AS101 Module 2

Astronomy is the ______ of the sciences!

oldest!

What is the best-known device that ancient peoples used to keep track of time? (Hint: It's in the south of England)

Stonehenge!

Who built the Stonehenge?

Largely debatable; could be by the people of the late Neolithic Period (3000 BC), or Beaker Folk, or Indigenous peoples

Who built Templo Mayor?

Aztec Empire

Best known construction on the Chichén Itzá site in Mexico? (The Mayans)

Kukulcan's Pyramid

What is the "much simpler Stonehenge" of rocks strategically placed on the ground to form a giant wheel with spokes?

Big Horn Medicine Wheel (Wyoming, USA)

What did most ancient civilizations pay close attention to in astronomics?

29.5 lunar day cycle

What do we refer to "lunar cycling" as nowadays?

Metonic cycle (after Mike Meton, 432 BC)

Why does the date of Easter vary annually?

Easter Sunday is always the Sunday following the first full moon, after the spring equinox!

The Saros Cycle is associated with...

the cycle of eclipses

Where did modern science first begin developing?

Middle East (Mesopotamia, Egypt, Greece) - Modern-day Iran and Iraq

Thales of Miletus (624-547 BC) promoted what for astronomy?...

The notion that the universe was rational and therefore understandable

(It wasn't a mystery beyond human comprehension, like previous cultures in Egypt believed)

Pythagoras (570-500 BC) believed...

that planets produce music as they travel in their orbits (concept of "music of the spheres")

Socrates (470-399 BC) was...

more a philosopher than a scientist; however his ideology was that virtue is understanding and that no human being knowingly does wrong

(but he would prove others wrong with lines of questioning to find contractions - like Ace Attorney fr)

Plato (428-348 BC) took little interest in science, although he valued mathematics, and was most known for his ideas on love, hence began the term:

platonic love!

Plato (428-347 BC) also wrote the Republic, which...?

formulated his ideas of the perfect state

Aristotle (384-322 BC) believed that knowledge was...

fundamentally empirical!

(Observation rather than theory or pure logic)

Aristotle (384-322 BC) believed that the universe existed in two parts:

Earth (corrupt and changeable) and the heavens (perfect and immutable)

Aristotle (384-322 BC) also believed that the Earth was...

at the centre of the universe

Aristotle (384-322 BC) developed a sequence of reasoning which involved gaining all knowledge that he could on a topic & testing it thoroughly. This is now the basis of all Western scientific thinking, which is called:

The Scientific Method

Claudius Ptolemy (90-168 AD) developed a model of the universe, which......

was based on his observations and those of his forefathers, and which predicted planetary events of the future quite well

(and which was studied by astronomers)

Claudius Ptolemy (90-168 AD) created a mathematical model of the Aristotelian universe in which...

the planet followed a small circle called the epicycle which slid around a larger circle called the deferent

(by adjusting the size and rate of rotation of these circles, he was able to figure out retrograde motions of a planet)

Other than it being the centre of the universe, Claudius Ptolemy (90-168 AD) deduced that the Earth was

slightly off center

The center of the epicycle moved such that it appeared to move at a constant rate as seen from the point called the...

equant

One of Claudius Ptolemy's critical flaws in his model of the universe was...

the earth being the centre of the universe

By adjusting the size and rate of specific circles, Claudius Ptolemy was able to determine retrograde motions of planets. What were these circles called?

The epicycle (small) and the deferent (large)

Nicolaus Copernicus (1473-1543) published a book titled...

De Revolutionibus Orbium Caelestium in 1543

(Concerning the Revolutions of the Heavenly Spheres), in which he claimed that the true and accurate model of the solar system could only be that of a Sun-centred system.

Nicolaus Copernicus (1473-1543) believed that the sun was...

in the centre of the universe! (which was correct!)

