Glowy oils, tinted creams, misty sprays, chalky sticks, lightweight gels. Like many people, my pool bag is filled with many types of sunscreen. But all use the same sun-shielding chemicals. In fact, the allowed ingredient list for U.S. sunscreens hasn’t changed in 20 years — until now.

This June, the U.S. Food and Drug Administration (FDA) added bemotrizinol (Beh-moh-TRIZ-eh-nol) to its approved list.  

“I think we should all be super excited,” says Tanya Hathaway. She’s a dermatologist who specializes in treating high-risk skin-cancer patients. Hathaway works at the Fred Hutchinson Cancer Center in Seattle, Wash.

Bemotrizinol has many benefits. It lasts longer than other sunscreen ingredients. It won’t get quickly absorbed into the bloodstream. And it’s very good at blocking those rays of the sun that age skin.

Sunscreens in Europe have used the chemical for more than 25 years, Hathaway notes. More recently, it’s been approved in Japan, Canada, Australia and many other places.

There are some sunscreen ingredients used elsewhere that still are not allowed in U.S. products. Bemotrizinol’s approval could open U.S. doors for some of these. It’s “a great first step,” Hathaway says.

A new chemical sunscreen

Sunscreens use a few tricks to protect our skin from the sun’s rays. Physical sunscreens rely on minerals such as titanium dioxide and zinc oxide. These create a coating that reflects sunlight, like a mirror. But they can leave a white sheen on the skin. Just think of a lifeguard’s nose, says Jennifer Stein. She’s a dermatologist at NYU Langone Health in New York City.

Those zinc and titanium products also “don’t rub in so well,” she notes. “And if people don’t like the way their sunscreen smells or feels, they’re not going to use it.”

Non-mineral sunscreens often rub in a bit better. They often use chemicals such as avobenzone (Ay-vah-BEN-zoan) and oxybenzone to absorb the sun’s rays. But these molecules are not very stable. They start to break down when hit by sunlight, Stein says. That’s not ideal for something that’s designed for use in the sun.

Because bemotrizinol is more stable, people may not need to apply sunscreens with it as often. This new ingredient also is good at blocking ultraviolet A1 (UVA1) radiation. That’s a type that gets deep into the skin. Over time, UVA1 can make skin wrinkly, loose and spotted, Hathaway says.

Current U.S. sunscreens do a good job of blocking UVB, which causes sunburns. But U.S. sunscreens had fewer options for blocking UVA, she says. Bemotrizinol “really expands that UVA spectrum of coverage.”

Is it safe?

View this post on Instagram

You might have seen influencers on TikTok or Instagram making DIY sunscreens. Often, they will call the ingredients in commercial brands “toxic.” Sunscreen skepticism on social media is nothing new, Stein says. Patients who avoid sunscreen often worry about chemicals passing through the skin.

That can happen with things like avobenzone and oxybenzone. They may even get into your blood, Stein says — but only if “you apply them to large areas of the body repeatedly throughout the day.” Even so, people shouldn’t fear them. Hathaway says no studies have shown that U.S. sunscreen ingredients are unsafe when used at current levels.

Bemotrizinol, which is a big molecule, is less likely to pass through skin than these other chemicals. It’s “too big to squeeze through the skin cells to get down into your bloodstream,” Stein says.  

FDA classifies bemotrizinol as GRASE (short for generally recognized as safe and effective). Titanium dioxide and zinc oxide are the only other U.S. sunscreen ingredients with this rating.

Bemotrizinol’s U.S. approval goes into effect on August 9. So sunscreens using it could hit shelves later this summer. But a new sunscreen is not the only way to stay safe from the sun. There are plenty of low-tech options, too: long sleeves, hats, sunglasses and staying in the shade. “The more clothing you’re wearing,” Stein emphasizes, “the less you have to depend on sunscreen.”

