The big bang was not an explosion in space; it was more like an explosion of space.
  • Tamara Davis, Charles Lineweaver, "Misconceptions About the Big Bang," Scientific American (March, 2005)

• The big bang happened everywhere. It was not a bomb going off at a particular spot that we can identify as the center of the explosion.
  • Tamara Davis, Charles Lineweaver, "Misconceptions About the Big Bang," Scientific American (March, 2005)

• I am convinced that the race backwards in space and time, to the origins of the Big Bang and the elementary structure of matter, is infinite; logically and spatially inaccessible. I therefore believe that the quarks that make up electrons and protons are not the most elementary particles at all; similarly, there is no single chain of events that led from the Big Bang to us, but an infinity of equally plausible possibilities. Mine is still a faith, because I have no proof of anything.
  • Tullio Regge. As quoted in Lara Reale, Silvia Artana, La teoria delle stringhe, secondo Tullio Regge? "Si sta colando a picco", torinoscienza.it, 22 January 2008 (in Italian)

• The Big Bang understood as the event that created the hot, dense gas of cosmic matter was not an explosion starting from a point in space. If it had been, we could detect traces of that initial point today. Instead, astronomical observations teach us that the primordial matter gas was incredibly uniform and homogeneous. This indicates that the universe in its infancy was like a giant pot of well-mixed soup. The Big Bang is the event in which this soup was created, not at any special point, but homogeneously everywhere in the pot. It is a uniform transition that involved a very large, perhaps even infinite, region of space that was suddenly filled with matter. Understanding the Big Bang means understanding what caused this transition."{{NDR|And before the Big Bang, what was there?} Today it is thought that before the Big Bang there was only empty space. A very special empty space, however. There was no matter, but the fabric of space was imbued with a form of energy called precisely vacuum energy capable of exerting repulsive gravity. The effect is quite amazing because it is the exact opposite of the force of gravity we are used to, which can only attract material bodies.
  • Gian Francesco Giudice. As quoted in Maria Lombardi, Big Bang, cosa c'era prima? Gian Francesco Giudice (capo dei fisici Cern): «L'universo non è nato da un'esplosione» (November 13, 2023)