It's about nine-tenths as fast as The Speed of Sound
In other words, 627.630 knots is 0.9410 times the speed of The Speed of Sound, and the speed of The Speed of Sound is 1.06 times that amount.(in dry air at 20°C)
The speed of sound in dry air at 20°C (68°F) is 667 knots. Air is a relatively poor acoustic conductor, however, as sound will travel at speeds of between 2,910 knots to 3,030 knots in water, depending on its salinity.
It's about four-fifths as fast as a Bullet (Handgun)
In other words, 627.630 knots is 0.8410 times the speed of a Bullet (Handgun), and the speed of a Bullet (Handgun) is 1.190 times that amount.(for .40 Smith & Wesson 135 grain Sierra JHP, VV 3N37 powder, Fed. 100 primer, Remington case) (muzzle velocity)
A 0.40 caliber Smith & Wesson bullet has a muzzle a velocity of 745 knots. This type of ammunition has been the standard issue round of the United States Federal Bureau of Investigation (FBI) since 1990.
It's about half as fast as a Jet Fighter
In other words, 627.630 knots is 0.480 times the speed of a Jet Fighter, and the speed of a Jet Fighter is 2.10 times that amount.(for Lockheed Martin F-16, a.k.a. Fighting Falcon, a.k.a. Viper) (maximum speed at altitude)
An F-16's maximum speed at altitude is approximately 1,300 knots. The F-16 has a flight ceiling of approximately 15 km (9.32 mi).
It's about one-third as fast as a Bullet (Rifle)
In other words, 627.630 knots is 0.3530 times the speed of a Bullet (Rifle), and the speed of a Bullet (Rifle) is 2.830 times that amount.(5.56 x 45 mm, a.k.a. 5.56 NATO)
A 5.56 x 45 mm cartridge is fired at a velocity of 1,780 knots. As the NATO rifle cartridge, it is used by the military forces of more than thirty-one countries, including use in the M16 series, M4 Carbine, HK-416, and M249 Squad automatic weapons used by the United States armed forces.
It's about three times as fast as a Peregrine Falcon
In other words, 627.630 knots is 2.990 times the speed of a Peregrine Falcon, and the speed of a Peregrine Falcon is 0.3340 times that amount.(a.k.a. Peregrine, a.k.a. Duck Hawk, Falco peregrinus)
The Peregrine Falcon can reach speeds of up to 210 knots when diving. Falcons are sometimes sent to scare smaller birds away from airports to improve air traffic safety and were used in World War II to intercept carrier pigeons used by enemy forces.
It's about three-and-a-half times as fast as The CRH (train)
In other words, the speed of The CRH (train) is 0.30 times 627.630 knots.(a.k.a. Hexie Hao, 和谐号, a.k.a. 和諧號, a.k.a. Héxié Hào, a.k.a. "Harmony")
The CRH-3 train which runs on China's Beijing-Tianjin Intercity Railway are capable of speeds up to 190 knots. Theses train can make the 120 km (74 mi) journey from Beijing to Tianjin in about 30 minutes.
It's about three-and-a-half times as fast as a Porsche 911