# The Big Bang Live Lesson - Questions and Answers

Thank you to all who emailed us with questions for Professor Brian Cox.

As we were only able to answer a small number of questions during the live lesson, our science adviser Alessio Bernadelli has been working hard to try and answer as many questions as possible.

1. How fast is the speed of light?
From: Cameron Botting, Y7, Henry Beaufort School

The speed of light is 299792458 m/s, i.e. nearly 300 thousand kilometers per second.

2. What is a ‘Light year’ and how would you measure it?
From: Cameron Botting, Y7, Henry Beaufort School

A light year is actually a measure of distance used in astronomy because of the huge distances we deal with in that area of Physics. It is the distance a photon of light would travel in a whole year and it is really long. If you do the calculations you get that 1 light year = 94.5 x 1012 km, i.e. about 95 followed by 12 zeroes, or 95 thousand trillions of kilometers. The nearest star to the sun is Proxima Centauri and their distance apart is 4.3 light years – this should give a vague idea of how massive the universe is.

3. Why is there no atmosphere on the moon?
From: Lucy in 6J, Blackpool

Because the gravitational pull of the moon is not strong enough to hold gases around it, as the moon has only about 1/6 the mass of the earth.

4. How big is the universe?
From: Class 5, All Saints in Marple, Stockport

Although our view of the universe is limited, our imaginations are not. Astronomers have indirect evidence that the universe of galaxies extends far beyond the region we can see. But no one knows if the whole universe is infinitely large - large beyond limit.

According to the leading theories, other parts of the universe may look very different from our own - and may even have different laws of nature. We may never be able to find out for sure. But it is possible that clues to the answer lie in plain view, just waiting to be discovered!

5. How did the rings get on Saturn?
From: Class 5, All Saints in Marple, Stockport

A possible theory is that Saturn’s rings formed when objects like comets, asteroids or even moons broke up in orbit around Saturn due to Saturn’s very strong gravity. The pieces of these objects kept colliding with each other and broke into even smaller pieces. These pieces gradually spread around Saturn to form its rings, which are mainly made of ice.

6. What is the biggest crater ever made?
From: Class 5, All Saints in Marple, Stockport

The largest crater in the Solar System is located on the Moon. The impact crater is named the South Pole-Aitken basin. It is in about 2,500 km in diameter and is 13 km deep.

7. How does a magnet really work?
From: Meghan, S2, Scotland

A brilliant physicist called James Clerk Maxwell was able to link all magnetic effects to electricity. Every moving charge generates a magnetic field, so there is a magnetic field around any wire carrying an electric current in your house. In a similar way, electrons orbiting the nucleus of an atom are moving charges and each single atom therefore generates a tiny magnetic field thanks to its moving electrons. In magnets all atoms are aligned in a particular way – this means that the magnetic force produced by each atom in the magnet adds up to produce an overall magnetic field that is strong enough to be noticed and measured.

8. Does the upthrust of water change depending on the mass of the object?
From: Finn, S2 Scotland

For a floating object the upthrust on the object must be equal to the weight of the object, so the upthrust would increase if the weight of the floating object increased.

9. Are there many jobs in science?
From: Nick in 6J Layton Primary School

There are many jobs in science! People often think of science jobs only as someone working in a lab, but you can be a scientist and work in finance, business and many other areas. The skills you develop through a science degree allow you to take a wide range of roles. There are many areas of science research that are incredibly interesting and many questions that still need to be answered. You do not need to be a genius to become a successful scientist, you just need to love science and persevere.

10. How many galaxies are there in the universe?
From: Zach Mapleston

It is difficult to tell with certainty, because current technology allows us only to see a portion of the whole universe. The most recent estimates predict that there could be around 100 to 200 billion galaxies in the Universe.

11. How did space appear and will it ever disappear?
From: Dayna Oberg

The most popular theory about the origin of space (and everything else, including time) is the Big Bang Theory, which states that 14 billion years ago space, and all matter in the universe, was formed in a huge “explosion”. This explosion caused all matter and space to expand out of a single point. Many scientists interpret the observation that all galaxies are moving further away from each other (and that the space they exist in is also expanding) as evidence that everything started from a single point and exploded away.