However, Nicolaus Copernicus (1473-1543) still held the belief that the orbits of the planets had to be...

circular! (not eclipses as we know now)

Tycho Brahe (1546-1601), when he was young, observed that the expected conjunction of Jupiter and saturn was late by...

two days! (based on Copernicus' model)

After this, he decided to start compiling his own set of observations

Tycho Brahe was eventually sponsored by King Frederick II (Denmark), and he was able to...

set up his own spectacular observatory, on his own island of Hven in the Baltic Sea, where he did his work!

(but it was much to no avail - he failed to come up with any better models of planetary motion)

Johannes Kepler (1571-1630) established what?

three laws dedicated to orbits of planets (though Kepler's Third Law was more about the ratio of planets)

Kepler's First Law:

The orbit of each planet around the Sun is an ellipse with the Sun at one focus (The Law of Orbits)

Kepler's Second Law:

As a planet moves around in its orbit, it sweeps out equal areas in equal times (The Law of Areas)

Kepler's Third Law:

The squares of the periods of any two planets have the same ratio as the cubes of their semi-major axes (The Law of Periods)

Works as an equation of: p2 = a3

We can only write Kepler's Third Law, p2 = a3, only when "a" is expressed in...

AU! (astronomical units)

We can only write Kepler's Third Law, p2 = a3, only when "p" is expressed in..

Years!

Galileo invented the...

telescope!

(and for astronomical purposes this time - Hans Lippershey actually invented the telescope but only as a toy)

Gelileo's observation of Venus confirmed that solar system was...

Sun-centred!

Galileo died on January 8, 1642, having failed to convince the ignorant leaders of...

the Roman Catholic Church that its interpretation of the Holy Scriptures was inconsistent with observed facts

(sounds a lot like fire force fr...)

The Church pronounced Galileo's findings false and heretical, and...

forbade anyone to teach them, and put Galileo under a form of "house arrest" (mfs scared of facts fr)

Isaac Newton (1632) introduced the idea of...

universal gravity! (Law of Gravitation)

We can determine the mass of a star of planet by...

finding something in orbit around it

(We determine the Earth's mass by observing the Moon. We determine Jupiter's mass by observing any of its moons)

Which side of the Earth feels a stronger (bigger) gravitational attraction?

The side of the Earth facing the Moon!

At the time of a new and/or full Moon (when the Sun, Moon, and Earth are all lined up), the tides are highest and are called...

spring tides!

(has nothing to do with the spring season; it is because the water “springs” up the shore)

During the first and third quarter Moons, the tides are called...

Neap tides!

(because the Sun, now perpendicular to the line between the Earth and the Moon, tends to cancel out the effect of the lunar tides -- resulting in lower tides than at other times)

What happens as a result of tidal friction?

The rotation of the Earth gradually slows down (the days are getting slightly longer) and the Moon is moves further from the Earth

Deductive reasoning is...

logically valid and it is the fundamental method in which mathematical facts are shown to be true

Inductive reasoning is...

the process of reasoning that a general principle is true because the special cases you've seen are true

(constructing a general principle from special cases - asserting something based on prior experience, essentially)

(Ex. if all the people you've ever met from a particular town have been very strange, you might then say "all the residents of this town are strange".)

The Scientific Method:

one looks at a set of observations or demonstrated facts, develops a hypothesis that satisfies or predicts accurately the observations, makes further observations, tests the hypothesis and makes adjustments as necessary!

- Ask Question > Do background research > construct hypothesis > test with an experiment > analyze results & draw conclusion > if hypothesis is true, report results > if hypothesis is false or partially true, think and try again from constructing the hypothesis!

Pseudoscience, or false science, is...

Lots of people make predictions based on reading tea leaves, tarot cards, palms, psychic determinations. Such so-called scientific prognostications have never met the "test of time" using the accepted scientific method (such as astrology)

- essentially something that is believed but cannot be scientifically proven

Nonscience (notice how close this word is to “nonsense”) is a term used to describe...

predictions based on intuition, societal traditions (old wives' tales), faith, political conviction, and tradition.

However, such non-science techniques also do not meet the "test of time" and when made subject to the scientific method, simply fall apart.

