Big BangBig Bang

Extraterrestrial Life and Death Extraterrestrial Life and Death

Lecture Seven, Jan. 29, 2003Lecture Seven, Jan. 29, 2003

Pre-project EssayPre-project Essay

• In one or two typewritten pages In one or two typewritten pages discuss some of the events important discuss some of the events important for life on Earth between the Big for life on Earth between the Big Bang and the evolution of man. Bang and the evolution of man.

• Due Friday Jan. 31, 2002.Due Friday Jan. 31, 2002.

EvolutionEvolution

• Evolution and survival of fittest is very Evolution and survival of fittest is very powerful.powerful.

• Evolution needs stable environment for long Evolution needs stable environment for long time and way to store information (DNA).time and way to store information (DNA).

• Is evolution enough to explain Man and Is evolution enough to explain Man and intelligence from primitive life?intelligence from primitive life?

• A number of mass extinctions have occurred on A number of mass extinctions have occurred on Earth. Some probably from asteroid/ comet Earth. Some probably from asteroid/ comet impacts.impacts.

• Mass extinctions can be important for Mass extinctions can be important for evolution. evolution.

GenesisGenesis

• This completes overview of first third of class.This completes overview of first third of class.• Origin of Universe in Big Bang.Origin of Universe in Big Bang.• Origin of first stars and Milky Way galaxy.Origin of first stars and Milky Way galaxy.• Origin of chemical elements in stars that died Origin of chemical elements in stars that died

before the solar system formed.before the solar system formed.• Origin of solar system: Earth, Sun and planets.Origin of solar system: Earth, Sun and planets.• Origin of primitive life.Origin of primitive life.• Evolution of intelligence and Man.Evolution of intelligence and Man.• Man very recent, sophisticated multicell Man very recent, sophisticated multicell

organsims 6-700 Mya, life 3.8 Bya, formation of organsims 6-700 Mya, life 3.8 Bya, formation of Earth 4.6 Bya, formation of elements 5-12Bya, Earth 4.6 Bya, formation of elements 5-12Bya, Milky Way galaxy 12 Bya, Big Bang ~13 Bya.Milky Way galaxy 12 Bya, Big Bang ~13 Bya.

• Here is a reverse Here is a reverse timelinetimeline of some of these of some of these events in terms of the evolution of the Earth.events in terms of the evolution of the Earth.

Big BangBig Bang

• Grand explosion that created the Grand explosion that created the Universe.Universe.

• Who banged? God. Who banged? God.

• What banged? The Universe.What banged? The Universe.

• When was the big bang? ~13 B.y. ago.When was the big bang? ~13 B.y. ago.

• Where was the big bang? Everywhere. Where was the big bang? Everywhere. It created space.It created space.

• Why the big bang? For life???Why the big bang? For life???

Who bangedWho banged? God ? God

• As a physicist part of my definition of God As a physicist part of my definition of God is that which created the Universe. is that which created the Universe.

• Hey, it is in his job description.Hey, it is in his job description.• What banged. Tremendous explosion that What banged. Tremendous explosion that

created the mass, energy, space, and time created the mass, energy, space, and time of the Universe.of the Universe.

• When? We measure an When? We measure an expansion rateexpansion rate for for the Universe today. The faster the rate, the Universe today. The faster the rate, the faster the galaxies got to their present the faster the galaxies got to their present positions hence the younger the Universe positions hence the younger the Universe is. is.

Where was the Bang?Where was the Bang?

• Everywhere.Everywhere.• The explosion created the space and The explosion created the space and

time of the Universe. It also created time of the Universe. It also created the the reference framereference frame to ask where to ask where any event occurred.any event occurred.

• The Universe has no center and no The Universe has no center and no edge! Just like the surface of the edge! Just like the surface of the round Earth has no center or edge. round Earth has no center or edge.

What is outside the What is outside the Universe?Universe?• What is the Universe expanding into?What is the Universe expanding into?• What happened before the big bang?What happened before the big bang?• What is the sound of one hand What is the sound of one hand

clapping, Grasshopper?clapping, Grasshopper?• There was no time or space before There was no time or space before

the big bang.the big bang.• You will not be responsible, in this You will not be responsible, in this

class, for anything which occurred class, for anything which occurred before the big bang.before the big bang.

