Home▸Cosmology▸CMB Sky Map Simulation — Cosmic Microwave Background Temperature Fluctuations

🛰️ CMB Sky Map Simulation

Interactive Cosmic Microwave Background (CMB) sky map simulation. Generate a procedural all-sky temperature fluctuation map with adjustable contrast and angular scale, alongside a stylised power spectrum with acoustic peaks.

Cosmology2DModerate60 FPS

This interactive simulation generates a procedural Cosmic Microwave Background (CMB) sky map — a colourful, all-sky pattern of tiny temperature fluctuations left over from about 380,000 years after the Big Bang, when the universe first became transparent to light.

🔬 What It Demonstrates

The CMB's hot and cold spots record sound waves ("baryon acoustic oscillations") rippling through the early plasma. Regions that were slightly denser appear as tiny temperature differences — about 1 part in 100,000 — which this simulation generates procedurally as layered noise, plus a stylised power spectrum showing characteristic acoustic peaks.

🎮 How to Use

Increase fluctuation contrast to exaggerate the hot/cold pattern. Move angular scale to shift between large, smooth blobs (low multipole ℓ) and fine, speckled detail (high ℓ) — watch the marker move along the power-spectrum graph. Switch palette between the classic red/blue scheme, grayscale, or rainbow, and click New random seed to regenerate the pattern.

💡 Did You Know?

The CMB was discovered accidentally in 1965 by Arno Penzias and Robert Wilson, who initially thought a persistent radio hiss in their antenna was caused by pigeon droppings. It later earned them the 1978 Nobel Prize in Physics as the key confirmation of the Big Bang theory.

About this simulation

The Cosmic Microwave Background is the oldest light we can observe: relic radiation released when the universe cooled enough, about 380,000 years after the Big Bang, for electrons and protons to combine into neutral hydrogen and let photons finally travel freely — an event called recombination. Satellite missions COBE, WMAP and Planck have mapped this radiation across the whole sky, revealing tiny temperature fluctuations of about one part in 100,000 that trace sound waves frozen into the early plasma.

🔬 What it shows

A procedurally generated fluctuation map built from layered directional waves whose frequency, phase and amplitude are randomised per "seed". The angular scale slider changes the dominant wave frequency, mimicking how real CMB maps contain structure at many different angular sizes, summarised by the multipole moment ℓ in the power spectrum.

🎮 How to use

Fluctuation contrast stretches the colour mapping so subtle variations become visible. Angular scale shifts the pattern between broad blobs and fine speckle, with a marker tracking the corresponding position on the power-spectrum curve. Palette swaps the colour scheme, and the seed button regenerates a fresh random sky.

💡 Did you know?

The power spectrum's first acoustic peak, near multipole ℓ ≈ 220, corresponds to the largest sound waves that had time to complete one full compression by the moment of recombination. Its exact position let cosmologists measure the geometry of the universe and confirm it is very close to spatially flat.

Frequently asked questions

What is the Cosmic Microwave Background?

The Cosmic Microwave Background (CMB) is thermal radiation left over from the early, hot, dense universe. It was released about 380,000 years after the Big Bang during recombination, when the universe cooled enough for neutral atoms to form and photons to travel freely instead of constantly scattering off free electrons. Today it appears as a near-perfectly uniform microwave glow at about 2.725 K coming from every direction in the sky.

What causes the tiny temperature variations in the CMB map?

The variations, only about one part in 100,000, trace regions of the early universe that were very slightly denser or less dense than average. These density differences arose from quantum fluctuations stretched to cosmic scales during inflation, and they oscillated as sound waves in the hot photon-baryon plasma before recombination froze them in place.

What is the CMB power spectrum and why does it have peaks?

The power spectrum plots the strength of temperature fluctuations against angular scale, expressed as the multipole moment ℓ. Its series of peaks corresponds to sound waves of different wavelengths that had compressed or rarefied by differing amounts at the moment of recombination — the "acoustic peaks". Their positions and heights encode the universe's geometry, composition and age.

Who discovered the CMB and how?

Arno Penzias and Robert Wilson discovered the CMB by accident in 1965 while testing a sensitive radio antenna at Bell Labs. They found a persistent, uniform background noise they could not eliminate, which theorists soon identified as the predicted relic radiation from a hot Big Bang. The discovery earned them the 1978 Nobel Prize in Physics.

Is this simulation a real measurement of the sky?

No. This is a procedurally generated, artistic approximation using layered mathematical noise functions, not real satellite data. It is designed to illustrate the statistical character of CMB fluctuations and the shape of the acoustic power spectrum, not to reproduce the actual measured sky from missions like Planck or WMAP.

⚙ Under the hood

CosmologyCMBPower SpectrumCanvas 2DProcedural Generation

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install