This is fastest thing on Earth — and it may not be light

Our home planet is full of high-speed feats, such as spaceship launches, race cars racing around a track, and cheetahs charging towards their prey.

However, what is the fastest object on Earth? The response is contingent upon the meanings of "thing" and "on Earth." Furthermore, photons and neutrinos, the leading contenders, are invisible to the unaided eye.

Light seems to be the most obvious solution. Light moves at about 186,000 miles per second (300,000 kilometres per second) in a vacuum. Nothing that we are aware of can travel faster than this in the universe.

But is light a thing? On this, physicists are not entirely at odds. Some say no, since light is massless. Others respond that light is both a particle and a wave at the same time because of the peculiarities of quantum mechanics. Particles are things, according to the majority of physicists.

Those particles, known as photons, are the fastest things in space, according to University of Utah scientist John Matthews.

It gets a little trickier on Earth unless you're in a vacuum chamber. A photon's velocity somewhat slows down as it enters Earth's atmosphere. And after that, given the correct conditions, it might face some competition. According to Matthews, this is because not all particles experience the same degree of atmospheric slowness that photons do.

Matthews is a member of a team that has discovered multiple extremely fast particles that come from high-energy cosmic rays—showers of subatomic particles that come raining down from space onto Earth. 

In 1991, his colleagues discovered one of these particles—dubbed the Oh-My-God particle—from the highest-energy cosmic ray that hasn't yet been discovered.

Particles like these start out going extremely close to the speed of light in a vacuum. But when they hit Earth's atmosphere, "by their nature, they just continue to barrel ahead," Matthews said. "So they're exceeding the speed of light in the atmosphere."

Accordingly, the Oh-My-God particles are not at the top of the list of the fastest objects on Earth with mass. According to Justin Vandenbroucke, a particle physicist at the University of Wisconsin-Madison, the neutrino wins that prize instead.

In terms of subatomic particle mass, the Oh-My-God particle is most likely a proton, or at least proton-like. Because a neutrino's mass is at least ten billion times lower than a proton's, it can move even more quickly with the same amount of energy due to fundamental physics.