Tag: earth

Meteorological vs astronomical seasons
Meteorological vs astronomical seasons

In the field of meteorology the year is divided into 4 seasons following the climate: winter is made out from the coldest months of the year (Dicember, January and February); summer consists in the hottest months (June, July and August). The seasons in between these two are spring (March, April and May) and fall (September, October, November). These are the meteorological seasons.

So what’s the difference with the astronomical seasons?

Well, the year can also be divided following the movements of the Earth, the tilt of the Earth’s axis, and its position around the Sun. The Earth’s orbit is not a perfect circle, but seasons are not a consequence of how far or near the Earth is to the Sun. The distance has no effect on our weather or our seasons. So why do we have different seasons?
The solution lies behind the Earth’s axis. It’s is an imaginary pole going right through the center of Earth from “top” to “bottom.” Earth spins around this pole, making one complete turn each day. That is why we have day and night, and why every part of Earth’s surface gets some of each.
So, we have seasons on Earth because its axis doesn’t stand up straight.

Equinox and Solstice dipend on this: when the North Pole tilts toward the sun (around June) summer starts for the Northern Hemisphere; when the South Pole tilts toward the sun (around December) the winter starts for the Northern Hemisphere.

It is summer in June in the Northern Hemisphere because the sun’s rays hit that part of Earth more directly than at any other time of the year. It is winter in December in the Northern Hemisphere, because that is when it is the South Pole’s turn to be tilted toward the sun. Since this movement is not stable, the moment of Equinoxes and Solstices vary each year.
From the winter solstice the winter begins, spring starts from the spring equinox, summer starts from the summer solstice, autumn starts from the fall equinox.

In April the Arctic sea ice nearly set a new record
In April the Arctic sea ice nearly set a new record

Bad news form the North Pole. The Arctic sea ice extent was 980,000 square kilometers (378,400 square miles) below the average and only 20,000 square kilometers (7,700 square miles) above the record low April extent set in 2016. Sea ice in the Arctic expands and shrinks following the seasons: in summer the ice extent reaches its minimum, in winter its maximum size. During the month of April the ice starts to melt but usually not this much. Arctic sea ice extent for April 2018 averaged 13.71 million square kilometers (5.29 million square miles). Just to give an idea, the ice surface missing is 3 times the size of Italy! Only in April 2016 the situation was worse that today with 20.000 square kilometers more missing.

Ten interesting facts about Earth
Ten interesting facts about Earth

Earth is not a perfect sphere.

Earth is wider around the equator, the imaginary line around the middle. How much wider? Well, only 0.3%. Although Earth appears round in photos, it is just barely not.

Days are getting longer.

4.6 billion years ago when planet Earth was formed, days were much shorter, only about six hours long because it was spinning fast. Since then days have become longer and longer, about 0.0017 seconds longer every one hundred years. Why has Earth has slowed down? It’s all because of the Moon. The tides it creates all around the world slow down Earth’s rotation.

Continents don’t stay in one place.

Pangaea is the name of a supercontinent that grouped all the continents we see today about 250 million years ago. Since then they have spread apart to form the world as we see it today. North America, South America, Africa, Europe, Asia, Australia, and Antarctica are all separate entities now. But even before that time, over 800 million years ago there was another supercontinent called Rodinia.

One Ice Age? No, several.

Ice covered the Earth and woolly mammoths roamed during a recent Ice Age 300,000 years ago. But this wasn’t the only time ice completely covered the Earth. Scientists have discovered at least four other separate Ice Ages in the past .

How can the most arid desert be near the ocean?

The driest place on Earth, where there is a town people say that hasn’t seen a drop of rain for 400 years, is the Atacama Desert in northern Chile. It is funny that this desert is right next to the world’s largest body of water, the Pacific Ocean!

Gravity isn’t the same all over the Earth.

Earth has high mountains, deep valleys and other different features. If it were as smooth as a pool ball, gravity on Earth would be the same everywhere. GRACE is a special mission involving a satellite that maps out the gravity across the Earth’s surface showing  the differences in gravity.

Sea levels were higher (and lower) in the past.

Imagine if the seas were 390 feet lower than today, there would be lots more land and some islands would be attached to the mainland. This was the situation during the last Ice Age when so much water was trapped in icy glaciers. But long before that, the sea level was actually about 230 feet higher than it is now. There are parts of land today that used to be far beneath the ocean waters.

The sun has its own lifespan.

Like all stars, the sun goes through different phases, before it uses up all its energy. We don’t need to worry though, the sun won’t run out of energy for a long time, at least  five billion years! If people are still living on Earth they would have to leave and move to another planet, but there’s plenty of time to find one!

Earth has more than one “moon”.

The satellite that we call moon is not the only object orbiting near Earth. Two other asteroids that we cannot define strictly as moons are present near Earth. Cruithne  is an asteroid that follows the Earth around the Sun. The other, called Asteroid 2002 AA29 , has a horseshoe shaped orbit and passes near Earth every 95 years.

The calm before a storm.

When there is about to be a big storm  sometimes we sense a strange moment of absolute calm. The explanation is this. As a storm is building up the warm humid air around it is pulled inside, goes into the cloud  and comes out over the top. This air then comes back down on the outside of the cloud getting warmer and drier as it moves.  This makes the weather  calm and stable, which is the calm before the storm.