The UV index measures the sun's ultraviolet radiation risk on a scale of 1 to 11+

Demystifying sunscreen

Sunscreen is helpful all year round. Experts argue a minimum level of protection is SPF 30. There are two kinds of sunscreen: mineral (a physical barrier) and chemical (absorbs UV light). No new sunscreen ingredients have been approved in the US in decades, so foreign products are common.

The weakest form of light that is dangerous to humans is ultraviolet

Unlike radio waves, microwave, infrared, and visible light, UV light can produce chemical changes, such as curing adhesives and resins, causing substances to fluoresce, and destroying the genetic material of microorganisms. This makes UV light useful for sterilization, forensics, and quickly drying nail polish.

Oxygen and ozone molecules absorb up to 99.9% of UV radiation reaching Earth

Although they make up no more than 10 out of every million molecules in the ozone layer, ozone provides outsized protection by absorbing the most energetic wavelengths of ultraviolet radiation. This absorption increases thermal energy in the stratosphere, causing temperatures there to rise with altitude.

Vitamin D supplement pills are linked to rising cases of vitamin D toxicity in the US

Vitamin D deficiency is common. But taking Vitamin D supplements in doses exceeding 4,000 IU/day (a measurement of vitamin biological activity) for prolonged periods can raise bodily concentrations of this vitamin to dangerous values. US National Poison Data indicates that the annual average of vitamin D poisonings from 2000-05 was 196, but this rose by 1,600% to 4,535 per year for the period of 2005-11.

EXTREMA is a smart city system protecting residents from heat-related health risks

The mobile application is designed to protect citizens in select European cities from extreme temperatures by calculating the heat index at a specific location and providing personalized information to users. Municipal governments can also utilize it to inform emergency responses, such as determining when and where to open cooling centers.

A composite of telescope images of the sun, which each reveal unique solar features

While traditional cameras can reveal sunspots—cooler regions on the sun's surface—in visible light, x-ray detectors can highlight explosions of high-energy plasma and magnetic fields known as coronal mass ejections. Hydrogen-alpha filters can reveal clouds and filaments of material suspended in magnetic fields above the sun's surface.

Calculate your risk of developing cancer

Hosted by the National Cancer Institute, this tool provides interactive charts that display the likelihood of dying from various causes—including cancer—based on factors like age, sex, race, and smoking status. By contextualizing cancer risk among other potential health threats, users can create custom charts.

Scientists quantify how far from the poles auroras will be visible using the G-scale

The Geomagnetic Storm scale indicates the expected severity of the deformation of Earth's magnetic field based on the amount of energy injected by the solar wind. Solar activity is monitored using various satellites to forecast these storms, which can also be used to anticipate damage and disruption to power systems, radio communications, and satellite navigation.

An overview of the sun, from its formation to its role in fueling and protecting life on Earth

With a surface gravity almost 28 times Earth's, the sun's mass exerts enough pressure to raise temperatures in its core above 15 million degrees Celsius (27 million degrees Fahrenheit) and enable nuclear fusion. These reactions produce the energy that sustains Earth's photosynthesis-dependent food chains, while the sun's magnetic field protects the solar system from cosmic ionizing radiation.

10 percent of SAD cases occur in the summer

Despite its significantly lower incidence, summer-risk SAD is as significant as its winter counterpart. Rather than being prompted by less light, the summer version is typically spurred by high temperatures, strong light, distinct summer time social pressures (appearing in a bathing suit, for example), and pollen. Common treatments include keeping cool and prioritizing sleep.

Learn about ionizing radiation and see the most radioactive places on Earth

The average person is exposed to radiation every day, though most of it is either harmless non-ionizing radiation or ionizing radiation at doses too small to significantly affect an individual. The highest doses of ionizing radiation are received by smokers due to the radioactive polonium and radioactive lead in tobacco products.

Visualize your city’s annual daylight map

Type in your town or region and see sunrise and sunset for each day of the year. A separate view shows the number of hours of day versus night for each day. Search a city far north like Oslo, Norway, and compare its graphs to one near the equator (like Singapore).

What is the lipstick index?

The lipstick index is an economic theory that breaks down to this: when consumers think an economic downturn is looming, sales for affordable luxury items (such as lipstick) go up. While it's not an economically proven theory, it's still worth considering. So why do consumers exhibit this behavior? Read more about the lipstick index to find out.

See the UCLA Loneliness Scale, often used to measure global loneliness

This 20-question survey, first established in the late 1970s and subsequently revised and often adapted, aims to measure the subjective experience of loneliness. Respondents rate various items on a scale of 1 (Never) to 4 (Often). One revision of the test (not included here) offers an abbreviated three-question version that focuses on how often you feel companionship, left out, and isolated.

