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PHYS1160-Introduction to Astronomy - T3 2021 Dashboard  My courses  PHYS1160-5219_01557  Module 1 (Weeks 1 & 2) — Introduction  PHYS1 Started on Wednesday, 3 November 2021, 12:32 AM State

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Completed on Wednesday, 3 November 2021, 12:38 AM Time taken 5 mins 42 secs Grade

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Astronomy had very practical applications in the past, such as navigation and time keeping. The image shows an instrument called nocturnal that was used to determine time at night by observations of stars.

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The Phases of Venus and the Copernican Model In lesson 1 we saw how Galileo's observations of the phases of Venus provided important evidence that helped support the Copernican model of the Solar System. In this activity we will investigate that idea further. 

Question 1 Correct Mark 1.00 out of 1.00

Firstly it is important to understand what we mean by "phases" in this context. Phases are what we are familiar with in the case of the Moon. The Moon changes from being a thin crescent to being a full Moon depending on how it is being illuminated by the Sun Lets try a few questions to see if you understand the Moon's phases.

This animation shows a bit more than just the phases of the Moon. It shows that the Moon's size changes slightly because its orbit is elliptical and non-circular. The animation also shows the wobble in the orientation, which is called libration. How long does it take the Moon to go through a full cycle of phases - from one full moon to the next? (2 attempts) Select one: About a month About two weeks About a day About a year

Your answer is correct.

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The Phases repeat in about a month because this is the Moon's orbital period about the Earth. The correct answer is: About a month

Question 2 Correct Mark 1.00 out of 1.00

You see the Moon high in the sky at midnight. What phase is the Moon likely to show? (2 attempts) Select one: New Moon

Full Moon Crescent Moon

Your answer is correct. The Moon can only be full (or close to it) because if it is high in the sky at midnight it is roughly opposite where the Sun is and so will be fully illuminated. The correct answer is: Full Moon

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Venus shows phases similar to those of the Moon. However, we didn't know about them until Galileo first applied the telescope to astronomy. The phases of Venus are too small to be seen with the naked eye, but could be clearly seen in Galileo's telescope.

Galileo's drawings of the phases of Venus From these drawings we can see that: Venus shows a range of phases varying from a crescent to a full phase. Unlike the Moon, Venus varies substantially in size being much larger at crescent phase than at full phase.

Question 3 Correct Mark 1.00 out of 1.00

The Ptolemaic (geocentric) model here shows Venus orbiting inside the orbit of the Sun around the Earth. It is carried on an epicycle and the epicylce moves around the Earth on a larger circle (called the deferent) that orbits the Earth with a one year period the same as the Sun. This is needed to explain the apparent motion of Venus. It is always seen near the Sun, either in the evening sky just after sunset or in the morning sky just before sunrise. The simulation below shows how the phases of Venus would be produced on two models of the Solar system. Start by looking at the Copernican Model. 

When Venus is at a "Full" phase how are Venus, Earth and the Sun positioned: (2 attempts) Select one: In a line with Venus and Earth on the same side of the Sun In a triangle with the right angle at the Sun In a line with Venus and Earth on opposite sides of the Sun

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Your answer is correct. In a line with Venus and Earth on opposite sides of the Sun is the correct answer. The correct answer is: In a line with Venus and Earth on opposite sides of the Sun

Question 4 Correct Mark 1.00 out of 1.00

Galileo observed particular features while observing Venus, namely, Venus changing in apparent size, and the phases of Venus. Use the check boxes to show which of these features are predicted by the Copernican model and which by the Ptolemaic model. (2 attempts) Select one or more: The Copernican model predicts that Venus changes its apparent size in the sky as viewed from Earth as Venus goes through its phases

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The Ptolemaic model predicts that Venus changes its apparent size in the sky as viewed from Earth as Venus goes through its phases

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The Copernican model predicts that Venus is sometimes seen at full phase

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The Ptolemaic model predicts that Venus is sometimes seen at full phase The Copernican model predicts that Venus is sometimes seen at a crescent phase The Ptolemaic model predicts that Venus is sometimes seen at a crescent phase

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Your answer is correct. The correct answers are: The Copernican model predicts that Venus changes its apparent size in the sky as viewed from Earth as Venus goes through its phases, The Ptolemaic model predicts that Venus changes its apparent size in the sky as viewed from Earth as Venus goes through its phases, The Copernican model predicts that Venus is sometimes seen at full phase, The Copernican model predicts that Venus is sometimes seen at a crescent phase, The Ptolemaic model predicts that Venus is sometimes seen at a crescent phase

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The Copernican or Heliocentric model predicts all the features that Galileo observed for Venus. The Ptolemaic model can only predict two of the three features. It is not consistent with the observation that Venus goes through a full (fully illuminated) phase. This never happens in the Ptolemaic model because Venus never passes behind the Sun. This was one of the key pieces of evidence providing support for the Copernican or Heliocentric Model.

