The following essay is part of a 5 part series to help you understand the sun and your interaction with it for optimal health. It is designed to empower you as a critical thinker and inspire you to practice sun smart habits. In this third part we will be learning all about the sun and its association with our planet.

In part 2 of this series—get to know your skin—we learned about our skin and how it is affected by the UV radiation from the sun. We also examined and became informed about the different types of skin cancer and how we can increase or decrease our risk of them. In this essay we continue with part 3 where we will get to learn about the sun.

In this part we will first explore the basics of how the sun works. We will then go on to understand the difference between UV-A and UV-B rays. We will then move on to understand the differences in solar radiation throughout the world, in different seasons and at different times of the day. We will finish off by connecting the pieces we have covered thus far in how they work for or against us when it comes to safe sun exposure.

Get to Know the Sun

Our sun is at the center of our solar system. It is what gives our Earth its natural light and warmth. The sun is a star – some of us are always surprised to hear this, which means it follows a certain life cycle like other stars. We see it in the form that we do, as it is the closest star to us – only about 8 light minutes away versus hundreds of light years away as are the other stars we see in the night sky.

It is estimated that the sun has “burned” now for over 4.5 billion years and is projected to do so for the next 5 billion years. It is mostly made up of the gases hydrogen and helium, but due to its massive size, tightly holds those gases around its core, hence the round shape.

The sun does not burn like a typical combustion reaction here on Earth but like a reaction that can be found in a nuclear reactor. The nuclear reactions make its energy and the immense movement of the gases cause magnetic fields. The sun works on the principle of nuclear fusion where it forces hydrogen atoms to come together creating the gas called helium and free energy.

The reason why the sun emits “radiation” is because in that reaction which synthesizes the helium, there is a neutron transfer in the cores of the hydrogen atoms. And whenever there is a neutron added or lost from an atom, there is the possibility of that substance becoming radioactive. That is similar to the technology most of our present day nuclear reactors use to generate energy.

The energy produced by the sun is emitted in various forms like: visible light, ultraviolet light, infrared, x-rays, gamma rays, microwaves and radio waves, which are considered to be electromagnetic radiation.

We are fortunate that our atmosphere blocks some of the visible and infrared radiation, almost all the ultraviolet rays, and all the x-rays and gamma rays. Nearly all of the radio energy reaches Earth’s surface. If we lose the precious layers of protection in our atmosphere, more of the damaging UV rays and other types of radiation will be able to reach us.

We have to remember that as scary as the sun has been made out to be by some sources, without the sun the Earth would not exist as we know it. It would not be able to sustain life as all plants rely on the sun to sustain themselves and ultimately us. If the sun goes, the plants go and hence we stand no chance of survival. And in our modern way of life today, many of us do cut ourselves off from the sun and often do not realize the disservice we are doing ourselves when it comes to all areas of our health—mental, emotional and physical.

What is the difference between UV-A and UV-B rays?

UV radiation is virtually the same whether is comes from natural sources like the sun versus artificial sources like tanning beds. UV radiation is made up of three types: UV-A, UV-B and UV-C radiation. The main difference between these three is their significant wavelengths.

UV-A radiation is further subdivided into UV-A-I and UV-A-II. The Earth receives most of its radiation from this source.

This type of radiation penetrates deeply as it has the longest wavelength, but generally does not cause sunburns. It is hence however still dangerous as the deep penetration leads to DNA mutations causing cancer. This type of radiation can also destroy the vitamin A in our skin.

UV-A gives a quick tan that lasts for days.

UV-B radiation is stronger compared to UV-A radiation as it is quicker to affect and damage our skin. It is also known to have a negative effect on our immune system by reducing its function. This is the main culprit for our sun burns and skin cancers as it directly mutates our skin’s DNA.

The positive part of UV-B radiation is that induces the synthesis of vitamin D in our skin. This type however, can also destroy vitamin A in our skin.

Aside from immediate sunburn, UV-B gives a slow tan that develops over several days as the skin continues to try to protect itself from the incurred damage.

UV-C radiation is the third type of UV radiation. It is the highest energy and most dangerous radiation, but we never hear about these rays as they are almost completely absorbed by the ozone layer and hence pose minimal health risk. If one was exposed to this, it would have the most damaging effect on the cornea of the eye.

