This is the story of how Max the Dog helped people return to the Moon — this time, to stay.

It all began on the morning of the parade. Max had just returned from his trip to the Space Station. He was a hero — after all, none of the astronauts could have come home safely without him.

As Max's car drove along Pearl Street, Max looked to the west, and he began to howl just as the Moon set over the mountains.

Phases of the Moon

Do you see the Moon setting over the mountains in the picture of Max's parade? To appreciate what we're seeing, we need to understand the Moon's cycle of phases.

Each cycle takes about a month. That's where the word month comes from; think of it as a special way of saying "moonth."

A cycle begins with new moon, when we can't see the Moon at all. A couple of days after a new moon, a thin crescent [??] moon appears in the early evening sky. Then, each day, we see more of the Moon's face and the Moon stays up later at night. About a week after new moon comes first quarter [??] phase, when the Moon shows half its face and stays up until around midnight. A few days later, the Moon's face is bright except for a thin, dark crescent; we call this a gibbous [??] (pronounced with a hard g as in "gift") moon. Full moon [??] comes about two weeks after new moon; we can see the Moon's full face all night long.

After full moon, the Moon goes back through the same phases but with its opposite side illuminated and appearing only later at night. A few days after full moon we have another gibbous moon. A week after full moon comes third quarter moon; you can't see the third quarter moon at bedtime, because it doesn't rise until around midnight. A few days later, we can see only a thin crescent moon * in the early morning sky. Then the phases begin again with another new moon. Do you want to know why the Moon goes through phases? Try the activity on p. 30.

* * *

In truth, Max howled because he heard a siren. He always howls at sirens. But the TV reporters didn't know that, so they thought he was howling at the Moon.

A reporter spotted Max's friend, Tori.

"Why did Max howl at the Moon?," he asked.

"I'm not sure," said Tori. "Maybe it's because he wants to go there."

The Moon in the Daytime

Children's stories often make it seem like the Moon and bedtime always go together. But there are many nights when we cannot see the Moon at bedtime and many days when we can see it in the daytime sky.

Each day, the Moon rises in the east and sets in the west much like the Sun. The times of moonrise and moonset depend on the Moon's phase.

A new moon rises and sets with the Sun, which is why we cannot see it at all: in the daytime it is hidden in the Sun's glare and at night it is below our horizon. As the phases progress from new to full — which we call the "waxing" (getting fuller) phases — the Moon rises and sets later and later compared to the Sun. A waxing crescent moon trails a couple of hours behind the Sun in the sky, making it visible in the late afternoon and early evening. A first quarter moon rises around noon and sets around midnight, making it visible for much of the afternoon and all of the evening. A full moon rises and sets opposite the Sun, keeping it above the horizon all night long.

The pattern continues with the "waning" (getting less full) phases. For example, a waning gibbous moon rises a few hours after sunset and sets a few hours after sunrise, while a third quarter moon rises around midnight and sets around noon. If you look closely, you'll see that it is a waning gibbous moon over Max's parade, which is why it is visible in the mid-morning sky.

Many newspapers show the Moon's daily phase and times of moonrise and moonset.

* * *

Well, Tori's "maybe" was good enough for TV. By the next day, Max's dream of going to the Moon was all over the news. And because no one had been to the Moon in a long time, it seemed like it was about time for someone — or some dog — to go.

Leaving the Earth

If you throw a ball into the air, it falls back to the ground. But the harder and faster you throw it upward, the higher it goes before coming down. If you had magical strength, you could throw a ball so hard and so fast that it would never come back down. We would say that you gave the ball escape speed, because it went upward fast enough to escape from the Earth and go out into space.

The escape speed from the Earth is very fast — about 25,000 miles per hour (40,000 kilometers per hour). That is much faster than anyone can really throw a ball. It is faster than any airplane travels. But big rockets can go that fast.

* * *

It's not easy to go to the Moon. It takes big rocket engines to get a spaceship off the Earth. It takes careful planning to make sure the astronauts reach the Moon and come back safely. And it costs a lot of money.

But everywhere Max went, crowds chanted, "Send Max to the Moon!" People wrote letters to the President. So a new moonship was built and assembled at the Space Station.

A Trip to the Moon

Past Moon missions took astronauts directly from the Earth to the Moon with big, multistage rockets. Future Moon missions may include a stop at the Space Station. (The Space Station will require modifications in order to support a Moon mission.)

The Space Station makes Moon trips easier in two ways. First, it makes it easier to put a large moonship in orbit. Without the Station, we'd need a huge rocket to get the moonship into space. With it, we can use smaller rockets to launch the moonship in pieces, then assemble the pieces at the Station.

Second, starting from the Station gives the moonship a head start on achieving escape speed. The Space Station orbits about 250 miles (400 km) above the Earth at a speed of about 17,000 miles per hour (27,000 kilometers per hour). Thus, a moonship docked at the Space Station already is traveling this fast, so its engines need only to boost it an additional 8,000 miles per hour (13,000 kilometers per hour) to reach escape speed.

* * *

Tori gave Max the good news. "You are going to go to the Moon," she said. "I sure hope they let me come with you."

Why Is the Moon a "moon"?

Our Moon is a "moon" because it orbits the Earth. Planets orbit the Sun, and there are nine planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Moons orbit planets, and there are dozens of moons in our solar system. Mercury and Venus are the only planets with no moons at all.

The Moon is about 2,160 miles (3476 kilometers) in diameter, which is a little more than one-fourth of the Earth's diameter. The Moon's average distance from Earth is about 239,000 miles (384,000 kilometers). The photographs below of the Earth and Moon show their relative sizes to scale. If you wanted to show the distance between them on the same scale, you'd need to hold these two pictures about 1.9 meters (6 feet, 3 inches) apart.

* * *

Max went into astronaut training again. The other astronauts were glad to have Max back. Max made the long training sessions seem fun.

Some how, he always managed to find a stick. He loved to play fetch while the...