Gravity...Houston, we have a hit | Film Review

It's been exactly two years since the multi-award winning film, 'Gravity' was released in the UK. But here's my opinion of the hit film.

On the 28th January 1986 everything changed for America. The US news network, CNN carried live pictures of the routine challenger space shuttle launch. Although what was far from ordinary was the shuttle carried the first female civilian to go into space, 37 year old teacher Christa McAuliffe, chosen from over 11,000 applicants. What captured the collective imagination of the American people,soon, 73 seconds later ended in a tragic disaster. All seven crew members were killed and never made it into space.

The event, watched eagerly by millions worldwide shocked and tramatised the nation, just as the 9/11 attacks did some 15 years later. But the smash hit Gravity has the same ingredients, a female in space, Dr Ryan Stone played by Sandra Bullock going about her business with colleague Dr Kowalski played by George Clooney, when an onslaught of space debris hits the international space station (the ISS). First tethered to safety, the race is on to save the space station and more importantly to save their lives.

With the tilted Earth shimmering like a blue marble, circling them below, the film is a cinematic virtue and there's some science too.

The average space station commander logs around 4,000 hours at a time on board the football-field sized vehicle. Hollywood has officially accomplished the mission to make your children think space is cool.

Why do galaxies collide?

Well, they collide due to their 'mutual gravitational attraction' in other words they collide because gravity draws them together. However in general galaxies are moving away from each other at an ever increasing rate, basically because of the Universe expanding at an ever increasing rate. This can be modeled simply by drawing stars or dots (imagine these as galaxies) onto a deflated balloon then blowing up the balloon. An idea that has sprung from this is the Red Shift. This is where astronomers have found that the further away a star is the more it's light has been red shifted. So this tells us that distant galaxies are moving away from us and that the further away a galaxy is the faster away its moving away from us.

The Red Shift is an example of the Doppler effect, named after the Austrian physicist Christian Doppler who proposed this theory in 1842 in Prague. You may have noticed that as a police car comes towards you the siren becomes high pitched and low pitched as the car drives away. This effect is where there is a change in frequency and wavelength. So when a source moves towards an observer the observed wavelength decreases and frequency increases and vice versa. In terms of Astronomy the results of the Doppler effect are used to identify if a nearby star is what astronomers call a binary star. This is two stars orbiting around a 'common center of mass' which is where the relative position of the distributed mass adds to zero. The brighter star is called the 'primary star' and the other the 'secondary star'

In our own 'Local Group' of galaxies for example some of the galaxies are moving away from us and some are moving towards us. Take our nearest galaxy the Andromeda galaxy for example which is currently moving towards the Milky Way at 402, 336 km/h and is due to hit us in 4 billion years.

If the Sun's gravity was reduced what would happen to us?

A sudden reduction in the Sun's gravity would trigger massive earthquakes on earth as we were shifted along with Earth's altered orbit. However finding something that would cause this would be very difficult! A slow reduction in gravity would mean that the earths orbit would slowly be altered. In fact what happens is the Sun's mass decreases very slightly converting it into heat and light. To put this into context the mass that the sun looses each year is about 0.25% of the sun's mass since it first was formed. Also as the Sun grows older the Sun also gets brighter which means the Earth stays warm.