Presentation on theme: "Scales in Space and Time in the Cosmos"— Presentation transcript:
1Scales in Space and Time in the Cosmos By Dr. Harold Williamsof Montgomery College PlanetariumTitle slide
2The Scale of the CosmosAstronomy deals with objects on a vast range of size scales and time scales.Most of these size and time scales are way beyond our every-day experience.Humans, the Earth, and even the solar system are tiny and insignificant on cosmic scales.
3Size and Scale of the Universe Realms of the UniverseImage courtesy of The Cosmic Perspective by Bennett, Donahue, Schneider, & Voit; Addison Wesley, 2002
11The speed of light: c = 3x105 km/s. Source Distance (km) Light Travel timeLondon 6, sMoon , sSun x s (8.3 min)Jupiter x minNearest Star 4 x yearsMost Distant Galaxy 1.4 x billion yearsWhenever you see "light-(time)", that means we are talking about distance, not time.1 light year = 10 trillion km
12Survey QuestionSound travels at a speed of 300 meters per second. In analogy to the light-year, what does 1 sound-minute equal?The time sound takes to travel 300 meters.The time delay of a sound heard 300 meters away.The distance traveled by sound in 1 minute.The speed of sound 1 minute later.
13Survey QuestionIf the Universe is infinite in size and 14 billion years old, the most distant object that we could ever hope to see is:1) 100,000 light-years away2) 14 billion light-years away3) 14 billion years away4) there is no limit – if we look hard enough, we will see all objects.
14(Almost) Empty Space Around our Solar System Approx. 10,000 AU
16The Solar Neighborhood New distance scale:1 light year (ly) =Distance traveled by light in 1 year= 63,000 AU = 1013 km= 10,000,000,000,000 km(= zeros)= 10 trillion kmNearest star to the Sun:Proxima Centauri, at a distance of 4.2 light yearsApprox. 17 light years
17The Extended Solar Neighborhood Approx. 1,700 light years
20To get another sense of this… If Earth were a golf ball, the sun would be 15 meters wide.You would be able to fit 960,000 Earths (almost a million) in the Sun…With 1 million golf balls, you would be able to fill an entire school bus with nothing but golf balls!
22Betelguese is 2x the Earth’s orbit around the Sun! If Earth were a golf ball, Betelguese would be the size of 6 Empire State buildings stacked one on top of the other…You could fit 262 trillion Earth’s in Betelgeuse…If you had that many golf balls, you would fill the super bowl dome with golf balls.
23How big is a million, billion, trillion, etc. anyway? 1 million seconds ago = 12 days ago1 billion seconds ago = 31 years ago1 trillion seconds ago = 31,688 years ago
24Mu Cephei…If Earth were a golf ball…. Mu Cephei would be the size of two Golden Gate Bridges!You could fit 2.7 quadrillion Earth’s..Canis MajorisIf earth were a golf ball… Canis Majoris would be the height of Mount Everest!!You could fit 7 quadrillion Earths….That is enough golf balls to cover the entire state of Texas with golf balls… 22 inches deep.
25Diameter of the Milky Way: ~ 75,000 ly The Milky Way GalaxyDiameter of the Milky Way: ~ 75,000 ly
29Large-Scale Structure Distribution of bright galaxies in the Virgo region indicates the Virgo cluster and presence of more distant, larger scale structure
30The Universe on Very Large Scales Clusters of galaxies are grouped into superclusters.Superclusters form filaments and walls around voids.
31Large-Scale Structure A large survey of distant galaxies shows the largest structures in the universe:Filaments and walls of galaxy superclusters, andvoids, basically empty space.
32Cosmology with the Cosmic Microwave Background If the universe was perfectly homogeneous on all scales at the time of reionization (z = 1000), then the CMB should be perfectly isotropic over the sky.Instead, it shows small-scale fluctuations:
33Measuring the “Deceleration” of the Universe … By observing type Ia supernovae, astronomers can measure the Hubble relation at large distancesDistance recession speedSize scale of the universe rate of expansionIt was expected that this would measure the deceleration of the universe, but …
34The Accelerating Universe Flat decelerating universeApparent Magnitude of Type Ia SupernovaeFlat accelerating universeRed Shift zIn fact, SN Ia measurements showed that the universe is accelerating!
35A Sense of TimeIf we were to compress the time since the Big Bang into one year, and make the time of the Big Bang January 1,The Earth was formed in mid-September.The mammals appeared on December 26.All human prehistory (from the first known stone tools) and history have occurred in the last ½ hour of New Year's Eve.All of human history is but a fleeting instant on the cosmic timescale.