Tag: Earth

Categories
Stargazing Universe

Earthshine

Earthshine
Earthshine

When you look at the Moon, sometimes, besides the illumination of the crescent of the moon, you are able to see the rest of the disk of our planet’s natural satellite. That dim illumination of the darker disk is called earthshine.

What causes it?

But what causes this illumination? We all know that sunlight hits Earth, there’s no question there. But Earth is a globe, and a fraction of the light that hits our planet, is reflected back into space (and in the scientific literature is known as earthlight). Some of this light that gets reflected into space, hits the moon as well, and it is this what causes the lighting up of the dark disk besides the crescent moon. And this dim light gets reflected back to Earth and it’s what our eyes percieve.

Sunlight hits Earth (yellow arrow). A portion of this light gets reflected back into space (white arrow) and can cause earthshine, which is reflected back to Earth (grey arrow).

When to look?

When the moon is full, we’ve all seen that it can light up pretty well entire regions on our planet, from where the full moon is visible. From the surface of the moon, Earth can be also illuminated by the Sun (just like other planets of our Solar System). When Earth is “full” (from the moon’s night sky perspective), it means that our planet can light up an entire region on the moon as well. Why would it only be the other way around, anyway? This also means that earthshine is visible at its maximum when Earth is almost “full”, so, when the Moon is a very thin crescent.

Planetshine

This phenomenon occurs on other celestial bodies as well, not only on Earth! When a planet is illuminated by its star, and if that planet has a natural satellite, the phenomenon takes plase in the same waym just like in the Sun-Earth-Moon system. The only difference is the name – it’s generally called planetshine. And, of course, light reflected from a planet in general, is called planetlight.

Have you already seen or photographed earthshine?

Categories
Nature Science Universe

The Polar Day

The Midnight Sun shines 24/24h during the polar day
The Midnight Sun shines 24/24h during the polar day

Regions way above the Polar Circle, in the High Arctic, have already started to experience the polar day. Other Arctic regions are going to experience the phenomenon in the coming days. In Vadsø, the polar day already started on May 17 this year, and the Midnight Sun has been visible since, as well.

But what is the polar day?

Earth carries out two types of rotations: one around the Sun, during the course of a year, and the second around its own axis, during 24 hours. At the same time, Earth is inclined in respect with the Sun, at an angle of approximately 23°, and remains tilted at this angle during the whole year.

This means that the Earth is illuminated by the Sun differently during one year. At and around the summer solstice (sometime around 22nd June each year), Earth is inclined in such a way that the North Pole and the region around the North Pole, points towards the Sun, thus it is illuminated more and longer.

Just take a look at the first part of this video from the California Academy of Sciences, and see how Earth is illuminated by the Sun during a whole year.

You can see that the length of the polar day varies in function of latitude: closer you are to the North Pole, longer the polar day is. At the exact location of the North Pole, the polar day lasts no less than 6 months! At lower latitudes, but still above the Arctic Circle, the Sun never sets for a shorter period. The shortest polar day occurs on regions exactly on the Polar Circle (at 66°N), where the Sun never sets for only 1 day, which is exactly the day of the Summer Solstice!

The Midnight Sun

The Midnight Sun is a wonderphul phenomenon. It is what makes the sky bright at “night time” during the polar day, just like the Northern Lights brighten the sky during the dark period. It is a typical Arctic (and Antarctic) phenomenon, which occurs only during the polar day.

As the name suggests, here in the Arctic, the sun is visible in the sky at midnight, as well as the whole night and day, and it never sets below the horizon during this period. In Vadsø, the Midnight Sun will be visible this year until July 26.

And did you know that Aurora Labs has a special activity dedicated to discovering the midnight sun differently? Check it out here!

Regions below the polar circle experience a normal day/night cycle, which varies also in length, in function of the exact latitude.

And, by the way, the opposite of the polar day is the magnificent polar night! Have you ever experienced one or the other?

During the polar day, the Sun never sets below the horizon.
Categories
Nature Science Universe

The Polar Night

Polar Blue during the Polar Night in Vadsø
Polar Blue during the Polar Night in Vadsø

This period of the year means the beginning of the end of the Polar Night for regions in the Arctic. The polar night in Vadsø will end on the 17 of January, when the Sun will rise for the first time this year in the Arctic sky, for only 50 minutes. After this date, each day will mean the Sun will come out higher and higher in the sky and for longer periods. And this until May 17, when the Sun will never set for almost 2 months, marking the beginning of the Polar Day.

But what is the polar night?

Earth carries out two types of rotations: one around the Sun, during the course of a year, and the second around its own axis, during 24 hours. At the same time, Earth is inclined in respect with the Sun, at an angle of approximately 23°, and remains tilted at this angle during the whole year.

This means that the Earth is illuminated by the Sun differently during one year. At and around the winter solstice (sometime around 22nd December each year), Earth is inclined in such a way that the North Pole and the region around the North Pole, points away from the Sun, meaning it is not illuminated by our star, which translates into a continuous night – phenomenon which we call the Polar Night.

Just take a look at the first part of this video from the California Academy of Sciences, and see how Earth is illuminated by the Sun during a whole year.

You can see that the length of the polar night varies in function of latitude: closer you are to the North Pole, longer the polar night is. At the exact location of the North Pole, the polar night lasts no less than 6 months! At lower latitudes, but still above the Arctic Circle, the Sun never rises for shorter periods. The shortest polar night occurs on regions exactly on the Polar Circle (at 66°N), where the Sun never rises for only 1 day, which is exactly the day of the Winter Solstice!

Moreover, in function of latitude, the Polar Night may be experienced differently, concerning the position of the Sun below the horizon. This means that during the polar night, closer to the Arctic Circle, the Sun will still be near the horizon (but still below it) during the normal “day” hours. Which means that twilight occurs – thus indirect light from the Sun beautifully illuminates these regions, and you are able to see the landscape and the surroundings. And it does it in a surreal blue lighting – which is what the amazing polar blue is! Vadsø in Northern Norway experiences this phenomenon during the whole period of the polar night.

Me during the Blue Hour outside of Vadsø, during the polar night
Dogsledding in the Varangerhalvøya National Park, during the Polar Night

Further up from the Arctic Circle, the Sun does not have time to get so close to the horizon, which means that no indirect light will illuminate these regions at all, which leads to a 24-hour long pitch-black night, which can last for months!

And the best part about the Polar Night? You can see the Northern Lights even during the “daytime”!

Regions below the Polar Circle experience a normal day/night cycle, which varies also in length, in function of the exact latitude.