This March, Americans are of two minds regarding the change of seasons. There are those on the east coast and Midwest for whom this offers hope of the end of one of the most severe winters in history. Here in the Pacific Northwest, the longer days and higher temperatures confirm what we have long feared – that this will be a year with no winter at all.
But what exactly is it that’s causing these competing feelings of disappointment and optimism? What does science have to say on the subject?
Thanks for asking!
The answer lies in the intersection of biology and physics. Humans are generally diurnal; we tend to be active during daylight hours and asleep at night. Though we don’t hibernate (at least most of us don’t), our processes tend to slow down when the days become shorter, then pick up as day length increases. As the days (okay … the daylight portion of the 24-hour day) lengthen, we begin the transition from our wintertime to summertime selves.
It’s not so much the length of the days that causes this, but the day-over-day INCREASE in daylight hours that affects our moods. And there is not time when this is more pronounced than the first day of spring – the vernal equinox. This is where physics comes in.
You probably recall from high school science that the seasons are caused by the tilt of the Earth’s axis, relative to our orbit around the Sun. If you look at a chart of daytime versus nighttime throughout the year, the result becomes clear. The graph is a classic sinusoidal function – like a radio or sound wave. And one thing that’s fundamental to these functions is that, as the function reaches its neutral position (the spring and autumn equinoxes), the rate of change (the ‘first derivative’ in Calculus terms) hits is greatest.
But what exactly is it that’s causing these competing feelings of disappointment and optimism? What does science have to say on the subject?
Thanks for asking!
The answer lies in the intersection of biology and physics. Humans are generally diurnal; we tend to be active during daylight hours and asleep at night. Though we don’t hibernate (at least most of us don’t), our processes tend to slow down when the days become shorter, then pick up as day length increases. As the days (okay … the daylight portion of the 24-hour day) lengthen, we begin the transition from our wintertime to summertime selves.
It’s not so much the length of the days that causes this, but the day-over-day INCREASE in daylight hours that affects our moods. And there is not time when this is more pronounced than the first day of spring – the vernal equinox. This is where physics comes in.
You probably recall from high school science that the seasons are caused by the tilt of the Earth’s axis, relative to our orbit around the Sun. If you look at a chart of daytime versus nighttime throughout the year, the result becomes clear. The graph is a classic sinusoidal function – like a radio or sound wave. And one thing that’s fundamental to these functions is that, as the function reaches its neutral position (the spring and autumn equinoxes), the rate of change (the ‘first derivative’ in Calculus terms) hits is greatest.
This effect applies everywhere except at the equator, where day time and nighttime hardly vary throughout the year. At the other end, the Polar Regions go from nearly constant darkness in mid-winter to round-the-clock daylight in late June. Scientifically speaking, the further from the equator one is, the greater the amplitude of the sinusoidal function.
If that hasn’t adequately stolen the magic of the season from you, stay tuned.
Next time we’ll cover how it’s the wind ABOVE one’s wings that provides the lift; so if a friend says you’re ‘the wind beneath my wings’, you’re actually being told you’re a drag. Future lessons will cover how it’s generally darkest a really really long time before the dawn (around midnight).
If this all seems a little much, there is an alternate explanation. The Earth is coming to life in joyous celebration of Persephone’s annual release from captivity in the underworld.
You’re welcome!
If that hasn’t adequately stolen the magic of the season from you, stay tuned.
Next time we’ll cover how it’s the wind ABOVE one’s wings that provides the lift; so if a friend says you’re ‘the wind beneath my wings’, you’re actually being told you’re a drag. Future lessons will cover how it’s generally darkest a really really long time before the dawn (around midnight).
If this all seems a little much, there is an alternate explanation. The Earth is coming to life in joyous celebration of Persephone’s annual release from captivity in the underworld.
You’re welcome!
No comments:
Post a Comment