The Big Bang Theory:

Origin & Evolution of the Universe

Su’dud Mayadmeh

Where did the Universe come from?Where is it going?How can we see the past?

How can we learn about the future from seeing the past?

Introduction

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Newton’s Static Universe Universe is static and composed of an

infinite number of stars that are scattered randomly throughout an infinite space.

rse is infinitely old and will exist forever without any major changes.

Time and Space are steady and independent of one another and any objects in existence within them.

Newton’s Error

If universe is as how Newton describes, then why is the sky dark at night?

Olber’s Paradox

If space goes on forever with stars scattered randomly throughout, then in any line of sight in any direction will eventually run into a star.

Using this logic, the sky should be the average brightness of all of these stars; the sky should be as bright as the sun, even at night.

But isn’t the sky dark at night?…

Yes, of course - that is what we observe now and have always observed.

Something is wrong with Newton’s idea of a static, infinite universe.

What is the Big Bang Theory?

The universe started as a single point.That point was extremely dense.

It became unstable and exploded outward.

Today the universe continues to expand

Time begins The universe begins

~13.7 Billion years ago

The universe begins as the size of a single atom

The universe began as a violent expansionAll matter and space

were created from a single point of pure energy in an instant

~3 minutes after big bang The universe has grown

from the size of an atom to larger than the size a grapefruit

E=mc2

energy froze into matter according to Albert Einstein’s equation.

This basically says that like snowflakes freezing, energy forms matter into clumps that today we call protons, neutrons and electrons.

These parts later form into atoms

http://www.colorado.edu/physics/2000/applets/doppler2.html

Universal expansion and Hubble’s Law

a) Hubble observed the majority of galaxies are moving away from us and each other

b) The farther, the faster they move

c) Red Shift

Galactic Red shifts Edwin Hubble (1889-1953) and colleagues

measured the spectra (light) of many galaxies found nearly all galaxies are red-shifted

Redshift (Z)

rest

rest

lll -

= observed Z

Andromeda galaxy

Z = [(1+ v/c)/(1+ v/c)]1/2 - 1

(Doppler Effect )Z=V/C

(For speed approaching Cwe’ll need a relativistic version

Of this equation).

Do you know what Red Shift is?

RedshiftQuasars &

Cosmology

Department of Physics, Applied Physics & Astronomy, RPI

In relativity the space between the galaxiesis expanding.

Hubble’s Law

Galaxies are moving away from us.

The farther away the faster they go.

V = Ho x Dv = recessional velocity of the galaxyH0 = Hubble constantD = distance of galaxy to earth

Hubble’s Constant Expansion rate measured using Type 1A

Supernovae. The age of the universe can be derived

from Hubble’s constant:○ T0 = d T0 = 1

H0d H0

For example, if H0 = 73 km/s*Mpc, then

T0 = 13.4 Billion years old

Evidence for Expansion

The light from remote galaxies and other objects is red shifted.

This red shift is called cosmological red shift because it is caused by the expansion of the universe, not by the actual movement of the object (doppler red shift).

If galaxies are all moving away, then at some point they were all much closer.Hubble’s Law implies the Universe is expanding.

Three Pieces of Evidence Supporting the Big Bang

The observation of the galaxies spreading away from the center of the universe (Red Shift)

The presence of Background Radiation

Heat in space 3°K

Center of Universe?

There is NO CENTER to the universe Expansion looks the same regardless of

where you are in the universe. Every point appears to be the center of the

expansion, therefore no point is the center. The universe is infinite.

What Happens Next?

Astronomers feel that the Big Bang theory leads to two possible futures for the Universe.

Open Universe

Galaxies will continue racing outward (continue to expand). All of the stars will die off as the last of their energy is released. There will be nothing left, total emptiness

Gravitational attraction between the galaxies will cause the movement away from each other to slow and, eventually come to a halt. The gravitational pull will begin to pull the galaxies back to the center of the universe

Closed Universe

The Shape of the UniverseAccording to Einstein, mass bends space. This means that the universe has a shape. This shape is related to

the density of the universe.

Type Shape of Universe

Open Universe

Closed Universe

Flat Universe

Cosmic Background Radiation

Discovered in 1965 Discovered by Arno Penzias & Robert

Wilson Their radio telescope detected faint

radiation coming from all directions Now believed to be leftover thermal

energy from the big bang

Cosmic Background Radiation (or CBR)

George Gamow, Ralph Alpher and Robert Herman (1948) suggested that the Universe should have been filled with radiation shortly after the Big Bang. A remnant of this radiation should still be detectable today as low intensity background microwaves.

•In an expanding Universe, the wavelength of radiation from the Big Bang would also expand, becoming red shifted and cooled.

Therefore, we should be able to detect the red shifted cooled-off remnant of the Big Bang explosion all around us (pervading the entire Universe)!

Furthermore, the remnant of the Big Bang explosion should have a blackbody spectrum.

Not The EndJust out of

time

LASTLY – we are pretty sure everything has a beginning, right?

To be continue…