This photograph shows a laser shot carried out by the Paris Observatory - PSL (Paris Sciences et Lettres) to measure the speed of light between its Meudon campus and the Arago Dome, at the Observatory of Paris in Meudon on October 9, 2026. (Photo by DIMITAR DILKOFF / AFP via Getty Images)

People watch a laser shot carried out by the Paris Observatory - PSL (Paris Sciences et Lettres) to measure the speed of light between its Meudon campus and the Arago Dome, at the Observatory of Paris in Meudon on October 9, 2026. (Photo by DIMITAR DILKOFF / AFP via Getty Images)

People watch a laser shot carried out by the Paris Observatory - PSL (Paris Sciences et Lettres) to measure the speed of light between its Meudon campus and the Arago Dome, at the Observatory of Paris in Meudon on October 9, 2026. (Photo by DIMITAR DILKOFF / AFP via Getty Images)

People watch a laser shot carried out by the Paris Observatory - PSL (Paris Sciences et Lettres) to measure the speed of light between its Meudon campus and the Arago Dome, at the Observatory of Paris in Meudon on October 9, 2026. (Photo by DIMITAR DILKOFF / AFP via Getty Images)

People watch a laser shot carried out by the Paris Observatory - PSL (Paris Sciences et Lettres) to measure the speed of light between its Meudon campus and the Arago Dome, at the Observatory of Paris in Meudon on October 9, 2026. (Photo by DIMITAR DILKOFF / AFP via Getty Images)

This photograph shows a laser shot carried out by the Paris Observatory - PSL (Paris Sciences et Lettres) to measure the speed of light between its Meudon campus and the Arago Dome, at the Observatory of Paris in Meudon on October 9, 2026. (Photo by DIMITAR DILKOFF / AFP via Getty Images)

This photograph shows a laser shot carried out by the Paris Observatory - PSL (Paris Sciences et Lettres) to measure the speed of light between its Meudon campus and the Arago Dome, at the Observatory of Paris in Meudon on October 9, 2026. (Photo by DIMITAR DILKOFF / AFP via Getty Images)

This photograph shows a laser shot carried out by the Paris Observatory - PSL (Paris Sciences et Lettres) to measure the speed of light between its Meudon campus and the Arago Dome, at the Observatory of Paris in Meudon on October 9, 2026. (Photo by DIMITAR DILKOFF / AFP via Getty Images)