Newtonian Gravity 101

What is Gravity?

Gravity is an invisible force that pulls objects toward one another. It’s what keeps us grounded on Earth, holds the Moon in orbit, and lets satellites stay aloft.

A Clear Example

When you jump in the air, you come back down. That’s gravity pulling you back. It’s constant, directional, and predictable. And not only that, it’s everywhere.

Why “Newtonian” Gravity?

We call it Newtonian because Sir Isaac Newton was the first to mathematically describe gravity’s behavior in the 17th century.

His formula for gravitational force:

$$ [ F = G \frac{m_1 m_2}{r^2} ] $$

Where:

$( F )$ is the gravitational force
$( G )$ is the universal gravitational constant ($ 6.67430×10−11 N⋅m2/kg2 $)
$( m_1 )$ and $( m_2 )$ are the two masses
$( r )$ is the distance between their centers

Newton’s model works incredibly well at human and planetary scales.

Even though scientists have a greater understanding of gravity now given Quantum Gravity Theory, Newtonian Gravity is still foundational to orbital mechanics today.

A Universal Force

Unlike magnetism or electricity, gravity always attracts and applies to all objects with mass, no matter where they are in the universe.

Why Does Gravity Matter?

What It Enables

Gravity enables:

Orbits and satellite trajectories
Stable walking and landing surfaces on celestial bodies
Conditions for atmosphere, water retention, and life
The difference between weightlessness and load-bearing design

Why It’s Important

For scientists and engineers, gravity influences:

Trajectory planning
Spacecraft hardware requirements
Biological experiments (e.g., bone density loss)
Fluid dynamics, especially in microgravity

Founders and mission designers rely on gravity models to estimate launch energy, determine orbital decay, and simulate environments for experiments.

Where Gravity Shows Up in Space Research and Industry

Area	Example
Human Spaceflight	ISS (microgravity), Moon missions (1/6G), Mars (0.38G)
Biotech	Cell behavior in microgravity, partial gravity tissue growth
Materials Science	Crystal formation in orbit, metal alloy uniformity
Satellite Engineering	Orbital insertion, deorbit burns
CubeSats	Gravity’s effect on passive stabilization and reentry
SBIR Research	Numerous grants focused on space environments and gravitational impacts

Common Misconceptions About Gravity

❌ “There’s no gravity in space.”
✅ Actually, there’s plenty of gravity. Objects in orbit are in freefall, which creates the experience of weightlessness.
❌ “Gravity is constant everywhere.”
✅ Gravity varies with both altitude and local mass distribution (it’s slightly weaker on Everest than at the bottom of the Mariana Trench).
❌ “Microgravity means no gravity.”
✅ Microgravity means very small residual accelerations (usually referred to as 1×10-6 G), not true zero-G.

How Spark Gravity Connects to Newtonian Gravity

At Spark Gravity, we’re building platforms to explore and enable artificial gravity in space. From rotating labs to modular research stations, our goal is to create programmable gravity environments that expand what’s possible in biotech, materials, and exploration.

To do that, we need to deeply understand gravity, starting with Newton’s formulation.

Whether we’re simulating Mars-level gravity or stabilizing payloads in LEO, Newtonian physics remains our baseline tool.

Understanding gravity isn’t just academic for us, it’s a design constraint, a control input, and an enabler of entirely new space-based industries.