# How many sunrises in 24 hours?April 19, 2009 12:36 PM   Subscribe

How many sunrises could you see in 24 hours?

Lets assume for the purposes of this question you have access to a fast jet that can land wherever you want, how many do you think it is theoretically possible to see within a twenty four hour period?
posted by muthecow to Science & Nature (22 answers total) 1 user marked this as a favorite

If the jet was fast enough and had sufficient fuel capacity to fly around the world in 24 hours, couldn't you see a continuous sunrise?
posted by carmicha at 12:38 PM on April 19, 2009 [1 favorite]

I think this depends on the speed of your jet and what constitutes seeing a sunrise, e.g. sitting and watching the sun rise for 30 minutes, or just glancing at the sun as it's rising. If your jet was really fast and seeing the sun for a split second as it's rising counts as seeing a sunrise, then you could see arbitrarily many sunrises in a 24 hour period.
posted by pravit at 12:40 PM on April 19, 2009

Factor in cloud cover. You're not likely to find clear skies everywhere around the world.
posted by hungrysquirrels at 12:41 PM on April 19, 2009

Building on what carmicha suggests, I think the answer might be 'all of them.'
posted by box at 12:43 PM on April 19, 2009 [1 favorite]

Yeah I was going for watching a complete sunrise. Sitting down somewhere where there is 0% sun and watching until there is 100% sun, and then flying to the nearest place where there is 0% and repeating the process.
posted by muthecow at 12:44 PM on April 19, 2009

A sunrise "travels" around the equator at about 1,000 mph, and at a slower speed at all other latitudes. This NASA page explains the math.

If you had access to a jet that could fly at least Mach 1.5 and with an adequate fuel supply, you could see a constant sunrise by flying west at that speed for 24 hours, although you'd have to look behind you to see it. For reference, the Concorde could fly up to mach 2.2.
posted by thewittyname at 12:50 PM on April 19, 2009 [2 favorites]

Since the planet is spinning on its axis at over 1000mph (at the equator), you would need a plane faster than anything we have to make this happen. I suppose you could fly against the rotation and sort of meet the sun on the other side, but even then... I remember flying to/from Germany many years ago, and neither of those flights involved more than one daylight appearance, and both were a major portion of a 24-hour period.

I love the concept -- it is SO Little Prince. I just can't see it being possible.
posted by hippybear at 12:54 PM on April 19, 2009

This question is much more complex than it might appear. It depends upon, for example, your latitude and the time of year.

With that said, the shortest amount of time that a sunrise can take, from 0% sun to 100% sun, is 128 seconds (which is at the equator during an equinox).

So, an upper limit to the number of full sunrises you could see in one day is (24 hours / 128 seconds), which is 675.

That is, if you were at the equator on a solstice, and you could instantaneously teleport, you could see 675 sunrises in one 24 hour period.

Anywhere else, or any other date, or any slower method of transportation, and the answer is something less than 675.
posted by Flunkie at 12:58 PM on April 19, 2009 [6 favorites]

That is, if you were at the equator on a solstice
I mean "... on an equinox". Solstices are the times of the slowest sunrises; equinoxes the fastest.
posted by Flunkie at 12:59 PM on April 19, 2009

With that said, the shortest amount of time that a sunrise can take, from 0% sun to 100% sun, is 128 seconds.

Well, no. You realize that what you are really measuring is the time it takes the earth to turn until you can see the entire sun. You can speed that up with a jet, then turn the jet around until you can't see the sun, then turn around and do it again. So flying a fast jet in circles will do it.
posted by weapons-grade pandemonium at 1:04 PM on April 19, 2009 [2 favorites]

Well, no. You realize that what you are really measuring is the time it takes the earth to turn until you can see the entire sun. You can speed that up with a jet, then turn the jet around until you can't see the sun, then turn around and do it again. So flying a fast jet in circles will do it.
The poster specified that you had to sit down someplace and stay there, watching from zero percent sun to 100 percent sun, and only then could you move to the next location.
posted by Flunkie at 1:06 PM on April 19, 2009

No. The poster did not say that.
posted by weapons-grade pandemonium at 1:10 PM on April 19, 2009

A very powerful pogo stick would do it, also.
posted by weapons-grade pandemonium at 1:11 PM on April 19, 2009

No. The poster did not say that.
Then explain to me what this means, please.
posted by Flunkie at 1:11 PM on April 19, 2009

Not the jet-oriented answer you're looking for but I think the best way to see many, many sunrises is to orbit around this planet.
posted by Baud at 1:11 PM on April 19, 2009

There's also latitude to consider. Flying around nearer the poles would give you less ground to cover and might give you an advantage.

Let's say you wanted to see 24 sunsets - one every hour for 24 hours. And let's say your jet can move you at an average of 500 mph (faster than most commercial jets, but easier to round). Let's say you stop to look at the sunrise once and refuel once an hour, and those stops last 12 minutes (again, easier for rounding). You travel 400 miles in each hour, though you're traveling AT 500 mph when you're flying. So, 9,600 miles in total. To do all 24 stops, you'd need to be flying above a slice of the Earth that was a little over 3,000 miles in diameter. The planet's about 8,000 miles in diameter at the equator, so you'd have to be up/down a good ways towards one of the poles. You wouldn't fly at a constant latitude relative to the pole, because the planet's tilted at 23 degrees and that axis tilts towards the sun at different angles over the course of the year. You could stop more often to see more sunrises, with shorter stops or higher velocity. If you could go much faster, you fly closer to the equator.

Of course, the real problem is that any such slice of the Earth's surface isn't going to have airports at evenly spaced 400 mile intervals, and any such slice is probably going to include stretches of hundreds or thousands of miles over an ocean. Then again, maybe you could do it more easily if you were right by the South Pole on an Equinox.

[Trig wizards of AskMe: am I leaving anything out there?]
posted by el_lupino at 1:20 PM on April 19, 2009

There's also latitude to consider. Flying around nearer the poles would give you less ground to cover and might give you an advantage.
The question being a theoretical limit, the speed of the jet can be considered to be the speed of light, and the amount of ground you have to cover is thus essentially irrelevant.

The limiting factor, therefore, is the duration of a sunrise, not the distance you have to move. This is (on any given day) always fastest at the equator. Therefore, higher latitudes are worse.

I stand by my answer: 675.
posted by Flunkie at 1:23 PM on April 19, 2009 [1 favorite]

Randall Munroe (of xkcd fame) recently explored a similar issue in his blag.
posted by funkiwan at 2:32 PM on April 19, 2009

[few comments removed - poster is not anonymous. feel free to contact them.
posted by jessamyn at 2:34 PM on April 19, 2009

You'd have to bring the number down more unless 'wherever you want' includes 'in the middle of the ocean', because of the need to find land to land on. I mean, unless you're dealing in teleporting or jets that go the speed of light, in which case, why not just declare the number to be a brazilian?
posted by jacquilynne at 4:30 PM on April 19, 2009

That is, if you were at the equator on a solstice, and you could instantaneously teleport, you could see 675 sunrises in one 24 hour period.

I remember the first time I encountered this idea was in Larry Niven's first Ringworld book, I think it was, when (given that teleportation technology with limited range has been invented) Louis Wu chases sunrises around the world on his birthday.
posted by stavrosthewonderchicken at 6:41 PM on April 19, 2009

You might be interested in the Concorde flight on June 30, 1973 where observers were able to view totality for over 74 minutes
posted by Redmond Cooper at 12:45 AM on April 20, 2009

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