Practice Questions: Earth And Universe

Q1: How was the solar system formed?
Ans: About 5 billion years ago, the solar system was a swirling cloud of hot gas and dust. Most of the material came together at the centre to form the Sun, and the rest clumped together to form the planets.

The Earth, the Sun, and the Moon are all part of our solar system. In addition to Earth, there are seven other planets in our solar system.

Q2: What is the Earth and what surrounds it?
Ans: The Earth is the third planet in our solar system. It consists of air, water, and land, and is surrounded by a layer of air called the atmosphere.

The atmosphere protects us from the harmful ultraviolet rays emitted by the sun. Without the atmosphere, life on Earth would not be possible.

Q3: What are the three main layers of the Earth?
Ans: The three main layers of the Earth are the crust (outermost), the mantle (middle), and the core (innermost).

The crust is made of rocks and is where we live. The mantle is hot and gooey with molten rocks. The core is the hottest layer, like a furnace, and is divided into the outer core (liquid) and inner core (solid).

Q4: What is the mantle and how does it cause earthquakes?
Ans: The mantle is located below the crust and is about 2900 km thick. The crust and outer mantle together form tectonic plates that move slowly.

The place where tectonic plates touch each other is called a fault. When the plates move and bump against each other, it causes an earthquake. The mantle also releases magma during volcanic eruptions and contains iron, magnesium, and aluminium.

Q5: What is the outer core and inner core made of?
Ans: The outer core is approximately 2300 km thick and is made of liquid iron and nickel. The inner core is around 1200 km thick and is a solid ball mostly made of iron.

The core is the innermost layer of the Earth. The outer core is liquid while the inner core remains solid due to extreme pressure at the centre of the Earth.

Q6: What is the Sun made of and what happens in its core?
Ans: The Sun is a massive sphere of hot, burning gases, mainly hydrogen and helium. In its core, hydrogen atoms are transformed into helium, releasing a large amount of heat and light energy.

The Sun is located at the centre of the solar system and is the closest star to Earth, about 150 million kilometres away. It has a thin layer of air around it called the corona, and its core is the hottest part.

Q7: Why does the Moon shine? What are its surface features?
Ans: The Moon does not have its own light. It shines because it reflects the sunlight that falls on it.

The Moon's surface is covered with rocks, dust, tall mountains, plains, and large round holes called craters. There is no air or water on the Moon, so no sound can be heard there and no life exists on it.

Q8: What was Apollo 11 and who were the astronauts on board?
Ans: Apollo 11 was the first spacecraft to land on the Moon on 21st July, 1969. It carried three American astronauts - Neil Armstrong, Edwin Aldrin, and Michael Collins.

India's first spacecraft to go to the Moon was Chandrayaan-1, launched on October 22, 2008, from Sriharikota by ISRO. Its goal was to study the Moon's surface, and the mission ended on August 30, 2009.

Q9: What are the phases of the Moon?
Ans: The Moon's different shapes as seen from Earth are called phases. The Moon takes about one month to go around the Earth and goes through phases: new moon, crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent.

On New Moon Day, the side facing us gets no sunlight so we cannot see it. On the fourteenth day, the whole side is lit - this is the Full Moon. The Moon rotates slowly while revolving, so we always see the same side of it.

Q10: What are tides? What causes spring tides and neap tides?
Ans: Tides are the rise and fall of ocean water levels caused by the Moon's gravity pulling water towards it.

When the Sun and Moon line up during a full moon or new moon, we get spring tides, which are very high and low. When the Sun and Moon are at a right angle during the waxing or waning moon, we have neap tides, which are lower than usual.

Q11: What is an eclipse?
Ans: An eclipse occurs when the Sun, Earth, and Moon come in a straight line, and the middle object blocks the light and casts a shadow on the other.

The Sun is a source of light while the Earth and Moon are opaque objects. When any opaque object comes in the path of light, it blocks the light and casts its shadow. This blocking of light is called an eclipse.

Q12: What is a lunar eclipse? What are umbra and penumbra?
Ans: A lunar eclipse happens when the Earth comes between the Sun and the Moon, casting a shadow on the Moon. If the Moon is completely in the Earth's shadow, it is a total lunar eclipse; if only part is covered, it is a partial lunar eclipse.

The dark part of the shadow that blocks all the light is called the umbra. The lighter part of the shadow that only blocks some light is called the penumbra.

Q13: What is a solar eclipse?
Ans: A solar eclipse occurs when the Moon comes between the Sun and the Earth, blocking sunlight from reaching the Earth.

If the Sun is completely blocked, it is a total solar eclipse. If only part of the Sun is visible, it is a partial solar eclipse. Solar eclipses last for a short time, usually just a few minutes.

Q14: What are artificial satellites and what are they used for?
Ans: Artificial satellites are man-made objects that orbit around the Earth. They are used for weather forecasting, transmitting signals for mobile phones, TV programs, and studying outer space.

The first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4, 1957. India's first satellite was Aryabhata, launched in 1975. India also launched the world's first educational satellite, EDUSAT, in September 2004.

Q15: Name three astronauts with Indian roots who have gone to space.
Ans: The three astronauts with Indian roots who have gone to space are Rakesh Sharma, the late Kalpana Chawla, and Sunita Williams.

Space is a lonely and difficult place. People who go there face strong and harmful radiation and need hard training before going on space trips. Man-made satellites help us communicate and predict the weather, while space travel lets us explore beyond Earth.