# What is body temperature?

An episode of [Science for Kids / Science's Not Boring: The Kids Science Podcast](https://invisiblenetwork.ai/podcast/1896928296), 18 Sep 2026, 14 min.

Audio: https://www.buzzsprout.com/2624612/episodes/19789008-what-is-body-temperature.mp3

Have you ever wondered why you shiver in the freezing winter snow and drip with sweat in the blazing summer sun? Your body is actually performing an incredible, invisible magic trick! Inside your brain, there is a tiny, almond-sized control center called the hypothalamus that works around the clock to keep your insides at the absolute perfect temperature. Join Mira and Finn on Science is Not Boring as they uncover the amazing secrets of how our bodies survive extreme hot and cold environments! You'll discover why humans are mostly water, how a fever actually helps you fight off sick germs like a fiery superpower, and the crazy history of the very first foot-long glass thermometer. Plus, we'll meet some of the most extreme animals on the planet, including a shiny desert ant that wears a mirror suit and an Alaskan wood frog that survives winter by freezing completely solid like a living ice cube! Get ready for a mind-blowing adventure into the science of homeostasis and learn why staying warm-blooded is your body's cleverest survival trick!

## Transcript

[0:00] SPEAKER_00: Welcome to Science Is Not Boring by Kidopoly.com.
[0:03] SPEAKER_00: I'm Mira.
[0:04] SPEAKER_00: And I'm Finn.
[0:06] SPEAKER_00: Before we dive in, we have a massive shout-out today.
[0:09] SPEAKER_00: A big hello to six-year-old Daniel in Massachusetts.
[0:13] SPEAKER_01: Thanks for listening, Daniel.
[0:15] SPEAKER_01: We hear you love learning cool science facts with us on the show.
[0:19] SPEAKER_00: And Daniel, you are going to love today's topic.
[0:22] SPEAKER_00: Because today we are talking about your body's most amazing, invisible magic trick.
[0:29] SPEAKER_01: Wait, magic?
[0:31] SPEAKER_01: Do we have secret powers that nobody told me about?
[0:35] SPEAKER_00: Sort of.
[0:36] SPEAKER_00: Picture this.
[0:37] SPEAKER_00: You are standing outside in the freezing snow, shivering in a massive winter blizzard.
[0:44] SPEAKER_01: Okay, I am picturing it.
[0:46] SPEAKER_01: I am freezing, and my nose is like an icicle.
[0:49] SPEAKER_00: Now imagine you are stuck in the boiling summer sun, surrounded by hot desert sand, dripping with sweat.
[0:57] SPEAKER_01: Now I am melting.
[0:59] SPEAKER_01: I need a massive glass of ice water.
[1:02] SPEAKER_00: But here is the mind-blowing part.
[1:05] SPEAKER_00: Deep inside your body, near your heart and brain, your temperature barely changes at all.
[1:11] SPEAKER_00: Whether you are in an ice storm or a desert, your body works incredibly hard to stay exactly the same.
[1:18] SPEAKER_01: Wait, no way.
[1:20] SPEAKER_01: You are saying even if I am standing in a freezer, my insides aren't freezing.
[1:25] SPEAKER_00: Exactly! Today we are going to explore how your body handles extreme heat, freezing cold, and why staying warm-blooded is one of your cleverest survival tricks.
[1:37] SPEAKER_01: So who is in charge of this?
[1:39] SPEAKER_01: Is there a tiny thermostat hidden inside me?
[1:42] SPEAKER_00: Yes! Let's find out how it works.
[1:44] SPEAKER_00: So, let's start with the absolute basics.
[1:47] SPEAKER_00: For a long time, doctors have said your body's normal temperature is 98.6 degrees Fahrenheit, or 37 degrees Celsius.
[1:57] SPEAKER_01: Okay, but who figured that out?
[1:59] SPEAKER_01: Did someone just walk around measuring a bunch of people?
[2:03] SPEAKER_00: That is exactly what happened.
[2:06] SPEAKER_00: A German doctor named Carl Wunderlich figured it out way back in 1868.
[2:12] SPEAKER_01: 1868?
[2:14] SPEAKER_01: Did they even have good thermometers back then?
[2:17] SPEAKER_01: I feel like they would just use a hot rock or something.
[2:20] SPEAKER_00: They had thermometers, but they were ridiculous.
[2:24] SPEAKER_00: Carl Wunderlich's thermometer was a whole foot long.
[2:28] SPEAKER_00: That is 12 inches of heavy glass.
[2:31] SPEAKER_01: A foot long?
