You're listening to Sleep Tight Science.
Did you know that when you're eating lunch in London Ontario, someone in Sydney Australia, is already asleep?
And it's actually tomorrow there?
What?
Hello friends and welcome back to Sleep Tight Science a bedtime show that answers your questions about science.
In this episode, we are going to learn about time zones, how they work.
Why do we have them?
What happens when you fly through multiple time zones?
And what exactly is jet lag?
Maybe you video called a grandparent or cousin who lives far away and realized it was the middle of the night.
Where they are.
Or perhaps you've traveled by plane to a distant place and felt strangely tired, even though your watch said it was morning.
Or maybe you've wondered why someone in Vancouver is eating breakfast while you're already eating dinner.
Time zones can seem confusing at first.
All those different clocks showing different times.
People talking about being ahead or behind.
But they actually solve a really important problem.
One that we'll explore together. in this episode.
Time zones are where science meets human coordination.
The science part is Earth's rotation, our planet spinning once every 24 hours, which means the Sun can only shine on half of Earth at any moment.
The human part is our need to organize our days, coordinate with each other, catch trains and planes on time and generally agree on what three o'clock means.
First, we'll discover what life was like before time zones existed and why they became necessary.
Then we'll explore exactly how time zones work, the math, the maps, and the rules.
Next, we'll find out what happens to your body when you fly across multiple time zones and why jet lag makes you feel so strange.
And finally, we'll discover some fun time zone facts from around the world.
Thank you to Franklin from London, Ontario for submitting this excellent question.
And a quiet thank you to Mac, age nine from Albuquerque, New Mexico, for introducing our show.
And to all our curious friends who send in questions.
You help us learn together.
Let's find a comfy spot and take one easy breath in and out.
Let's start with what's happening right now.
Earth is spinning.
It completes one full rotation every 24 hours, which means different parts of our planet face the Sun at different times.
The Sun's light can only illuminate half of Earth at any given moment.
The half facing the Sun experiences daylight. while the half-facing away is in darkness.
Because Earth is constantly rotating, the line between light and shadow sweeps across the planet's surface.
When London Ontario rotates into direct sunlight and the Sun reaches its highest point overhead, solar noon, Vancouver is just rotating into the Sun's rays at sunrise.
London, England has already rotated past that point and is approaching sunset.
Tokyo has rotated completely away from the sun into nighttime darkness.
Now imagine if everyone, everywhere, used exactly the same clock showing 12 noon.
In London, Ontario, that noon would match the sun's highest position.
But in Vancouver, noon would mean sunrise.
In Tokyo, noon would mean the middle of the night.
The same word would describe completely different positions of the sun.
For most of human history, this wasn't really a problem.
Each town and city simply set its own clock by the sun.
When the sun reached its highest point in the sky, that was noon, or 12 o'clock.
This is called solar noon.
If you lived in a small area and rarely traveled far, this worked perfectly fine.
But towns even 50 kilometers apart would have clocks showing slightly different times because the sun reached its highest point at slightly different moments for each location.
The difference might only be a few minutes, but those minutes mattered when something important happened.
Trains.
In the 1800s, Railroads began connecting distant cities.
Suddenly, people could travel hundreds of kilometers in a single day.
This created a massive problem for train schedules.
Imagine trying to write a timetable when every single town along the route kept its own time.
Let's say you're running a train from London, Ontario to Toronto, about 200 kilometers apart.
Because of Earth's rotation, solar noon happens roughly 8 minutes later in London than in Toronto.
So if both cities kept sun time, their clocks would be 8 minutes different.
Now imagine a train route with 20 stops. each with its own slightly different time.
How would you write a schedule?
How would passengers know when to arrive at the station?
It was more than inconvenient.
It was actually dangerous.
Train crashes happened because of confusion about times.
Trains leaving at the same time from different cities could end up on the same track because those same times were actually different.
In New England alone, there were over 300 train accidents in the mid-1800s.
Many blamed on time confusion.
The railroads needed a solution.
Divide the world into zones.
Within each zone, everyone would agree to use the same time, even if it didn't match solar noon exactly.
North American railroads adopted this system in 1883 and by the early 1900s it became the worldwide standard.
So time zones are a human invention designed to solve a coordination problem created by Earth's rotation.
They're a compromise between the science of how Earth spins and the practical need for everyone in a region to agree on what time it is.
Now that we understand why we need time zones, let's explore how they actually work.
The system is based on some straightforward math combined with Earth's geography.
Earth is a sphere that rotates 360 degrees in 24 hours.
