unit 2 | tides & distances

tides

{{tides vocab{{

• $apogee$ → point of an orbit that is further away from focal point
• $perigee$ → point of an orbit that is closer to focal point

{{spring tide{{

• occurs during the full & new moon
• the combined gravity of the sun & moon produces a stronger tide   * higher high tide & lower low tides
• has nothing to do with the season
• occurs twice each lunar month
• moon is aligned with sun

{{neap tide{{

• occurs during the waxing & waning half-moons
• the detracting gravity of the sun and moon produces a weaker tide   * lower high tides & higher low tides

{{diurnal tide{{

• 1 episode of high water and 1 episode of low water each day
• occur in locations when the moon is farthest from the equator

{{semi-diurnal tide{{

• 2 episodes of equal high water and 2 episodes of low water each day
• the second high tide rises to the same level it did in the 1st high tide
• the second low tide also matches with the 1st low tide
• occurs when the moon is directly over the equator
• most common type of tidal pattern

{{mixed tide{{

• can have two episodes of high or low water per day   * two high or low tides are unequal
• can either include both sets of unequal high or low waters or only one set of unequal high or low water
• occurs when the moon is extremely far north or extremely far south of the equator

\

\

{{meteorological tides{{

• tides affected by wind, barometric pressures, rainfall, ice melting, & land drying
• example:   * storm surges: the wind & inverted barometric pressure combine to cause a dramatic increase in sea levels

space measurement

<<doppler effect<<

• the apparent change in the frequency of a wave
• with light it’s also called “red shift, blue shift”
• when a star or other luminescent object is moving away from our position then it appears to give off more red light
• when a star or other luminescent object moves closer it appears to give off more blue light

<<cosmological red shifts<<

• the wavelength at which the radiation is originally emitted is lengthened as it travels through (expanded) space
• cosmological red shift results from the expansion of space itself and not from the motion of an individual body

<<astronomical units<<

• major unit used to measure space (AU)
• made from measuring the mean distance from the center of the Earth to the center of the Sun   * 93,000,000 mi

<<light years<<

• how long is a light-year in Earth years?   * 5,878,625,370,000 mi (9.5 trillion km)

<<parallax<<

• the apparent displacement or the difference in apparent direction of an object as seen from two different points not on a straight line with the object especially

OR

• the angular difference in direction of a celestial body as measured from two points on Earth’s orbit

<<parsecs<<

• a unit of distance used in astronomy, equal to about 3.26 light years (3.086 x 10^13 km)
• one parsec corresponds to the distance at which the mean radius of the Earth’s orbit subtends an angle of one second of arc