1. We get seasons because Earth is tilted 23.4º on its axis.
When the North Pole is pointed towards the sun it’s summer in the Northern Hemisphere. Summer solstice is the time at which the North Pole is closest to the sun.
2. The summer solstice doesn’t happen very often on Uranus.
We get the summer solstice once a year. But in Uranus’ northern hemisphere it last happened in 1944, and will next happen in 2028.
3. Photosynthesis probably uses quantum effects.
Photosynthesis turns sunlight into energy for plants. We don’t quite know how it works, but it seems to involve quantum effects including entanglement, which inextricably links particles no matter where they actually are.
4. Migrating birds might “see” Earth’s magnetic field using quantum entanglement.
Birds appear navigate using Earth’s magnetic field, which they might see as a pattern of colours thanks to quantum entanglement.
5. Campfire flames are visible thanks to decaying electrons.
The flames of a campfire are the visible light emitted by electrons decaying to lower energy levels.
6. Inertia keeps you in your roller coaster seat.
You don’t fall out of a roller coaster during a loop because your inertia resists the acceleration and anchors you to the seat.
7. Sunsets are red because red light is scattered less by Earth’s atmosphere.
Blue, violet and green light have shorter wavelengths than red and so are scattered more when they pass through Earth’s atmosphere, leaving just reddish light.
8. You can thank the wavelength of blue light for perfect blue skies too.
During the day, sunlight passes through less atmosphere as it comes from directly overhead. Blue light is still scattered but not scattered away completely, so the sky looks blue.
9. Hayfever is caused by three different types of pollen.
Tree pollen, grass pollen, and weed pollen can all trigger the sneezing and itchy eyes that seem to go hand in hand with summer for many people. Tree pollen is mostly released in spring, but grass and weed pollen start in spring and go through summer. And spending more time outside in summer means its harder to avoid pollen.
10. Sunflowers use maths to maximise sunlight.
The spiral shapes of sunflowers follow a Fibonacci sequence: 1, 1, 2, 3, 5, 8… each number is the sum of the last two. This maximises the sunlight received by each floret.
11. Getting sunburn can damage the DNA in your skin cells.
And damage to DNA can kill the skin cells – this is one of the reasons your skin peels after getting badly sunburnt. The body can repair DNA after its damaged, but it can’t always be fixed. The mutated DNA is what can lead to skin cancer.
12. A bellyflop has exactly the same amount of kinetic energy as a proper dive.
But that energy is converted to sound, heat and waves when the diver hits the water, rather than gradually worn away by friction.
13. Cicadas expand and contract their exoskeleton to make loud calls.
They do this thousands of times per second. Navy physicists have studied them to create long-range underwater beacons.
14. Sandcastles are held together by water surface tension.
Billions of grains of sand are held together in a sandcastle by tiny “bridges” of water surface tension. Add too much or too little water and the bridges snap, causing your castle to crumble.
Thanks to the Perimeter Institute’s #PhysicsOfSummer series for some of these facts.
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