The exact maximum speed of Sonic the Hedgehog is debatable (and trust me, there are many people on the internet debating it), but it’s fair to assume that at the very least he is capable of running at 1,225km/h (761mph) – the speed of sound. The human world record, for comparison, is 44km/h (27mph), achieved by Usain Bolt during the 100m sprint at the 2009 World Championships in Athletics. But while Sonic would surely win every gold medal, would travelling faster than the speed of sound be survivable?


“Humans have flown in supersonic vehicles since the late 1940s and in hypersonic vehicles since the 1960s,” says Richard Leland, president of the National Aerospace Training and Research (NASTAR) Center. For clarity, supersonic flight is defined as speeds up to Mach 4.9, which represents 4.9 times the speed of sound, while hypersonic flight is defined between Mach 5 and 10.

“Neither supersonic flight nor hypersonic flight have an appreciable effect on the human body so long as the human is in a properly designed aircraft.”

But Sonic does not travel in aircraft, which are designed to deal with heat buildup due to friction with the atmosphere. “In order to reduce these temperatures, supersonic vehicles typically fly at altitudes of 60,000 feet [18,288m] or higher where the atmosphere is thinner,” says Leland, who speculates that on average Sonic travels between Mach 3 and Mach 5.

“Since Sonic the Hedgehog runs at roughly sea level, wind blast and temperature buildup would not be survivable,” he says. “To put it another way: he would break up and burn.”

Another factor is how Sonic would be affected by g-force. Leland explains that, generally, the average human can withstand up to 15G for a short time, if they are travelling forward. “It would definitely not be comfortable, and would likely induce some degree of injury,” he says. Still, this is more than can be handled by travelling backwards or vertically (like fighter pilots do) and is why astronauts face upwards, therefore travelling forward, when their shuttle is being launched into space.

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Sonic the Hedgehog
Sonic the Hedgehog © Joe Waldron

G-force wouldn’t be too much of an issue for Sonic during his run, as long it was at a consistent rate of motion and in one direction. Hence why, despite travelling at around 27,360km/h (17,000mph) in orbit, astronauts can move around more or less as easily as a passenger on an aeroplane. But Sonic’s tendency to rapidly accelerate and decelerate – both of which are lethal to living organisms – is quite another matter.

“If Sonic the Hedgehog were to accelerate to Mach 1 in one second, he would sustain 34G,” explains Leland. “If he were to accelerate to Mach 3 in one second, he would experience 114G. If he were to accelerate to Mach 5 in one second, he would experience 175G.”

He brings up the example of John Stapp, who in the 1950s, during his studies on the effects of deceleration, showed that a trained human can withstand at least 46.2G while accelerating/decelerating on a rocket sled. During these tests he broke ribs, lost fillings and temporarily lost his vision due to bleeding in his retinas. “Suffice to say, accelerations or decelerations of 114G and 175G would not be survivable,” Leland adds.

Not to mention the fact that if Sonic were to pass out or die while running, he would likely smash into another object. Leland cites a calculation conducted by, who figured out that the kinetic energy of a 35kg hedgehog travelling at the speed of sound equates to 2,058,858 joules. That’s a ridiculous amount of damage. And would no doubt make collecting rings while in mid-sprint a dangerous hobby.


Verdict: Dr Robotnik can rest easy. Sonic is likely to splat into hedgehog mince once he starts accelerating or hits a golden ring.

About our expert, Richard Leland

Richard Leland is an aerospace physiologist and former USAF Pilot who concentrates on research for aviation and space and aeromedical training equipment design and manufacture at Environmental Tectonics Corporation.

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Stephen Kelly is a freelance culture and science journalist. He oversees BBC Science Focus's Popcorn Science feature, where every month we get an expert to weigh in on the plausibility of a newly released TV show or film. Beyond BBC Science Focus, he has written for such publications as The Guardian, The Telegraph, The I, BBC Culture, Wired, Total Film, Radio Times and Entertainment Weekly. He is a big fan of Studio Ghibli movies, the apparent football team Tottenham Hotspur and writing short biographies in the third person.