{"id":19591,"date":"2026-09-09T10:15:11","date_gmt":"2026-09-09T00:15:11","guid":{"rendered":"https:\/\/geoffreychen.com\/why-a-round-manhole-cover-cannot-fall-through-its-opening\/"},"modified":"2026-09-09T10:15:11","modified_gmt":"2026-09-09T00:15:11","slug":"why-a-round-manhole-cover-cannot-fall-through-its-opening","status":"publish","type":"post","link":"https:\/\/geoffreychen.com\/zh\/why-a-round-manhole-cover-cannot-fall-through-its-opening\/","title":{"rendered":"\u5706\u5f62\u4e95\u76d6\u4e3a\u4ec0\u4e48\u4e0d\u4f1a\u6389\u8fdb\u81ea\u5df1\u7684\u4e95\u53e3\uff1f"},"content":{"rendered":"<\/p>\n<p><img data-recalc-dims=\"1\" decoding=\"async\" src=\"https:\/\/i0.wp.com\/public-assets.geoffreychen.com\/wordpress\/articles\/why-a-round-manhole-cover-cannot-fall-through-its-opening\/572b26dfe1ab31bf5fb66dd3.jpg?w=1140&#038;ssl=1\" alt=\"\u5706\u5f62\u4e95\u76d6\u4e3a\u4ec0\u4e48\u4e0d\u4f1a\u6389\u8fdb\u81ea\u5df1\u7684\u4e95\u53e3\uff1f\" 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href=\"https:\/\/mathworld.wolfram.com\/CurveofConstantWidth.html\" rel=\"nofollow\">https:\/\/mathworld.wolfram.com\/CurveofConstantWidth.html<\/a><br \/><a href=\"https:\/\/mathworld.wolfram.com\/ReuleauxTriangle.html\" rel=\"nofollow\">https:\/\/mathworld.wolfram.com\/ReuleauxTriangle.html<\/a><\/p>\n<p>","protected":false},"excerpt":{"rendered":"","protected":false},"author":17897162,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_geoff_meta_description_en":"A round cover has the same width in every direction, so it has no narrower orientation that can pass through its opening\u2014an example of constant 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