When Does It Get Dark?

Wherever you are in the world, most people will smile at the thought of lighter nights during the summer. It brings forth memories of sunny bbqs, drinks in the garden, shorts and dresses. Astronomers and keen star gazers however, live for the longer nights. An extended period of time in which you could hope to coo at the moon or try to find Neptune’s elusive shine. Or you could just be one of those crazy people, like me, who love a good cosy night in watching the TV. No matter who you are, the question of ‘When Does It Get Dark?’ has probably passed through your mind at some point. Well, here I am to tell you a bit about the time when the Sun goes away and the stars come out to play.

Billions of Stars?

While gazing at the night sky and seeing all those wonderful blinking lights, I have often wondered why we don’t see more. There are billions upon billions of stars out there in the universe, shouldn’t the black sky be covered in tiny glints? The truth is easy to understand: the universe is always expanding. Stars that were created millions of years ago are getting further away from us as time goes on. Therefore they get fainter and dimmer, which is the reason our dark nights aren’t as bright as you would think.​ However, there are some wicked spots when it comes to finding the best night sky views.

What’s the Time?

The answer to this question lies in where you call home. The answer is different across the globe. Do you ever sit at home eating dinner at six in the dark and wonder what the Australians are doing? Well, if you live in England, the Australians would most likely be still be fast asleep with the sun getting ready to rise. The globe is split into time zones which affects what time the country is in, dependent on where the earth is on its 24 hour rotation. The following image highlights the different timezones.​

World Timezones

So for instance, if it was noon in the UK, it will be 7am in New York City. The various time zones need to be kept in mind when discussing the time it gets dark, as each time zone will experience it at different times.

Why does it get dark?

The very simple answer being, we have night and darkness when the Earth rotates on its axis and turns away from the Sun. Each hemisphere takes its turn in the light, the amount of hours depends on where Earth is in its rotation of the Sun. Earth is on a slight tilt, which means during the summer months in the northern hemisphere, the Earth’s axis points towards the Sun, the opposite for the southern hemisphere. The following is a great picture highlighting this:​

Seasons

You Spin Me Right Round

Following along with the Earth spinning away; it’s rotation take 24 Earth hours to orbit the Sun. In a symmetrical world we would all have 12 hours day and 12 hours night, but that’s not how this works. Due to the tilt and the Earth’s axis, the amount of darkness we get depends on where you live. For ease and simplicity I will only discuss times for the Northern hemisphere.

The equinox is when the plane of Earth’s equator passes through the centre of the Sun. This happens twice each year, in March and September. Day and night are roughly equal at these times but not exactly 12 hours each. Then we have the solstice in June and December where the sun is either at its highest or lowest point in the sky at noon. Once again check this image to understand where the Earth is in its rotation at the equinox and solstice to better understand when it gets dark:

Spin Right Round

Equinox

The spring equinox marks the first day of the astronomical spring and is often when people associate the nights getting lighter. Turning the clocks forward one hour towards the end of March means that it will get darker later on in the evening. Apart from attempting to confuse millions of people, daylight saving time was originally created to take advantage of the longer daylight hours during the summer. Sunset times gradually increase over the following months, meaning stargazers will have to wait awhile before getting out. The September equinox often marks the end of summer and beginning of autumn, it is often when most people notice the dark nights getting earlier.

Solstice

The solstice arrives twice a year, June and December.

  • Difficult language: when the sun reaches its most northerly or southerly point relative to the celestial equator.
  • Simple language: In June the Sun is high in the sky at noon. In December the Sun is low in the sky at noon.

We love the June solstice in our family as it’s the day with the most sunlight hours, meaning it won’t get dark until late in the evening. The December solstice is the day with the shortest hours of sunlight. Astronomers better get their telescopes out as this is the best time to head out and get a full night’s worth of star gazing.

So When Does It Get Dark?

I’m hoping I made this article as simple as possible to answer the question ‘When Does It Get Dark?’. The truth is though, there is no simple answer. It changes according to where you are in the world and where the Earth is in its rotation of the Sun. There are hundreds of articles and journals out there which go into much more detail of the Earth’s axis, the celestial sphere and other complicated scientific terms. For more information I have included some links to websites which I find relatively easy to read and give further information on some of the topics I have discussed.

Useful links:

A great website to figure out your local sunset times: 

https://www.timeanddate.com/sun/

Information about the equinox and solstice:

http://www.metoffice.gov.uk/learning/learn-about-the-weather/how-weather-works/seasons/the-equinox-and-solstice

Information about Earth’s orbit around the Sun:

http://www.universetoday.com/61202/earths-orbit-around-the-sun/

Image Credits: 

Featured Image Source:​ Bryan Pocius / CC BY 2.0

https://www.flickr.com/photos/estevesm/473866656/in/photolist-k2gm55-bkwof3-HSG3L-5CVQHK-xTGAn-a7aod-bnZX5v-reYAuP-88tERy-bGCijr-VPgceC-bnZXFB-7uQ1Z6-hh8qk-LFgtGk​

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