🛰️
Gravity Lab
a static mini-site
Curvature • attraction • orbits

Gravity: the quiet rule that runs everything.

From falling apples to black holes, gravity is the interaction that shapes motion at every scale. This page gives you the core idea, the key equations, and a few interactive toys—no backend, no frameworks beyond CDN.

Try the calculators Orbit demo
Earth gravity
9.81 m/s²
Universal constant
G ≈ 6.67e−11
Live feel
Gravity slider
g = 9.81 m/s² (Earth)
9.81
0 → floaty • 9.81 → Earth • 30 → “heavier than Jupiter”
If you drop something from
meters, fall time ≈ 1.43 s
Uses the basic vacuum formula: t = √(2h/g)

What gravity “is” (in two flavors)

In everyday physics, gravity is a force pulling masses together. In Einstein’s general relativity, it’s better described as the curvature of spacetime: mass-energy tells spacetime how to curve, and curved spacetime tells objects how to move.

Newton’s law (force)
F = G · (m₁m₂ / r²)
Bigger masses → stronger attraction. Bigger distance → much weaker (inverse-square).
Near Earth (acceleration)
a ≈ g ≈ 9.81 m/s²
This “g” is the gravitational acceleration at Earth’s surface (varies slightly by location).

Gravity myths (quick debunk)

  • “Heavier things fall faster.”
    In a vacuum, all objects accelerate equally; air resistance is the culprit in real life.
  • “No gravity in space.”
    There’s plenty—astronauts are in continuous free-fall (orbit).
  • “Gravity is a kind of magnetism.”
    Different interaction; gravity acts on mass-energy, not electric charge.

Key numbers

A few constants and typical values people actually use.

G (grav. constant)
6.674×10⁻¹¹
N·m²/kg²
Earth g
9.81
m/s²
Escape velocity
11.2
km/s (Earth)
LEO speed
~7.8
km/s (low Earth orbit)

Weight on different worlds

Weight is force: W = m·g. Mass stays the same; g changes.

Try 80 kg or whatever.
g
9.81 m/s²
Your weight
785 N
That’s about 80.0 “kg-force” on Earth (informal).
Note: People often say “I weigh 80 kg,” but kg is mass. Technically your weight is in Newtons.

Drop simulator

A quick visual using basic kinematics. Toggle “air” for a simple drag approximation.

time: 0.00s
est: 2.02s
Estimated fall time: 2.02 s
“Air resistance” here is a simplified model: it just reduces effective acceleration as speed increases, stronger for lighter/flatter objects.

Orbit intuition

Orbit is “falling sideways” fast enough that you keep missing the ground. Speed too low → crash; too high → escape.

This is a visual toy, not a full physics integrator. It maps “gravity strength” to orbit period.
Orbit controls
120 px
1.00x
Current g:
9.81 m/s²
Higher g → faster orbit for the same radius (in this toy model).