The word forensic comes from the Latin word forensis, which means of or before the forum. “During the time of the Romans, a criminal charge meant presenting the case before a group of public individuals in the forum. Both the person accused of the crime and the accuser would give speeches based on their side of the story. The individual with the best argument and delivery would determine the outcome of the case. Basically, the person with the sharpest forensic skills would win. This origin is the source of the two modern usages of the word ‘forensic’ — as a form of legal evidence and as a category of public presentation.” (Wikipedia, 2008)

Today, the use of scientific evidence is so prevalent in the courtroom that the term forensics has become associated with forensic science. Forensic science is any science that is used in the courts or judicial system and it is extremely vital. The goal of a forensic scientist is to remain impartial and to appraise all of the available evidence in order to determine the truth.

Forensic science includes many areas of study, such as criminalistics, engineering science, pathology and biology. If a sports player were to die suddenly while playing a game, a forensic scientist with a specialty in pathology and biology would be called in to find out the cause. The scientist might have to perform an autopsy and examine the body to determine if the death had a natural cause — such as a health problem — or not. (To find out more about a related career, you can check out the Science Buddies career profile on pathologists.)

On the other hand, a forensic engineer may need to apply engineering principles to the purposes of law investigations. For example, a forensic scientist with specialty training as a civil engineer may study failure analysis and evaluate the quality of construction and manufacturing of structures involved in a crime or catastrophic event. They may look into why a particular car rolled over or why a building or bridge collapsed.

In general, to become a forensic scientist, you may need to study math, science and engineering. To find out more about being a forensic scientist, you can check out the Science Buddies career profile on forensic science technicians.

In this forensics science project, you will investigate how the size of blood spatter changes depending on the height that the blood was dropped from, but you will be using fake blood instead of real blood. In crime scenes where people are wounded, investigators apply principles of blood spatter analysis by taking measurements, such as of the diameter of the blood spatter, to figure out what happened. How do you think the diameter of the spatter changes as blood is dropped from different heights? Find out by trying your hand at collecting evidence in this science project and remember that solving mysteries is serious work!

Terms and concepts

• Forensic science
• Evidence
• Blood spatter analysis

Questions

• What is forensics?
• What are the different areas of study in forensic science?
• What kinds of projects do forensic scientists work on?
• How do you think the height from which something falls, such as a drop of blood, affects how it lands on the surface below?

Objective

To investigate how, in the field of forensic science, the size of blood spatter correlates to the distance from which the blood fell.

Resources

The following sources will help you learn more about forensic science:

• Wikipedia Contributors. (2014, March 24). Forensic science. Wikipedia: The Free Encyclopedia. Retrieved March 25, 2014.
• Wikipedia Contributors. (2014, March 22). Bloodstain pattern analysis. Wikipedia: The Free Encyclopedia. Retrieved March 25, 2014.
• Layton, J. (2008). How Crime Scene Investigation Works. Howstuffworks. Retrieved May 5, 2008.

Materials and equipment

• Digital scale (or you can use measuring spoons)
• Graduated cylinder, 50 mL or 100 mL size (or you can use measuring spoons)
• Cornstarch (17 g or about 2 tbsp)
• Corn syrup (60 mL or about 4 tbsp)
• Red food coloring (5 mL or 1 tsp)
• Bowl
• Water
• Fork or spoon for mixing
• Optional: Plastic wrap
• Cardboard. You will want enough cardboard to create seven pieces that are each about 30 cm by 30 cm (12 in by 12 in). The pieces should be able to lay flat and should not have many folds or creases in them.
• Scissors
• Pencil or pen
• Medicine dropper
• Measuring tape
• A chair or stepping stool
• Metric ruler or measuring tape that has millimeter marks
• A location to do your experiment where the ground can be easily cleaned (in case of spilling the simulated blood). For example, concrete or linoleum may work well.
• Optional: Butcher paper or newspaper
• Helper
• Lab notebook

Experimental procedure

Making the simulated blood

1. Using the digital scale, weigh 17 grams (g) of cornstarch and place it into the bowl. (Or measure two tablespoons [tbsp] of cornstarch and add it to the bowl.)
2. Thoroughly mix 30 milliliters (mL; 2 tbsp) of water into the cornstarch with a fork or spoon. The mixture must be smooth, as shown in Figure 1 below.

