//! Physical and astronomical constants used across the workspace.
//!
//! All values are expressed in SI units unless the name or doc comment
//! states otherwise. Values that are fixed by definition are given exactly;
//! measured values carry the number of significant digits justified by the
//! public source.
//!
//! Sources:
//!
//! - SI defining constants: BIPM, *The International System of Units (SI)*,
//!   9th edition, 2019.
//! - CODATA 2018 recommended values: E. Tiesinga et al., *CODATA
//!   recommended values of the fundamental physical constants: 2018*,
//!   Rev. Mod. Phys. 93, 025010, 2021.
//! - Earth gravitational parameter and equatorial radius: WGS 84,
//!   NIMA TR8350.2, 2000.
//! - Astronomical unit: IAU 2012 Resolution B2.
//!
//! Where a value is defined exactly by a standard, the doc comment says so,
//! because several derived quantities depend on the exact value rather than
//! the rounded printed one.
//!
//! 当某个数值由标准精确定义时，文档注释会指出这一点，因为若干导出量依赖精确值
//! 而非取整后的打印值。

/// Speed of light in vacuum, in meters per second.
///
/// Exact by definition of the metre in the SI.
///
/// 真空光速，单位为米每秒。
///
/// 由 SI 对米的定义精确确定。
pub const SPEED_OF_LIGHT: f64 = 299_792_458.0;

/// Newtonian constant of gravitation, in cubic meters per kilogram per
/// second squared.
///
/// CODATA 2018 value with its standard uncertainty of
/// `1.5e-11 m^3 kg^-1 s^-2`.
///
/// 牛顿万有引力常数，单位为立方米每千克每二次方秒。
///
/// CODATA 2018 推荐值，标准不确定度为 `1.5e-11 m^3 kg^-1 s^-2`。
pub const GRAVITATIONAL_CONSTANT: f64 = 6.674_30e-11;

/// Boltzmann constant, in joules per kelvin.
///
/// Exact by definition of the kelvin in the SI.
///
/// 玻尔兹曼常量，单位为焦耳每开尔文。
///
/// 由 SI 对开尔文的定义精确确定。
pub const BOLTZMANN: f64 = 1.380_649e-23;

/// Planck constant, in joule seconds.
///
/// Exact by definition of the kilogram in the SI.
///
/// 普朗克常量，单位为焦耳秒。
///
/// 由 SI 对千克的定义精确确定。
pub const PLANCK: f64 = 6.626_070_15e-34;

/// Elementary charge, in coulombs.
///
/// Exact by definition of the ampere in the SI.
///
///  elementary charge，单位为库仑。
///
/// 由 SI 对安培的定义精确确定。
pub const ELEMENTARY_CHARGE: f64 = 1.602_176_634e-19;

/// Astronomical unit, in meters.
///
/// Exact by IAU 2012 Resolution B2.
///
/// 天文单位，单位为米。
///
/// 由 IAU 2012 Resolution B2 精确确定。
pub const ASTRONOMICAL_UNIT: f64 = 149_597_870_700.0;

/// Standard gravity, in meters per second squared.
///
/// Exact by definition of the standard atmosphere.
///
/// 标准重力加速度，单位为米每二次方秒。
///
/// 由标准大气的定义精确确定。
pub const STANDARD_GRAVITY: f64 = 9.806_65;

/// One minute, in seconds.
///
/// 一分钟，单位为秒。
pub const MINUTE: f64 = 60.0;

/// One hour, in seconds.
///
/// 一小时，单位为秒。
pub const HOUR: f64 = 3_600.0;

/// One day of 24 hours, in seconds.
///
/// This is the SI day. It is not the mean solar day, which is slightly
/// longer, and not the Julian day of 86 400 seconds used in Julian date
/// arithmetic, which is identical to this value.
///
/// 一个 24 小时的日，单位为秒。
///
/// 这是 SI 日。它不是略长的平均太阳日，也不是儒略日运算中使用的 86 400 秒
/// 儒略日，后者与本值相同。
pub const DAY: f64 = 86_400.0;

/// One Julian year of 365.25 days, in seconds.
///
/// Exact by definition of the Julian year.
///
/// 一个 365.25 日的儒略年，单位为秒。
///
/// 由儒略年的定义精确确定。
pub const JULIAN_YEAR: f64 = 31_557_600.0;

