One Question Per Page false false Earth does not appear to be in any danger from any asteroids that measure one kilometre wide. 1 We don’t need to worry about small asteroids under 20 metres wide. 2 A special telescope will provide a complete defence against asteroids hitting Earth. 2 PHAs are the biggest concern, but they’re still not an immediate threat. 1 Didymoon’s orbit is not stable. 3 HAMMER may or may not need nuclear weapons to save Earth from an asteroid. 1