Wednesday, January 9, 2013

Wednesday Search Challenge (1/9/13): When will the sun hit the beach?

Ah.. the life of a research scientist!  I’m attending a conference on Maui this week.  (And no, I really haven’t been to the beach… yet.  So far, I’ve been indoors for 3 days straight.) 

I DO hope to get to the beach tomorrow morning.  However, I also don’t want to get a sunburn (or miss any of the great talks that start early in the morning).  

Since I’m an early riser, I’m planning on going to the beach at the crack of dawn and hang out there until the sun hits the beach.  Then, the moment the sunlight strikes those golden sands, I'll head back inside and get to work, giving me a few idyllic moments of walking along the beach.  

I think this is a non-trivial problem to figure out.  But I worked it, and was surprised by the answer.  I suspect you will be too.  

Hint:  Where is Wailea Beach?  Why is that location important? 

And it leads to today’s sensemaking problem to work out..

     Question:  If I’m at the beach at 20.68183, -156.44322 (Wailea Beach Park), 
           what time will the sunlight hit the beach sand there tomorrow morning,
           January 10th, 2013? 

Be sure to tell us how long it took you to figure this out, and HOW you worked it out!! 

Search on!


  1. 7:05am

    Found site...
    established it is in postal code 96753.
    About 2 minutes.

  2. I've had a similar problem recently - trying to figure out when the sun sets and when daylight will be gone so I know when it's safe to run outdoors.

    Because of this, I know that the terms that were on the site that I used were "dawn" and "dusk", (the times when light appears and disappears from the sky) so I did a search that was [dawn dusk times] because I figured there had to be a map/calculator things out there for it.

    I found one that fit my idea perfectly called "SunCalc", where you input a location, and it will tell you the times for dawn, sunrise, solar noon, sunset, and dusk. Putting in your coords, I found that if you are at the beach at 6:41 am, there will be light, and 7:05 am is when the sun begins to come up.

    That's only 24 minutes of beach time, so as a redhead (I burn REALLY EASILY) I would say you could stay another 20 minutes or so without sunscreen before risking sunburn - that's about how long I can stay out, and chances are you aren't paler than I am. ;)

    Total time: about 2 minutes (since I had a headstart on knowing what I was looking for),-156.4429,16/2013.01.09/10:40

    1. interesting use of terms - I had just put [sun rise Wailea-Makena, HI] in my browser's search window (google) and had come up with this NOAA site and sunrise time of 7:04 for TH, 1/10/13... (also found the U.S. Naval Observatory site - it used the term "civil twilight", but I had ignored that)... but it had seemed too easy and thought Dr.D.R. had some other angle up his Hawaiian board shorts and I gave up after about 20 minutes of searching for alternatives.
      Then when I saw your comment & link to the SunCalc app, I looked at it (with corrected date) and see it shows dawn @ 9:41 & sunrise @ 10:05 which would create the "surprise factor" Dan alluded to, but it seems awfully late - maybe due to the volcano factor GRayR & others mentioned? - at any rate, I'm in the dark* until tomorrow - thanks for shedding some sunlight on "dawn" & "dusk" types.
      *and now I see there are even more types of twilight & ranges... referee Dan please...
      08:47—09:14 — astronomical twilight
      09:14—09:41 — nautical twilight
      09:41—10:05 — civil twilight
      10:05—10:08 — sunrise

  3. Maybe I answered too quickly. Sunlight hits the beach during twilight and 'civil twilight' may be the term you are looking for. Civil twilight begins at 6:41am while sunrise is at about 7:04am according to
    About 10 minutes.

  4. I found a sunrise calculator that gave me 7:04 as the time for sunrise at the location you specified. It took about 5 minutes to find one that worked for anywhere, not just major cities. Some weather programs like Living Earth have inbuilt sunrise/sunset calculators but that gives 7:06.

