Learning Target I – I can model gravity is caused by mass in the Solar System.
Gravity Articles II
What keeps satellites from falling out of the sky?
Ask Smithsonian Smithsonian.com November 18, 2015
You asked us, “What keeps satellites from falling out of the sky?”
Over the last half-century, more than 2,500 satellites have followed the first one into space. What keeps them all afloat? It is a delicate balance between a satellite’s speed and the pull of gravity.
Satellites are basically constantly falling. Crazy, right?
They fall at the same rate that the curve of the Earth falls away from them if they’re moving at the right speed. Which means instead of racing farther out into space or spiraling down to Earth, they hang out in orbit around the planet.
Corrections are often needed to keep a satellite on the straight and narrow.
Earth’s gravity is stronger in some places than others. Satellites can get pulled around by the sun, the moon and even the planet Jupiter.
You would think gravity was enough to deal with. But, satellites in low earth orbit such as the Hubble Space Telescope can also get pulled out of their orbit by drag from the atmosphere.
Not to mention the ongoing game of Frogger that satellites have to play. That’s so they can avoid space junk and other high flyers.
Heads up!
Plant Gravity
October 11, 2007
A listener asks: Regardless of how you plant a seed, the roots always grow downward and the shoots upward, so how does the plant orient itself?
The gravity of plants. I’m Bob Hirshon and this is Science Update.
Regardless of which way you plant a seed, its roots always grow downward and its stem upward. This inspired listener B-J Stone of White Plains, New York to ask how the seedling manages to orient itself. We turned to plant physiologist Cary Mitchell of Purdue University. He says that gravity is the environmental signal plants use to determine up and down.
Cary Mitchell (Purdue University) – If you were to launch a seed into space, in the absence of gravity, you would get an aimless germination and it would just wander.
Hirshon – But in the presence of gravity here on earth, dense starchy bodies inside the plant settle to the bottom of each cell. The plant senses up and down based on the location of these dense bodies, triggering its roots to grow toward water and mineral nutrients and its shoots to grow toward the sun. I’m Bob Hirshon, for AAAS, the science society.
Chaos Among the Planets
Kate Ramsayer, From Science News for Kids June 1, 2005.
Once upon a time, billions of years ago, the giant planets in our Solar System took different paths around the Sun than they follow now.
Jupiter, Saturn, Uranus, and Neptune were once grouped together, closer to the Sun, says an international team of scientists. Under the influence of gravity, the planets broke out of their original orbits and began violently rearranging the outer Solar System.
It’s “a fairy tale of the early Solar System,” says Hal Levison. He’s a planetary scientist with the Southwest Research Institute in Boulder, Colo., and was one of the researchers who developed a computer simulation of the planets’ movements.
As the scientists tell it, the tale starts a few million years after the Solar System’s birth.
At first, the four giant planets had compact orbits. Neptune, for example, was only half as far away from the Sun as it now. A slowly circulating band of ice, dust, and gas lay beyond these planets.
Ice, dust, and gas might not seem like much of a match for huge planets. But the researchers say that the pull of gravity between the particles and the planets caused the planets to gradually break out of their tight-knit group. Jupiter moved a bit closer to the Sun, and the other three planets moved further away.
All was peaceful in the solar kingdom until the orbits of Saturn and Jupiter aligned so that Saturn took exactly twice as long as its neighbor to go around the Sun. The increased gravitational tug of the two planets acting together caused an avalanche of effects.
Saturn’s orbit changed shape slightly, which threw off the orbits of Uranus and Neptune. The orbits of these two planets started looking like squished ovals. At times, the two planets even crossed paths.
And that’s when things got really crazy. Uranus and Neptune started hurtling through the band of ice, dust, and gas, scattering the debris throughout the Solar System. The planets themselves ended up in their current orbits.
In the meantime, some of the scattered material became trapped around Jupiter, the scientists suggest. This could account for the presence of objects, known as the Trojan asteroids, that both lead and trail the planet.
Some of the debris could have been flung closer to our home, slamming into the Moon and the Solar System’s inner planets. This bombardment may have created the huge craters on the Moon and elsewhere.
