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The cornea is a transparent structure found in the very front of the eye that helps to focus incoming light. Behind the cornea is a colored ring-shaped membrane called the iris. The iris has an adjustable circular opening called the pupil, which can expand or contract depending on the amount of light entering the eye. [The 7 Biggest Mysteries of the Human Body]

The birth of each rainbow begins with millions of tiny rain droplets.  The rain droplets serve as a type of reflector of light.  White light enters one individual rain droplet and exits as one specific color of the spectrum.  Without millions of rain droplets, a rainbow would not occur.  If you only had a few rain droplets you would only see a few colors.  This is typically why rainbow appear after a rain storm

Each rain droplet has a function in the formation of the rainbow. Sunlight enters the rain droplet at a specific angle and the rain droplet separates the white light into many different colors.  This angle is a fixed measurement between your eye

and the sun.  What color is refracted depends upon the critical angle,                   which is the angle the sunlight strikes the back of the rain droplet.  Red light bends the least, exiting the rain droplet at a 42 degree angle, while Violet light bends the most, exiting the rain droplet at a 40 degree angle.  All of the other colors of the rainbow exit the rain droplets at some angle between 40 and 42 degrees, thus making up the colors of the rainbow ROYGBIV, this order never changes.

As the light from our Sun shines into the atmosphere, most of the colors are able to reach the Earth’s surface uninterrupted. However, because blue light has a wavelength that is the same size as the particulates in the air, this light is scattered in every direction. This blue light bounces from particulate to particulate until it eventually reaches your eyes. For this reason, no matter what direction you look in the sky, it appears to be blue. This blue light originated with the Sun, was bounced around in the sky many times, and then eventually reached your eyes.

In space, there is no air. Because there is nothing for the light to bounce off, it just goes straight. None of the light gets scattered, and the "sky" looks dark and black.

Light rays pass through a dense, transparent gel-like substance, called the vitreous that fills the globe of the eyeball and helps the eye hold its spherical shape.

During a sunrise, the sun is lower in the sky, which lengthens the angle at which light reaches the Earth. As a result, the shorter violet, blue and green light never reaches the eye, so only the yellow, orange and red light is visible. Because red has the longest wavelength, the first light of dawn often appears pink or red--depending on the particles in the atmosphere. As the sun moves further up the sky, the reds and yellows fade as the scattered blue light becomes more visible.

it’s Daylight Saving Time! Daylight Saving Time (or “Summer Time,” as it’s known in many parts of the world) was created to make better use of the long sunlight hours of the summer. By “springing” clocks forward an hour in March, we move an hour of daylight from the morning to the evening. On the first Sunday in November, we “fall back” and rewind our clocks to return to Standard Time.

Your eye works in a similar way to a camera - light passes through the lens of your eye and is 'recorded' on the back of your eye (the retina).

Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time

Birds have many physical features, besides wings, that work together to enable them to fly. They need lightweight, streamlined, rigid structures for flight. The four forces of flight – weight, lift, drag and thrust – affect the flight of birds.

Flying birds have: lightweight, smooth feathers – this reduces the forces of weight and drag a beak, instead of heavy, bony jaws and teeth – this reduces the force of weight an enlarged breastbone called a sternum for flight muscle attachment – this helps with the force of thrust light bones – a bird’s bones are basically hollow with air sacs and thin, tiny cross pieces to make bones stronger – this reduces the force of weight a rigid skeleton to provide firm attachments for powerful flight muscles – this helps with the force of thrust a streamlined body – this helps reduce the force of drag wings – these enable the force of lift.

Color originates in light. Sunlight, as we perceive it, is colorless. In reality, a rainbow is testimony to the fact that all the colors of the spectrum are present in white light. As illustrated in the diagram below, light goes from the source (the sun) to the object (the apple), and finally to the detector (the eye and brain).  

For starters, cats’ visual fields are broader than ours, spanning roughly 200 degrees instead of 180 degrees, and their visual acuity isn’t as good. So, the things humans can sharply resolve at distances of 100-200 feet look blurry to cats, which can see these objects at distances of up to 20 feet. That might not sound so great, but there’s a trade-off: Because of the various photoreceptors parked in cats’ retinas, they kick our asses at seeing in dim light. Instead of the color-resolving, detail-loving cone cells that populate the center of human retinas, cats (and dogs) have many more rod cells, which excel in dim light and are responsible for night-vision capability. The rod cells also refresh more quickly, which lets cats pick up very rapid movements — like, for example, the quickly shifting path a marauding laser dot might trace. Lastly, cats see colors differently than we do, which is why the cat-versions of these images look less vibrant than the people-versions. Scientists used to think cats were dichromats — able to only see two colors — but they’re not, exactly. While feline photoreceptors are most sensitive to wavelengths in the blue-violet and greenish-yellow ranges, it appears they might be able to see a little bit of green as well. In other words, cats are mostly red-green color blind, as are many of us, with a little bit of green creeping in.

As an example, think of a person who has a cold. That person may cough into his or her hand and then touch a doorknob, thus placing the cold virus on that doorknob. The virus may die on the doorknob, but it's also possible that the next person to touch the doorknob will pick it up. If that person then touches food with the unwashed hand and consumes the food, the virus is now inside the body.

As the Earth rotates it turns away from the sun’s light, and the sky becomes dark. However, if you think about the millions and millions of bright stars all around the sky at night, you might start to wonder why it isn’t just as bright as it was when we were facing the sun!

Cats and dogs are just like color blind humans, seeing some colors but not all of them. For the bright daytime light, cells known as cones are needed. Humans have three kinds of cones, enabling them to see blue, red and green.

Cats and dogs, on the other hand, have just two kinds of cone cells (blue and green sensitive), allowing them to see only partial color.

while we’re on the subject, contrary to the legend that cats can see perfectly in total darkness, they do not have those superpowers. But cats require only about one-sixth of the light that humans do, making their night vision a whole lot better than ours

The wavelength of the blue light scatters better than the rest, predominates over the other colors in the light spectrum, and makes the sky appear blue to us.

We experience some deep, quiet sleep and some active sleep, which is when dreams happen. You might think sleepwalking would happen during active sleep, but a person isn't physically active during active sleep. Sleepwalking usually happens in the first few hours of sleep in the stage called slow-wave or deep sleep.

Sleepwalking may run in families and sometimes occurs when a person is sick, has a fever, is not getting enough sleep, or is stressed.