It doesn’t matter if you blink ― you’ll probably miss it.
The U.S. Air Force has shared a test of a hypersonic sled traveling at 6,599 mph. You’ll just have to take their word for it because as the video shows, it’s almost impossible to see the accomplishment, even when the footage is slowed to quarter-speed.
Holloman Air Force Base in New Mexico said last week that the rocket sled launched on its High-Speed Test Track hit Mach 8.6. It did not give a date for the test.
According to a Defense Department fact sheet, the 10-mile rocket sled test track is believed to be the longest of its kind in the world. The track is often used to test components of hypersonic weaponry, including guidance and control systems, The Drive reported. However, the Defense Department did not specify what was tested in this video.
This article originally appeared on HuffPost.