    One problem with sunrise calculation is that the definition of sunrise differs, in the USA I believe that it is as you wanted i.e. that the sun's light reaches the beach. In Sweden however it is the time when the centre of the sun is over the horizon.

  5. So, about 90 minutes, and not 100% sure, but best guess is ~7:06AM local time. Perhaps a few minutes later - I'm not entirely sure on the math for high the sun has to be over the horizon to appear to hit the beach.

    Beach is at sea level, assuming no obstructions to the sunlight. Apparent sunrise (NOAA calculator) is 7:04, and sun actually reaches 0 elevation ~7:05:40-something. So padding a few extra seconds on, I figure right around 7:06. But it could be a few minutes later.

    Spent a lot of time chasing wrong leads. Realized much later that if I'd started off looking in solar panel resources instead of astronomy resources, I would've had an easier time of things.

  6. When I searched the location and sunrise, it came right up in Google as 7:04 am. I confirmed it by putting the location in accuweather and it gave. The same time. Took me just a couple of minutes so I was concerned that this was just too easy and that maybe I am wrong.

  7. The time of sunrise at Wailea Beach Park, or to be more exact, when will the sunlight hit the sand? (I lived in Hawaii for years and I remember when we went to this beach and there was nothing there but beach.)

    Well first this beach faces west, and there is that big pile of volcano Haleakala right behind it. But looking at street view it looks like the trees and bushes and buildings will block the sunrise somewhat.

    Looking up a standard sunrise sunset table for that location at
    I get a time of 7:04 AM. But what time will the sun actually hit the beach. For that we need to know where in the sky the sun will come up, and how high does it need to be for the first rays of the sun to hit that beach.

    Looking up the Solar position calculator at NOAA using that lat. and long, and for 7:04 AM tomorrow morning.
    I get a solar declination of -21.8
    (solar declination - the declination of the sun. The solar declination varies from -23.44° at the (northern hemisphere) winter solstice, through 0° at the vernal equinox, to +23.44° at the summer solstice. The variation in solar declination is the astronomical description of the sun going south (in the northern hemisphere) for the winter.)

    A solar azimuth of 118.9
    And a solar elevation of 10.5
    (azimuth and elevation - an angular coordinate system for locating positions in the sky. Azimuth is measured clockwise from true north to the point on the horizon directly below the object. Elevation is measured vertically from that point on the horizon up to the object. If you know the azimuth of a constellation is 135° from north, and the elevation is 30°, you can look toward the southeast, about a third of the way up from the horizon to locate that constellation. Because our planet rotates, azimuth and elevation numbers for stars and planets are constantly changing with time and with the observer's location on earth.)
    What is this telling me?
    Without knowing the exact height of the trees, bushes, and buildings, it is difficult to exactly determine exactly when the sun hits the beach. Answer, not available from given inputs. A guess is 7:18 AM
    I know something is wrong or I am not finding something. I am 0 for 3 on the last searches. I want to see a picture of the sun on the beach with your chronograph.
    And have fun, this is a beautiful place.

  8. First of all I checked the beach orientation using google maps.
    Wallea Beach Heads to the west, so the sun rises at your back when you’re looking to the sea.
    Hawaii has mountains so, if there’s any peak at the same latitude and is high enough, it can modify the sunlight hit the beach sand because of it shadow.
    There is one and is high.
    Again with google maps I find the name: Haleakala Crater
    Google search tell me that the elevation is about 3000 meters (3km)
    Well, how far is the peak from the beach?
    With google maps I take an aproximation: 20km
    So the sun will hit the beach when the elevation from the horizont is about arcSin(3/20) = 8.6 degrees ( using google calculator ;-)
    So, the easiest way (the first in my head) is to calculate the sunrise at
    lat:20.68, long:-156.44 - 8.6 deg instead of long:-156.44
    OK, but what’s the time?
    With google search I searched [sunrise lat long]
    4th result: Custom Location Entry for Sunrise Sunset Calendar
    I prefered this result because of the custom word (remember, I tryn to find sunrise time in the middle of the ocean! 8 deg away the beach)
    I filled up the form and get a calendar: day 10 Sunrise: 17:39 GMT
    (the actual result for the beach lat long is 17:04 GMT, so according this, the volcano shadows last about half an hour on the beach)
    Well, the last step, whatś the local time when the sunlight hit the beach 17:39 GMT - 10 to get HST (Google search for [hst time]:

    So the answer is.... 7:39am Maui local time

    Total time, about 15 minutes.

