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Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
Distance Ladder
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Distance Ladder

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The Transit of Venus and the understanding of Distances in the Universe

The Transit of Venus and the understanding of Distances in the Universe

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  • For the time, the stadion was the current large unit of measure equal to 600 feet. A standing army was expected to march 100 stadia in a day (or about 11 miles). Alexander’s armies could march 13, while the cavalry could ride 40.
  • From a 10th century manuscript
  • Transcript

    • 1. Distance Ladder 2012-Apr-13 mississauga.rasc.ca
    • 2. How far is it to the Moon, Planets Sun? How far to the nearest stars? How far to Galaxies? How big is the Universe? How old is the Universe? 2012-Apr-13 mississauga.rasc.ca
    • 3. Moon, Nearest Milky Nearby GalaxyPlanets, Stars Way Galaxies Clusters Sun Closer Farther 2012-Apr-13 mississauga.rasc.ca
    • 4. Moon, Planets, Sun Nearest Stars Milky Way Nearby Galaxies Galaxy Clusters [RADAR] [Parallax] [Main Sequence [Cepheids] [White Dwarf Fitting] Supernovae] Trigonometry Luminosity-Temperature-Distance Tully-Fisher, et al. Redshifts 2012-Apr-13 mississauga.rasc.ca
    • 5. Moon, Planet Nearest Stars Milky Way Nearby Galaxy s, Sun Galaxies Clusters [Parallax] [Main [RADAR] Sequence [Cepheids] [White Dwarf Fitting] Supernovae] Trigonometry Luminosity-Temperature-Distance Tully-Fisher, et al. Redshifts 2012-Apr-13 mississauga.rasc.ca
    • 6. • Multiples of Feet!• Probably first derived guess Eratosthenes (200s BCE)• Calculated 40,000 stadia• Or 6,280 km – 8,360 km (based on different standard feet in the Ancient World)• Land/sea/air/space based trigonometric measurements mean radius of 6,371 km 2012-Apr-13 mississauga.rasc.ca
    • 7. 2012-Apr-13 mississauga.rasc.ca
    • 8. 2012-Apr-13 mississauga.rasc.ca
    • 9. Moon, Nearest Stars Milky Way Nearby GalaxyPlanets, Sun Galaxies Clusters [Parallax] [Main [RADAR] Sequence [Cepheids] [White Dwarf Fitting] Supernovae] Trigonometry Luminosity-Temperature-Distance Tully-Fisher, et al. Redshifts 2012-Apr-13 mississauga.rasc.ca
    • 10. 2012-Apr-13 mississauga.rasc.ca
    • 11. 2012-Apr-13 mississauga.rasc.ca
    • 12. 2012-Apr-13 mississauga.rasc.ca
    • 13. Moon, Nearest Milky Way Nearby GalaxyPlanets, Sun Stars Galaxies Clusters [Main [RADAR] [Parallax] Sequence [Cepheids] [White Dwarf Fitting] Supernovae] Trigonometry Luminosity-Temperature-Distance Tully-Fisher, et al. Redshifts 2012-Apr-13 mississauga.rasc.ca
    • 14. 2012-Apr-13 mississauga.rasc.ca
    • 15. Moon, Nearest Milky Way Nearby GalaxyPlanets, Sun Stars Galaxies Clusters [Main [RADAR] [Parallax] Sequence [Cepheids] [White Dwarf Fitting] Supernovae] Trigonometry Luminosity-Temperature-Distance Tully-Fisher, et al. Redshifts 2012-Apr-13 mississauga.rasc.ca
    • 16. 2012-Apr-13 mississauga.rasc.ca
    • 17. 2012-Apr-13 mississauga.rasc.ca
    • 18. Moon, Pl Nearest Milky Nearby Galaxy anets, S Stars Way Galaxies Clusters unkm Astronomical U Light Year Mega Parsec 2012-Apr-13 mississauga.rasc.ca
    • 19. • AU Astronomical Unit is approximately the mean distance from the center of the Sun to the center of the Earth (~150,000,000 km)• ly Light-Year is the distance light travels in a vacuum in a Julian year (~10 trillion km)• pc A parsec is the distance from the Sun to a parallax-arc-second displaced object (3.26 ly or ~31 trillion km)• Mpc A Mega parsec is 3,261,000 ly 2012-Apr-13 mississauga.rasc.ca
    • 20. • Voyager 1 is about 116 AU away• Proxima Centauri is about 4.2 ly away• the Pleiades are about 120 pc away• the Milky Way is about 30 kpc across• Andromeda Galaxy is 800 kpc away• the Virgo Cluster is about 16.5 Mpc• the boundary of the observable universe has a radius of about 14 Gpc 2012-Apr-13 mississauga.rasc.ca
    • 21. • You need to get the AU right• Used to be only visual observation of the Venus Transit and very good mathematics could do it• Now there is RADAR of Venus and Mars, but that still requires very good “radio” observation and mathematics 2012-Apr-13 mississauga.rasc.ca
    • 22. • A 0.0005% error in the angular measurement of the Transit of Venus means a 1% error in the AU and a 1% error in a parsec (or 2062.56 AU)• A 1% error in distance at the Cepheid stage represents a 2.3% error in the Luminosity difference• This carries through to the expansion number 2012-Apr-13 mississauga.rasc.ca
    • 23. • Our measurements of the Transit of Venus are key to understanding the distance of the AU• This gives us a good value for a parsec• Which in turn helps us figure out luminosity and distance of stars in the Milky Way• Helping us to find where Cepheid are and how far away close Galaxies are• Which in turn helps us understand the expansion of the Universe! 2012-Apr-13 mississauga.rasc.ca
    • 24. The Transit of Venus is Very Important 2012-Apr-13 mississauga.rasc.ca

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