National Aeronautics and Space Administration Home Edition Age of the Universe: Cosmic Times Size of the Universe: 6 Billion Years 1955 4-8 Billion Light Years Death of a Genius:Albert Einstein he world has just lost its Examples of these include his revo- us do not speak physics. Instead, greatest scientific mind. Al ­ lutionary re-thinking of light as not we sense the importance of the Tbert Einstein died in his sleep just waves but particles, and his man indirectly. We watch like chil­ on April 18th from complications theory of special relativity, which dren at a parade, as his life and his of a gall bladder infection. He was explains that nothing in the Uni- genius pass before us.♦ 76. There is no doubt that this rum­ verse can move faster than the pled, white-haired, pipe-smoking speed of light. Also, his professor looked deeper into the most famous equation nature of the Universe than any E = mc2, which explains other man. In death he joins a se­ how matter can become lect few – such as Newton, Coper­ energy, and energy can nicus, Archimedes and Pythagoras become matter. Finally, – as a giant in science whose ge­ his space-time bend­ nius changed the course of history. ing theory of gravitation. Taken together, Ein­ The immediate outpouring of stein’s ideas are the ba­ praise for the German-born sci­ sis of all modern physics. entist begins to reveal his place in history. President Eisenhower said, Non-scientists know “No other man contributed so much Einstein was a genius, to the vast expansion of 20th cen­ but don’t really un­ tury knowledge.” Moshe Sharett, derstand many of his the Prime Minister of Israel, stated, theories. The average “The world has lost its foremost person knows that tele­ genius.” There were even eulogies vision and the hydrogen behind the Iron Curtain. Pravda, bomb are the results of the official newspaper of the Soviet his work, but doesn’t Union, described him as, “A great understand how it is so. transformer of natural science.” We are like the nurse at Einstein’s deathbed who Einstein’s achievements are bet­ failed to understand the ter known to his co-workers and great man’s final words students, who still work to under­ that were spoken in Image credit: Orren Jack Turner via the Library of Congress stand, test, and apply his theories. German. She did not Albert Einstein speak German. Most of 2 “Yardsticks” in Neighbor Galaxy Double Universe’s Size alter Baade, an astronomer because all the stars in the Magellanic at the California Institute of Clouds are basically the same dis­ The solution to this mismatch came WTechnology, says the Uni­ tance from Earth, so it suggested that during the wartime blackouts of 1943 verse is twice as large as we thought. the rate at which those Cepheids were in California. Doctor Baade took ad­ He has used the giant 200-inch reflect­ pulsing was a clue to their real bright­ vantage of the darkened skies and ing telescope at Mount Palomar to ness (or luminosity). By comparing how the power of the 100-inch Hooker tele­ measure the scale of the Universe. bright the stars really are, to how bright scope at the Mount Wilson Observa­ they look (their apparent magnitude), tory near Los Angeles to re-examine Baade’s discovery hasn’t come from their distance could be calculated. Andromeda’s globular clusters. simply reading mile markers in space. To properly determine the distance to For example, if an astronomer sees Using special red-sensitive photo­ stars and the scale of the Universe, he a Cepheid in our own Milky Way Gal­ graphic plates Dr. Baade discovered first had to discover that Nature has axy that appears dim, he can observe two populations of stars: created more than one kind of measur­ how fast it pulsates to determine if the • Redder, fainter “Type II” stars in ing tool (“yardstick”). Until a few years star is close or far away. He can use globular clusters near Androme­ ago, there was just one measuring tool Miss Leavitt’s brightness/pulsation re­ da’s center and in its outlying known to astronomers, and it was be­ lationship to do this. If the star pulsates halo (the same arrangement as ing used incorrectly. Oddly enough, it rapidly, then the star really is dim and in the Milky Way) took the wartime blackouts in Los An­ not far away. If the star pulsates slowly, • Bluer, brighter “Type I” variable geles to begin setting things straight. then the star is actually bright, and only stars located in open clusters in (These blackouts were periods of time looks dim because it is very far away. Andromeda’s disk (outer spiral at night when people had to turn off all arms). lights or make certain all lights were After Miss Leavitt completed her blocked