At the heart of modern astronomy is something called the Cosmological Principle. This principle is based on two fundamental tenets:

One:

There is nothing special or unique about Earth — the Earth is not at the centre of the Universe or even our own solar system (of course, we now know that) — our location in the Universe is where it is by chance, nothing more, nothing less — nor is our galaxy anything special or different; there are thousands of galaxies like ours and unlike ours

Two:

The second is that the laws of physics and chemistry that describe what happens on Earth are valid throughout the Universe — in a sense, this follows from the first tenet — we are nothing special (astronomically speaking)

Early Greek philosophers who influenced the development of scientific thought included...

Aristotle, Socrates, Plato, Ptolemy

Nicolaus Copernicus was important because...

although he didn't come up with the concept of the heliocentric model, he was convinced that it was the correct model and wrote about it in a published book!

The Copernican Revolution resolved the problem of...

the place of Earth within the solar system!

The problem of planetary motion was only partly solved by...

Kepler's laws

Although we are used to thinking of speeds in km/hour, in science, we usually use..

Standard International (SI) units as metres/second

What is velocity?

Velocity specifies both speed and direction of travel of an object

(velocity can change if: (i) The speed changes (ii) The direction changes (iii) Both speed and direction change)

Velocity also changes if there is a change of direction; so turning is also an example of acceleration. Thus, an object can be traveling in a circle, let’s say, at constant speed but its direction is constantly changing and this translates into a change in velocity.

Speed is...

the rate at which an object moves (changes position).

It is the total distance moved divided by the total time taken to move that distance

Acceleration is...

the rate of change of velocity with time!

It is thus the change in velocity divided by the time taken for the change to occur

Newton’s first law of motion states that... (in terms of velocity and force)

an object remains at rest or at constant velocity unless a net force acts to change its speed or direction

(Ex. When your car is at rest or traveling at a constant speed and direction, then the forces exerted by the wheels to drive you forward is balanced by the wind resistance and other forces in such a way that the net (total) force is zero. If you wanted to speed up, or slow down or change direction, then the engine would have to cause an additional force)

All falling objects on Earth have a constant acceleration downwards towards...

the centre of the Earth (this acceleration was first pointed out by Galileo)

The acceleration of gravity, g, is...

9.8 metres per second per second (more commonly written as 9.8 m/s2)

Newton’s third law of motion states that... (in terms of force)

for every action (force) there is an equal and opposite reaction (force), although the action and reaction forces act on different bodies

(Ex. In terms of the Earth-Moon system this means that the Earth's gravity pulls on the Moon and that's what keeps the Moon in orbit around the Earth. However, at the same time the Moon is pulling on the Earth and these two forces have exactly the same values although, as you can easily comprehend, they do act on different bodies, one on the Moon and the other one on the Earth.)

Second Law of Motion:

Acceleration of an object depends upon its mass, and the magnitude of force applied to it

(F = ma) - Force = mass x acceleration

First Law of Motion (Law of Inertia)

Objects will remain at rest, or in a uniform motion in a straight line, unless acted upon by an unbalanced force

Third Law of Motion:

For every action there is an equal and opposite reaction

(direct example is rocket engine)

Newtonian gravitation is sometimes called...

universal mutual gravitation

In science, mass is not the same as...

weight!

What is mass?

Mass is an intrinsic property of an object and is the same no matter what forces are acting on an object

(an object's weight is the force that gravity exerts on the object.)

What is weight?

weight is the force acting on an object due to the presence of Earth

essentially - the force of gravity on an object

What single word describes what Gravity is?

Universal! Gravity is universal.

(My mass affects the planet Neptune and the galaxy M31, and every other object in the universe, and their masses affect me—although not much, because they are so far away and my mass is relatively very small)

An object orbiting Earth, and any object for that matter, is actually...

falling! (being accelerated due to the gravitational force) towards Earth's center

Objects orbiting each other actually revolve around...

their mutual center of mass!

