EPS 1063 Lecture #153

Week 2 The origin of the Universe, the solar system and our planet Earth.

August 2858 ^thNov. 14, 2000, 1999

General introduction. A good place to start is the beginning. Doesn’t necessarily have anything to do with environment, but something that everyone should be exposed to.

STARTING AT THE BEGINNING!

· The Universe started with the Big Bang 15-20 billion years ago.

It started from a single point. Before that there was neither space, nor time, nor mass. (Einstein’s theory of time-space continuum – discuss Einstein’s theory from

a) atomic clocks and b) the shift in the planetary position.

(The overall framework of the big bang theory came out of solutions to Einstein’s general relativity field equations and remains unchanged, but various details of the theory are still being modified today. Einstein himself initially believed that the universe was static. When his equations seemed to imply that the universe was expanding or contracting, Einstein added a constant term to cancel out the expansion or contraction of the universe. When the expansion of the universe was later discovered, Einstein stated that introducing this “cosmological constant” had been a mistake.)

· After 10^-35 sec, it was the size of a pea and 10 billion billion billion (10²⁸) degrees.

· Only after several minutes was temperature low enough for the nuclei of hydrogen and helium to form.

· 100,000 years later, electrons formed, so that true molecules could exist. Photons formed at the same time, allowing for light to exist.

· During the outward expanse of exploding gas, clouds of hydrogen and helium were formed. These clouds began to coalesce under their own gravity to form galaxies, and then individual protostars.

· The temperature of these clouds rose during condensation (due to potential energy release) and nuclear reactions occurred, making them ‘energy-producing’ stars. The nuclear reactions led to the formation of the elements (the otherrest of the elements ( 2%), during formed by repeated episodes of coalescing stars and supernovae (the following explosions).

· How do we know about the Big bang? “Red Shift” and 2.7°C background radiation that permeates the Universe and is a background glow from the Big Bang.

· Discuss Red Shift (Edwin Hubble). The red shift gives an age of 15 billion years (with an uncertainty of a factor of two).

· George Gamow first formulated his theory of the Big Bang, and predicted there would be a leftover radiation "signature" from the Big Bang, and he realized it might be detectable. He calculated the original temperature of the explosion, took into account the temperature reduction that would be caused by the universe's subsequent expansion (review the physics) and arrived at a figure of about 5 Kelvins.

· In the 1960s Arno Penzias and Robert Wilson were working at AT&T Bell Laboratories, trying to improve microwave communications by reducing antenna noise. They found a noise in their antenna they simply couldn't remove. They considered all kinds of possibilities including bird droppings, but nothing helped. If the antenna was pointed at the sky, the noise appeared. The pointing direction and time of day didn't matter. Finally they called an astrophysicist at Princeton, who told them what the signal probably was, hung up the phone, turned to his associates and said, "We've been scooped." The annoying noise was, in fact, the primordial radiation left over from the Big Bang. Penzias & Wilson won the Nobel Prize for their discovery. (See figure).

· Galaxies form from condensation of tabular masses. Stars form from gravitational pull of matter. Temperatures rise, nuclear fusion begins, and stars become energy producing. (Discuss potential energy). There are 100 billion billion stars.

· Our Galaxy is the Milky Way. Formed 15 billion years ago. Spiral galaxy. 100 billion stars (10% is interstellar matter). We are in the outer rim. Our star formed >4.6 billion years ago. (That we are not in the center of the Universe was realized by Copernicus and Galilleo).

·

· Everything you see is the Milky Way except the Magellenic clouds (discovered 1519 by Magellen. Why? 170,000 light years away, 30,000 light years across). OVERHEAD

· Our Solar system.

· Formed from a solar nebula – a swirling cloud of gas and dust.

· Originally cool, it is 99% H and He

· The nebula coalesced forming the sun. (One textbook says RenD¹⁸

· Smaller clouds formed protoplanets

· All spin the same way (except Venus, Uranus and Pluto) OVERHEAD

*Discuss problem of spin – outgassing of solar wind and interaction with magnetic field. A brake, so to speak.

· The planets. (Table 6.1 in Our Changing Planet). First planetesimals

· Formed from condensation of gases. *Discuss satellites

· Four inner ‘terrestrial’ planets (Mercury, Venus, Earth, Mars).

· The asteroid belt.

· Four ‘Jovian’ planets (Jupiter, Saturn, Uranus, Neptune). H, He, ammonia, methane

· Pluto

Mercury	small, dense, hot, magnetic field	No atmosphere – too small
Venus	like Earth, 475°C,	Mostly CO2, some acid.
Earth		Mostly N2, O2
Mars	smaller than Earth (seasons)	very thin, mostly CO2. Tremendous winds. Water at one time, life?
Jupiter OVERHEADS	Enormous, over 300 times Earth; Gives off heat.	Metallic H core, liquid H outer part, some He, methane and ammonia.
Saturn	1/3 size of Jupiter.	Similar with incredible rings
Uranus	tilted orbit, rocky core?	H, He, CH4, strong mag. field
Neptune	Similar to Uranus	Liquid water-methane?
Pluto	Small, solid core	methane & ice?

Photo gallery:

1. Background cosmic radiation (N. Hemisphere) left over from the Big Bang. Quite patchy.

2. Interstellar hydrogen gas from the Eagle Nebula

3. Closeup of column

4. distant galaxy called M 100 taken in 1995 from the Hubble Telescope.

5. Star forming in a nebula

6. Crab Nebula (supernova seen exploding on Earth in 1054).

7. Milky Way (large band), Magellenic cloud (bright blue, lower right) with Supernova (bright white spot in Magellenic cloud. The (Large) (Magellenic cloud is 150,000 light years away.

8. Mercury (average temperature 200 C, up to 500oC) 1/3 diameter of Earth)

9. Venus (average surface T = 500oC) Only slightly smaller than Earth

10. Venus surface

11. Mars (half the radius, 1/10 the mass), tiny atmosphere, below freezing

12. Jupiter and moons (317 times more mass, 11 times the diameter, 2.5 times gravity, T~-100oC

13. Jupiter

14. Jupiter close up of spot

15. Even closer

16. Saturn w/ satellites (almost all hydrogen atmosphere; 1/10 the density, 97 K.

17. Saturn

18. Uranus (14 times the mass of Earth; density, 1/5^th; 100 times atmospheric pressure, 58 K at surface; hydrogen 82.5%, helium and a touch of methane)

19. Neptune showing blue cloud

20. Neptune's blue cloud

21. Pluto and its sister satellite Charon (only 0.0021 time the mass of Earth; radius 1/10^th; discovered, 1930; atmosphere, almost none, methane and nitrogen; ~50 K).

Meteorites and asteroids. Where from. Apollo objects, etc.

·Formation of Earth.

·Coalescence of silicate material. Cool. Then heating by:

1) meteorite impact

2) gravitational compression (potential energy)

3) decay of radioactive elements (not a lot of material, but packs a whollop).

Caused melting or iron-nickel and formation of core. The ‘falling’ of this iron core would cause a heating increase of over 2000°C. Planetary differentiation is the most significant event in the history of the Earth. Caused ‘resetting’ of the planet.

The Earth has a solid inner metallic core, an outer liquid metallic core, an inner and outer silicate-rich mantle and the crust (finally with ocean film). OVERHEAD? How do we know that there is a liquid outer core. Seismicity . P – waves (primary waves) are compressional (push-pull). S-waves (secondary waves) are shear waves. Demonstrate.