Category Astronomy

WHAT MAKES THE SEASONS?

Earth is always tilted the same direction as it orbits the Sun. So when Earth is on one side of the Sun, the northern hemisphere is tilted closer towards the Sun, making it warmer. At the same time, the southern hemisphere is tilted away from the Sun, and is, therefore, colder. When Earth reaches the other side of the Sun, it is the opposite, so it’s winter in the northern hemisphere and summer in the southern.

Seasons happen at different times in different parts of the world. The tilt of the Earth doesn’t change as it rotates around the Sun. But the part of the planet that gets the most direct sunlight does change.

The Northern Hemisphere is tilted away from the Sun from September to March. That means the northern half of the planet doesn’t get as much light and heat from the Sun. This causes autumn and winter. During the same months, the Southern Hemisphere is tilted towards the Sun. That means the southern half of the planet gets spring and summer.

From March to September, the Northern Hemisphere is tilted towards the Sun. So that’s when the northern half of the Earth experiences spring and summer. During the same months, the Southern Hemisphere experiences autumn and winter.
Other planets also have seasons. But the length and intensity of each season varies from planet to planet.

  • On Earth, seasons last between 90 and 93 days.
  • On Venus, seasons last between 55 and 58 days.
  • On Mars, seasons change about once every six months. Summer lasts 199 days and winter lasts 146 days.
  • On Saturn, seasons last about seven years.
  • And if you lived on Neptune, you would have to wait more than 40 years for the seasons to change!

Credit: Let’s talk Science

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WHAT IS THE PRIME MERIDIAN?

This is an imaginary line of 0° longitude that is perpendicular to the equator, and parallel to the axis. It passes through Greenwich in the UK, and divides Earth into eastern and western hemispheres. As it crosses the poles to the opposite side of the globe, the line becomes 180° longitude and is also known as the International Date Line.

The prime meridian is arbitrary, meaning it could be chosen to be anywhere. Any line of longitude (a meridian) can serve as the 0 longitude line. However, there is an international agreement that the meridian that runs through Greenwich, England, is considered the official prime meridian.

Governments did not always agree that the Greenwich meridian was the prime meridian, making navigation over long distances very difficult. Different countries published maps and charts with longitude based on the meridian passing through their capital city. France would publish maps with 0 longitude running through Paris. Cartographers in China would publish maps with 0 longitude running through Beijing. Even different parts of the same country published materials based on local meridians.

Finally, at an international convention called by U.S. President Chester Arthur in 1884, representatives from 25 countries agreed to pick a single, standard meridian. They chose the meridian passing through the Royal Observatory in Greenwich, England. The Greenwich Meridian became the international standard for the prime meridian.

Credit: National geographic

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WHAT ARE TIME ZONES?

As Earth spins, different parts of its surface turn towards the Sun at different times – the Sun is always rising in one place and setting in another. So, the time of day varies around the world. When it’s dawn where you live, it’s sunset on the other side of the world. To make it easier to set clocks, the world is split into 24 time zones, one for each hour of the day. As you go east around the world, you put clocks forward by one hour for each zone – until you reach an imaginary line called the International Date Line. If you go further on across the Date Line, you carry on adding hours, but put the calendar back by a day.

A time zone is a region on Earth that uses a uniform time. They are often based on the boundaries of countries or lines of longitude. Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory located in Greenwich, London, considered to be located at a longitude of zero degrees. Although GMT and Coordinated Universal Time (UTC) essentially reflect the same time, GMT is a time zone, while UTC is a time standard that is used as a basis for civil time and time zones worldwide. Although GMT used to be a time standard, it is now mainly used as the time zone for certain countries in Africa and Western Europe. UTC, which is based on highly precise atomic clocks and the Earth’s rotation, is the new standard of today.

UTC is not dependent on daylight saving time (DST), though some countries switch between time zones during their DST period, such as the United Kingdom using British Summer Time in the summer months.

Most time zones that are on land are offset from UTC. UTC breaks time into days, hours, minutes, and seconds, where days are usually defined in terms of the Gregorian calendar. Generally, time zones are defined as + or – an integer number of hours in relation to UTC; for example, UTC-05:00, UTC+08:00, and so on. UTC offset can range from UTC-12:00 to UTC+14:00. Most commonly, UTC is offset by an hour, but in some cases, the offset can be a half-hour or quarter-hour, such as in the case of UTC+06:30 and UTC+12:45

Credit: calculator.net

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What is doomsday fiction?

Imagine a world wrecked by a natural disaster, devastated by nuclear war, or destroyed by a pandemic. While this may sound all too familiar because of the prevailing COVID-19 pandemic, apocalypse fiction is a literary genre that has existed for many years. A subset of science fiction, apocalyptic and post-apocalyptic fiction, also known as doomsday fiction, imagines what life will be like at the end of the world.

How it began

An apocalypse is an event that results in mass destruction and change. Although apocalyptic themes exist in many religious texts, the 20th and 21st centuries have given rise to this genre. The aftermath of World War I, World War II, and the nuclear arms race proved to be fertile ground for writers and filmmakers to conjure up a world plagued by zombies, murderous robots, climate change and even a nuclear holocaust

Apocalyptic vs Post- Apocalyptic

Apocalyptic and post apocalyptic literature is set in a time period where the earth as we know it is coming to an end. An apocalyptic novel or film tells the story of the end of the world, unfolding during the timeline of the story. For example, the 2004 film, “The Day After Tomorrow shows what happens when a sudden worldwide storm plunges the entire planet into a new ice age. On the other hand, post-apocalyptic works portray life in the wake of a cataclysmic event. They focus on how the characters deal with the consequences of a disaster. A 2007 film “1 am Legend” starring Will Smith, is a good example. It follows Robert Neville, a scientist who is the last human survivor of a plague in the whole of New York, as he attempts to find a way to reverse the effects of the human-made virus.

Popular examples

Books written under this genre can be broadly classified (based on their themes) into post-disaster wastelands zombie apocalypse, nature gone wrong, machines taking over the world, and dystopian worlds. Here are a few examples.

Post-disaster wastelands

  • “The Stand” by Stephen King
  • “The Mad Max” film series by James McCausland and George Miller

Zombie Apocalypse

  • World War Z by Max Brooks
  • “The Walking Dead”, a graphic novel series by Robert Kirkman, Tony Moore, and Charlie Adlard

Dystopian worlds

  • “The Hunger Games” by Suzanne Collins
  • “Divergent” by Veronica Roth

Machines taking over

  • “The Maze Runner by James Dashner
  • The Big Melt” by Ned Tillman

 

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