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Sidereal day is defined as the time between successive crossings by any reference star of any observer’s celestial Meridian. It literally means the star day. Similarly, the period between successive crossings of the sun on any observer’s Celestial Meridian is called a solar day (Kaler, 2002). We basically use the solar time in our day to day life. We measure solar day and hours on our clocks and watches.
- One solar day = 24 solar hours
- One sidereal day = 23 hours 56 minutes
We can experimentally show the difference between the sidereal and the solar day. It is an observational experiment which requires focus and concentration of the observer to find the exact between the two types of days (Smith, 1988).
The aim of the experiment would be to determine the length of the sidereal day in solar hours by measuring the time difference a bright star takes to reach a certain spot on the sky on different night. The experiment can be carried out at any time of the year.
- The first step of the experiment involves selecting a bright naked-eye star, which is well placed in the sky about an hour after sunset.
- Identify a sharp object as a reference point for the selected bright star to measure the exact time at which the star reached the same position.
- The basic concept behind this experiment is to measure the exact time the star disappears behind the reference sharp object on one night. This observation has to be repeated for several nights later (Koupelis, 2010).
- There are important factors that have to be taken into consideration like calibrating the clock or watch that is used to measure the time to the true solar time, this can be done by referencing the time announced in the radio station or checking the internet, ets.
- Each night the selected star will follow the same path across the sky, through appearing in the same location earlier and earlier each night. Now, we need to accurately measure the time at which the selected bright star reaches a certain position in the sky and repeat the observation for the days to follow.
- Finally, we can find the difference of 4 minutes per day in the sidereal day to the solar day.
- This can be related to the movement of the earth for the full 360 degrees in its orbit. It takes 4 minutes for the earth to move 1 degree. As there are 365 days in a year and there being only 360 degrees earth has to travel that extra 1 degree to before the sun next crosses the same meridian in the second position (Smith, 1988).
Hence, we have the leap year for every 4 years to accommodate the 366.26 sidereal days in the calendar.
How would a planet orbiting a first generation star be different than planets formed today? Could humans exist on that world?Why or why not?
Planets orbiting a first generation star would have contained hydrogen and helium (Leuschner, 1935). Planets forming today contain elements that were made in the star as well as those made in the big bang. Living organisms need carbon and oxygen, and the elements iron and silicon are crucial for building planets on which life can exist (Ginzburg, 2004). Human cannot exist on that earlier world because the earlier planets would just be made of hydrogen and helium, and life could not have existed there.
best explanation for the presence of the moon.
The collision-ejection theory applies the established fact of the age-old collisions in the solar system to the formation of the moon. This theory proposes that the newly formed earth was struck at an angle by a mars-sized planetesimal that splashed some of the earth surface layers into orbit around it (Gibbons, 1998). The material that formed the moon came from earth’s crust and mantle, but not its iron-rich core. This matter becomes a short-lived ring that finally c.............
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