Vampires

Humanity used to be terrified of vampires. Throughout history, tales of bloodsucking fiends that prey on innocent lives abound.

Nowadays, of course, ‘Twilight’ fans are too busy mocking their sparkly bodies to be properly afraid.

But if you’ve ever wondered how long it would take for a real vampire to kill you, a group of students from the University of Leicester’s Department of Physics and Astronomy have used a combination fluid dynamics and biology to provide an answer.

Most vampires go with a classic neck-biting, to get at the external carotid artery. The group has estimated it would take a vampire around six and a half minutes to drain 15 percent of your blood using this method – enough blood loss to start significantly hurting you. More than that causes your heart rate to change and your body to start reacting negatively. That’s why when you donate blood, the technician takes less than a tenth of your total blood volume.

The main artery that leaves the human heart is called the aorta; it splits into five smaller arteries that take blood to different parts of the body. The team was only interested in the common carotid artery, which brings blood to the neck and head. This artery then splits into the external and internal carotid arteries.

To simplify the calculations, they assumed the blood from the aorta splits evenly among the five smaller arteries and that they are all of the same thickness. This allowed the students to calculate the speed at which the blood flows through the carotid artery. Since the blood splits evenly among the external and internal carotid arteries, the speed of blood flow through the external artery is simply half that of the blood flow before the split.

Then, taking into account the pressure difference between the external carotid artery and the air, they were able to calculate how fast blood would flow out of two .5-millimeter punctures from a vampire’s fangs. This gives the vampire six minutes if they don’t plan on killing you.

Their findings might not be all that useful for science as a whole, but you have to admit, they’re pretty cool.