Stephen Gray (scientist) facts for kids

Stephen Gray (born December 1666 – died February 7, 1736) was an English scientist. He worked as a dyer and studied astronomy. Gray was the first person to carefully experiment with how electricity moves through different materials. Before his work in 1729, people mostly focused on making static charges and seeing their effects, like small shocks or glows.

Gray also figured out the difference between materials that let electricity pass through them (conductors) and those that do not (insulators). He also discovered action-at-a-distance, which is how an electrical charge can affect something without touching it. This is known as electrostatic induction.

Stephen Gray's Early Life

Stephen Gray was born in Canterbury, Kent, England. After some basic schooling, he started working with his father and older brother in the cloth-dyeing business. But Stephen was much more interested in natural science and especially astronomy.

He taught himself a lot about these subjects. He did this mainly by using the libraries and science tools of his wealthy friends. In those days, science was often a hobby for rich people.

Building His Own Telescope

Gray was very clever. He made his own lenses and built his own telescope. Using this telescope, he made several small discoveries, mostly about sunspots. People knew him for making very accurate observations.

Some of his findings were even published by the Royal Society. This happened thanks to his friend, Henry Hunt, who worked for the Society.

Working with John Flamsteed

Some of Gray's work caught the eye of John Flamsteed. Flamsteed was a relative of some of Gray's friends in Kent. He was also the first English Astronomer Royal. At the time, Flamsteed was building the new Royal Greenwich Observatory.

Flamsteed was trying to create a very detailed and accurate map of the stars. He hoped this map would help sailors figure out their exact location at sea. Gray helped him a lot with observations and calculations.

Challenges in the Science World

Gray and Flamsteed became close friends and wrote many letters to each other. However, this friendship caused problems for Gray in the official science world. Flamsteed was in a long disagreement with Isaac Newton. This fight became a big problem within the Royal Society, which Newton mostly controlled. Newton often kept Flamsteed and his friends out of the Society's activities for many years.

Gray worked for a while at the second English observatory being built in Cambridge. But the project was not managed well by Newton's friend, Roger Cotes. The observatory project eventually failed. This left Gray with no choice but to go back to his dyeing job in Canterbury.

Moving to London

Later, Gray became ill. He moved to London to help John Theophilus Desaguliers. Desaguliers was a supporter of Isaac Newton and sometimes demonstrated experiments for the Royal Society. Desaguliers worked as a science consultant. He gave lectures about new discoveries and ran a boarding house for gentlemen interested in science. Gray did not get paid by Desaguliers. Instead, he received a place to live in exchange for discussing science with the guests.

Desaguliers' boarding house was later torn down to build Westminster Bridge. This left Gray in a difficult situation. In 1720, with help from John Flamsteed and Sir Hans Sloane (who later became the President of the Royal Society), Gray got a special place at the Charterhouse. This was a home for gentlemen who had served their country and were now in need. It was also linked to a boys' school. While living there, Gray started experimenting with static electricity again. He used a glass tube that created static electricity when rubbed.

Discovering Electrical Conduction

One night, in his room at Charterhouse, Gray noticed something interesting. The cork at the end of his glass tube (which kept out moisture) attracted small pieces of paper when the tube was rubbed. Usually, the cork would not hold an electrical charge. But because of the weather and the materials, the cork was gathering a charge.

When he put a small stick of fir wood into the cork, the electrical charge appeared at the end of the stick. Then he put an ivory ball on the end of the stick, and the ball also attracted light objects. He tried longer sticks. Finally, he added a long piece of oily hemp string connected to the ivory ball.

Electricity as a Fluid

Through these experiments, Gray discovered that "electric virtue" (what they called electricity) was not just a small, static spark. Instead, it was like a fluid that could travel over a distance. The ivory ball at the end of the string still attracted light objects, just like the rubbed glass tube.

Over the next few days, he made his string longer. He found that electricity could travel from his balcony down into the courtyard below. He also learned that electricity could travel around bends in the string and that gravity did not affect it. He was also able to send charges to metal objects like a poker or a kettle. People at the time thought these metal objects could not create or hold a static charge. He also found that silk string would not carry the "virtue," but thicker hemp string and wire could.

Conductors and Insulators

Between June 30 and July 2, 1729, Gray made even more discoveries while visiting Kent. He visited Reverend Granville Wheler, a wealthy friend and member of the Royal Society. Together, they extended the electricity experiments. They ran a hemp string up and down a long gallery in Wheler's manor house, Otterden Place.

During this experiment, Gray and Wheler discovered something very important. They learned that they needed to keep their string (the "conductor") from touching the ground or the house wall. They used silk to hang the string. They noticed that if a metal wire was used to support the hemp string, all the "electrical virtue" disappeared. At first, they thought the thickness of the silk, string, and wire mattered. But later, they realized that silk itself did not conduct electricity well. So, they used only silk to support and insulate the hemp string, which was their main conductor.

The next day, they dropped the string from the house tower to the garden. Then they stretched it across a field for 800 feet. They used pairs of garden stakes with short pieces of silk to keep the hemp string from touching the ground. Wheler told his friends at the Royal Society about this. Gray wrote all the details in a letter to Desaguliers.

Understanding Electricity

From these experiments, people began to understand the role of conductors and insulators. These names were given by Desaguliers. Two French scientists, Abbe Nollet and C.F. du Fay, visited Gray and Wheler in 1732. They saw the experiments and went back to France. There, du Fay created the first full theory of electricity, called the "two-fluid" theory.

This theory was popular in Europe for a while. Later, English scientists John Bevis and William Watson improved upon it. They were in contact with Benjamin Franklin's group in Philadelphia. They came up with a "single-fluid/two-state" theory. This idea suggested that electricity was one fluid that could be in too much or too little supply. Watson later called these "positive" and "negative." These ideas fit the facts better, especially after the invention of the Leyden Jar. The single-fluid theory eventually became widely accepted.

Gray continued to make more electrical discoveries. One of the most famous was electrical induction. This is when you create an electrical charge in an object without touching it. This experiment was known as the "Flying Boy" demonstration. A boy was hung on silk ropes. Gray then brought his rubbed glass tube (which made static electricity) close to the boy's feet, but without touching him. Gray showed that the boy's face and hands could still attract small pieces of paper. Gray realized that the "electric virtue" was the same as lightning. This was many years before Franklin's famous kite experiment.

Recognition and Legacy

When Sloane took over the Royal Society after Newton's death, Gray finally received the recognition he deserved. Gray was too poor to pay the membership fees, so he was not a member of the Royal Society. Also, many of his experiments were used by Desaguliers in his demonstrations.

Sloane actively helped Gray. Gray received the Royal Society's first Copley Medal in 1731 for his work on conduction and insulation. He received a second Copley Medal in 1732 for his induction experiments. In 1732, the Royal Society also made him an honorary member. Stephen Gray died a few years later in 1736.

Stephen Gray's Impact

Even though his discoveries were very important, Gray did not get much credit for a long time. Some historians believe this was because of the arguments within the Royal Society and the strong influence of Newtonianism. By the time Gray's work was publicly recognized, experiments in electricity had moved on. People were more interested in the exciting things done by Franklin and others, like capturing lightning in their Leyden Jars. Gray's discoveries seemed less exciting by comparison. Because of this, some historians tend to overlook his work.

There is no monument to Stephen Gray, and he is not widely recognized for his scientific achievements. It is believed he was buried in a common grave in an old London cemetery. This area was for poor pensioners from the Charterhouse. In 2017, the School of Physical Sciences at the University of Kent in Canterbury started the Stephen Gray Lectures to honor him.

See also

In Spanish: Stephen Gray para niños