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Friday, Aug. 8, 2025

The Science of Feeling Happy Under the Sun

The Science of Feeling Happy Under the Sun

Reading time: about 5 minutes

Cornellians have become experts on taking on sunny days in Ithaca — especially after a frigid and long winter. From sitting out on Libe Slope soaking up the sun, throwing frisbees on the Arts Quad or just working and chatting outside — Cornell loves the sun. 

Ithaca gets about 155 days of sunlight in 365 days, a 42.5 yearly percentage. Compare that to the University of Florida located in Gainesville, Florida, which got 224 sunny days in 2024.

But why do humans enjoy the sunshine so much? For starters, the sun provides us with Vitamin D, which promotes calcium absorption to strengthen our bones, reduces inflammation and assists in the regulation of processes like cell growth and immune response. This occurs because the sun's ultraviolet B rays interact with a protein called 7-DHC in your skin which is converted to the active form of vitamin D — vitamin D3. 

Vitamin D is also only present in low amounts in our foods naturally, which makes exposure to sunlight or daily supplementary vitamins crucial.  

Sunlight is an electromagnetic type of energy and falls in the visible spectrum, 380 to 700 nanometer wavelengths, of what humans are able to see. According to Prof. Adam Anderson, psychology, the “rainbow of light” we are able to see gives us an idea of why humans enjoy seeing the sun so much!

“[Sunlight] ranges from the short wavelength and high energy violet to longer wavelength lower energy red — imagine a rainbow, which is [an] expression of how our brains interpret light as color,” Anderson said. “[My lab] has shown that each of [our] brains have special sensitivity to different colors.” “Beyond being a source of visual experience, colors also activate reward circuits in our brains to differing degrees and this influences our motivations and emotions.”

Notably, there is a link between sunlight and serotonin as a decrease in the exposure to sunlight is associated with lower serotonin levels. Serotonin is a neurotransmitter and hormone that boosts mood and makes you feel calm, happy and content. And when you are in the sun, serotonin levels increase and cause you to feel happier.  

“More daylight is associated with a more positive mood and less depression,” Anderson said. “This does not mean the most depressing day on campus is the winter solstice.” “It is just one of many factors that can regulate our mood, like spending time with people we care about and having gratitude for all that we have.” “But knowing this tendency for lower mood with restricted light, we can take special measures to boost our mood and to keep ourselves motivated."

Another reason you may feel happier in the sunshine is because your body may feel less pressure and stress. Studies have shown that sunlight can increase the levels of nitric oxide in your body which works to dilate your blood vessels, making the blood flow easier in your body. This causes increased cardiovascular health.

Sunshine is even linked to your circadian rhythm — which is your body’s 24-hour internal clock that regulates your sleep and awake time. It does this by responding to changes in light during the day. 

Light is considered a zeitgeber — which in German means “time-giver” — since it is a stimulus for the body to set its biological clock. 

So, bright and early in the morning when you are outside getting sunlight your circadian rhythm becomes aware of what time it is. In the afternoon when there is more sunlight, your circadian rhythm becomes stronger and even more aware of what time it is. 

When exposed to the sun, your body blocks melatonin production which can explain why you feel more energetic in the sunshine. As the sun sets, your body becomes aware that it is time to sleep. Therefore, in the darkness you will produce more melatonin which is connected to greater longer, more quality sleep at night. 

While sun exposure is important, overexposure to the sun can lead to many serious health issues including skin cancer, sunburn, premature aging and damage to the eyes. Wearing sunscreen is the best way to avoid running into these issues as you soak up the sun. 

“Don’t forget that light also has effects on us beyond what we can see, like heat on our skin and the ultraviolet exposure that gives us vitamin D and sunburns," Anderson added. “You can still get a sunburn on an overcast day due to ultraviolet exposure.” “You will still need sunscreen on the slope even if the skies are grey — your future self will thank you for wearing some.”

So, as the summer continues — soak up the sunshine and don’t forget that sunscreen! Your skin, body and brain will thank you.

“The effect of light on brain-body interactions influences many aspects of our physiology like blood pressure and metabolism, and our higher selves like our cognition, motivation and mood,” Anderson said. “We are just beginning to appreciate and understand how our brains, and our minds, interface with our internal bodily organs towards health and disease.” “Research shows the power of light to regulate these invisible internal forces is much more real than a rainbow.”


Zeinab Faraj

Zeinab Faraj is the assistant sports editor on the 143rd editorial board and a member of the class of 2028 in the College of Arts and Sciences. You can reach her at zfaraj@cornellsun.com.


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