Why is outer space cold

It is astonishing how a burning object from far away can cast its heat over such a large distance. If you were to stand for an extended period in such temperatures, you risk dying from heatstroke. But what puzzles the most is that outer space remains cold even when the earth scorches millions of kilometers away. So, why is space so cold if the sun is so hot? To understand this puzzling phenomenon, it is important to first recognize the difference between the two terms that are often used interchangeably: heat and temperature.

In simple terms, heat is the energy stored inside an object, while the hotness or coldness of that object is measured by temperature. So, when the heat is transferred to an object, its temperature rises. This heat transfer can happen through three modes: conduction, convection, and radiation. Heat transfer through conduction occurs in solids. As the solid particles are heated, they begin to vibrate and collide with one another, transferring heat in the process from hotter particles to colder ones.

Heat transfer through convection is a phenomenon observed within liquids and gases. This mode of heat transfer also occurs at the surface between solids and fluids. When the fluid is heated, the molecules rise upwards and carry the heat energy along with them. A room heater is the best example demonstrating convective heat transfer.

When the heater heats the surrounding air, the temperature of the air will increase and the air will rise to the top of the room. The cool air present at the top is forced to move down and get heated, creating a convection current. Heat transfer through radiation is a process wherein the object releases heat in the form of light. All materials radiate some amount of thermal energy based on their temperature.

At room temperature, all objects including us humans radiate heat as infrared waves. Cold is simply the absence of heat. Any spot in the universe that is sufficiently blocked from all heat sources will eventually cool down to freezing temperatures.

But points in space removed from heat sources aren't cold in the sense that they would quickly make you cold. Quick heat transfer requires contact or air, both lacking in space. As a result objects cool very slowly through the much slower mechanism of thermal radiation.

A human exposed to outer space in shadow without a space suit does not instantly freeze to a block of ice. But just for giggles, let's take a thermometer out in our starless void and check the reading. It will quickly tumble below zero and keep going until it reaches While that's pretty dang cold, it's not absolute zero , the coldest possible temperature. To reach that numbing number we'll need to keep going to By the way, the sensation we call heat is created by wriggling molecules.

If you overheat a meal in the microwave, the water molecules in your food will jiggle with enough fury to burn your tongue! At absolute zero atoms are essentially motionless.

Notice that our coldest parcel of outer space is 4. The source of that heat takes us back to the Big Bang As the fireball expanded and cooled, the first subatomic particles could form.

When these gathered into the first neutral atoms — a pivotal event that occurred about , years after the Big Bang — the radiant energy light bound up in the expanding universe broke free and streamed across all of space. We can't see the CMB because as the name implies, it glows in the microwave part of the spectrum.

But we've confirmed it's there and nailed down the temperature to five decimal places. Incredibly, physicists and astronomers predicted its existence and temperature before this remnant glow of the Big Bang was discovered in Finding it helped to confirm the origin of the universe in a blazingly hot, singular event billions of years ago.

All cold ultimately derives from outer space. The sun keeps our planet habitable. Read more of his work at duluthnewstribune. Astro Bob Astro Bob: How cold is outer space? Cold, yes, but it could be a lot colder.