What does the universe really look like? Is Pluto still a planet? Is there life in the galaxy? How do stars live and die? Should we, and can we, colonize space? To answer those questions, three of today’s leading astrophysicists — Neil deGrasse Tyson, Michael A. Strauss and J. Richard Gott — take us on a tour of the cosmos.
Tyson, director of the Hayden Planetarium at the American Museum of Natural History, is passionate about his perennial search for life in the universe, but his scientific mind leaves no space for a romantic view of space. In a few words, he describes a universe that no longer seems as welcoming as we might once have thought.
“It’s a big universe. I want to introduce you to the size and scale of the cosmos, which is bigger than you think. It’s hotter than you think. It is denser than you think. It’s more rarefied than you think. Everything you think about the universe is less exotic than it actually is,” writes Tyson.
“Welcome to the Universe” was inspired by an extremely popular introductory course that Tyson, Strauss and Gott taught together at Princeton. This book “bridges the gap between popular accounts of scientific discovery and textbooks on the subject,” says Tyson.
“There’s a neglected community of science enthusiasts out there who hunger for more. Our book doesn’t simply tell you what’s in the universe; we empower you to understand the operations of nature, the machinery of cosmic phenomena.”
This book has 24 chapters divided into three distinct sections: “Stars, Planets and Life,” “Galaxies” and “Einstein and the Universe.” The first is written by Tyson and the other two by Strauss and Gott respectively. In the first section, Tyson looks at the size and scale of the universe. The narrative is heavy on equations.
This exercise in numbers is daunting, and in an interview Tyson explained: “There is a limit to the number of countable things in the observable universe. That would be like the number of particles in the universe, you could count those and we give that estimate. It’s around 10 to the power of 80 or something like that. So then of what good are numbers bigger than that if there’s nothing to count them with?”
The book introduces us to a brief history of astronomy. Until the 16th century, the popular belief was that Earth was the center of the universe. Polish-born Nicolaus Copernicus, however, claimed in a book that he was pressured not to publish — “On the Revolutions of the Celestial Spheres” — that the Sun was the center of what is now known as the solar system, and that the various planets, including Earth, move in orbits around the sun.
Copernicus’ book was finally printed just before his death in 1543, and was a major event in the history of science. Sixty-six years later Johannes Kepler, a German mathematician, astronomer and astrologer, discovered the first two of his three laws of planetary motion.
His works provided foundations for Isaac Newton’s Universal Law of Gravitation. One of the remarkable facts of this law is that the acceleration of gravity does not depend on the mass of the object being accelerated, either for orbits around the sun or for objects falling in the Earth’s gravitational field. When the Apollo 15 astronauts left for the moon, they took along a hammer and a feather to do an experiment to test this principle.
“The moon effectively has no atmosphere: A very good vacuum exists above its surface, and hence there is no appreciable air resistance,” explains Strauss, professor of astrophysics at Princeton University. “When the astronauts dropped the feather and the hammer simultaneously, they fell at exactly the same rate, just as Newton and (Galileo) had predicted. You can see the video record of their lunar experiment online.”
The study of the physical nature of stars and other celestial bodies is relatively recent. Modern astrophysics began in the 1920s, when scientists were able to measure accurately the spectrum of a star, in other words its electromagnetic wavelengths, in order to understand its chemical composition.
It is interesting that at the turn of the century, women could not be professors and did not have access to many jobs. At the Harvard College Observatory, there was a room filled with women who were “doing what most men considered to be menial work, classifying spectra of all these stars,” writes Tyson.
One of these women, Cecilia Payne, worked on spectra at Harvard for a decade as an assistant before she was eventually appointed a professor. She discovered that the Sun is made mostly of hydrogen. “Astronomy, because of that peculiar history, has a fascinating legacy of early contributions by women,” writes Tyson.
He gives a fascinating account of the controversy triggered by Pluto’s demotion as a planet. It began when Kenneth Chang, a New York Times scientific journalist published an article on Jan. 21, 2001, entitled “Pluto’s not a planet? Only in New York.” This sensational news created a buzz, and Tyson, who was in charge of the Hayden Planetarium, spent three months doing nothing else but handling media queries.
This controversy showed how some scientists under political pressure had lost their critical minds. The president of the International Astronomical Union’s planet-naming commission suggested that Pluto should have dual citizenship!
Dr. Richard Binzel, a professor at the Massachusetts Institute of Technology (MIT) who had devoted part of his career to studying Pluto, was quoted in the article as saying: “They went too far in demoting Pluto, way beyond what mainstream astronomers think.”
Since the 1980s, Pluto had been on the point of beginning to join comets, asteroids and other solar debris. In 1992, a swathe of icy bodies known as the Kuiper Belt was discovered in the solar system. Pluto is part of the Kuiper Belt, and is made mostly of ice.
“Over these past decades, we’ve just been kind to Pluto, keeping it in the family of planets, even though we knew in our hearts that it didn’t fit anywhere,” writes Tyson. “Pluto’s existence now makes sense. It has brethren. It has a home. Pluto is a Kuiper Belt object.” In 2006, the Astronomical Union demoted Pluto to dwarf planet and confirmed the existence of eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Gott concludes this guided tour of the cosmos with an impassioned plea to begin colonizing Mars: “We should be doing that quickly while we still have a space program. The goal of the human spaceflight program should be to improve our survival prospects by colonizing space.
“This could be achieved at a reasonable cost… You just have to find a handful of astronauts… who would rather be founders of a Martian civilization than return to be celebrities back on Earth.”
“Welcome to the Universe” describes the latest discoveries in astrophysics that continue to get more intriguing and challenging. The authors take readers, preferably with a grounding in physics, on a unique intergalactic voyage from our solar system to the outermost frontiers of the universe.
• life.style@arabnews.com
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