  9. Opps, angle is arcTan(0.15) = 8.5 degrees

  10. Took me 2 minutes...

    search term: sundown OR sunset at specific location
    --> brought me to wikipedia article, heading to external links (while I knew that there are always good external links to specific sites or calculators)
    --> lead me to,-156.4431,17/2013.01.10/21:42 where I entered Wailea Beach Park - Received the following data:

    00:00—16:47 — night
    16:47—17:14 — astronomical twilight
    17:14—17:41 — nautical twilight
    17:41—18:05 — civil twilight
    18:05—18:08 — sunrise
    18:08—05:01 — daylight
    05:01—05:03 — sunset
    05:03—05:27 — civil twilight
    05:27—05:54 — nautical twilight
    05:54—06:21 — astronomical twilight
    06:21—00:00 — night

    But while I read the other comments I'm a little bit confused if it is the right answer ;)

  11. How about 11:04 using your coordinates and the calculator at

  12. I checked Maps to make sure the beach had not moved since I was there. The sunset obfuscation was great. I knew you were not after sunrise time. I have spent was too long on this and cannot figure out how to find out when sunshine gets over the mountain shadow. - Hours burned

    Except for an easy solution: I phone the front desk and ask them. - 30 seconds


  13. If you want to get some details on where and when the sun will be in the sky on any given day I would grab a copy of The Photographer's Ephemeris from this will give a sunrise of 7:04 AM at that location. It factors in the location of the sun in the sky and shadowing by the local terrain.

  14. Hi Daniel! I follow the Lifehacker page and I found your post there. I just want to say hi directly from the conference (keynote in progress) :) It was so funny to see the post and the picture, while being at the same place :)

  15. the rays of the sun will hit the sand on Wailea Beach at approx 7:31am Jan 10th, 2013 in the Hawaii-Aleutian timezone

    Google Earth has this neat little feature to view the sunrise/sunset (or sun position at anytime)...

    It took approx. 4 minutes to load the program, orient the view and start the timer

  16. Around 7:44 am. I first located Wailea beach on googlemaps, then searched for the sunrise time at the latitude, longitude of Wailea-Makena ( for example) : 7:04am. But I can see big mountains east the the beach that must hide the rising sun and delay its apparition on the beach. There's even an observatory on that mountain (Haleakala Observatories on maps). [Haleakala Observatories] gave a 10,000ft (3 km) altitude and the mesure tool in maps gave about 17 km (straight line) between the beach and the top of the mountain. A little maths gave an angle of 0,1747 rd the earth must rotate (or the apparent movement of the sun) before the sun is visible on the beach. Maths again : 2*pi rd in 24hrs -> 0,1746 rd in about 40'. That must be added to 7:04' and makes 07:44am. 15' search and maths.

  17. Sunrise in Maui is at 7:04. It only took two clicks.
    Enjoy the sunrise tomorrow!

  18. 1) Entered the co-ordinates in google maps.
    2) Was convinced there would be an eclipse at that time (disappointed).
    3) Noticed that the map was looking empty to the east of the location. Googled a bit and found a mountain (Haleakala)
    4) Got the height (3km) from the wiki page and confirmed using some geographic maps (
    5) Got the distance (~19km) using the ruler in google maps.
    6) Angle of elevation is invtan(3/19) ~ 9 degrees
    7) Earth rotates at 15 degrees an hour so time from normal sunset is 36 minutes.
    8) Here comes the tricky part, earths atmosphere actually bends the light of the sun at different angles at different elevations of the sun.
    9) found a 34 arcminute deviation at horizon and approx 6 arcminute at 9 degrees elevation (from the wiki page for atmospheric refraction). Which gives a 28 arcminute (0.46 degrees) error from our actual calculation.
    10) This gives an extra 1.86 minute addition to our 36 minutes.
    11) Local sunrise at Wailea is 7:05 am. Therefore the beach will get first light at ~7:43 am. You have about 38 minutes from sunrise.