Extreme heat puts people at risk of developing kidney stones

It's essential to remain hydrated in summer weather to keep your body healthy, but one reason is to help dilute minerals that naturally build up if they aren't excreted in our water-fueled urine. Doctors recommend people generally drink 64 ounces of water a day and also eat foods with salt to help ward off dehydration.

MS risk is shaped by geography, not just genes

Latitude—and related vitamin D exposure—seems to affect MS risk. People who migrate from a high-risk MS latitude (like northern Europe or the northern US) to a lower-risk latitude (like tropical areas) before age 15 tend to adopt the lower risk of their new country—suggesting there's a critical window for environmental exposure.

See if you know how to recognize poison ivy

This quiz, accompanied by photos of the varied forms of the plant, may help you identify the plant when it counts.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

The National Weather Service communicates tornado risks on a three-tier system

During a tornado watch, atmospheric conditions favor the development of a tornado, and residents in an area should be prepared to seek refuge. A tornado warning is issued if a tornado has been detected, while a tornado emergency indicates a violent tornado has touched down in the area, with severe threats to human life and property expected.

View US solar energy industry trends and trajectories, tracked by SEIA

The Solar Energy Industries Association provides charts summarizing the state of solar energy in the US, including cumulative solar installations, solar jobs, photovoltaic pricing and deployment, and inflation and supply chain constraints within the market.

Dsup protects DNA from radiation up to 3,000 times the tolerable human dose

A key component of a tardigrade’s biochemical toolkit, the damage suppressor protein is produced and binds to DNA molecules when the animal enters its dormant tun state. Dsup has provided a 50% reduction in double-strand DNA breaks in mice after exposure to X-rays.

View the 55 ECVs used to describe Earth's atmospheric conditions

Essential climate variables include physical, chemical, and biological variables that meaningfully contribute to Earth's climate and how it changes with time. Many of these variables influence one another through feedback mechanisms across Earth's atmosphere, hydrosphere, cryosphere, biosphere, and geosphere.

Feels-like temperature indicates how our skin will feel

When the wind is moving faster, we tend to feel colder due to the so-called "wind chill," which cools our bodies by moving heat away from them and making water evaporate faster. On the other hand, high levels of humidity can make us feel 10 degrees warmer at times.

See this graphic describing what different decibel levels mean for hearing loss

From the sound of a ticking watch, which is roughly 20 decibels, to the sound of a gunshot at 140 decibels, the Hearing Health Foundation breaks down the decibels of daily sounds in this chart, noting that sounds louder than 70 decibels are considered harmful.

Ranking every baseball stadium outfield by how hard it is to play

Park factors have long adjusted for how a ballpark helps or hurts hitters and pitchers, but rarely fielders. MLB's Statcast looked at five years of Outs Above Average data to shed light on the gap. It found that stadiums with roofs or in cities that regularly have sunny skies dominate the easy end, while those battered by wind or rain, like San Francisco's, are the hardest to play.

The world's 10 best places to live

The Economist Intelligence Unit's Global Liveability Index ranked 173 cities based on stability, healthcare, culture and environment, education, and infrastructure. The report shows an overall increase in livability scores compared to previous...

Between 10 million and 50 million people in the US develop rashes from poison ivy, poison sumac, and poison oak each year.

Explore an interactive map built from more than 100,000 survey responses on where people find joy in their lives

Use this calculator to find the dollar value of your mental load, from meal planning to coordinating after-school care for your children.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

Doctors differentiate between a phobia and fear by asking patients whether their fear interferes with their day-to-day activities.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

44% of Americans say they pray at least once a day—discover how your state's religiosity stacks up against the rest of the country.

Fireworks-related ER visits are on the rise—in 2024, they increased by 52% as compared to the prior year.

View the ten deadliest tornadoes in US history.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

The first steps to rebuilding your credit score include getting to know exactly what's on your credit report and figuring out how far you are from the '700 club,' or 'good score' range.

Learn how to read a prospectus, the juicy document that any company must file with the SEC before going public.

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

Browse a detailed visual analysis of over 200,000 similes—comparisons that often use 'like' or 'as'—from popular fiction to see how frequently writers the same idiomatic expressions.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Coral reefs get their colors from zooxanthellae—microorganisms that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

Ebola species have historically been named after where they were discovered, stigmatizing residents who live there, including Bundibugyo, in Uganda.

Prince's sexually explicit 1984 track 'Darling Nikki' attracted the ire of the Parents Music Resource Center, an advocacy group that inspired the Parental Advisory sticker, even though the song ends with a Christian message.

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in casualties, forces mobilized, and displacement of civilians.