COSMOLOGY HOW IT BEGAN

1 / 40

# COSMOLOGY HOW IT BEGAN - PowerPoint PPT Presentation

COSMOLOGY HOW IT BEGAN. Chris Impey University of Arizona. Norton, 2010. Space. Science is Seeing. A Scale Model. Set the Earth to the size of a walnut, or a 1:500,000,000 scale model. =. The Moon is a pea at arm ’ s length The Sun is a 3 m ball 300 m away

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about ' COSMOLOGY HOW IT BEGAN' - nibaw

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

COSMOLOGY

HOW IT BEGAN

Chris Impey

University of Arizona

Space

Science is Seeing

A Scale Model

Set the Earth to the size of a walnut, or a 1:500,000,000 scale model

=

• The Moon is a pea at arm’s length
• The Sun is a 3 m ball 300 m away
• Neptune is a softball 9 km away
• Nearest star is 80,000 km away

And at this scale, light is reduced to very slow walking speed. There’s no way information in the universe can travel any faster

• The Moon is a seconds walk away
• The Sun is 8 minutes walk away
• 10 hours to walk the Solar System
• 4 years to walk to the nearest star

Reduce the scale by a factor of 10,000,000

• The Solar System is a grain of sand
• The distance between stars is 20 m
• The Milky Way is the size of the U.S.
• The MW has 400,000,000,000 stars

Now reduce by another factor of 10,000,000

• The Milky Way is like a small plate
• The nearest galaxy is 5 m away
• The universe is the size a large city
• Billions of galaxies within this space

Galaxies

Scattered in a universe 46 billion light years across

100 billion

galaxies

Stars

The Milky Way is typical with 400 billion stars

100,000 billion

billion stars

Atoms

Almost all the simple elements hydrogen and helium

1080

Atoms

Photons

A billion photons for every particle

1089

Mediocrity

• We therefore live on an:
• Average planet around
• An average star in an
• Average galaxy in a
• Very large universe

Copernicus

Universal Pie

Composition of the Universe

Dark matter: 22%

Dark energy: 73%

Cosmology

Slipher

Lookback Time

If the speed of light were infinite, light from everywhere in the universe would reach us at exactly the same time and we would see the entire universe as it is now.

But it is not, so we see distant regions as they were in the past.

Distant Light = Old Light

3C 273

Cosmology: What We Know
• Redshift – it’s a universal

expansion of space-time,

not a Doppler shift.

• The microwave background radiation (CMB), a signal that is close to perfectly thermal, at temp of 2.726K.

Hubble Ultra Deep FieldHST•ACS

• Galaxies in past look younger (smaller and more irregular).
Evidence
• A good scientific model should always make predictions which can be verified.
• The big bang model makes two predictions which have been verified since the 1960s:
• the existence and characteristics of the cosmic microwave background (CMB)
• the expected Helium abundance in the Universe
• The model predictions agree with all current observations. There is much indirect evidence the universe was smaller and hotter in the past
Cosmic Microwave Background
• The universe is immersed in a sea of radiation.
• 380,000 years after the big bang, the universe had cooled enough for free electrons to become bound into atoms of Hydrogen and Helium
• Without electrons to scatter them, photons were able to travel unhindered throughout the universe
• The universe became transparent
• The temperature of the universe was 3,000 K at this time, similar to a stellar photosphere
• It has expanded by a factor of 1000 since then, reducing the temperature to 3000/1000 = 3 Kelvin

When we look at the CMB, we look at the surface of the glowing “fog” that filled the entire early universe!

Origin

Science is Seeing

The big bang was extraordinary― the instantaneous creation of all of space and time, containing energy to drive the expansion and enough matter for 100 billion galaxies.

The initial state was so compact that it can only be described by a theory that unites gravity and the quantum world. We do not have such a theory at present.

The big bang can be thought of as a quantum event, originating from very chaotic space-time in which the other quantum fluctuations might have led to other parallel universes.

Cosmic Inflation

The standard big bang has trouble explaining why the universe is as smooth and flat as it is, leading to the idea of an epoch of extremely rapid inflation, just 10-35 sec after the big bang. The mechanism is unclear but probably associated with the Grand Unified theories that seek to unite all the forces except gravity.

Status of Inflation

Inflation makes the universe flat and smooth (by design!), and it implies vast region of space that are beyond view. It has tentative support from CMB satellite data.

Beyond the Horizon

The universe is bounded in time and not space. General relativity sets no speed limit to the expansion. As time goes by, ever more distant regions come into view.

At z = 1.3, an object was moving away from us at c at the time the light was emitted.

At z = 1000, two distant points were moving apart at ~60c at the time the radiation was emitted.

Consequence of standard big bang: The physical universe is much

larger than the observable universe, we are subject to a horizon.

Consequence of the inflationary big bang: A microscopic region of

space-time became our universe; the universe is a quantum entity.

THE UNIVERSE AND US

Us

Earth

Solar System

Milky Way

Universe

Multiverse?

Beyond the Horizon

Science is Seeing

Life occurs in

a range of scales that extends from galaxies to the atomic nucleus, as symbolized by the ancient symbol of the ouroboros, the snake that eats its own tail

Quantum fluctuations are a mechanism for multiple realizations of the universe

…leading to the concept of the “multiverse”

String Theory Landscape

500

Perhaps 10 different vacua

de Sitter expansion in these vacua create quantum fluctuations and provide the

initial conditions for inflation. String theory provides context for the “multiverse”

The “ekpyrotic” universe has a big bang, but it is not ever at an infinite temperature and density, and it is not the origin of all space-time…

So our universe emerged from a collision of two 4D branes that are embedded in 5D space-time. The collision is the engine for expansion and matter creation.

Nature of the Expansion

The early expansion was rapid, driven by intense radiation. It slowed down as the dark matter began to dominate, and more recently has begun to accelerate due to the relative growth of dark energy.