Hollywood under the microscope

Would real space battles look and sound just like they do in ‘Star Wars’? And could Bruce Willis’s bomb save us from an asteroid? Adam Weiner puts screen science to the test


Star Wars

In a galaxy far, far away, Luke Skywalker and Princess Leia are locked in a battle for the freedom of the Republic. Within the numerous battles that ensue, ships of every size, shape and political affiliation launch their attack across the vastness of space. The Millennium Falcon and the Death Star – as well as all kinds of spacecraft in between – are featured heavily as deafening lasers whizz and screech across the dark, starry backdrop.

Now, let's not be silly about this: you have to assume that a long, long time ago, in a galaxy far, far away, they knew how to build these space ships. But here's the thing – sound can't travel in a vacuum, so the dramatic inter-galactic combat wouldn't be quite as breathtaking as it seems in the film. There is no sound in space, no matter what George Lucas might have you believe. In a nutshell, the speed of sound is 340 metres per second through air. It travels much faster in water or solids, but in a vacuum there is no matter for sound waves to travel through.

And it's not just George who's guilty of perpetuating the myth – Star Trek, Galaxy Quest, and Starship Troopers all fall prey to the same notion. The only notable exception is 2001: A Space Odyssey, which uses the stillness of space to its advantage – the strains of "Daisy, Daisy, give me your answer, do" wouldn't sound quite so menacing against a backdrop of anything but deathly silence.



Batman

The1989 Batman, with Michael Keaton, is a great example to showcase film physics. When Batman and Kim Basinger are dangling over a ledge, they lose their grip and fall before Batman’s retractable rope-hook catches on a gargoyle, saving them from crashing to death on the ground below. Would it really save them, though? Remember that the principal feature that distinguishes Batman from other superheroes is that he has no superpowers. So here’s where the physics doesn’t add up. It doesn’t matter whether a fall is interrupted beforeimpact with the ground; if the deceleration is sharp enough, severe injury is just as likely as in hitting the ground. To alleviate the effects of the forces and resulting negative acceleration (or deceleration), their magnitude must be reduced by increasing the time over which the forces occur. The rope does no good unless it is very elastic, like a bungee cord. Batman’s rope isn’t; he and Kim Basinger are brought to an abrupt halt.

Rapid accelerations and decelerations in humans would cause large bones to break, and internal injuries are possible. This is a result of Newton’s First Law: internal organs aren’t fixed to the frame of the body, so they will continue to move “at a constant speed in a straight line until acted on by a net external force”. That is, until they splat on your ribcage

Armageddon

The scenario: scientists have discovered an asteroid on a direct collision course with Earth. If the asteroid hits, it will destroy all life on the planet. Billy Bob Thornton and his Nasa staff have to divert the asteroid before it hits. The solution involves flying a space shuttle out to the asteroid, carrying a nuclear bomb to be placed in a hole that Bruce Willis is going to drill into the rock. The explosion will blow the asteroid in half, and each half will be deflected to either side of Earth. We are told the asteroid is “the size of Texas”, which means it has a diameter of about 700 miles.

Bruce Willis and his crew drill a hole that is only 800 feet deep to get the bomb inside the asteroid. If you draw a figure to scale, you can see that for all practical purposes they are exploding the bomb on the surface. Not only that but the asteroid must also split into just two roughly equal-size halves in order to change from its Earth-bound course. So does the bomb have enough energy to ensure that a) the asteroid will split into just two fragments instead of shattering into space rubble, and b) the fragments would be blown apart with enough force to miss the Earth? No problem. Bruce Willis and his crew have a 100-megaton nuclear bomb, after all. But hang on, according to my calculations that would explode with only one-hundred-millionth of the energy needed. Assuming all the energy of a nuclear bomb can be converted into the kinetic energy of the asteroid, and assuming the bombs are able to split the asteroid into fragments, that would be blown far enough from their current course to miss the Earth, another 70 or 80 million bombs of that size would be needed.

The Day After Tomorrow

The Day after Tomorrow is an end-of-the-world disaster movie, and this time it’s all about bad weather. The premise is based loosely on a controversial theory that global warming could end up triggering a global deep-freeze. Any discussion of weather clearly calls for a little foray into the principles of thermodynamics. The controversial theory in The Day after Tomorrowis that global warming causes melting of glacial ice, and that the influx of fresh water reduces the salinity of the oceans in those areas. This could affect something called thermohaline circulation, which affects ocean convection. The amount of warm water flowing into the North Atlantic is reduced, cooling parts of the northern hemisphere.

The film slams this theory in overdrive as it leads to an “instant ice age”. Probably the most dramatic phenomenon in The Day after Tomorrow is the famous masses of air descending, at -100C, to the surface from the upper layer of the Earth’s atmosphere, causing everything to freeze instantly. But these temperatures in the upper part of the troposphere, the lowest layer of the atmosphere, only range from around -45C to -75C. And even if the air magically got that chilly at the top of the troposphere, its descent would warm it up. It seems that there might be a moment of physics clarity when Ian Holm, as meteorologist Terry Rapson, asks, “Shouldn’t the air warm up as it descends?” Yes, it should! On its way down, the cold air has to be compressed, and that means it heats up.

