Group Lec 002 May 15, 2:45-4:45pm Van Vleck B102Group Lec 001 May 16, 12:25-2:25pm Camberlin 2103

EXAMS:

A Timeline of the Universe

The Origin of Helium

• Immediately after the Big Bang, only protons and electrons existed

• Shortly after the BB, temperature and density was high enough for deuterium to form by fusion

• After 100 seconds or so, temperature cooled enough so that deuterium could fuse into helium nuclei

• The temperature continued to cool, and fusion stopped after a few minutes.

• Big Bang theory predicts that around 24% of the matter in the early universe was helium, which matches what we see.

The Epoch of Inflation

• Modern technology allows us to test theories back to a time 10-33 seconds after the Universe Birth (UB).

• Physics as we know it ceases to function at 10-43 seconds after the UB, called the Plank Time

• Using particle colliders, scientists have uncovered a number of clues about what happened in the early universe, after the Plank time

• The early universe underwent a period of very rapid expansion

• By 10-33 seconds, the universe expanded from the size of a proton to the size of a basketball

• This expansion is called inflation

Expansion Forever? Or Collapse?

• The fate of the universe is ultimately controlled by its total amount of energy– Energy of expansion (positive)

– Gravitational energy that can slow the expansion (negative)

– Binding energy

• If the total energy is positive or zero, the expansion continues forever

• If the total energy is negative, the expansion will halt, and the universe will contract and eventually collapse.

Dark Energy

• Dark energy may provide the solution to the mystery

• Dark energy remains constant everywhere, regardless of the universe’s expansion

• Provides an outward push to accelerate expansion

• Dark energy must make up around 70% of all of the energy in the universe

• Much work remains to be done on this frontier…

Life on Earth

• Life formed on Earth relatively soon after the planet’s formation– For ¾ of the Earth’s history,

only algae and single-celled life forms existed

– Slowly, more complex lifeforms developed

• By 250 million years before the present, dinosaurs and early mammals had evolved.

• Hominids, our distant ancestors, developed 5.5 million years ago

• Homo Sapiens evolved only 500,000 years ago!

Figure 83.04

• Life tends to draw on the substances that are most plentiful: Carbon, Nitrogen, Oxygen and Hydrogen

• Amino acids are organic molecules containing these substances

• Amino acids form proteins, which provide structure and energy to cells

• All life contains DNA – this instruction packet contains all the information needed to build an organism

The Origin of Life

• So how did amino acids form out of the substances available on the early Earth?

• Probably started thanks to complex chemical reactions in the atmosphere and surfaces of Earth

• The Miller-Urey experiment attempted to duplicate the environment of the early Earth

• A variety of complex organic molecules formed in their “atmosphere”

Fossil Eukaryote Algae

The Search for Life on Mars

• It appears that Mars at some point in its history was very much wetter and warmer than it is today

• Scientists have been looking for life there

• The Viking landers (1970’s) tested for the presence of microbes, but returned inconclusive results

• We are still looking!

Fossils of Ancient Martian Life?

SETI

• SETI: Search for Extra-Terrestrial Intelligence

• Listens for electromagnetic evidence of intelligence elsewhere in the universe

• To date, evidence has been sparse.