SPACETRC / UNIVERSE RULES
See a law through its variables.
Separate mass from weight. Then compare a star’s temperature with the peak wavelength of its radiation. Two small experiments, two transparent models.
01 / W = m g
Same mass. Different weight.
For a 70 kg mass, example surface weights are 686 N on Earth, 113.7 N on the Moon and 259.7 N on Mars. Mass is expressed in kg; weight force in N. Changing location does not change mass.
- Weight force
- Vacuum fall time
- Vacuum final speed
Constant gravity, vacuum, short drop
W = mg; t = √(2h/g); v = √(2gh). The object starts at rest. Local gravity is constant and drag is zero. Surface values are rounded examples; latitude, altitude and rotation details are not solved. In an atmosphere, shape and drag alter the fall. Apparent weightlessness in orbit does not mean gravity is absent.
Investigate: double the mass. Why does weight double while fall time from the same height stays unchanged? Then quadruple the height and compare the time ratio.
02 / λmax T = b
Temperature rises. The peak shifts.
For a blackbody spectrum per unit wavelength, λmax = b/T; b ≈ 2.897771955 × 10⁻³ m·K. At 5,800 K, the peak is about 500 nm.
- Peak wavelength
- Peak region · approximate
- Surface power ratio / 5,800 K
The graph is not a photograph of a star.
The curve is calculated from Planck’s relation and divided by its own peak; it does not show the actual power difference between temperatures. The adjacent ratio is (T/5800)⁴ for equal-area ideal blackbodies. The visible band is marked approximately as 380–700 nm. The peak is not a star’s single perceived colour: its broad spectrum, atmosphere, perception and instrument response matter. Real stars have absorption lines and atmospheric structure.
Bλ ∝ λ⁻⁵ / [exp(hc/λkT) − 1]
h = 6.62607015 × 10⁻³⁴ J·s · c = 299792458 m/s · k = 1.380649 × 10⁻²³ J/K
Investigate: double the temperature. Compare peak wavelength and surface power ratio separately. Remember that peaks per unit wavelength and per unit frequency are defined in different coordinates.
SOURCE NOTEBOOK
Learn the relationship. Inspect the source.
- NASA Glenn · Free Falling Objects ↗
- NASA JPL · Planetary Physical Parameters ↗
- NASA Science · Earth and Moon ↗
- NIST · CODATA 2022 (SP 961, 2024) ↗
- NASA Imagine the Universe · Blackbody radiation ↗
Checked: 24 October 2026. The mission hardware, numerical budgets and investigation prompts on this page are original SpaceTRC teaching examples. They do not imply an institutional partnership or mission approval.