We now know that distant We now know that distant galaxies are moving away from galaxies are moving away from us as the Universe expands.us as the Universe expands.

Expanding Expanding UniverseUniverse

• Dots represent galaxies. Each dot moves away from Dots represent galaxies. Each dot moves away from all others as the Universe expands. Note, Universe all others as the Universe expands. Note, Universe shown as expanding surface, should show it as shown as expanding surface, should show it as expanding 3 dim space in 4 dimensions. expanding 3 dim space in 4 dimensions.

• Scientific visualization from "Galactic Odyssey“ Scientific visualization from "Galactic Odyssey“ produced by NCSA for NHK, the Japanese Broadcasting produced by NCSA for NHK, the Japanese Broadcasting Co. Co.

Click here for 10 second animation of expanding universe

Dots are Dots are Galaxies –Galaxies –Island Island UniversesUniverses

Single dot is M31 Single dot is M31 GalaxyGalaxyHubble deep field showing lots of Hubble deep field showing lots of

galaxiesgalaxies

Image of M31 from my driveway with an 8” telescope and a Image of M31 from my driveway with an 8” telescope and a homemade CCD camera.homemade CCD camera.

Great Scale of the UniverseGreat Scale of the Universe

• E. Hubble in 1920s used great 100” Hooker E. Hubble in 1920s used great 100” Hooker telescope to resolve M31 into stars. He enlarged telescope to resolve M31 into stars. He enlarged the image until the uniform white “milky way” the image until the uniform white “milky way” gave may to individual stars.gave may to individual stars.

• M31 is made out of lots of stars just like our own M31 is made out of lots of stars just like our own Milky Way! We are but one of very many Milky Way! We are but one of very many galaxies!galaxies!

• Stars were very dim. This implied M31 is very far Stars were very dim. This implied M31 is very far away. Of order 3 million light years! [Note, today away. Of order 3 million light years! [Note, today we think of this distance as a very close neigbor.] we think of this distance as a very close neigbor.]

• Read discussion and debate in the Perfect Read discussion and debate in the Perfect Machine.Machine.

Expansion of Universe and the Expansion of Universe and the Motion of Distant GalaxiesMotion of Distant Galaxies

• How do we know that distant How do we know that distant galaxies are moving away from us?galaxies are moving away from us?

• These galaxies are so far away that it These galaxies are so far away that it would take a very long time, even would take a very long time, even given their very high velocities, to given their very high velocities, to see them move appreciably.see them move appreciably.

• Instead, we infer their velocities from Instead, we infer their velocities from the the Doppler shiftsDoppler shifts of their of their spectral spectral lineslines..

Spectral LinesSpectral Lines

• How do we know the composition of distant Stars How do we know the composition of distant Stars and Galaxies?and Galaxies?

• Each chemical element has a set of unique Each chemical element has a set of unique spectral lines. These are particular frequencies of spectral lines. These are particular frequencies of light (electromagnetic radiation) that the element light (electromagnetic radiation) that the element absorbs or emits.absorbs or emits.

• Chemical elements are characterized by their Chemical elements are characterized by their atomic number Zatomic number Z. This is the number of electrons . This is the number of electrons that orbit the nucleus. Hydrogen Z=1, Helium that orbit the nucleus. Hydrogen Z=1, Helium Z=2, Lithium Z=3 … Uranium Z=92.Z=2, Lithium Z=3 … Uranium Z=92.

• Quantum mechanics says these electrons can Quantum mechanics says these electrons can only have discrete energies when they are only have discrete energies when they are orbiting the nucleus. A spectral line is emitted orbiting the nucleus. A spectral line is emitted when an electron jumps from one energy to when an electron jumps from one energy to another.another.

Hydrogen has Z=1, Carbon has Z=6 and Sodium (Na) has Z=11 Hydrogen has Z=1, Carbon has Z=6 and Sodium (Na) has Z=11 electrons.electrons.

