Simplified P2 - Threats to Earth , The Big Bang

Question 1

What are asteroids?

Answer 1

Asteroids are mini planets or planetoids orbiting the sun:

• Most orbit between Mars and Jupiter
• They are large rocks that were left over from the formation of the solar system.

Question 2

How were all bodies in space formed?

Answer 2

All bodies in space, including planets were formed when clouds of gas and dust collapsed together due to gravitational forces of attraction.

Question 3

What determines an objects gravitational force?

Answer 3

The mass of an object determines its gravitational force.
Asteroids have relatively low masses compared to the mass of Jupiter, however Jupiter’s gravitational force prevents asteroids from joining together to form another planet.

Question 4

How do scientists believe the moon was formed?

Answer 4

Scientists believe the moon was a result of the collision between two planets in the same orbit, the iron core of another planet melted and joined with the Earth’s core, less dense rocks began to orbit and they came together to form the moon.

Question 5

What scientific evidence supports the current most popular theory of the formation of the moon?

Answer 5

• There is no iron in the moon
• The moon has exactly the same oxygen composition as the Earth, but rocks on Mars and meteorites form other parts of the solar system have different oxygen compositions
• The average density of Earth is 5500 kg/m3 whereas the the density of the moon is only 3300 kg/m3.

Question 6

What evidence have geologists found and examined to support the theory that asteroids have collided with Earth?

Answer 6

• Near to a crater thought to have resulted from an asteroid impact, they found quantities of the metal iridium, a metal not found normally in the Earth’s crust but common in meteorites.
• Many fossils are found below the layer of iridium, but a few are found above it.
• Tsunamis have disturbed fossil layers, carrying some fossil fragments up to 300km inland.

Question 7

What happens to the speed of a comet as it approaches the sun?

Answer 7

The speed of a comet increases as it approaches the sun, and decreases as it gets further away, this is because of gravitational attraction.

Question 8

Where do most comets orbit?

Answer 8

Most comets pass inside the orbit of mercury and well beyond the orbit of pluto.

Question 9

Why is there a comet trail?

Answer 9

As the comet passes close to the sun, the ice melts and solar winds blow the dust into the comet’s trail which always points away from the sun.

Question 10

What is meteor made from?

Answer 10

A meteor is made from grains of dust that burn up as they pass through the Earth’s atmosphere.

Question 11

Why is there is a shooting star streak?

Answer 11

Meteors heat the air around them, which glows and the streak is known as a shooting star.

Question 12

What did Galileo observe?

Answer 12

With the help of the newly invented telescope, Galileo observed four moons orbiting Jupiter, and this confirmed that not everything orbited the Earth and supported Copernicus’ idea that planets orbited the sun.

Question 13

Why did people refuse to believe Galileo’s ideas?

Answer 13

The Roman Catholic church did not support Galileo’s model as the believed that the Earth was at the centre of the universe, it took a very long time before it was accepted.

Question 14

What did newton discover?

Answer 14

In the 17th century, Newton was working on his theory of universal gravitation which suggested that all bodies attract one another.

Question 15

Why do we believe that gravitational collapse is prevented today?

Answer 15

Today, we believe that gravitational collapse is prevented because the universe is constantly expanding as a result of the big bang.

Question 16

What is the red shift?

Answer 16

When a source of light is moving away from its observer, its wavelength appears to increase which shifts light towards the red end of the spectrum - red shift.

Question 17

What is a nebula?

Answer 17

A nebula is a swirling cloud of gas and dust.

Question 18

What is the entire life cycle of a star?

Answer 18

• Nebula clouds are pulled together by gravity, and as the spinning ball of gas starts to get hot, it glows. This protostar cannot be seen because of the dust cloud.
• Gravity causes the star to become smaller, hotter and brighter, and after millions of years the core temperature is hot enough for nuclear fusion to take place, as hydrogen nuclei join together to form helium nuclei, energy is released and the star continues to shine while there is enough hydrogen.

Question 19

Why do small stars shine for longer than large stars?

Answer 19

Small stars shine for longer than large stars because they have less hydrogen but use it up at a slower rate, and what happens at the end of a star’s life depends on its size.

Question 20

What happens at the end of a medium sized star’s life?

Answer 20

• A medium star like the sun becomes a red giant, while the core contracts the outer part cools changes colour from yellow to red and expands.
• Gas shells, called planetary nebula are thrown out.
• The core becomes a white dwarf shining very brightly but eventually cools to become a black dwarf.

Question 21

What happens at the end of a large star’s life?

Answer 21

• Large stars become red super-giants:
• As the core contracts and the outer part expands, the core collapses to form a neutron star, and there is an explosion called a supernova
• Neutron stars are very dense
• Remnants from a supernova can merge to form a new star
• The core of the neutron star continues to collapse, becomes even more dense and could form a black hole