Category Physics

WHAT IS EARTH MADE OF?

The structure of Earth can be divided into three parts: the crust, the mantle and the core. Made up from mainly oxygen and silicon, the crust is the outermost layer. It is the familiar landscape on which we live: rocks, soil and seabed. Beneath the crust is the mantle, a layer almost 3000 km deep. It is made of metal silicates, sulphides and oxides. This layer is so hot that the rock often flows like sticky road tar – only very, very slowly. Below the mantle is a core of metal, mostly iron, sulphur and nickel. The outer portion of the core is so very hot that the metal is always molten. The Earth’s magnetic field is created here. Earth’s inner core is even hotter – estimated to be around 6000 °C – but the metal is solid because pressure within the inner core is extreme, so the metal cannot melt.

1: The Core

The composition of the Earth begins with the inner parts of the planet. The Earth’s core is the densest part of the planet. It is made up of iron and nickel, and the core is so hot that is heats the rest of the planet around it. The core has chosen how the planet will be heated, and the core of the planet determines the equilibrium of the planet itself.

2: The Magma

The magma underneath the Earth’s surface spins around the world as it keeps the crust warm. The warmth of the magma can be felt in certain parts of the world where the ground is very close to the magma. The magma can be found rising out of the surface of the Earth at volcanoes and underwater cracks in the crust. The magma is the lifeblood of the Earth even though it is quite a scary thing to encounter today.

3: The Crust

The crust of the Earth is the ground that everyone walks on today. The crust is much thinner than the other components of the Earth, but it manages to support all the life on the planet. The Earth’s surface is covered with the crust completely, but much of the Earth’s surface is covered in water. Citizens of the Earth may never explore the floor of the sea, but that area is still a part of the Earth’s crust.

4: Magnetism

The magnetism of the Earth that helps it stay attached to the sun in orbit comes directly from the core. The core’s construction keeps the magnetism of the Earth going in ways that scientists do not understand completely. The magnetism created by the core also helps the Earth create a gravitational field that keeps everyone on the planet.

Credit: AES

Picture credit: Google

HOW DO WE KNOW WHAT EARTH’S INSIDE LOOK LIKE?

Scientists have worked this out from the vibrations from earthquakes and underground explosions. This data is pictured with lines on 3D maps to help scientists understand the structure of Earth’s core.

Core, mantle, and crust are divisions based on composition. The crust makes up less than 1 percent of Earth by mass, consisting of oceanic crust and continental crust is often more felsic rock. The mantle is hot and represents about 68 percent of Earth’s mass. Finally, the core is mostly iron metal. The core makes up about 31% of the Earth.

CRUST AND LITHOSPHERE

Earth’s outer surface is its crust; a cold, thin, brittle outer shell made of rock. The crust is very thin, relative to the radius of the planet. There are two very different types of crust, each with its own distinctive physical and chemical properties.Oceanic crust is composed of magma that erupts on the seafloor to create basalt lava flows or cools deeper down to create the intrusive igneous rock gabbro. Sediments, primarily muds and the shells of tiny sea creatures, coat the seafloor. Sediment is thickest near the shore where it comes off the continents in rivers and on wind currents.

MANTLE
The two most important things about the mantle are: (1) it is made of solid rock, and (2) it is hot. Scientists know that the mantle is made of rock based on evidence from seismic waves, heat flow, and meteorites. The properties fit the ultramafic rock peridotite, which is made of the iron- and magnesium-rich silicate minerals. Peridotite is rarely found at Earth’s surface.Scientists know that the mantle is extremely hot because of the heat flowing outward from it and because of its physical properties. Heat flows in two different ways within the Earth: conduction and convection. Conduction is defined as the heat transfer that occurs through rapid collisions of atoms, which can only happen if the material is solid. Heat flows from warmer to cooler places until all are the same temperature. The mantle is hot mostly because of heat conducted from the core. Convection is the process of a material that can move and flow may develop convection currents.

CORE
At the planet’s center lies a dense metallic core. Scientists know that the core is metal for a few reasons. The density of Earth’s surface layers is much less than the overall density of the planet, as calculated from the planet’s rotation. If the surface layers are less dense than average, then the interior must be denser than average. Calculations indicate that the core is about 85 percent iron metal with nickel metal making up much of the remaining 15 percent. Also, metallic meteorites are thought to be representative of the core.If Earth’s core were not metal, the planet would not have a magnetic field. Metals such as iron are magnetic, but rock, which makes up the mantle and crust, is not. Scientists know that the outer core is liquid and the inner core is solid because S-waves stop at the inner core. The strong magnetic field is caused by convection in the liquid outer core. Convection currents in the outer core are due to heat from the even hotter inner core. The heat that keeps the outer core from solidifying is produced by the breakdown of radioactive elements in the inner core.

Credit: Lumen Learning

Picture credit: Google

Does your shadow follow you?

A girl walking in the midday sun and could see her small shadow following her. There was a plane flying high overhead but it threw no shadow on the ground. Why?

If an object is placed between a source of light and a screen, a shadow falls on the screen. If the object is smaller than the source of light then the shadow will have a small dark centre called umbra and a larger and lighter shadow surrounding it called the penumbra.

