Astronomy

Astronomy- Unit one- the moon Revolution vs. Rotation

revolution- the movent of one object around another object. The moon revolves around the earth and the earth revolves around the sun and the solar system revolves around the center of the galaxy.

Rotation- is the spinning of an object on its axis. (rotation of the earth is ever 24 hours, giving us day and night, the moon rotates on is axis much slower.) Synchronous rotation- the amount of time it takes the moon to rotates is exactly the same as it takes for it to make one revolution around the earth. Which is why we are only able to see one side of the moon from the earth.

Orbit of the moon the moon's orbit is elliptical. not a perfect circle. distance from earth to the moon as small as 356,400 km as large as 406,700 km Best measurements of the distances to the moon have been found measuring the time required for laser signals aimed at the moon to bounce back from reflectors left on the moon during the apollo landings (evidence that they were not faked)

knowing the distance to an accuracy to a few centimeters, plus calculating an angle and one more calculation gives us the diameter (distance from one side to another through the center) of 3476km, which is 27% as large as the earth.

EFFECTS OF THE MOON Tides-distortions in shape due to tidal forces TIDAL FORCES-Differences in gravity that occur in an object being attracted by another.

The points on the earth that are the closest to the moon at any given time experience the strongest gravitational pull by the moon.

Tides and the Earth's ROtation the friction that is a result of the tidal forces between the earth and the moon cause the Earth to spin slower and slower

this is like if you spin a bucycle tire and then place your hand on it to slow it down

the effect from the moon is much less and the slowing is only at a rate that increases the length of our day by about 0.0015 seconds per 100 years.

270 million yrs ago= 384 days per year 440 million years ago= 407 days per year 900 million yrs ago= 481 days per year

this was determined using coral evidence as well as evidence found in sedimentary rocks.

Moon's orbit

the distance from the Earth to the moon is increasin at a current rate of about 3cm each year. at that rate, however, the earth and moon would have been very close 1.6 million years ago. Rate of increase has not always been at 3cm per year. It was slower in the past.

Moon's surface prior to 1609, the best sketches of the moon were by Jan Van Eyck and by Leonardo Da Vinci in 1609- galileo observed the moon through his telescope.

although he understood that the moon probably didn't have large bodies of water, he named the large daed regions maria (sea) and the lighter regions terrae (land) The names of the dark regions were invented in the mid 1600s by giovanni Riccioli who also began the custom of naming the craters after notable scholars.

EXPOLRATION OF THE MOON

Luna 3(1959) passed behind the moon and returned the first images of the far side, showing almost no large maria. 1966- USA and USSR both began series of robotic landers. Luna 9- showed that the surface of the moon was not covered by an extremely thick layer of dust, as some scientiss had predicted. Us surveyor program's mission was to determine whether a managed mission landing was possible, measuring the strength and composition of the lunar soil.

Apollo 11- July 20th 1969 Neil Armstron and Buzz Aldrin made the first manned lunar landing at the sea of tranquility. Apollo12 1969- Pete Conrad and al Beanlanded 600m from the suveyor 3 landing site and were able to retrieve the camera from that mission Appollo 13- Jim lovell, Jack Swigert, and Fred Haise- was called the successful failure mission- despite suffering multiple setbacks and life threatening challenges, crew returned safely without haveing landed on the moon.

Apollo 14- feb, 5 1971 third manne dmission to land on the moon. al sheperd(first american in space) and ed mitchell. Apollo 15- July 26, 1971 longer term mission than prior missions.. Dave scott nd james irwin spent three days on the moon, and 18.5 hours on EVAs(extral vehicular activity); also the first mission to use the rover to explore fartherfrom landing site than before. Apollo 16- April 21, 1972- John Young, Charlie duke landed on the highlands. Apollo 17-dec 11, 1972 final lunar landing, gene Cernan, Harrison Schmitt (geologist who was seleted to replace Joe Engal when it was determined that this mission was to be the last the apollo series

Theories of the Formation of the moon Sister/coformation theory Early theory that the moon formed at the same time as the earth, and formed a double planet system revolving around a common center of mas. Problem with this threory, our moon differs in density and composition tfrom the earth.

Capture theory- the moon formed far from the Earth, but was somehow captured by the Earth's gravitational pull. the theory solved the different compostion problm, but left a new one. Problem with this teory- the moon is such a large satellite compared to the Erth that the mathematical equations dealing with gravitational pull do not work for the earth capturing something as massive as the moon.

Daughter/fission theory- this older theory states that the earth in its moten state of formation ejected enough material to form the moon. Problem: the math doesn't work for the earth to be spinning fast enough for this to happen, and even if it could, the ejected material probably wouldn't have ended up in a stable orbit.

Impact Theory: most astromomers favor this theory- the theoary is that a mars sized body/object collided with a young, molten earth. THe modelling suggests that the impact was not a direct one, but rather a glancing blow. The Matter that was dislodged from the hit, reassembled to form the moon. Took place about 4.6 billion years ago.