I had a request to explain a couple of the previous engineering jokes. The two jokes with the punch lines were based off a mathematics/physics concept call a cross product. To explain a cross product, you have to start with a vector. A vector ALWAYS has a magnitude (scalar value) and a direction. A cross product is the multiplication of two vectors, and the result of the cross product is another vector that tells you how close to being perpendicular the two vectors are. The direction of the resultant vector is always perpendicular to both of the vectors that were multiplied. Thus, three dimensional space is required to do this operation.
If you cross vector A with vector B, the resultant magnitude is A*B*sin(angle between A and B), and the direction is determined using the right hand rule. Put your right hand fingers in the direction of A, fold your fingers toward B, and where your thumb is pointing is the resulting direction. When A and B are perpendicular (90 degrees between them), the sine of 90 degrees is 1, so the resulting magnitude is A*B. If the two vectors are parallel, the sine of 0 degrees or 180 degrees is 0, and the cross product is the vector 0.
One of the most common uses of the cross product is to determine torque. Usually you have a distance vector determined by the length of your wrench that points parallel to your wrench. Then you exert a force on your wrench perpendicular to the wrench, which when you take the cross product of these two vectors causes a torque in a direction perpendicular to the force and the distance. This is also why a longer wrench creates more torque - because the magnitude of the torque (cross product) is determined by the force*distance. The other common use of the cross product is to determine how much force a magnetic field will exert on an electronic charge.
So, the reason the joke is funny when it asks what you get when you cross a grape with an elephant is because the answer takes the cross product of the vector grape with the vector elephant. Statistics show 99% of the population considers these kinds of jokes to be lame. And, in order to take a cross product, both things must be vectors (no scalars allowed!).
Did you make it through all of that? How much drool is on your keyboard? Any vacant eyes yet? Was that so exciting that now everybody wants to be an engineer? Was the explanation so skilled that I should become a math or physics teacher? Probably not since it's hard to cram a whole semester of physics into a two paragraph explanation. ;-) But, it was fun for me to take a trip down college class lane. Next week: The joys of taking a dot product using vectors.