The Origin

• In late 1920's, the American astronomer Edwin Hubble made observations that distant stars and galaxies are receding from earth in every direction.
• The velocities of recession increase in proportion with distance that implied the universe is expanding is predicted by Eintein's Theory of General Relativity
• The Big Bang - a big explosion discharging matter and energy in all directions that occurred 13.8 billion years ago.
• The diameter of the Earth is infinite but should be at least 91 billion light-years
• 1 light-year = 9.4607 x 10^12 km
• the density of the universe = 4.5 x 10^-31 g/cm^3
• The most abundant elements in the universe are hydrogen, helium and litium.
• Helium makes up about 25% of the mass of the universe
• Hydrogen makes up about 75% of the mass of the universe
• Litium makes up less than 1% of the mass of the universe
• Stars - the building blocks of galaxies
• Stars - born out of clouds of gas and dust in galaxies.
• Protostar - it is formed from the instabilities within clouds that eventually result in gravitational collapse, rotation, heating, and its transformation
• protostar - the hot core of a future star as thermonuclear reactions sets in.
• Galaxy - cluster of billions of stars
• Superclusters - clusters of galaxies
• The Universe comprises all space and time, and all the matter and energy in it.
• The universe is made of 4.6% baryonic matter, 24% cold dark matter, and 71.4 dark energy.
• baryonic matter is also known as ordinary matter such as protons neutrons and electrons
• cold dark matter - it is a matter that has gravity but does not emit light
• dark energy is a source of anti-gravity
• Dark matter is composed of particles that do not absorb, reflect, or emit light, so they cannot be detected by observing electromagnetic radiation.
• 3.8 billion years ago, life took root on Earth
• The solar system comprises the sun, eight planets, dwarf planets, asteroids, comets and other bodies
• The asteroid belt lies between Mars and Jupiter
• Meteoroids are smaller asteroids.
• Meteoroids - thought of as remnants of a failed planet or one that did not form dues to the disturbance from JUpiter's gravity.
• Kuiper belt lies beyond Neptune and comprises numerous rocky or icy bodies a few meters to hundreds of kilometers in size.
• Oort cloud marks the boundary of the solar system and is composed of mostly icy objects
• The age of the solar system is at 4.6 billion years old based on the radioactive dating of meteorites
• Solar system is much younger than the Universe
• Our solar system is located in the milky Way galaxy, which is about 100 million light-years accross
• Milky way has an estimated 200 billion stars
• The solar system revolves around the galactic center once in about 240 million years
• All planets revolve around the Sun
• Orbits of the planets are elliptical and are on the same plane.
• Much of the mass of the Solar System is concentrated at the Sun, while the outer planets hold angular momentum
• The innermost planet moves fastest, the outermost, moves the slowest
• The periods of revolution of the planets increase with the increasing distance from the sun
• All planets are located at regular intervals from the Sun