Tide Basics
The world’s incomprehensibly gigantic oceans are an ideal location to become intimately connected with the ruthlessly raw power of nature. Hikers and beachgoers alike love to look at the mysterious beauty of the world’s bodies of water from dry land. As surfers, we prefer to go in the water itself, and if we are lucky enough to score, we ride the energy of the waves and tides. But what exactly is a tide?
A tide is a wave. Yes, that’s right! The Earth’s tide is a wave of water with a wavelength of half the Earth’s circumference (~20,000km). This wave is caused by the effect of gravity from the moon and the sun. The moon pulls on the oceans closest to it. This lunar pull by itself would create only high tide and one low tide per day as the Earth rotates on its axis. The second high tide that surfers notice occurs because there is a centrifugal, or balancing, force acting on the oceans from the off-centered rotation of the Earth and Moon. These waves of water travel around the Earth with a period of 24 hours and 50 minutes or 89,400 seconds. This means that the high and low tide times change every single day.
The Sun’s Role
Our sun also influences the Earth’s tide because it has gravity as well. Farther away from the moon but 400 times as massive, the sun accounts for around one-third of the total pull of the tides. Furthermore, this pull from the sun’s gravity helps dictate the strength of the tides based on the moon phase. When the sun and moon are in alignment (new moon/full moon), there are bigger tides called spring tides. When the sun and moon offset each other (first quarter/third quarter), this creates smaller neap tides.
In later posts, we will cover more about tides, how they influence surfers, and other interesting ways humans connect with the oceans and their tides.
THIS IS SO COOL