Q: You hear scientists say that'the light from an object has taken ten billion light years to reach us', but surely ten billion years ago the cosmos was much smaller than it is now – so wouldn't light emitted at that time have long since have passed the area where the solar system would one day form?

Eric Rodger

A: The Universe was initially expanding quicker than the speed of light, and so light was simply not travelling quickly enough to get across the Universe.  Then, the expansion of the Universe slowed, allowing light to travel across the Universe, and finally reach us.  The most distant objects that we can see emitted their light 13.7 billion years ago, and so thanks to the continuing expansion of the universe, those objects will now lie some 46.5 billion light years away.

Dr Darren Baskill, University of Sussex

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Q: I have heard that there was nothing before the 'Big Bang'... I want to know what created the Big bang what was there before it happened?

Michal Stachowicz

A: We have no idea why the Big Bang happened, nor what was there, if anything, before it.  There are lots of ideas, but no data to either prove or disprove any of these.  One idea is there are countless other Universes, all popping in and out of existence all the time.  This is called the multiverse theory, but we have absolutely no evidence to back up this idea, as yet. 

Dr Darren Baskill, University of Sussex

(I have tackled the 'multiverse' a couple of times on Cosm, you can find them here and here – BG)

Q: If a car is driving inside a 100-mile-long spaceship that is travelling at the speed of light, how fast would the car be travelling?
Michal Stachowicz

A: Only light can travel at light speed. The spaceship will travel a little bit slower - say, at 99.999999% of light speed. Inside the spaceship, the car can travel as fast as its driver wants. However, unbeknownst to the driver, time inside the spaceship will slow down. This will be perceived by people looking on from a stationary position outside the spaceship. The car will appear to be moving very slowly so that its speed, taking into account that it is moving forward inside a very fast spaceship, will never reach light speed either.

Jorge Quintanilla, University of Kent

Q: If lived on the moon and I held my breath and was really quick, could I go out without a space suit?
Andrew Norton

A: No, unfortunately you’d explode because there is no atmospheric pressure. Unlike the Earth, the Moon does not have an atmosphere. It would be better to breathe out, but you’d still die due to lack of oxygen
Dr Mike Hardiman,  University of Sussex

Q: If I was weightless in space and my big brother punched me, would it hurt?
Tom Chapel

A: Yes it would. You would both move off in opposite directions (from Newton’s Second Law F=ma where F is the force, m is the mass and a is the acceleration). This results in a sore fist and broken nose
Dr Mike Hardiman

Q: Does the Earth’s magnetic field attract asteroids from space or do asteroids contain any metal?
James (surname not provided)

A: Some asteroids are known to be rich in metals, particularly nickel and iron. Such asteroids may have once formed the cores of even larger asteroids that were broken up by collisions. The Earth’s magnetic field has virtually no effect on the orbits of metal-rich asteroids. This is because the dominant force experienced by the asteroid is the gravitational effect of the Sun – unless it gets really close, the Earth’s gravity has little effect on the asteroid. When an asteroid does hit our planet it is usually because the Earth ‘gets in the way’ of the asteroid’s path around the Sun, rather than being due to Earth’s gravitational attraction
Professor Carl Murray, Queen Mary, University of London

Q: Do we know where the centre of the Universe is? Is it reasonable to presume that would be the site of the Big Bang?
Crispin Cockman

A: The remarkable thing about the universe is that it is the same everywhere and in all directions and has no centre.
How can this be?
The way the universe is expanding is such that the whole of space expands evenly. Take a balloon and inflate it a little. Now with a felt tip pen mark a few dots around the surface of the balloon. Now as you blow up the balloon each one of those dots will appear to move away from every other dot. This is just what we observe in the universe. It is not that there is a central point from which the universe emerged but rather the universe as a whole is expanding just like the surface of the balloon when you blown it up
Dr David Berman, Queen Mary, University of London

Q: Why is time relative to speed? The books say that someone moving away and returning from earth at 80% of the speed of light would be younger, but why is this?
Chris Kyriakou

A: This is known as the twin paradox: one identical twin flies away very fast in a spaceship, turns round and comes back to find his twin is much older than he is. One way to understand this is to imagine that each twin sends a signal to the other everytime he has a birthday (according to their own local clock). During the flight out, each twin sends and receives the same number of signals, though it takes the signals a while to travel. Then, when the traveler decelerates quickly and reaccelerates back to Earth he picks up a huge numbers of pending birthday signals, but without having to send any out. Then on the way back they send and receive the same number.
The twin on Earth has sent more messages and is therefore much older. It is because the traveling twin accelerates that there is a difference between them
Dr Paul Stevenson, University of Surrey