3. Add 60 mL (4 tbsp) of corn syrup to the bowl and mix thoroughly. The mixture should be smooth, as shown in Figure 2 below.

4. Mix in 5 mL (1 tsp) of red food coloring. Stir until the mixture is a consistent color, as shown in Figure 3 below.

5. You should now have a small bowl of simulated blood. If you will not be using it right away, cover the bowl with plastic wrap and set it aside.
6. Note: Be careful not to spill the simulated blood on furniture or carpeting, as it can stain! If it does spill, be sure to clean up the simulated blood immediately.

Blood spattering

1. Carefully cut up the cardboard into seven pieces of similar sizes. Each piece will be used for testing a different height.
   1. Each piece should be about 30 centimeters (cm) by 30 cm (12 inches [in] by 12 in). This will give you a good amount of space for dropping 10 drops of simulated blood onto each piece.
   2. Make sure the pieces can lay flat.
   3. Avoid using pieces with many folds or creases in them.
2. Use a pencil or pen to label each piece of cardboard with the height you will be testing on it.
   1. The heights you will be testing are 30 cm (12 in), 60 cm (24 in), 90 cm (36 in), 120 cm (48 in), 150 cm (60 in), 180 cm (72 in) and 210 cm (84 in).
3. Lay the cardboard piece you labeled for testing a height of 30 cm (12 in) flat on the ground where you will do your experiment.
   1. Because the simulated blood can stain, you should only do this experiment on a surface that can be easily cleaned, such as linoleum or concrete.
   2. You may also want to cover the surface (under the cardboard) with butcher paper or lots of newspaper to prevent stains.
4. Fill the medicine dropper with some simulated blood and hold the dropper completely vertically above the cardboard piece, as shown in Figure 4 below. Have a helper use the measuring tape to make sure the tip of the dropper is 30 cm (12 in) above the cardboard.

5. Drop a single drop of simulated blood onto the cardboard piece.
6. Repeat steps 4–5 nine more times so that you have dropped a total of 10 drops onto the cardboard piece. Then let the cardboard piece dry, being careful not to disturb the drops while they dry.
   1. If any of the drops landed on another drop or landed in a crease or fold on the cardboard, do not count these drops for your total of 10.
7. Repeat steps 3–6 with all of your other cardboard pieces, being sure to test each from the correct height.
   1. You and your helper will need to stand on chairs or stepstools to reach the highest heights. Be careful when doing this.
8. When all of the drops on the cardboard pieces have dried, measure the diameter of each drop — or spatter — in millimeters (mm) or inches (in) and record the measurements in your notebook in a data table like Table 1 below. Be sure to measure very carefully, because there may be very small, but measurable, differences between the drops. Tip: The drops may look glossy and wet even after they have dried. You may want to make an extra drop on one of the cardboard pieces that you can test (by touching it) to see when the drops have completely dried.

Drop height (cm) or (in)	Drop	Drop diameter (mm) or (in)	Average drop diameter (mm) or (in)
30	1
	2
	3
	…
	10
60	1
	2
	3
	…
	10
90	1
	2
	3
	…
	10
etc.	etc.

