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

In every direction we care sicuro observe, we find stars, galaxies, clouds of vapore and dust, tenuous plasmas, and http://www.datingranking.net/it/pure-review radiation spanning the gamut of wavelengths: from radio sicuro infrared puro visible light sicuro modo 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 to 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 esatto simply extrapolate forward con time, when things will be even larger, less dense, and cooler, the laws of physics allow us to 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 sicuro go as far as possible: all the way back preciso infinitesimal sizes and infinite densities and temperatures, or what we know as verso singularity. This intenzione, of per singular beginning onesto space, time, and the universe, was long known as the Big Bang.

The modern cosmic picture of our universe’s history begins not with verso singularity that we identify with the Big Bang, but rather with per period of cosmic inflation that stretches the universe sicuro 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 the universe anymore.

Countless scientific tests of Einstein’s general theory of relativity have been performed, subjecting the idea puro 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 preciso our Solar System with dramatic success. Very quickly, verso handful of exact solutions were found thereafter. (Credit: LIGO scientific collaboration, T. Pyle, Caltech/MIT)

Where did all this come from?

Like most stories sopra science, the origin of the Big Bang has its roots per both theoretical and experimental/observational realms. On the theory side, Einstein put forth his general theory of relativity durante 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. In 1916, Karl Schwarzschild found the solution for a pointlike mass, which describes a nonrotating black hole.
2. Per 1917, Willem de Sitter found the solution for an empty universe with a cosmological constant, which describes an exponentially expanding universe.
3. From 1916 preciso 1921, the Reissner-Nordstrom solution, found independently by four researchers, described the spacetime for verso charged, spherically symmetric mass.
4. Durante 1921, Edward Kasner found a solution that described per matter-and-radiation-free universe that’s anisotropic: different durante different directions.
5. Per 1922, Alexander Friedmann discovered the solution for an isotropic (same con 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 onesto describe our universe on the largest scales, where things appear similar, on average, everywhere and sopra 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.