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Earth-Moon distance, length of day and obliquity for CTest samples

Source: R/ctest_earthmoon.R
ctest_earthmoon.Rd

Each sampled precession constant is converted with precession_frequency() (Farhat et al. 2022, eq. A.7), either by inverting the AstroGeo22 curve or by assuming Earth-Moon angular-momentum conservation.

Usage

ctest_earthmoon(
  x,
  age_ma = NULL,
  method = c("angular_momentum", "astrogeo22"),
  obliquity_deg = NULL,
  probs = c(0.025, 0.5, 0.975),
  data_dir = NULL
)

Arguments

x

Precession constants to convert: a ctest object from ctest (its samples of k are used) or a numeric vector of precession constants given as periods in years. Required, no default.

age_ma

Age of the record in Ma (numeric), used for the obliquity of the angular-momentum inversion (when obliquity_deg is NULL) and for the comparison with AstroGeo22 at that age (model_at_age). NULL uses the mean of the age range of a ctest object, or no age for a numeric vector (then the present-day obliquity is used and no comparison is made). Default=NULL.

method

How the precession constant is converted to Earth-Moon distance and length of day (character): "angular_momentum" assumes conservation of the Earth-Moon angular momentum at the given obliquity; "astrogeo22" reads distance, length of day, obliquity and the equivalent model age off the AstroGeo22 curve (last 1000 Myr). Default=c("angular_momentum", "astrogeo22"), i.e. "angular_momentum".

obliquity_deg

Obliquity in degrees (numeric) used in the angular-momentum inversion; NULL takes the AstroGeo22 value at age_ma (or the present-day 23.25 degrees when no age is known). Ignored by method="astrogeo22". Default=NULL.

probs

Probabilities of the quantiles reported in the summary next to the mean (numeric vector, values between 0 and 1). Default=c(0.025, 0.5, 0.975).

data_dir

Folder that contains the astronomical data table AstroGeo22.txt (character path); NULL uses the table installed with the package (or the folder set with options(cocoR.data = ...)). Default=NULL.

Value

list with `summary`, `samples`, `method`, `age_ma` and, when an age is known, `model_at_age`