Skepticism, Medicine and Science News

Gravity Fingers Mathematically Explained

Since I have my math exam tomorrow, it seems only natural I should write about something math related. 

When water soaks down into the ground, it does not do so evenly, but rather forms spikes known as gravity fingers (see image below). Though it is a well known phenomenon in fluid mechanics, no one has been able to explain, mathematically, why it happens. In a recently published paper however, mathematicians at MIT give a both simple and elegant explanation. They got the idea when one of the researchers observed that gravity fingers looked very much like water flowing down a window (when you look at the picture it looks really obvious, it was definitely the first think I though of), which is a well understood phenomenon. Then it was just a matter of taking the equations describing that and apply it to water movement in soil. 

The short explanation to this phenomenon is that in order for water to flow down a window or in soil, the surface tension of the water has to be overcome. This will cause the water to flow in a finger-like pattern because as water builds up in the fingers, the weight overcomes the surface tension. My understanding of the phenomenon is that small indentations in the bottom flow line are bound to form no matter what because the soil/window is not perfectly uniform (and can never be), and when this happens the flow rate at the indentations increase because of the extra weight, leading to gravity fingers. 

Gravity fingers


December 14, 2008 Posted by | Math | , , , , , , , , , , , , | Leave a comment

Come on people…

This article just appeared on NewScientists web site, and I have to say it’s a really, really depressing read. What ever happened to scientific standards? The scientific method? Evidence? Clutching to the “God of the Gaps”-explanation for everything science has yet to explain is just…sad. “See, see, you scientists can’t explain exactly, to the most minute detail, how the brain works, therefore it must be God, and we should teach this in science classes”. What would you think if your doctor said something like this to you: “Well, we don’t have any evidence for this treatment, we don’t really know what it does either, or if it has any effect, but does it really matter, ey?” It’s basically the same thing… Explaining one unknown (the workings of the brain) with another unknown (God) is really pointless. What good does it do us? No predictions flow from that explanation. No scientific progress can be made from that explanation. The whole point of scientific theories is to make predictions. Just look at the theory of gravity. We know that gravity says that two objects with masses so and so will attract each other, and so we can predict that an object dropped from a certain distance from the surface of the earth will fall towards it. So we use this prediction and build rockets, planes, satellites… That’s the whole point of science. I have nothing against religion, but don’t drag it into the science class rooms. Please…. And remember, the computer you’re using, the chair you’re sitting on, the mouse pad, the desk, the building…it all comes from scientific research. None of that would be available if everyone simply said “God did it”.

October 22, 2008 Posted by | General Science, General Skepticism | , , , , , , , , , , , , | Leave a comment