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Do you consider yourself an early bird or a night owl? Most people tend to fall into one of those categories, but it doesn’t mean they can’t be either type from time to time. Early birds love waking up early and seeing the morning dew on the plants. Night owls prefer to stay up late and enjoy the night sky. Regardless of our preferences we all respond to light and dark similarly.

A circadian rhythm is a biological function that responds to light or dark. We find this natural process in all living things. It is one factor that is responsible for your sleep cycle. It is why you feel drowsy at night and awake during the day.

The scientific community defines night as the time between sunset and sunrise, and day as the time between sunrise and sunset. There is no determined duration for day or night as the sun rises and sets at different times throughout the year.

As the Earth rotates on its axis different areas of the world experience day or night. It takes 24 hours for Earth to complete one full rotation. The Earth's axial tilt is not perpendicular to the Sun's orbital plane. If it was perpendicular then night and day would each be 12 hours long, and there would be no seasonal variations. Due to the tilt of the Earth's axis we experience different lengths of day and night.

The planets in our solar system all have different tilts to their axes. Uranus is tilted at almost a right angle of 97.77 degrees. This means Uranus essentially orbits on its side. Astronomers think the planet collided with something equally large a long time ago, causing the dramatic tilt. Day lengths differ across the planets in our solar system and places on Earth.

In the northern part of Canada, as well as in some other Northern Hemisphere countries, the sun doesn't rise or set at all during certain periods of the year. For example in Tromsø, Norway, the Polar Night lasts from November to January. During this period the sun never rises. The Midnight Sun occurs from May to July, and during this period the sun never sets. Tromsø experiences both perpetual nights and perpetual days every year.

Imagine only seeing the sun or the moon for such extended periods of time. There is no dusk, no dawn, and no twilight; only day or night.

In most countries these extremes of perpetual night or day don't occur although days get longer and shorter depending on the season. Summers are filled with relatively long days and short nights whereas winters have short days and long nights. The summer solstice is the longest day of the year and the winter solstice is the shortest day of the year.

The night sky is full of wonderful sights, as long as you live in an area with little or no light pollution. You might be able to see faint traces of stars if you live in a bustling urban area but the further away you get from man-made illumination, the better your chances are of seeing some marvellous sights in the night sky, like stars and constellations. You can look at the constellations and try to find your zodiac sign in the sky.

In a scientific sense, a star is a ball of hydrogen and helium with enough mass that it can sustain nuclear fusion at its core. Stars come in different sizes and colours, and our Sun is average compared to other stars. Betelgeuse is a red giant star that is 700 times larger than our Sun and about 14,000 times brighter. There are billions of stars like our Sun scattered across the Milky Way galaxy.

A star is born when a nebula, called molecular clouds, gravitationally collapses and forms a star from the gases in the cloud. Some stars in the sky you see are long gone as light travels extremely fast taking many years to reach Earth. Some of the stars that have already long died have light that is still travelling to us on Earth. That is quite incredible.

Can you see the stars clearly where you live?

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