Folks driving home as the sun is setting may notice the rays of the sun make it hard to see, even giving way to what many refer to as sun blindness.
Alison Earnhart, instructor of physics at Juniata College explained that the position of the sun in the sky is responsible for the sun in motorists’ eyes this time of year.
“The main reason the sun causes more blindness is that it’s physically lower in the sky this time of year. Generally speaking, the sun’s path across the sky is higher and longer in the summer and lower and shorter in the winter. This is caused by the tilt of the Earth,” said Earnhart. “People notice it especially when they’re driving home in the winter time because the sun is setting earlier in the evening. So when most people are leaving right around 5-6 p.m., they’ll notice it more.”
According to Earnhart, the only difference between summer sunsets and winter sunsets is time.
“When the sun is lower in the sky, there’s more of a chance that you’re going to have the sun’s rays shining into your eyeballs as you look out across the horizon like when you’re driving. Also, and more practically, since the sun is setting earlier in the winter months, it tends to be setting around the time that folks are driving home from work, so it’s simply more noticeable then. In the summer when the sun sets much later, it’s not as big of a problem. Additionally, the reflection off of snow and ice means that there’s more of a chance to get blinded simply from all the shiny things around,” said Earnhart.
“In the summer time when the sun is setting at like 8:30-9 p.m., there are far fewer cars on the road and rush hour’s done. It’s simply not as noticed. In winter when you have ice and snow everywhere you have a lot more reflective surfaces that the sunlight can reflect off of and hit your eyes at a strange angle especially while you’re driving,” said Earnhart.
Earnhart explained the position of the sun in the sky is due to the changing of seasons.
“The Earth’s axis is tilted 23.5 degrees, and as we go around the sun every year, we spend a quarter of the time with our Northern Hemisphere tilted towards the sun and a quarter of the time tilted away from the sun. In between is autumn and spring,” said Earnhart. “This tilt causes its position in our sky to change and hence, more direct sunlight in the summer. It’s also why when we’re having winter, the southern hemisphere is having summer and vice versa.”
Even though it is winter for people living in the northern hemisphere, Earnhart explained the earth remained tilted the same way.
“The Earth is always tilted the same amount, but because we’re going around the sun throughout the year, the area of the Earth that is pointed towards the sun or away from the sun changes. For our winter the Northern Hemisphere is tilted away from the sun, when it’s winter here, it’s summer in the Southern Hemisphere. That’s why we view it as being lower in our sky, because we’re physically pointed away so the sun ends up being lower,” said Earnhart. “For us, since we’re still in winter right now, that means the Northern Hemisphere is tilted away from the sun still. If you imagine leaning away from something, whatever you’re leaning away from gets lower and lower in your field of vision. So that’s true for the sun right now.”
A hot topic for most who buy sunglasses is the amount of harmful rays coming from the sun. Earnhart explained that the amount of UV light isn’t much different in the winter as opposed to the summer.
“There are a lot of factors that play into the amount of ultraviolet (UV) light you’re getting at any given moment. The seasons aren’t really that big of a deal, but weather has a big factor in it. Thicker cloud coverage can play a small role, but even when it’s cloudy, UV light can make it through the atmosphere,” said Earnhart. “One of the biggest things is thickness of the atmosphere. If you’re at a high altitude, you’re going to experience more UV light, and down here you experience less. Throughout the seasons, I don’t think there is actually much of a change in the amount of UV light on any given day.”