Download Measuring Distances: Mph (miles per hour): miles traveled per hour

Unit 10: Light Years & Origins of the Universe Measuring Distances: Mph (miles per hour): miles traveled per hour Km/Hr: kilometers traveled in one hour; best unit to a drive or trip Knots: ;me it takes to travel 1 nau;cal mile per hour (nau$cal mile is longer than a land mile) Mach: an object’s speed divided by the speed of sound AU (Astronomical Unit): standard measurement for distances within our solar system (AU = 150,000,000 km – roughly the distance from Sun to Earth) -­‐ Mercury: .39 AU, Jupiter 5.2 AU, Pluto 39.9 AU Light year (symbol: ly): standard measurement for distances in space: DISTANCE (HOW FAR) light travels, at the SPEED OF LIGHT, (through a vacuum, like space) in 1 year; (1 ly = 10 trillion km) PS: SPEED OF LIGHT = roughly 300,000 km per second. Warp: doesn’t exist except on “Star Trek” – made up speed that is faster than the speed of light A light year is defined by how far a beam of light travels in one year (6 trillion miles / 10 trillion km). Proxima Centauri (our next closest star) is 4.2 light years (remember light year = distance) away from Earth. The light that le] Proxima Centauri today will take 4.2 years at the speed of light (remember speed of light = speed) to reach us on Earth, so we’d see it 4.2 years later. We are looking at the past. Light speed to the Moon takes about a 1 ½ seconds. Light speed to the Sun is roughly 8.33 minutes. ORIGIN OF THE UNIVERSE THEORIES: A theory is an explanaSon of things or events based on scienSfic knowledge. Theories are the most accepted explanaSon, based on informaSon from research. Theories can change if EVIDENCE supports the change. Theories about the origins of the universe include: Flat Earth Theory, Ptolemy Universe Theory, Copernicus Universe Theory, Kepler’s Universe Theory, Steady State Universe Theory, Big Bang Theory, Friedmann Universe Theory, Anthropic Universe theory, Infla$onary Universe Theory, No Boundary Universe Theory, and the Oscilla$ng Universe Theory. As our tools for studying the universe have improved, some of these theories have been disproved. The nature of a theory is that if new informaSon and data clarifies or disproves a theory, the theory can be changed. Without this ability to change as knowledge is gained, we would sSll believe the theory that the Earth is flat. The images and data collected from the space program disproved that theory. BIG BANG THEORY: is the most popular and widely accepted THEORY about the beginnings of the universe, and is supported by observa;onal evidence. A Belgian priest named Georges Lemaitre first suggested the Big Bang Theory when he theorized that the universe began from a single atom. Suppor;ng evidence was found in Albert Einstein’s Theory of RelaDvity, Edwin Hubble’s observaDons that galaxies are speeding away (RED-­‐SHIFTED=MOVING AWAY FROM US) from us in all direcDons, and from the discovery of cosmic microwave radiaDon by Arno Penzias and Robert Wilson. The Big Bang Theory developed from the observa;on that other galaxies are moving away from our own galaxy at great speed, in all direc;ons, as if they had all been propelled by an explosive force. THERE WAS NO EXPLOSION; there was and con;nues to be …an EXPANSION. Imagine a balloon: instead of a balloon popping and releasing all of its contents, the Big Bang theory is more like the balloon star;ng off as an extremely ;ny balloon and expanding to the size of our current universe. But un;l further evidence supports a change, the Big Bang Theory is the currently accepted one. WHEN WE LOOK AT THE NIGHT SKY, WE ARE LOOKING AT THE PAST: ScienDsts esDmate the universe is roughly 13-­‐14 billions years old. The light coming from the farthest depths of the universe has been traveling across the cosmos for almost three ;mes longer than our planet has existed. But there’s a catch: we cannot say that the edge of the visible universe is 14 billion light-­‐years away. Why? Because the universe has EXPANDED (RED-­‐SHIFTED) in that ;me! A galaxy whose light took 14 billion years to reach Earth has moved further away during the ;me it took for light to reach us. If we stopped the universe from expanding, it would be just over 46 billion light years across! And it’s genng bigger (expanding) every day.