William, from Honolulu, wrote in this week to ask:
If there was a space station/city the size of San Francisco in geostationary orbit, what would it look like from ground level with the naked eye? Would it cast a noticeable shadow?
When Einstein developed his general theory of relativity, commercial radio didn’t even exist yet. He could not possibly have imagined all of the fancy, high-tech equipment that scientists would use over the next 100 years to test—and verify—his predictions. In fact, he wasn’t even sure that all of his predictions could be tested experimentally because they resulted in such tiny, hard-to-measure effects.
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Given its stats, the recently discovered planet KELT-9b probably deserves its own baseball card. The planet and its host star, KELT-9, compose a unique system among the exoplanets discovered so far. KELT-9 is a relatively young, very hot star and its scorching heat warms the near side of the planet to a blistering 7,800 degrees Fahrenheit. KELT-9b isn't just the hottest gas giant so far discovered, it’s hotter than many stars.
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For the third time, a telltale signal of two colliding black holes has been caught by the dual detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO). Not only does the new detection reinforce LIGO’s capabilities and previous detections, it also provides clues about how these black hole systems form and just how common they are. In addition, each new detection is a chance to test the predictions of general relativity—predictions that can’t be tested in a lab.
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