The question asks about the primary method by which the heat of the sun reaches us on Earth. To understand this, we need to look at the different ways heat can be transferred.

Heat Transfer Modes

There are three main modes of heat transfer:

• Conduction: This mode involves the transfer of heat through direct contact between particles. Heat energy moves from hotter parts of an object to colder parts, or from a hotter object to a colder object when they are touching. Conduction requires a medium, like a solid or a liquid, where particles can vibrate and transfer energy to their neighbors.
• Convection: This mode of heat transfer occurs in fluids (liquids or gases). It involves the movement of the fluid itself, carrying heat energy along with it. Hotter, less dense fluid rises, while colder, more dense fluid sinks, creating a convection current. This method also requires a medium.
• Radiation: This mode of heat transfer does not require any medium. Heat is transferred in the form of electromagnetic waves (like infrared waves, visible light, etc.). These waves can travel through a vacuum, as well as through gases and some liquids and solids. When these waves hit an object, their energy is absorbed and converted into thermal energy, making the object warmer.

Sun's Heat Reaching Earth

Now, let's apply these concepts to how the heat of the sun reaches Earth:

• The space between the Sun and the Earth is largely a vacuum. This means there is very little matter (particles) for heat to be transferred through by conduction or convection.
• Since conduction and convection both require a medium for heat transfer, they cannot be the primary way the sun's heat travels through the vast emptiness of space to Earth.
• Radiation, on the other hand, does not require a medium. The Sun emits enormous amounts of energy as electromagnetic radiation, including visible light, ultraviolet rays, and infrared radiation (which we perceive as heat). These electromagnetic waves travel through the vacuum of space at the speed of light.
• When this solar radiation reaches Earth, it is absorbed by the atmosphere, land, and oceans, which then convert the electromagnetic energy into thermal energy, causing our planet to warm up.

Therefore, the primary method by which the heat of the sun reaches us is through radiation.