My Favorite Universe - Internet Archive

TopicScience& Mathematics“Pure intellectual stimulation that can be popped intothe [audio or video player] anytime.”—Harvard MagazineMy FavoriteUniverse“Passionate, erudite, living legend lecturers. Academia’sbest lecturers are being captured on tape.”—The Los Angeles Times“A serious force in American education.”—The Wall Street JournalCourse GuidebookProfessor Neil deGrasse TysonHayden Planetariumand Princeton UniversityProfessor Neil deGrasse Tyson is the Frederick P. RoseDirector of the Hayden Planetarium at the American Museumof Natural History in New York City. Professor Tyson, whoholds a Ph.D. in Astrophysics from Columbia University, haswritten prolifically on cosmology for the general public. Hiscoauthored book, One Universe: At Home in the Cosmos,won an American Institute of Physics Science Writing Award.THE GREAT COURSES Corporate Headquarters4840 Westfields Boulevard, Suite 500Chantilly, VA 20151-2299USAPhone: 1-800-832-2412www.thegreatcourses.comCover Image: NASA, ESA, and The Hubble Heritage Team (STScI/AURA).Course No. 158 2003 The Teaching Company.PB158ASubtopicAstronomy

PUBLISHED BY:THE GREAT COURSESCorporate Headquarters4840 Westfields Boulevard, Suite 500Chantilly, Virginia 20151-2299Phone: 1-800-832-2412Fax: 703-378-3819www.thegreatcourses.comCopyright The Teaching Company, 2003Printed in the United States of AmericaThis book is in copyright. All rights reserved.Without limiting the rights under copyright reserved above,no part of this publication may be reproduced, stored inor introduced into a retrieval system, or transmitted,in any form, or by any means(electronic, mechanical, photocopying, recording, or otherwise),without the prior written permission ofThe Teaching Company.

Neil deGrasse Tyson, Ph.D.The Frederick P. Rose Director,Hayden Planetarium,American Museum of Natural History,and Visiting Research Scientist and Lecturer,Princeton UniversityProfessor Neil deGrasse Tyson was bornand raised in New York City, where hewas educated in the public schools throughhis graduation from the Bronx High School of Science. Tyson went on toearn his B.A. in Physics from Harvard and his Ph.D. in Astrophysics fromColumbia University.Tyson’s professional research interests include star formation, explodingstars, dwarf galaxies, and the structure of our Milky Way. Tyson obtains hisdata from telescopes in California, New Mexico, Arizona, and the AndesMountains of Chile.In addition to dozens of professional publications, Dr. Tyson has written,and continues to write, for the public. Since January 1995, he has writtena monthly essay for Natural History magazine under the title “Universe.”Tyson’s recent books include a memoir, The Sky Is Not the Limit: Adventuresof an Urban Astrophysicist; the companion book to the opening of the newRose Center for Earth and Space, One Universe: At Home in the Cosmos(coauthored with Charles Liu and Robert Irion), which won the AIP sciencewriting prize for 2001; and a playful question-and-answer book on theuniverse for all ages, titled Just Visiting This Planet. Also, premiering inthe fall of 2004, will be a four-part PBS-NOVA special on Cosmic Origins,hosted and narrated by Tyson.Tyson’s contributions to the public appreciation of the cosmos have recentlybeen recognized by the International Astronomical Union in its of¿cialnaming of asteroid “13123 Tyson.” On the lighter side, Tyson was votedi

“Sexiest Astrophysicist Alive” in the November 14, 2000, issue of PeopleMagazine, the publication’s annual “Sexiest Man Alive” issue.Tyson is the ¿rst occupant of the Frederick P. Rose Directorship of theHayden Planetarium, and he is a Visiting Research Scientist in Astrophysicsat Princeton University, where he also teaches. Tyson lives in New York Citywith his wife and two children. Ŷii

Table of ContentsINTRODUCTIONProfessor Biography .iCourse Scope .1LECTURE GUIDESLECTURE 1On Being Round .3LECTURE 2On Being Rare¿ed .8LECTURE 3On Being Dense .14LECTURE 4Death by Black Hole .19LECTURE 5Ends of the World .24LECTURE 6Coming Attractions .28LECTURE 7Onward to the Edge.32LECTURE 8In Defense of the Big Bang.37LECTURE 9The Greatest Story Ever Told .42LECTURE 10Forged in the Stars .47iii

Table of ContentsLECTURE 11The Search for Planets .52LECTURE 12The Search for Life in the Universe .56SUPPLEMENTAL MATERIALTimeline .62Glossary .71Biographical Notes .87Bibliography .91iv

