<unk> <unk> <unk> <unk> <unk>  ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ Approximately 3,800 people, representing 199 scientific institutes and 43 countries, form the CMS collaboration who built and now operate the detector.<unk> Approximately 3,800 people, representing 199 scientific institutes and 43 countries, form the CMS collaboration who built and now operate the detector. It is located in an underground cavern at Cessy in France, just across the border from Geneva.<unk> It is located in an underground cavern at Cessy in France, just across the border from Geneva. ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️  Question: How long is the CMS detector?
21.6 m long