BIG BANG THEORY

Big Bang Theory The theory that all matter and energy in the universe was compressed into an extremely small volume. 13.7 billion years ago a sudden event began expanding matter and energy in all directions

Universe The study of the universe is called cosmology. Cosmologists study the structure and changes in the present universe. The universe contains all of the star systems, galaxies, gas and dust, plus all the matter and energy that exist. The universe also includes all of space and time.

Evolution of human understanding of the universe 4th century BCE—Aristotle proposes a Geocentric (Earth-centered) universe in which the Earth is stationary and the cosmos (or universe) revolves around the Earth. 2nd century AD—Ptolemy proposes an Earth-centered universe, with the Sun, moon, and visible planets revolving around the Earth. 1543—Nicolaus Copernicus publishes his heliocentric (Sun-centered) universe theory. 1610—Johannes Kepler proposes the planets moved around the sun in elliptical orbits. 1687—Sir Isaac Newton's laws describe large-scale motion throughout the universe. 1915—Albert Einstein publishes the General Theory of Relativity, showing that an energy density warps space and time 1929—Edwin Hubble demonstrates redshift and thus shows the expansion of the universe.

Hubble’s Discoveries Hubble realized that many of the objects that astronomers called nebulas were not actually clouds of gas, but were collections of millions or billions of stars —what we now call galaxies. Hubble showed that the universe was much larger than our own galaxy. Today, we know that the universe contains about a hundred billion galaxies—about the same number of galaxies as there are stars in the Milky Way Galaxy.

Hubble’s Observations Light given off by an entire galaxy can be used to create a light spectrum. Edwin Hubble found that the spectra of galaxies were shifted toward the red end of the spectrum. Hubble found that the most distant galaxies showed the greatest red shift. Telescopes today confirm Hubble’s original findings.

Doppler effect-Red Shift A star moving away from Earth has a spectrum that is shifted slightly toward red. This shift occurs because the wavelengths of light appear to be longer as the star moves away from Earth.

Doppler effect-Blue Shift The colors in the spectrum of a star moving toward Earth are shifted slightly toward blue. This shift occurs because the light waves from a star appear to have shorter wavelengths as the star moves toward Earth.

Cosmic Microwave Background Radiation Low levels of energy evenly distributed throughout the universe Detected by radio telescopes in 1965 The Big Bang theory predicts that the early universe was a very hot place and that as it expands, the gas within it cools. Thus the universe should be filled with radiation that is literally the remnant heat left over from the Big Bang, called the “cosmic microwave background radiation”, or CMB.

Expanding Universe As the universe expanded some of the matter gathered into clumps that evolved into galaxies. The universe is still expanding today.