The Big Bang Theory

1. THE BIG BANG THEORY
BY: ANA CABELLOS,NURIA JEREZ & LUCIA SAN JUAN
4ºESO B

2. History of the big bang
-Dicoveries in astronomy and physics have shown that
universe started in a proccess called The Big Bang.
-This theory tries to explain what happened.
-Thanks to all the observations we say the universe
started 13.810 million years ago.
-Since then the universe has suffered 3 different
phases.
-The future of the universe is not clear.

3. History
-The Big Bang occurred in an infinitely dense and
hot spot. It wasn’t a normal explosion as the
ones we know.
-Immediately after the moment of the "explosion"
every particle of matter began to move away very
quickly, so it started occupying more space and that’s
why expanded so much.

4. History
-This theory indicates that in the past these
elements were closer than today, so if we go
back in time, then all the stuff was together at
one point. That point is called singularity, which
was a fireball.

5. Development
-Einsten: he came up with 10 field equations to support his
theory of relativity.
-Friedmann: proposed a close universe, where everything
would finish as it started in one point, and an open universe,
where the universe would continue expanding for ever, with
no end.
-Hubble: measured the distance to the nearest nebulae and
showed that these systems were indeed other galaxies.
-Slipher: discovered that almost all such nebulae were
receding from the Earth.

6. Problems
Between the 1920s and 1930s almost
every cosmologist preferred an eternal
steady state of the Universe and several
complained that the beginning of time
implied by the Big Bang imported
religious concepts into physics.
This objection was later repeated
by supporters of the steady state
theory, (this basically says that
the universe is always expanding
but maintaining a constant
average density). So this
perception was enhanced by one
of the originators of the Big Bang
Theory, Monsignor Georges
Lemaître, who was a Roman
Catholic priest.

7. Evidence
During the 1930s, other ideas
were proposed as non-standard
cosmologies to explain Hubble’s
observations, including the
Milne model and the oscillatory
Universe (which was originally
suggested by Friedmann but
advocated by Albert Einstein and
Richard Tolman).
However, it was then criticized by the
supporters of the steady state theory
which says that, if the Universe was
really initially as hot as the Big Bang
theory suggests, we should be able to
find, nowadays, some remainings of this
heat.

8. Eddington and Lemaître
Arthur Eddington agreed with
Aristotle that the Universe did not
have a beginning in time and that
matter is eternal. A beginning in time
was kind of “disgusting” to him.
Lemaître, however, said: “If the world has a
beginning with a single quantum, the notions of
space and time would altogether fail to have
any meaning at the beginning; they would only
begin to have a sensible meaning when the
original quantum is divided into a sufficient
number of quanta. If this suggestion is correct,
the beginning of the world happened a little
before the beginning of space and time.”

9. Novel Prize 1978
Later on, in 1965, two radio
astronomers discovered a
2.725 degree Kelvin Cosmic
Microwave Background
radiation (CMB) which
pervades the observable
Universe. This is thought to
be a remnant which
scientists were looking for
to support the Big Bang
Theory. These two radio
astronomers shared the
Nobel prize for physics for
the discovery in 1978.

10. Expansion of the Universe
Significant progress in Big Bang cosmology had been made since the
late 1990s as a result of the advantages in telescope technology as
well as the analysis of data from satellites, such as COBE.
Cosmologists now have fairly precise and accurate the measurements
of many of the parameters of the Big Bang model, and have made an
unexpected discovery: ‘the expansion of the Universe appears to be
accelerating.

11. Common misconceptions
When we talk about the big
bang theory, many of us
think about a huge
explotion, but it isn´t, it was
(and it is) an expansion. For
you to have an idea, rather
than figuring a balloon
popping and releasing its
contents, imagine a balloon
expanding, infinitesimally
small balloon expanding the
size of our current universe.
We tend to imagine the
singularity as a little
fireball appearing
somewhere in space; but
according to many
experts, space didn’t
exist before the big bang
took place.
According to calculations, time and space
had a finite beginning that corresponded
to the origin of matter and energy. The
singularity didn’t appear in space; rather,
space began inside the singularity. Prior
to the singularity, nothing existed, not
space, time, matter, or energy-nothing.

12. THE HIGGS BOSON AND THE BIG BANG
The particle studied by physicists at
CERN may also play a role in the
Big Bang Theory.
Physicists applied a mathematical
principle known as scale invariance
– starting with the Higgs boson,
they were able to determine the
existence of the dilaton, a close
cousin, as well as its properties.
the expansion of the current
Universe is once again accelerating,
but its origins are not understood.
This theoretical advance – a
completely unexpected result – is
reassuring the scientists that they
may be on the right track.

13. Astrophysicists are measuring
the state of the Universe today
using data from the Planck
satellite. They are observing the
light echo from the Big Bang,
which reveals the large scale
properties of the cosmos. In
2013, the measurement
campaign will provide results
that will be precise enough to
compare with the EPFL
scientsits' theoretical
predictions – and they'll be able
to see if their Higgs theory
holds up. The boson isn't just
hidden in the bowels of CERN's
accelerator.
CERN’s acelerator.(ABOVE)
Light echo from the Big Bang Theory.
(DOWN)

14. Hubble’s Law
It is the linear relationship between a galaxy’s
distance and ``aparent´´ recessional
velocity.
It implies the Universe is expanding.
First observational support for Lemaître’s
prediction in 1927.
The American astronomer
Edwin Hubble uncovered
important evidence that the
Universe is expanding.
He compared the measured
relative velocities (red shifts)
of faraway galaxies with his
estimates of their distances
from the Earth.
In 1929 he announced his
discovery that the further
away a galaxy is from another
point in space, the faster it
appears to recede as the
Universe expands - Hubble's
Law.
But there was more to be
discovered about the
expanding Universe - dark
energy.

15. Problems with the Big Bang Theory
1.- The Horizon Problem: discussion of the cosmic microwave background:
when we look at the microwave background radiation coming from widely
separated parts of the sky, it can be shown that these regions are too
separated to have been able to have ever communicated with each other
even with signals travelling at light velocity. Thus, how did they know to
have almost exactly the same temperature? This general problem is
called the horizon problem, because the inability to have received a signal
from some distant source because of the finite speed of light is termed a
horizon in cosmology. Thus, in the standard big bang theory we must
simply assume the required level of uniformity.

16. 2.-The Flatness Problem: present Universe has very low geometrical
curvature in its spacetime (it is nearly flat). Theoretical arguments that
are well established but too complex to go into here suggest that this is
a very unlikely result of the evolution of the Universe from the big bang,
unless the initial curvature is confined to an incredibly narrow range of
possibilities. While this is not impossible, it does not seem very natural.

17. 3.-The Monopole Problem:The only plausible theory in elementary particle
physics for how nuclei in the present universe were created in the big
bang requires the use of what are called Grand Unified Theories
(GUTs). In these theories, at very high temperatures such as those
found in the instants after the Universe was created the strong, weak,
and electromagnetic forces were (contrary to the situation today)
indistinguishable from each other. We say that they were unified into a
single force.
Although there is as yet no certain evidence for the validity of such
theories, there is strong theoretical reason to believe that they will
eventually turn out to be essentially correct. Our current understanding
of elementary particle physics indicates that such theories should
produce very massive particles called magnetic monopoles, and that
there should be many such monopoles in the Universe today. However,
no one has ever found such a particle. So the final problem is: where
are the monopoles?