Category Science

HOW BIG IS THE EARTH?

          The size of the Earth depends upon how you measure it. If you were to circumnavigate the world (on land and sea) following the Equator, you would travel 40,075km (24,902 miles). Starting at one pole and visiting the other, you would travel 67km (42 miles) less. The Earth’s diameter, pole to pole, is 12,714km (7900 miles), while the distance through the Earth at the Equator is a further 43km (27 miles).

          The radius of Earth at the equator is 3,963 miles (6,378 kilometers), according to NASA’s Goddard Space Flight Center. However, Earth is not quite a sphere. The planet’s rotation causes it to bulge at the equator. Earth’s polar radius is 3,950 miles (6,356 km) — a difference of 13 miles (22 km).

          Earth’s density is 5.513 grams per cubic centimeter, according to NASA. Earth is the densest planet in the solar system because of its metallic core and rocky mantle. Jupiter, which is 318 more massive than Earth, is less dense because it is made of gases, such as hydrogen.

          Earth’s mass is 6.6 sextillion tons (5.9722 x 1024 kilograms). It volume is about 260 billion cubic miles (1 trillion cubic kilometers).

          The total surface area of Earth is about 197 million square miles (510 million square km). About 71 percent is covered by water and 29 percent by land.

          Mount Everest is the highest place on Earth above sea level, at 29,028 feet (8,848 meters), but it is not the highest point on Earth — that is, the place most distant from the center of the Earth. That distinction belongs to Mount Chimaborazo in the Andes Mountains in Ecuador, according to the National Oceanic and Atmospheric Administration (NOAA). Although Chimaborazo is about 10,000 feet shorter (relative to sea level) than Everest, this mountain is about 6,800 feet (2,073 m) farther into space because of the equatorial bulge.

          The lowest point on Earth is Challenger Deep in the Mariana Trench in the western Pacific Ocean, according to the NOAA. It reaches down about 36,200 feet (11,034 meters) below sea level.

Picture Credit : Google

 

HOW LONG DOES THE EARTH TAKE TO ORBIT THE SUN?

          It takes the Earth one whole year to make one full orbit of the Sun.

          Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi), and one complete orbit takes 365.256 days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi). Ignoring the influence of other solar system bodies, Earth’s orbit is an ellipse with the Earth-Sun barycenter as one focus and a current eccentricity of 0.0167; since this value is close to zero, the center of the orbit is close, relative to the size of the orbit, to the center of the Sun.

          As seen from Earth, the planet’s orbital prograde motion makes the Sun appear to move with respect to other stars at a rate of about 1° eastward per solar day (or a Sun or Moon diameter every 12 hours). Earth’s orbital speed averages 29.78 km/s (107,208 km/h; 66,616 mph), which is fast enough to cover the planet’s diameter in 7 minutes and the distance to the Moon in 4 hours.

          From a vantage point above the north pole of either the Sun or Earth, Earth would appear to revolve in a counterclockwise direction around the Sun. From the same vantage point, both the Earth and the Sun would appear to rotate also in a counterclockwise direction about their respective axes.

Picture Credit : Google

 

Why is Venice more vulnerable to floods?

Last month’s flooding is attributed to a combination of factors including strong winds, heavy rains, high tides, which were pushed into Venice by southerly winds. Besides, rising sea levels make the city built amid a system of canals even more vulnerable to inundation.

The sea level around Venice has been rising steadily for decades and it has been attributed to climate change. Globally, the mean sea level is now estimated to be more than 20 cm higher than it was a century ago. Studies show that sea level is still rising 2.4mm a year along Venice. Some estimates suggest the Mediterranean Sea levels will rise by five feet by the end of the century, which could cause the city to flood twice daily. Currently, Venice experiences flooding about four times annually.

Further, the soft and the shifting geological terrain of the city has made the ground level sink gradually by an estimated one millimetre a year. Local industries around Venice make things worse by pumping groundwater from the aquifer under the lagoon.

Because of the combined effect of the city’s terrain and the rising of the sea, the water is now 30 cm higher against the buildings than it was when record-keeping began in 1873.

 

Picture Credit : Google

What is acqua alta?

Acqua Alta or ‘high waters’ is a seasonal phenomenon in Venice. The term is used to refer the exceptionally high tides that occur in the northern Adriatic Sea. The peaks reach their maximum in the Venetian Lagoon and causes flooding in coastal cities Venice and Chioggia.

The phenomenon occurs annually in November and December, when seasonal winds drive strong high tides up canals, through drains, and into the streets of the city.

Venice, built on a cluster of small islands, has always lived with tides that usually create variations of around 50 cm in sea levels but which can sometimes be more extreme, such as the ones experienced last month.

Climate scientists note that exceptional tides – those over 4 feet – have become much more frequent in the past two decades.

Of the 20 exceptional tides recorded since 1936, more than half have occurred after the year 2000.

 

Picture Credit : Google

What caused Venice flooding?

Last month, Venice was hit by three back-to-back floods in less than a week. They sent waist-high water flowing through the Italian city, threatening its iconic Saint Mark’s Basilica and other historic structures. More than 85% of Venice was inundated. The flooding was second only to the waters that inundated the city in 1956, when levels crossed 6 feet.

Venice’s huge Saint Mark’s Square was submerged by more than a metre of water, while the adjacent Basilica was flooded for the sixth time in 1,200 years – but the fourth in the last 20 years.

The floods were primarily driven by the aqua alta, or high tides, which is an annual phenomenon here. But other factors such as climate change and sea level rise made it worse. Experts say that floods of such intensities could become frequent in the coming years.

What is a flood?

A flood is a natural event when an area gets submerge under water for a while. Some floods can occur suddenly and recede in no time. Others take days or even months to build and recede.

Floods can develop in many ways. Heavy rain is one of the major reasons. If it rains hard enough or long enough, low-lying areas get inundated. The flow exceeds the capacity of waterbodies such as rivers, lakes and oceans. When water overflows beyond their boundaries, it leads to flooding. Breach in dams can also cause flooding.

Storm surge – abnormal rise in seawater level during a storm caused primarily by winds – causes the sea to rush inland.

Floods are destructive in nature as huge amounts of water get discharged, leaving no time for evacuation. Sometimes, floods are triggered by other natural disasters such as earthquakes and tsunamis.

What makes an area susceptible to floods?

Any plain low-lying area adjacent to a river or lake is more likely to experience floods whenever the water level rises – for example, a coastal city or a city with a river running through it.
A place’s susceptibility to floods also depends on the capacity of the catchment areas the volume of water hat a river or canal can hold without overflowing. When the amount of rainwater exceeds this capacity, floods may occur.

What is Venice like?

Venice is situated on a group of 118 small islands that are separated by canals and linked by over 400 bridges. The islands are located in the shallow Venetian Lagoon at the head of the Adriatic Sea in Northern Italy. The whole city is an extraordinary architectural masterpiece. The lagoon and a part of the city are listed as a UNESCO World Heritage Site.

 

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How do Snakes, Seals and Walruses inflate?

The elephant seal has a nose that looks like a trunk, hence its name. When the time to mate comes around, the seals inflate their noses by nearly a foot or 30 centimetres! They face off in snorting contests to prove their value to the females.

Walruses on the other hand, puff up their necks to create a natural pillow. The two sacs keep the walrus afloat when it is sleeping in the water.

Among snakes, the puff adder is the only one that can inflate its entire body and let out a loud hiss for good measure. It is a large venomous snake found in some parts of Africa.

 

Picture Credit : Google