SPACE-TIME is mostly empty. Though there are at least 100 billion galaxies - each home to around too billion stars -and lots of galactic dust, the universe is so vast that there are huge tracts of space-time between every star and more still between every galaxy. Even the nearest star to Earth (the sun) is nearly 150 million kilometres away, meaning the fastest thing in the universe (light) still takes 8 minutes to get from there to here, despite travelling at 300,000 kilometres per second.
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