Given the same surface area, will shiny things reflect light better than white things?
So for instance, if we cover Antarctica with really shiny foil, will it reflect more light back into space than it has been with white snow?
Those things don’t (necessarily) affect the amount of light being reflected, they affect its direction. A matte white surface has what’s called a diffuse reflection–that is, it reflects incident light away in all directions. A polished metal surface, on the other hand, has what’s termed a specular reflection–the angle of reflection is equal to the angle of incidence. In this type of surface, you can see an image reflected. However, it’s perfectly possible for the matte white surface to have a greater reflectivity than the polished metal one, depending on the exact composition and light wavelengths involved.
What about mirrors?
What about them?
Fresh snow has an albedo (diffuse) of 0.80–0.90.
A good aluminized surface will have a reflectivity (specular + diffuse) of near 95%.
Are there colored substances that can reflect light better than whatever they back mirrors with?
You’ve answered your own question here. A “colored substance” of a particular hue is reflecting only that spectrum of color and absorbing the rest. “Light” as you see is an amalgamation of a spectrum of discrete wavelengths of electromagnetic energy; each individual portion of the spectrum, however, is reflected by a different pigment.
Stranger
To direct this a bit more to the question, the fact that white surfaces reflect in every direction means that they are reflecting a lot of their light at an oblique angle through the atmosphere. That light has a higher chance of being absorbed in the atmosphere and never making it back to space.
So assuming that your surfaces are both oriented at right angles to the incident light the mirrored surface may be more efficient at reflecting light back into space even if its reflectivity is slightly lower.
I’d take issue with that phrasing. ‘Colored’ can mean more than one spectrum - a good example would be a rich purple, which incorporates red light and blue light, but not as much green light.
A colored substance does not reflect the different parts of the visible spectrum equally. But you’re right that that would generally give it a disadvantage in terms of total reflection versus uncolored substances.
Good point. Even better would be to reflect the light straight up, no matter what its incoming angle.
Do you know of a material which can do this? I sure don’t.
Am I missing something? Can’t any mirror be angled to reflect any incoming vertically?
Yes, it’s any material that can move. I suppose you’re interpreting it as meaning light simultaneously incident from multiple directions, rather than from the Sun, but I doubt that’s what Blake had in mind.
On further thought, when the mirrored surface isn’t normal to the incident light, it captures somewhat less light, so there’d be some optimal angle between reflecting up and reflecting normal to the incident light.