9. Calculate the average diameter of the drops for each height. Add your answers to your data table.
   1. For example, if the 10 drops you measured at a height of 90 cm (36 in) had diameters of 12.5 mm (0.49 in), 12.0 mm (0.47 in), 12.5 mm (0.49 in), 13 mm (0.51 in), 12.5 mm (0.49 in), 13 mm (0.51 in), 12.5 mm (0.49 in), 12.0 mm (0.47 in), 13.5 mm (0.53 in), and 12.0 mm (0.47 in), the average drop diameter from a height of 90 cm (36 in) would be 12.6 mm (since the sum of all 10 drops is 125.5, and this number divided by 10 rounds to 12.6 mm (0.50 in).
10. Make a graph of your results. On the x-axis, put the drop height (cm or in), and on the y-axis, put the average drop diameter (mm or in).
11. Look at your graph and try to draw some conclusions based on your results.
    1. How did the diameter of the spatter change as the simulated blood was dropped from different heights?
    2. How do you think your results could help a forensic scientist figure out what happened at a crime scene?

This activity is brought to you in partnership with Science Buddies. Find the original activity on the Science Buddies website.

In the sea, soft-bodied sea slugs crawl around without shells to protect them. Instead, they sport dazzling colors and flashy patterns to warn would-be predators that they’re toxic. Now, researchers have learned that many of these vibrant hues come from structures under the slugs’ skin.

These slugs, called nudibranchs (NU-dih-branks), are sometimes dubbed the “butterflies of the sea.” Their colors are “exceptionally bright,” says materials scientist and physicist Samuel Humphrey. He works at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany. Nudibranchs’ range of colors and patterns exceeds those of other ocean dwellers and is only like that of butterflies and birds, he says.

Not much was known about nudibranch colors, Humphrey says. But in nature, some of these colors — such as white, blue and purple — are hard to get from pigments. (Those are molecules that provide color.) That made Humphrey’s team suspect the slugs’ colors instead arise from light waves bouncing off structures on their bodies. Such structural color can create hues as intense as those seen on the sea slugs.

Humphrey collected one species of nudibranchs off the coast of France. Others, he and his colleagues bought from aquarium shops. The researchers looked at the creatures under the microscope and saw tiny dots of colors that combined to create a shade. For instance, a nudibranch might look purple, but zoom in, and you may find specks of red and blue. “It’s a bit like mixing paints until you get the color you want,” Humphrey says.

Actually, he adds, “it’s better than that.” Sea slugs’ hues arise from specific wavelengths, or colors, of light bouncing off them and reaching our eyes. And the team found that, for a given color, nudibranchs reflect up to 80 percent of light that hits them. That makes their hues more vivid than those produced by pigments, which create colors by absorbing light. Losing light means losing brightness, Humphrey explains.

The researchers shared their results in the March issue of the Proceedings of the National Academy of Sciences.​

With a powerful microscope, the team saw stacks of tiny plates under nudibranchs’ skin. The plates were crystals made of guanine. The thickness of the plates and the distance between them in a stack determined the colors that they reflected. That allows sea slugs to wear a rainbow of colors made of just one material.

The many tiny dots of color on sea slugs’ skin creates an effect akin to how TVs make images with many spots of only a few colors. This is called pixelation. “It feels like a thing that humans have invented,” Humphrey says. “But actually, evolution had invented it millions of years ago.”

Data Dive:

1. How many types of colored light make up the violet hue of Hypselodoris tryoni (Figure A)?
2. How many types of colored light make up the beige or white region of the same slug (Figure B)? Which color of light has the highest reflectance? What is that color’s peak wavelength?
3. Which sea slug here has the color with the highest reflectance? (Hint: Not all the y-axes are exactly the same.) What is that color and what is the peak wavelength?
4. How many different colors of light are in the region of Chromodoris annae (Figures E and M)? Based on those colors, how do you think this area of the slug looks to the eye?

Fjord (noun, “FYORD”)

Fjords are long, narrow arms of the sea that often reach far inland. They are typically flanked by tall, steep cliffs on either side. Below water, their trenches often plunge much deeper than the open sea to which they connect.

Fjords are usually formed by glaciers. This sets them apart from other types of narrow valleys, or gorges. As glaciers slowly make their way to the ocean, they can carve deep channels through the terrain. These channels remain even after the glaciers have melted and filled with water, creating fjords.