[2:33] SPEAKER_01: Where did he even put it?
[2:35] SPEAKER_01: You can't stick that in someone's mouth.
[2:38] SPEAKER_00: No, he put it under their armpit.
[2:40] SPEAKER_00: And he didn't just measure a few people.
[2:43] SPEAKER_00: He meticulously took temperature readings from 25,000 different people.
[2:49] SPEAKER_01: Twenty-five thousand?
[2:51] SPEAKER_01: That must have taken years!
[2:53] SPEAKER_00: It did.
[2:54] SPEAKER_00: He recorded over one million different temperature readings.
[2:58] SPEAKER_00: And it took 20 whole minutes just to get one single reading from that giant thermometer.
[3:04] SPEAKER_01: Oh, 20 minutes! Just sitting there completely still with a foot-long glass stick under your arm?
[3:11] SPEAKER_01: That sounds so boring.
[3:13] SPEAKER_00: Yep, but all that incredible data gave us the famous 98.6 degrees measurement.
[3:19] SPEAKER_01: So if that is our target temperature, who is driving the spaceship?
[3:24] SPEAKER_01: How does my body know if I am too hot or too cold?
[3:27] SPEAKER_00: It is all controlled by a tiny, super smart part of your brain called the hypothalamus.
[3:33] SPEAKER_01: Hypothalamus.
[3:36] SPEAKER_01: That sounds like a dinosaur.
[3:38] SPEAKER_01: How big is it?
[3:39] SPEAKER_00: It is tiny, about the size of an almond, sitting right near the centre of your brain.
[3:45] SPEAKER_00: It constantly measures the temperature of the blood flowing past it.
[3:49] SPEAKER_01: Haha, so an almond is controlling my whole body's temperature?
[3:54] SPEAKER_01: What happens if I go outside on a super hot day and start running around?
[3:59] SPEAKER_00: The second your blood gets even a tiny bit warmer than normal, the almond sounds the alarm.
[4:04] SPEAKER_00: The hypothalamus instantly sends signals to cool you down.
[4:08] SPEAKER_00: How?
[4:09] SPEAKER_00: Does it turn on an internal fan?
[4:12] SPEAKER_00: Even better! It activates your sweat glands.
[4:15] SPEAKER_00: A normal human body is covered in two to four million tiny sweat glands.
[4:21] SPEAKER_01: Four million?
[4:22] SPEAKER_01: That is a lot of leak holes.
[4:25] SPEAKER_01: I must be mostly water.
[4:26] SPEAKER_00: You actually are mostly water.
[4:29] SPEAKER_00: When these glands open, they pump out salty water onto your skin.
[4:34] SPEAKER_00: As the sweat evaporates into the air, it pulls the heat right off your body.
[4:39] SPEAKER_01: But how much can a person actually sweat?
[4:42] SPEAKER_01: Like, could I sweat a whole swimming pool?
[4:45] SPEAKER_00: Not a pool, but a lot.
[4:47] SPEAKER_00: An average person sweats between 0.8 and 1.4 litres an hour when exercising.
[4:53] SPEAKER_00: But in 1984, an Olympic runner named Alberto Salazar set a crazy record.
[5:00] SPEAKER_00: Ooh, how much did he sweat?
[5:02] SPEAKER_00: He sweat an unbelievable 3.71 litres in just one single hour.
[5:08] SPEAKER_01: 3.7 litres?
[5:11] SPEAKER_01: That is almost two huge soda bottles of sweat coming out of one person.
[5:16] SPEAKER_01: Haha, exactly.
[5:18] SPEAKER_00: It is an incredibly powerful cooling system.
[5:21] SPEAKER_00: But what if the opposite happens?
[5:23] SPEAKER_00: What if you are trapped in the freezing cold?
[5:27] SPEAKER_01: The Ormond brain panics and turns on a heater.
[5:30] SPEAKER_00: Pretty much.
[5:31] SPEAKER_00: It shifts into survival heating mode.
[5:34] SPEAKER_00: First, it tells your blood vessels to shrink, keeping your warm blood deep inside, near your important organs like your heart.
[5:42] SPEAKER_01: Is that why my fingers and toes get so freezing cold in the snow?
[5:46] SPEAKER_00: Yes, your body is prioritizing your core.
[5:49] SPEAKER_00: And if you are still too cold, the hypothalamus sends electrical signals to your muscles, making them contract and relax super fast.
[5:57] SPEAKER_01: Wait, is that what shivering is?
[6:00] SPEAKER_01: Just my muscles twitching.
