My Physics in Film Blog

Without a doubt superhero movies are my favorite, and Iron Man is my favorite hero. That made this one of the harder assignments for me. The physics in the movie weren’t too bad. Most things were based on the same laws we have to deal with in our world. Apparently the movie world has a car with a drive train that shifts from rear to front wheel drive and has a bumper and quarter panels that are directly connected to the frame of the car. (Watch the car that Stane throws at Stark during their battle on the street.) They also seem to have no requirements for crash testing their Hydrogen powered buses. (Watch how flimsy the sides are) Other than that once you get past the idea of a flying suit of amor the rest pretty much makes sense and fall into place.

How does it work?

Super Strength.

This power is a must because the complete setup (man and armor) weighs 425 pounds minimum, more based on armor configurations. Tony has to be able to move in the armor with speed and grace so hydraulics are out of the question. The tubes shown in the movie are fiber optic conduits and temperature regulation arrays. The ARC reactor provides the power to the repulsor tech. Perhaps Iron Man doesn’t so much lift things but uses magnetic fields to push them away. In this way he could deliver a devastating punch by changing the polarity of various armor parts (fist and shoulder) to make the repel each other. The reactor power seems to be virtually unlimited so the magnetic fields wouldn’t have to be limited to a certain size. It would also explain why cars picked up by the bumper don’t fall apart. Of course it would take a lot of computing power to constantly adjust all those parameters, but we are already doing it with the latest generation of fighter planes (F-16, F-18, F-22, & F-35), and we all know Tony Stark is much smarter than we are. So by using electricity and magnetism Iron Man can move and perform great feats of strength. Try not to think about how he lifts large boulders or other nonmagnetic things. There must also be a lot of shielding in the armor because that amount of electromagnetic energy would surely disable the on board computers required to run the suit.

Damage Resistance.

While Stark is just a regular man the armor is invulnerable (or close to it). If the laws of physics were really in force then he would be turned to a liquefied paste inside the armor. The forces he experiences while flying ( high G maneuvers), impact from artillery and missiles, along with the fists, feet, and falls that are a part of life as Iron Man should still be felt by the man inside the armor. Inertia still has to be dealt with along with momentum. The affects of small arms fire through some types of artillery could be reduced through the use of repulsor technology. An electromagnetic field could be used to slow the projectile and reduce its momentum prior to impact. Another option is to use an electric reactive armor technique. You can read about it here: http://en.wikipedia.org/wiki/Reactive_armor#Electric_reactive_armour That may also explain why there is a layer of armor under the red and gold layers. When the armor decelerates from supersonic speed to a dead stop the body inside wants to keep going. Internal organs should hemorrhage and death should occur. That’s why the armor employs the same inertial dampeners used on Star Trek.

Flight.

How does Iron Man fly? Since there are no flames or heat coming from the boots they must use the same repulsor technology as the hand units. The question is what are they repelling? I can understand them working in the test lab but not in the open sky. What do they push against to provide propulsion? Maybe they just push air out with great force but you never see any intakes for air. You do in the comics but not in the movie. At best he should be able to hover like in the test lab or launch himself like a cannonball. Even that would depend on the strength of the platform he was launching from. It could be that he interacts with the electromagnetic field of the planet itself to achieve flight. This is one we just have to press the “I believe” button for.

So as you can see with the exception of flight all these powers are easily explainable. Much of the technology is already being used or tested. (on a much smaller scale in most cases) All we need now is a 12 Gigawatt ARC reactor and an inertial dampener and I’m on my way… Hey, it could happen!

At the end of the movie”Contact” we find Ellie has only disappeared for a fraction of a second to a few seconds at most. This isn’t a problem except for the fact that her personal log recorder has 18 hours of static on it. The immutable laws of physics say that this cannot be possible. With the effects of time dilation, more time has to have passed on Earth that inside the traveling chair apparatus. If we assume the pod travels at 0.99c and discount any time actually spent on the planet, then Ellie spent a total of 18 hours just traveling. Nine hours at 0.99c turns out to be 9.6228 E 12 meters or 0.0010171 light years away. This is well short of the 25 light year distance to Vega but we’ll use it anyway to prove the problem.

An eighteen hour proper time interval for Ellie traveling at 0.99c would equal 127 hours on Earth or 5.3166 days not a few seconds. Remember we still haven’t accounted for the time she actually spends on Vega. Looks like Hollywood got the twin paradox completely backwards. Normally I wouldn’t be surprised but the rest of this movie was done really well from a physics standpoint.

