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

A lecture by Roberto Trotta

The transcript and downloadable versions of the lecture are available from the Gresham College website:
https://www.gresham.ac.uk/lectures-and-events/cosmic-distance

Gresham College has been giving free public lectures since 1597. This tradition continues today with all of our five or so public lectures a week being made available for free download from our website. There are currently over 2,000 lectures free to access or download from the website.

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