Dec 19, 2022 LIGO could be used to detect giant alien spacecraft "They found it would have to be really big to generate gravity waves strong enough to reach Earth—perhaps the size of Jupiter. It would also have to be moving really fast—their calculations showed approximately 1/10 the speed of light. And it would have to be reasonably close—say about 326,000 light-years from Earth. They note that under such conditions, if they were to arise, researchers at LIGO should be able to spot the gravity waves generated. The researchers also note that if aliens are using warp drives, scientists on Earth should be able to spot them, too, using the same technology, because such a craft would also generate gravity waves."
Luke Sellers et al, Searching for Intelligent Life in Gravitational Wave Signals Part I: Present Capabilities and Future Horizons, arXiv (2022). DOI: 10.48550/arxiv.2212.02065
