# Expanding Universe

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Expanding Universe. Robert Nemiroff Michigan Tech U. Physics X: About This Course. Officially "Extraordinary Concepts in Physics" Being taught for credit at Michigan Tech Light on math, heavy on concepts Anyone anywhere is welcome No textbook required - PowerPoint PPT Presentation

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• Expanding Universe

Robert NemiroffMichigan Tech U.

• Physics X: About This CourseOfficially "Extraordinary Concepts in Physics"Being taught for credit at Michigan TechLight on math, heavy on concepts Anyone anywhere is welcome No textbook requiredWikipedia, web links, and lectures onlyFind all the lectures with Google at:"Starship Asterisk" then "Physics X" http://bb.nightskylive.net/asterisk/viewforum.php?f=39

• Considering Our Universe as a WholeThe Cosmological PrincipleUniverse Homogeneous & IsotropicHomogeneousSmooth when averaged outExample: jello, even fruity jelloIsotropicSame in every directionExample: room with the lights out

• The Expanding Universe: Hubbles LawOur Universe is expanding!Discovered by Edwin Hubble in 1930sMore distant galaxies are moving away fasterHubbles Law: v = Ho dv is galaxy velocity, d is galaxy distance and Ho is Hubbles constant

• Expanding Universe

What is our universe expanding into?

1. Empty space.2. An extra spatial dimension.3. An extra time dimension.4. General Relativity only says that objects can move apart.

• Expanding Universe

4. General Relativity only says that objects can move apart.

There are theories that use other spatial dimensions, but Einstein's General Relativity (GR), by itself, isn't one of them. GR only says that the entire universe could be expanding. GR does not include a larger "empty space" that it could be expanding into. In GR, matter and energy is everywhere. Observations indicate that matter is diluting everywhere.

• http://hyperphysics.phy-astr.gsu.edu/hbase/astro/hubble.html

• Center of the Universe

Toward which direction is the center of the universe?

1. The Sun.2. The center of our Milky Way Galaxy.3. The dipole hotspot on the microwave background.4. No direction.

• The Expanding Universe: Where is the center?In General Relativistic Cosmology:

There is no center.There is no Big Bang National Park.The Universe is not an exploding golf ball.Every point can be considered the center.The expansion looks the same from every point.

• http://www.hk-phy.org/articles/univexpand/univexpand.jpg

• (Courtesy of SLAC and Nicolle Rager)http://www.interactions.org/imagebank/search_detail.php?image_no=SL0062

• The Expanding Universe: What is expanding?Newtonian cosmology does have a centerWould result in strange unseen forcesYou and I do not expandAnything held together does not expandThe average space between galaxies expands almost drifts -- apart