|MadSci Network: General Biology|
Hello Erica, Thank you for the question...seems ironic that I would answer this on Halloween. I think I heard of this scene in some conversation somewhere from the show "Rome", right? First, I don't think I have ever heard of this. It seems this would be something very rare to occur, considering the nature of being in a situation where you are struggling for survival, have no ballast available, and conceive of the need to go to this extreme. I read somewhere that in ancient Rome sailors feared death at sea, since their body would not be buried in the ground, instead floating on the water, possibly leaving them to wander the river Styx for a hundred years before being allowed to enter the land of the dead. Ok, on to the science... Would corpses be effective in such a dire situation to stay afloat? Yes. It is a matter of how many you are using, the nature of how they died, and how many people you were trying to put on this scary raft...Obviously if someone died or was killed with the body intact and not full of water (possibly by drowning), the body acts like pontoon with some buoyancy (although not a whole lot...). Rather than try to explain a lot of examples, I thought it best to give you some information on factors that make them float: Lungs: Lungs are like a sponge. When someone drowns, the air sacs in the lungs fill with water. Since a body without air in the lungs is denser than water, it sinks. A person who is killed on the surface and then put in the water tends to float, since the lungs are still full of air. Body Position: A person who was dead before entering the water can still sink depending on the position of the body. If the body is upright when dumped into the water, water can enter the lungs while air escapes. Hence, the body sinks after a short time. If the body is prone (face down), the air in the lungs can't escape, so the body floats. Body Fat: Body fat is less dense than water. The fatter a person is, the more buoyant the body. Muscle on the other hand is denser than water, so people with a lot of muscle--or people who are just plain lean--tend to sink. Clothing: Some fabrics trap air well; others don't. Natural fibers, like cotton and wool, absorb water and so tend to sink. An exception is silk, whose fine fibers can be woven tightly enough to trap air. In more modern times, some synthetic fibers, like nylon and polyester, usually don't absorb water, so they can trap air. Putrefaction: As the corpse decays, it generates gases that collect in various body cavities. That's why corpses become bloated, whether in the water or not, giving us the charming term "floater." The water can also affect buoyancy: Salinity: Probably the most important factor is salinity. Salt water is denser than fresh water, so corpses tend to float in the ocean but not in a river. Temperature: The water's temperature affects its density. Water is densest at 4 degrees Celsius (about 39 degrees Fahrenheit). Bodies of water often have a thermocline (a depth where there's a dramatic change in temperature). Warm waters "float" and circulate by convection when warmed by the sun; colder waters "sink" and tend to stay there. Hence, there is a slight (very slight) tendency for bodies in cold water to float, since they may be less dense than the water surrounding them. You asked the question as to what happens to a body in the water, regarding rotting or being scavenged by the ocean's inhabitants. Bodies exposed to water decompose approximately four times faster than in earth, and if the water is warm or polluted, this occurs much faster. Insects also get into the act. Bodies that float near land for even a few minutes will have maggot infestations in all body cavities. Aquatic insects may also feed on the body, but these insects seem to accidentally happen onto the body rather than being attracted by the odor. (Forensic scientists are investigating whether aquatic insects can be used to estimate the time a body was immersed in water). If a body rests in water for only a short time, especially if the water is cold and contains minimal fish life, a variety of changes can occur. The skin of the palms and soles intially becomes very wrinkled, called "washerwoman skin" by pathologists, looking similar to a person's hands and feet after spending too much time in a swimming pool or bathtub. If the body is submerged in cool (less than 70F or 21C) to cold (less than 40F or 4,4C) water for as little as one to three weeks, the corpse's tissues convert to adipocere, a compound that stops the activity of bacteria. The preservation from cold water was exemplified by two bodies trapped for five years in a car that sank in Lake Superior outside of duluth, Minnesota. The very cold water produced extensive adipocere formation and well-preserved internal organs. After bieng in water for hours to days, a corpse's skin becomes white, soft, and extremely unpleasant to sight and smell. In warmer water, the decomposition advances rapidly, with the skin quickly loosening, darkening and becoming stained with blood. If fish are present to help consume the body, decomposition accelerates a hundred-fold. Fish, crabs and small marine animals quickly begin to feed on the soft parts of a corpse's face. the eyelids, lips and ears are the first to go, and then the eyes, nose and mouth. In some areas of the sea, large fish are scarce, so it is the smaller animal life that feeds on the remains. These small creatures, however, are quite efficient. Larger animals feed on the torso and extremities. So with all this said, it does seem plausible to be able to make a raft as they did in this portrayal. I would also direct you to a book I have read, called "Stiff: The Curious Lives of Human Cadavers ", which documents svereal ways in which cadavers are used in the name of scientific research, across several applications. The reason this came to mind was one of the chapters which deals in forensic description of how a human body decomposes in a natural setting, albeit on land, but still explains some of the processes which may further explain to you why they float as they do. I hope this answered your questions. Let us know if any new ones were spurred from this discussion... Tye
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