The Big Bang Theory

By Marina García, Jade Turner and Marina Pascual 4º ESO B

What is the big bang theory? (Jade)

The Big Bang Theory is the way we explain what happen for the creation of our Universe. It is the model that describes the early discovery of it.

When did it take place?

It occurred approximately 13,7 billion years ago. And the Universe was extremely hot and dense. There are many hypothesis surrounding the Big Bang Theory, one of these is that people tend to imagine a giant explosion, but however it was not, it is a continuous expansion.

TIMELINE:

What happened next?

After the initial expansion, the Universe cooled enough to allow energy to be converted into various subatomic particles, including protons, neutrons and electrons.

One of the results of the Big Bang: Forces

One result of the big bang was the formation of the four basic forces in the universe:

– Electromagnetism– Strong nuclear force– Weak nuclear force. – Gravity

Physicists and cosmologists are working of the Grand unified theory, which would explain how these four forces were once united and how they relate to each other.

One of the results of the Big Bang : Atoms

The majority of atoms that were produced by Big Bang Theory are hydrogen, 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.

Result of the observations

The core ideas of the Big Bang, the expansion, the early hot state, the formation of light elements, and the formation of galaxies, are deriver from these observations.

How the Big Bang Theory is supported?

Astronomers combine mathematical models with observations to develop workable theories of how the Universe came to be. According to many experts, space did not exist before the Big Bang.

One of the supporters of the Big Bang Theory: Theory of Relativity

The mathematical support of the Big Bang Theory includes Albert Einstein’s Theory of Relativity along with standard theories of fundamental particles.

One of the supporters of the Big Bang Theory: The Doppler effect

Austrian physicist Christian Doppler discovered that the frequency of a sound wave depended upon the relative position of the source of the sound.

As a noisy object approaches you, the sound waves it generates compress.

This changes the frequency of the sound, and so you perceive the sound as a different pitch.

When the object moves away from you, the sound waves stretch and the pitch goes down.

What happened:

If we would have looked at the Universe one second after the Big Bang, we would see a 10 billion degree mass of neutrons, protons, electrons, positrons, photons and neutrinos.

What happened:

Then, as time went on, we would see the Universe cooling down, the neutrons decaying into protons and electrons, or combining with protons to make an isotope of hydrogen.

What happened:

As it continued cooling, it eventually reach the temperature where electrons combined with nuclei to form neutral atoms.

What happened:

Before this ‘recombination’ occurred, the Universe would have been opaque because the free electrons would have caused light. But when the free electrons were absorbed to form neutral atoms, the Universe became transparent, and that is why we nowadays see the cosmic background radiation.

Evidence for the Theory:

1. We are sure that the universe had a beginning.

2. Galaxies appear to be moving away from us at speeds proportional to their distance; this is called ‘Hubble’s Law’

3. If the universe was initially very hot, we should be able to find some remnant of the heat (Cosmic Microwave Background radiation).

4. The abundance of light elements, hydrogen and helium found in the observable universe.

Alternative models to the Big bang Theory: The Steady-State Model

The steady-state model of the universe suggests the universe always had and will always have the same density. It suggests that the universe generates matter at a rate proportionate to the universe's rate of expansion.

Alternative models to the Big bang Theory: The Ekpyrotic model

The Ekpyrotic model suggests our universe is the result of a collision of two three-dimensional worlds on a hidden fourth dimension.

Alternative models to the Big Bang Theory: The Big Bounce Theory.

The big bounce theory suggests our universe is one of a series of universes that first expand, then contract again. The cycle repeats after several billion years.

Plasma cosmology attempts to describe the universe in terms of the electro-dynamic properties of the universe.

We do not know where it came from, why it is here, or even where it is. All we really know is that we are inside of it and at one time it did not exist and neither did we.

One of the goals has long been to decide whether the Universe will expand forever, or whether it will someday stop, turn around, and collapse in a ‘Big Crunch’.