Prove you are human

We are all familiar with the "type the text shown in the picture to prove you are human" check, but is it enough? As of now, it is generally believed that a computer cannot decipher such image. But it may become possible with the advance in image recognition technology. Who knows perhaps it is even already possible.. Sometimes simple questions, like "What is 4+7" are used, but this is also something a computer can solve. It is more difficult, but possible.

A better solution is something like this:

Original unknown

This idea can work very well for a math or science site. It can also serve as a good way to stop humans from spamming. While this particular question is very easy, those who didn't learned math in college will not be able to answer it. The answer to this specific question is 0, if you wondered.
For a niche blog such verification would be a very good idea - it will instantly assure that the people who comment know the subject well enough and are not spammers.

Despite the spam comments math pages is being hit with now, I am not going to use this way to fight with spam. I simply have no way to do it - Blogger doesn't allows me to put such checks. Unfortunately, perhaps.

Probably in the future it will become the norm, and in order to comment on a rocket science blog you well have to answer something like this:

What is the cosine of an ultraviolet wave traveling at a velocity of 27 kilojoules with a frequency of 3, as it extends perpendicular to the angle of inference, in an isotonic solution?

I have no idea, I am not a rocket scientists after all, so don't ask me.