Two penguins are standing at the South Pole.
One walks northwards, and the other turns and
walks in the opposite direction. What direction
is this? Explain.
How do we know that the Earth is spherical?
Give at least two reasons.
The diameter of the Earth is about 13 000 km.
Calculate its circumference.
In winter the sun is more to the north (lower in
the northern sky) than it is at the same time in
summer. Why is this?
Find out the meanings of the terms solstice and
equinox.
Where is the ‘Land of the Midnight Sun’? Why is
it called this?
In Darwin, the Earth’s surface is travelling at
about 1500 km/h. In Melbourne it is travelling at
only 1000 km/h. Why is this?
The planet Mercury is not tilted. It rotates slowly
on its axis once every 59 Earth days, and
revolves around the sun in 88 Earth days. What
would the days, nights, years and seasons be
like?
Look at the photo of the star trails.
If you were at the equator and pointed the camera straight up, the trails would
be straight lines. Try to explain this.
To answer the question about the penguins walking in opposite directions, we can determine the direction based on the reference point. If we consider the South Pole as the reference point, the penguin that walks northwards is moving away from the South Pole, so its direction is away from the South Pole. The other penguin, walking in the opposite direction, is moving towards the South Pole. So we can say its direction is towards the South Pole.
To know that the Earth is spherical, there are several reasons:
1. The shape of the Earth's shadow during a lunar eclipse: When the Earth passes between the Moon and the Sun, it casts a round shadow on the Moon's surface. The curved shadow indicates that the Earth is spherical.
2. The phenomenon of ships disappearing over the horizon: As a ship sails away from shore, it starts to disappear from the bottom up. This happens because the Earth curves away from our line of sight. If the Earth were flat, we would be able to see the entire ship at all times.
Now let's calculate the circumference of the Earth given a diameter of about 13,000 km. The circumference of a circle can be found using the formula C = πd, where C is the circumference and d is the diameter.
C = π(13,000 km)
C ≈ 40,840 km
Therefore, the circumference of the Earth is approximately 40,840 km.
During winter, the sun appears more to the north (lower in the northern sky) compared to summer due to the tilt of the Earth's axis. The Earth rotates on an inclined axis, which causes different regions to receive varying amounts of sunlight throughout the year. During winter in the northern hemisphere, the North Pole is tilted away from the Sun, resulting in the Sun appearing lower in the sky and giving less direct sunlight.
Solstice and equinox are astronomical terms:
1. Solstice: These occur twice a year, in December and June, when the Sun reaches its highest or lowest point in the sky at noon. In the Northern Hemisphere, the December solstice marks the winter solstice and the June solstice marks the summer solstice.
2. Equinox: These occur twice a year, in March and September when the Sun shines directly on the equator. These are the moments when day and night are of approximately equal length all over the world.
The "Land of the Midnight Sun" refers to regions near the Arctic Circle, such as parts of Norway, Sweden, Finland, and Alaska. During the summer months, the Sun doesn't fully set below the horizon, resulting in extended daylight hours, hence the term "Midnight Sun."
The difference in the Earth's surface speed between Darwin and Melbourne is due to the Earth's rotation. The Earth completes one rotation in about 24 hours. As you move closer to the poles, the distance traveled during each rotation becomes smaller, resulting in a slower surface speed. Darwin is closer to the equator, so its rotational speed is higher compared to Melbourne, which is located towards the southern hemisphere.
On the planet Mercury, due to its slow rotation on its axis and its shorter revolution around the Sun, the days and nights would be much longer than on Earth. One side of Mercury would experience scorching temperatures during its day, while the other side would be drastically colder during its night. The year, consisting of the time it takes for Mercury to complete one revolution around the Sun, would be significantly shorter than Earth's year. Due to its lack of axial tilt, Mercury does not experience seasons as we do on Earth.
When you point a camera straight up at the equator and capture star trails, the resulting trails appear as straight lines. This happens because at the equator, Earth's rotation moves the camera in a relatively straight path parallel to the celestial equator. The celestial equator is an imaginary extension of Earth's equator into space. The stars appear to rotate around the celestial pole, which is directly overhead at the Earth's poles and appears on the horizon at the Equator. This results in straight star trails when photographing at the equator.
The penguin that turns and walks in the opposite direction is walking southwards. This is because the South Pole is located at the southernmost point of the Earth, and any direction away from it would be towards the north.
Two reasons that indicate the Earth is spherical are:
1) The shape of the Earth's shadow during a lunar eclipse: When the Earth passes between the Sun and the Moon, it casts a curved shadow on the Moon. This curved shape indicates that the Earth is spherical.
2) The way ships disappear over the horizon: As a ship sails away from shore, it gradually disappears from view bottom-first. This happens because the Earth's surface curves away from the observer, making the ship disappear over the horizon.