My Favorite UniverseScope:This series of lectures discusses 12 topics based on 12 hand-pickedessays out of 100 or so written for Natural History magazine since1995. Although they do not follow a particular curriculum, theynonetheless represent the professor’s favorite cosmic subjects. And, notsurprisingly, they represent topics for which the general public harbors asustained and insatiable interest.The dozen lectures are thematically arranged in four groups of three. The¿rst group might be entitled “On Being.” Here, Professor Tyson introducesthe fundamental properties of matter and energy and the forces that shapethe cosmos. Describing these properties and forces as though they areprotagonists on a cosmic stage, Tyson shows how the same laws of physicsdiscovered here on Earth reveal themselves elsewhere in the universe,lending extraordinary con¿dence to the enterprise of science.The next group of three lectures comes under the heading “CosmicCatastrophes.” Here, Professor Tyson highlights a battery of destructivecosmic phenomena and the role catastrophe has played in the history of lifeon Earth and in the history of Earth as a planet. The lectures include detaileddescriptions of all the things that are bad for you, including black holes, thedeath of the Sun, and killer asteroids.The next group of three lectures might be called “The Big Bang.” For theselectures, Professor Tyson examines the frontier of our understanding of theuniverse and asks our most basic questions: How did our universe get here?How has it evolved in the past, and how will it evolve in the future?Finally, the last group of three lectures addresses the most intriguing questof them all: “The Search for Life in the Cosmos.” Does life exist elsewhere?In what environments would we expect to ¿nd life? What would that life belike? Would we recognize alien life if we saw it?1

ScopeThe mission of the dozen lectures in My Favorite Universe is to pique yourinterest in some of the most fascinating and fundamental questions everasked—questions that have been with us across time and across cultures. Inthe end, we will know that we have succeeded when “my favorite universe”becomes “your favorite universe.” Ŷ2

On Being RoundLecture 1Look around at all the round things in the world. Is there anythingnature makes that’s not round? Yes, there is. There are a few things. Toname a couple, crystals are not round. Plus, you have fracture rocks.Those have angles to them. But, by and large, if you look around in thecosmos, there are very few things that make angles.Let us begin by describing the property of “roundness.” What forcestend to shape objects into roundness, and why is a sphere the mostef¿cient shape that objects can take? From our discussion of spheresin nature on Earth, we move to spheres in the cosmos. Some planets areperfect spheres, but others are not, which in itself tell us something abouttheir environments. As you will see, our description of roundness will takeus across the cosmos.Many natural objects, however,are round, such as soap bubbles,stars, planets, and galaxy halos.Even the observable universe isa perfect sphere, centered on us. Water droplets on glass.This “roundness” is the resultof forces that want to shape anobject in such a way that the surface is minimized. Think, again, of soapbubbles. No matter the cavity through which you blow the soapy liquid, whatcomes out the other side is a sphere. The sphere is the shape that encloses the3 Corel Stock Photo Library.Why are so many things in the universe round? The forces that makethings round operate on small and large scales. The term round refers tothe energy of a body. Energy tends to descend to the lowest energy stateit can; for example, think of ahouse of cards. Some things inthe universe, such as crystals, arenot round; this fact also tells ussomething about these objects.

largest volume with the least surface. If the bubble were any other shape, itwould have to stretch itself to cover the surface area. Any other shape wouldnot be as strong as a sphere; it would be thinner in one place than another,and the bubble would pop.This generalized feature is also revealed in a cube. Some parts of the cubeare more distant from the cube’s center than others. Every corner is fartherfrom the center than the middle of the cube’s sides, which weakens the sides.If the cube were an orb that had gravity like a planet the corners would bemountains, and the forces that had enabled gravity to have made the planetin the ¿rst place would tend to make those mountains smaller. A rock onthe mountain would roll down and ¿ll up the center of the orb. This processwould continue until the cube much more closely resembled a sphere.Lecture 1: On Being RoundOther spheres in the universe include raindrops, which are not reallytear-shaped but perfect spheres. The force that holds a raindrop together issurface tension the boundary between a liquid and the air. In forming thatboundary, the molecules of the liquid grab onto each other to establish thesurface. The act of establishing the surface creates a tension that wraps theliquid. When it falls, the raindrop wraps itself into a perfect sphere, onceagain, making itself the most ef¿cient shape that it possibly can.Another perfect sphere is a ball bearing, but how is one made? It can’t beproduced with a lathe, because it is too small. Ball bearings can be madeby dropping lique¿ed metal down a tube. As the metal travels down thetube, it cools and hardens into a perfect sphere. If you were in a weightlessatmosphere, such as the space station, you could squeeze the lique¿ed metalfrom an eyedropper, and it would cool and harden and form a perfect sphereright in front of you. In fact, in a weightless atmosphere, you could producethe most perfect ball bearings ever made. Mercury is the only metal that isliquid at room temperature, but its surface tension is so high that it forms asphere under normal conditions on Earth. Think of the toys that children usedto play with in which a mercury bead traveled through a maze. If a spheremaximizes volume and minimizes surface area in other words, given thata sphere is the most ef¿cient shape why isn’t everything a sphere? Whynot packaging in the grocery store, for example? Because spheres roll, that’swhy. Can you imagine trying to stack round boxes of Cheerios?4