(like a magnet almost)

A closed orbit is...

An orbit that repeatedly returns to the same starting point, and therefore the speed is always less than the escape velocity

An open orbit is...

An open orbit is one that doesn't return to the same angular position - the body only approaches once, and then flies off again to infinity!

(How spaceships & rockets maintain flight - it's through an open orbit!)

Newton proved that any object moving in a closed orbit according to the inverse square law must follow...

an elliptical path!

The Moon and all objects in the universe will remain on their respective paths forever unless...

an external force (such as a collision with another object) acts on them.

According to the law of gravitation, the planets move faster when...

they are closer to the Sun

What were Newton's laws of motion? (Simple definition)

His laws of motion were general laws that described the motions of all bodies under the action of external forces!

What is the physics of heat known as?

Thermodynamics!

What temperature unit do scientists usually use?

Kelvin! (K; don't use degrees - ex. 87 K)

What is the freezing point of water in Kelvin?

273.15 K

How is absolute zero written? (temperature)

0 K

This is achieved when all atoms making up a sample are in their ground state. It can never be achieved in the laboratory, though some scientists have gotten close to doing so!

What do we call temperature? (In terms of energy)

The average kinetic energy (energy of motion) of atoms

When we "take the temperature" of something, we're really...?

Measuring the average kinetic energy of the atoms that make up the mass of what is being tested

The total kinetic energy of all particles in a system is often referred to as...

Thermal energy!

In terms of a solid, speed and amplitude of vibration of atoms is an indication of...?

the object's temperature!

How is heat transferred from one body to another? (Three mechanisms)

1) Conduction
2) Convection
3) Radiation

When does conduction occur?

When heat passes from a hot area of an object to a cooler area; heat is passed molecule by molecule

(Another instance - when the atoms in one part of the substance vibrate or oscillate faster, or in the case of a gas move around faster, (meaning a higher temperature) than at another part of the substance (meaning a lower temperature))

What happens to the "heat energy" in the case of conduction?

It is transferred from one part of the object to another in an attempt to make all parts of the object equal energy-wise, a spreading out or sharing of the thermal energy through diffusion

(ex. Metals are great conductors of heat; best conductors are solids)

How does heat transfer in the case of convection?

By the actual transfer of mass (unlike conduction where one atom/molecule jostles the one next to it and so on)

For example - boiling water:
The bottom of the pot gets hot (conduction at work as the bottom of the pot is in contact with the hot stove element), warming the water in contact with the bottom of the pot. Warm water is less dense than cold water so the warm water rises and is being replaced by cooler water from above and a convection cell is established.

What is one of the ways that terrestrial planets and moons cool down? (like Earth, Mars, and Titan)

Convection!

Explanation: Heat from the hot core of the planet heats up the portion of the mantle that it is in touch with core; this rocky material moves (slowly) to the outer part of the planet (similar to our warming pot of water) being replaced by cooler material from the upper portion of the mantle, and thus a convection cell is established.

The average photon energy depends on...?

the object's overall temperature!

What do photons do in the case of radiation?

Eventually some of these photons make their way to the object's surface and are radiated away from the object, taking energy with it, and thus cooling the object overall

What is it called when heat is transferred through light?

Electromagnetic (waves), though it is commonly called radiant energy or thermal radiation

When an object cools by emitting light the radiation is not at one specific frequency (colour) but rather a...?

spectrum (range) of frequencies depending on the temperature of the object!

How the thermal radiation spectrum depends on the temperature of the emitting object, Rule 1:

Hotter objects emit more total radiation per unit surface area

(ex. a 600 K object radiates 16 times as much energy as a 300 K (room temperature) object)

How the thermal radiation spectrum depends on the temperature of the emitting object, Rule 2:

Hotter objects emit photons with a higher average energy

(Ex. a fireplace poker which is relatively cool emits infrared radiation (not visible to us) but as it heats up it gets red (emitting higher energy photons) and at still hotter temperatures it might get white hot (emitting yellow and blue photons along with the red))