Surprise: the Big Bang isn’tau the beginning of the universe anymore

Surprise: the Big Bang isn’tau the beginning of the universe anymore

The Big Bang teaches us that our expanding, cooling universe used to be younger, denser, and hotter con the past.

Sopra every direction we care onesto observe, we find stars, galaxies, clouds of vapore and dust, tenuous plasmas, and radiation spanning the gamut of wavelengths: from radiotrasmissione onesto infrared esatto visible light preciso qualita rays. No matter where or how we look at the universe, it’s full of matter and energy absolutely everywhere and at all times. And yet, it’s only natural preciso garantis that it all came from somewhere. If you want to know the answer esatto the biggest question of all – the question of our cosmic origins – you have esatto pose the question onesto the universe itself, and listen preciso what it tells you.

Today, the universe as we see it is expanding, rarifying (getting less dense), and cooling. Although it’s tempting onesto simply extrapolate forward per time, when things will be even larger, less dense, and cooler, the laws of physics allow us onesto extrapolate backward just as easily. Long spillo, the universe was smaller, denser, and hotter. How far back can we take this extrapolation? Mathematically, it’s tempting esatto go as far as possible: all the way back onesto infinitesimal sizes and infinite densities and temperatures, or what we know as per singularity. This intenzione, of verso singular beginning esatto space, time, and the universe, was long known as the Big Bang.

The modern cosmic picture of our universe’s history begins not with per singularity that we identify with the Big Bang, but rather with a period of cosmic inflation that stretches the universe preciso enormous scales, with uniform properties and spatial flatness

But physically, when we looked closely enough, we found that the universe told per different story. Here’s how we know the Big Bang isn’t the beginning of mingle2 on-line the universe anymore.

Countless scientific tests of Einstein’s general theory of relativity have been performed, subjecting the preoccupazione preciso some of the most stringent constraints ever obtained by humanity. Einstein’s first solution was for the weak-field limit around verso single mass, like the Sun; he applied these results onesto our Solar System with dramatic success. Very quickly, per handful of exact solutions were found thereafter. (Credit: LIGO scientific collaboration, T. Pyle, Caltech/MIT)

Where did all this che from?

Like most stories in science, the origin of the Big Bang has its roots durante both theoretical and experimental/observational realms. On the theory side, Einstein put forth his general theory of relativity con 1915: a novel theory of gravity that sought preciso overthrow Newton’s theory of universal gravitation. Although Einstein’s theory was far more intricate and complicated, it wasn’t long before the first exact solutions were found.

  1. Durante 1916, Karl Schwarzschild found the solution for verso pointlike mass, which describes verso nonrotating black hole.
  2. Durante 1917, Willem de Sitter found the solution for an empty universe with verso cosmological constant, which describes an exponentially expanding universe.
  3. From 1916 esatto 1921, the Reissner-Nordstrom solution, found independently by four researchers, described the spacetime for per charged, spherically symmetric mass.
  4. Sopra 1921, Edward Kasner found per solution that described a matter-and-radiation-free universe that’s anisotropic: different in different directions.
  5. In 1922, Alexander Friedmann discovered the solution for an isotropic (same in all directions) and homogeneous (same at all locations) universe, where any and all types of energy, including matter and radiation, were present.

That last one was very compelling for two reasons. One is that it appeared sicuro describe our universe on the largest scales, where things appear similar, on average, everywhere and per all directions. And two, if you solved the governing equations for this solution – the Friedmann equations – you’d find that the universe it describes cannot be static, but must either expand or contract.