Each plant travles around the sun-or revolves-in its own path, or orbit. The father the plant is from the sun, the longer it takes to revovle.
Earth is the third planet from the the sun. It takes 365 days (one year) to make one revolution.
The planets spin like tops as they revolve around the sun.Some planets spin very fast；Some spin slowly.
Earth spins around, or rotates once every 24 hours. This is what makes day and night.
The great power of the rockets gave the bus enough speed to break away from Earth's gravity. We zoomed through the atmosphere into dark, aurless space.
Gravity is the force within a star or planet that pulls objects toward it is center.
Once we were going fast enough, the Friz turned off the rockets. Right away, strange things started to happen. I had been holding Roxxo on my lap. But I let go of him for a second-and he floated up to ceiling!
Soon we were all bumping into one another as tumbledaround insudethe space bus. We had to hold on to seat backs to steaty ourselves.
Arnold was floating upsude down near a window. “Look at Earth!”he said. “It's so beautiful from up here.”
We all floated over to see. Earth was a blue-and-brownish-green sphere surrounded by swirling white clouds. Home sweet home.
Earth is the perfect distance from the sun for life-it's not too hot and not too cold. It has water and gases, such as oxygen, that living things need.
It also has an atmosphere to protect ut from harmful rays from the sun.
All of this makes Earth a perfect place for animals and plants to live and grow.
“Earth is one of the four rocky planets, along with Mercury, Venus, Mars,”the Friz said. “But you can see, most of the surface is covered with water. Some people think a better name fur our planet would be Ocean.”
There was a lot of water covering Earth. I couldn’t believe how small the planet looked from space.
“Hey- there’s the moon! Wanda called. “Or at lest half of it.”
“The whole moon is there, Wanda,”said MS. Frizzle“But we only see the part that is lit up by the sun’s light.”
I remembered that the moon is covered with rocks.“MS. Frizzle,”I said,“could we stop here? I always wanted some moon rocks for my colletion.”
“Sure thing, Carlos!”MS. Frizzle fireed some engunes to change our direction. We slowed down as we camenear the bright side of the moon. It was covered with deep pits and craters that looked like huge bowls. We landed in one of the wude craters with a thud.
On July 20,1969,American astronaut Neil Armstrong became the first person to set foot on the moon. He was one of three men in the Apollo II crew.
Million and million of people a round the world watch on TV Armstrong said,“Thats one small step for man, one giant leap for mankind.”
The pull of gravity depends on the mass of the planet, moon, or other body in space. Usually, the larger the body, the more mass it has. The moon is much smaller than Earth, so it has much less gravity.
If you weigh 75 pounds on Earth, you would weugh only 12 1/2 pounds on the moon.
如果你在地球重75公斤,你將在月亮重12 1/ 2公斤。
“Wheee!”called Ralphie.“This is better than a trampoline.”He jumped easily off the ground, came back down, then bounced up.
Rocco was speeding farther and farther into space. If we get going fast, we'd never be able to catch up with him.
As soon as everyone was aboard space bus,ms. Frizzle fired the rockets and we took off after my little robot. Once we were out of orbit we were no longer weightless. We could walk around on the bus again.
Hey,Ms. Frizzle, what's that bright star ahead?”Phoebe asked.
“It's not a star, Phoebe,”the Friz told her.“Thats the planet Venus. Venus is the third brughtest object we can see from Earth after the sun and the moon.
A star is a hot, gloeing ball of gas that gives off heat and light.
D.A. had done her report on Venus. She told us Venus is so bright because the layers of thick clouds surrounding it reflect a lot of light from the sun.
Soon we could see the swirling clouds of Venus and it looked as if Rocco washeading straight into them.
Suddenly I remembered Rocco's remote control. It was in my pocked. Maybe I could use it to steer him away from those deadly clouds. I had to act fast before the planet's gravity pulled him in.
I pushed the reverse button. Right on! Rocco spun around and headed back toward space-bus.
“You did it,Carlos!”Tim yelled.“Now wejust have to figure out how to get him unside once he gets close enough.”
“Follow that robot, please!”I called Ms. Frizzle. The space-bus zoomed off, leaving Venus in our dust.
Rocco was going so fast, soon he was just a dot in space.
“Hey, Carlos, can you use Rocco's radio signal to follow him?”Ralphie asked.
“We can try,”I said. I pushed the voice button. We heard a faint sound.“Yip,yip,yip.”
“I've located Rocco on the radar screen,”Ms. Frizzle said. She set a new course and fired the contro thrusters.
“You bet! You're seen pictures of astronauts repairing seteilites out inspace, right?”Ms. Frizzle asked.“Just like them, we'll be wearing tether wires. We'll be attached to the Magic Space Bus so we can’t float off.”
“But we'll burn up in the sun's heat!”I protested.
“Not so Carlos,”the Friz replied. She reached into a compartment and pulled out two shiny gold coated umbrellas.“These parasols are made of special material that reflects heat and light. they'll protect us from the sun's rays.”
Ms. Frizzle and I got into our space suits and entered the airlocj, a small room vwith a hatch over head.
On our way back to Mars, we whizzed past Venus and the moon. I wished I had gotten some moon rocks, but I was glad to have Rocco back. Maybe we'd have better luck colleting rocks on Mars.
In empty space, there is no weather! That means no cloudy days, so a lot of sunshine is available to make solar electricity.
“Cool! ”D.A. said“I'd like to work in a space station someday.”
Boulders came rushing atus as the Friz wildy punched buttons on the instrument panel. The bus zigged right, then zagged left, narrowly missing a huge asteroid. “Aha!”Ms. Frizzle cried. “Gotcha!”She didn't look scared.