In a new live-action film directed by Deadpool director Tim Miller, Sega’s snarky speedster, Sonic the Hedgehog, will barrel onto the big screen at his infamously supersonic velocity. Is Miller savage enough to engineer a human-sized hedgehog and deploy it a speed faster than the speed of sound? If he is, the laws of physics dictate he better not point it at anyone, unless he wants to deal with a murder charge on top of the literal fire he’ll already have to tend to.
Youtube science guru Vsauce3 considered the physics of the anthropomorphic blue ball in a 2012 video, concluding that, at full speed, Sonic is essentially a quill-covered bullet. Hardcore fans disagree on his maximum speed, but they generally agree that he moves at the speed of sound: at least 768 miles per hour. (For comparison, your average passenger jet crawls by at around 560.5 miles per hour.) Vsauce calculates that Sonic can go from zero to Mach 1 — that is, 717 miles per hour (the speed of sound in air) — in about five seconds. Assuming Sonic is about the weight of a small man, he’ll accelerate at about 64 meters per second squared, which generates a force of about 4,480 Newtons.
A bullet, in comparison, flies at an average speed of 1,700 miles per hour. The force at which it strikes a person depends on the weight of the bullet, the gun that fired it, and how far it travels before it hits flesh, but broadly speaking, bullets have been estimated to kill at a force of 2,000 Newtons. In other words, get out of the damn way.
It’s possible, however, that Sonic might go up in flames before he can rip a hole through his obstacles. Running through air, as anyone who’s jogged against the wind knows, creates friction, and that friction is converted into heat — lots of it, at high enough speeds. Vsauce3 calculates Sonic would heat up at a rate of 98.6 degrees Fahrenheit per second, concluding that “he can only run for so long before he has to cool off for a bit.” If he doesn’t, it’s entirely possible he might ignite. Hedgehog quills are made of keratin — the same stuff as human hair and nails — and human hair is thought to start bubbling at temperatures as low as 374 degrees Fahrenheit, according to a Minnesota police department investigation of the use of hairstyling tools as arson weapons. Given these numbers — and barring the cooling effects of wind — Sonic would literally smoke passersby in about four seconds.
Miller would at least be able to rest assured that the humanoid blue hedgehog won’t lose his hearing — or burst anyone else’s eardrums — when he creates a sonic boom. If Sonic travels at supersonic speeds, he will certainly blast through the sound barrier, but the effect that boom will have on him and his surroundings is minimal because his tiny body won’t actually displace that much air; accordingly, he won’t create a pressure change that could do too much damage, even at close (16-foot radius) quarters. Free fall record holder Felix Baumgartner, Vsauce3 notes in the video, broke the sound barrier while falling through the air in 2012 and didn’t notice a thing.
While it isn’t clear which parts of Miller’s live-action film will be live and which will be animated, we hope, for his sake, that he plays it fast and loose with the actual science.