Theories of the Origin of the Universe

THEORIES OF THE ORIGIN OF THE UNIVERSE

1. Steady State Theory – based on the perfect cosmological principle that the universe looks the same from any location at anytime. This theory holds that the universe is unchanging, it has no beginning and no end.

2. Big Bang Theory – presupposes that the vast universe grew out of something where all matter and energy were compressed to infinite density and heated to trillions of degrees (a beginning which was an immensely small particle of high-density state. The four basic forces of nature – gravity, electromagnetism, strong and weak atomic forces – were unified in that tiny particle. This particle exploded into a great fire ball releasing the basic forces. Rapid expansion took place and then the fire ball started to cool and slow down.

Of these two theories discussed, the Big Bang theory is the most popular.

What are the evidences for the Big Bang Theory?

1. The universe had a beginning – Einstein’s theory of gravity (which has been thoroughly validated by extensive experimental confirmation) preclude an eternal universe. We now know beyond a reasonable doubt that the universe began at some point in the finite past.

2. The universe is expanding – (Edwin Hubble, 1929) Observed a Red Shift when looking at the spectrum light coming from distant galaxies. All light from these galaxies is shifted towards longer wavelengths, i.e.. toward red light. This is the Doppler effect and could only occur if the galaxies were moving away from each other at very high speeds. In fact they are moving away from each other at a rate proportional to the distance between them.

ORDER OF EVENTS INTO THE FORMATION OF THE UNIVERSE ACCORDING TO THE BIG BANG THEORY

1. Big Bang (infinitely small universe)

* Four Basic Forces of Nature were united - Grand Unified Theory (GUT Theory)

* Gravity – the weakest force. It is always attractive, and acts between any two pieces of matter in

the Universe since mass is its source.

• Weak Atomic Force – responsible for radioactive decay and neutrino interactions. It has a very short range and, as it name indicates, it is weak.

• Electromagnetic force – causes electric and magnetic effects such as the repulsion between like electrical charges or the interaction of bar magnets. It is long ranged but much weaker than the strong force.

• Strong Atomic Force – is very strong. This force holds the atomic nucleus together. This is the “glue” which binds the protons and neutrons in a nucleus.

2. Gravity separates from the four basic forces.

3. Strong nuclear forces separate out (quarks/electrons and antimatter form).

4. Quarks combine to form protons/neutrons (this forms the universe according to the theory).

5. Electromagnetic and weak atomic forces have separated.

6. Hydrogen and Helium nuclei formed

7. Electrons combine with nuclei and create whole H/He atoms.

8. Expansion and cooling continued and nuclear reactions stopped.

9. The universe became matter-dominated rather than radiation-dominated.

10. The radiation continued to cool as the universe expanded.

11. Matter in the universe formed clouds and groups of clouds that eventually collapsed to form galaxies and clusters of galaxies. In the galaxies were formed the stars, planets and other bodies.

THE END OF THE UNIVERSE

Basic question to such topic: Is the universe open or closed?

1. If the universe is “open” – it will have no definite end. It will just gradually dissipate as temperatures will continue to decline until they reach absolute zero. Hydrogen will be consumed by about 10 years after the birth of the universe and all the stars will burn out. Galaxies will disintegrate and their constituent stars will be lost to galactic space in 10 years.

2. If the universe is “closed” – some 50 billion years from now, it will stop expanding and start contracting. Galaxies will rush toward each other. The universe will once again become hot and compressed, entering a new singularity