Why is the earth heated by radiation as opposed to conduction?

Answer 1

You have the Sun over there in space and the Earth over here in space. OK?

For conduction to work the two bodies must be physically touching - the sun and the earth are not in direct contact (there is space between them) so the Sun's heat can not be conducted to Earth.

For convection to work you need a fluid or air round the two objects - the sun and the earth are separated by the vacuum of space (no fluid or air) so the Sun's heat can not be convected to the Earth.

The third means of transferring heat is by radiation, this travels across space just fine and thus it is the means by which the Sun's energy reaches the Earth (as sunlight).

Answer 2

If heat travels by conduction, a cold object would have to be in physical contact with a heat source (such as a hot object), like pressing your hand against a hot radiator. Since the Earth is not touching the Sun, this is not possible.

Convection as a method of heat transfer relies on the flow of particles from a hot region to a cold region or vice versa. For example, the air above a radiator is warm because hot air around the radiator rises in the cold air around it (or, to look at it the other way, cold air falls). If the Earth were heated by the Sun via convection, hot particles would have to travel all the way from the Sun to the Earth. This doesn't happen, it's only the heat energy that radiates.

So, as you correctly assume, heat from the Sun travels to Earth only by radiation.

Answer 3

If the earth depended on conduction to heat it, we would all be out of luck. Conduction is the

process of heat flowing through a material medium, and there isn't any of that between the

sun and us, so we receive zero heat from the sun by conduction. If that's all there was, we

would need very heavy coats. And good flashlights too.

Answer 4

Energy from the sun must travel through the vacuum of space to reach the earth. Only via radiation can solar energy reach the earth. Conduction and convection both require matter to transfer the thermal energy. Let's look at a couple of examples.

A pan gets hot on the upper surface where we cook because heat from the bottom of the pan travels by conduction up through to the top. The air in the kitchen gets warm when baking because convection carries thermal energy from the oven out into the kitchen. As space is a vacuum, neither conduction or convection is effective in the transfer of thermal energy between the sun and earth.

Answer 5

The Earth is heated by radiation from the Sun because of the vast distance between the Earth and the Sun, which prevents direct conduction of heat. Radiation is a more efficient way to transfer heat over such large distances through the vacuum of space. Conduction requires direct contact between objects, which is not feasible across the vastness of space.