[6:02] SPEAKER_00: Exactly! When you shiver, your muscles are firing 10 to 20 times every single second.
[6:08] SPEAKER_00: This means your muscles burn energy to create heat and warm your blood back up.
[6:13] SPEAKER_01: But wait, what if I am sick?
[6:16] SPEAKER_01: When I have a fever, I get super hot and sweaty on purpose.
[6:20] SPEAKER_01: Is the almond broken?
[6:22] SPEAKER_01: Great question!
[6:24] SPEAKER_00: The hypothalamus isn't broken at all.
[6:26] SPEAKER_00: It is actually raising your temperature on purpose.
[6:30] SPEAKER_00: On purpose?
[6:31] SPEAKER_01: Why would my body want to cook me?
[6:34] SPEAKER_00: Because germs, like viruses and bacteria, absolutely hate the heat.
[6:39] SPEAKER_00: When your white blood cells spot an invader, they release special chemicals called pyrogens.
[6:45] SPEAKER_01: Pyrogens?
[6:47] SPEAKER_01: That sounds like a fiery superpower.
[6:49] SPEAKER_01: Like a dragon spell.
[6:51] SPEAKER_00: It actually means fire maker.
[6:53] SPEAKER_00: The pyrogens travel to the hypothalamus and reprogram the thermostat.
[6:58] SPEAKER_00: It tricks your brain into thinking normal is 102 degrees.
[7:03] SPEAKER_01: So then my body shivers to reach that new hot target.
[7:07] SPEAKER_01: Is that why I feel freezing cold when I have a fever?
[7:10] SPEAKER_00: Exactly! Your brain thinks you are too cold, so it turns up the heat to cook the germs.
[7:16] SPEAKER_00: But humans aren't the only ones with extreme temperature tricks.
[7:20] SPEAKER_01: Really?
[7:21] SPEAKER_01: What is the most extreme animal?
[7:23] SPEAKER_00: Meet the Saharan silver ant.
[7:25] SPEAKER_00: It lives in one of the hottest deserts on Earth.
[7:28] SPEAKER_00: It waits until midday when the sand reaches a scorching 158 degrees Fahrenheit.
[7:34] SPEAKER_01: 158?
[7:36] SPEAKER_01: That would instantly fry an egg.
[7:39] SPEAKER_01: How does it not melt?
[7:40] SPEAKER_00: It is covered in microscopic silver hairs shaped like triangular prisms.
[7:46] SPEAKER_00: They act like mirrors, reflecting the sun's deadly radiation right off the ant's body.
[7:51] SPEAKER_01: A shiny mirrored desert ant.
[7:54] SPEAKER_01: What about the cold?
[7:56] SPEAKER_01: What is the best animal at freezing?
[7:58] SPEAKER_00: The Alaskan wood frog.
[8:00] SPEAKER_00: When winter arrives, the frog doesn't hide deep underground.
[8:04] SPEAKER_00: It just tucks under some leaves and freezes solid.
[8:07] SPEAKER_00: Solid?
[8:08] SPEAKER_00: Like an actual ice cube?
[8:10] SPEAKER_00: Yes.
[8:11] SPEAKER_00: Up to 70% of the water inside its body turns into ice.
[8:15] SPEAKER_00: Its heart completely stops beating and it stops breathing for up to seven months.
[8:21] SPEAKER_00: But is it dead?
[8:23] SPEAKER_00: Nope.
[8:24] SPEAKER_00: As it freezes, the frog floods its cells with huge amounts of glucose, which is a sugar.
[8:30] SPEAKER_00: The sugar acts like antifreeze, keeping the inside of the cells safe so they don't burst.
[8:35] SPEAKER_01: Seven months frozen solid with no heartbeat.
[8:39] SPEAKER_01: Saved by sugar.
[8:41] SPEAKER_01: That wood frog is basically a magical zombie.
[8:45] SPEAKER_00: A very clever, very alive zombie.
[8:48] SPEAKER_00: It is the ultimate example of extreme temperature control.
[8:52] SPEAKER_00: But even without freezing solid, our human bodies are doing a balancing act every single second.
[8:59] SPEAKER_01: So my body is constantly adjusting the dials just to keep me perfectly warm.
[9:04] SPEAKER_00: Exactly! Scientists call this balance homeostasis.
[9:08] SPEAKER_00: It comes from Greek words meaning same and steady.
[9:12] SPEAKER_00: Without homeostasis, a hot day would literally cook our insides, because the proteins in our blood only work at that perfect sweet spot.
