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The time when the upper rim of the Sun appears on the horizon in the morning is known as sunrise (or sunup). The word can also apply to the full process of the sun disc crossing the horizon and the atmospheric disturbances that follow it.
The daily disappearance of the Sun below the horizon owing to Earth’s rotation is known as sunset or dusk. The equinox Sun sets due west at the moment of both the Spring and Autumn equinoxes as seen from everywhere on Earth (excluding the North and South poles). The sun sets to the northwest in the Northern Hemisphere’s spring and summer, and to the southwest in the autumn and winter, as seen from the Northern Hemisphere; the seasons are reversed in the Southern Hemisphere.
Refraction in the air causes the phenomenon of early sunrise and late dusk. In this scenario, the Sun appears to rise 2 minutes earlier and set 2 minutes later. The Sun’s rays are refracted when they hit the atmosphere. As a result, the Sun appears to be in an elevated position, indicating that it has already risen. The Sun appears in the sky after it has set due to the same refraction phenomenon. This entire process is caused by variations in the atmosphere’s refractive index. In this essay, we’ll go deeper into the reasons for the later sunset and earlier sunrise.
The variation in the refractive index of the atmosphere is responsible for the entire sequence.
What Factors affect sunrise and sunset times
Longitude: The imaginary lines that travel vertically around the globe, intersecting at the North and South Poles, are known as longitude lines. Longitude refers to how far east or west a location is in regard to a single imaginary line known as the Prime Meridian, which passes through the town of Greenwich, England. The Sun appears to the east of any given position each day because the Earth rotates clockwise. The Sun’s light travels 15 degrees longitude in about an hour. This is why the East Coast receives the Sun’s beams each day before the West Coast.
Latitude: Latitude lines are imaginary horizontal lines that encircle the earth. Latitude refers to how far north or south a location is in reference to the Equator, the imaginary line that circles the globe’s centre. Latitude lines, unlike longitude lines, never cross. Because the Earth’s radius is less towards the poles than it is in the center, extreme northern and southern places experience more variations in the length of their days than those closer to the Equator. While equatorial locales enjoy about 12 hours of daylight and darkness each day all year, sites closer to the North and South Poles might have several months of constant sunlight or darkness. The majority of North Americans live somewhere in the middle of these two areas.
Altitude: As if all of these variables weren’t enough, altitude plays a role as well. In general, the higher you are above sea level, the earlier the Sun rises and the later it sets, compared to when the same area would be at sea level. Remember that sunrise will be one minute earlier for every mile of altitude gained, and sunset will be the same amount of time later.
Causes of Advanced sunrise and sunset
Advanced Sunrise
The Sun’s rays are refracted when they hit the atmosphere. As a result, the Sun appears to be in a position where it has already begun to rise.
During sunrise, the sun rises above the horizon. The sun’s rays are refracted as they travel from more dense air to less dense air. The human eye also perceives solar rays as a straight line, creating the impression that the sun has risen. However, it has not yet risen in reality.
Delayed Sunset
We may see the sun’s apparent location rather than its true position when it sets beneath the horizon after night. Sun beams that travel from denser air to rarer air are refracted by atmospheric refraction and appear to come from above the horizon. The fact that human eyes see light as travelling in a straight line gives the impression that the sun hasn’t set.
Conclusion
Refraction is the bending of a light wave’s path when it passes across the boundary between two mediums.
The phenomenon of atmospheric refraction causes delayed sunset and advanced sunrise.
The Sun appears to rise 2 minutes earlier and set 2 minutes later than it does in reality.
Solar rays appear to the human eye as a straight line.
The Refractive Index is calculated by dividing the speed of light in a vacuum by the speed of light in a second medium with a higher density (Index of Refraction).
The air density rises as light travels from space into the atmosphere, changing the refractive index. As a result, the degree of refraction increases, causing the light to bend.
