Phenomena

LIGHT

BLACK BODY RADIATION

DARK MATTER

Theories

BIG BANG

BIG CRUNCH

EXPANSION OF THE UNIVERSE

Age of the Universe

The age of the Universe is 13.75 billion years old. People long thought the Universe as much younger— millions, let alone billion of years old. Edwin Hubble’s observations in the 1920s showed that the Universe has a finite age. Using Doppler Shift, Hubble discovered that the Universe was expanding. Every galaxy seemed to be moving away from each other, showing red shifts in their spectral lines. In 1958, Allan Sandage made the first calculation of a value called the Hubble’s constant, which determines the rate of the Universe’s expansion. With the Hubble’s constant, Sandage made the first accurate (closer than before) estimate of the age of the Universe at ~20 billion years. Discovered in 1965, the microwave cosmic background radiation, a remnant of the Big Bang, confirmed the expanding Universe theory. As the Universe expanded, it gradually cooled. The  CBR shows the Universe at 2.7 K. In fact, scientists have recently discovered dark energy. Dark energy accelerates the expansion of the Universe, reducing earlier estimates of >14 billion years to 13.75 billion years.

Early Formation Theories

Vortex Theory (1664 – René Descartes); Catastrophe Theory (1745 – Comte de Buffon); Tidal Theory; Nebular Hypothesis (1775 – Immanuel Kant, 1796 – Marquis Pierre Simmon de Laplace); Nebular Theories

Nebular Theory

1. Gas clouds
2. Small spin
3. Shape down
4. Gravitational contraction
5. Accretion
6. Protoplanets
7. Contraction of protosun

Extra-Solar Planets

Planets outside of the Solar System are detected by wobble in the star’s orbit and small changes in stars’ brightness and gravitational lensing of a closer star can detect earth-size planets.