Goal to understand the scale of the universe Objectives: 1) To explore our local part of space called the Solar System. 2) To understand the distances between stars. 3) To understand the sizes of galaxies 4) To learn about the local group 5) To learn about the distances to galaxy clusters 6) To scale down the observable universe First, the overall size • 100000000000000000000000000000 m • 1026 m, 13 billion light years The Earth • 8000 miles in diameter. • 25000 miles in circumference. • Our moon is 250,000 miles away. Solar system • Our sun is on average 93 million miles • (1 Astronomical Unit, or AU) • Sun itself 800,000 miles in diameter. • If our sun were a small marble, 1 cm in diameter, the earth would be the width of a human hair located a distance of 1.16 m from the sun. • Neptune, the furthest planet at 30 AU, would be 35 m away from the marble that is our sun. Nearest star to sun • Alpha Centauri Proxima (red dwarf) – 4.2 light years • If sun was a marble (1cm) Alpha Centauri would be 312 km away (about Chicago). 400 light years 1500 Light Years http://www.ldps.ws/Mirror/Universe/galaxy.html The math • If the distance from our sun to Alpha Centauri Proxima were 1 cm the diameter of our galaxy would be about 240 m and would have a thickness of about 5 m. • Our galaxy has about 400 billion stars and a mass of about 1 trillion solar masses (1 solar mass = mass of our sun) Local group http://www.anzwers.org/fr ee/universe/ Local Group • If the diameter of our milky way were reduced to the size of a small marble: • Andromeda Galaxy (nearest spiral) would be 20 cm away. • Entire local group would have a radius of about 30 cm (1 foot) Nearby region of the universe 1 billion light years Universe What does that mean? • If our galaxy were a marble (1 cm in diameter) then the observable universe would be 1.3 km in diameter • Suppose we wanted to travel there? • It would take tens of billions of years Earth time each way. • 100 billion galaxies in universe. http://htwins.net/scale2/ Conclusion • • • • The universe is a really huge place. Distances between stars is huge. Galaxies are huge. Distance between galaxies are huge.