Tides & Eclipses By: Kiah Bransch, Iva Rreza, Ashley Pantona-Price, and Gabby Jones

Universal forces Albert Einstein, the renowned physicist and philosopher, summed up the universe forces into four main forces known as electromagnetic, gravitational, and the weak and strong forces within an atom. While gravity and electromagnetic are infinite, the forces within an atom are finite. Electromagnetism is a force that occurs wherever magnetic and electric field occur. The elementary particles of the universe are known as quarks where the weak forces cause radiation and the strong forces bind matter together. Gravity is also an infinite force and a centripetal force that happens when an object is massive enough. When this is true an object constantly attracts objects towards it.

Days, Years, and Seasons While the earth is constantly kept into orbit through gravity, the earth experiences temperature changes as it rotates and revolves. Since the earth is somewhat of a sphere, it receives different amounts of light throughout. (more at equator than at poles) The constant revolution causes earth to have period of light and no light which occurs every 23 hours and 56 minutes. Since earth’s orbit is not a perfect circle earth’s temperature changes due to distance. Seasons are caused by the tilt of the earth’ s axis (23.5º) as it orbits the sun. The measure of one year is equal to the time it takes the earth to make one full revolution. Since the distance from the sun changes, earth’s speed changes, speeding when near the sun, and slowing down when farther.

Solar Eclipses The first is called a solar eclipse, and it is caused by the moon’s shadow falling on the earth. This occurs only when the moon is directly in front of the earth. The amount of light that is blocked by the moon’s shadow differs because the moon is significantly smaller than the earth. The umbra is the portion of the shadow where most light is blocked and produces a total solar eclipse. The portion of the earth that is covered by the penumbra, or the portion of the shadow that blocks only a part of the sun’s light, experiences a partial solar eclipse.

Lunar Eclipses The second kind of eclipse is a lunar eclipse. This is when the earth’s shadow falls on the moon. This kind of eclipse can only be seen during a full moon. During this time the moon is moving at 1 km per second. Lunar eclipses are observed more often than solar because the earth is significantly bigger than the moon so the moon is always covered by earth’s umbra. Even though the moon is tilted 5º in relation to the alignment of the sun, moon, and earth, it eventually passes directly behind the earth. Lunar eclipses can be observed by the naked eye.

Tides Earth’s oceans go through constant flux in phenomenon known as tides. Caused by the pull of the moon’s gravity on earth’s oceans. Earth’s oceans are balanced by centrifugal force which counteracts centripetal force of earth’s gravity. The place nearest the moon always has the highest tide and since the earth is constantly spinning, there is a high tide on the opposite side too. The positions in between experiences low tides. Tides constantly vary from time to time and position to position.

Spring Tides Tides occur in different positions and alignments. Spring tides occur when the moon, earth, and sun are aligned. As the moon orbits around the earth, the oceans bulge outward. The greatest difference between high and low tide is known as a spring tide. Spring tides can only occur during full and new moon. The position that is closest to the moon and the one opposite to it experiences the highest tide and the same is for lowest tide.

Neap Tides When the position of the moon in relation to the earth and sun is at a 90º angle, a neap tide, occurs. This occurs when the sun, earth, and moon are not aligned and the gravitational forces cancel each other out. This tide is also known as the smallest difference between high and low tide. Neap tides occur twice in a month during the first and last quarter.

Moon phases The infinite force that keeps the earth orbiting around the sun also keeps the moon orbiting the earth. Since the moon is an illuminated object, the portion that is “lighted up” always changes. Orbiting and rotational period: 27.3 earth days. Moon phases in chronological order: New moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, waning crescent, and then back to a new moon.