If the Sun is able to keep Earth warm while being millions of miles away, shouldn’t it get warmer and warmer the closer you get to it (like when you go to space)? Like how it would get warmer if you were to approach a burning house for example?
In: Planetary Science
Heat is molecules getting energy and bouncing around more. Space doesn’t have (many) molecules. There is nothing to bounce around. Therefore it cannot “heat up” the same way Earth can heat up.
Funny enough, if you put a thermometer in space in direct sunlight it WILL heat up and you may think space is hot.
There are three ways for thermal energy to move. Convection, induction, radiation. Convection comes from hot air rising and moving across the room, induction comes from a hot thing touching something cooler. However both of these require some medium to work.
Space is empty, so there must be radiation heating.
Anything that has a temperature releases light, animals produce light with wavelength of 12000nm. We can only see from 700 to 380 nm. So we don’t see humans glowing.
As you heat something up, the wavelength produced decreases, and eventually it will be in the 700-380nm range and we see it glow. First red, then yellow, then white.
The sun is very hot, so it produces a lot of thermal light, this travels through space and hits the earth, releasing the energy. Light doesn’t need a medium to travel through
So, couple of things here.
It does get hot in the path of the sun. Very hot. Astronaut suits are white and have reflective visors for a reason. All that electromagnetic energy heats things up, so the suits are designed to reflect a lot of it and insulate the human meat bag inside.
The thing is, as soon as an object in Earth’s orbit moves into an area that’s fully shaded, it gets cold. Very cold. Good thing those spacesuits are insulated, because they also keep meat bags from freezing.
The issue is that without an atmosphere, there’s nothing holding all that heat in. So when you’re exposed to the source of energy, you get hit with a lot of it. And when you hide from it, you get exposed to such a small amount, you radiate energy out instead. Here, on the ground, the air holds that heat in. Especially moisture in the air. Deserts aren’t just hot in the daytime. Their temperature drops, a lot, at night.
Space is cold because it is mostly empty, so there isn’t enough matter to gain and retain heat.
But heat is still a problem in space, which is why space suits for EVA are designed with insulation and cooling to keep the wearer from getting too hot in the sun or too cold in the shade. There is also a cooling solution for space craft and stations that transfer heat from the hot side to the cool side to regulate the temperature. They also have tinted windows to help block harmful UV radiation.
The sun heats the ground, and the ground heats the air.
Space has neither, so the light just passes through.
If a photon does hit a stray gas or dust particle, it will quickly be remitted as a lower frequency photon.
The space between the Sun and the Earth *isn’t* cold because it isn’t *any* temperature at all. Space is nothing, and nothing can’t have a temperature. Stuff *in* space has a temperature. Anything i*n* space between the Sun and the Earth will actually be very hot unless it’s something is in between it and the Sun, in which case it will be very cold.
When we say space is cold, it’s kind of misleading because what we’re really taking about is the temperature of the very sparse bits of gas and dust in a given volume of space. Since there are so few molecules or bits of gas and dust in any given volume of space, it will have a low temperate, just like how it’s cold at the altitude planes fly at because the air is so thin.
Stuff *in* space can get very hot though. The sun-facing side of Mercury gets as hot as 800°F (430°C) while the side facing away from the Sun gets as cold as -290°F (-180°C). Earth is farther away from the Sun so it gets less concentrated energy, which means it doesn’t get as hot. Using the Moon as an example (since like Mercury, it has no atmosphere), the sunlit side of the Moon gets up to 250°F (121°C) in daylight and as cold as -208°F (-133°C) on the dark side.
So in summary, your instinct is mostly correct. Things *in* space are hotter the closer they are to the sun, unless something is blocking the sunlight, in which case they get very cold.
In space, the definition of temperature starts breaking down. That’s because when talking about temperature, you’re talking about the property of “stuff”. Air, water, rocks. Matter. Temperature is most commonly defined as kinetic energy of particles.
Vacuum of space is famously really empty. There’s not enough “stuff” to define it strictly as we do on earth. You get absolute nonsense like vacuum being 10 million degrees because the two protons per square kilometer have a lot of energy between them.
So you have to be very careful when talking about the temperature of space to define what you’re talking about.
If you put yourself between the earth and the sun, you’ll quickly find that you’re being heated as much as the earth is, because there’s sunlight shining on you. In fact, it’s quite difficult to cool down, because there’s very little to carry heat AWAY from you in the vacuum of space. And you’re not going to radiate more heat than you get until you’re, well, the temperature of the sun. As a human, I do not recommend being the temperature of the sun.
>Like how it would get warmer if you were to approach a burning house for example?
Well… That’s exactly what happens. That’s why Mercury is hotter than Earth.
A lot of these answers don’t seem simple, so I’ll try to say it in a simpler way.
Earth has an atmosphere that can hold the heat. Imagine you are in a cold house and you boil a pot of water with the lid on. The house will still feel cold but the inside of the pot will be hot. The fire that heats the pot is like the sun, and the lid keeping the heat in is like the atmosphere.
This also explains how rain works. The steam that rises to the top of the lid is like the clouds, and the water on the lid that drips back down is like the rain.
There is nothing to impart the heat to, it’s empty space. Actually this statement is technically incorrect but technically correct. Space isn’t completely empty but it’s very close to empty. There are tenuous gases and few and far between solid particles which is why space is cold but it’s not absolute zero, and why the temperature in outer space is not consistent. But for all intents and purposes, it is empty space. So a probe flying through space will be in a very cold environment, because there is next to nothing near it to be heated up by the Sun’s radiation, but the probe itself can be heated up by it.
There are several types of heating: heat by conduction, convection, and radiation. The first two require a medium – such as air – to heat up and then transfer heat to something else. In space, there is no medium to heat up, so we are left with only radiated heat.
Heat transfer via radiation occurs when light ( the light can be visible or invisible to the human eye) emitted by something hits something else and causes the molecules to become excited.
When you shine a flashlight at a wall and walk closer, the beam will become more concentrated. Just like a flashlight, the closer to the sun something gets, the more intensely it is illuminated, meaning that there is more energy being absorbed and thus more heat is transfered via radiation.
This is an oversimplified explanation that neglects some other important factors like how much an object absorbs or reflects radiation, but I think it answers the basic question.
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