Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Big Bang, Black Holes, No Math

ASTR/PHYS 109Dr. David TobackLectures 24 & 25

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

Was Due Today – L25• Reading:

– (BBBHNM Unit 3)• Pre-Lecture Reading Questions Quiz:

– (Unit 3 Quiz)• End-of-Chapter Quizzes:

– Chapter 9: Was due before class– Chapter 10: Due before next class

• Feynman Diagram Drawing Assignment– Working on grades– (Feynman Diagram Assignment 1 &2 )– Feynman Diagram Assignment 3: Will assign today

• Papers– Paper 1:

• Grades posted. Let me know if you don’t see a grade or if you think you were misgraded– Re-grades in progress

• You can submit a revision after you have completed the full assignment. Need to re-do full assignment

– Paper 2• Text was due already in Peerceptiv and TurnItIn• Please finish the assignment soon if you haven’t already, can submit Revisions at any time

• Honors Section:– “Stage 2”: Was due before class on Monday– Need to hear from you at least once every 7 days

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Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Overview

• Finished: The Exploding Universe

• This Time: Expansion of Space-Time and General Relativity

• After That: Photons and Hydrogen in the Universe

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Outline

•General Relativity and Expanding Space-Time•Expanding Space and Red-Shifts

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

Recapping the DataGalaxies are moving away from us, faster if they are further away AND we see this to be true in ALL DIRECTIONS

Simple-but-wrong explanation: We are the center of an explosion!

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Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Is this right?Only consistent with this data if we’re at the center of the Universe and not

movingNot consistent with

other dataNeed a better explanation!

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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General Relativity to the Rescue

•Space-time can change–E.g. Mass causes it to curve and stretch

•What if space-time is expanding?

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Expanding SpaceAnalogy:

A loaf of raisin bread where the dough is rising and expanding, taking the raisins with it

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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A Better Example of Expanding Space

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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The Expanding UniverseSpace is expanding, carrying the

galaxies along with it!Galaxies ALSO move THROUGH space

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Velocity?

How does this explain why things are moving FASTER the further

away they are?

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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More on Expanding Space-Time and Raisin Bread

Distance

http://bigbang.physics.tamu.edu/Figures/StolenAnimations/RaisinBread.swf

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Expanding Space-Time and Red-

Shifts of Photons

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Photons in Expanding Space-Time

• Since space is so empty, light from 10 billion years ago can reach us just fine

• What happens to photons as they travel in the Universe?

• The wavelength gets stretched as space expands The wavelength gets longer

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Red Shifts in an Expanding Universe

http://bigbang.physics.tamu.edu/Figures/StolenAnimations/originredshifts1.swf

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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What do photons look like in Expanding Space-Time?

A distant galaxyemits a short wavelength photon towards our galaxy billions of years ago

The Grid shows space

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Space-Time Expands

The expansionof space-time stretches the photon to longer wavelengths as it travels

The Grid is bigger now

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Space-Time Expands More

The farther the photon has traveled, the more it is stretched

Still bigger

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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How We Observe It

When the photon arrives at our galaxy we see it with a larger wavelength The bigger the distance the more red-shifted it has become! Even bigger as time goes by

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

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Doppler Effect in Expanding Space

Evidence for the Big BangTopic 2: Expanding Space-Time

Big Bang, Black Holes, No Math

Prep for Next Time – L25• Reading:

– (BBBHNM Unit 3)• Pre-Lecture Reading Questions Quiz:

– (Unit 3 Quiz)• End-of-Chapter Quizzes:

– (Chapter 9)– Chapter 10: Due before next class– If we finished Chapter 11 then end-of-chapter quiz 11 due class after that

• Feynman Diagram Drawing Assignment– Working on grades– (Feynman Diagram Assignment 1 & 2)– Feynman Diagram Assignment 3: Due before next class

• Papers– Paper 1:

• Grades posted. Let me know if you don’t see a grade or if you think you were misgraded– Re-grades in progress

• You can submit a revision after you have completed the full assignment. Need to re-do full assignment

– Paper 2• Text was due already in Peerceptiv and TurnItIn• Please finish the assignment soon if you haven’t already, can submit Revisions at any time

• Honors Section:– “Stage 2”: Was due before class on Monday– Need to hear from you at least once every 7 days

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