scales in space and time in the cosmos by dr. harold williams of montgomery college planetarium
TRANSCRIPT
Realms of the UniverseSize and Scale of the Universe
Image courtesy of The Cosmic Perspective by Bennett, Donahue, Schneider, & Voit; Addison Wesley, 2002
16 x 16 m
A Campus Scene
1 mile x 1 mile
A City View
100 miles x 100 miles
The Landscape of Pennsylvania
Diameter of the Earth: 12,756 km
Earth
Distance Earth – Moon: 384,000 km
Earth and Moon
Distance Sun – Earth = 150,000,000 km
Earth orbiting around the Sun
Approx. 100 AU
The Solar System
The speed of light: c = 3x105 km/s.
Source Distance (km) Light Travel time London 6,000 0.02 s Moon 385,000 1.3 s Sun 1.5 x 108 500 s (8.3 min) Jupiter 7.8 x 108 43 min Nearest Star 4 x 1013 4.3 years Most Distant Galaxy 1.4 x 1023 14 billion years
Whenever you see "light-(time)", that means we are talking about distance, not time.
1 light year = 10 trillion km
Survey Question Sound 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.
Survey Question
If 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 away
2) 14 billion light-years away
3) 14 billion years away
4) there is no limit – if we look hard enough, we will see all objects.
Approx. 10,000 AU
(Almost) Empty Space Around our Solar System
Approx. 17 light years
The Solar Neighborhood
The Solar NeighborhoodNew distance scale:
1 light year (ly) =
Distance traveled by light in 1 year
= 63,000 AU = 1013 km
= 10,000,000,000,000 km
(= 1 + 13 zeros)
= 10 trillion km
Nearest star to the Sun:
Proxima Centauri, at a distance of 4.2 light years
Approx. 17 light years
Approx. 1,700 light years
The Extended Solar Neighborhood
How big is a million, billion, trillion, etc. anyway?
1 million seconds ago = 12 days ago
1 billion seconds ago = 31 years ago
1 trillion seconds ago = 31,688 years ago
Diameter of the Milky Way: ~ 75,000 ly
The Milky Way Galaxy
Distance to the nearest large galaxies: several million light years
The Local Group of Galaxies
Large-Scale Structure
Distribution of bright galaxies in the Virgo region indicates the Virgo cluster and presence of more distant, larger scale structure
A Sense of Time
If 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.
Optical Sky
Near-infrared sky
Boldt et al.
Radio Sky
Soft X-ray Sky
Gamma-ray all-sky map
Fermi Gamma-ray Space Telescope
Scientific Notation Video
• http://www.teachertube.com/viewVideo.php?video_id=119236
• http://htwins.net/scale2/