SCIM1040 Lecture Notes - Lecture 1: Plutoid, Regolith, Ripple Marks
5 Jun 2018
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SCIM1040- Lecture 1.
• The Solar System formed about 4.6 billion years ago.
• A solar system starts out as a huge cloud of dust and gas (about 10 000 times
larger than the distance from Earth to the Sun).
• The cloud collapses under gravity, begins to spin and forms a flat, rotating disk
in which the star is formed. The planets form by bits of the cloud sticking
together.
• The major parts are our star, the Sun, and planets held gravitationally in orbit
around our star.
• It takes our Solar System about 240 million years to do one galactic orbit,
about18 completed to date.
• In ancient times, most knowledge about the stars, planets, and comets was
• based on what was simply observed and common-sense attitudes. As a result
of
• improving technology, information about our Solar System has been growing
• very rapidly.
Aristotle (384BC - 322 BC), a highly respected Greek philosopher and scientist, based
his geocentric model on the common sense observation that the Sun, Moon, and planets
seemed to move around the Earth. He believed Earth to be the rotational centre of the
universe which was widely accepted without question by the Church and the people
until the 16th century.
Claudius Ptolemy (90AD–168AD), a Greek-Egyptian astronomer, also described an
Earth-centred model of the universe due to the need to obey the Church’s teachings.
Ptolemy argued that the Sun orbited the Earth which was located in the centre of the
universe from the observation that half the stars were above the horizon and half were
below the horizon at any time.
Tycho Brahe (1546 – 1601) was a Danish astronomer who made accurate astronomical
tools for his night sky observations. He did not support Copernicus’s heliocentric theory
but, at the same time, did not completely agree with Ptolemy that the Earth was orbited
by the Sun and the other planets. So, he combined both the geocentric and heliocentric
models (geoheliocentric?) because it allowed astronomers to stay on the right side of the
Catholic Church while moving away from the established geocentric theory. He
described the Sun orbiting the Earth at the same time as all other planets moved around
the Sun.
Copernicus (1473-1543), a Polish astronomer, believed that the Earth as well as the
other planets revolved around the Sun. Copernicus’ Sun-centred model was only
published on his death for fear of criticism from the Church.
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Galileo Galilei (1564 - 1642), an Italian astronomer, was an outspoken supporter of the
Copernican theory. Also, in 1609, he was the first to use a telescope and found that the
heavens were not at all perfect like the Ancients had said. The Sun had spots, the Moon
had mountains, Venus showed phases, and Jupiter had moons (this observation was
very controversial as it proved that the Earth was NOT the ONLY centre of movement
in the universe).
Johannes Kepler (1571 - 1630), a German astronomer, studied motion of planets in
detail and improved the heliocentric model. He discovered from Tycho Brahe’s
observations that Mars’ path around the Sun was not circular but elliptical. The planet
moved faster when it was closer to the Sun and slowed down when it was further away.
Sir Isaac Newton (1643 - 1727), an English scientist, is famous for proposing that
gravity was responsible for the movement of planets and comets around the Sun and
that gravity is a force that holds the universe together. He also formulated the three
laws of motion (laws of inertia, acceleration proportional to force, action and reaction)
which dominate the physical universe.
• Average size star that appears yellow when viewed from Earth but is white when
viewed from space.
• Is a rotating sphere of hot glowing gases, mainly hydrogen and helium.
• Has about another 5 billion years before it will collapse into a white dwarf star
after using up all its hydrogen and helium.
• The Sun is approximately 333 000 times more massive than Earth but over a
million Earths could fit inside the Sun.
• Contains more than 99% of the mass of the entire Solar System.
• Surface temperature is approx. 6000oC with the core being about
15 000 000oC.
The surrounding corona (extended outer atmosphere of the Sun) mysteriously rises in
temperature to million of degrees. It may be being heated by powerful X-ray jets being
sprayed from the Sun’s surface hundreds of times a day launching hot gas into the
corona at speeds of 3 million km/hr.
Mercury:
• No moons
• Day = 59 Earth days
• Year = 88 Earth days
• Usually obscured by the Sun’s glare
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• Extreme temperature ranges from 427oC to -173oC (The metal lead would melt on
the hot surface - 7 times hotter than Earth’s hottest desert; 8 times colder than the
kitchen freezer)
• Heavily cratered
• No atmosphere: a very weak exosphere of some gases with a pressure less than
one trillionth of Earth’s atmospheric pressure.
• Fastest moving planet
Venus
• Closest planet to Earth
• Known as the Morning Star and the Evening Star
• No moons
• Day = 243 Earth days
• Year = 224.7 Earth days (its day is longer than its year)
• Hottest planet = can reach 480oC (approx twice as hot as the kitchen oven on full)
• Permanently shrouded in clouds preventing direct observation; only cloud-
penetrating radar from an orbiting space probe has been able to map the surface
.
• Atmosphere consists mainly of carbon dioxide and sulfuric acid (acid in the
atmosphere is as strong as the battery acid in the car); acts like a blanket
creating a perfect greenhouse effect.
• Air pressure is nearly 90 times greater than Earth’s atmosphere (its atmospheric
pressure could crush a deep-sea submarine)
• Spins on its axis in the opposite direction to other planets, possibly caused by a
collision with another large planet early in its history.
Earth
• Is about 150 million kilometres away from the Sun. We call this distance 1AU or
one Astronomical Unit, a very small unit of distance when measuring distances
in the universe.
• Has a magnetic field that acts like a giant bar magnet.
• Only planet to have liquid water over its surface.
• Crust is broken into slow moving sections called plates that cause volcanoes,
earthquakes and mountain building as they interfere with each other.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The planets form by bits of the cloud sticking together: the major parts are our star, the sun, and planets held gravitationally in orbit around our star. It takes our solar system about 240 million years to do one galactic orbit, about18 completed to date. In ancient times, most knowledge about the stars, planets, and comets was based on what was simply observed and common-sense attitudes. As a result of improving technology, information about our solar system has been growing very rapidly. Aristotle (384bc - 322 bc), a highly respected greek philosopher and scientist, based his geocentric model on the common sense observation that the sun, moon, and planets seemed to move around the earth. He believed earth to be the rotational centre of the universe which was widely accepted without question by the church and the people until the 16th century. Claudius ptolemy (90ad 168ad), a greek-egyptian astronomer, also described an.
