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According to Einstein’s General Relativity, gravity travels at the speed of light. Proving it is far from simple, though: unlike light, gravity can’t simply be switched on and off, and is also extremely weak.

Over the years, various attempts have been made to measure the speed using studies of astronomical phenomena, such as the time delay of light as it passes through the huge gravitational field of Jupiter. While the results have been broadly in line with Einstein’s prediction, they’ve lacked the precision needed for compelling evidence. That’s now been provided by the celebrated detection of gravitational waves. Analysis of the signals picked up by the two giant LIGO instruments in the US has confirmed that gravity does indeed travel through space at the speed of light.

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Scientists at TU Wien, the University of Innsbruck and the ÖAW have for the first time demonstrated a wave effect that can lead to measurement errors in the optical position estimation of objects. The work now published in Nature Physics could have consequences for optical microscopy and optical astronomy, but could also play a role in position measurements using sound, radar, or gravitational waves.

With modern optical imaging techniques, the position of objects can be measured with a precision that reaches a few nanometers. These techniques are used in the laboratory, for example, to determine the position of atoms in quantum experiments.

“We want to know the position of our quantum bits very precisely so that we can manipulate and measure them with laser beams,” explains Gabriel Araneda from the Department of Experimental Physics at the University of Innsbruck.

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China’s first Mars simulation base opened to the press on Friday in Gansu Province in the northwest of the country, providing a glimpse of the project mainly intended to popularise space among youth.

The base is located in the Gobi Desert, 40 kilometres away from the downtown area of Jinchang, a city in Gansu. The natural features, landscape and climate are being described as resembling Martian conditions.

The newly-built base has an extravehicular site and nine modules, including an airlock module, a general control module and a bio-module.

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