What happens when the angle of the Sun is perpendicular to the Earth's surface? 


2 Answers

Samuel Chiltern Profile
Samuel Chiltern answered
I just need to quickly define perpendicular before I answer your question, to make sure that we're clear about what this term means.

Something is said to be perpendicular if it stands at a right-angle (90 degrees) to something else. Try to imagine the Earth's surface as a flat plane, with a ray of light from the Sun hitting it head-on.

The Influence of The Sun's Angle Relative to the Earth
The intensity of sunlight as it hits the Earth has a direct relationship with the angle the light approaches from.

The Sun's radiation is most intense at the higher angles (between 65 - 90 degrees). You will have witnessed the effects of this intensity if you have stood outside at high-noon on a hot day!

The lower angles of incidence cause the energy from the Sun to be more spread out, which is why mornings and the evenings are the coolest times of day.

The Earth follows a two-dimensional path as it orbits the Sun. A single trip is called an Earth revolution, and takes 365.26 days, or one year.

The Earth's axis is set at an angle of 23.5 degrees to this path, which means that the relative position of the axis to the Sun changes throughout the year. This is what accounts for the change in seasons, and is also responsible for the relative changes in the Sun's height above the horizon.

It is this continual shifting that leads to changes in the amount of time during which any one particular point on Earth is exposed to sunlight. Crucial to your question is the fact that the intensity of that light also varies depending upon the Sun's height in the sky, and the consequent angle at which the rays of light hit the Earth.
Oddman Profile
Oddman answered
Shadows are as short as they will ever be. Energy absorbed per unit area is as large as it will ever be. The local solar time is noon.

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