Question

Earth Science Guide for 9th graders:
Gravitational Forces In The Solar System

Answer 1

Gravity holds the solar system together.

Planets, comets, and asteroids move through the sky in odd-shaped but regular orbits. That observation led to some of the most revolutionary ideas in science. In this lesson, you will explore how bodies move in the solar system and the science that explains it.

Answer 2

Planets move through the sky in predictable ways.

Look at the sky every night, and you will notice that the stars move regularly across the sky, but the constellations remain intact. But planets, asteroids, and comets change position. In one night, a planet will move across the sky along with the stars. But over several weeks, the position of the planet will change against the background stars. And sometimes planets move in a "loopy" fashion over time.

Answer 3

For centuries, an earth-centered model explained planetary motions.

The Greek astronomer Ptolemy (Claudius Ptolemaeus) envisioned that the earth was the center of the universe. The sun, stars, moon, and planets all revolved around the earth on circular orbits. To explain the loop path of the planets, Ptolemy put each planet on a smaller circle called an epicycle . The epicycle spun as it moved along its orbit.

The Ptolemaic model, or geocentric model, worked reasonably well at calculating the positions of the planets, but the model was not always accurate and needed constant readjustments. It was, however, the prominent model of the solar system for almost 1,300 years.

Answer 4

Copernicus explained the motions of the planets with a sun-centered model.

In the sixteenth century, Nicolaus Copernicus suggested that the sun, not the earth, was the center of the solar system. In his sun-centered or heliocentric model, the planets revolved around the sun in circular orbits.

Because planets orbit the sun at different speeds, sometimes a planet will overtake another planet as it orbits. When that happens, the slower planet looks as if it moves backward before continuing on its path.

Answer 5

Kepler studied the problem of planetary motion.

Copernicus's heliocentric model gained some support by Galileo's observations of Jupiter and its moons. However, there was little mathematical or observational evidence to advance the heliocentric model over the geocentric model.

Johannes Kepler tried to explain the orbits of the planets in the shapes of nested, regular geometric form but could not get the model to work. Kepler collaborated with Tycho Brahe , who had the most precise observations of the positions and movements of the planets to date. Their relationship was tumultuous over many years. When Tycho died, Kepler convinced Tycho's family to give him the data. Kepler labored over many years to mathematically model Tycho's observations.

Answer 6

Kepler's first law: Using Tycho's data, Kepler worked out the shapes of planetary orbits.

Kepler struggled to make Tycho's observations fit a mathematical model. He tried circular orbits, as Copernicus had suggested, and tried various geometric shapes for the orbits, testing how the predictions of each shape fit Tycho's data. After many years, Kepler hit upon a shape that worked.

The orbits of planets are in the shape of an ellipse with the sun at one focus. This is Kepler's first law of planetary motion.

Answer 7

Kepler's second law: Kepler discovered the speed along planetary orbits.

Kepler also discovered that the speed of a planet's orbit was not constant.

As planets orbit, they sweep out sections of equal areas in equal time intervals. Planets travel faster close in to the sun and slower when farther away. This is Kepler's second law of planetary motion.

Answer 8

Kepler's third law: Kepler found a relationship between orbital distance and orbital period.

Kepler, a mathematician, played with data on the length of time that it takes a planet to orbit the sun and the distance from the sun. He found that the farther a planet is from the sun, the longer it takes to orbit the sun.

It takes Mercury 88 days to orbit the sun. Venus takes 225 days. Earth takes 365 days, or 1 year. Mars needs 687 days. Jupiter takes 4,332 days, or almost 12 earth years. Saturn needs 10,759 days, or over 29 earth years. Uranus needs 30,684 days (84 earth years), and Neptune requires 60,190 days (165 earth years).

Answer 9

The odd motion of planets led to theories of gravity and orbital mechanics.

Early observations showed that planets have odd-shaped motions in the sky, which led to earth- and sun-centered models of the solar system. Over the years, observational data improved and did not support the earth-centered model.

Kepler used observational data to describe the elliptical motions of objects around the sun. Newton used the laws of gravity to explain how planets orbited the sun and to refine Kepler's ideas. Kepler's and Newton's ideas and equations successfully predicted the appearances of comet Halley. Kepler's and Newton's ideas are the basis of orbital mechanics, used by scientists to send interplanetary spacecraft to Mars and beyond.

Answer 10

Kepler's and Newton's ideas about planetary motion are the basis of orbital mechanics.

The models and equations of orbital motions set forth by Kepler and Newton are widely used today. Astronomers use them to calculate the orbits and track newly discovered asteroids and comets. They can also use Newton's version of Kepler's third law to detect and calculate the mass of unseen planets around other stars based on wobble in the star's motion.

Space scientists use these equations to plot transfer orbits for spacecraft between planets. The equations also help in plotting the trajectories of interplanetary probes to the outer planets and beyond, such as Voyager, Galileo, Cassini, and Pluto Express.

Answer 11

Newton explained the motions of the planets by gravity.

While Kepler's model accurately described how planets move in their orbits around the sun, it did not explain what kept the planets in their orbits.

Isaac Newton, an English physicist, demonstrated that the force of the sun's gravity constantly pulled on the planets to keep them in their orbits, much like when you swing a ball attached to a string around your head. The tension of the string, like gravity, holds the ball in the circular path. Newton actually derived all of Kepler's laws of planetary motion from his own laws of motion and gravity.

Answer 12

Others tested Kepler's and Newton's ideas about planetary motion.

Edmund Halley recognized that a comet observed in 1682 had been seen regularly many times before and used Newton's version of Kepler's third law to calculate that the comet orbited the sun every 76 years, and that it would return in 1758. Well, that's just what happened: The comet appeared exactly as he predicted and it now bears his name. All comets have orbital paths that obey the laws of Kepler and Newton.

Answer 13

^this took 13 large sticky notes to write down xD

Answer 14

@563blackghost

Answer 15

NICe JOB PIXEL. Except I knew most of it.

Answer 16

By the law of conservation of matter, when I gain information about random solar system facts, I'll lose a distant memory of my childhood.

Answer 17

Ooo Thank youuu <3