Why is summer solstice designated ad the beginning of summer?


Summer solstice is the longest day/gets most direct sun light. Doesn’t that mean the warmest season is 1/8 year before and after it? So summer solstice should be the middle of summer instead, right? Or is there delay between sunlight hitting earth and earth getting warm?

In: Earth Science

On some planets in our solar system, the hottest day of the year is also the longest day of the year. This happens on Mars, for example. It makes intuitive sense – the longer the surface of the planet spends in the sun, the warmer it gets.

However, on the Earth, we have an awful lot of water on the surface of the planet, and it takes a lot of energy to heat water. So on Earth, the seasons lag behind the sun by several months. The gas giants also have seasonal lag for about the same reason that the Earth does.

Its an easily marked designator of time. The seasons are based on the earth’s position in its orbit, not just it being hot or cold.

What do you mean by “designated ad?”
Designated by whom?

The solstice is not designated, it is a measurement of the orbit of the Earth. The reason there is more warm weather after it than before it is that Earth has significant thermal inertia. All that water soaks up heat and slowly heats up. Then even when less heat is coming in it takes time to slowly cool off.

The solstices are opposite for the northern and summer hemisphere because of the angle of tilt the Earth rotates on.

So, it’s the beginning of summer because that’s the point in the earth’s orbit that that hemisphere will have accumulated the most thermal energy to carry forward throughout the next ¼ of the year. Bodies of water, the ground, the air, everything has been warming up all spring long as the days lengthened. That has a cumulative effect that gets carried forward. But the day after the solstice the days start to get shorter, so the amount of thermal energy won’t increase beyond that point.

Think of the earth and it’s seasons like an oven. Spring is preheating, summer is actually cooking something. Fall is letting it cool back down, winter is completely cool.

If the solstice and equinox days were the middle of season, they couldn’t tell when exactly the season begins. But these special days were great markers for seasonal change. It was convenient.

The same goes with the beginning of a new year on January 1st, of the 30 day long months with only February at 28 days. That for example, had been set by Romans who believed February is an unlucky month and therefore shortened it.


Rule 2.

Better to r/askhistorians about this.

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