Ciro Santilli @cirosantilli 37

This game was mind blowing to Ciro Santilli and all kids. It felt so real. The perfect contrast between peaceful town work and saving the world. OMG.

Databases and projects:

Because of edit wars and encyclopedic tone requirements. See also: Wikipedia.

Thus OurBigBook.com.

Considering e.g. Newton's laws of motion, you take a system that is a function of time $f(t)$, e.g. the position of many point particles, and then you reverse the speeds of all particles, then $f(-t)$ is a solution to that.

The complex analogue of the special orthogonal group, i.e. the subgroup of the unitary group with determinant equals exactly 1 instead of an arbitrary complex number with absolute value equal 1 as is the case for the unitary group.

I guess you also have to change the sign of the gravitational constant?