Yesterday announcement of the Harvard astronomy center about discovery gravitational waves and confirming the theory of cosmic inflation was one of the most important scientific discoveries of the last decades and came after a long and collective effort. But what was it that made it so significant? In order to understand its meaning, some concepts that are not found in everyday vocabulary will need to be explained.
The Big Bang
Our knowledge of cosmology has developed rapidly in the last century. It is indicative that at the beginning of 20th century we did not know that there were other galaxies beyond our own. In the first quarter of the last century it was known that not only are there many other galaxies but also that there is a phenomenon called the expansion of the Universe that overturned the image of a stable, eternal and unchanging universe.
Making her iftreatment backwards, one would reasonably assume that the Universe in the past was increasingly dense. According to astronomical observations as well as theoretical ones forecasts, we believe that about 13.8 billion years ago the Universe was condensed into a point of infinite density, from which arose what we call the Big Bang. Physical theories break down at the moment of the birth of the Universe, but scientists focus on the immediate moments that were decisive for the shape the Universe has today.
The cosmic inflation
The Big Bang model provides several answers about the Universe, but leaves a series of unanswered questions: why is the Universe so homogeneous and isotropic (it looks the same in any direction we look, no matter where we are), why the Universe is so amazingly tuned to be flat (out of all possible values, it seems that its density balances with incredible precision at a certain price which implies a Universe described by Euclidean geometry) etc. These questions are elegantly settled by the idea of cosmic inflation. According to her, shortly after the Big Bang (we don't know exactly when, but around 10-35 seconds later), the universe expands exponentially, for a short time, due to the presence of a field. The exact form of the inflation field is not known, as there are many different models that we can divide according to their projections, and scientific discoveries such as yesterday are therefore very useful.
General Relativity and gravitational waves
The "language" that describes modern cosmology is the theory of General Relativity, invented by Albert Einstein in the first quarter of 20th century. It is a gravitational theory, and since gravity, although the weakest of the forces, is predominant over long distances (matter is basically electrically neutral, while nuclear forces have a small range), through which the evolution of the universe is described.
Gravitational waves are a prediction of theory, but this has not been confirmed so far. According to the General Theory of Relativity, gravity is related to the distortion of the geometry of space-time caused by the presence of mass or energy-is essentially the same thing. This deformation spreads in the form of waves that are very difficult to detect since they come from a weak force.
Background radiation and polarization
The main evidence for the Big Bang theory is the so-called background radiation, that is, the light that continues to be emitted even today, as an echo of the birth of the Universe. As it is light (of low frequency, since the intercession of 13.8 billion years has it "freeze»), reveals the property of polarization. The polarization of electromagnetic radiation can be of several types, called ways.
What scientists have spotted in the experiment VICEP (Background Imaging of Cosmic Extragalactic Polarization) was a particular mode of polarization in the background radiation, called mode B. This mode is a "signature" of the gravitational wave effect of the early Universe, which occurred because gravitational waves compress space and time as they propagate, and this compression creates a pattern for the propagating radiation. Here the concept of inflation is introduced, since the discovery is a prediction of the specific theory. This point is indeed sensitive, because it opens a window of compatibility between General Relativity (a classical theory) and quantum mechanics, which is one of the biggest problems of modern physics.
Today's discovery is important for a variety of reasons and is about to pave the way for new research. Firstly, it is the confirmation of one of the basic predictions of the theory of cosmic inflation and therefore of theory itself, while giving scientists the possibility of a new way of studying the Universe through gravitational waves.
