Test 1 Flashcards
Why does the Sun and stars rise in the East and set in the West each day?
The Sun and stars appear to rise in the East and set in the West due to the counterclockwise rotation of the Earth on its axis.
What is a solar day?
The solar day measures the amount of time it takes for the Sun to return to its originally measured location in the sky. It is slightly longer than the sidereal day because of Earth’s movement along its orbit as it rotates.
What is a sidereal day?
The sidereal day measures the amount of time it takes for a star to return to its originally measured location in the sky.
What is precession and what causes it?
Precession refers to the motion in the direction of the Earth’s axis. Because our planet bulges at the equator and is not an exact sphere, the gravitational pull of the Sun and the Moon cause it to wobble.
Explain why there are seasons on Earth.
The seasons on Earth are caused by the 23.5-degree tilt of the Earth’s axis. In the summer months, the Northern Hemisphere “leans into” the Sun and is more directly illuminated, whereas in winter months the Northern Hemisphere “leans away” from the sun. In the fall and spring months, the Earth “leans sideways” -neither into the Sun nor away from it, so the two hemispheres are equally favored with sunshine.
What is the difference between a day and a year?
A day measures the Earth’s rotational period on its axis and a year is the Earth’s revolution period around the Sun.
What is a constellation?
a human grouping of stars in the night sky into a recognizable pattern
What is a solar system?
Any star system that has planets in orbit
What is a galaxy?
a cluster of gravitationally bound stars
What is the universe?
the universe is everything. Everything that exists, does so within the universe.
What is a solstice?
A solstice refers to the point in time when the Sun has reached its highest and lowest points along its ecliptic path.
What is an equinox?
The equinoxes refer to the point at which the Sun crosses the celestial equator along its ecliptic path.
In the summer, which is longer for us: day or night? Why?
The days are longer in the summer for us because during these months the north pole is leaning towards the Sun, exposing more of the northern hemisphere to daylight.
If we lived on the Equator, which would be longer for us in the summer: day or night? Explain.
At the equator, day and night would be roughly equal year round because the equator is perpendicularly aligned to the Earth’s axis.
If we lived on the North Pole, how many hours of daylight are there in the summer? Explain.
During the summer, the North Pole receives 24 hours of daylight because the North Pole of the Earth’s axis is tilted towards the Sun, causing the Sun to remain above the horizon.
If we lived on the South Pole, how many hours of daylight are there in the summer? Explain.
During the summer, the South Pole receives 0 hours of daylight because the South Pole of the Earth’s axis is tilted away the Sun, causing the Sun to remain below the horizon.
What is the name of the star we call the North Star? Has this always been the North Star? Why or why not?
Our current North Star is called Polaris. It hasn’t always been the North Star and this is because of the precession of the Earth which changes the direction of the Earth’s axis.
Describe why the Moon has phases.
The moon has phases due to its orbit around Earth. As it moves around the Earth it changes how much of the moon’s sunlit side is visible from Earth.
When the Moon is on the side of the Earth that is away from the Sun (when we have a full Moon), why doesn’t the Earth always block the Sun’s light to the Moon?
The Moon remains lit due to its orbit being tilted 5.2 degrees relative to the Earth’s orbit.
What is a solar eclipse?
A solar eclipse occurs when the Moon lines up between the Earth and the Sun, with the Moon casting its shadow (umbra) on Earth.
What is a lunar eclipse?
A lunar eclipse occurs when the Earth lines up in between the Sun and the Moon, with the Earth casting its shadow on the Moon.
Is the far side of the Moon always dark? Explain.
No, the far side of the moon receives just as much sunlight as the near side, its just not visible from Earth.
What is parallax, and how is it useful for measuring distance?
The concept of parallax imaging is used in astronomy to determine the distance of celestial objects from Earth. By measuring the apparent change in position of a star from different lines of sight we can determine the parallax angle with a little geometry. The distances across space are way too vast for direct measurements to be considered practical.
If two people come up with different theories to explain something, how do we determine who is correct?
If both theories explain the phenomenon equally well, the simpler one (fewer assumptions) is often preferred, which is known as Occam’s Razer.
Name five physical differences between the terrestrial planets and the Jovian planets.
- Terrestrial planets are smaller than Jovian planets.
- Terrestrial planets have a rocky surface and Jovian planets are gaseous.
- Terrestrial planets have higher densities than the Jovian planets.
- Terrestrial planets have few, if any moons whereas Jovian planets have many moons.
- Terrestrial planets have no rings while Jovian planets all have ring systems.
What is an astronomical unit? Write down the distances from the Sun, in astronomical units, for each planet in our solar system.
An astronomical unit (au) utilizes the distance from the Earth to the Sun, approx. 150 million km, as a standard unit of measurement to describe distances.
What planets are asteroids and meteoroids like? Comets are like the moons of what planets?
Asteroids and meteoroids are more like the terrestrial planets in terms of composition and comets are more like the moons of the Jovian planets, which is a mixture of rock and ice (frozen gases).
Describe the difference between a meteor and a meteorite.
A meteor is a meteoroid that has entered the Earth’s atmosphere and burns up due to the friction with the air. A meteorite is any part of a meteor that has landed on the Earth’s surface.
Describe what a comet is.
A comet is a celestial body composed of frozen gas, dust, and rocky material that forms a coma when they get near the sun as the frozen gases melt and evaporate.
Which way do the tails of a comet point?
The tail of a comet points in the opposite direction of the Sun due to the solar winds (radiation and particles) generated by the sun.
