John Joly facts for kids
Quick facts for kids
John Joly
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John Joly
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| Born | 1 November 1857 Millgrove, Bracknagh, County Offaly, Ireland
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| Died | 8 December 1933 (aged 76) Dublin, Ireland
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| Nationality | Irish |
| Known for | radiotherapy cohesion-tension theory |
| Awards | Boyle Medal of the Royal Dublin Society (1911) Royal Medal of the Royal Society of London (1910) Murchison Medal of the Geological Society of London (1923) |
| Scientific career | |
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John Joly (born November 1, 1857 – died December 8, 1933) was a smart Irish scientist. He was a physicist and a geology professor at the University of Dublin. Joly is famous for two main things. First, he helped create radiotherapy, a way to treat cancer using radiation. Second, he found new ways to figure out how old rocks and the Earth are by looking at radioactive elements inside them. This method is called uranium–thorium dating.
Contents
Life and Work
John Joly was born in Holywood House, a rectory in Bracknagh, County Offaly, Ireland. He was a second cousin to Charles Jasper Joly, who was an astronomer.
Early Education and Career
In 1876, Joly started studying at Trinity College, Dublin. He graduated in Engineering in 1882, coming in first place. He also earned special certificates in different engineering fields. At the same time, he achieved top honors in modern literature.
After graduating, Joly worked as a demonstrator in the Engineering and Physics departments at Trinity College. In 1897, he became the Professor of Geology and Mineralogy. He held this important position until he passed away in 1933. Joly loved sailing and even served as a Commissioner for Irish Lights, which manages lighthouses.
Joining the Royal Dublin Society
Joly became a member of the Royal Dublin Society in 1881 while he was still a student. He often shared his scientific papers with the society. His very first scientific paper was published in 1883. It was about how to use weather instruments from a distance. Over his lifetime, he published more than 270 scientific papers!
Key Scientific Discoveries
John Joly made many important contributions to science. He explored ideas in physics, geology, and even biology.
Understanding Ice
In 1886, Joly suggested a theory about why ice is slippery. He thought that when pressure is put on ice, it makes a thin layer of liquid water. This water layer then allows things to slide. While scientists have updated this idea since then, Joly's theory was the first to try and explain why ice has such low friction.
Estimating Earth's Age
On May 17, 1899, Joly presented a paper called "An Estimate of the Geological Age of the Earth." He suggested a new way to calculate the Earth's age. He proposed using the amount of sodium that had built up in the oceans.
Joly figured out how fast the oceans would have collected sodium from erosion (the wearing away of land). Based on this, he estimated that the oceans were about 80 to 100 million years old. This paper was published quickly. Even though this method was later found to be not entirely accurate, it greatly changed how people thought about the Earth's age at the time.
Radioactivity and Earth's Age
In 1903, Joly wrote an article in Nature magazine. In it, he talked about using radium to date the Earth. He then studied how much radioactive material was in the Earth's crust. This helped him create a theory about the Earth's heat cycles. He also looked at radioactive parts of rocks to figure out their age.
Working with another famous scientist, Sir Ernest Rutherford, Joly used radioactive decay in minerals. In 1913, they estimated that the Devonian period (a time in Earth's history) started at least 400 million years ago. This estimate is very close to what modern scientists believe today!
In 1908, Joly gave a speech called "Uranium and Geology" at a meeting of the British Association for the Advancement of Science. He explained how radioactive materials in rocks help create the Earth's internal heat.
Water Movement in Plants
Joly also worked with his friend Henry Horatio Dixon. Together, they proposed the cohesion-tension theory. This theory explains how water moves upwards in tall plants, from the roots to the leaves. Scientists now believe this is the main way plants get water.
Cancer Treatment
In 1914, Joly developed a way to get radium out of materials. He then used this radium to treat cancer. As a leader at Dr Steevens' Hospital in Dublin, he worked with Walter Stevenson. They created new radiotherapy methods. They also helped set up the Irish Radium Institute at the Royal Dublin Society. Here, they pioneered the "Dublin method," which used a hollow needle for deep radiotherapy. This technique later became used all over the world. The Radium Institute also provided small tubes of radon to hospitals for treating tumors.
Inventions and Innovations
Joly was also a talented inventor. He created several useful scientific tools:
- A photometer to measure how bright light is.
- A meldometer to measure the melting points of minerals.
- A special steam calorimeter to measure how much heat different materials can hold.
- A constant-volume gas thermometer.
All these inventions are named after him. He also created one of the first successful color photographic processes, called the Joly colour screen. It was the first method that could produce color pictures from a single photographic plate.
Awards and Legacy
John Joly received many honors for his scientific work:
- In 1892, he was chosen as a Fellow of the Royal Society of London.
- He won the Boyle Medal from the Royal Dublin Society in 1911.
- He received the Royal Medal from the Royal Society of London in 1910.
- In 1923, he was awarded the Murchison Medal from the Geological Society of London.
He also received honorary degrees from several universities, including the National University of Ireland, the University of Cambridge, and the University of Michigan.
After he passed away, his friends collected money to create a memorial fund. This fund is still used today to support the annual Joly Memorial Lectures at the University of Dublin. Sir Ernest Rutherford gave the first of these lectures in 1935. Joly is also remembered by the Joly Geological Society, a student geology club started in 1960.
In 1930, a sculptor named Oliver Sheppard was asked to make copies of a bust (a sculpture of his head and shoulders) of Joly for Trinity College Dublin and the Royal Dublin Society.
In 1973, a crater on the planet Mars was named in his honor.
See also
In Spanish: John Joly para niños
