Monday
Monday: Where Did All This Come From?
Rocket lines up a lamp, a ball, an orange and a handful of pebbles on the Sky Deck step. "The Sun, Earth, the Moon, some asteroids."
Raven studies the row. "What do you notice? They all go around the lamp the same way. Why the same way?"
"Because that is how they started?" Rocket says, then stops. "Wait. How did they start?"
Nova hovers over the lamp. "Gravity pulls things together," she says. "Last week it held the system. Think about what it did first."
"Before there were planets," Raven says slowly, "there must have been just stuff. Dust. Gas."
Rocket sweeps the pebbles into a pile. "And gravity pulled the stuff into a pile." Nova glows. "A spinning pile. Find out what spinning does."
A cloud that fell in on itself
Last week you learned that gravity holds the solar system together. This week you learn that gravity built it.
The Next Generation Science Standards say it this way. The solar system appears to have formed from a disk of dust and gas, drawn together by gravity.
NASA tells the story for students. It starts about 4.6 billion years ago with a cloud of dust that was part of a larger cloud called a nebula.
At some point the cloud collapsed. It fell in on itself, creating a disk of material around its center.
At the center, the pressure grew so great that hydrogen atoms began to fuse into helium, releasing a tremendous amount of energy. Our Sun was born.
Leftovers become planets
The Sun took in more than 99 percent of all the material in the disk. But there was still some left over.
Bits of this material clumped together because of gravity. Big objects joined bigger objects, forming still bigger objects.
Some grew big enough to become spheres. Those spheres became the planets and dwarf planets.
Rocky planets like Earth formed near the Sun, because icy and gaseous material could not survive close to all that heat.
Gas and ice collected farther away, creating the gas and ice giants.
- Read the question.
- Tap your answer.
| Statement | True or false? |
|---|---|
| The Sun took in more than 99 percent of the material in the disk. | ? |
| The planets formed before the cloud collapsed. | ? |
| Bits of leftover material clumped together because of gravity. | ? |
| Gas and ice giants formed close to the Sun. | ? |
Leave three outside the pile. Those are your planets. Write what the pile and the three leftovers stand for.
The facts this week come from NASA at science.nasa.gov and spaceplace.nasa.gov, from OpenStax Astronomy at openstax.org and from the NGSS at nextgenscience.org.
Write why ice could gather far from the young Sun but not close to it.
Good start. Tomorrow you find out what spinning did to the cloud, and why that explains the planets' paths.