We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What are Circadian Rhythms?

Mary McMahon
By
Updated Jan 31, 2024
Our promise to you
WiseGeek is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WiseGeek, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Circadian rhythms are cyclic and persistent patterns of behavior, physical changes, and mental characteristics exhibited by most life on Earth, from the smallest bacteria to the largest redwood tree. These rhythms roughly follow 24 hour periods, reflecting the amount of time it takes for the Earth to complete a rotation. The study of circadian rhythms and the internal clocks that most creatures seem to have is known as chronobiology. Researchers study them to learn more about life on Earth, and how to treat various conditions such as sleep disorders.

Several characteristics distinguish these rhythms. The first is that the changes will be retained through dramatic changes in environmental conditions. For example, an animal in the dark will still have periods of increased and decreased activity that correspond with a 24-hour cycle. Repeated input from external stimuli can also reset the internal clock, as anyone who has switched time zones is probably aware. In addition, fluctuations in temperature do not appear to impact circadian rhythms.

The term was coined by Franz Halberg, a researcher at the University of Minnesota. Halberg was fascinated by the cyclical patterns of behavior that could be observed in things like plants, which actually slowly move over the course of a day to take advantage of changing light conditions. The word is derived from the Latin words circa, meaning “around,” and dies, for “day.” The study of these patterns links a number of disciplines, including chemistry, general biology, genetics, physiology, and even psychology. Halberg is widely regarded as the father of chronobiology, although circadian rhythms have been observed and described since the 1700s.

Humans tend to be most interested in these patterns in terms of how they affect sleep. When people experience sleep disorders such as insomnia, these problems can sometimes be linked to a disruption of their internal clocks that could potentially be fixed. It also explain why people experience periods of more alertness at certain times of the day, and when humans feel sleepy or hungry as well.

A clear genetic link to circadian rhythms has been established by researchers, who suggest that these very basic patterns have probably been on Earth almost as long as living organisms have. Primitive bacteria demonstrate circadian patterns, for example. Animals with brains also clearly have an internal biological clock.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a WiseGeek researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By fify — On May 23, 2011

Great article! I heard that the circadian cycle is roughly 24 hours (a little bit more than 24 hours) because the days used to be longer in our early history.

Does that mean that if we did not have a way of checking the time, we would function according to an internal clock that runs closer to 25 hours?

By bear78 — On May 22, 2011

Whenever I fly across the ocean, I experience jet-lag. It is actually worse when I fly towards the east. I am unable to adjust to the new time zone for at least a week. I wake up extremely early in the morning and take naps during the day. It's not as bad when I fly west, although I'm not sure why.

I knew jet lag happened because of time zone difference. But I never realized that it's caused by a disruption of our circadian rhythms and can be serious. I can't imagine what pilots and air hostesses go through.

By burcidi — On May 19, 2011

I read a book on nutrition and weight loss which talked about the cycle and patterns of eating and energy use in our bodies.

For example, the author said that our metabolism kicks up at sunrise and slows down at sunset, no matter what we are doing. So even if we sleep until noon and go to bed at two in the morning, our metabolism still functions the way it has been as long as we existed.

I think this is a good example and also proof of circadian rhythms.

By mitchell14 — On May 18, 2011

A lot of spiritual beliefs, such as shamanism, take circadian rhythms into account to some degree. I have known people who believed almost all illnesses could be pinned down to a problem in a person's daily cycles. While I would not go that far, I do think it makes a difference.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

Learn more
WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.