SCALES: COSMIC

GALAXY BASICS

Bright galaxies tend to have one of two shapes.

1) Spiral galaxies, like the Andromeda Galaxy and the Whirlpool Galaxy.

Stars in a spiral galaxy go around on neat (almost) circular orbits.

2) Elliptical galaxies, like the galaxy M87.

There is also an abundant category of dwarf galaxies, including our neighbors LMC & SMC.

Stars in an elliptical galaxy are on disordered, randomly oriented orbits.

SCALE MODEL III

A great island of stars in space, all held together by gravity and orbiting a common center

M31, Andromeda

Galaxy

The sum total of all matter and energy; that is, everything within and between all the galaxies. Most of the space between galaxies is empty.

Universe

Galaxy shrunk to size of small plate

That factor is 1023 or 100,000

billion billion

Geshe ActivityLet’s lay out the local universe, remembering that each galaxy contains a few billion stars.

Use the scale model where a large galaxy is a small plate and a dwarf is a cotton ball to lay out the architecture of the nearby universe.

Nearest Neighbors

Local Group

Virgo Cluster

Nearby Universe

This model shrinks the scale by 10 billion from the model of grains of sand as stars. Scale is a phenomenal 1:1023.• The Milky Way is a plate 10 cm

across• LMC/SMC cotton balls 20 cm away• Andromeda is a plate about 3 m away• Virgo Cluster is 1000 plates 70 m away• Observable universe is 100 km across

SPACE SCALE MODEL III:

Cosmological Principle

Isotropic: same at all locations

Homogeneous: same in all directions

Cosmology is based on the assumption that our location (MW) is typical and not unusual.

Geshe ActivityCosmology assumes we have no special place in the universe, i.e. homogeneity and isotropy.

With monks as galaxies, and one acting as the MW, arrange yourselves to be the same in all directions but not all locations, and vice versa.

Science is Seeing

The Universe is Empty

The visible universe contains 1023 stars in 40 billion light years. That is 1041 km3 of star stuff in a space of 1074 km3. So only one part in 1033 or a billion trillion trillion contains anything.

Scientific Visualization