How can sharks smell one drop of blood in however much water?

I discovered in my research of sharks that they can smell one drop of blood in…I can’t remember how much water but it was a lot. Anyway, my point is, how does the shark smell this blood that is, let’s say, 40 yards away when there is no physical contact between the shark’s nose and the blood. I can understand how one could smell a freshly baked pie in a windowsill because the little smell particles (I will call them) can move through the air to the person’s nose. I don’t understand how in water a shark could smell this blood. How are the smell particles moved to the shark’s nose? Do they move at the speed of light or what?

Indeed the sense of smell of many land animals is very sensitive–I think to tens of molcules, which is an extraordinary dilution. I don’t know about sharks, perhaps they can smell blood–but I am speculating that we are on the border of an old wive’s tale here–I doubt considering the dilutions involved that the sense of smell will be effective for more than a hundred, perhaps a few hundred meters. Also, considering the time it would take “blood” molecules to drift by current, tide, wave action, other means, etc., one definitely has to take into account how far the blood molecules have traveled in a fixed time. Smelling recent blood a mile away for example–physically impossible for both reasons I’ve listed. Probably more likely, the sharks are sensing vibrations which travel at the speed of sound in water, something like 4000fps? more or less.

This isn’t an old wives tale. It’s a fact. The human brain devotes about 1/12 of it’s brain to the sense of smell whereas a shark uses 1/3 of it’s brain. The sense of smell is so vital to the shark for it’s survival that it needs this large a part of it’s brain for smell. The point of the question was how does smell travel in water so the shark can smell it even though no obvious means of contact are being made between the shark and the blood.

Llardball, I remember reading a book in high school that claimed about 75 percent of a shark’s brain was devoted to its olfactory senses.


Armed, dangerous…
and off my medication.

In order to smell, the molecules MUST reach the animal. The question is, just how?

They mix the blood in a big tank of water with the big fishie. They don’t put a drop of it 40 yards away from the big fishie & expect it to smell it.

That’s just a guess, I don’t have a shark handy to ask. But then I have surfed lots of times with cuts & bleeding & ain’t seen no fishies come around.

Now ask how female moths manage to pick up the pheromones of males from miles away…