If you divide 360 by 24, you get 15, which means Earth rotates 15 degrees every hour.
This is the foundation of time zones.
Each time zone covers roughly 15 degrees of longitude.
Longitude lines are imaginary lines that run from the North Pole to the South Pole like the segments of an orange.
They're measured in degrees east or west from a starting point.
That starting point is called the Prime Meridian, and it runs through Greenwich, England.
Greenwich is at zero degrees longitude. and it's where the time zone system begins.
The time there is called Greenwich Mean Time GMT or, more officially Coordinated Universal Time UTC.
From Greenwich, time zones count outward.
If you travel east, toward Asia and Australia, you move ahead in time.
If you travel west, toward the Americas, you move backward in time.
Each zone is roughly one hour different from its neighbor.
For example, London, Ontario is about 75 degrees west of Greenwich.
That puts it in a time zone that is five hours behind GMT.
When it's noon in Greenwich, it's 7am in London, Ontario.
Sydney, Australia is about 150 degrees east of Greenwich, which puts it 10 or 11 hours ahead, depending on the season.
When it's noon in Greenwich, it's 10pm or 11pm in Sydney, and actually the next day.
But time zones aren't perfect straight lines running north to south.
That's because politics, geography, and practicality matter.
Countries want to keep their territory in as few time zones as possible.
So time zone boundaries often follow national or regional borders instead of strict longitude lines.
China is a dramatic example.
The entire country uses one time zone, even though it's wide enough to span five.
This means the sun rises very early in eastern China and very late in western China, but everyone's clock shows the same time.
Some places use unusual offsets.
Newfoundland and Labrador is three and a half hours behind GMT.
Notice that half hour?
India is five and a half hours ahead.
Nepal is five hours and 45 minutes ahead, one of only two places with a 45-minute offset.
These unusual times help put their capitals closer to solar noon.
In North America, you might have heard of time zone names.
Pacific, Mountain, Central, and Eastern.
Each one is an hour apart, but there's an extra complication.
Daylight saving time.
During summer months, many places shift their clocks forward by one hour.
So Eastern Standard Time, or EST, becomes Eastern Daylight Time EDT, changing from five hours behind GMT to only four hours behind.
Not all places do this, which means the time difference between two cities changes can actually change depending on the season.
Finally, there's the international date line, which runs roughly along the 180 degree longitude line in the Pacific Ocean.
This is where the calendar date changes.
Cross it westward and you jump forward a whole day.
Cross it eastward and you go back a day.
It zigzags around countries and island groups so that no nation gets split between two different dates.
So time zones create an organized system where everyone in a region shares the same time, making coordination possible across a spinning planet.
Now let's explore what happens when you actually travel through multiple time zones, especially by plane.
This is where time zones stop being abstract and start affecting your body.
Imagine flying from London, Ontario to London, England, a journey that crosses five time zones.
You board an evening flight at 7 p.m. and fly for about seven hours.
When you land, your body feels like it's 2 a.m.
You've been awake for a long time and you're exhausted.
But when you look at the local clocks, they say 7 a.m.
The sun is up, people are having breakfast, and your day is just beginning.
Your body is screaming bedtime, but the world around you says good morning.
This confusion is called jet lag and it happens because your internal body clock, your circadian rhythm, is still set to your home time zone.
Your circadian rhythm is like a biological clock that runs on a roughly 24-hour cycle.
It's controlled by a special part of your brain that responds to light and darkness, meal times and activity patterns.
This internal clock tells your body when to feel alert, when to feel hungry and when to feel sleepy.
When you suddenly jump across time zones, your body clock doesn't instantly reset.
It takes time to adjust.
Jet lag isn't just feeling tired.
It's a real biological confusion that affects sleep, appetite, digestion, mood, and concentration.
You might feel exhausted during the day but wide awake at 3 a.m.
You might feel hungry at strange times or not hungry at mealtimes.
Your brain might feel foggy and your body just feels off.
Interestingly, flying east tends to cause worse jet lag than flying west.
When you fly east, you're losing time.
The day gets shorter and you skip ahead.
Your body finds this harder to adjust to.
Flying west means gaining time.
The days get longer, which your body handles more easily.
Scientists think this is because our natural circadian rhythm is actually slightly longer than 24 hours.
So extending the day feels more natural than shortening it.
How long does jet lag last?
A rough rule is about one day per time zone crossed.
So if you crossed five time zones, it might take five days to fully adjust.
Some people recover faster, others slower.
The best way to reduce jet lag is to expose yourself to bright light at the right times.
