Transcript La teoria del big bang y la formacion del Universo

La teoria del big bang y la
formacion del Universo
• The Big Bang theory is the prevailing cosmological model for the early
development of the universe.
• The key idea is that the universe is expanding. Consequently, the
universe was denser and hotter in the past. Moreover, the Big Bang
model suggests that at some moment all matter in the universe was
contained in a single point, which is considered the beginning of the
universe.
• Modern measurements place this moment at approximately ~13.8
billion years ago, which is thus considered the age of the universe.
• After the initial expansion, the universe cooled sufficiently to allow
the formation of subatomic particles, including protons, neutrons,
and electrons. Though simple atomic nuclei formed within the first
three minutes after the Big Bang, thousands of years passed before
the first electrically neutral atoms formed.
• The majority of atoms that were produced by the Big Bang are
hydrogen, along with helium and traces of lithium. Giant clouds of
these primordial elements later coalesced through gravity to form
stars and galaxies, and the heavier elements were synthesized either
within stars or during supernovae.
Background radiation left over from
the Big Bang
free electrons met up with nuclei and created
neutral atoms. This allowed light to shine
through about 380,000 years after the Big
Bang.
• Most of this matter, which formed from the
pure energy of the Big Bang, took the form of
hydrogen and helium atoms within about
300,000 years.
• So where did all of the other elements like
carbon, oxygen, and iron come from? ->
Elements larger than hydrogen and helium
formed during the last supernova stage of
dying stars.
• Within a few hundred million years after the Big
Bang, the hydrogen and helium had pulled
together under the force of gravity to form stars,
which shine because hydrogen atoms are fusing
together to make helium atoms, releasing
radiation energy in the process.
• When the hydrogen runs out, the stars go
through a rapid sequence of fusion stages called a
supernova that produces heavier elements and
then ejects them into space.
• This means that most of Earth, including your
body, is made of the exploded ashes of a dead
star.
The matter of our planet was primarily made through two very
different mechanisms: the Big Bang and the supernovae of
dying stars.
- The moment the Big Bang occurred, the universe
immediately began to expand at speeds on the
order of the speed of light. The energy and matter
expanded outward, pulling the universe with it.
- Soon after the Big Bang, energy began converting
into matter according to Einstein’s well-known
equation E = mc2 .
Predicted timeline of the Big Bang
• 1) At the start of the Big Bang, all four of the
fundamental forces were unified as a single
force (weak nuclear, strong nuclear,
electromagnetism and gravity).
• 2) By 10-43 seconds after the Big Bang the
single unified force began to split apart.
• 3) By 10-34 seconds, the universe entered into
a period of inflationary expansion, moving
faster than the speed of light.
• 4) By 10-32 seconds, the first subatomic
particles were forming. The universe was 30
centimeters in diameter and had a
temperature of 3x1026 K.
• 5) By 10-11 seconds, the four forces had finally
separated with the split of the
electromagnetic and weak nuclear forces.
• 6) By 10-5 seconds, protons and neutrons had
formed, though it was still too hot for stable
atoms to form. The universe was 0.002 lightyears in size (100 times the earth-sun
distance) and had a temperature of 1013 K.
• 7) By one second, electrons had formed and were
annihilating positrons. The universe was three
light-years in size with a temperature of 1010 K.
• 8) By three minutes, hydrogen atoms were
forming, though it was still too hot for stable
atoms to form. The universe was 50 lightyears in
size with a temperature of 1 billion degrees
Kelvin.
• 9) By 10,000 years, matter began to dominate
over radiation. The universe was two million
light-years in size with a temperature of 30,000 K.
• 10) By 1 billion years, protogalaxies and the
first stars were forming. The universe was 10
billion light-years in size with a temperature of
only 10 K.
• 11) By 5 billion years, full galactic disks were
forming. The universe was 20 billion lightyears in size with a temperature of 5 K.
• 12) Currently, 13.7 billion years after the Big
Bang, the universe is 40 billion light-years in
size with a temperature of 2.7 K
• (- 270.42° C).
• The fate of the universe depends upon the
amount of mass it contains.
• 1. If there is too much mass, the universe will
stop expanding and eventually collapse;
• 2. if there is too little mass, the universe will
continue to expand forever.
• It currently seems as if the rate of expansion
of the universe is actually increasing.
Gravity
• The force of gravity is responsible for the
formation of galaxies. Galaxies contain
between tens of millions and a trillion stars.
Stars are more plentiful and tend to be much
larger near the centers of galaxies.
• Stars are born when there is enough
hydrogen that the intense pressure causes
hydrogen atoms to fuse together to form
helium, emitting light in the process. This
process is called nuclear fusion.
Near the end of a star’s life, hydrogen fusion occurs in the
outer layer of the star, and the star swells in size to become a
red giant or supergiant.
In the final stages of a star, when the hydrogen runs low, the
helium begins fusing to start a series of fusion reactions that
creates elements larger than helium.
• Stars follow a life cycle that is variable
depending upon the size of the star.
• 1. Low-mass stars, at the end of their
lifetimes, go through a sequence of becoming
red giants, planetary nebulae, and then white
or black dwarves; small stars can last for many
billions of years.
• High-mass stars go through a final sequence
of being a red supergiant, a supernova, and
either a neutron star or black hole; very large
stars can burn out in only thousands of years.
• The fact that our solar system contains
planets means that our sun must be a secondgeneration star. A previous star had to die for
the planet
• Earth to be formed from its remains.