Example, Sodium Glows Example, Sodium Glows YellowYellow

• Spectrum of Sodium shows green, bright yellow, Spectrum of Sodium shows green, bright yellow, orange. and red spectral lines. Light from a glowing orange. and red spectral lines. Light from a glowing discharge containing the element sodium is split by discharge containing the element sodium is split by a prism with short wavelengths (blue) on the left and a prism with short wavelengths (blue) on the left and long (red) wavelengths on the right. long (red) wavelengths on the right.

• Seeing these lines in the spectrum of a star or Seeing these lines in the spectrum of a star or galaxy implies that the distant object contains galaxy implies that the distant object contains sodium.sodium.

• Remember electromagnetic spectrum.Remember electromagnetic spectrum.

Composition of Other StarsComposition of Other Stars

• Spectral lines show that other stars, in Spectral lines show that other stars, in general, have a similar chemical general, have a similar chemical composition to our Sun.composition to our Sun.

• Therefore, the Sun is just another star!Therefore, the Sun is just another star!• The Earth was no longer the center of The Earth was no longer the center of

the universe since it orbits the Sun. the universe since it orbits the Sun. • Now the Sun is not the center of the Now the Sun is not the center of the

universe because it is just one of universe because it is just one of billions of stars in the galaxy.billions of stars in the galaxy.

• Spectra of some stars. Spectra are shown in order of Spectra of some stars. Spectra are shown in order of decreasing temperature for normal stars, whose names decreasing temperature for normal stars, whose names are listed on the right. Spectral types are labeled on the are listed on the right. Spectral types are labeled on the left, and the wavelengths and associated elements are left, and the wavelengths and associated elements are shown at the top and bottom for selected spectral lines.shown at the top and bottom for selected spectral lines.

Doppler shift of Spectral Doppler shift of Spectral LinesLines• If an object is moving away from you, the If an object is moving away from you, the

sound or light that it emits is Doppler sound or light that it emits is Doppler shifted to lower frequencies. shifted to lower frequencies.

• The lowest frequency visible light is red. The lowest frequency visible light is red. Therefore we call this a red shift.Therefore we call this a red shift.

• If the object is moving towards us, the If the object is moving towards us, the light is shifted to higher frequencies and light is shifted to higher frequencies and we call it a blue shift.we call it a blue shift.

• Can use the Can use the Doppler shift Doppler shift to measure the to measure the velocity of distant galaxies.velocity of distant galaxies.

Doppler Shift of Light from Doppler Shift of Light from GalaxyGalaxy

• The top figure compares spectral line (black line) The top figure compares spectral line (black line) from distant galaxy to same spectral line on Earth, from distant galaxy to same spectral line on Earth, yellow marks at top and bottom.yellow marks at top and bottom.

• If galaxy is moving away (middle figure) spectral line If galaxy is moving away (middle figure) spectral line is shifted to the red. If galaxy is moving towards us is shifted to the red. If galaxy is moving towards us (bottom), spectral line is shifted towards blue.(bottom), spectral line is shifted towards blue.

Hubble’s LawHubble’s Law

• E. Hubble found that light from distant E. Hubble found that light from distant galaxies was red shifted by an amount galaxies was red shifted by an amount proportional to distance (from us).proportional to distance (from us).

• The velocity of a distant galaxy v (inferred The velocity of a distant galaxy v (inferred from the red shift) is related to its distance d,from the red shift) is related to its distance d,

v=H dv=H d• Hubble’s constant H has dimensions of Hubble’s constant H has dimensions of

1/time.1/time.• Age of universeAge of universe is about 1/H. Exact value is about 1/H. Exact value

depends on how expansion rate depends on depends on how expansion rate depends on time. time.

• This expansion age is about 13 B. years.This expansion age is about 13 B. years.

Expanding Expanding UniverseUniverse

• Dots represent galaxies. Each dot moves away from Dots represent galaxies. Each dot moves away from all others as the Universe expands. Note, Universe all others as the Universe expands. Note, Universe shown as expanding surface, should show it as shown as expanding surface, should show it as expanding 3 dim space in 4 dimensions. expanding 3 dim space in 4 dimensions.

• Scientific visualization from "Galactic Odyssey“ Scientific visualization from "Galactic Odyssey“ produced by NCSA for NHK, the Japanese Broadcasting produced by NCSA for NHK, the Japanese Broadcasting Co. Co.

