The Broken Cosmic Distance Ladder


Professor Roberto Trotta

Roberto Trotta is Visiting Gresham Professor of Cosmology and Professor of Astrostatistics at Imperial College London, currently on leave of absence to the International School of Advanced Studies in Trieste, Italy, where he is part of the senior leadership team establishing a new Data Science Institute.

His research focuses on cosmology, machine learning and data science. An award-winning author and science communicator, he is the recipient of the Annie Maunder Medal 2020 of the Royal Astronomical Society for his public engagement work. For more information about him, please visit his website:

Roberto Trotta’s lecture series are as follows:

2021/22 The Frontiers of Knowledge

2020/21 The Unexpected Universe

2019/20 The Nature of Reality

All lectures by the Visiting Professor of Cosmology can be accessed here.

Measuring distances to astronomical objects outside our Galaxy is a surprisingly hard challenge: it wasn’t until 1923 that Edwin Hubble obtained proof that Andromeda is indeed a galaxy in its own right. Today, astronomers extend distance measurements in the cosmos to the edge of the visible Universe, building up a ‘cosmic distance ladder’ made of several rungs.

This talk explored a major conundrum of contemporary astronomy: as observations have become more precise, the distance ladder appears today to be broken.

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