Struct LightContext 

pub struct LightContext {
    pub two_grav_param_over_c3: f64,
}

Configuration for the Shapiro delay — the extra time light (or radio signals) takes to travel near a massive body because gravity curves spacetime.

In simple terms: when a light beam or radar pulse passes close to a star or planet, general relativity makes the path take a tiny bit longer than it would in flat space. This struct holds the single number that controls how strong that delay is for a particular central body (the Sun, a planet, another star, etc.).

Used in high-precision light-time calculations, spacecraft ranging, pulsar timing, and very-long-baseline interferometry (VLBI).

Fields

two_grav_param_over_c3: f64

2GM/c³ in seconds — the characteristic gravitational time scale used in the one-way Shapiro delay formula.

This is mathematically equal to 2 * GM / c³, where:

• G is Newton’s gravitational constant,
• M is the mass of the central body,
• c is the speed of light.

“GM” (often written as a single value called the standard gravitational parameter or μ) is the product of G and M. In real-world astronomy it is measured very accurately as one combined number (in m³/s²), so we keep it together here.

It tells the light-propagation code “how strong the gravitational slowing is” for this body. Bigger value = stronger delay effect.

Most users never set this manually — just use SOLAR or from_grav_param().

Implementations

impl LightContext

pub const SOLAR: Self

Ready-to-use value for our own Sun, based on the exact IAU 2015 recommended constants.

Use this for any typical solar-system light-propagation calculation (radar to planets, spacecraft tracking, etc.).

pub const FLAT: Self

No gravitational delay at all (flat spacetime approximation).

Perfect for:

• interstellar or intergalactic distances,
• quick “ignore gravity” calculations,
• or when you want to apply your own custom gravitational model elsewhere.

pub const fn from_grav_param(grav_param: f64) -> Self

Creates a LightContext for any central body (planet, star, black hole, etc.).

Arguments

• grav_param — the body’s standard gravitational parameter (GM or μ) in m³/s². This is the product of Newton’s gravitational constant and the body’s mass.

Trait Implementations

impl Clone for LightContext

fn clone(&self) -> LightContext

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LightContext

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for LightContext

fn eq(&self, other: &LightContext) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for LightContext

impl StructuralPartialEq for LightContext