A monument in London was once a telescope and laboratory too!
It was 2nd September 1666 when a fire broke out in London’s Pudding Lane near London Bridge. This incident, which continued till 6th September, reducing 80% of the city to ashes and leaving over 70 000 people homeless, is known as the Great Fire of London. A monument was built as a memorial to the lives lost in London’s most enormous fire. Known as the Monument to the Great Fire of London, this well-known sight in London was constructed between 1671-1677. Inside the towering monument, there is a spiral staircase for visitors to reach all the way to the top. But this colossal construction is more than just a monument. The structure was used as a giant telescope and underneath it was a state-of-the art physics laboratory. Curious to know what the telescope was used for, or what research was carried on in the lab? Read on.
The Monument at a glance
The Monument to the Great Fire of London lies just a few meters from the London Bridge, between Monument Street and Fish Street Hill. This is the tallest isolated stone column (202 feet) in the world and has a balcony, a pedestal (21 square feet and 40 feet high) and a golden orb on the top, representing fire. The structure was constructed Sir Christopher Wren, a highly acclaimed English architect of time who also built London's St. Paul's Cathedral, and his friend Robert Hooke, an English polymath who was both a scientist and an architect. They intentionally designed the Monument such that it served as a memorial as well as a telescope for viewing the limited sky area visible through the column.
The telescope
When you enter the monument, you will see a spiral staircase that will take you to the top. This is the telescoping column. The basement of the monument contains the observation room. From this room, an astronomer can use an eyepiece to view the sky immediately overhead. Telescope lenses can be positioned at various heights above the ground depending on what is being studied. But why a telescope? While it may be difficult to imagine now, Hooke constructed this telescope monument to demonstrate that the Earth circles the Sun. Hooke believed that by creating a large enough telescope, he could confirm the validity of the hypothesis that is now universally accepted. Unfortunately, Hooke had to abandon his experiment midway, as the vibrations caused by surrounding traffic interrupted the experiment. Finally, in 1838, Hooke’s theory was proved by the German astronomer Friedrich Bessel.
A successful experiment
The physics laboratory was used for one successful experiment. Want to know what was it? Well, Hooke was interested in studying the effects of height on the pressure of the surrounding air. However, such an experiment would require tall structures, which were uncommon in 17th-century London. So, what did Hooke do? He used the monument. Hooke had carefully constructed the inside spiral staircase of the monument, making each step exactly six inches tall. This helped him to precisely calculate the variations in pressure, with equal intervals of height (six inches). Are you wondering what Hooke’s test results were? Well, he found that the mercury level (in the barometer) decreased by roughly a third of an inch between the bottom and top of the steps. This supported Hooke's notion that air pressure reduces as height increases. However, Giovanni Battista Baliani, an Italian scientist, had already proved this hypothesis three decades before Hooke. Once a hub of scientific experiments, the Monument now houses only a wireless router and a few sensors.