Question 5 Correct Mark 1.00 out of 1.00

What is the main reason that Galileo was able to solve the problem of determining the correct model of the Solar System when earlier scientists had not been able to do this? (2 attempts) Select one: Galileo applied correctly "the scientific method" of forming a hypothesis and carrying out an experiment to test that hypothesis. Galileo had access to technology that had not been available to earlier scientists.

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Galileo was smarter than earlier scientists.

Your answer is correct. Galileo was able to apply the new technology of the telescope to the problem and therefore able to make the discoveries of the phases of Venus, and Jupiter's moons that helped to solve the problem. This is an example of the fact that Scientific discoveries often don't follow the commonly presented definition of "scientific method". Instead there are many factors that can contribute to scientific advances. The correct answer is: Galileo had access to technology that had not been available to earlier scientists.

Question 6 Correct Mark 1.00 out of 1.00

Which of the following objects would go through a full range of phases from crescent to full? Select all that apply. (2 attempts) Select one or more: Mercury as seen from Earth

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Jupiter as seen from Earth Earth as seen from Mars

Your answer is correct. You can see planets going through the full set of phases, only when they are in an orbit that is smaller than the orbit of the planet, which you are making your observations from. The correct answers are: Mercury as seen from Earth, Earth as seen from Mars

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Phases We see a full cycle of phases from any planet whose orbit is inside that of the planet we are viewing from. On Earth we see phases for the planets Mercury and Venus, but not for Mars, Jupiter etc. However from Mars we would see phases for Earth as well. The picture here shows a crescent Earth and Moon as seen from a NASA spacecraft in orbit around Mars.

Question 7 Correct Mark 1.00 out of 1.00

Parallax This simulation illustrates the parallax effect that astronomers use to measure the distance of stars (the size of the effect is grossly exaggerated here). Parallax causes a star to change its position against the background of more distant stars as the Earth moves round the Sun. 

A large parallax movement means: (2 attempts) Select one: The star is relatively distant from us The star is relatively close to us

Your answer is correct. A large parallax movement means a relatively nearby star.

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A more distant star would have a smaller parallax. The correct answer is: The star is relatively close to us

Question 8 Correct Mark 1.00 out of 1.00

What does this image show? (1 attempt) Select one: Our own Milky Way galaxy A spiral galaxy similar to the Milky Way The Solar System A Planetary Nebula

Your answer is correct. It isn't possible to photograph our own galaxy like this because we are inside it. The Solar system is just our Sun, the planets and smaller objects that revolve around it. A planetary nebula is formed in the late phase of stellar life. It is a shell of gas expelled by a star. The image such an object, called Ring Nebula is shown below.

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This is the Andromeda galaxy, the closest spiral galaxy to our own Galaxy, the Milky Way. Astronomers found that our Galaxy has a similar shape and size to Andromeda galaxy. The correct answer is: A spiral galaxy similar to the Milky Way

Question 9 Correct Mark 1.00 out of 1.00

'Light year' is a term used by astronomers. Select all correct statements. (1 attempt) Select one or more: A light year is a measure of time used by astronomers. The Alpha Centauri system is the closest system of stars to the Sun. It is about 4.3 light years from the Sun.

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Light years are used to measure the distances to stars because the numbers would be extremely large if expressed in more common units such as kilometres.

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A light year is the distance that light travels in one year.

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Your answer is correct. Only option A is incorrect, because light year is a measure of distance not time. The correct answers are: The Alpha Centauri system is the closest system of stars to the Sun. It is about 4.3 light years from the Sun., Light years are used to measure the distances to stars because the numbers would be extremely large if expressed in more common units such as kilometres., A light year is the distance that light travels in one year.

Question 10 Correct Mark 1.00 out of 1.00

Select the term that best fills the blank in each sentence. (1 attempt) The distance between the Sun and the Earth is called

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, that is about

150,000,000 km. An enormous region of space with many clusters of galaxies is called a The orbit of a planet around the Sun is in the shape of

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Your answer is correct. The correct answer is: Select the term that best fills the blank in each sentence. (1 attempt) The distance between the Sun and the Earth is called [an astronomical unit], that is about 150,000,000 km. An enormous region of space with many clusters of galaxies is called a [supercluster]. The orbit of a planet around the Sun is in the shape of [an ellipse].

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