    Took about 20 minutes for fact checking etc.

  19. I suspected that geography might play a role in this. I am also assuming that you want the time when sunlight directly shines on the beach rather than it still being in shadow. There's a lot of answers here that make me second guess my answer, but what I did was open up Google earth, paste in the coordinates, and zoom down to first person view. I then enabled the sun and adjusted the time slider to see when the sun would first crest the volcano on that day. The fuzziness of the sun and discrete slider steps made it a little difficult to figure out exactly. My answer is 9:30 at the earliest.

  20. I used Google Earth's sun layer to step through light hitting the beach. It looks like even though sunrise is 7:04 the beach does not get light until 9:07 for a brief time then about 10:50.
    About 30 min

  21. Search term: Wailea Beach sunrise time
    Found this page (second hit):
    Entered Wailea

    Sunrise: 7:04
    Sunset: 18:02

    Took me about 5 minutes.

  22. 6:02 PM
    Sunset in Wailea-Makena, HI, USA

    search: Wailea Beach
    Click on GoogleMaps right on the top right to find out that is in Hawaii

    Type on sunset: wailea, hawaii

  23. Did a search for "daybreak calculator", and inserted the coordinates in
    Initially thought you meant sunrise (sorry, I'm not too used to twilight-ish English) and got 7:03am, then after seeing Kozel's error, had to go google twilight again, and I came up with 06:39am.

    So with a little of Kozel's help, and a little under 10 minutes, I hope I'm right

  24. Well if you take the question very literally, meaning date and location, the sun will not hit the beach this morning. According to Weather Underground it is supposed to rain today on Wailea Beach.

    One search - first hit. 10 seconds.

  25. 07:06:06 am HST = 05:06:06 pm UTC

    By finding a City nearby and asking Wolfram Alfa ;-)

  26. Plenty of time suggestions, but what makes it difficult to speculate, is that the beach faces west, and so the sun will be coming from east to west, and will be rising above whatever land is to the east of the beach. I see some sort of a ridge, a plethora of hotels in the way, etc. I suspect the photo pictured above is of the sunset...

  27. Worked on this with my colleague Anne. We knew from Dan's email that he wasn't just looking for the sunrise time at this location. So we started out by doing a search in google maps for the location. We noticed that it was on the far western side of the island and that there were mountains that could impede the sun hitting the beach. We saw that we could filter by sunlight in Google Earth and was able to see that the beach wasn't getting sunlight at the official sunrise time of 7:04. From Google Earth is appeared like sunlight came closer to 8:30 am. That may have just been us not knowing how to use this feature on GoogleEarth effectively. I am not sure we would be able to have figured this out using the math! So if we wanted a really precise answer we probably would have called the front desk or the reference librarian at the local library!

  28. Did you know your Garmin GPS device includes a sunrise and sunset time for your current position? When takimg groups hiking I would bore them with this and other data that in fact could save their life. Another fun fact is if you know your altitude and can monitor your barometric pressure/trends you can determine if the weather is going to get worse and how long before it will hit you.

  29. Entered coordinates plus -10 UTC and DST at
    I may have it wrong based on others but it calculated Apparent Sunrise as 8:04am

  30. re-entered because table asks for local time which based on the fact I had Indicated -10 for time zone I think Hawaii time should be identified but by putting in Hawaii time I now get 11:13 for Jan 11th. So now I am confused.