[00:08.59]Great scientists
[00:12.25]John snow defeats "king cholera"
[00:19.38]John snow was a well-known doctor in London---
[00:25.42]so famous, indeed, that he attended queen Victoria to ease the birth of her babies.
[00:33.46]But he became inspired when he thought about helping ordinary people exposed to cholera.
[00:42.21]this was the most deadly disease of its day.
[00:47.78]Neither its cause, nor its cure was understood.
[00:54.23]So many thousands of terrified people died every time there was an outbreak.
[01:01.49]John snow wanted to use his knowledge to help solve this problem.
[01:08.55]He knew it would never be controlled until its cause was found.
[01:15.31]He got interested in two theories explaining how cholera killed people.
[01:23.07]The first suggested that cholera multiplied in the air without reason.
[01:30.15]A cloud of dangerous gas would float around until it found its victims.
[01:37.91]The second suggested that people absorbed this disease into their bodies with their meals.
[01:45.85]From the stomach the disease attacked the body quickly
[01:52.01]and soon the affected person was dead.
[01:56.98]He believed in the second theory but needed to prove he was correct.
[02:04.21]So when another outbreak hit London in 1854,
[02:10.46]john snow was ready to test these two theories.
[02:16.02]As the disease spread quickly through the poor neighbourhoods,
[02:22.26]john snow began to gather the information.
[02:27.25]He found that in two particular streets,
[02:32.82]the cholera outbreak was so severe that more than 500 people had died in 10 days.
[02:41.88]He determined to find out why.
[02:46.24]He marked on a map where all the dead people had lived.
[02:52.62]Here it is: the map gave a valuable clue about the cause of the disease.
[03:00.95]Many of the deaths were near the water pump in broad street
[03:07.79]( especially numbers 16,37.38 and 40 broad street).
[03:16.26]John snow also saw that some houses
[03:22.92](such as 20 and 21 broad street and 8 and 9 cambridge street)
[03:31.07]had had no deaths.
[03:35.12]He discovered that these families worked in the pub at 7 cambridge street.
[03:42.69]They were given free beer and so had not drunk the water from the broad street pump.
[03:50.74]It seemed the water was to blame.
[03:55.31]Next, john snow looked into the source of the water for these two streets.
[04:03.25]He found that it came from the river,
[04:08.01]which had been polluted by the dirty water from London.
[04:13.15]Immediately john snow told the astonished people in broad street
[04:21.02]to remove the handle from the water pump so it could not be used.
[04:27.99]Soon the disease began to slow down.
[04:33.84]John snow had shown that cholera was spread by germs and not in a cloud of gas.
[04:42.38]In addition, he found two other deaths in another part of London
[04:49.15]that were linked to the broad street outbreak.
[04:53.90]A woman, who had moved away from broad street,
[04:58.87]liked the water so much
[05:02.81]that she had had it delivered from the pump to her house every day.
[05:09.05]Both she and her daughter, who often visited her,
[05:15.53]died of cholera after drinking the water.
[05:20.08]With this extra evidence
[05:25.12]john snow was able to announce with certainty
[05:30.16]that polluted water carried the disease.
[05:35.41]To prevent this from happening again,
[05:40.66]john snow suggested that the source of all water supplies be examined
[05:48.13]and new methods of dealing with polluted water be found.
[05:53.88]The water companies were also instructed not to expose people to polluted water anymore.
[06:02.34]Finally "king cholera" was defeated.
[06:08.01]Reading and writing
[06:17.86]Copernicus' revolutionary theory
[06:23.32]Nicolaus Copernicus was frightened and his mind was confused.
[06:31.78]Although he had tried to ignore them,
[06:36.75]all his mathematical calculations led to the same conclusion:
[06:43.72]that the earthe was not the center of the solar system.
[06:49.68]Only if you put the sun there did the movements of the other planets in the sky make sense
[06:58.61]Yet he could not tell anyone about his theory
[07:04.67]as the 'powerful Christian church would have punished him for even suggesting such and idea.
[07:13.42]They believed god had made the world a
[07:18.99]and for that reason the earth was special
[07:24.26]and must be the center of the solar system.
[07:29.41]The problem arose
[07:34.06]because astronomers had noticed that some planets in the sky
[07:40.72]seemed to stop,
[07:44.27]move backward and then go forward in a loop.
[07:49.55]others appeared brighter at times and less bright at others.
[07:56.50]this was very strange if the earth was the center of the solar system
[08:03.97]and all lanets went round it.
[08:09.12]Copernicus had thought long and hard about these problems
[08:16.59]and tried to find an answer.
[08:20.85]He had collected observations of the stars
[08:26.31]and used all his mathematical knowledge to explain them.
[08:32.26]But only his new theory could do that.
[08:37.90]So between 1510 and 1514 he worked on it.
[08:45.84]Gradually improving his theory until he felt it was complete.
[08:53.00]In 1514 he showed it privately to his friends.
[09:00.08]The changes he mande to the old theory were revolutionary.
[09:07.24]He placed a fixed sun at the center of the solar system
[09:14.37]with the planets going round it and only the moon still going round the earth.
[09:22.42]He also suggested that the earth was spinning
[09:27.77]as it went round the sun and this explained changes in the movement of the planets
[09:35.82]and in the brightness of the stars.
[09:40.68]His friends were enthusiastic and encouraged him to publish his ideas,
[09:48.62]but Copernicus was cautious.
[09:53.48]He did not want to be attacked by the Christian church,
[09:59.14]so he only published it as he lay dying in 1543.
[10:06.69]Certainly he was right to be careful.
[10:12.47]The Christian church rejected his theory,
[10:17.43]saying it was against god's idea and people who supported it would be attacked.
[10:25.01]Yet copernicus' theory is now the base on which all our ideas of the universe are built.
[10:35.14]His theory replaced the Christian idea of gravity,
[10:41.31]which said things fell to earth because god created the earth
[10:47.65]as the center of the universe.
[10:51.81]Copernicus showed this was obviously wrong.
[10:57.16]Now people can see that there is a direct link
[11:03.72]between his theory and the work of Isaac Newton,
[11:09.78]albert Einstein and Stephen hawking |