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why do we feel cold when we have a fever

It wouldnt be a St. Patricks Day celebration in the Windy City without 400,000 spectators crowding the banks of the Chicago River to ooh and aah at its (temporarily) emerald green tinge. But how do officials turn the water green? First, a bit of history: The dyeing tradition became an annual thing nearly 60 years ago, in 1962, but its real origins go back even further. In the early days of his administration as Mayor of Chicago, Richard J. Daley was a man on a mission to develop the citys riverfront area. There was just one problem: The river itself was a sewage-filled. In order to get to the bottom of the citys pollution problem and pinpoint the exact places where waste was being discarded into the waterway (and by whom), Daley authorized the pouring of a special green dye into the river that would allow them to see exactly where dumping was occurring. Fast-forward to late 1961 when Stephen Baileypart of the Chicago Journeymen Plumbers Local, the citys St. Patricks Day Parade chairman, and a childhood friend of Daleyswitnessed a colleagues green-soaked coveralls following a day of pouring Daleys dye into the Chicago River. That gave Bailey
: If they could streak the Chicago River green, why not turn it all green? Three months later, revelers got their first look at an -colored river when the city poured 100 pounds of the chemical into the water. They got a really good look, too, as the river remained green for an entire week. Over the next several years, the same practice was repeated, and again it was carried out by the Plumbers Local. The only difference was that the amount of dye used was cut in half over the next two years until they finally arrived at the : 25 pounds of dye = one day of green water.

Unfortunately, the dye that was intended to help spot pollution was an oil-based fluorescein that many environmentalists was actually damaging the river even more. After fierce lobbying, eco-minded heads prevailed, and in 1966 the parade organizers began using a powdered, vegetable-based dye. While the exact formula for the orange powder (yes, it's orange until it's mixed with water) is kept top-secretin 2003 one of the parade organizers a reporter that revealing the formula would be akin to telling where the leprechaun hides its goldthere are plenty of details that the committee lets even non-leprechauns in on. The dyeing process will at 9 a. m. on the morning of the parade, Saturday, March 17 (it's always held on a Saturday) when six members of the local Plumbers Union hop aboard two boats, four of them on the larger vessel, the remaining two on a smaller boat. The larger boat heads out onto the water first, with three members of the crew using flour sifters to spread the dye into the river. The smaller boat follows closely behind in order to help disperse the substance. (The to catch a glimpse is from the east side of the bridge at Michigan Avenue, or on Upper and Lower Wacker Drive between Columbus and Lake Shore Drives. ) Approximately 45 minutes later, voila, the Chicago River is greenbut dont expect it to stay that way. These days, the color only sticks around for about. Which is roughly the same amount of time it takes to get a perfectly poured pint of Guinness if you venture out to an Irish pub on St.

Patricks Day. Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at. This question was sent in by a reader from Dublin. We all know what, it s like, the thermometer says our temperature is up but all we want to do is wrap ourselves in blankets and sit near a warm fire. So why is that? Firstly, we need to take a look at what our normal body temperature is and how it is regulated. BODY TEMPERATURE AND REGULATION Our body temperature is usually between 36. 1 and 37. 2C. This varies depending on age, health, how the temperature is taken and a variety of other factors. HOW DOES OUR BODY CONTROL AND MAINTAIN THESE TEMPERATURES? It uses a thermostat. Our internal thermostat is located in a part of our brain, called the hypothalamus. It is set at 36. 8C. If our body temperature goes above this we do certain things to cool down; if our temperature drops, we need to warm up. COOLING DOWN The body uses two main systems to cool down. One is that it sweats; body heat transfers to the sweat (or any water on the body) and the heat is removed from the body when the sweat is wiped away or evaporates. This also explains why we feel cold coming out of a swimming pool, even on a very hot day. The flow of blood to vessels that sit just below the skin also increases. This brings heat to the surface of the body to be released. This explains why we often have a red face when we are hot. HEATING UP If our body temperature drops below that set on our internal thermostat then we need to heat up.

This time we reduce the blood flow to capillaries near the body s surface, to reduce the amount of heat lost through our skin. We also get certain muscles moving to burn some energy and heat up the body. USING HEAT AS A WEAPON Often, when our body is attacked by a microorganism, like a virus or bacteria, it responds by altering the temperature of our body. Most viruses and bacteria grow best in warm temperatures; 37C is ideal for many microorganisms. Unfortunately this is around the normal temperature of the human body. So what does the body do to try to stop these infecting organisms from growing, reproducing and taking over? It turns up the thermostat. So the fever we experience is created deliberately, to try to suppress an infection. WHY DO WE SHIVER? When the thermostat is turned up, our normal body temperature is lower than the new setting and we feel cold. The body kicks into action, bringing the temperature up. To do this it gets certain muscles to start to contract involuntarily. This burns up energy within the body, giving off heat and increasing the body s temperature. The involuntary muscle contractions are what we call shivering. Usually the increase in temperature is enough to stop the infection from spreading within the body. Once our immune system kills of the infection and our body is safe, then the thermostat is reset to 36. 8C and out body temperature drops back down to normal again. Naomi is a science communicator and mother to three inquisitive children. She can be found at sciencewows. ie Feel free to email your questions to

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