MoonPhase
MoonPhaseDate
FindAstroEvent
TideData

Astronomy
Time-Related Computation

Variations in Day Length

Study how the observed length of a day differs from 24 hours

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The precise length of a day on Earth varies over time due to a variety of effects. These range from tidal interactions to internal mass redistribution between the Earth's crust, mantle, cryosphere, atmosphere and ocean. In this example, we use

GeoOrientationData

to get data on the changing length of the day.

Get day duration values for all days in 2022. The "DayDurationExcess" property gives us the signed difference between the observed day length and a nominal 24 hours:

In[1]:=

ts=GeoOrientationData[DateInterval[{{2022,1,1},{2022,12,31}}],"DayDurationExcess","Around"]

Out[1]=

TimeSeries

Time: 31 Dec 2021 to 31 Dec 2022
Data points: 366



Convert the resulting

TimeSeries

into a

Tabular

object:

In[2]:=

tab=Tabular[ts]

Out[2]=

Plot the day duration excess over the year 2022. The error bars are too small to appear:

In[3]:=

DateListPlot[Normal@tab]

Out[3]=

Next let's find the longest and shortest days of 2022.

November 4, 2022 was more than 1 millisecond longer than 24 hours:

In[4]:=

MaximalBy[tab,"Value"]

Out[4]=

June 29, 2022 was more than 1.5 milliseconds shorter than 24 hours:

In[5]:=

MinimalBy[tab,"Value"]

Out[5]=

By aggregating over the year, we can see the total excess or deficit.

By the end of 2022 we had lost about 0.1 seconds:

In[6]:=

atab=TransformColumns[tab,"Value"Function[ColumnwiseThread[Accumulate[#Value]]]]

Out[6]=

Plot the total excess day length over the course of the full year:

In[7]:=

DateListPlot[Normal@atab]

Out[7]=

Related Symbols

MoonPhase
MoonPhaseDate
FindAstroEvent
TideData

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Contributed by: Wolfram Staff

Wolfram Language Example Repository

Variations in Day Length

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