The Earth, the Sun, and the Stars
Posted by admin in Uncategorized on June 18, 2011
Our Solar System consists of the sun, planets, dwarf planets (plutoids), moons, an asteroid belt, comets, meteors and other objects. The Sun is the centre of our solar system and everything orbits around it.
The Earth is the third planet of our solar system- meaning it is the third from the Sun. Earth is the fifth largest of the eights planets in the Solar System, but the densest. It is the only astronomical body where life is known to exist.
The Earth’s terrain varies from place to place. Roughly 71% is covered by water. The remaining 30% consists of mountains, deserts, plains, plateaus and other geomorphologies.
The Earth provides lots of natural resources, which unfortunately humans have been exploiting for centuries. Some of these are non-renewable resources which are difficult to replace in a short amount of time. Humans have access to useful biological products that are produced by the Earth’s biosphere. These products include, food, wood, oxygen and the recycling of many organic wastes. The ecosystem that exists on land is dependent on topsoil and water. And the ecosystem that exists below water depends on the Earth’s dissolved nutrients.
The Sun is the star at the centre of the Solar System. It is approximately 149.6 million kilometres away from the Earth. It takes about 8 minutes and 19 seconds for light to travel from the Sun to Earth. Almost all life on Earth is supported by the energy of this sunlight. This is achieved via photosynthesis, which is the chemical process of converting carbon dioxide into organic compounds using energy from sunlight. The sun also controls the Earth’s climate and weather patterns.
A star is a luminous ball of plasma held together by gravity. The Sun is a star and it is the star nearest to Earth. By observing the spectrum, luminosity and motion through space of a star, astronomers can determine its age, mass and chemical composition.
For creation and sustainability to take place all parts of our ecosystem must work together. Trees play their part by producing oxygen and reducing carbon dioxide in the atmosphere. They also help to moderate temperatures on Earth. Trees serve many additional purposes such as building material from their wood, fruits from their vines, and their aesthetics for landscaping purposes.
To date humans have exploited quite a lot of the planet’s natural resources. It is of course normal that we would need and use some of them, but it is our responsibility to be as prudent as we can. We need to keep our world prosperous and beautiful.
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Archimedes Principle and Buoyancy
Relating buoyancy to displacement, Archimedes principle forms the basis of the relationship between solid objects and surrounding fluids. Fluids can be either a liquid or a gas, but we’ll be sticking to liquids for this article.
Archimedes principle states that any floating object displaces its own weight of fluid. In more general terms, it can also be stated as: “Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.”
This explains why wood floats and a steel bar doesn’t. The object’s density will determine its behavior when placed in a liquid – whether it will float or sink. As a rule of thumb, if an object has a higher density than water, it will sink, if lower, it will float.
Then Why do Steel Ships Float?
Brilliant question. Steel will float only if its shape allows it to hold enough air to where its density lowers below that of water. This is why a steel bar will sink rapidly, whereas say, a steel bowl of the same mass will float. They both weigh the same amount, but the bowl holds more air within it than the bar and therefore will float due to its lower density.
In contrast, wood doesn’t have to displace as much water for it to float, as it is considerably less dense, and therefore doesn’t need as much force to keep it afloat. Both of these materials obey Archimedes principle.
Deriving an Object’s Volume from its Buoyancy
If an object is square or an otherwise “simple” geometric shape, its volume can be calculated fairly easily. But irregular shapes such as a crown for example, are more difficult. But good news! An object’s volume can be calculated by simply subtracting its mass when it’s submerged from its mass when it’s not, and multiplying by the density of water – which is one. Read the rest of this entry »