Put a pencil straight down into a glass of water. Notice whether the pencil looks bent. Now tilt the pencil and note how its apparent bending changes. How does this illustrate why light from objects near the horizon is refracted more strongly?
Is the atmosphere thicker looking toward the horizon than upwards?
Yes, the atmosphere does appear to be thicker when looking toward the horizon compared to looking upward. This is due to the phenomenon known as atmospheric refraction.
To understand why light from objects near the horizon is refracted more strongly, let's begin with the example of placing a pencil in a glass of water. When you place a pencil straight down into the water, it appears to bend at the water-air interface. This bending of the pencil occurs because light traveling from the pencil into the air undergoes refraction.
Refraction is the bending of light as it passes from one medium to another with a different optical density, such as from water to air or from air to glass. The speed of light changes as it moves through different substances, and this change in speed results in refraction.
When light waves pass from one medium (like air) to another medium (like water or glass) at an angle, they change direction. This bending occurs because light travels at different speeds in different media. The change in direction depends on the change in the speed of light as it transitions from one medium to another.
Now, let's apply this understanding to the case of light passing through the Earth's atmosphere. The Earth's atmosphere consists of layers of air with varying densities. As light passes through these layers, it encounters variations in temperature, pressure, and humidity, which causes its speed to change. This change in speed leads to the bending or refraction of light rays.
When an object is near the horizon, the light from that object has to travel through a larger portion of Earth's atmosphere compared to when the object is directly overhead. This means that the light rays near the horizon have to pass through more layers of varying air densities, resulting in a greater degree of refraction.
So, the apparent stronger refraction of light from objects near the horizon is due to the longer path through the atmosphere, passing through more layers with different densities. This bending of light by the Earth's atmosphere causes objects near the horizon to appear higher than they actually are, leading to phenomena like the apparent compression of the Sun or Moon when they are near the horizon.
In summary, the apparent stronger refraction of light from objects near the horizon is a result of the longer path through the Earth's atmosphere, which contains layers of air with varying densities. This bending of light is similar to the way a pencil appears to bend when placed in water, and it is due to the phenomenon of atmospheric refraction.