How We Measure the Universe

The 'How We Measure the Universe' episode of 'The Infinite Monkey Cage' podcast delves into the vastness of the cosmos and the intricate methods used by scientists to comprehend its size and scale. The episode begins with a humorous reflection on the historical simplicity of the universe's model, contrasting it with the current understanding of a vast and expanding universe. The panel, consisting of Adam Masters, a lecturer in planetary science, Jo Dunkley, a professor of physics, and comedian Jo Brand, engage in a discussion moderated by hosts Robin Ince and Brian Cox.

Adam Masters highlights the discovery of subsurface oceans on Jupiter and Saturn's moons as a potential habitat for life, while Jo Dunkley emphasizes the sheer enormity of the universe. The conversation shifts to the practical challenges astronomers face when trying to measure the universe from Earth. Jo Dunkley explains the historical progression of cosmic measurement, starting with the 1790s transit of Venus and the concept of parallax, which allowed for the determination of the solar system's size. The panel discusses the use of this method to measure distances to stars and the difficulty of extending this technique beyond our galaxy.

The episode then explores Henrietta Swan Leavitt's pivotal discovery of Cepheid variable stars in the early 20th century, which provided a new rung on the cosmic distance ladder. Leavitt's work enabled astronomers to measure distances to nearby galaxies and eventually led to Edwin Hubble's groundbreaking realization that smudges of light previously thought to be within the Milky Way were actually other galaxies. The panel reflects on the historical underappreciation of female astronomers like Leavitt and the ongoing challenges faced by women in the field.

The conversation also touches on the use of supernovae as standard candles to measure even greater cosmic distances. The episode concludes with a discussion on the observable universe's size, estimated to be between 40 and 50 billion light years, and the intriguing possibility that the universe may be finite yet boundless, akin to the surface of the Earth.