Stellar Society
The cause of seasons on Earth is because of the varied distance between Earth and the Sun. When they are close to each other, it’s summer on Earth. Does it make sense? Why?
It doesn’t make sense. The distance between Earth and the Sun doesn’t significantly vary, and even if this is the cause, there will not be significant differences in season on the two hemispheres. The main cause is the axis tilt of the Earth, which points one hemisphere more directly to the Sun, and expands its exposure time.
All known stars rise in the east and set in the west, and we will never discover a star that will rise in the west and set in the east. Does it make sense? Why? (CP51-23 adjusted)
It makes sense. The movement of the stars is due to the rotation of Earth itself. Since the direction of Earth’s rotation stays the same, the stars will always rise in the east and set in the west.
Define speed, velocity, and acceleration. What are the units of acceleration? What is the acceleration of gravity? (CP102-1)
The speed measures how far an object would go in a certain amount of time.
The velocity measures both an object’s speed and direction.
The acceleration measures the change of velocity, whether in speed or direction or both. The acceleration of gravity measures the acceleration of a falling object.
Suppose you could enter a vacuum chamber (a chamber with no air in it) on Earth. Inside this chamber, a feather would fall at the same rate as a rock. Does it make sense?
It makes sense. Because the acceleration of gravity experienced by both rock and feather is the same, regardless of their mass, the two objects would fall at the same rate if they were both released from rest.
What are the 8 major planets in our Solar System from the closest to the farthest relative to the Sun?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus(天王星), Neptune.
What are the two key properties of a telescope?
(A) Light-collecting area.
(B) Magnification.
(C) Angular resolution.
A and C
Because of their higher frequency, X-rays must travel through space faster than radio waves. Does it make sense? (CP131-20)
It doesn’t make sense. All electromagnetic waves move at the same speed c, the speed of light. the difference in frequency will cause the variation in wavelength, though.
When the sky is completely dark and there is no man-made light around the city, the only possible source of light is the stars in the night sky. Does it make sense? (Hint: What is light?)
It depends on the definition of light. Even if we can’t see much light in this scenario, there are other forms of light to visible light, typically radio waves.
What are latitude and longitude? Does the local sky vary with latitude? Does it vary with longitude? Explain. (CP 50-7)
Latitude measures N-S position on Earth and longitude measures E-W position. The local sky does vary with latitude, but it doesn’t vary with longitude. Typically, people living in the Southern hemisphere don’t see Polaris in their night sky.
The star Betelgeuse is about 600 light-years away. If it explodes tonight, we’ll know because it will be brighter than other stars in the Sky. Does it make sense? (CP22-26 adjusted)
It doesn’t make sense. The light from 600 light-years away will arrive on Earth 600 years after the event happens.
Briefly describe key facts about the solstices and equinoxes（分点）. (CP50-10)
Solstices: when the s N or S hemispheres are tipped most directly toward the Sun.
Equinoxes: when the sun-lit area in the N and S hemispheres becomes equal.
Properties: difference in temperature, biological activities, and sun-lit time. Which is concluded as “seasons”.
For an astronaut working at the International Space Station, he will nearly not experience gravity because he is too far from the surface. Does it make sense?
It doesn’t make sense. It’s gravity that makes the object orbit the planet, so the astronaut must have experienced gravity. However, because of its tangent speed, he will not fall to the ground but stay in the same orbit. It makes him experience weightlessness because he is constantly free-falling, but it doesn’t mean that he doesn’t experience gravity.
How much greater is the light-collecting area of a 6-meter telescope than that of a 3-meter telescope? (CP132-33)（Hints：The amount of light collected by a telescope is proportional to the area of the telescope.）
4 Times
What is the basic layout of the solar system? (Including the Star, types of planets, asteroids, comets, and dwarf planets.)
The Sun, terrestrial planets, the asteroid belt, Jovian planets, the Kuiper belt (including the dwarf planets and comets), Oort cloud.
5. About how old is the solar system, and how can we know?
(A) 4.5 million years.
(B) 4.5 billion years.
(C) 4.5 trillion years.
(B) 4.5 billion years. Scientists can measure the age of the solar system using the asteroids fallen on Earth through radiometric dating.
How do we know our universe is expanding? If so, where did the Big Bang Theory come from?
Two facts were recognized by Edwin Hubble in the 1920s:
(1) Almost every galaxy outside the Local Group is moving away from us.
(2) The more distant the galaxy, the faster it appears to be racing away.
Using the Cake Analogy, if the universe is expanding along with the movement of the stars in the universe at a constant speed, it would show up in correspondence with the two facts mentioned above.
To think further, if the universe is expanding constantly, we can deduce that the universe starts with a dot by reversing the time. This is the basic idea of the Big Bang Theory.
Suppose you got lost and don’t know where you are on Earth, and you also lost all your electronic devices. How can you know your latitude according to the night sky?
Find the altitude of the celestial pole from your horizon. (Northern hemisphere: Polaris; Southern hemisphere: center of the orbit of Southern Cross.) As you find this number, it’s the same number as your latitude.
The dwarf planet Eris orbits the Sun every 557 years. What is its average distance (semimajor axis) from the Sun? (CP79-38)
According to Kepler’s 3rd law applied to the Solar System:
A spectral line appears at a wavelength of 321 nm in the laboratory appears at a wavelength of 328 nm in the spectrum of a distant object. What can we learn about this object? (CP132-32, adjusted)
Because the wavelength is stretched, we say this wave is redshifted, which means the object is moving away from us.
All planets in the solar system orbit the Sun in the same direction. They rotate in the same direction as well, and they all have a similar small axis tilt. Evaluate this statement.
Indeed, all planets orbit the Sun in the same direction due to the contraction of the Solar Nebula. However, Venus has a clockwise rotation direction when seen from Earth’s north pole, and Uranus has an axis tilt of 97.9 degrees.