The blackboard was invented by James Pillans. He made it in 1801 and gave it the name, blackboard. It is made from the stone called slate. The chalk made from calcium sulphate is the thing you use, so you can write on it. In the early years of the twentieth century it was used in many schools. It came in different colors like green, brown and black. In the fifties most of the blackboards were colored green since researches have revealed that green is the color that gives a calming effect for the eyes. The green color also avoids the eyes from getting fatigued.

1. The first answer to the question why is the blackboard green is because one research revealed that the eyes of humans are very sensitive to anything that has green color. This is one of the main reasons why most creators of chalkboards preferred making them green instead of black. Studies also showed that the eyes' retina has two kinds of cells for light namely, rods and cones. There are around one hundred twenty millions rods in our eyes. The rods are the ones that help us develop scotopic visions. This vision helps us in seeing in a bright and dark room. The part of our eye that recognizes colors are the cones. There are seven million cones and some of them are green ones. The green cones are very sensitive to light and let our eyes get the best resolution, when we are looking or reading.

2. The second answer to the question why is the blackboard green is because of the fact that in many cultures around the world, this color is the symbol of hope. It is a color that most teachers associate with growth as well. For education it means that studying should have a big part of the growth process of every individual.

3. The third answer to the question why is the blackboard green is because of the rise of many groups all over the globe advocating for protection for the environment. There was at time when the movement for going green became popular. All of those movements also campaigned for the use of the color green.

4. The fourth answer to the question why is the blackboard green is because green let the rooms have a minimal stark image. The chalk marks on the green chalkboards are also not as obvious as to the black chalkboards. The people then started calling it chalkboards instead of blackboards because it of the change in the color and green became the official color in the fifties.

Today whiteboards are widely used than chalkboards because of the concern over the dust chalks give off but there are still a few schools and institutions which use because these days they are no longer made from slate and there are chalks now that do not give off dust.

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