What is Albedo?
Albedo is a term used to refer to the amount of light that an object reflects. The term is typically used in science, especially in astronomy, as well as in photography and computer generated imagery (CGI), where understanding of reflective surfaces often plays an important role in making materials look realistic. There is no specific unit used in measuring an object’s albedo, and the scale used is typically either between 0 and 1, where 0 is a non-reflective “black body” surface and 1 represents total reflection of light or a “white body.” It is also measured as a percentage with a maximum limit of 100%.
Originally a Latin word, albedo means “whiteness” and is rarely used outside of scientific and specialized fields of artistic creation. In astronomy, it is often used in the study of distant objects, either within our own solar system or far beyond our immediate neighbors, such as planetary bodies orbiting distant stars. For understanding such distant objects, knowing how light reacts to different types of materials can make it easier to understand what is seen and measured about those objects.
For example, freshly fallen snow has an albedo rating of about 0.9, ice is 0.5, and expanses of sand are about 0.4. If an astronomer is able to accurately gauge a distant planet as having an albedo generally of about 0.4 then he or she can begin to narrow down the properties of that world. While it may not be immediately possible to determine if it is made up principally of deserts, there is at least some quantifiable evidence to support such a claim. This is, of course, made more difficult in that many planets do not consist of a single type of environment, and clouds and other atmospheric factors often affect the albedo of a planet. However, it can provide useful information.
Albedo is sometimes used in photography and CGI as well, though for somewhat different purposes. When photographing a surface, it can be helpful for a photographer to understand how light will be affected by the surface, so unsightly lens flares and other photographic anomalies can be avoided. For computer artists, it can be extremely important to understand the albedo of a type of material to better ensure the computer version of that material matches reality. Reflectivity of surfaces plays a large role in how people observe different objects and immediately recognize whether something is made from metal, wood, or plastic. Understanding how these different appearances require different textures and levels of reflectivity, makes for more realistic and accurate digital creations.
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![Camera lenses that have several glass elements tend to create lens flare -- often seen as scattered light circles or halos.]()
By: adam121Camera lenses that have several glass elements tend to create lens flare -- often seen as scattered light circles or halos.
Discussion Comments
@irontoenail - I know what you mean. I lived in Alaska for several years after I graduated college. What a lot of people don't consider is just how much the snow can affect your skin.
Part of the problem is the combination between the cold of the air combined with the light reflected from the snow. It can cause horrible chapping and burning if you don't cover up enough. The other thing that has happened to me and plenty of other people I knew was that the sun reflects off the snow and hits the inside of your nose. What you end up with is a sunburn in your nose, and it is not a fun experience.
Wow, this was really interesting. I had read the term albedo in books and knew generally what it was, but I didn't realize it had some many varied uses. I thought the really interesting thing was when the article mentioned that people could tell the difference between different materials just by the amount of light they reflected. Once I thought about it, though, I realized that it really is true.
If you had a white piece of plastic, wood, paper, and metal, you probably wouldn't have a difficult time telling the materials apart just based on the amount of reflection coming off of them.
I never thought about looking into space, either. Then you definitely wouldn't have the ability to tell what material something has just by touch. Out of curiosity, what is Mars' albedo or another planet's compared to Earth?
@TreeMan - That is pretty interesting. Is that to say though that we should cut down all the trees in those areas? Just because they retain some of the heat, they would still be doing their job of pulling in carbon dioxide from the atmosphere. I am curious if there are any studies looking at the tradeoffs between the two things.
Global warming has been where I've heard talk about albedo lately. I wonder if the opposite thing would hold true that there are places in the world where there are land covers that have very low albedo, and it might be worth it to try to find more reflective vegetation.
I wonder how much the oceans' refectiveness would play into sunlight being bounced away from the surface.
@pleonasm - Good point. I was also reading that there is actually a strong link between land cover types and climate change. A lot of people advocate for reforesting everywhere where it is feasible so that the trees will suck up more carbon. Removing carbon from the atmosphere, then, should theoretically help the Earth to cool down.
In reality, though, trees can actually cause the land to heat up faster than it normally would. The primary example that the article I read used was in the boreal forests in Canada and Russia. Basically, the land is covered by snow for the majority of the year, and that snow is able to reflect huge amounts of sunlight that would normally heat up the ground. If you start planting trees there, though, the trees are darker and would retain some of the heat from the sun.
I thought it was a reall interesting concept and just another challenge in dealing with climate change.
People underestimate how much the albedo affects them, particularly when it comes to their skin and eyes.
The classic situation is the tourists who think they are safe from the sun because they are sitting in the shade. But, the harmful rays get reflected from the ocean, or from the sand, or even from the snow and they can end up harming you almost as much as direct rays.
Worse, usually, because since people think they are safe they don't take any kind of precautions. So they end up sitting for hours exposed to the part of sunlight which is most dangerous, and they end up with sunburn and sore eyes.
Which is why you should always protect yourself with sunglasses and sunscreen and think about not going outside at all during the hottest part of the day.
Albedo is a really important term when you are considering the feedback loops that are contributing to climate change. When I had to research this for school it was actually really disturbing what I found out.
The problem is that most people think of the ice melting in the ocean as a simple process, as in the world gets hotter, the ice melts and that's about it.
What actually happens is that the ice melts and exposes the water which has a much higher albedo than ice. Which means that the reflected light is hotter and leads to more ice melting.
So, it's not just a matter of increasing temperatures, it's also a matter of the increasing albedo. Which makes it that much more difficult to change if we fix the carbon.
At the moment, since so much ice is gone already, it would take lower temperatures to replace it than we had before.
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