02_bigbang - UCSD Physics 10 Out Into the Universe An...

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UCSD Physics 10 Out Into the Universe Out Into the Universe An overview of the cosmos: An overview of the cosmos: What’s out there? What’s out there? How big is it? Is it getting bigger? How big is it? Is it getting bigger?
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Spring 2008 2 UCSD Physics 10 Beyond Our Comfort Zone Beyond Our Comfort Zone Direct Experience: 10 Direct Experience: 10 -5 -5 to 10 to 10 5 meters meters Dust grain may have 0.01 mm = 10 micron diameter View from mountaintop may extend 100 km Experts” may claim comfort with 10 Experts” may claim comfort with 10 -7 -7 to 10 to 10 7 m m Optical surfaces are smoother than wavelength of light Earth diameter about 12,750 km Scientists today deal with much larger ranges Scientists today deal with much larger ranges Particle physics probes 10 -18 m scales Visible Universe spans 10 26 m Theorists stop at “Planck scale”; 10 -35 m
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Spring 2008 3 UCSD Physics 10 Graphical Logarithmic Representation Graphical Logarithmic Representation of the Physical Scales in our Universe of the Physical Scales in our Universe -30 -20 -10 0 10 20 Comfort Zone Planck Scale Current Experimental Limit Proton Atom Cell Phys 10 Student State Distance To Sun To Nearest Star Milky Way Visible Universe means 10 -30 meters Does it even mean anything to look beyond the scales represented here? This may be all that matters!
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Spring 2008 4 UCSD Physics 10 Outward Journey Outward Journey The logarithmic scale is deceptively compact The logarithmic scale is deceptively compact We think linearly, because that’s how we perceive time Now let’s imagine the universe in linear terms… We use the speed of light to express large distances We use the speed of light to express large distances c = 300,000,000 m/s: 1 light second = 3 × 10 8 meters 1 light year is about 10 16 meters 1 yr is about π× 10 7 seconds (actually 3.15576 × 10 7 s) Imagine how far you could walk in a given amount Imagine how far you could walk in a given amount of light travel-time of light travel-time Puts things into a familiar context Gadzooks, the Universe is big!
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Spring 2008 5 UCSD Physics 10 Outward Journey; Solar System Outward Journey; Solar System The moon is 385,000 km away The moon is 385,000 km away 1.25 light seconds Walk about 2 meters in this time: Across a small room Note: Deceiving perspective. The moon is about 30 earth-diameters away from earth. Photo from Galileo spacecraft (NASA).
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This note was uploaded on 02/12/2012 for the course PHYSICS 104 taught by Professor Staff during the Fall '10 term at Rutgers.

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02_bigbang - UCSD Physics 10 Out Into the Universe An...

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