Light and heat are linked by electromagnetic waves. When sunlight strikes an object, it activates the motion of particles and is converted into thermal energy, raising the temperature.
The Sun, Light and Heat
Why is the sun’s rays warmer than the shade? No matter how hot the sun is, how can it warm the objects on Earth that are so far away through empty space without a suitable medium? To understand this, we must first clearly understand the nature of heat and light.
Historical understanding of heat
Until the middle of the 18th century, scientists believed that heat was the action of an invisible substance – a “calor” – and explained the melting of solids and the evaporation of liquids as a kind of chemical action between the calor and the particles that make up the solid or liquid. However, thanks to the research of Rutherford, Meyer and Joule, the existence of “heat” was denied and the concept of “thermal energy” was established instead. It was Clasius who specifically identified the nature of heat, arguing that the thermal energy of a gas is the kinetic energy of the gas molecules, and that temperature therefore indicates the degree to which the gas molecules are moving. In addition, Maxwell showed that the speed of motion of gas molecules at a constant temperature is distributed around the average value, which ultimately revealed that heat is the “average kinetic energy of the particles that make up an object. The particles of all objects are constantly oscillating or rotating about the average position, and temperature is a measure of the magnitude of this kinetic energy.
Electromagnetic Theory and Light
To understand the nature of light, it is also necessary to understand electromagnetic theory, because light is a type of electromagnetic wave. The existence of electromagnetic waves was deduced through Ampere’s experiment, which showed that electric current (electric field) creates a magnetic field, Faraday’s experiment, which confirmed that electric current is created in a magnetic field, and Maxwell’s theory, which summarized these experiments. Ampere confirmed that a magnetic field is created when current is passed through a wire placed side by side, and that a magnet with strong magnetism is created when current is passed through a coil made by winding a wire into a cylinder, called a “solenoid”. Faraday confirmed that when a magnet is passed through a coil without current, an electric current is generated from the change in the magnetic field of the magnet. An electric field produces a magnetic field, and a magnetic field produces an electric field. Maxwell summarized the results of these experiments and established the theory of “Maxwell’s equations”, from which the existence of electromagnetic waves could be deduced.
The Principle of Electromagnetic Wave Propagation
When a current is suddenly applied to a wire, or the strength of the current is changed, a magnetic field is created in the surrounding area, which generates a secondary electric field, which in turn generates a secondary magnetic field. Electromagnetic waves are waves that propagate as the process of an electric field creating a magnetic field and that magnetic field creating another electric field repeats itself. After calculating that the speed of these waves is equal to the speed of light, Maxwell came to the brilliant conclusion that “light itself is also a kind of electromagnetic wave. Unlike mechanical waves, in which matter actually vibrates like sound, light is an electromagnetic wave that propagates by repeating continuous changes in electric and magnetic fields. Scientists later confirmed that electromagnetic waves can propagate without a medium, which explains how sunlight can travel through empty space.
Propagation and Transfer of Solar Energy to Earth
What comes from the sun is not heat particles, but electromagnetic waves that, when they hit an object, interfere with the object’s vibrations. And these vibrations interact with the particles of matter, causing the particles to move, which in turn raises the temperature of the matter. Through this process, the sun’s light can travel through the universe without a medium and warm objects on Earth.
The temperature difference between the sunny side and the shady side
The temperature difference between the sun and the shade can be explained by this principle. In the sun, electromagnetic waves from the sun hit objects directly, causing their particles to vibrate strongly and increase their temperature. In the shade, however, the sun’s rays do not hit the objects directly, so this process does not occur and the temperature remains relatively low. In addition, the degree to which an object absorbs solar energy varies depending on the object’s color and properties, so the surface temperature of an object can vary even with the same amount of sunlight. For example, a dark object absorbs more solar energy and heats up faster, while a light object has a higher reflectivity and heats up less.
Conclusion
Using these principles, we can understand that the sun is warmer than the shade. The sun’s energy is transmitted in the form of electromagnetic waves, which travel through the universe without a medium and heat objects on Earth, and sunlit areas become warmer. The process of understanding natural phenomena through these scientific principles is very interesting and provides a deeper understanding of phenomena that can be easily observed in everyday life.
