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Todd Rowland

Moon Phases in Wolfram|Alpha

July 14, 2011 —
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On a moonlit stroll, a young man points to the cloudless sky and says, “Look—a full moon!”

His date is not impressed. “Technically,” she replies, “the Moon’s not full until 2pm, when its ecliptic longitude is opposite to that of the Sun.”

Hoping to save his pride, he replies, “But the Moon looks completely illuminated.”

“It’s never one hundred percent illuminated,” his date says, unfazed. She’s a tough cookie. “Oh, and on this side of the world it’ll be a corn moon.”

Pretending to check his watch, the young man gets confused. He remembers his science teacher explaining that the Moon reflects sunlight and that it is full when it is on the other side of the Earth from the sun, but the nighttime half of the Earth is on the opposite side of the Sun, so how could that be 2pm? Did the newspaper say it would be a full moon tonight, or did it say tomorrow night? And what’s a corn moon?

There’s only one thing he can do: look it up on Wolfram|Alpha!

One of the latest features added to Wolfram|Alpha is more coverage of full moons and other Moon phases. Back when people got their information from only a local newspaper, it was relatively simple to say that one night or another would be a full moon, because for a specific location, the time of a full moon would be closest to midnight on that day. But now it is easy to get your information from a newspaper that is far away, so its date can be off by a day. Of course, Wolfram|Alpha detects your location, so it is able to predict the date of the next full moon in your area, and the “Precise time” button reveals the exact time the full moon will take place.

corn moon 2012

Remember that because of time zone differences, there is always part of the world that is on a different day. And that affects labels like “corn moon”, which is the first full moon in September. The beginning and ending dates of September depend on the time zone, and sometimes the full moon is close to this boundary. The next ambiguous corn moon will be in 2012.

While moon phases are hardly the most complicated thing Wolfram|Alpha deals with, these examples show how it turns complicated and confusing queries into answers that are easy to understand.

Let me leave you with a word of advice. The next time you are on a midnight stroll, you might want to avoid looking like a show-off and instead explain that you found it out from Wolfram|Alpha.


I was mildly happy to see this entry – Todd thanks so much. The use of WA to help with research concerning the phases of the moon is hugely important particularly for indigenous peoples like mine.

I am a native of New Zealand, a Maori, and have been researching our traditional use of the maramataka (lunar calendar). A lunar calendar cannot be synchronised with the ‘Western’ Georgian calendar currently used for every day business and commerce.
In pre-European times Maori used a lunar calendar. Being colonised changed the way our people behaved towards the use of their maramataka – often to our people’s detriment and well being.

The tribal use of the maramataka ishighly democratic – each tribe having the means to determine when the phase occurred, such as a full moon, new moon etc. These lunar events were determined locally, culturally and socially – certainly not mathematically. However, a tribes’ use of lunar phase occurrence was not in isolation to other natural lunar events such as tidal changes. Importantly the appearance of key stars was instrumental – paramount.

For instance Whanui (Vega) rises in early March and signals the time to harvest (late harvest). Rehua (Antares) rises in December which is the time for early harvest and late planting. Te Puanga (Rigel) & Matariki (Pleiades) both rise in June which sets the New Year according to Maori. Tribes utilised these co-joint stellar and lunar occurrences to synchronise their tribal events, activities and calendar.

Currently in New Zealand many research our lunar maramataka using historically records written by European anthropologists and historians in the 1800s that were often and invariably misinterpreted or just failed to record key ideas and activities – particularly around the native astronomy and lunar calendar. Many still fail to incorporate knowledge held privately by tribes even today.

The maramataka was hugely important for every day activity – both in business and commerce for sustenance, health and wellbeing. Our tribe used the maramataka into the 1970s to collect harvest and collect food – especially kaimoana (fish, shell fish etc). Some tribes still do sparingly. Many fish specifies are only caught at specific times according to the lunar and annual cycle. On fishing occasions our whole tribe (about 20-30 adults plus us children) would all go along all undertaken according to the maramataka. These fishing excursions were great fun in the 1950s & 60s. As a young child I would often wonder why we went in the early evening – often in total darkness on moonless nights.

Why didn’t we go on a full moon I would think? We had to use kerosene lanterns (we could not afford torches with batteries back then).

It was not until I was older my father explained the intricacies of the maramataka. Fishing and planting by the lunar calendar was an every day occurrence & it certainly wasn’t unusual. I am sure any indigenous people all over the world even today still use a lunar calendar for harvesting and gathering of food – Maori are certainly not unique by any stretch of the imagination on this aspect.

However, conducting business and commerce by the maramataka is less obvious. Our people certainly conducted business and commerce using a lunar calendar. This aspect was well documented in the late 1800s when Europeans built natives schools that would routinely be closed because all the native children were taken out of the schools by their tribes to help with planting and harvesting – which was all performed according to the tribal maramataka.
My personal research is now trying to prove the relationship between past tribal business activity and the maramataka – more specifically lunar phases and which phase. This is where WA might be able to help.

Now here is the issue. During the 1950s – 1970s my tribe met to arrange meetings with other tribes. The planning for these important tribal meetings was meticulous – our people had many meetings just to develop a strategy before hand (I’m not sure they saw it as strategic back then – but it was). Issues discussed and planned were: who is to be the lead speaker, what issues will be spoken about, what issues will not be talked about. I have the documented from copies of minutes recording these events with dates and times.

I am almost convinced the idea of holding the tribal meeting (business) also included the lunar ‘timing’ of the tribal occasion.

Therefore, how do I ask WA what lunar phase for a specific date, year, and importantly in New Zealand?

Please note: I do use WA to provide and verify the times of when a specific star rises.
I hope this long winded explanation didn’t bore the masses.
Thanks again. Henere Tumapuhia, Wellington, New Zealand

Posted by Henere Tumapuhia July 24, 2011 at 7:23 pm

Kia ora Todd, thanks heaps – I realy appreciate your response. Take care.

Posted by Henere Tumapuhia July 27, 2011 at 5:33 pm

Kia ora Todd, thanks heaps – appreciated your response. Will put this into practise. Take care.

Posted by HenereTumapuhia July 28, 2011 at 4:03 am

Until recently, the U.S. Naval Observatory website would accept as input the latitude, longitude, and date for any location on Earth, and generate for you a table of sun and moon azimuth and elevation on a minute-by-minute basis. The revamped website, however, no longer provides this capability. Pity. Would be nice were Wolfram|Alpha, vis-`a-vis this post, to fill this newly created gap.

Posted by Popeye the Sailor Man August 1, 2011 at 10:43 am