The Knowledge
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.
Last Updated on March 13, 2026 by Daily News Staff
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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The Knowledge
Where Does Federal Money Go? The Biggest Costs Behind the Budget
Where does federal money go? Part two of our National Debt Explained series examines the biggest expenses in the 2025 budget and how spending connects to government borrowing.
The Knowledge | National Debt Explained, Part 2
When discussing debt, ask: Who borrowed the money? That question helps distinguish a family’s finances from the federal budget. Our first episode explained why your credit card balance is separate from the national debt. Now comes the next question: What does the federal government spend money on?
Much of it pays for retirement benefits, health coverage, national defense, public services, and interest on previous borrowing.
Social Security was the largest individual program in fiscal year 2025, costing approximately $1.6 trillion. But combine the major health care programs—including Medicare, Medicaid, and health insurance subsidies—and their spending reached about $1.8 trillion, exceeding Social Security alone. cbo.gov
The figures below cover October 1, 2024, through September 30, 2025.Major expense FY 2025 spending What it supports Social Security About $1.6 trillion Retirement, survivor, and disability benefits Medicare, net $988 billion Health coverage for older adults and certain people with disabilities Net interest $970 billion Cost of servicing publicly held federal debt, after subtracting interest income Discretionary defense $893 billion Military personnel, operations, equipment, and research Medicaid $668 billion Federal contribution toward health coverage and care for eligible people
These are selected expenses, not the entire budget. Medicare spending is shown after premiums and other offsetting receipts. The combined health care total already includes Medicare and Medicaid, so it should not be added to those rows. cbo.gov
The government also supports veterans’ health care, transportation, education, housing assistance, courts, law enforcement, scientific research, disaster response, and environmental protection. Nondefense discretionary spending totaled approximately $980 billion in 2025, covering many of these services. Some funding for these areas falls elsewhere in the budget. cbo.gov
Federal spending falls into three broad groups:
- Mandatory spending: Payments governed by existing eligibility rules and benefit formulas, including Social Security and major health programs.
- Discretionary spending: Funding lawmakers control through appropriations legislation, including most defense spending and many public services.
- Net interest: The expense of servicing publicly held federal debt, minus government interest income. cbo.gov
Interest deserves attention because it pays for borrowing already undertaken. In 2025, net interest exceeded discretionary defense spending. Congressional Budget Office
A program’s cost does not automatically translate into an equal increase in national debt. Taxes and other receipts finance much of federal spending. Social Security and Medicare’s hospital insurance program receive dedicated payroll taxes, while Medicare also collects premiums.
In 2025, federal spending totaled approximately $7 trillion, compared with $5.2 trillion in revenue. The roughly $1.8 trillion shortfall was the deficit, requiring borrowing. Understanding national debt therefore means examining both what government spends and what it collects. cbo.gov
Explore more explanations behind the headlines at STM Daily News, home of The Knowledge.
Sources for this episode
- CBO: The Federal Budget in Fiscal Year 2025 — Overview of spending, revenue, deficits, and debt interest.
- CBO: Mandatory Spending in Fiscal Year 2025 — Breakdown of Social Security, Medicare, Medicaid, and other benefit programs.
- CBO: Discretionary Spending in Fiscal Year 2025 — Defense spending and services including transportation, education, and veterans’ health care.
- CBO: Overview of the FY 2025 Budget Infographics — Highlights the largest expenses and broader budget trends.
Related reading
- U.S. Treasury: Understanding the National Debt — What federal debt represents and how borrowing works.
- U.S. Treasury: Understanding the National Deficit — Explains the difference between an annual deficit and accumulated debt.
- U.S. Treasury: Federal Spending — Additional context about where federal money goes.
Daily News
Whose Debt Is the National Debt?
The national debt isn’t Americans’ credit card balances added together. This simple explainer separates federal borrowing from household debt and explains the difference between debt and a deficit.
Last Updated on October 11, 2026 by Daily News Staff
The Knowledge | STM Daily News
When you hear “national debt,” do you picture everyone’s credit card balances added together? The name can create that impression, but the national debt and household debt measure different borrowing.
The U.S. national debt is money the federal government owes. Your personal credit card balance is not included.
Federal debt versus household debt
The Treasury defines national debt as the federal government’s total outstanding borrowing accumulated over the country’s history. Household debt covers borrowing by individuals and families, including mortgages, credit cards, auto loans, and student loans.
|Type of debt |Who borrowed? |Examples |
|————–|————————|————————————————–|
|National debt |Federal government |Outstanding Treasury securities |
|Household debt|Individuals and families|Credit cards, mortgages, auto loans, student loans|
Putting a $500 purchase on your credit card increases your personal balance. It does not add $500 to the national debt.
How does the national debt grow?
When federal spending exceeds tax collections and other revenue, the government runs a budget deficit. Treasury sells securities to borrow money to cover the gap.
Consider a simplified, hypothetical example: the government collects $5 trillion and spends $6 trillion in one year. That leaves a $1 trillion deficit requiring financing.
A deficit measures a shortfall over a period, usually a year. Debt measures outstanding borrowing accumulated over time. Repeated deficits generally increase that debt. Interest on existing borrowing is also a federal expense.
Does paying off your credit card reduce the national debt?
Paying off a card reduces what you owe your lender. It does not directly repay Treasury borrowing. Household debt and government debt can influence the same economy, but they remain separate obligations.
When discussing debt, ask: Who borrowed the money? That one question helps distinguish a family’s finances from the federal budget.
Find more explanations of the ideas behind the headlines at STM Daily News, home of The Knowledge.
Sources
● U.S. Treasury: Understanding the National Debt
● U.S. Treasury: Understanding the National Deficit
● Federal Reserve Bank of New York: Household Debt and Credit Report
Science
October Meteor Showers Give Phoenix Skywatchers a Reason to Look Up
Phoenix skywatchers have several chances to catch October’s meteor showers. Here’s when to watch the Taurids and Orionids—and how moonlight affects the view.
Last Updated on October 10, 2026 by Daily News Staff
PHOENIX — October is bringing several opportunities to spot shooting stars over the Valley, with the Draconids reaching their October 8–9 peak and more meteor activity ahead.
The Draconids remain active through October 10, although viewers should expect a light display as the peak passes. Under favorable conditions, the shower typically produces only a handful of meteors per hour. timeanddate.com
Next, the Southern Taurids have an annual activity peak around October 14. Known for occasional bright fireballs, the shower continues into November. The stronger Orionids peak on the night of October 21 into the morning of October 22, typically producing 10–20 meteors per hour under dark skies. A bright Moon will interfere with this year’s display. American Meteor Society
The Orionids originate from debris left by Halley’s Comet. For Phoenix viewers, the best opportunity will be after moonset and before dawn, weather permitting. City lights will further reduce the number visible. amsmeteors.org
NASA recommends finding a viewing area away from streetlights, allowing about 30 minutes for eyes to adjust, and watching a broad stretch of sky. No telescope is needed—just a comfortable chair and patience. NASA Science
ECurious about what’s happening above us? Explore more space stories and science explainers in The Knowledge at STM Daily News.xplore more space, science and everyday
