Super Science Review Earth and Space Science 28-42

28. Gravity is the force that pulls all objects down. If you throw a ball up, gravity pulls it back down. Larger objects have more gravity, so the Sun has the most, Earth has less, and the moon has the least gravity.

29. The Sun is a star, meaning it is a giant ball of hot gases. It is the largest object in our solar system. It is extremely hot. Cooler and darker spots on the Sun are known as sunspots. All of the planets travel around the Sun because its gravity pulls them.

30. The Sun is the source of energy for all life on Earth. The Sun’s energy also gives us weather, as well as providing the heat energy that causes evaporation, the start of the water cycle.

31. There are 8 planets (in our Solar System). They are, in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. The first four are smaller and made of rock. The last four are larger and made of gas.

32. An orbit, also called a revolution, is the path that an object takes around another object. It takes 365 days for the Earth to orbit the Sun. It takes the moon about 28 days, or one month, to revolve around the Earth. (Hint: revolution…4 syllables…4 seasons…1 year. Orbit –O is round because Earth moves around the Sun in orbit.)

33. A rotation is when an object spins around on it axis (center). It takes the Earth 24 hours, or one day to complete one rotation. (Hint: Rotation-RoDAYtion))

34. Complete this chart to compare the Earth and the Moon: EARTHMOON Has an atmosphere Has Liquid Water Has more gravity Has less craters Has no atmosphere No water (liquid) Has Less Gravity Has More Craters

35. Weathering is the breaking down of large rocks into smaller rocks. Weathering occurs over millions of years. The Grand Canyon was formed by physical weathering and erosion caused by the Colorado River. Physical weathering includes water, air, and temperature. Caves and stalactites/stalagmites are caused by chemical weathering. Chemicals break down rock by dissolving it.

36. Erosion is the carrying away of rocks and sediment. Moving water, such as flowing rivers, is the main agent of erosion. Air can also erode smaller pieces of rock, such as sand blowing in the desert.

37. Deposition is the depositing of sediment over a period of time. Deltas are formed when rivers slow down and deposit sediment, forming a large fan-shaped pile. When desert winds slow down, sand is deposited and sand dunes are formed.

38. Soil is made up of tiny pieces of rock, humus, water and air. It forms slowly through weathering. The layers of soil are topsoil, subsoil, lowest layer and bedrock. Plants grow best in the topsoil layer. Sand grains are the largest, silt grains are medium, and clay grains are the smallest.

39. The Earth is always changing. Changes like glaciers carving out the land are slow changes or changes like earthquakes and landslides are fast changes.

40. We can the age of things by looking at rock layers. By examining fossils (the remains of dead organisms), we can tell the age of rock layers. The layers on top are the youngest and the layers on the bottom are the oldest.

41. Renewable resources can be replaced within our lifetime. Trees, oxygen and animals are examples of renewable resources. Nonrenewable resources cannot be replaced in our lifetime. Coal, oil (also known as petroleum), and natural gas are examples of nonrenewable resources. They are called fossil fuels, which are formed from the remains of prehistoric plants and animals over millions of years. Oil and natural gas were formed in prehistoric seas. Coal was formed in prehistoric swamps.

42. Burning a lot of fossil fuels puts too much carbon dioxide into the atmosphere, causing global warming. We can prevent this by practicing the “3 R’s”: reduce, reuse, recycle. When we recycle things like aluminum cans, they can be melted and remade into new products. We can reuse products such as cloth diapers, which can be washed and reused again. We can reduce energy by turning off lights when we’re not in the room, or by opening a window instead of using an air conditioner. We call all of this conservation.