How do sunrise and sunset times change with altitude?
Hi, I am a professional airline pilot and an amateur astronomer and would appreciate it if could provide me with a formula or method in how to calculate the affect of altitude on sun set/rise at different latitudes and if there is any way to predict time of sun set/rise while flying.
At most latitudes on the Earth, the effect of increased altitude is the same: it makes the Sun rise earlier and set later than it would at that same location from the ground. To make things simple, let's assume that you are in a plane over the ocean, at the equator at sunset. In that case, straightforward trigonometry indicates that at a typical commercial airplane altitude of 12000 metres, you can see an extra 2 degrees "around" the Earth. Since the Earth moves around the Sun at a rate of a quarter of a degree a minute, it means that at this altitude, sunset occurs 8 minutes later than it would from the ground. The variation with altitude is approximately linear, and so we conclude that sunset is later by 1 minute for every 1.5 kilometres in altitude, and that sunrise is earlier by the same amount.
Now, all of this is complicated somewhat by the fact that you don't stay in one place in a plane, but you travel in a given direction: if this direction is predominantly East or West, then the plane's motion will completely change the answer we got above (in particular, travelling West at sunset can lengthen the latter significantly in a commercial jet). So, the results above are valid in a plane if a) the plane is moving rather slowly (like a personal plane) or b) the plane is travelling in the North-South direction.
Get More 'Curious?' with Our New PODCAST:
- Podcast? Subscribe? Tell me about the Ask an Astronomer Podcast
- Subscribe to our Podcast | Listen to our current Episode
- Cool! But I can't now. Send me a quick reminder now for later.
- Why can we see the sun's image before sunrise and after sunset?
- How is the time of sunrise calculated?
- How much can the location of sunset differ from due West?
How to ask a question:
If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist
This page has been accessed 29538 times since November 10, 2002.
Last modified: April 17, 2003 8:40:00 PM
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.
Warning: Your browser is misbehaving! This page might look ugly. (Details)