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/