No one knows for sure whether all this really happened. But, by using computers to play complex games of “what if,” scientists can get a better sense of what might have happened to create the Solar System as we know it.
Name ______
Gravity Articles II
What keeps satellites from falling out of the sky?
1. Over the last half-century over ______satellites have been launched into Earth orbit. (Enter a number, no comma!)
2. Satellites keep “afloat” through a balance of its…
a. gravityc. gravity and speed.
b. speed.
3. Satellites are basically constantly falling.
a. Trueb. False
4. Satellites in low Earth orbit face drag from…
a. solar wind.c. the Moon’s gravity.
b. the atmosphere.d. the Sun’s gravity.
Plant Gravity
5. This is the environmental signal plants use to determine up and down.
a. Atomic forcec. Gravity
b. Electron forced. Magnetism
6. In the absence of gravity, you would get an aimless germination and it would just wander.
a. Trueb. False
7. Dense starchy bodies inside the plant settle to the ______of each cell.
a. bottomb. top
Chaos Among the Planets
8. According to the article, these four planets were bunched together and nearer to the Sun. (There are four answers to this question.)
a. Earthe. Neptune
b. Jupiterf. Saturn
c. Marsg. Uranus
d. Mercuryh. Venus
9. This force caused the violent rearrangement of our Solar System.
a. Electromagneticc. Strong
b. Gravityd. Weak
10. Ice, dust, and gas were not much of a match for huge planets.
a. Trueb. False
11. This planet’s orbit changed slightly and threw off the orbits of Uranus and Neptune.
a. Saturnc. Jupiter
b. Earthd. Mercury
12. Some of the scattered materials formed this group of asteroids.
a. Apolloc. Roman
b. Centaurd. Trojan
13. Some of the debris was thrown towards Earth. It may have been responsible for craters on the Moon and planets in the inner Solar System.
a. Trueb. False
14. Scientists are positive this happened.
a. Trueb. False
Gravity Articles II – Key I
1. Over the last half-century over ______satellites have been launched into Earth orbit. (Enter a number, no comma!)
2500
2. Satellites keep “afloat” through a balance of its…
a. gravityc. gravity and speed.
b. speed.
c. gravity and speed.
3. Satellites are basically constantly falling.
a. Trueb. False
a. True
4. Satellites in low Earth orbit face drag from…
a. solar wind.c. the Moon’s gravity.
b. the atmosphere.d. the Sun’s gravity.
b. the atmosphere
5. This is the environmental signal plants use to determine up and down.
a. Atomic forcec. Gravity
b. Electron forced. Magnetism
c. Gravity
6. In the absence of gravity, you would get an aimless germination and it would just wander.
a. Trueb. False
a. True
7. Dense starchy bodies inside the plant settle to the ______of each cell.
a. bottomb. top
a. bottom
8. According to the article, these four planets were bunched together and nearer to the Sun. (There are more than two answers to this question.)
b. Jupiter, e. Neptune, f. Saturn, g. Uranus
9. This force caused the violent rearrangement of our Solar System.
b. Gravity
10. Ice, dust, and gas were not much of a match for huge planets.
a. True
11. This planet’s orbit changed slightly and threw off the orbits of Uranus and Neptune.
a. Saturn
12. Some of the scattered materials formed this group of asteroids.
d. Trojan
13. Some of the debris was thrown towards Earth. It may have been responsible for craters on the Moon and planets in the inner Solar System.
a. True
14. Scientists are positive this happened.
b. False
Gravity Articles II – Key II
1. 2500
2. c
3. a (2 choices)
4. b
5. c
6. a (2 choices)
7. a (2 choices)
8. b, e , f, g (8 choices)
9. b
10. a (2 choices)
11. a
12. d
13. a (2 choices)
14. b (2 choices)
Gravity Articles II Worksheet
Scoring Guide
13-14 – 412 – 3.5
11 – 3
10 – 2.5
9 – 2
8 – 1.5
7 – 1
1-6 – .5
0 – 0
~1~