John Mather on COBE, the Big Bang and Early Galaxies

Astrophysicist John Mather discusses measurements of the cosmic microwave background and the questions that remain about the early universe. The host introduces the COBE map of small temperature differences across the sky.

Mather grew up around a dairy farm and recalls early conversations with his father about cells and chromosomes. A visit to a natural history museum and planetarium deepened his curiosity about origins.

As a graduate student at Berkeley, he wanted to build an instrument to measure the spectrum of the cosmic microwave background, radiation associated with the hot early universe.

The balloon-borne instrument did not work, but he completed his thesis and later joined a NASA laboratory. He and colleagues proposed making the measurement from space.

He recalls the team proposing a satellite mission and eventually presenting a spectrum that closely matched the expected blackbody curve. The audience recognized its importance for the hot Big Bang model.

COBE also mapped small temperature variations in the background radiation. Mather explains that an exactly uniform universe would lack the initial variations that help structure form.

He discusses how physical laws allow complexity: particles, atoms and reactions produce structures under suitable conditions. The interview uses this as a bridge from early radiation to matter.

He describes gravity as important for gathering matter and forming stars and galaxies. Gravitational collapse can turn an expanding, initially near-uniform environment into locally structured regions.

The early fluctuations recorded in the cosmic background provide evidence used to study the growth of structure. A colored map is a representation of temperature differences, not a photograph of present-day galaxies.

Mather recalls Stephen Hawking’s praise for the temperature map and reflects on the connection between the early universe and the formation of the structures that made life possible.

He notes that unifying gravity and quantum mechanics remains difficult. The cosmic background offers clues about the early universe, but it does not answer every question about fundamental physics.

Later missions confirmed and refined measurements of the background. Mather describes the importance of independent confirmation and improved observations.

He says observations with Hubble revealed galaxy growth that challenged earlier expectations, motivating instruments that could look farther back in time.

Mather describes early James Webb Space Telescope images as adding to the puzzle of how quickly galaxies formed. He offers possible explanations as open research questions, not established discoveries.