Physic Labs

Cosmology and astrophysics

Cosmic microwave background (CMB)

Read an all-sky temperature map of the cosmic microwave background. Identify the nearly isotropic T0≈2,725T_0 \approx 2{,}725 K background and the tiny anisotropies ΔT/T∼10−5\Delta T/T \sim 10^{-5} by inspecting hot and cold spots.

Research

⚠ Simulated model; no equipment hazards. Note real satellite maps only emerge after subtracting foreground emission from our galaxy.

Equipment

  • Simulated all-sky map in a Mollweide-like projection
  • Anisotropy-amplitude slider (amplifying the temperature contrast)
  • Viewing-angle slider and a Pause button

Procedure

  1. Set anisotropy amplitude to minimum

    Drag the amplitude slider low: the map becomes almost uniform — this is close to the true anisotropy ΔT/T∼10−5\Delta T/T \sim 10^{-5}, nearly invisible on a linear temperature scale without amplification.

  2. Amplify to count hot and cold spots

    Increase the amplitude gradually and rotate the view. Observe the characteristic spot size and random distribution around the mean temperature; hot and cold spots are roughly balanced, reflecting the nearly symmetric oscillations of the primordial plasma.

  3. Connect to the blackbody spectrum

    Keep in mind this map sits on a nearly perfect blackbody spectrum at T0≈2,725T_0 \approx 2{,}725 K — evidence the universe was once a hot, dense plasma in thermal equilibrium. Predict: as the universe expands, how does the background temperature evolve?

Simulation

Experiment history

In 1948 Ralph Alpher and Robert Herman — building on George Gamow's Big Bang theory — predicted the universe should retain a background radiation of a few kelvin. The prediction was largely forgotten until Robert Dicke and Jim Peebles at Princeton independently re-derived it and prepared to measure it in 1964. Meanwhile, Arno Penzias and Robert Wilson at Bell Labs found unexplained ~3.5 K antenna noise while calibrating the Holmdel horn antenna — the background itself; they shared the 1978 Nobel Prize. In 1992 the COBE satellite (John Mather, George Smoot; Nobel 2006) measured the most perfect blackbody spectrum known and first mapped the ~10⁻⁵ anisotropies.

Related physicists

Albert EinsteinArno Allan PenziasRobert Woodrow WilsonJohn Cromwell MatherGeorge Fitzgerald Smoot IIIJames PeeblesEdwin Powell Hubble

Related library topics

Cosmic microwave background (CMB)