Independence Day

In this 1996 version of the “aliens invade Earth” plot – and in spite of the fact that the aliens’ technology is incomprehensibly advanced – the humanssomehow hack into the alien computer system and blow up the gigantic mother ship. Along the way, we’re told the mother ship has a mass equal to one-quarter the mass of the Moon and is in geosynchronous orbit above the Earth, more than 10 times closer than the Moon.

The ship’s gravity would cause huge tides, totally destroying coastal areas, and probably flex the Earth’s crust enough to cause catastrophic earthquakes. Still, the aliens send out smaller craft (each about 15 milesacross) to hover before unleashing flaming death-rays. Here, we cannot ignore Newton’s Third Law: to allow a ship to hover, there must be an upward force equal to the weight acting on it. So the ship must be exerting a downward force. If this involves air, the city beneath will be crushed by air pressure. So why waste energy on those death rays?



Adam Weiner is the author of Don’t Try This At Home: The Physics of Hollywood Movies, published in the US by Kaplan. Excerpted by permission from Kaplan Publishing, a division of Kaplan, Inc. © 2007 Kaplan, Inc

Start your day with The Independent, sign up for daily news emails
ebooks
ebooksAn introduction to the ground rules of British democracy
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
SPONSORED FEATURES
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Sales Executive or Senior Sales Executive - B2B Exhibitions

£18000 - £30000 per annum: Recruitment Genius: A Sales Executive or Senior Sal...

Recruitment Genius: Head of Support Services

£40000 - £55000 per annum: Recruitment Genius: This is an exciting opportunity...

Recruitment Genius: Warehouse Team Leader

£22000 per annum: Recruitment Genius: This industry leading company produces h...

Recruitment Genius: Business Development Manager / Sales - OTE £40,000

£20000 - £40000 per annum: Recruitment Genius: This IT provider for the educat...

Day In a Page

A nap a day could save your life - and here's why

A nap a day could save your life

A midday nap is 'associated with reduced blood pressure'
If men are so obsessed by sex, why do they clam up when confronted with the grisly realities?

If men are so obsessed by sex...

...why do they clam up when confronted with the grisly realities?
The comedy titans of Avalon on their attempt to save BBC3

Jon Thoday and Richard Allen-Turner

The comedy titans of Avalon on their attempt to save BBC3
The bathing machine is back... but with a difference

Rolling in the deep

The bathing machine is back but with a difference
Part-privatised tests, new age limits, driverless cars: Tories plot motoring revolution

Conservatives plot a motoring revolution

Draft report reveals biggest reform to regulations since driving test introduced in 1935
The Silk Roads that trace civilisation: Long before the West rose to power, Asian pathways were connecting peoples and places

The Silk Roads that trace civilisation

Long before the West rose to power, Asian pathways were connecting peoples and places
House of Lords: Outcry as donors, fixers and MPs caught up in expenses scandal are ennobled

The honours that shame Britain

Outcry as donors, fixers and MPs caught up in expenses scandal are ennobled
When it comes to street harassment, we need to talk about race

'When it comes to street harassment, we need to talk about race'

Why are black men living the stereotypes and why are we letting them get away with it?
International Tap Festival: Forget Fred Astaire and Ginger Rogers - this dancing is improvised, spontaneous and rhythmic

International Tap Festival comes to the UK

Forget Fred Astaire and Ginger Rogers - this dancing is improvised, spontaneous and rhythmic
War with Isis: Is Turkey's buffer zone in Syria a matter of self-defence – or just anti-Kurd?

Turkey's buffer zone in Syria: self-defence – or just anti-Kurd?

Ankara accused of exacerbating racial division by allowing Turkmen minority to cross the border
Doris Lessing: Acclaimed novelist was kept under MI5 observation for 18 years, newly released papers show

'A subversive brothel keeper and Communist'

Acclaimed novelist Doris Lessing was kept under MI5 observation for 18 years, newly released papers show
Big Blue Live: BBC's Springwatch offshoot swaps back gardens for California's Monterey Bay

BBC heads to the Californian coast

The Big Blue Live crew is preparing for the first of three episodes on Sunday night, filming from boats, planes and an aquarium studio
Austin Bidwell: The Victorian fraudster who shook the Bank of England with the most daring forgery the world had known

Victorian fraudster who shook the Bank of England

Conman Austin Bidwell. was a heartless cad who carried out the most daring forgery the world had known
Car hacking scandal: Security designed to stop thieves hot-wiring almost every modern motor has been cracked

Car hacking scandal

Security designed to stop thieves hot-wiring almost every modern motor has been cracked
10 best placemats

Take your seat: 10 best placemats

Protect your table and dine in style with a bold new accessory