Space motion

Earth-Centred Universe In ancient times many people though that the Earth was the centre of the Universe and that all other objects revolved around it.

Sun-Centred Solar System 500 years ago people began to question the idea of the Earth- Centred Universe. Around 1550, Copernicus showed mathematically that the planets all orbited around the Sun.

2 Solar System Models Geocentric – 2000 years ago Earth is the centre of the universe Heliocentric – present model Sun is the centre of the solar system

Why Do we have sunsets?

A rotation is 1 spin on Earth’s axis 1 spin = 1 day Earth’s rotation The motion of the sun in the sky is caused by the rotation of Earth on its axis A rotation is 1 spin on Earth’s axis 1 spin = 1 day

Revolution is the movement of one object around another It takes Earth one year to revolve around the Sun along its orbit

Why does the earth have seasons? A. Earth’s orbit is further away from the sun during the winter and closer in the summer B. The tilt of Earth’s Axis causes the seasons C. The tidal changes in the ocean as a result of the moons revolution causes the seasons

The reason for the seasons The Earth is tilted on it’s axis 23.5° Earth tilted toward the sun = summer Tilted away from the sun = winter

Seasons

Northern Hemisphere Summer At this point, we have participants use styrofoam balls with sticks and a bright lamp to model the seasons on the Earth, with the axis of the “Earth” tilted toward a “North Star” that has been placed high in the corner of the room. For part of our orbit the northern half of Earth is tilted toward the Sun. This is summer in the northern hemisphere; there are longer periods of daylight, the Sun is higher in the sky, and the Sun's rays strike the surface more directly, giving us warmer temperatures. The north pole is in constant daylight! When the northern half of Earth is tilted toward the Sun, the southern hemisphere is tilted away. People in the southern hemisphere experience the shorter day lengths and colder temperatures of winter. During winter in the northern hemisphere, our northern axis continues to point to the North Star, but, because we have moved in our orbit around the Sun, our northern hemisphere now points away from our Sun. The north pole is completely dark and other places in the northern hemisphere experience the shorter day lengths and colder temperatures of winter as the Sun traces a lower arc across the southern sky and the Sun's rays strike the surface at a lower angle. When it is winter in the northern half of Earth, the southern hemisphere, tilted toward our Sun, has summer. During fall and spring, some locations on Earth experience similar, milder, conditions. Earth has moved to a position in its orbit where its axis is more or less perpendicular to the incoming rays of the Sun. The durations of daylight and darkness are more equally distributed across all latitudes of the globe. Solstices occur when Earth's axis is pointed directly toward our Sun. This happens twice a year during Earth's orbit. Near June 21 the north pole is tilted 23.5 degrees toward our Sun and the northern hemisphere experiences summer solstice, the longest day of the northern hemisphere year. On that same day, the southern hemisphere is tilted 23.5 degrees away from our Sun and the southern regions of Earth experience the shortest day of the year — the winter solstice. The second solstice occurs on December 21 or 22 when the north pole is tilting 23.5 degrees away from our Sun and the south pole is inclined toward it. This is the shortest day of the year in the northern hemisphere — the northern hemisphere winter solstice. Twice each year, during the equinoxes (“equal nights”), Earth's axis is not pointed toward our Sun, but is perpendicular to the incoming rays. During the equinoxes every location on our Earth (except the extreme poles) experiences 12 hours of daylight and 12 hours of darkness. The vernal or spring equinox occurs in the northern hemisphere on March 21 or 22 (the fall equinox of the southern hemisphere). September 22 or 23 marks the northern hemisphere autumnal or fall equinox. As Earth orbits our Sun, the position of its axis relative to the Sun changes. This results in a change in the observed height of our Sun above the horizon. For any given location on Earth, our Sun is observed to trace a higher path above the horizon in the summer, and a lower path in the winter. During spring and fall, it traces an intermediate path. This means that our Sun takes a greater amount of time tocross the sky in the summer and a shorter amount of time in the winter. This effect is greater as you move toward the poles; people living near the equator experience only small changes in daylight during the year. The change is more extreme toward the poles. From the National Maritime Museum During the northern hemisphere summer solstice, Earth is tilted such that the Sun's rays strike perpendicular to the surface at the Tropic of Cancer (23.5 degrees north latitude, corresponding to the tilt of Earth's axis). At (solar) noon, our Sun is directly overhead in this location (and at a decreasing height above the horizon north and south of the Tropic of Cancer). At locations north, our Sun will be at its highest position above the horizon and will take the greatest amount of time to cross the sky. All northern locations have more than 12 hours of daylight. All locations south experience less than 12 hours of daylight. Locations above the Arctic Circle (north of 66.5 degrees latitude; 90 degrees minus the tilt of Earth's axis) receive 24 hours of sunlight. Locations below the Antarctic Circle (66.5 degrees south latitude) experience 24 hours of darkness. During the northern hemisphere winter solstice, the Sun's incoming rays are perpendicular to the Tropic of Capricorn at 23.5 degrees south latitude. The Sun's path is the lowest above the horizon in locations north of the equator, and these regions experience the shortest day of the year. Between the winter and summer solstices, daylight increases as Earth continues its orbit around our Sun. During the equinoxes, sunlight strikes perpendicular to the surface at Earth's equator. All locations on Earth, regardless of latitude, experience 12 hours of daylight and 12 hours of darkness. The spring equinox marks the change from 24 hours of darkness to 24 hours of daylight at Earth's poles . In these extreme locations, our Sun moves above the horizon at the spring equinox and does not go below the horizon until the fall equinox. More daylight hours, more direct sunlight https://www.youtube.com/watch?v=KUU7IyfR34o&list=PLW-qGSm739tksDYzzY6rmi3OTBRdWpVX3&index=3

Time Zones – not all areas experience day and night at the same time

Motions of the moon rotates on a axis The moon also revolves around the earth The moon rotates on its axis in about the time it takes to revolve around the earth Therefore we always see the same side of the moon

Together the earth and moon orbit around the sun Moon’s Motion Together the earth and moon orbit around the sun

Phases of the Moon

The same side of the Moon is always facing Earth. Phases of the Moon The same side of the Moon is always facing Earth.

The Moon rotates around it’s axis once every 29.5 days. Phases of the Moon The Moon rotates around it’s axis once every 29.5 days. Moon Phases: Crash Course Astro #4 https://www.youtube.com/watch?v=A Q5vty8f9Xc National Geographic http://video.nationalgeographic.com/vid eo/101-videos/moon-101-sci

The Moon revolves around the Earth once every 29.5 days. Phases of the Moon The Moon revolves around the Earth once every 29.5 days.

Interesting Facts… When there are two Full Moons in a month the second one is called a "Blue Moon".

Due to the pull of gravity by the moon 3. Tides Due to the pull of gravity by the moon https://www.youtube.com/watch?v=KlWpFLfLFBI

Apparent Motion of Celestial objects the stars appear to move across the sky from east to west However, the apparent motion is caused by Earth’s rotation