- If the earth was to rotate at twice its present rate of rotation, which of these changes is likely to be observed?
A. There will be 2 days and 2 nights within 24 hours.
B. There will be only 1 day OR 1 night in 24 hours.
C. The 24 hour duration of the day-night cycle will not change.
D. The duration of each day will be 18 hours and night 6 hours.
Answers
Answer:
Examine the following figure, which demonstrates star trails that would be visible in a photo centered on the North Star (Polaris) when the camera's shutter is left open to reveal the path the stars are taking as they move during part of one night.
-All of the stars move in a counterclockwise path around Polaris.
-The stars closest to Polaris move in smaller circles.
The altitude of the North Star (how high it appears above the horizon) changes as one travels large distances to the north or south on Earth. This suggests that the imaginary celestial sphere (with the stars apparently fixed on its surface) seems to spin around the spherical Earth, with Polaris centered near the northern axis of rotation (the top of the sphere).
Use this interactive diagram (Flash required) to see how your local view of the celestial sphere would change as you change latitude on the Earth.
The following diagram shows a person standing on the Earth (where the ground is the green disk). The bottom (purple) half of the sphere is invisible to the observer, as it lies below the horizon. The zenith is the point in the sky directly above the observer (looking straight up). The cardinal directions are labeled on the horizon, and the meridian divides the sky into eastern and western halves.
north
Celestial motions over time periods longer than a day are less obvious. Say you went out at exactly the same time each night and looked at the sky, noting the position of a specific set of stars at that time with respect to reference objects on Earth, such as trees and buildings. The following figure shows how the stars would change position. Based on this figure, what is the most correct conclusion?
The stars appear to move westward from one night to the next
During the day, the Sun is too bright for us to see where it is located with respect to the constellations, but we can use our observations of stars at night to figure this out. Based on the way stars shift position over the course of a year, your knowledge of how the time of day is defined, and the fact that the same constellations are seen at the same place in the sky at the same time of night on a given day of the year, which of the following is most likely correct?
The Sun appears to move across the constellations over the course of a year, ending where it started with respect to the background stars by the end of that period.
The apparent path the Sun takes through the constellations over the course of a year is called the ecliptic. As seen in the figure shown, the Sun is in a different position on the ecliptic at different times of year. Assuming you are in the Northern Hemisphere, how would you expect the location of the Sun in your local sky at noon to differ from season to season?
The Sun will appear to be higher above the southern horizon in the summer than in the winter.
From our point of view on Earth, it feels as if we are stationary and the celestial sphere and Sun are all rotating around us. In actuality, however, the Earth is moving, rotating on an axis that is tilted with respect to the orbit it takes around the Sun.
Open the AstroTour called "The Earth Spins and Revolves." Watch the Introduction, and the first half of the Explanation (up until the interactive part).
Then, choose one of the following conclusions that best explains the cause of the shift from day to night
The shift from day to night is caused by the rotation of the Earth around its axis.
Determining what causes the seasons is not as straightforward as determining what causes day and night. We can begin by suggesting hypotheses and then testing them for their validity.
Let's start with the hypothesis that the seasons are caused by a variable distance between the Earth and the Sun. Sort the observations or physical laws below according to whether they argue for or against this hypothesis.
For Hypothesis-
Closer light source has stronger intensity.
Earth's orbit is elliptical.
Against Hypothesis-
S and N hemispheres
Explanation: