News
Why can’t it always be summer? It’s all about the Earth’s tilt
Earth’s axial tilt causes the seasons. As Earth orbits the Sun, different hemispheres tilt toward or away, creating summer and winter depending on location.
Stephanie Spera, University of Richmond
Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.
Why can’t it always be summer? – Amanda, age 5, Chile
With its long days just itching to be spent by water doing nothing, summer really can be an enchanting season. As Jenny Han wrote in the young adult novel “The Summer I Turned Pretty”: “Everything good, everything magical happens between the months of June and August.”
But all good things must come to an end, and summer cannot last forever. There’s both a simple reason and a more complicated one. The simple reason is that it can’t always be summer because the Earth is tilted. The more complicated answer requires some geometry.
I’m a professor of geography and the environment who has studied seasonal changes on the landscape. Here’s what seasons have to do with our planet’s position as it moves through the solar system.
This animation shows why the Earth has seasons.
Closeness to the Sun doesn’t explain seasons
First, you need to know that the Earth is a sphere – technically, an oblate spheroid. That means Earth has a round shape a little wider than it is tall.
Every year, Earth travels in its orbit to make one revolution around the Sun. The Earth’s orbit is an ellipse, which is more like an oval than a circle. So there are times when Earth is closer to the Sun and times when it’s farther away.
A lot of people assume this distance is why we have seasons. But these people would be wrong. In the United States, the Earth is 3 million miles closer to the Sun during winter than in the summer.
Spinning like a top
Now picture an imaginary line across Earth, right in the middle, at 0° latitude. This line is called the equator. If you drew it on a globe, the equator would pass through countries including Brazil, Kenya, Indonesia and Ecuador.
Everything north of the equator, including the United States, is considered the Northern Hemisphere, and everything south of the equator is the Southern Hemisphere.
Now think of the Earth’s axis as another imaginary line that runs vertically through the middle of the Earth, going from the North Pole to the South Pole.
As it orbits, or revolves, around the Sun, the Earth also rotates. That means it spins on its axis, like a top. The Earth takes one full year to revolve around the Sun and takes 24 hours, or one day, to do one full rotation on its axis.
This axis is why we have day and night; during the day, we’re facing the Sun, and at night, we’re facing away.
But the Earth’s axis does not go directly up and down. Instead, its axis is always tilted at 23.5 degrees in the exact same direction, toward the North Star.
The Earth’s axis is tilted due to a giant object – perhaps an ancient planet – smashing into it billions of years ago. And it’s this tilt that causes seasons.
It’s all about the tilt
So that means in June, the Northern Hemisphere is tilted toward the Sun. That tilt means more sunlight, more solar energy, longer days – all the things that make summer, well, summer.
At the same time, the Southern Hemisphere is tilted away from the Sun. So countries such as Australia, Chile and Argentina are experiencing winter then.
To say it another way: As the Earth moves around the Sun throughout the year, the parts of the Earth getting the most sunlight are always changing.
Fast-forward to December, and Earth is on the exact opposite side of its orbit as where it was in June. It’s the Southern Hemisphere’s turn to be tilted toward the Sun, which means its summer happens in December, January and February.
If Earth were not tilted at all, there would be no seasons. If it were tilted more than it is, there would be even more extreme seasons and drastic swings in temperature. Summers would be hotter and winters would be colder.
Defining summer
Talk to a meteorologist, climate scientist or author Jenny Han, and they’ll tell you that for those of us in the Northern Hemisphere, summer is June, July and August, the warmest months of the year.
But there’s another way to define summer. Talk to astronomers, and they’ll tell you the first day of summer is the summer solstice – the day of the year with the longest amount of daylight and shortest amount of darkness.
The summer solstice occurs every year sometime between June 20 and June 22. And every day after, until the winter solstice in December, the Northern Hemisphere receives a little less daylight.
Summer officially ends on the autumnal equinox, the fall day when everywhere on Earth has an equal amount of daylight and night. The autumnal equinox happens every year on either September 22 or 23.
But whether you view summer like Jenny Han or like an astronomer, one thing is certain: Either way, summer must come to an end. But the season and the magic it brings with it will be back before you know it.
Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.
And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.
Stephanie Spera, Assistant Professor of Geography and the Environment, University of Richmond
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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News
Untreated sewage and fertilizer runoff threaten the Florida manatee’s main food source, contributing to malnutrition
Aarin-Conrad Allen, Florida International University
The gentle, slow-moving Florida manatee has no natural predators.
And yet, these charismatic mammals face numerous threats.
Manatees are struck by vessels in busy waterways across the state, and a majority bear scars from these collisions.
Harmful algal blooms – characterized by the rapid growth of algae that degrades water quality – can impair their nervous systems.
With less blubber, or fat, compared with other marine mammals like whales, dolphins, seals and sea lions, manatees are vulnerable to cold-stress syndrome during winter months.
And they can ingest or get entangled in marine debris like derelict fishing gear and drown or be crushed by floodgate and water control structures.
I am a doctoral candidate in marine biology at Florida International University’s Institute of Environment. Over the past 15 years, I have gained extensive experience working with marine mammals, particularly manatees.
Recently, my colleagues at the United States Geological Survey, Florida Department of Environmental Protection and I documented a change in the dietary pattern of manatees. We found that manatees are eating less seagrass – traditionally their primary food source – and more algae than in decades past. This change occurred along Florida’s Atlantic coast during a period of extensive seagrass decline.
We believe this represents an emerging threat to the species’ survival.
Protected species
Manatees were listed as an endangered species under the Endangered Species Act of 1973. By the early 1990s, the manatee population in Florida had dwindled to less than 1,300.
Researchers believe that federal protection, along with additional state measures such as slow-speed zones and no-entry refuges, has contributed to the growth of the manatee population in Florida.
In 2017, manatees were reclassified from endangered to threatened. Surveyors counted 5,733 individual manatees during a statewide aerial survey conducted in 2019.
Florida manatees average 9-12 feet (2.7-3.7 meters) in length and typically weigh about 1,000 pounds (450 kilograms), but they can grow as large as 3,500 pounds (1,600 kilograms). As the largest fully aquatic herbivore, they consume 5% to 10% of their body weight in vegetation each day.
While manatees eat a broad diet of over 60 different plants, they most commonly feed on species of seagrass. Seagrasses are marine plants that, like land plants, have leaves, flowers, roots and seeds, and make their food through photosynthesis.
So what happens when these seagrasses are no longer available?
A changing estuary
The Indian River Lagoon is an estuary along Florida’s east coast that covers roughly 350 square miles (560 square kilometers) between the mainland and barrier islands, from Ponce Inlet to Jupiter Inlet.
It is a critical habitat for manatees, which feed on native seagrass meadows in the lagoon during their seasonal migrations.
Seagrasses are vital to the health of marine ecosystems. They are a habitat for juvenile fish and other marine organisms, provide food for aquatic herbivores, reduce carbon in the atmosphere and improve water quality. They also protect coastal habitats by stabilizing sediments and reducing wave energy that can erode shorelines and damage coastal infrastructure, especially during hurricanes.
For more than a decade, the Indian River Lagoon has experienced extensive loss of seagrass meadows, due to a series of algae blooms associated with nutrient runoff and degraded water quality from septic overflow leaching into the environment.
When untreated sewage and fertilizers flow into the estuary, they add nitrogen, phosphorus and other nutrients that drive excessive algal growth. These harmful algal blooms deplete oxygen levels and block sunlight, which seagrass needs for photosynthesis.
Between 2011 and 2019, over 50% of all seagrass in the lagoon was lost. This led to an increase in macroalgae and even led to a change in the animal communities that live in the lagoon. For example, among finfish, sheepshead populations declined, while seabream numbers increased. Invertebrate communities were also affected, with bryozoans colonizing areas previously dominated by barnacles.
Manatees along the Atlantic coast have suffered two unusual mortality events since the seagrass decline, including one that is ongoing. Researchers attribute the increase in manatee deaths to malnutrition due to a shortage of seagrasses in the Indian River Lagoon.
A shift in manatees’ diet
In our study, we examined 193 manatee stomach samples collected from carcasses recovered from the Indian River Lagoon during two time periods – one before and one after the onset of the seagrass loss in 2011.
We compared stomach sample contents from carcasses collected between 1977 and 1989 with samples collected between 2013 and 2015.
Our findings indicate that manatees consumed 45% less seagrass and 74% more algae after the seagrass decline.
Recently, in a study supported by FIU’s Center for Aquatic Chemistry and Environment, I investigated differences in the nutritional composition – like protein, fat, carbohydrate and fiber – of items identified in manatee stomach samples. My preliminary results show notable differences in the nutritional composition of seagrass and algae.
Marine mammals are particularly vulnerable to dietary shifts due to their large size and high energy demands. Such changes can worsen their physical health and increase the likelihood of starvation.
Depleted oxygen levels are having a similar impact on aquatic vegetation and seagrass meadows in other regions of Florida, like Biscayne Bay and the Caloosahatchee River and Estuary. This suggests that the ecological challenges seen in the Indian River Lagoon could become more widespread.
What is the solution?
Remediation efforts within the lagoon have incorporated the restoration of seagrass through aquaculture and replanting strategies, similar to efforts to restore coral reefs.
While the lagoon’s seagrass has recently shown signs of regrowth, the rehabilitation of the ecosystem must begin with improving and maintaining water quality.
Counties along the lagoon have enacted fertilizer bans that aim to reduce the levels of nitrogen and phosphorus in the water that drive algal blooms.
New research, however, indicates that these restrictions alone will not fix the problem, as residential septic systems are the primary source of nutrient pollution in the lagoon.
Furthermore, many of the factors contributing to harmful algal blooms are intensified by global warming and changing climate, which could accelerate the decline of seagrass in Florida and elsewhere.
Given the multiple, synergistic threats facing manatees, I believe that improving water quality, protecting their food sources, and further research – coupled with community outreach and education – are critical to ensure the long-term survival of this iconic Florida species.
Aarin-Conrad Allen, Ph.D. Candidate in Marine Sciences, Florida International University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
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College Life
Campus diversity is becoming difficult to measure as students keep their race and ethnicity hidden on college applications
When the Supreme Court struck down race-based admissions at American colleges and universities just over a year ago, many predicted U.S. campuses would become much less diverse. But in part due to students who decide not to disclose their race or ethnicity, coupled with universities’ selective use of statistics, it is not clear how much the decision has affected diversity on campus.
As higher education institutions begin reporting the racial makeup of the class of 2028 – the first to be affected by the 2023 decision – the data is hard to interpret, confusing and inconclusive.
As a sociologist who has studied how institutions of higher education collect and report data on race and ethnicity, I have identified some factors that contribute to this lack of clarity.
Students don’t identify with choices given
Some students may not select a racial or ethnic category because they don’t believe any of the categories really fit. For example, before multiracial students could select “one or more,” an option that became widely available in 2010, they were more likely to decline to identify their race or ethnicity. Some even boycotted checkboxes entirely.
Other students don’t view their race as important: 67% of the students who choose “race and ethnicity unknown” are white. Of these students, 33% say race and ethnicity are not a relevant part of their identity, a researcher found in 2008.
The number of students who don’t respond to questions about race or ethnicity – and are listed in the “race unknown” category – is increasing. At Harvard University, for example, the percentage of “race-unknown” undergrad students doubled from 2023 to 2024.
As the number of “race unknown” students grows, it not only becomes harder to determine a student body’s ethnic and racial diversity but also the impact of the ban on race-conscious admissions.
Fearing discrimination, students don’t disclose race
Some students believe their race or ethnicity will harm their chances of admission.
This is particularly true at many selective institutions, which have higher nonresponse rates than less selective institutions, about 4% compared with 1% to 2%.
