How old is Earth? How fast can you think? How long is a light year and how short is a femtosecond? What does Greenwich Mean Time mean? Can you tell the time with flowers? When did time begin? This light-hearted, illustrated miscellany from Royal Observatory Greenwich goes a long way to answering some of these questions and also presents a whole range of other amazing facts and figures which show the influence of time on our daily lives Visit Us.
Search Want to search our collection? Twilight is the name given to the period between dawn and sunrise, or between sunset and dusk, when light is still visible in the sky due to sunlight scattering off the atmosphere. It can also be separated in astronomical, nautical and civil sections by how far below the horizon the Sun is.
Sunrise and sunset are the points at which the top edge of the Sun reaches the horizon; the only difference between them is the direction in which the Sun is moving at the time. It actually occurs when the top of the Sun is 0.
Let us know take a closer look at each one in further detail, before moving onto some other similarly related questions you may have around this time of day. Sunrise is when the suns breaks the horizon, and when the upper part of the sun can be visibly seen by an observer. The timing of sunrise differs depending on the time of the year, along with the observers location longitude, latitude, altitude, and time zone. While dawn and sunrise occur at a similar time, the main difference is that one is a process whereas the other is an event.
Dawn is seen as a time of the day and process , whereas sunrise an event that happens during this time. In fact, the first hint of daylight occurs before the sun actually rises. It is only when the sun becomes visible that the term sunrise should be used.
For example, at the equator, it can be as little as 70 minutes, whereas in the polar regions it can span multiple hours. So, where you are on earth largely impacts what you can expect.
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