Before we get to the car, let's look at what the car is named after, the atom. An atom is a very, very small thing. So small, that over 20 billion of the little things can fit across the width of a human hair. So the Atom car, is small then. Well, there's another trait to atoms which is the real reason behind the Atom's name. An atom contains electrons (or in the case of a Hydrogen atom, just one electron), which orbit the nucleus (centre) of the atom. The electron has virtually no mass, which makes it fast. So the Ariel Atom is small, like an atom, and contains a very high revving Honda engine, like an electron.
The Atom is practically a road legal go-kart, but with a hell of a lot more power. This go-kart certainly isn't powered by a Briggs and Stratton lawnmower engine, like the ones I drove at my friend's birthday parties. The Atom has no doors and no roof. The headlights provide less light than an extinguished candle, and a toilet seat would be more kind to someone's backside than the bucket seats in the Atom.
We'll come to why the Atom is so under-furnished in a minute, but for now, let's look at the engine. It certainly isn't big, (it's only 2 litres) but it's also supercharged, to give up to 300 horsepower! So why are there no doors or no roof? The men in Somerset, England who build the Atom seem to be on a diet. This clearly rubs off on their cars. The Atom weighs in at 612 kgs. This gives it a power to weight ratio of 650 horsepower per ton. The Bugatti Veyron (fastest production car in the world, remember) has a power to weight ratio of 446 horsepower per ton.