What is gravity? - NASA Newton's "law" of gravity is a mathematical description of the way bodies are observed to attract one another, based on many scientific experiments and observations The gravitational equation says that the force of gravity is proportional to the product of the two masses (m 1 and m 2), and inversely proportional to the square of the distance (r) between their centers of mass Mathematically
StarChild: Glossary - NASA GRAVITATIONAL FORCE See Gravity GRAVITATIONAL PULL See Gravity GRAVITY The force of attraction between two objects which is influenced by the mass of the two objects and the distance between the two objects GYROSCOPE A heavy wheel or disk mounted so that its axis can turn freely in one or more directions
Teachers Center Activity: Gravity Effects on Planet Motion - NASA 1 Introduction: Review the definition of gravity Drop a ball and explain why it falls downward Explain that the strength of a gravitational pull is determined by the masses of the objects involved and the distance between the objects Hold up a scale model of Earth and a scale model of the Sun Inquire as to which object would exert a stronger pull
How do we know that dark matter exists? - NASA The cluster does not behave as scientists would expect it to if only the visible matter is generating the gravity present in the cluster 'Dark matter' theory suggests that a huge amount of dark (invisible to direct observation) matter, interacting gravitationally with the normal, visible matter in the universe, exists
StarChild: Glossary - NASA GRAVITY The invisible force between objects that makes objects attract each other GRAVITATIONAL PULL The attraction that one object has for another object due to the invisible force of gravity H HURRICANE A very, very strong windstorm where the wind blows in circles at more than 46 kilometers per hour Heavy rains often come with the winds I
StarChild: The Asteroid Belt - NASA An asteroid is a rocky body in space which may be only a few hundred feet wide or it may be several hundred miles wide They are considered to be debris left over from the formation of the solar system Many asteroids orbit the Sun in a region between Mars and Jupiter This "belt" of asteroids follows a slightly elliptical path as it orbits the Sun in the same direction as the planets It
Where did the Moon come from? - NASA The Moon's low density (3 3 g cc) shows that it does not have a substantial iron core like the Earth does Moon rocks contain few volatile substances (e g water), which implies extra baking of the lunar surface relative to that of Earth The relative abundance of oxygen isotopes on Earth and on the Moon are identical, which suggests that the Earth and Moon formed at the same distance from the
What is the shape of the universe? - NASA The geometry of the universe is often expressed in terms of the "density parameter", which is defined as the ratio of the actual density of the universe to the critical density that would be required to cause the expansion to stop Thus, if the universe is flat (contains just the amount of mass to close it) the density parameter is exactly 1, if the universe is open with negative curvature the
What is a light-year and how is it used?? - NASA A light-year is a unit of distance It is the distance that light can travel in one year Light moves at a velocity of about 300,000 kilometers (km) each second So in one year, it can travel about 10 trillion km More p recisely, one light-year is equal to 9,500,000,000,000 kilometers
StarChild: Black Holes - NASA Black holes are extremely compact space objects that were once massive stars which collapsed inward due to the force of their own gravity Consequently, black holes are very dense If it were not for the effect that black holes have on the objects around them, we would be unable to detect them A black hole has a powerful gravitational field which traps everything that goes near it Scientists