Astronomy For Dummies. Maran Stephen P.

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СКАЧАТЬ theory of gravity, which passes experimental tests that Newton’s theory flunks. Newton’s theory was good enough for commonly experienced gravity, like the force that made the apple fall on his head (if it really hit him). But in other respects, Newton’s theory was hit or miss. Einstein’s theory is better because it predicts everything that Newton got right, but also predicts effects that happen close to massive objects, where gravity is very strong. Einstein didn’t think of gravity as a force; he considered it the bending of space and time by the very presence of a massive object, such as a star. I get all bent out of shape just thinking about it.

      Newton’s concept of gravity explains the following:

      ❯❯ Why the Moon orbits Earth, why Earth orbits the Sun, why the Sun orbits the center of the Milky Way, and why many other objects orbit one object or another out there in space

      ❯❯ Why a star or a planet is round

      ❯❯ Why gas and dust in space may clump together to form new stars

      Einstein’s theory of gravity, called the General Theory of Relativity, explains everything that Newton’s theory does plus the following:

      ❯❯ Why stars visible near the Sun during a total eclipse seem slightly out of position

      ❯❯ Why black holes exist

      ❯❯ Why gravitational lensing is found when we observe deep space

      ❯❯ Why Earth drags warped space and time around with it as it turns, an effect that scientists have verified with the help of satellites orbiting Earth

      ❯❯ How a collision of two black holes produces gravitational waves that shake things up even billions of light-years away

      You find out about black holes in Chapters 11 and 13, and you can read up on gravitational lensing in Chapters 11, 14, and 15 without mastering the General Theory of Relativity.

      You’ll get smarter if you read every chapter in this book, but your friends won’t call you Einstein unless you let your hair grow, parade around in a messy old sweater, and stick out your tongue when they take your picture.

      Space: A Commotion of Motion

      Everything in space is moving and turning. Objects can’t sit still. Thanks to gravity, other celestial bodies are always pulling on a star, planet, galaxy, or spacecraft. Some of us are self-centered, but the universe has no center.

      For example, Earth

      ❯❯ Turns on its axis – what astronomers call rotating – and takes one day to turn all the way around.

      ❯❯ Orbits around the Sun – what astronomers call revolving — with one complete orbit taking one year.

      ❯❯ Travels with the Sun in a huge orbit around the center of the Milky Way. The trip takes about 250 million years to complete once, and the duration of the trip is called the galactic year.

      ❯❯ Moves with the Milky Way in a trajectory around the center of the Local Group of Galaxies, a couple of dozen galaxies in our neck of the universe.

      ❯❯ Moves through the universe with the Local Group as part of the Hubble Flow, the general expansion of space caused by the Big Bang.

      The Big Bang is the event that gave rise to the universe and set space itself expanding at a furious rate. Detailed theories about the Big Bang explain many observed phenomena and have successfully predicted some that hadn’t been observed before the theories were circulated. (For more about the Big Bang and other aspects of the universe, check out Part 4.)

      Remember Ginger Rogers? She did everything Fred Astaire did when they danced in the movies, and she did it all backward. Like Ginger and Fred, the Moon follows all the motions of Earth (although not backward), except for Earth’s rotation; the Moon rotates more slowly, about once a month. And it performs its tasks while also revolving around Earth (which it does about once a month).

      And you, as a person on Earth, participate in the motions of rotation, revolution, galactic orbiting, Local Group cruising, and cosmic expansion. You do all that while you drive to work, whether you know it or not. Ask your boss for a little consideration the next time you run a few minutes late.

Chapter 2

      Join the Crowd: Skywatching Activities and Resources

      IN THIS CHAPTER

      ❯❯ Joining astronomy clubs, using the Internet, downloading apps, and more

      ❯❯ Exploring observatories and planetariums

      ❯❯ Enjoying star parties, eclipse tours and cruises, telescope motels, and dark sky parks

      Astronomy has universal appeal. The stars have fascinated people everywhere from prehistoric times into the modern age. Early observations of the sky led to all sorts of theories about the universe and attributions of power and purpose to the movements of stars, planets, and comets. As you look up at the sky, hundreds of thousands of people worldwide watch with you. When it comes to skywatching, you’re not alone. Many people, organizations, publications, websites, smartphone apps, and other resources are at your disposal to help you get started, to keep you going, and to help you participate in the great work of explaining the universe.

      In this chapter, I introduce you to these resources and give you suggestions on how you can get started. The rest is up to you. So join in!

      

When you know the resources, organizations, facilities, and equipment that can help you enjoy astronomy more deeply, you can move comfortably to the science of astronomy itself – the nature of the objects and phenomena out there in deep space. I describe the equipment you need to get started in Chapter 3.

      You’re Not Alone: Astronomy Clubs, Websites, Smartphone Apps, and More

      You have plenty of readily available information, organizations, people, and facilities to help you get started and remain active in astronomy. You can join associations and activities to help researchers keep track of stars and planets. You can attend astronomy club meetings, lectures, and instructional sessions, which allow you to share telescopes and viewing sites to enjoy the sky with others. You also can find magazines, websites, books, computer programs, and smartphone apps with basic information on astronomy and current events in the sky.

Joining an astronomy club for star-studded company

      The best way to break into astronomy without undue effort is to join an astronomy club. Clubs hold meetings where old hands pass along tips on techniques and equipment to beginners and scientists present talks. Members likely know where to get a good deal on a used telescope or binoculars and which products on the market are worth buying. (See Chapter 3 for more.)

      Even better, astronomy clubs sponsor observing meetings, usually on weekend nights and occasionally on special dates during a meteor shower or another special event. An observing meeting is the best place СКАЧАТЬ