Collision of cosmic rays with the upper atmosphere gives rise to a stream of particles called muons. The proper lifetime of these particles has been determined to be 2.2 µs (microseconds). Once formed, they travel through the atmosphere at very high speed. Scientists have observed the average lifetime of these rapidly moving particles to be about 10 times longer than what it would be for muons in the laboratory reference frame. Approximately how fast must the muons be traveling relative to Earth?