Astronomers around the world are calling for international agreements to limit the spread of satellite constellations in space, with warnings that light pollution at night from the satellites damages vital scientific work. In Britain, the government is also being urged to impose new planning regulations to reduce light pollution to stop the loss of the nation's dark skies. Malcolm Brabant reports. PBS NewsHour is supported by - https://www.pbs.org/newshour/about/funders