The mathematical underpinnings of the Big Bang theory include Albert Einstein’s general theory of relativity along with canone theories of fundamental particles. Today NASA spacecraft such as the Hubble Space Telescope and the Spitzer Space Telescope continue measuring the expansion of the Universe. One of the goals has long been preciso decide whether the Universe will expand forever, or whether it will someday fermo, turn around, and collapse in per “Big Crunch?”
Retroterra Radiation
According esatto the theories of physics, if we were sicuro aspetto at the Universe one second after the Big Bang, what we would see is a 10-billion degree sea of neutrons, protons, electrons, anti-electrons (positrons), photons, and neutrinos. Then, as time went on, we would see the Universe cool, the neutrons either decaying into protons and electrons or combining with protons preciso make deuterium (an isotope of hydrogen). As it continued preciso cool, it would eventually reach the temperature where electrons combined with nuclei onesto form neutral atoms. Before this “recombination” occurred, the Universe would have been opaque because the free electrons would have caused light (photons) to scatter the way sunlight scatters from the vaso droplets sopra clouds. But when the free electrons were absorbed puro form neutral atoms, the Universe suddenly became transparent. Those same photons – the afterglow of the Big Bang known as cosmic sostrato radiation – can be observed today.
Missions Study Cosmic Sostrato Radiation
NASA has launched two missions sicuro study the cosmic background radiation, taking “bambino pictures” of the Universe only 400,000 years after it was born. The first of these was the Cosmic Sostrato Explorer (COBE). Mediante 1992, the COBE staff announced that they had mapped the primordial hot and cold spots con cosmic sostrato radiation. These spots are related onesto the gravitational field sopra the early Universe and form the seeds of the giant clusters of galaxies that stretch hundreds of millions of light years across the Universe. This rete di emittenti earned NASA’s Dr. John C. Mather and George F. Smoot of the University of California the 2006 Nobel Prize for Physics.
The second mission onesto examine the cosmic retroterra radiation was the Wilkinson Microware Anisotropy Probe (WMAP). With greatly improved resolution compared puro COBE, WMAP surveyed the entire sky, measuring temperature differences of the microwave radiation that is nearly uniformly distributed across the Universe. The picture shows a map of the sky, with hot regions per red and cooler regions mediante blue. By combining this evidence with theoretical models of the Universe, scientists have concluded that the Universe is “flat,” meaning that, on cosmological scales, the geometry of space satisfies the rules of Euclidean geometry (ancora.g., parallel lines never meet, the ratio of circle circumference to diameter is pi, etc).
Per third mission, Planck, led by the European Space Agency with significant participation from NASA, was. launched durante 2009. Planck is making the most accurate maps of the microwave sostrato radiation yet. With instruments compatissante onesto temperature variations of per few millionths of verso degree, and mapping the full sky over 9 wavelength bands, it measures the fluctuations of the temperature of the CMB with an accuracy arnesi by fundamental astrophysical limits.
Inflation
One problem that arose from the original COBE results, and that persists with the higher-resolution WMAP data, was that the Universe was too homogeneous. How could pieces of the Universe that had never been in contact with each other have che tipo di to equilibrium at the very same temperature? This and other cosmological problems could be solved, however, if there had been verso very short period immediately after the Big Bang where the Universe experienced an incredible burst of expansion called “inflation.” For this inflation esatto have taken place, the Universe at the time of the Big Bang must have been filled with an unstable form of energy whose nature is not yet known. Whatever its nature, the inflationary model predicts that this primordial energy would have been unevenly distributed durante space paio puro per kind of quantum noise that arose when the Universe was extremely small. This pattern would have been transferred puro the matter of the Universe and would esibizione up per the photons that began streaming away freely at the moment of recombination. As a result, we would expect onesto see, and do see, this kind of pattern sopra the COBE and WMAP pictures of the Universe.
But all this leaves unanswered the question of what powered inflation. One difficulty con answering this question is that inflation was over well before recombination, and so the opacity of the Universe before recombination is, in effect, a curtain drawn over those interesting very early events. Fortunately, there is verso way sicuro observe the Universe that does not involve photons at all. Gravitational waves, the only known form of information that can reach us undistorted from the instant of the Big Bang, can carry information that we can get niente affatto other way. Several missions are being considered by NASA and ESA that will immagine for the gravitational waves from the epoch of inflation.
Dark Energy
During the years following Hubble and COBE, the picture of the Big Bang gradually became clearer. But con 1996, observations of very distant superatic change in the picture. It had always been assumed that the matter of the Universe would slow its rate of expansion. Mass creates gravity, gravity creates pull, the pulling must slow the expansion. But supernovae observations showed that the expansion of the Universe, rather than slowing, is accelerating. Something, not like matter and not like ordinary energy, is pushing the galaxies apart. This “stuff” has funziona military cupid been dubbed dark energy, but puro give it a name is not to understand it. Whether dark energy is a type of dynamical fluid, heretofore unknown onesto physics, or whether it is a property of the vacuum of empty space, or whether it is some modification esatto general relativity is not yet known.
