# Scales in Space and Time in the Cosmos

## Presentation on theme: "Scales in Space and Time in the Cosmos"— Presentation transcript:

Scales in Space and Time in the Cosmos
By Dr. Harold Williams of Montgomery College Planetarium Title slide

The Scale of the Cosmos Astronomy deals with objects on a vast range of size scales and time scales. Most of these size and time scales are way beyond our every-day experience. Humans, the Earth, and even the solar system are tiny and insignificant on cosmic scales.

Size and Scale of the Universe
Realms of the Universe Image courtesy of The Cosmic Perspective by Bennett, Donahue, Schneider, & Voit; Addison Wesley, 2002

A Campus Scene 16 x 16 m

A City View 1 mile x 1 mile

The Landscape of Pennsylvania
100 miles x 100 miles

Diameter of the Earth: 12,756 km

Distance Earth – Moon: 384,000 km
Earth and Moon Distance Earth – Moon: 384,000 km

Distance Sun – Earth = 150,000,000 km
Earth orbiting around the Sun Distance Sun – Earth = 150,000,000 km

The Solar System Approx. 100 AU

The speed of light: c = 3x105 km/s.
Source Distance (km) Light Travel time London 6, s Moon , s Sun x s (8.3 min) Jupiter x min Nearest Star 4 x years Most Distant Galaxy 1.4 x 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.

(Almost) Empty Space Around our Solar System
Approx. 10,000 AU

The Solar Neighborhood
Approx. 17 light years

The Solar Neighborhood
New distance scale: 1 light year (ly) = Distance traveled by light in 1 year = 63,000 AU = 1013 km = 10,000,000,000,000 km (= zeros) = 10 trillion km Nearest star to the Sun: Proxima Centauri, at a distance of 4.2 light years Approx. 17 light years

The Extended Solar Neighborhood
Approx. 1,700 light years

To get another sense of this…
If Earth were a golf ball, the sun would be 15 meters wide. You would be able to fit 960,000 Earths (almost a million) in the Sun… With 1 million golf balls, you would be able to fill an entire school bus with nothing but golf balls!

Betelguese is 2x the Earth’s orbit around the Sun!
If Earth were a golf ball, Betelguese would be the size of 6 Empire State buildings stacked one on top of the other… You could fit 262 trillion Earth’s in Betelgeuse… If you had that many golf balls, you would fill the super bowl dome with golf balls.

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

Mu Cephei… If Earth were a golf ball…. Mu Cephei would be the size of two Golden Gate Bridges! You could fit 2.7 quadrillion Earth’s.. Canis Majoris If earth were a golf ball… Canis Majoris would be the height of Mount Everest!! You could fit 7 quadrillion Earths…. That is enough golf balls to cover the entire state of Texas with golf balls… 22 inches deep.

Diameter of the Milky Way: ~ 75,000 ly
The Milky Way Galaxy Diameter of the Milky Way: ~ 75,000 ly

Distance to the nearest large galaxies: several million light years
The Local Group of Galaxies Distance to the nearest large galaxies: several million light years

Large-Scale Structure
Distribution of bright galaxies in the Virgo region indicates the Virgo cluster and presence of more distant, larger scale structure

The Universe on Very Large Scales
Clusters of galaxies are grouped into superclusters. Superclusters form filaments and walls around voids.

Large-Scale Structure
A large survey of distant galaxies shows the largest structures in the universe: Filaments and walls of galaxy superclusters, and voids, basically empty space.

Cosmology with the Cosmic Microwave Background
If the universe was perfectly homogeneous on all scales at the time of reionization (z = 1000), then the CMB should be perfectly isotropic over the sky. Instead, it shows small-scale fluctuations:

Measuring the “Deceleration” of the Universe …
By observing type Ia supernovae, astronomers can measure the Hubble relation at large distances Distance  recession speed Size scale of the universe  rate of expansion It was expected that this would measure the deceleration of the universe, but …

The Accelerating Universe
Flat decelerating universe Apparent Magnitude of Type Ia Supernovae Flat accelerating universe Red Shift z In fact, SN Ia measurements showed that the universe is accelerating!

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.

Soft X-ray Sky

Gamma-ray all-sky map Fermi Gamma-ray Space Telescope

The Evolution and Ultimate Fate of the Universe
Today, acceleration due to dark energy dominates. Until ~ 6 billion years ago, gravity of matter was stronger than acceleration

Scientific Notation Video