Try to adapt to the new schedule quickly stay hydrated, and get some exercise.
Flight attendants and pilots who cross time zones constantly become experts at managing this.
They use light strategy, rest when they can and learn to function even when their body clock is confused.
Time zones also affect people who never leave home.
If you've ever had a video call with someone far away, someone always has an inconvenient time.
A 9am meeting in Toronto is 6am in Vancouver and 11pm in Sydney.
Someone's always getting up early or staying up late.
Now that you understand how time zones work, let's learn some of the fascinating and unusual exceptions around the world.
Did you know that France has more time zones than any other country?
Twelve in total.
This isn't because France itself is so wide, but because France controls overseas territories scattered across the globe, from the Caribbean to the Indian Ocean, to the Pacific.
Russia comes in second with 11 time zones, stretching over 10,000 kilometers.
When people in Moscow are eating breakfast, people in Vladivostok are getting ready for bed.
Did you know that the island nation of Kiribati made headlines in 1995 when it moved the international date line to keep all its islands on the same calendar date?
This made Kiribati the first country to see each new day and celebrate each new year.
Nepal uses one of the world's most unusual time zones, UTC plus 545.
That's right, 5 hours and 45 minutes ahead of Greenwich.
This quirky offset was chosen to put the capital city of Kathmandu closer to solar noon.
Nepal is one of only two places with a 45-minute offset.
Spain's time zone is particularly interesting.
Geographically, Spain should be in the same time zone as the United Kingdom.
They're at similar longitudes.
But Spain uses Central European time instead, one hour ahead.
This happened during World War II, when Spain aligned its clocks with Nazi Germany, and the country simply never changed back.
Did you know that Arizona doesn't observe daylight saving time?
But here's where it gets really confusing.
The Navajo Nation, which is within Arizona, does observe it.
This creates a patchwork where driving through certain areas means changing your clock multiple times.
And here's a fun fact.
Because of time zones and the international date line, you could theoretically celebrate New Year's Eve multiple times by flying westward around the world, staying just ahead of midnight as it sweeps across the planet.
Would you like to try that someday?
Here's a wave to some of our question askers.
Theodore, age 9.
Quinn Dunn.
Nolan, five years old, from rural Alberta.
Felix, nine years old, from Queensland, Australia.
Sol in California.
Zenluka, nine years old, from Montreal, Quebec.
Nordy, age five.
Michaela Cummings, age five, in Foxborough, Massachusetts.
Liliana L., age 7, from Los Angeles County, California.
Alexi, age 7, from Haroldwood, England.
Tristan Wong, age 11, and Michael Wong, age 9, from Edmonton, Alberta.
Joshua Sinai, 6 years old, from Santa Barbara, California.
And Alex, 6 1⁄2 years old, in Toronto.
Thank you for asking questions that spark our curiosity and keep us learning to submit your questions.
Ask your parents to help you write us a note to the email address in our episode notes.
You can also visit our website and send a message that way.
Also, don't forget to leave us a review.
It helps other people find our show.
In this episode, we learned how time zones work.
We discovered why we need them.
Before time zones, every town kept its own time by the sun, which made train schedules impossible.
We learned how time zones divide earth into 24 sections roughly 15 degrees wide, with each zone one hour different from its neighbors.
We found out what happens when you fly through multiple time zones.
Your body clock gets confused, causing jet lag, because your internal circadian rhythm doesn't match the local time.
And we explored some time zone.
Fun facts like France having 12 different time zones and some places using 45-minute offsets.
Time zones are a human solution to a spinning Earth problem.
Take a slow, deep breath in and let it out gently.
Maybe tonight you'll dream of riding on Earth as it spins through space, watching invisible time zone.
Ribbons sweep across the surface, each one marking where clocks tick to a different hour.
You might become a train conductor in 1883, celebrating as a new time zone system finally makes your impossible schedule work perfectly.
Perhaps you'll fly westward across the world, chasing the sunset, never letting it dip below the horizon, celebrating midnight over and over in different places.
You could stand with one foot in today and one foot in tomorrow balanced, right on the international date line, in the middle of the Pacific Ocean.
Maybe you'll shrink down and explore the intricate gears of your internal body clock, watching it slowly reset after a long journey, adjusting to new patterns of light and dark.
Or you might watch the sun move across the sky while clocks in different cities tick at their own rhythms, some showing morning, some showing evening, all at the same moment.
Your imagination can take you anywhere in space and time.
Thank you for spending this time with us.
From Cheryl and Clark, good night.
Sleep tight.
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