Post on 02-Oct-2020
Size and Scale of the Universe
SIZEANDSCALEOFTHEUNIVERSE
WHAT IS YOUR COSMIC ADDRESS?
Size and Scale of the Universe
# Street
City
State
Country
Continent
Hemisphere
Planet
Orbit
Star?
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REALMS OF THE UNIVERSESize and Scale of the Universe
Image courtesy of The Cosmic Perspective by Bennett, Donahue, Schneider, & Voit; Addison Wesley, 2002
EARTHSize and Scale of the Universe
• Planet comprised primarily of rock
• Spherical • 12,700 km
diameter
Image Credit: NASA/JPL/GSFC
SUNSize and Scale of the Universe
• The star that Earth orbits
• Composed primarily of hydrogen and helium gas
• Spherical • 1.39 million km
diameter
Image Credit: SOHO/NASA/ESA
Calculations
If the room were the sun, how big would Earth be?
room's diameter (10 m)sun's diameter (1,390,000 km)
=x
Earth's diameter (12,700 km)
0.0914 m = 9.14 cm diameter(a wiffle ball)
THE SOLAR SYSTEMSize and Scale of the Universe
• 8 planets, several dwarf planets, thousands of asteroids, and trillions of comets and meteoroids
• Mostly distributed in a flat disk • Heliosphere: The boundary
between the Solar Wind (constant wind of charged gas from the sun) and interstellar space
Image credit: N
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Image credit: N
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CalculationsIf the room were the solar system, how big would the sun be?
room's diameter (10 m)solar system (3.0×1010 km)
=x
sun's diameter (1.39×106 km)
0.000463 m = 0.46 mm diameter(a grain of salt)
CalculationsIf the room were the solar system, how big would Earth’s orbit be?
0.1 m = 10 cm diameter(a roll of masking tape)
room's diameter (10 m)solar system (3.0×1010 km)
=x
Earth's orbit (3.0×108 km)
CalculationsIf the room were the solar system, how big would Earth be?
0.000004 m = 4 μm diameter(a microscopic bacteria)
room's diameter (10 m)solar system (3.0×1010 km)
=x
Earth's diameter (12, 700 km)
THE SOLAR NEIGHBORHOOD
Size and Scale of the Universe
• Region of the Galaxy within about 20 light-years of the Sun (40 light-years diameter)
• Neighborhood stars generally move with the Sun in its orbit around the center of the Galaxy
• The ‘Solar Neighborhood’ is a vague term (not scientifically defined)
Image credit: Andrew Colvin
CalculationsIf the room were the solar neighborhood, how big would the solar system be?
0.0008 m = 0.8 mm diameter(a grain of salt)
room's diameter (10 m)solar neighborhood (40 ly)
=x
solar system (3.2×10−3 ly)
THE MILKY WAY GALAXYSize and Scale of the Universe
• A giant disk of stars 100,000 light-years across and 1,000 light-years thick
• The Sun is located at the edge of a spiral arm, 30,000 light-years from the center
• Over 200 billion stars in the Milky Way
Image credit: R. Hurt (SSC), JPL-Caltech, NASA
CalculationsIf the room were the Milky Way Galaxy, how big would the solar neighborhood be?
0.004 m = 4 mm diameter(a peppercorn)
room's diameter (10 m)Milky Way (100, 000 ly)
=x
solar neighborhood (40 ly)
THE LOCAL GROUP(OF GALAXIES)
Size and Scale of the Universe
• Contains 3 large spiral galaxies (Milky Way, Andromeda(M31), Triangulum(M33), plus a few dozen dwarf galaxies with elliptical or irregular shapes)
• Gravitationally bound together—orbiting about a common center of mass
• Roughly shaped like a football
Image Credit: Andrew Colvin
CalculationsIf the room were the Local Group, how big would the Milky Way be?
0.154 m = 15.4 cm diameter(a small paper plate)
room's diameter (10 m)Local Group (6.5×106 ly)
=x
Milky Way (100, 000 ly)
THE LOCAL SUPERCLUSTERSize and Scale of the Universe
• About 130 million light-years across
• Huge cluster of thousands upon thousands of galaxies
• Clusters and groups of galaxies are gravitationally bound together, but spread away from each other as the Universe expands
• Roughly pancake shaped
Image credit: Andrew Colvin
CalculationsIf the room were the Local Supercluster, how big would the Local Group be?
0.5 m = 50 cm diameter(an XL pizza)
room's diameter (10 m)Local Supercluster (1.3×108 ly)
=x
Local Group (6.5×106 ly)
CalculationsIf the room were the Local Supercluster, how big would the Milky Way be?
0.008 m = 8 mm diameter(width of a paper clip)
room's diameter (10 m)Local Supercluster (1.3×108 ly)
=x
Milky Way (100, 000 ly)
THE UNIVERSE(THE OBSERVABLE PORTION)
Size and Scale of the Universe
• Great walls and filaments of galaxy clusters surrounding voids containing no galaxies
• At least 100 billion galaxies in the Universe (probably)
Image Credit: Dr Chris Fluke, Centre for Astrophysics and Supercomputing, Swinburne University of Technology
Image Credit: G.L. Bryan, M. L. Norman, UIUC, NCSA, GC3
• Surveys of galaxies reveal a web-like or honeycomb structure to the Universe
• Computer simulations show the “Cosmic Web”
Size and Scale of the Universe
THE UNIVERSE(THE OBSERVABLE PORTION)
Image Credit: Springer et al (2004)
• The Observable Universe is currently about 91 billion light-years across
• There could be (and likely is) much more beyond that, but we cannot see it from this point in spacetime
Size and Scale of the Universe
RealmActual Size
(diameter in km)Actual Size (in light-years)
Multiple “X” larger than Earth
Scale Model
Earth
Sun
Solar System
Solar Neighborhood
Galaxy
Local Group (of galaxies)
Local Supercluster
Universe
1.27x104 1.4x10-9 1 salt grain (0.1 mm)
1.39x106 1.5x10-7 1.09x102 marble (1.09 cm)
3.0x1010 3.2x10-3 2.34x106 football stadium(234 meters)
3.78x1014 4.0x101 3.0x1010 ~ size of Moon(3,480 km)
9.46x1017 1.0x105 7.5x1013 5.4 Suns (7.5 million km)
6.15x1019 6.5x106 4.8x1015 orbit of Mars -diameter(~3 AU)
1.2x1021 1.3x108 9.7x1016 orbit of Neptune -diameter(~60 AU)
8.6x1023 9.1x1010 6.8x1019 Oort Cloud-radius (48,000 AU or 0.76
ly)
CalculationsIf the room were the observable universe, how big would the Local Supercluster be?
0.014 m = 1.4 cm diameter(a marble)
room's diameter (10 m)observable universe (9.1×1010 ly)
=x
Local Supercluster (1.3×108 ly)
CalculationsIf the room were the observable universe, how big would the Local Group be?
0.0007 m = 0.7 mm diameter(a grain of salt)
room's diameter (10 m)observable universe (9.1×1010 ly)
=x
Local Group (6.5×106 ly)