Constants.md•3.43 kB
---
title: Physical Constants Library
kind: reference
header_svg:
src: "/assets/svg/tool-constants-hero.svg"
static: "/assets/svg/tool-constants-hero-static.svg"
title: "Physical Constants Library"
animate: true
theme_variant: "auto"
reduced_motion: "auto"
---
{% assign header_svg = page.header_svg %}
{% include header-svg.html %}
# Physical Constants Library
The Constants Library provides access to the most up-to-date physical constants from CODATA and astrophysical databases. All values include uncertainties and proper units.
## Available Constants
### Fundamental Constants
- **c** - Speed of light in vacuum
- **h** - Planck constant
- **hbar** - Reduced Planck constant (h/2π)
- **e** - Elementary charge
- **k_B** - Boltzmann constant
- **N_A** - Avogadro constant
- **G** - Gravitational constant
- **R** - Universal gas constant
### Electromagnetic Constants
- **epsilon_0** - Electric constant (permittivity of vacuum)
- **mu_0** - Magnetic constant (permeability of vacuum)
- **alpha** - Fine-structure constant
- **a_0** - Bohr radius
### Particle Masses
- **m_e** - Electron mass
- **m_p** - Proton mass
- **m_n** - Neutron mass
### Astrophysical Constants
- **M_sun** - Solar mass
- **pc** - Parsec
- **ly** - Light-year
- **au** - Astronomical unit
## Usage Examples
### Get a Single Constant
```json
{
"tool": "constants_get",
"params": {
"name": "c"
}
}
```
### Get Multiple Constants
```json
{
"tool": "constants_get",
"params": {
"name": "h"
}
}
```
## Response Format
Each constant returns:
```json
{
"name": "c",
"value": 299792458.0,
"unit": "m/s",
"uncertainty": 0.0,
"description": "Speed of light in vacuum",
"source": "CODATA 2018"
}
```
## Common Physics Calculations
### Energy-Mass Equivalence
```json
{
"tool": "cas",
"params": {
"expr": "m*c^2",
"vars": {
"m": {"value": 1, "unit": "kg"},
"c": {"value": 299792458, "unit": "m/s"}
}
}
}
```
### Planck Energy
```json
{
"tool": "cas",
"params": {
"expr": "hbar*c^5/G",
"vars": {
"hbar": {"value": 1.054571817e-34, "unit": "J*s"},
"c": {"value": 299792458, "unit": "m/s"},
"G": {"value": 6.67430e-11, "unit": "m^3/kg/s^2"}
}
}
}
```
## Accuracy and Sources
- **CODATA 2018**: Latest recommended values for fundamental constants
- **Uncertainties**: All values include standard uncertainties
- **Units**: SI base and derived units with proper formatting
- **Updates**: Constants are updated as new measurements become available
## Integration Examples
### Quantum Mechanics
Calculate the de Broglie wavelength:
```json
{
"tool": "cas",
"params": {
"expr": "h/(m*v)",
"vars": {
"h": {"value": 6.62607015e-34, "unit": "J*s"},
"m": {"value": 9.1093837015e-31, "unit": "kg"},
"v": {"value": 1e6, "unit": "m/s"}
}
}
}
```
### Thermodynamics
Calculate the thermal energy at room temperature:
```json
{
"tool": "cas",
"params": {
"expr": "k_B*T",
"vars": {
"k_B": {"value": 1.380649e-23, "unit": "J/K"},
"T": {"value": 300, "unit": "K"}
}
}
}
```
## Educational Applications
- **Problem Setup**: Automatically insert correct constant values
- **Unit Consistency**: Ensure all calculations use proper units
- **Uncertainty Propagation**: Include measurement uncertainties in calculations
- **Current Values**: Always use the most recent constant values