“Look at the stars! Look, look up at the skies!
O look at all the fire-folk sitting in the air!
The bright boroughs, the circle-citadels there!”
The Starlight Night - Gerard Manley Hopkins (1844-1889)
These are the opening lines of a beautiful poem by English poet Gerard Manley Hopkins, “The Starlight Night”, and while reading it one can almost see children on holiday who, after playing together with friends on the terrace at home, on a trip to the mountains, at the seaside or perhaps even in their dreams, point to the bright dots scattered across the skies and daydream about distant worlds, about those “little towns that spin” above our heads, and that fuel our imaginations like few other things in this world.
The sky is an open book where we can read endless stories of legends and magic, experiments and science. It holds so many secrets!
On a night-time stroll we can spot Vega! It is impossible to miss it! Vega is one of the easiest stars to spot in the summer sky, as it is the brightest star in the constellation of Lyra.
Here is another fun fact to tell children: Vega is destined to become the North Star… and this has to do with the summer solstice!
Stories involving space are the most mysterious of all: not only do we not know how they end, but we do not even know how they begin!
So, let's try to find out together what happens to our planet in summer.
How did Earth form?
“All of a sudden I sprawled; as if they had - we would say today - tripped me up.
It was the first time I had fallen, I didn’t know what “to fall” was.
“Don’t trample here”, a voice said, “I don’t want you to, Qfwfq”. It was the voice of my sister G’d(w)n.
- Why? What's there?
- I made some things with things…”
At Daybreak, Cosmicomics - Italo Calvino
The bizarre protagonist of the fantastic stories by Italian writer Italo Calvino, who goes by the unpronounceable name Qfwfq, recounts the first moments of the creation of the solar system: from a vast cosmic void to the ability to fall from a surface that previously had not existed. Indeed, in the beginning there was nothing to walk on in the solar system… so what was there? Scientists are not entirely sure, but probably a great cloud of gas, perhaps heated by the explosion of a nearby star, set in motion the material that was inside it. Over the course of billions of years, this material collided with other material, sticking together, breaking apart and re-forming, heating up and cooling down until it produced the planets as we know them today. There was real chaos in the beginning! These violent collisions were fundamental for human life since Earth, as a result of these clashes and the gravitational pull of the Moon and Sun, is tilted on its axis as it moves through space.
What is the summer solstice?
Earth rotates as it revolves around the Sun, but its axis of rotation is tilted. It bears a greater resemblance to a spinning top spinning than to a basket ball rotating!
Spinning just like a spinning top, this tilted axis which to the north points almost directly to the North Star, means that one day (thousands of years from now) the North Star it points to will be none other than Vega!
This axial tilt is what causes the seasons: how hot or cold it is does not depend only on Earth's distance from the Sun, but also on the angle at which the sun's rays strike our planet.
Let's think about what happens on the summer solstice (literally, sun standing still): the side of the planet tilted towards the sun (in this case the southern hemisphere) receives sunlight for longer than the dark side, with the days growing longer until the maximum period of sunlight which is the summer solstice (this year it falls on 21st June). Looking at the picture, you can clearly see how the South Pole remains in shadow, while the North Pole has continuous sunlight, so that it is light even at midnight!
As it continues its orbit around the Sun, Earth reaches a point where its angle of inclination relative to the Sun is perpendicular to its axis and the two hemispheres have a day and night of equal duration (equinox, equal night).
Here is an experiment to carry out with children to help them understand this phenomenon.
We need a globe, or else we can make one using a large polystyrene ball to draw on and colour in, keeping our creation in place with a wooden stick (like those used in the kitchen to make skewers).
At this point, on top of the globe we can place some action figures or characters created by the children, and then try to light them up with a desk lamp or the torch on a smartphone.
And now watch carefully! Where do the shadows of the characters fall as the children spin the globe? When we tilt the globe, do the two poles receive the same amount of light?
Test away, have fun experimenting and enjoy this game to play with the whole family!