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Q: Physics Question: Jet Airplane Racing the Sun ( Answered ,   4 Comments )
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 Subject: Physics Question: Jet Airplane Racing the Sun Category: Science > Physics Asked by: nronronronro-ga List Price: \$3.00 Posted: 27 Jan 2004 16:29 PST Expires: 26 Feb 2004 16:29 PST Question ID: 300935
 ```Hi There ! Last night, I was on a jet flying due west as the sun was setting. I assume the airplane was going 400-600 MPH at 35,000 feet. The sun was balanced on the horizon, half in view and half out of view. Because we were heading west, the sun took a very long time (40-60 minutes) to set. This same sunset would have occurred in 5-15 minutes on the ground. A 5-star answer would be the speed required for an jet aircraft, such that the sun would seemingly rise in the west. Approximate speed is fine with me. No "heavy lifting" mathematics required. All comments greatly appreciated ! ron```
 Subject: Re: Physics Question: Jet Airplane Racing the Sun Answered By: pafalafa-ga on 27 Jan 2004 17:31 PST Rated:
 ```Hello again Ron, Interesting question (but then again, ALL your questions are interesting questions. Strange. But interesting.) The setting sun "travels" around the circumference of the earth in 24 hours. In other words, it travels 25,000 miles in 24 hours, or a bit over 1,000 miles an hour. Travel west any faster than that, and you will "reverse" the sun's direction, and it will rise in the sky, rather than set. Put it another way, when the sun sets in my hometown of Washington DC, it still has three hours yet before it sets in Los Angeles, about 3,000 miles away. If I could hop on the recently-departed Concorde and fly across the country at 1,000 miles an hour, I'd land in LA thee hours later, just as the sun was setting -- the same position in the sky as when I left DC. Travel a bit faster than 1,000 mph,and I arrive at the west coast in under three hours -- the sun will actually be higher in the sky when I land in LaLa land. Kapish? Any questions, just fire away. paf```
 nronronronro-ga rated this answer: ```pafalafa, If you think my questions are strange and interesting, you should see my face ! heh heh heh Excellent and straightforward answer. Thank you. ron```

 ```Jerry Glasser and Ted Ross once took off after sunset in an SR-71. They flew a westerly course, and, since the day/night terminator travels at only about a thousand miles per hour at the equator, and since the supersonic spy plane travels much faster than that, they watched the sun "rise" in the west. After a while, they turned south, and the sun set again. Later in the mission, they headed west again, and observed the sun slowly rise over the horizon. Glasser and Ross may be the only people to see the sun rise in the west. Twice in one "day." http://www-psao.grc.nasa.gov/asao.quiz/october.97.html```
 ```Thanks, pinkfreud. I appreciate your comments ! ron```
 ```Keep in mind that the tangent speed of Earth's rotation varies with latitude. It's roughly 1,000m/h at the equator, but drops steadily and approaches zero as one approaches either of the poles. So accordingly, the ground speed of an aircraft keeping the Sun balanced at a fixed angular separation will also vary in the same way. Near the south pole, for example, you'd be able to crawl fast enough to keep the Sun at a fixed angular separation from you. -Mark Martin```
 ```Thanks, Mark. Very elegant exposition. Quod erat demonstrandum! ron```