On Saturday afternoon, the moon will be the closest it's been to Earth in more than 18 years. The "supermoon," as observers have dubbed it, will appear at 3 p.m. ET at a distance of 221,565 miles away. It will appear 14 percent larger and 30 percent brighter than your average full moon, weather permitting. The reason why the moon will be so much closer is due to a fluke of orbital mechanics. But don't be alarmed: Although the supermoon will result in a dramatically large range of high and low ocean tides—which could result in flooding problems if combined with a coastal storm at the same time—it won't cause a natural disaster.