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ASTROPHYSICS
The pressure is on to choose between several proposals for space-based detectors.
In the wake of last month's historic detection of gravitational waves by a US-led collaboration, a range of Chinese proposals to take studies of these ripples in space-time to the next level are attracting fresh attention.
The suggestions, from two separate teams, are for space-based observatories that would pick up a wider range of gravitational radiation than ground-based observatories can. The most ambitious plan could give China an edge over the leading European proposal to detect gravitational waves from space, but whether a single country can achieve that on its own is unclear. Also under consideration are a possible collaboration between Chinese researchers and the European effort, and a cheaper Chinese plan.
Although an Earth-based detector - the US Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) - was the first to confirm a prediction made by Albert Einstein a century ago, launching the field of gravitational-wave astronomy, such detectors can pick up only limited frequencies. Advanced LIGO compares laser light beamed along two perpendicular detector arms to reveal whether one beam has been compressed or stretched by gravitational waves.
Each LIGO arm measures 4 kilometres, but picking up the frequencies that are richest in gravitational waves requires distances of hundreds of thousands of kilometres or more. This can be achieved only in space, where spacecraftequipped with lasers can be positioned at these distances. Space-based detectors also avoid fluctuations in Earth's gravitational field, which can obscure signals.
With such considerations in mind, the European Space Agency (ESA) is pursuing a spacebased gravitational-wave detector. One of the Chinese proposals, Taiji, meaning 'supreme ultimate', is to...