The 18th of April is the 108th day of the year (Gregorian calendar) or 109th in a leap year.
The 18th of April is known as World Amateur Radio Day commemorating the anniversary of the creation of the International Amateur Radio Union in 1920
The 18th of April is also known as International Day for Monuments and Sites and was created on this day in 1983 by UNESCO (United Nations Educational, Scientific and Cultural Organisation)
The 18th of April is known as ‘Independence Day’ in the country of Zimbabwe to commemorate gaining their independence from the United Kingdom.
In Japan this day is known as National Invention day to commemorate the nation’s inventors.
Bangladesh joined the Commonwealth of Nations. After gaining its independence (on the 26th of March 1971) from Pakistan, Bangladesh joined India and Pakistan as a member of the Commonwealth of Nations on this day in 1972.
Albert Einstein died at the age of 76. The German born theoretical physicist was the father of general relativity and created of the worlds most famous equation E=MC2. His discoveries revolutionised the world of “modern physics” (Relativity and Quantum Mechanics). In 1916 Einstein published his ‘General theory of Relativity’ which described gravity as a property of space and time (spacetime) and he proposed that the properties of gravity, space and even time were relative to the speed of motion of the observer of the object in question. One of the most controversial ideas of this theory is that time actually slows down the closer you get to the speed of light, a theory now proven many times and is a pivotal part of satellite navigational technology. He also received the Nobel Prize in 1921 for his work on the ‘Photoelectric Effect’ which helped to establish Quantum Physics. The ‘Photoelectric Effect’ regards the transfer of energy from a light beam onto a metal surface which becomes heat. The theory suggested that with enough time, however strong the beam of light, enough energy should be transmitted to the metal to liberate one of its electrons from one of the atoms. In practice physicists found that this worked on some metals and not others and that an electron would eject with more energy dependant on the colour of the beam rather than the intensity. This perplexed physicists until 1905 when Einstein applied a previous theory by Max Planck. Plank had suggested that light beams (and all Electromagnetic radiation) were not a continuous flow of energy, as previously thought, but actually packets (quanta) of energy (like the way information is sent across the internet). When Einstein applied this theory he was able to explain why it didn’t matter the length of time that the light beam shone on the metal but it the individual photons (energy packets) had enough energy within them to cause an electron to escape. It even explained why the colour affected the energy the electrons ejected by was effected by colour rather than intensity. His most famous work was the idea that the mass of an object could be converted to energy or energy into matter. E = MC2 suggests that the amount of (potential) energy is equal to the mass of matter multiplied by the speed of light squared. This is used in nuclear weapons but also explain how the sun is able to produce so much power. Every time a hydrogen atom becomes a helium atom in the plasma of the sun, a little bit of mass is ‘lost’ and converted into energy. Einstein left an amazing legacy when he died on this day in 1955 and his contributions changed physics and our lives forever.