All three types of radiation damage collagen and induce premature aging.

How is Solar Radiation affected by the seasons?

In learning about the sun, we have to be aware of the fact that indeed the sun gives us different strengths of solar energy depending on the seasons.

Since the Earth is tilted and rotates at an angle of 23.5°, different parts of the Earth get different intensities of the solar radiation at different parts of the year.

Examine the following diagram:


It takes the Earth 365 days to rotate once around the sun, and since it is rotating on an angle, this accounts for the presence of seasons and different strengths of the sun.

In the Northern Hemisphere, we are tilted towards the sun during the late spring to early fall months and hence experience warm temperatures then as we are directly facing the sun. As the Earth rotates around the sun, the Northern Hemisphere experiences the cold weather as the tilt places the Northern part furthest at this point from the sun.

In the Southern Hemisphere, there is an opposite occurrence in the seasons. During the months of October to April, it is then that the Southern Hemisphere is closest to the sun. During the months then of April to October it is then that the Southern Hemisphere is tilted furthest from the sun and hence experiences the coldest temperatures.

The equatorial regions are the least affected by the Earth’s rotation as that is the part of the Earth that always seems to “stick out” naturally. It is never really tilted further or closer away from the sun, but always in its direct path.

Hence, if you live in the Northern Hemisphere especially, you have to be aware that the sun does shine with different intensities, and because that part of the Earth experiences the most drastic season changes, one must be even more careful with their sun exposure there. This is opposite to the equatorial regions where the intensity is rather constant and humans there have evolved better to adapt to those conditions.

How is Solar Radiation affected by the time of the day?

It takes the Earth 24 hours to rotate itself once fully. During this time it will be facing the sun at various degrees.

The Earth rotates east and hence the sun is first visible on the east side of wherever you live. We know from an early age that the sun rises in the east and sets in the west. At these first moments the sun is considered to be low and at an angle. As the day proceeds and the Earth continues to rotate, the sun appears to “rise” higher and higher. Hence at mid-day the sun is at the highest point for that day and one gets most exposure from it, as you are in its direct path regardless of your location.

Ultimately to understand how the seasons and time of day affect sun intensity you have to remember that the sun is doing a “double rotation“. First picture the Earth rotating and then picture that while it is rotating it is moving around in an elliptical pattern around the sun.

Is the Sun really stronger today worldwide?

The quick answer is – yes! That is why we can no longer hide behind the excuse of “when I was your age I was outside all day and nothing happened”. Times have changed and it is not so much that the sun has changed – but that our atmosphere has changed. Well to be scientifically correct, our atmosphere has not changed itself, we changed our atmosphere. Scientists have noted however that the sun too has been burning more brightly in the past 60 years especially. See study here.

So what happened? Well for starters one of the most important layers of our atmosphere – the stratosphere contains a layer of ozone, which we know as our “ozone layer“. Over the past few decades this layer, which absorbs most of the harmful radiation of the sun has gotten damaged thanks to the thousands of chemicals that we emit into the air. This layer has not only gotten thinner but has also incurred some holes, where the sun was able to directly penetrate through.

The largest holes have opened up over the Antarctic. However the good news is that as soon as the world realized we were losing this precious ozone, various bans and chemical changes were made and today the ozone layer is in the state of recovery.

Without the ozone layer the harmful radiation would be so bad that we would literally not be able to leave our homes without full coverage.

You can read the article from Science Daily on how the ozone problem is on the mend.


The sun therefore is an important energy source for our planet, one without which, we could not live. However, the sun does emit radiation and whatever our atmosphere cannot absorb passes down to us and is capable of mutating our DNA from which cancers result.

Our big challenge then becomes how to maximize the effects of the sun, while minimizing the damage that it can cause and this is what we will wrap up this series with in part 5.

In the next article we will be looking at getting to know sunscreens and why you may be incurring more damage from using them sometimes, than benefits.

5 Part Sun Smart Series

Part 1 – Get to know the UV index

Part 2 – Get to know Your Skin

Part 3 – Get to know the Sun

Part 4 – Get to know Sunscreen

Part 5 – Summary: Maximize the Benefits, Minimize the Risks