Smack dab in the middle of a forest preserve about 25 miles west of Chicago, Argonne National Laboratory is building the fastest computer in the world. Its name is Aurora. Once it’s turned on in 2021, Aurora will be able to do more than one quintillion (that’s a 10 with 18 zeros behind it) operations per second, said Rick Stevens, associate laboratory director for computing, environment and life sciences at Argonne.