12. How long did the Big Bang go on for?
From: St Ninian’s Primary School, Perth

The Big Bang Theory states that there are various stages of the Big Bang and it took about 400 million years for the first star to be born.

13. What caused the Big Bang?
From: St Ninian’s Primary School, Perth

We don’t really know what caused the Big Bang. Some scientists believe that there was a singularity, or a fluctuation, that caused all space and matter to expand very rapidly from this single point of high energy. What caused that singularity is unknown.

14. Why do we have all of the planets?
From: St Ninian’s Primary School, Perth

It is believed that solar systems like ours formed from clusters of gas (nebulae). As more and more particles gather together by the force of gravity, enough mass starts to collect and the gravitational pull attracts even bigger objects towards the centre of the cluster. Eventually very large objects begin to form and the pressure in the centre become so high that some particles begin to fuse together (merge). This is called nuclear fusion and it is the beginning of stars. Planets form in a similar way around stars, but never get large enough to start nuclear fusion. Instead, they usually become very large masses of rocks, metal and other elements.

15. How many stars are in space?
From: St Ninian’s Primary School, Perth

It is estimated that there are about 200 billion galaxies in the universe, each with about 100 to 200 billion stars. So, there could be about 40000 billion billion stars, i.e. 4 followed by 29 zeroes.

16. Will Mankind ever be able to colonise on a different planet before our species dies out?
From: Cameron, Y8, William Brookes School, Bethany Berry from Christopher Whitehead Language College

There are plans to organise a manned mission to Mars and we have sent astronauts on the moon already, but actual colonization of a new world would take a lot more effort than that. The main hurdle would be to find a planet that can sustain life in the same way as our earth does, so the right temperature, water, etc. The main problem is that there is no such planet in the Solar System. The closest star is 4.3 light years away from our sun, so even if we could get there (which is in itself very unlikely), we might not find a planet that is suitable for us to live in. In other words, I think it is highly unlikely we will ever be able to do that and a much more viable option is to make sure we take as much care as we can of our own world. However, some scientists are looking into the possibility of building a spacecraft capable of transporting men as far as Alpha Centauri (another star relatively near the sun) where a planet with similar elements as the earth was found. That planet is too close to its star and would be too hot, but it is possible that other planets orbit around the same star and that we could find one that is right for supporting human life.

17. How was the moon made?
From: Aimee, Y7 Parkside Middle School

Some scientists believe the moon could have been formed from the collision of a large object, possibly a planet, with the earth.

18. Is it possible to live in space?
From: Ruby, Y7 Parkside Middle School

Yes – to some extent! Scientists at the International Space Station live in orbit around the earth for many months, but they need to constantly exercise so their muscles do not become too weak. They also need to receive supplies from earth, such as food and water, so we don’t have a way to actually live in space indefinitely without replenishing supplies from Earth.

19. Does space go on forever?
From: Michael Clayden, Keep Hatch Primary and Kyle Kilminster from Christopher Whitehead Language College

The universe is constantly expanding and measurements of the rate of expansion of space show that it is actually accelerating.

20. What is the biggest galaxy?
From: Daniel Brady, Keep Hatch Primary

The spectacular spiral galaxy NGC 6872 is the biggest yet seen. It is 5 times bigger than our Milky Way.

21. How do shooting stars happen?
From: Lily Hoban, Keep Hatch Primary

Shooting stars are not actual stars but bits of cosmic dust and small rocks that hit the earth’s atmosphere. They travel into our atmosphere so quickly that the friction between the air and these small objects makes them glow really bright and leave a tail as they burn in their fall towards the earth. Most of these objects vaporise before they hit the ground.

22. What are stars made of?
From: Elizabeth Garlish, Keep Hatch Primary

Mainly Hydrogen and Helium, but as they “burn” by nuclear fusion the form heavier elements such as carbon.