These dramatic landscapes offer sweeping vistas of craggy cliffs and majestic mountains that inspire awe. Some scenes in The Lord of the Rings movies were filmed in the fjords of New Zealand. For instance, aerial shots showing the fictional River Anduin get their steep, forested terrains from Fiordland National Park.  

However, Norway holds the record for most fjords. It has more than 1,200. The largest is Sognefjord. This fjord stretches 205 kilometers (127 miles) inland. Steep mountains and cliffs rise up to two kilometers (1.2 miles) above the water below. This water hides a deep underwater trench that plunges up to 1.3 kilometers (0.8 mile) below sea level.

In a sentence

In 2023, a landslide triggered a tsunami that wiped out vegetation along Greenland’s Dickson Fjord.

Check out the full list of Scientists Say.

A common houseplant hides a splendid geometric pattern.

This design, called a Voronoi diagram, appears on the leaves of the Chinese money plant. The layout may arise as waves of a plant hormone spread across a leaf during its development. A similar process may shape the vein patterns in leaves of other plants, too.

Researchers shared these findings May 12 in Nature Communications.

This is a “beautiful” showcase of how plant veins develop to move water across leaves most efficiently, says Lawren Sack. He did not take part in the research. But he does study plant biology at the University of California, Los Angeles. Veins of leaves “have so much to tell us” about how to get resources where they need to go, he says.

Lurking in leaves

Leaves of the Chinese money plant (Pilea peperomioides) are speckled with pores. Called hydathodes, these pores release water. Each one is fenced in by veins to form a mosaic.

While in high school, Elijah Blum discovered a curious pattern in those leaf veins. He noticed it while plant-sitting for his sister. At the time, Blum was an intern at Cold Spring Harbor Laboratory in New York. (He’s now in college at New York University.) He shared what he’d found with his internship supervisor, computer scientist Saket Navlakha.

“He showed the plant to me, and he said, ‘Look, the veins look kind of interesting here,’” Navlakha says. “We sort of held it up to the light — and we saw that … Voronoi diagram.”

In a Voronoi diagram, a surface is split up into zones. Each zone contains a designated point. And every spot within a zone must be closer to that zone’s point than any other.

Urban planners use the same idea to decide which fire department a house should be assigned to. This helps each house in a city or town be closer to the fire station in its zone than any other station.

Patterns that look similar to Voronoi diagrams appear elsewhere in nature. The tiles on giraffe fur look like this type of design. So do the scales of dragonfly wings. But in a true Voronoi diagram, the mosaic must form around a set of points. In the Chinese money plant, the water-oozing pores serve as those points.

Making the mosaic

Blum and the others were curious how this pattern might develop.

Similar leaf veins are thought to form through canalization. In this process, a hormone involved in plant development — auxin — branches out across leaves. As it does, it creates a treelike network of channels that become veins.

But that wouldn’t produce a Voronoi diagram around a leaf’s pores, the team found. Computer models instead showed that as Pilea leaves develop, waves of auxin spread out from each pore. Those waves collide to form ridges. Eventually, they become a leaf’s major veins.

More research is needed to find out why Pilea leaves follow this pattern, says team member CiCi Zheng. She studies the math of living things at the Allen Institute in Seattle, Wash.

The Voronoi diagram layout might be useful for plants, she says. This pattern keeps a leaf’s major veins — which transport water — as far as possible from its water-leaking pores. “You might want to place the veins not directly close to any of those locations where water evaporates super-fast,” Zheng says.

Sack at UCLA is excited about what new tech this finding might inspire. Past studies of leaf veins, he says, have helped engineers reimagine how to distribute resources such as water and energy. Such insights have improved solar panels, electronic circuits and irrigation systems.

“The more we know about leaf veins,” Sack says, “the more we can build functional and beautiful systems around us.”