My research shows that students are even more likely to pass on identifying race or ethnicity at selective law schools, where race and ethnicity could be used among a variety of criteria for admissions before the Supreme Court ruled against that practice. An average of 8% of students at those schools chose not to identify, compared with 4% at less selective law schools.
‘We’re very diverse’: University decisions distort statistics
What a university chooses to report will also affect the student body demographic data the public sees. Harvard, for example, does not report its proportion of white students.
Some institutions use statistics strategically to appear more diverse than they are. These strategies include counting multiracial students multiple times – once for each race selected – or including international students as a separate category in demographic pie charts. The greater the number of different-colored slices on the chart, the more demographically “diverse” an institution appears to be.
Impact of Supreme Court ruling: Clearer picture coming soon
While universities may not all report their student demographics the same way in their own materials, they all have to report it the same way to the federal government – namely, to its Integrated Post Secondary Education Data System, better known as IPEDS. The next IPEDS report on characteristics for the 2024 enrollment class is expected to be released in spring 2025. Once that data is available, a better picture of how the Supreme Court’s decision has affected diversity in college enrollment should emerge.
That clearer picture might not last long. In 2027, the federal government will require colleges and universities to make changes to how they report student race and ethnicity. Among the changes is the addition of a Middle Eastern and North African category. Under the current standard, Middle Eastern and North African students are counted as white. As a result, white enrollment at some colleges and universities will appear to decline after 2027.
The new standards will also change the way universities treat Hispanic or Latino ethnicity on enrollment forms. Today, if students self-identify as Hispanic and white, they will be categorized as Hispanic. If students select Hispanic and white in 2027, they will be categorized as multiracial. The revised categories will muddy the impact of the Supreme Court’s decision. A drop in the number of Hispanic students reported could be due to the court’s ruling. Or it may result from the new way students will be counted.
Until universities and colleges adjust to the new guidelines about collecting and reporting race – and as long as students decline to provide their racial identities – the full effect of banning consideration of race in college admissions will remain a cloudy picture at best.
Karly Sarita Ford, Associate Professor of Education and Sociology, Penn State
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Health
10 Simple Changes You Can Make Today for Improved Health and Wellness
Improve your health and wellness with these simple changes to your daily routine.
Boost Your Wellbeing with These Easy Tips
Living a healthy lifestyle is important for our physical and mental well-being, but sometimes it can be overwhelming to know where to start. However, there are simple changes that we can make to our daily routines that can have a big impact on our health and wellness. Here are 10 simple changes you can make today to improve your health and wellness.
- Drink more water: Staying hydrated is key for our body’s systems to function properly. Aim for at least 8 glasses of water a day.
- Add more fruits and vegetables to your diet: Fruits and vegetables are packed with nutrients and antioxidants that can help protect against diseases. Aim for at least 5 servings a day.
- Move more: Regular exercise is important for maintaining a healthy weight, reducing stress, and improving overall health. Find activities that you enjoy and aim for at least 30 minutes of physical activity a day.
- Get enough sleep: Sleep is essential for our body to heal and regenerate. Aim for 7-9 hours of sleep each night.
- Reduce stress: Chronic stress can have negative effects on our physical and mental health. Find activities that help you relax and reduce stress, like meditation or yoga.
- Practice good hygiene: Good hygiene practices like washing your hands regularly and showering daily can help prevent the spread of germs and illnesses.
- Limit alcohol intake: Drinking too much alcohol can have negative effects on our liver and overall health. Limit your intake to no more than 1-2 drinks per day.
- Quit smoking: Smoking is a major cause of many diseases and can have negative effects on our health. Quitting smoking is one of the best things you can do for your health.
- Wear sunscreen: Protect your skin from the harmful effects of the sun by wearing sunscreen with at least SPF 30, especially when spending time outdoors.
- Connect with others: Social connections are important for our mental health and well-being. Make an effort to spend time with friends and family, or find a community group that interests you.
Making these simple changes to your daily routines can have a big impact on your health and wellness. Remember that small steps can lead to big changes. Start with one or two changes and gradually add more as you feel comfortable. With time, these habits will become a natural part of your daily routine, helping you to live a healthier and happier life.
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