Dark Energy


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Dark Energy

  1. 1. Dark Energy by Jennifer Nalley March 2007
  2. 2. *About 70% of the calculated mass in the Universe can not be accounted for. *It has become apparent that something other than the matter and energy we know is responsible for the greater portion of the Universal contents. *Something else is out there, and it appears as though it is doing much more than simply filling up space. On to some history........
  3. 3. The Static Universe and The “Cosmological Constant” <ul><li>In his “ General Theory of Relativity” , Albert Einstein initially included a “ cosmological constan t” in his equations to insure that mathematically, the universe would be static as it was believed to be. </li></ul><ul><li>He later regretted the addition, calling it his “biggest blunder”. </li></ul>MY BIGGEST BLUNDER!!!
  4. 4. The Expanding Universe <ul><li>Edwin Hubble finds evidence of an expanding Universe.. </li></ul><ul><li>When he noticed redshifts in the emission of light from distant galaxies, he realized that they were moving away from each other. This phenomenon is now known as Hubble's Law. </li></ul><ul><li>The universe was not static, but expanding. </li></ul><ul><li>The famous Hubble Telescope bares his name </li></ul>
  5. 5. <ul><li>At some point between the days of Einstein and Hubble, </li></ul><ul><li>and the present,....astronomers and theorists became all too </li></ul><ul><li>aware that there was energy missing in the universe, meaning </li></ul><ul><li>that they could only account for about 5% of the total matter </li></ul><ul><li>that was supposed to be there. This has been </li></ul><ul><li>confirmed by the 2DF and SDSS projects, which map </li></ul><ul><li>the position and motions of millions of galaxies. </li></ul><ul><li>They found some of this missing substance to be </li></ul><ul><li>“ DARK MATTER”, (not to be confused with Dark Energy) </li></ul><ul><li>Even with the dark matter included, the total </li></ul><ul><li>accounts for just 1/3 of the total that should be there. </li></ul><ul><li>We know that the collective energy density of all of the photons, </li></ul><ul><li>atoms,dark matter and everything else, should add up to a certain </li></ul><ul><li>critical value determined by the Hubble constant. </li></ul><ul><li>THEY DO NOT! </li></ul>
  6. 6. <ul><li>Looking for the rate of </li></ul><ul><li>the universe's expansion </li></ul><ul><li>over time , something </li></ul><ul><li>Unexpected was found </li></ul><ul><li>In type 1a Super Nova! </li></ul>
  7. 7. <ul><li>Given the great technological improvement of astronomical tools, In the last decade, astronomers began to investigate how the rate of the universe expansion was changing with time. </li></ul><ul><li>They assumed a deceleration would be detected, but wanted to know the details. </li></ul><ul><li>They found their answers with the observations of type 1a Supernovae. </li></ul><ul><li>Type 1a are ideal for the job, in that their brightness provides a dependable measure of their distance, and they are so bright that they are visible billions of light years away. </li></ul>
  8. 8. What They Found <ul><li>Was that the universe appears to be more than expanding.... </li></ul><ul><li>It is expanding at an increasing rate, accelerating. </li></ul><ul><li>There appears to be a connection to this accelerating expansion and dark energy. </li></ul>
  9. 10. DARK ENERGY Current Beliefs and Theories Dark energy is responsible for about 70% of the density of the universe. It is gravitationally repulsive, fighting against the gravity of the mass in the universe (that should be causing the universe expansion to slow).It is believed to be the reason the universe expansion is accelerating. It does not cluster in galaxies like other matter. It appears to be spread smoothly. It, like dark matter seems to be unaffected by radiation. It has a uniform density- about 10 E-26 Kilograms per cubic meter. It reduces the rate at which other galaxies interact, merge, bang, overall gravitationally interact.
  10. 11. EINSTEIN! RIGHT AGAIN? Einstein's cosmological constant may have not been such a blunder after all Quoting SNLS- Super Nova Legacy Survey “ What is now being observed shows that this dark energy behaves like the discarded constant....to a precision of 10% Ph ysicist Leonard Susskind discusses the dark matter mystery at the American Association for the Advancement of Science meeting in Washington, D.C. Dan Falk MY BIGGEST BLUNDER!!! WAIT ONE MINIUTE!
  11. 12. Resources Scientific American- February 2007 “ The Universe's Invisible Hand ” by Christopher J. Conselice (SNLS) Super Nova Legacy Survey Argelander Institut f Ü r Astronomie The Cosmological Constant Problem May 12, 2000 by Steven Weinberg Physics World Magazine May 2004 University of Copenhagen's Dark Cosmology Center at the Niels Bohr Institute. (Info from web page).
  12. 13. THE END