The Universe - 2The Universe - 2

Inflation

• When the strong force began separating from the electroweak force at the end of the GUT era, theorists hypothize that a major release of energy caused the Universe to expand at an exponential rate (at every step in time, the size of the Universe doubled). This is the Inflation. • For instance, a region the size of a proton at 10-35 sec would have grown to the size of a basketball by 10-33 sec.• Although nothing can travel faster than light in space, space itself can expand faster than light; this is what happened during Inflation.• The tremendous expansion `flattened’ the Universe and created, possibly, parallel Universes.

Why do we need Inflation?

The light from the CMB has the same temperature everywhere and in every direction.However, the causally connected space had the size of a small dot: .

Thus, the CMB should appear with small temperature variations, but it does not: Inflation!

The Geometry of the Universe• The Big Bang and early evolution of the Universe does not tell us anything about its geometry • This is determined by how much mass there is in the Universe• For all practical purposes, the mass in the Universe bends the space-time, pretty much like a Black Hole bends the space around itself.• The geometry of the Universe determines its fate:

• a closed Universe will at some point reverse its expansion into a contraction, and proceed towards a Big Crunch• a flat or open Universe will expand forever.

Whether the universe is open, close, or flat depends on how much

matter (and energy) it containsFor a flat Universe, the mean density (matter in

a unit of volume) of the Universe at the present time must be about 10-26 kg/m3

It is determined by fundamental quantities, like the Hubble constant and the Gravitational constant:

c = 3 H2 / (8 G)

Three possibilities:Flat Universe, real and apparent sizes are the same - (critical case, stops at infinite times)

Closed Universe, objects appear larger than they are

(expands and re-collapses)

Open Universe, objects appear smaller than they are

(expands forever)

The geometry of the Universe

The Universe as viewed in the Microwave by the WMAP satellite

Contrast x 30,000

The angular sizes of the structure tells us about the geometry of the Universe, because the real sizes are known.

1 degree = Universe Horizon

The most prominent structures are about 1 degree, meaning the

Universe is flat

Why is the Universe flat: because of Inflation

Formation of structures

• By `structures’ we mean: stellar clusters, galaxies and clusters of galaxies;

• They were formed out of the fluctuations formed gravitationally by Dark Matter while the baryonic matter was still interacting with the light before the last recombination surface (z=1100)

The Universe as viewed in the Microwave by the WMAP satellite

Contrast x 30,000

This small anisotropy (~ 1/106) in the CMB, emitted 300,000 years after the Big Bang, represents the small fluctuation in the matter distribution which provides the seed for the structure formation in the universe.

Structure Formation in the Universe

Cosmological Simulations

Observational Cosmology

Formation of the Large-Scale Structure

Due to gravity,

acting on Dark Matter

Big Questions• What will be the fate of the universe?

• What are the dark matter and dark energy?

• What causes the big bang (inflation)?

• What, if any, of this should we believe?

A summary of this course

How do we combine geology and astronomy?

1. Astrobiology is one of the most recent fields of Astronomy, and is still under development; it combines the strengths of astronomy, biology, geology, climate science to investigate the possibility of life outside Earth;

2. The investigation of Solar System objects requires geologists to be involved in the quest; for instance, Prof. Hanner’s presentation talked about analyzing samples of comets. Geologists are the experts who know how best to perform such analyses. Not to forget: Lunar and Mars explorations!

What telescopes does NASA use to get the colorful pictures of nearby and distant

galaxies?

Chandra:X-ray

Hubble:UV and Optical

Spitzer:Infrared

What is the evidence for the existence of anti-matter?

• Antimatter has been created in particle accelerators around the world; its existence is well established.

• What we do not not is the origin of the slight primordial imbalance that produced the current `matter’ Universe.

What is the farthest thing/object we have identified from Earth?

It really depends on what you mean by `object’. The farthest we think we will ever be able to `see’ is the Cosmic Microwave Background. The farthest galaxy, so far, is at redshift z=7, equivalent to an age of the Universe of less than 1 Gyr.

The M.A.G.I.C. Gamma-ray Telescope team just released the discovery that high-energy gamma-rays from Mrk501 arrived with 4 minutes delay relative to

lower-energy radiation. What does it mean?

The authors suggest that this is an effect of quantum gravity (the high energy photons travel more slowly through the `quantum foam’).

However, energy scales are much below the `Planck energy scale’, which is needed to test effects that happen at the level of individual protons.And uncertainties in our knowledge of gamma-ray-burst sources compounds to raise some questions about the result.

What is in the center of the Milky Way?

A black holes, plus a large number of stellar clusters.

Is the presence of a white dwarf in a binary system shorten the life of the

companion star?

No. Because the mass loss from the companion star would happen anyway; the difference is that instead of being lost in space, it is accreted onto the white dwarf.

What is the chemical that makes the Neptune’s atmosphere appear blue?

Largely due to the methane in the atmosphere, which absorbs the red light(but there could be some yet unknown component in addition)

If a comet collided into Jupiter’s Red Spot, would it

stop the storm?It would really depend on the size (mass) and speed of the comet, I.e., on the total energy that an impact would impart to Jupiter.