Knowledge Center

Astronomy, In Plain Language

Short, accurate guides to the science behind every Cosmic Age Again tool — written so anyone can follow.

Planets

How Planetary Age Is Calculated

Your age on another planet depends on how long that planet takes to orbit the Sun.

What Is an Orbital Period?

The orbital period is the time a body takes to complete one orbit around another body.

What Is Surface Gravity?

Surface gravity determines how much you would weigh on another world.

What Is a Pi Age?

Your Pi Age celebrates every π Earth years of your life as one Pi year.

What Is a Phi Age?

Phi Age uses the golden ratio to mark harmonious milestones in your life.

Read more →The Moon

Moon Phase on Your Birth Date

The Moon's phase on the day you were born is your birth moon phase.

How Much Would You Weigh on Mars?

Your weight on Mars is about 38% of your weight on Earth.

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What Is a Supermoon?

A supermoon happens when a full moon coincides with the Moon's closest approach to Earth.

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What Is a Lunar Eclipse?

A lunar eclipse occurs when Earth blocks sunlight from reaching the Moon.

What Is the Perseid Meteor Shower?

The Perseids are an annual meteor shower caused by debris from comet Swift-Tuttle.

Read more →The Moon

How Many Full Moons in Your Lifetime?

A full moon occurs every 29.53 days, so they add up faster than you might think.

Astronomy vs Astrology — What Is the Difference?

Astronomy is a science; astrology is a belief system. They share roots but diverged centuries ago.

What's Your Real Zodiac Sign? The Astronomy-Based Answer (Not Astrology)

If you were born on September 4, your traditional sign is Virgo — but the Sun was actually in front of Leo that day. Here's your real constellation, calculated, not guessed.