A spin 1/2 particle in quantum physics defies what we normally think of as common sense. An object with a spin of 0 has complete rotational symmetry, i.e. you can spin it any number of degrees and it will look exactly the same. A circle is spin 0. An object with a spin of 2 can be spun 180 (or any multiple of 180 degrees) and will look exactly the same. A rectangle is spin 2. An object with a spin of 1 has to be spun around 360 degrees before it look the same as it did when you started. A one-way sign is spin 1. A spin 1/2 particle, though, can be spun 360 degrees and it will not look the same as it did when you started. It will only look the same once it has been spun 720 degrees. There is no example from everyday life of something tht is spin 1/2 (obviously!) For more information, read Stephen Hawking's A Brief history of Time.