In the 20th Century, we have gone from
being ignorants about the surrounding Universe (we only had
some local knowledge of the Solar System
and its Planets) to knowing a big percentage of its main properties.
One of the great observations made last Century,that I believe
to be fundamental was the discovery of the expansion of the Universe,
which is something that is not evident at first glance.
We can see distant objects and Galaxies, almost stable
in the night sky. Nevertheless, there were some
observations that suggested that these objects
weren't actually stable in space but that they were
all moving away from one another.
This was proposed by this man here, Sir Edwin Hubble,
who observed galaxiesthat were nearby our Milky Way
and demonstrated that they were moving away.
the way in which these galaxies were moving was not
fortuitous: the speed of separation was proportional to their distance
from us, in other words, the furthest galaxies moved
faster than the ones that were closer to us.
One of the presumptions that we can infer
from this movement is the idea that they were
really close at some previous point in time.
This implies that the origin of the Universe was probably
characterized by the condensation of its objects.
So, this is what underlies the Big Bang theory somehow,
which I supposed that is something you have already heard of.
The Big Bang theory suggests that the Universe originated at some point
in which it was pretty small compared to what it is nowadays.
Additionally, its initial state was characterized by
extreme density and temperature.
>From that moment on, the Universe is expanding,
time and space were created, and expanded;
temperatures began to lower meanwhile it expanded;
and more complex elements were formed little by little.
Due to the extreme density and temperature in the
original Universe, there could only exist the elementary particles,
namely, electrons, quarks, photons (particles associated with light)
but in the process of expansion and the Universe becoming colder,
some conglomerations formed, bigger and bigger each time:
protons and neutrons grouped and formed quarks,
later on protons and neutrons formed the simplest elements known so far,
for instance helium, hidrogen (just one proton), litium..
Later on, atoms were created when electrons
surrounded those elements... so advancing in the history
of the Universe, these atoms grouped and the Univers
eventually became transparent,
and it was a little bit later when the galaxies
and other celestial objects were formed.
Excerpt from the conference held
November 7th, 2013, at the Residencia de Estudiantes,
during the sessions "La frontera de la Física Fundamental"
Full video available at: www.eddaddeplata.org