by accident

1 - Like many finds in astronomy, the discovery of Uranus was by accident.

2 - A number of products that we commonly use today were developed quite by accident.

3 - Although most cities seem to form by accident, for thousands of years some of them have been designed.

4 - Saccharin, a white, crystalline compound that tastes more than 100 times sweeter than sugar, was discovered by accident in 1879.

5 - Inventions don't generally happen by accident or in a random order: science and technology progress in a very logical way, with each new discovery leading on from the last.