Neil de Grasse Tyson - Merlins Tour of the Universe

A M AIN S TREET B OOK
PUBLISHED BY DOUBLEDAY
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M AIN S TREET B OOKS , D OUBLEDAY , and the portrayal of a building with a tree are trademarks of Doubleday, a division of Bantam Doubleday Dell Publishing Group, Inc.

Library of Congress Cataloging-in-Publication Data

Tyson, Neil de Grasse.
Merlins tour of the universe : a skywatchers guide to everything from Mars and quasars to comets, planets, blue moons and werewolves / Neil de Grasse Tyson.
p. cm
AstronomyMiscellanea. I. Title
[QB52.T98 1997]
520DC21 96-37200

eISBN: 978-0-307-78408-7

Copyright 1989, 1997 by Neil de Grasse Tyson

All Rights Reserved

v3.1_r1

T o all people
who recognize herein
a question of their own

M ERLINS TOUR OF THE UNIVERSE is a collection of questions asked by the general public and answered by Merlin, a visitor from the Andromeda galaxy who is as old as Earth and has observed the major scientific achievements of recorded Earth history.

Merlin writes a question-and-answer column for Star Date, the astronomy magazine published for the lay reader by the McDonald Observatory of the University of Texas at Austin. Most of the material in Merlins Tour of the Universe first appeared in this column.

This book is not intended to be an astronomy tutorial. Its focus is guided entirely by questions asked by interested readers who have ranged from age four to age ninety. I have written these answers for the enjoyment of my readers and with my lifes enthusiasm for this beautiful and grand home that is our universe.

M ERLIN WAS BORN nearly five billion years ago on the planet Omnisciaone of a five-planet system in orbit around the star Draziw, two million light years away in the Andromeda galaxy. Merlins birth coincided with the formation of the solar system in the Milky Way galaxy that contains planet Earth.

Most residents of Omniscia are excited by science, and all residents have an endless thirst for knowledge. Merlin earned degrees in astrophysics, history, geophysics, chemistry, and philosophy at Omniscias planetwide Universe-ity. Throughout Merlins youth, Merlin was intrigued by the solar system that was born to the Milky Way when Merlin was born to Omniscia. Merlin later took a keen interest in scientific thought as conceived by humans on the planet Earth.

Merlin noticed that humans were curious about the scientists understanding of the universe but that many did not know where or how to find the answers to their questions. Sharing knowledge and wisdom is as fundamental as acquiring knowledge and wisdom. Merlin chose to visit Earth to spread science to those humans that share, along with Omniscians, that unquenchable cosmic thirst.

U NLIKE MANY OTHER PLANETS in the universe, Earth is a dynamic place.

There are oceans of water that are tidally induced by the Moon to slosh upon the continental shelves. The continents slide determinedly upon a mantle that is the source of magma that erupts from volcanoes. There are plants and animals and microorganisms that live and reproduce in temperatures that range from the frozen Arctic to hundred-degree desert days. All this activity unfolds under nearly six quadrillion tons of a turbulent atmosphere that spawns storms, drought, electrical discharges, and erosion.

Curiously, this environment represents quite hospitable conditions when compared with other places such as Venus, Pluto, and, of course, the binary planet Anoxia in the Draziw system.

The tilted Earth rotates and wobbles and bobs its way through space in orbit around the Sun with the Moon tightly tethered nearby.

Dear Merlin,

What would happen if the Earth suddenly stopped rotating?

J ONATHAN S WANN

S AN D IEGO , C ALIFORNIA

A mong other things, we would all fall over and roll due east at about 800 miles per hour (the exact speed depends on your latitude on Earth). The Pacific Ocean would wash up onto North and South America and the Atlantic Ocean would wash up onto Europe and Africa. Many other unpleasant things would also happen.

Once it all settled down, the Earth day would equal the Earth year and there would be no tornadoes, hurricanes, cyclones, or typhoons.

Dear Merlin,

If Earth were to explode tomorrow, what would happen to the orbits of the other planets?

P ATRICK K ANE

A USTIN , T EXAS

M erlin prefers to consider what would happen to Earths orbit if another planet were to explode tomorrow.

The exact orbit of Earth is controlled by the Suns mass and the mass of all remaining planets. An objects mass and its distance is all we need to know to completely determine the effects of its gravity on Earth.

The Sun is a thousand times more massive than all planets combined, and is relatively close to Earth. This veritable cosmic arrangement will permit Earths orbitin the face of any other planets armageddonto remain within 99.999 percent of its current path around the Sun.

Dear Merlin,

What is the exact shape of the Earth? Im told it is not a sphere.

R OBERT M C K INNEY

A LBANY , N EW Y ORK

E arth is slightly flattened at the poles and slightly wider below the equator than at the equator. This shape is unflatteringly referred to as an egg-shaped oblate spheroid.

Dear Merlin,

If lines of longitude on Earth help determine boundaries of time zones, and if all lines of longitude converge the farther north and south of the equator one travels, then what time is it at the poles where all lines of longitude meet?

D EAN J ORDAN

M ONTREAL , Q UEBEC

I t is time to go back home.

There are no official time zones at the poles.

Dear Merlin,

As I understand it, Earths core was very hot billions of years ago and its been cooling ever since. Is it possible that the core will cool completely? If so, what would the consequences be?