The orbit stretches
The difference between closest and farthest approach grows.
Milanković Cycles, Explained Visually
Why Do Ice Ages Come and Go?
Three slow changes in Earth's orbit and axis redistribute sunlight. Cooler northern summers can let snow survive; climate feedbacks amplify the change.
StretchOrbit shape · ~100,000 yearsLeanAxis tilt · ~41,000 yearsWobbleAxis direction · ~23,000 years
Step 1 · The Big Idea
The 30-Second Answer
Milanković cycles do not simply make the whole planet hotter or colder. They redistribute incoming sunlight—insolation—by season and latitude.
- 01
Earth moves
Its orbit and axis change slowly and predictably.
- 02
Sunlight shifts
Different seasons and latitudes receive different amounts.
- 03
Summer decides
Cool northern summers leave more winter snow unmelted.
- 04
Feedbacks amplify
Ice, oceans, greenhouse gases, and snowfall grow the response.
Why 65° North?
The latitude where great northern ice sheets grew
Around Alaska, northern Canada, and Scandinavia, a cool summer can leave some winter snow behind. Repeat that for many years and ice can accumulate. This is why northern summer sunlight at 65°N became the classic orbital indicator.
Orbit Shape · Eccentricity
Earth's orbit shifts between nearly circular and slightly more elliptical. The Sun remains at one focus—not at the center.
Distance contrast
Sunlight is stronger at perihelion and weaker at aphelion.
It amplifies timing
Eccentricity strengthens or weakens the seasonal effect of precession.
RounderTodayMore elliptical
Closest0.983 AU
Farthest1.017 AU
Sunlight contrast6.9%
The diagram exaggerates orbit shape 5× so the real, subtle change is visible.
Axis Tilt · Obliquity
Earth's axis leans between about 22.1° and 24.5°. More tilt intensifies seasons—especially at high latitudes.
The axis leans
The angle changes by only 2.4°, slowly and continuously.
Season strength
More tilt brings brighter high-latitude summers and darker winters.
Summer melt
Stronger northern summers can remove more of the previous winter's snow.
Milder seasonsTodayStronger seasons
Axis tilt23.44°
65°N daylight21.1 h
Summer sunlight478 W/m²
Axis Direction · Precession
Earth's axis traces a slow circle. Together with the rotating orbital ellipse, this changes which season occurs near the Sun.
The axis points elsewhere
Like a spinning top, its direction changes while the tilt remains.
Season meets distance
Northern summer can occur nearer perihelion or aphelion.
Opposite hemispheres
One hemisphere gets stronger seasonal contrast while the other gets less.
0°Today360°
Closest approachNorthern winter
Perihelion angle103°
Summer sunlight478 W/m²
Step 5 · The Combined Signal
No Single Cycle Is an Ice-Age Switch
Shape, tilt, and direction combine to change northern summer sunlight. The climate system then responds over thousands of years.
Weaker northern summers
More winter snow may survive, all else equal.
Ice reflects sunlight
Growing bright surfaces can reinforce cooling.
Oceans & gases respond
Slow feedbacks make the climate response much larger than the orbital nudge.
Step 6 · Recap
Three Motions. One Changing Pattern of Sunlight.
- 1
Earth's orbit and axis change predictably over tens of thousands of years.
- 2
Those motions redistribute sunlight by season and latitude—especially northern summer.
- 3
Snow, ice, oceans, greenhouse gases, and time amplify the orbital pacing.
An Important Distinction
Milanković cycles do not explain today's rapid warming
Orbital cycles unfold over tens of thousands of years. Modern warming is far faster and is driven primarily by human greenhouse-gas emissions.
Now Make the Pattern Yourself
Experiment with all three cycles
Go Deeper
Five questions, explained clearly
Read focused, source-backed guides to each orbital motion, the classic 65°N indicator, and the crucial distinction between ice-age pacing and modern warming.