Cosmology: Formation of the Solar System
How the Solar System Formed – Simple Explanation
How the Solar System Formed – More detailed Explanation
What do galaxies look like when they collide? - Great photo from the Hubble Space Telescope
Age of the Solar System
Here we are happily talking about the solar system being 4.5 billion years old, but how do we KNOW that the solar system is this old? What is the scientific evidence? The main evidence comes from radioactivity. A few elements are unstable and are likely to “decay” – that is, emit a particle and become a different element. For example, an isotope of potassium (potassium-40) decays to an isotope of argon (argon-40) with a half-life of 1.3 billion years. This means that 1 kilogram of pure potassium-40 would, over 1.3 billion years, turn into 1/2 a kilogram of argon-40 and 1/2 kilogram of remaining potassium-40. Then, another 1.3 billion years later, the 1/2 kilogram of potassium-40 reduces to 1/4 kilogram and another 1/4 kilogram of argon-40. Therefore, we can find out the age of a lump of rock by measuring the ratio of potassium-40 to argon-40
The oldest rocks on Earth are about 3.9 billions years old. There are not very many of such old rocks around since the surface of the Earth has been thoroughly resurfaced. The oldest lunar rocks are about 4.4 billion years old. The oldest rocks ever encountered are meteorites, some of which are as old as 4.6 billion years. These meteorite rocks are thought to have formed during the early condensation of the solar nebula. The planets formed about 0.1 billion (100 million) years later. So, the age of the Earth is probably close to about 4.5 billion years.
Earth: Measuring it, proving Heliocentrism, proving it rotates on axis…etc
Largest Hurricanes since 1900. Are there more hurricanes today than ever before?
Los Angeles Rainfall for the past 150 years. Is there less rain today than ever? What’s the trend?
The motion of the Sun and the Stars
Bad Astronomy: Misconceptions about Astronomy Answered
How Thick is the Earth’s “Skin” (atmosphere)
Sketch of moon going around earth as earth goes around sun. Shows Synodic Period (29.5 days) and Sidereal Period – true orbital period (27.3 days)
Earth and Moon
Daylight Savings Time Explained -Why do we change our clocks?
Eclipses – Solar and Lunar
Annular Eclipse of May 20, 2012 (5:30 – 7:30 PM local time) – Quicktime movie of eclipse occuring
Comet Hale Bopp – March 22nd was Closest to Earth. April 1st closest to sun
JPL Unmanned Missions
Article about the Vomit Comet – How to simulate Zero Gravity here on Earth.
Important People in Astronomy and Physics:
Eratosthenes (276BC-194BC) First to measure the circumference of the Earth
Ptolemy (85-165) Greek Astronomer who first proposes Geocentrism. It isn’t until Copernicus in the mid 1500’s do we question Geocentrism.
Copernicus (1473-1543) First proposes Heliocentrism
Galileo (1564-1642) Proves Heliocentrism by moons around Jupiter, Phases of Venus. Creates the concept of a pendulum clock.
Johannes Kepler (1571-1630) – Realizes that orbits are elliptical and determines a relationship between the period of rotation and distance from the sun.
Christiaan Huygens (1629-1695) Makes first pendulum clocks based on Galileo’s research
Newton (1642-1727) Father of Classical physics, and of calculus
John Harrison (1693-1776) Clock maker who basically invents the pocket watch. His watch can be used on ships to tell the time accurately so they can find their longitude.
Henry Cavendish (1731-1810) Solves the “Big G” constant problem posed by Newton in his Universal Gravitation equation. By solving “Big G”, the mass of the earth can be determined
Jean Bernard Leon Foucault (1819-1868) – Uses a pendulum to illustrate that the earth turns on its own axis
Albert Einstein (1879-1955) – Demonstrates that there are no forces holding the planets in orbit around the sun, rather the sun (and planets) cause a warping of space.
Philosophy of Science:
Teleological Argument – Design of nature leads one to believe there is an intelligent designer