Monday, 9 February 2015

What are hurricanes, typhoons and tropical cyclones?

A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain. Depending on its location and strength, a tropical cyclone is referred to by names such as hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone.

Mexico City

Largest city in Mexico
Mexico City is the capital and largest city in Mexico. It is also one of the most populous and polluted cities in the world. The Aztec people were here before the Spanish came and made Mexico City. It was founded in 1521 by Hernán Cortés. Today, about 8.5 million people live in the city, and about 21.2 million live in the Greater Mexico City urban area. The city of Mexico City ceased to exist in 1928. Since then, there is only the Federal District.

Mexico City has 21.2 million people. It is the city with the second highest number of people in the world after Tokyo in Japan and just slightly more populated than Mumbai in India.

Primate city

Mexico City is a primate city. A primate city is the leading city in its country or region, disproportionately larger than any others in the urban hierarchy.A primate city is number one in its country in most aspects, like politics, economy, media, culture and universities.

A primate city is at least twice as large as the next largest city and more than twice as significant.

Sunday, 8 February 2015

The states of water

Water is known to exist in three different states:

  • solid, 
  • liquid or 
  • gas.

Clouds, snow, and rain are all made of up of some form of water. A cloud is comprised of tiny water droplets and/or ice crystals, a snowflake is an aggregate of many ice crystals, and rain is just liquid water.

Water existing as a gas is called water vapour. When referring to the amount of moisture in the air, we are actually referring to the amount of water vapour. If the air is described as "moist", that means the air contains large amounts of water vapour. 

VIDEO - The states of water

Carbon dioxide

Colourless gas
At normal temperatures carbon dioxide is a colourless gas that exists naturally in the Earth’s atmosphere. The air that we breathe has about 0.03% of carbon dioxide in it. 
Carbon dioxide is an important part of the carbon cycle and essential for life on Earth. Without it temperatures on our planet would be very low.

Plants use the sunlight and take up the CO2 in the atmosphere to produce energy and oxygen. This process is called photosynthesis.

The gas is also produced when fossil fuels are burned. Carbon dioxide that has been stored for millions of years in coal, oil and natural gas is set free. Living creatures produce carbon dioxide when they breathe out. It is emitted from volcanoes and hot springs. Deforestation sets carbon that is stored in trees free.

Greenhouse gas
Carbon dioxide is an important greenhouse gas. Light that enters the atmosphere it is converted to heat. Higher amounts of CO2 make the atmosphere denser and keep it from getting out. CO2 is a gas that is highly responsible for global warming. Since the Industrial Revolution of the 1800s the amount of CO2 in our atmosphere has risen by 40%.

Absorption by nature
Throughout the centuries carbon dioxide has been in balance. Now more carbon dioxide is being produced than can be absorbed by nature.