Click here for 10 second animation of expanding universe

Age of UniverseAge of Universe

• Age of oldest stars.Age of oldest stars. Stars turn into red giants Stars turn into red giants (such as Betelgeuse) when they burn their (such as Betelgeuse) when they burn their hydrogen fuel. More massive stars are hotter hydrogen fuel. More massive stars are hotter and burn their fuel much faster. and burn their fuel much faster.

• Our Sun will take a total of 10 billion years to Our Sun will take a total of 10 billion years to use up its hydrogen. Note, Sun has been use up its hydrogen. Note, Sun has been shinning for 4.6 B. years so it has about 5 B. shinning for 4.6 B. years so it has about 5 B. more years to go before becoming a red more years to go before becoming a red giant.giant.

• More massive stars, last much less then 10 B. More massive stars, last much less then 10 B. years. Less massive stars last longer. years. Less massive stars last longer.

Globular Star ClustersGlobular Star Clusters

• Contain up to a million Contain up to a million stars which all formed stars which all formed at nearly the same at nearly the same time. Look for time. Look for smallest mass star smallest mass star that has already that has already become a red giant. become a red giant. Many clusters in our Many clusters in our galaxy have red giants galaxy have red giants with masses slightly with masses slightly less then the Sun. less then the Sun.

• Thus the clusters are Thus the clusters are about 12-13 B. years about 12-13 B. years old. Universe is about old. Universe is about 1 B. years older1 B. years older Ancient Globular Star Cluster M13Ancient Globular Star Cluster M13

Radioactive dating of StarsRadioactive dating of Stars

• New! With a great deal of effort one can New! With a great deal of effort one can determine amounts of radioactive Thorium determine amounts of radioactive Thorium and Uranium in ancient stars in halo of Milky and Uranium in ancient stars in halo of Milky Way galaxy. This is done by observing Way galaxy. This is done by observing spectral lines (particular frequencies of spectral lines (particular frequencies of light) from U and Th in the star light.light) from U and Th in the star light.

• This gives a direct radioactive age of these This gives a direct radioactive age of these stars of 12 +/- 3 B. years.stars of 12 +/- 3 B. years.

• Three independent ways to date Universe: Three independent ways to date Universe: expansion rate, globular cluster red giants, expansion rate, globular cluster red giants, and radioactive dating. All say Universe is and radioactive dating. All say Universe is about 13 B. years old.about 13 B. years old.

Big Bang SummaryBig Bang Summary

• Universe contains countless galaxies like Milky Way.Universe contains countless galaxies like Milky Way.• A single galaxy can have 100s of billions of stars.A single galaxy can have 100s of billions of stars.• Spectrum (characteristic frequencies) of star light Spectrum (characteristic frequencies) of star light

similar to Sun. Sun is just nearest star.similar to Sun. Sun is just nearest star.• Each chemical element has characteristic spectral Each chemical element has characteristic spectral

lines.lines.• Doppler shift of spectral lines from distant galaxies Doppler shift of spectral lines from distant galaxies

shows universe is expanding.shows universe is expanding.• Measured expansion rate implies about 13 billion years Measured expansion rate implies about 13 billion years

ago all galaxies on top of each other: age of universe.ago all galaxies on top of each other: age of universe.• This was Big Bang that created a very hot and dense This was Big Bang that created a very hot and dense

universe that has been expanding and cooling ever universe that has been expanding and cooling ever since.since.

For next timeFor next time

• Read chap. 3 of Jakosky about the history of Read chap. 3 of Jakosky about the history of the Earth and read “Alchemy of the the Earth and read “Alchemy of the Heavens", pages 25-58 in course packet Heavens", pages 25-58 in course packet about origin of chemical elements.about origin of chemical elements.

• Pre-project Essay:Pre-project Essay: In one or two typewritten In one or two typewritten pages discuss some of the events important pages discuss some of the events important for life on earth between the Big Bang and for life on earth between the Big Bang and the evolution of man. Due Friday Jan. 31, the evolution of man. Due Friday Jan. 31, 2002. 2002.

• Next lecture, “Death Stars and Alchemy of Next lecture, “Death Stars and Alchemy of the Heavens” about the origin of the the Heavens” about the origin of the chemical elements.chemical elements.