热辐射听起来就像你在物理测试中看到的一个令人讨厌的术语。实际上，这是一个每个人在物体发热时经历的过程。它在工程中也称为“热传递”，在物理学中也称为“黑体辐射”。宇宙中的一切都散发出热量。有些东西比其他东西散热更多。如果一个物体或过程高于绝对零度，它就会发热。鉴于空间本身只能是2或3度开尔文（相当冷酷！），称其为“热辐射”似乎很奇怪，但这是一个实际的物理过程。热辐射可以通过非常敏感的仪器测量 – 基本上是高科技温度计。辐射的特定波长将完全取决于物体的确切温度。在大多数情况下，发射的辐射不是你能看到的（我们称之为“光学光”）。例如，非常热和高能量的物体可能在X射线或紫外线中非常强烈地辐射，但在可见（光学）光中可能看起来不那么明亮。一个非常有能量的物体可能发射伽马射线，我们绝对看不到它，其次是可见光或X射线光。在天文学领域中最常见的传热例子是恒星做什么，特别是我们的太阳。它们闪耀并散发出巨大的热量。我们的中心恒星（约6,000摄氏度）的表面温度负责产生到达地球的白色“可见”光。 （由于大气影响，太阳呈现黄色。）其他物体也发出光和辐射，包括太阳系物体（主要是红外线），星系，黑洞周围的区域和星云（气体和尘埃的星际云）。我们日常生活中的热辐射的其他常见例子包括加热时炉顶上的线圈，熨斗的加热表面，汽车的电机，甚至人体的红外辐射。当物质被加热时，动能被赋予构成该物质结构的带电粒子。颗粒的平均动能称为系统的热能。这种赋予的热能将导致粒子振荡和加速，从而产生电磁辐射（有时称为光）。在一些领域中，当描述通过加热过程产生电磁能（即辐射/光）时，使用术语“热传递”。但这只是从略微不同的角度看待热辐射的概念，而这些术语实际上是可以互换的。黑体物体是那些具有完全吸收每种波长的电磁辐射的特定性质的物体（意味着它们不会反射任何波长的光，因此称为黑体），并且它们在被加热时也将完美地发光。根据维恩定律确定发射的光的特定峰值波长，该定律表明发射的光的波长与物体的温度成反比。在黑体物体的特定情况下，热辐射是来自物体的光的唯一“光源”。像太阳这样的物体，虽然不是完美的黑体发射体，但确实具有这样的特性。太阳表面附近的热等离子体产生热辐射，最终使其作为热和光进入地球。在天文学中，黑体辐射有助于天文学家理解物体的内部过程，以及它与当地环境的相互作用。其中一个最有趣的例子是由宇宙微波背景发出的。这是大爆炸期间消耗的能量的残余辉光，发生在大约137亿年前。它标志着年轻的宇宙在早期的“原始汤”中已经冷却到足以使质子和电子结合形成中性氢原子的点。我们可以看到来自早期材料的辐射是光谱微波区域的“发光”。
Thermal radiation sounds like one a geeky term you’d see on a physics test. Actually, it’s a process that everyone experiences when an object gives off heat. It is also called “heat transfer” in engineering and “black-body radiation” in physics. Everything in the universe radiates heat. Some things radiate much MORE heat than others. If an object or process is above absolute zero, it’s giving off heat. Given that space itself can be only 2 or 3 degrees Kelvin (which is pretty darned cold!), calling it “heat radiation” seems odd, but it’s an actual physical process. Thermal radiation can be measured by very sensitive instruments — essentially high-tech thermometers. The specific wavelength of radiation will entirely depend on the exact temperature of the object. In most cases ,the emitted radiation isn’t something you can see (what we call “optical light”). For example, a very hot and energetic object might radiate very strongly in x-ray or ultraviolet, but perhaps not look so bright in visible (optical) light. An extremely energetic object might emit gamma rays, which we definitely can’t see, followed by visible or x-ray light. The most common example of heat transfer in the field of astronomy what stars do, particularly our Sun. They shine and give off prodigious amounts of heat. The surface temperature of our central star (roughly 6,000 degrees Celsius) is responsible for the production of the white “visible” light that reaches Earth. (The Sun appears yellow due to atmospheric effects.) Other objects also emit light and radiation, including solar system objects (mostly infrared), galaxies, the regions around black holes, and nebulae (interstellar clouds of gas and dust). Other common examples of thermal radiation in our everyday lives include the coils on a stove top when they are heated, the heated surface of an iron, the motor of a car, and even the infrared emission from the human body. As matter is heated, kinetic energy is imparted to the charged particles that make up the structure of that matter. The average kinetic energy of the particles is known as the thermal energy of the system. This imparted thermal energy will cause the particles to oscillate and accelerate, which creates electromagnetic radiation (which is sometimes referred to as light). In some fields, the term “heat transfer” is used when describing the production of electromagnetic energy (i.e. radiation/light) by the process of heating. But this is simply looking at the concept of thermal radiation from a slightly different perspective and the terms really interchangeable. Black body objects are those that exhibit the specific properties of perfectly absorbing every wavelength of electromagnetic radiation (meaning that they would not reflect light of any wavelength, hence the term black body) and they also will perfectly emit light when they are heated. The specific peak wavelength of light that is emitted is determined from Wien’s Law which states that the wavelength of light emitted is inversely proportional to the temperature of the object. In the specific cases of black body objects, the thermal radiation is the sole “source” of light from the object. Objects like our Sun, while not perfect blackbody emitters, do exhibit such characteristics. The hot plasma near the surface of the Sun generates the thermal radiation that eventually makes it to Earth as heat and light. In astronomy, black-body radiation helps astronomers understand an object’s internal processes, as well as its interaction with the local environment. One of the most interesting examples is that given off by the cosmic microwave background. This is a remnant glow from the energies expended during the Big Bang, which occurred some 13.7 billion years ago. It marks the point when the young universe had cooled enough for protons and electrons in the early “primordial soup” to combine to form neutral atoms of hydrogen. That radiation from that early material is visible to us as a “glow” in the microwave region of the spectrum.