[9:23] SPEAKER_01: That means my body is basically a high-tech spacesuit, keeping me perfectly safe from the environment.
[9:30] SPEAKER_00: That is a brilliant way to look at it.
[9:32] SPEAKER_00: But here is one more wild fun fact to wrap your head around before our quiz.
[9:37] SPEAKER_00: Hit me with the facts.
[9:38] SPEAKER_00: Remember Carl Wunderlich and his 1 million armpit readings from 1868?
[9:44] SPEAKER_01: Of course, with the ridiculous foot-long glass thermometer.
[9:48] SPEAKER_00: Well, modern scientists recently looked at huge amounts of data from the 1860s all the way to today.
[9:56] SPEAKER_00: And they discovered humans are actually cooling down.
[10:00] SPEAKER_01: Cooling down?
[10:02] SPEAKER_01: Like we are turning into the wood frog?
[10:04] SPEAKER_01: Just a tiny bit.
[10:06] SPEAKER_00: Over the last 150 years, the average human body temperature has dropped to around 97.9 degrees Fahrenheit.
[10:15] SPEAKER_01: Wait, so the famous 98.6 number is totally outdated.
[10:20] SPEAKER_00: Yep.
[10:20] SPEAKER_00: Better medicine, cleaner water, and indoor heating mean our bodies don't have to fight off as many infections.
[10:28] SPEAKER_00: So we don't run quite as hot anymore.
[10:30] SPEAKER_01: Wow, so we are literally cooler than people from the past.
[10:34] SPEAKER_00: Alright, Finn, it's time for the quiz.
[10:36] SPEAKER_00: Let's see how much you remember.
[10:38] SPEAKER_01: Okay, I'm ready.
[10:39] SPEAKER_01: Fire away.
[10:40] SPEAKER_00: First question.
[10:42] SPEAKER_00: What year did Carl Wunderlich measure body temperatures?
[10:49] SPEAKER_00: Next one, what is the name of the almond sized part of the brain that acts as your thermostat?
[10:59] SPEAKER_00: Question three.
[11:00] SPEAKER_00: How many litres of sweat did Olympic runner Alberto Salazar lose in just one hour?
[11:11] SPEAKER_00: Here's number four.
[11:12] SPEAKER_00: What special chemicals tell your brain to cause a fever?
[11:19] SPEAKER_00: Last question.
[11:21] SPEAKER_00: What type of animal can freeze completely solid in the winter and thaw out in the spring?
[11:30] SPEAKER_00: Great job! Let's go through the answers.
[11:34] SPEAKER_00: The first answer is Carl Wunderlich did his famous measurements in 1868.
[11:40] SPEAKER_00: For question two, the almond size thermostat in your brain is the hypothalamus.
[11:46] SPEAKER_00: Number three, the answer is Alberto Salazar swept an amazing 3.71 litres in one hour.
[11:56] SPEAKER_00: Question four.
[11:57] SPEAKER_00: The fire-making chemicals that trigger a fever are called pyrogens.
[12:02] SPEAKER_00: And the final answer is the Alaskan wood frog is the incredible animal that freezes solid.
[12:09] SPEAKER_01: Wow! I will never complain about shivering in the cold or sweating in the heat ever again.
[12:15] SPEAKER_01: My body is working so hard to protect me.
[12:19] SPEAKER_00: It really is.
[12:20] SPEAKER_00: From sweating out litres of water to shivering your muscles 20 times a second, your body is an absolute powerhouse of survival.
[12:29] SPEAKER_01: And the wood frog is still my favourite part.
[12:32] SPEAKER_01: A totally frozen frog turning into a living ice cube is just the coolest thing ever.
[12:38] SPEAKER_00: If you loved learning about the frozen wood frog and your brain's amazing thermostats, please leave us a five-star review.
[12:46] SPEAKER_01: Yeah, just scroll down on your podcast app and tap those five stars.
[12:51] SPEAKER_01: It helps other kids find the show and join the adventure.
[12:55] SPEAKER_00: Oh, and don't forget to head over to our site, kidopoly.com.
[12:59] SPEAKER_00: We have tons of fun learning games and activities waiting for you there.
[13:03] SPEAKER_01: And if you want a shout out on the show, or just want to tell us your absolute favourite science fact, send us an email at hello at kidopoly.com.
[13:13] SPEAKER_00: We love hearing from you.
[13:15] SPEAKER_00: Thanks for exploring the incredible science of your body with us today.
[13:19] SPEAKER_01: See you next time on Science Is Not Boring.
[13:23] SPEAKER_01: Bye everyone.

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