Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Outer space wikipedia , lookup
Nucleosynthesis wikipedia , lookup
Gravitational lens wikipedia , lookup
Astronomical spectroscopy wikipedia , lookup
Shape of the universe wikipedia , lookup
Big Bang nucleosynthesis wikipedia , lookup
Expansion of the universe wikipedia , lookup
1 Understanding the PHYSICS of the Cosmic Times Inquiring into the Nature of the Universe Adapted from Dr. James Lochner USRA & NASA/GSFC Sandra Sweeney, Joseph Petsko Perkiomen Valley School District, PA 2 Cosmic times 1955 3 Einstein’s theories E = mc² , which explains how matter can come from energy, and vice versa (E=energy, m=mass, c=speed of light) Light is not only a wave, but also a particle Theory of Special Relativity, which includes nothing can go faster than the speed of light Gravity bends space-time 4 Telescopes 5 Radio telescopes The Very Large Array at Socorro, New Mexico, United States 6 Visible light telescopes: reflecting or refracting Refracting 7 The Refracting Telescope or Refractor REFRACTING TELESCOPES ARE THE MOST COMMON FORM OF THE TELESCOPE - A LONG, THIN TUBE W HERE LIGHT PASSES IN A STRAIGHT LINE FROM THE FRONT OBJECTIVE LENS DIRECTLY TO THE EYEPIECE AT THE OPPOSITE END OF THE TUBE. Advantages * Easy to use and consistent due to the simplicity of design. * Good for distant terrestrial viewing * Excellent for lunar, planetary and binary stargazing especially with larger apertures * Sealed tube protects optics and reduces image degrading air currents * Rugged, need little or no maintenance Disadvantages * Generally have small apertures, typically 3 to 5 inches * Less suited for viewing small and faint deep sky objects such as distant galaxies and nebulae * Heavier, longer and bulkier than equivalent aperture reflectors and catadioptrics * Limited practical usefulness * Good-quality refractors cost more per inch of aperture than any other kind of telescope 8 Reflecting telescope There are many types: Wikipedia 9 The Reflecting Telescope or Reflector Reflecting telescopes use a huge concave parabolic mirror instead of a lens to gather and focus the light to a flat secondary mirror that in turn reflects the image out of an opening at the side of the main tube. You look through an eyepiece on the side of the tube up near the top. Advantages * Easy to use and even construct * Excellent for faint deep sky objects such as remote galaxies, nebulae and star clusters because of their larger apertures for light gathering. * Low in optical irregularities and deliver very bright images * Reasonably compact and portable * A reflector costs the least per inch of aperture compared to refractors and catadioptrics since mirrors can be produced at less cost than lenses Disadvantages * Generally, not suited for terrestrial applications * Slight light loss due to secondary obstruction when compared with refractors * The tube is open to the air, which means dust on the optics even if the tube is kept under wraps * Reflectors may require a little more care and maintenance 10 11 The universe is twice as big as thought : Two Types of Cepheids! During the wartime blackouts in California, Walter Baade discovered two different populations of stars in Andromeda Used 200 inch telecscope This led to realizing there are two types of Cepheids, with two different period-luminosity relationships. Hubble had unknowingly used the wrong relationship. Yardstick vs Metersticks 12 13 [show clip of 1955 Cosmic Times showing “Origin of Everything” article ?] 14 Is Universe a “Steady State” or Did it originate from a “Big Bang?” Steady State Theory: As universe expands, matter is created. Evolution Theory (a.k.a. the Big Bang theory): running expansion backwards leads us to a point of high density and high temperature from which universe originated. (Create everything all at once) All will suck back together due to gravity and rebound, back and forth forever OR Everything will continue to expand outward 15 Steady State Universe Fred Hoyle, Hermann Bondi and Thomas Gold see the movie The Dead of Night, in which the end of the story circles back to its beginning. Unchanging situations need not be static New matter can be created spontaneously as the universe expands (a few hundred atoms per year per galaxy) Expansion of universe and creation of new matter balanced via a negative energy. The universe is constant in its overall density 16 Evolutionary Universe Starting from earlier work, George Gamow & Ralph Alpher worked out the conditions in the early universe Universe is expanding from a state of high density and pressure. Hydrogen & Helium were formed as universe cooled. There should be left over a background radiation with a temperature of ~ 5 Kelvin Hoyle scoffed at this theory and coined the term “Big Bang” 17 What is the Evidence for Big Bang? Leftover heat from explosion (3.5 degrees Kelvin) The Mark 1 radio antenna constructed to detect radio waves leftover from the Big Bang 18 A new type of star discovered: the supernova Giant exploding stars They create heavier, bigger elements Elements discovered by use of spectroscopy 19 Star life cycle: see textbook 20 1965 21 Show clip from 1965 CT, with “Murmur of a Bang” and “Big Hiss” 22 THE FIRST OBSERVED EVIDENCE OF THE BIG BANG Tool used: Penzias and Wilson were using a 20-foot horn detector to test satellite communication. Effort to reduce fuzz/hiss in the detector left them with a 3 degrees K residual. But they didn’t know its origin. 23 Tool for Determining “Steady State” vs. “Big Bang” Peebles and Dicke (Princeton) had just calculated an estimate for the temperature (3.5º K) of the residual background radiation from the big bang explosion, and found it was detectable in the microwave region. Called “cosmic background radiation” Peebles and Dicke were convinced that Penzias and Wilson had found it. This was strong evidence against the Steady State model of the universe and for the Big Bang theory. 24 Review of… 25 New Problem #1, assuming the Big Bang to be true: Will the universe eventually collapse back into itself, and explode again in an endless cycle (“oscillating universe”) OR Will the universe keep increasing in size forever with each galaxy isolated in emptiness? 26 Problem #2 has arisen with improved technological observations Galaxies do not appear to have enough mass in them compared to their luminosity (brightness). Most of the galaxy’s mass is not giving off light. How could 99% of the mass be MISSING!? 27 Problem #3 X-rays are being detected from the universe… But from where? 28 Discovery of QUASARS Galaxy-like objects that emit radiation that we can detect Power of 10 trillion suns Travel at 450 million miles/hr. (2/3 speed of light) They have been detected nearly 14 billion light-years away. What does this distance tell us about the age of the universe? 29 30 Cosmic Times 1919 - Confirmation of Einstein’s Theory of Gravity 1929 - Hubble’s discovery of Expanding Universe 1955 - Debate between Big Bang and Steady State 1965 - Discovery of the Cosmic Microwave Background 1993 - COBE Results; Development of Inflation Theory 2006 - Grappling with Dark Energy. 31 Cosmic Times: Scientific Themes Our understanding of the Expansion of the Universe Nature of Supernovae The size and scale of the Universe A number of other themes also appear. Impact of improved technology. Role of Women in early astronomy. 32