To calculate the circumference of the Earth, we can use the formula: Circumference = π x Diameter.
Circumference = 3.14 x 13,000 km ≈ 40,840 km.
In winter, the sun appears more to the north and lower in the northern sky than in summer because the Earth is tilted on its axis. During the winter solstice, the northern hemisphere is tilted away from the sun, resulting in less direct sunlight and colder temperatures.
Solstice: A solstice occurs twice a year when the Sun reaches its highest or lowest point in the sky at noon, marked by the longest and shortest days of the year. The summer solstice is the longest day of the year, while the winter solstice is the shortest day of the year.
Equinox: An equinox occurs twice a year when the Sun is directly above the equator, resulting in equal day and night length. The spring equinox marks the beginning of spring, while the autumn equinox marks the beginning of autumn.
The "Land of the Midnight Sun" refers to regions near the Earth's poles, where the sun remains visible for 24 hours a day during certain parts of the year. This phenomenon occurs because of the tilt of the Earth's axis, causing the sun to remain above the horizon for extended periods of time.
The Earth's surface travels at different speeds at different latitudes due to the Earth's rotation. As we move away from the poles towards the equator, the rotational speed of the Earth increases. Therefore, in Darwin, which is closer to the equator, the Earth's surface is traveling faster (about 1500 km/h) compared to Melbourne, which is located at a higher latitude and travels at a slower speed (about 1000 km/h).
On planet Mercury, which is not tilted, the days and nights would each last for about 59 Earth days. The year on Mercury would be about 88 Earth days, as it takes that long for it to orbit the sun. The lack of tilt on Mercury would mean no variation in seasons.
The star trails in the photo appear as straight lines when pointed straight up at the equator because the stars appear to move in circles around the celestial poles. At the equator, the celestial poles are directly overhead, resulting in the stars appearing to move in straight lines as the Earth rotates.
1. The penguin walking in the opposite direction of north is walking south. This is because north and south are opposite directions, and when one penguin turns and walks in the opposite direction, it would be moving in the opposite direction of north, which is south.
2. There are several reasons why we know that the Earth is spherical. Two of them are:
a) The shape of the Earth's shadow during a lunar eclipse: During a lunar eclipse, when the Earth passes between the Sun and the Moon, the shadow cast by the Earth on the Moon is always round. This indicates that the Earth has a spherical shape.
b) The curve of the horizon: As we move away from a location, the horizon appears to curve downwards. This curvature is consistent with the Earth being a sphere.
3. The formula to calculate the circumference of a circle is given by C = πd, where C is the circumference and d is the diameter. Given that the diameter of the Earth is about 13,000 km, we can calculate its circumference as follows:
Circumference = π × 13,000 km
Circumference ≈ 40,840 km
Therefore, the circumference of the Earth is approximately 40,840 km.
4. In winter, the sun is more to the north (lower in the northern sky) than it is in summer due to the tilt of the Earth's axis. The Earth's axis is tilted at an angle of about 23.5 degrees relative to its orbit around the Sun. During winter in the northern hemisphere, the North Pole is tilted away from the Sun, causing the Sun to appear lower in the sky and resulting in shorter days and less direct sunlight.
5. Solstice refers to the two points in the year when the sun reaches its highest or lowest point in the sky at noon, resulting in the longest (summer solstice) or shortest (winter solstice) days of the year, respectively. Equinox refers to the two points in the year when the sun crosses the celestial equator, resulting in equal day and night lengths. These occur around March 20th (spring equinox) and September 22nd (fall equinox).
6. The 'Land of the Midnight Sun' refers to regions near the Earth's poles where the sun remains visible for 24 hours during certain times of the year. This occurs because of the tilt of the Earth's axis, causing the sun to remain above the horizon for extended periods. The term is typically used to refer to locations near the Arctic Circle, such as parts of Norway, Finland, and Alaska.
7. The Earth's surface travels at different speeds at different latitudes due to the Earth's rotation. The Earth rotates once on its axis every 24 hours, and since the Earth is a sphere, the distance traveled at each latitude varies. Locations closer to the equator have a larger circumference to cover in 24 hours, resulting in higher surface speeds. In contrast, locations closer to the poles have a smaller circumference to cover, resulting in slower surface speeds.
8. Given that the planet Mercury is not tilted, its axis remains perpendicular to its orbital plane. As a result, there would be no significant change in the length of days and nights on Mercury. However, due to its slow rotation (59 Earth days), one side of Mercury would experience extremely hot temperatures during its long "day," while the other side would experience extremely cold temperatures during its long "night." Seasons would be non-existent or minimal on Mercury.
9. When taking a photo of star trails, if you were at the equator and pointed the camera straight up, the trails would appear as straight lines. This is because, at the equator, the Earth's rotation is perpendicular to the direction of the camera. As a result, the stars appear to move in a straight line across the image as the Earth rotates.
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