by heavy curtains to minimize work, astronomer Solon Bailey dis­ Dr. Baade realized that there must the danger of night-time bombing or covered that the same relationship also be two populations of Cepheids – spying raids. During these times, light seemed to be true for Cepheids found Type I Cepheids more common in the pollution was greatly reduced, and as­ in dense star clusters in our own gal­ disk of a galaxy and Type II Cepheids tronomers could better study light from axy. Next, astronomer Harlow Shap­ more common in the globular clusters. space.) ley standardized the “yardstick”, so he could measure the distance of According to Dr. Baade, Shapley did That first “yardstick” was discovered fast-period and slow-period Cepheids not realize Cepheids in globular clus­ around the turn of the century. It is a both inside and outside these dense ters have a different period-luminosity type of pulsating, variable star called a globular clusters in the Milky Way. relationship compared to Cepheids in Cepheid. Cepheid stars become very open clusters. He made a major error bright and then very dim over a pe­ “Thus a period-luminosity relation when he treated them as if they were riod of several days to several weeks. was established which covered the the same on his yardstick. This would Henrietta S. Leavitt of the Harvard Ob­ whole range of the Cepheid varia­ be similar to treating a yardstick (Type I servatory was studying the Magellanic tion and which was accepted as the Cepheid) exactly the same as a meter Clouds, which are small galaxies out­ period-luminosity relation for the next stick (Type II Cepheid). They are very side of the Milky Way. She noticed that 30 years,” recalled Baade in a speech different measuring tools. brighter Cepheids pulsed slower than at a recent award ceremony of the dimmer Cepheids. This was interesting, Astronomical Society of the Pacific. At Mount Palomar, Baade and his computer assistant Henrietta Swope Unfortunately, Shapley’s yard- recently confirmed that both types - stick had flaws. In 1931, Ed­ of Cepheids are very different types win Hubble began studying the of stars. After recalibrating his mea­ starlight from globular clusters suring sticks, Dr. Baade startled his in Andromeda, a galaxy near peers in 1952 at the Rome meet­ the Milky Way. For some rea­ ing of the International Astronomical son those clusters were burning Union by announcing that Andromeda more dimly than similar clusters was not 800,000 light-years away, as in the Milky Way. This mismatch Hubble thought, but 1.8 million light- meant either the globular clus­ years distant. Likewise, with the two ters in Andromeda are basically measuring sticks sorted out, the Uni­ different than those in our own verse we knew in 1929 to be one bil­ Image credit: Mt. Wilson-Palomar Observato ries photo, courtesy AIP Emilio Segre Visual Archives, Physics Today Collection Milky Way, or Andromeda must lion light-years wide has now doubled This 200-inch Hale telescope at Mt. Palomar, com- be farther than originally calcu- to two billion light-years across. ♦ lated. pleted in 1949, confirmed the size of the Universe. 3 Origin of Everything: Hot Bang or Ageless Universe? as the Universe always Universe. The evolutionary theory away, that motion lengthens the existed, or does it have a claims an initial collection of hot wavelengths, causing the light to Hbeginning, middle and an particles exploded at the dawn of “red–shift”. It’s similar to how the end? It’s difficult to imagine a deep­ time. These particles formed all sound of a retreating locomotive er mystery than this. However, this the Universe’s hydrogen (and per­ drops in pitch as it passes by you. topic was recently discussed at the haps helium) in one gigantic event. meeting of the National Academy In the steady-state theory the ex­ of Sciences in Pasadena, Califor­ Both theories explain – in entirely pansion comes from the continu­ nia. different ways – the fact that the ous bubbling up of the element hy­ Universe is expanding. This ex­ drogen, from empty space at a rate The case for an ageless, steady- pansion was first detected in 1914, of one particle every cubic meter state Universe was presented at when American astronomer Vesto every 300,000 years or so. This hy­ the conference by astrophysicist Melvin Slipher surveyed some gal­ drogen eventually gathers and con­ Jesse L. Greenstein and physicist axies and noticed the light from denses into stars. Through nuclear William A. Fowler of the California all of them was “red-shifted.” All fusions in their cores, stars make Institute of Technology. The steady light travels in waves. In the spec­ all the heavier elements (e.g.