/// One Julian century of 36 525 days, in seconds.
///
/// Exact by definition of the Julian year, used by precession and secular
/// rate expressions quoted per Julian century.
///
/// 一个 36 525 日的儒略世纪，单位为秒。
///
/// 由儒略年的定义精确确定；岁差与长期变化率表达式按儒略世纪引用时使用它。
pub const JULIAN_CENTURY: f64 = 3_155_760_000.0;

/// Julian date of the Unix epoch, 1970-01-01T00:00:00 UTC.
///
/// This is `2 440 587.5` in the Julian date system.
///
/// Unix 历元的儒略日，1970-01-01T00:00:00 UTC。
///
/// 在儒略日体系中该值为 `2 440 587.5`。
pub const JULIAN_DATE_UNIX_EPOCH: f64 = 2_440_587.5;

/// Julian date of the J2000.0 epoch, 2000-01-01T12:00:00 TT.
///
/// Exact by definition of the J2000.0 epoch.
///
/// J2000.0 历元的儒略日，2000-01-01T12:00:00 TT。
///
/// 由 J2000.0 历元的定义精确确定。
pub const JULIAN_DATE_J2000: f64 = 2_451_545.0;

/// The number of seconds between the J2000.0 epoch and the Unix epoch.
///
/// Derived from [`JULIAN_DATE_J2000`] and [`JULIAN_DATE_UNIX_EPOCH`].
///
/// J2000.0 历元与 Unix 历元之间的秒数。
///
/// 由 [`JULIAN_DATE_J2000`] 与 [`JULIAN_DATE_UNIX_EPOCH`] 导出。
pub const SECONDS_J2000_TO_UNIX: f64 = (JULIAN_DATE_J2000 - JULIAN_DATE_UNIX_EPOCH) * DAY;

/// Earth gravitational parameter, in cubic kilometers per second squared.
///
/// WGS 84 value, `GM = 398 600.4418 km^3/s^2`, with an uncertainty that is
/// dominated by the uncertainty in the Newtonian constant of gravitation.
/// Orbit propagation uses kilometers, so the value is given in those units
/// rather than in SI.
///
/// 地球引力参数，单位为立方千米每二次方秒。
///
/// WGS 84 取值 `GM = 398 600.4418 km^3/s^2`，其不确定度主要来自牛顿万有引力常数的
/// 不确定度。轨道传播使用千米，故该值以千米给出而非 SI 单位。
pub const EARTH_MU: f64 = 398_600.441_8;

/// Earth equatorial radius, in kilometers.
///
/// WGS 84 semi-major axis, `a = 6 378.137 km`.
///
/// 地球赤道半径，单位为千米。
///
/// WGS 84 半长轴，`a = 6 378.137 km`。
pub const EARTH_EQUATORIAL_RADIUS: f64 = 6_378.137;

/// Earth flattening, dimensionless.
///
/// WGS 84 value, `f = 1 / 298.257 223 563`.
///
/// 地球扁率，无量纲。
///
/// WGS 84 取值 `f = 1 / 298.257 223 563`。
pub const EARTH_FLATTENING: f64 = 1.0 / 298.257_223_563;

/// Earth rotation rate, in radians per second.
///
/// WGS 84 value. This is the nominal mean angular velocity of the Earth,
/// `omega = 7.292 115e-5 rad/s`.
///
/// WGS 84 取值，即地球的名义平均角速度，
/// `omega = 7.292 115e-5 rad/s`。
pub const EARTH_ROTATION_RATE: f64 = 7.292_115_0e-5;

/// Earth second zonal harmonic, dimensionless.
///
/// WGS 84 value, `J2 = 1.082 626 683e-3`.
///
/// WGS 84 取值，`J2 = 1.082 626 683e-3`。
pub const EARTH_J2: f64 = 1.082_626_683e-3;

/// Standard atmosphere sea level pressure, in pascals.
///
/// Exact by definition of the standard atmosphere.
///
/// 标准大气海平面气压，单位为帕斯卡。
///
/// 由标准大气的定义精确确定。
pub const STANDARD_ATMOSPHERE: f64 = 101_325.0;

/// Zero degrees Celsius on the thermodynamic temperature scale, in kelvin.
///
/// Exact by definition of the Celsius scale.
///
/// 热力学温标上零摄氏度对应的温度，单位为开尔文。
///
/// 由摄氏标度的定义精确确定。
pub const ZERO_CELSIUS_IN_KELVIN: f64 = 273.15;