The further you move the object from the screen and towards the source of light, the smaller the umbra. If you take it very far from the screen, the umbra disappears.

The plane high in the sky is the object between the source of light (sun) and the screen (ground). It’s too far away from the screen so there’s no umbra and the penumbra is so faint that it cannot be seen.

Picture Credit : Google 

“Give me a place to stand on and I will move the Earth.” said Archimedes in 240 BC. What did he mean?

At least in principle any load can be moved by a lever. A lever is a rigid uniform rod resting on a fixed point called fulcrum at which point it can rotate freely. The length of the lever from this fulcrum to the load is load arm and the length from fulcrum to the point where effort is applied is the effort arm. The lever is balanced when Effort x effort arm Load x load arm. If the effort arm is 100m and load arm 1m, the effort needed to lift 1000 kg will be just 10 kg. So keeping the effort arm proportionally long one can in priciple lift any load and that is what Archimedes was trying to say by this boastful statement.

Picture Credit : Google 

Why is it difficult to cook rice or dal when you’re in a place that is at a higher altitude?

The lower the atmospheric pressure, the lower the boiling point of water. At the top of Mount Everest where the atmospheric pressure is less than one-third of what it is at sea level, water boils at around 70 degrees Celsius, whereas in a place like Mumbai, water boils at 100 degrees C

Rice and dal require this higher temperature to get cooked. So though the water may boil at the top of Everest, it will not be hot enough for the rice or dal to cook in it.

The problem can be overcome by using a pressure cooker. In a pressure cooker, due to the high pressure created inside it, water boils at much higher temperatures than normal and so food gets cooked faster.

Picture Credit : Google 

When did Surveyor 3 land on the Moon?

Launched on April 17, 1967, Surveyor 3 was the third engineering flight of the Surveyor series and the second in the series to achieve a soft landing on the moon. It was based on Surveyor 3’s surface sampling tests that it was concluded that the lunar surface could hold the weight of an Apollo lunar module

The Apollo 11 mission will remain in the collective consciousness of human beings forever. This is because it was the first time we humans managed to set foot on our natural satellite, the moon.

It is important to remember that this was made possible due to a number of missions that preceded this one. Among these was the Surveyor 3 spacecraft which proved beyond doubt that an Apollo lunar module could indeed safely land on the moon’s surface.

The third engineering flight of the Surveyor series, this spacecraft was the first to carry a surface-sampling instrument that could reach up to 1.5 m from the lander and dig up to 18 cm. Unlike its predecessors, Surveyor 3 began its mission from a parking orbit around Earth on April 17, 1967.

Bouncing to a stop

While it became the second in the series after Surveyor 1 to achieve a soft landing on the moon three days later on April 20, it was far from smooth. As highly reflective rocks confused the landers descent radar, the main engine did not cut off at the correct moment during the descent to the lunar surface.

This meant that Surveyor 3 bounced off the moon, not once but twice-first to a height of 10 m and then again to a height of 3 m. It was third time lucky for Surveyor 3 as it landed softly in the southeastern region of Oceanus  Procellarum.

With its worst behind it. Surveyor 3 set out to do what it was sent to do. Within an hour after landing, the spacecraft began transmitting the first of over 6,000 TV pictures of the surrounding areas.

Similar to wet sand

The most important phase of the mission included deployment of the surface sampler for digging trenches, manipulating lunar material, and making bearing tests. Based on commands from Earth, the probe was able to dig four trenches, performing four bearing tests and 13 impact tests.

The results from these experiments were the most important aspect of this mission. The scientists were able to conclude that lunar soil’s consistency was similar to that of wet sand and that it would be solid enough to bear an Apollo lunar module when it landed.

The start of May saw the first lunar nightfall following the arrival of Surveyor 3. The spacecraft’s solar panels stopped producing electricity and its last contact with Earth was on May 4. While Surveyor 1 could be reactivated twice after lunar nights, Surveyor 3 could not be reactivated when it was attempted 336 hours later during the next lunar dawn.

Tryst with Apollo 12

That, however, wasn’t the last of what we heard about Surveyor 3. Four months after the huge success of Apollo 11, NASA launched Apollo 12 in November 1969. The lunar module of Apollo 12 showcased pinpoint landing capacity as the precise lunar touchdown allowed the astronauts to land within walking distance of the Surveyor 3 spacecraft. During their second extra vehicular activity on November 19, astronauts Charles Conrad, Jr. and Alan L. Bean walked over to the inactive Surveyor 3 lander and recovered parts, including the camera system and the soil scoop.

Just like moon rocks, these were returned to Earth for studying, as they offered scientists a unique chance to analyse equipment that had been subjected to long-term exposure on the moon’s surface. The studies of the parts showed that while Surveyor 3 had changed colour due to lunar dust adhesion and exposure to the sun, the TV camera and other hardware showed no signs of failure.

While NASA placed some of the Surveyor 3 parts into storage along with moon rocks and soil samples, the remaining parts found home elsewhere. Even though NASA treats them as lunar samples and not artefacts, they are greatly valued when gifted or loaned out, both to museums and individuals.

Picture Credit : Google