How would I fix this? First traveling 50 light years at 0.999c will take 50.0485 years as measured by clocks on Earth and 2.23768 years by Ellie’s clock. During the trip the pod and Ellie obviously must be must be more energy than matter so the recorder would not register anything including the passage of time. The eighteen hours of static would just be the time she spent on Vega which the aliens would have conveniently erased. After the pod disappeared the government would have put out a cover story saying Ellie died. The device would have been disassembled and rebuilt in a secret location just in case (Those government scientists understand time dilation). In 50 years Ellie would return and immediately be sequestered by the Feds. Most of her friends and associates would be dead. The world has changed markedly due to the technological advances based on the original pod transport design. There is now one world government, and Ellie has a headstone in Arlington National Cemetery next to David Drumlin. She has been raised to hero status across the globe. Palmer Joss has lost his faith and is waiting to die. Since she has no proof of her trip she is kept from the public and only a select few even know she is alive. Fearing the damage her return would cause Ellie agrees to Take care of Palmer until he dies and never tell anyone her story. The movie ends with a young Zefram Cochrane learning about the IMC at Ellie Arroway Elementary school and vowing to figure out how to warp space and time.

I’m a big fan of the Star Trek franchise, so I had seen this film when it was in the theaters. I thought it was one of the more entertaining films but not really a true Star Trek film. The film is more of a human interest story. There is not much technology or space travel involved since the majority of the film takes place in the late 1980’s. But the tech developed for the franchise is key to making the series work.

Without the warp engines none of these stories would be possible. Even if the Enterprise could travel at the speed of light. The original 5 year mission would not be enough time for a round trip to our nearest neighboring star system, Proxima Centauri. Since we are not even close to being able to obtain 0.25 c it would take too long to travel across our own star system much less visit others. No one wants to spend an hour every week just watching a ship move through the vast emptiness of space. Being able to warp time and space allows them to move vast distances in an incredibly short period of time. This allows for different scenarios and locations each week which makes for a more interesting television show. Evidently the warp engines also negate the effects of time dilation also. Without warp engines when 5 years had passed for the crew of the Enterprise much more would have passed on Earth. How do you explain returning from your first trip in your state of the art ship only to find it is hundreds of years behind current technology? I hope Starfleet keeps good records since every time Kirk and crew returned to Earth most if not all of the people they left behind would be dead. Some of the people they would report to would not have been born when the Enterprise left Earth. The problem with warp engines is that nothing can travel faster than the speed of light. Even if we could properly mix matter and antimatter for a sustainable reaction we would still be limited to the physical laws of this universe. That is why the show’s creators say the engines create a warp bubble and they travel through subspace where our laws do not apply. So much for that whole thing about laws being the same for any inertial reference frame.

The second technology invented for the franchise was the transporter. This was more of a budgetary device. Without it there would be a need for additional sets and scenes with either shuttle craft landing and docking or a method for the Enterprise to fly in an atmosphere (wings). The saucer section is designed to land only in an emergency. I’m not sure how it generates lift since all it has are impulse engines and maneuvering thrusters. The original shuttlecraft looked like a flying brick with no aerodynamic properties at all. The process of beaming down to a planet gets us past all of these problems. In theory in seems based in real world physics. Matter is converted to energy and the energy is transferred to a receiver at the speed of light. The energy is then reintegrated back into matter. E=mc² seems to explain this as long as there is no energy loss during the transfer. The problem with the transporter is that we have no way to keep track of the structure being disassembled. How much computing power would be needed to map a persons structure down to the subatomic level and then rebuild that structure on the other end of the transmission. Even if we had the computer technology we don’t know how to do that. If things aren’t put together exactly right you run the risk of killing or maiming the person or material you are moving. (Think Jeff Goldblum in The Fly) It’s no wonder that Dr. McCoy doesn’t like the transporter! We can convert matter into energy but we can’t currently reintegrate that matter to its original form.

While these two technologies are not possible, Star Trek has inspired many others that are common today. Cell phones, Touch screens, flat panel displays, PDAs, bio beds, online encyclopedias, and clothes without pockets to name a few.

I am always intrigued by why people do the things they do. It seems that no matter what type of people we are, there are common factors that drive us. Throughout the course of this movie people begin to question their actions and their motivations.

My time in the military made it easier to understands General Groves’ initial desire to build the bomb. If you must fight then you want the best and most powerful weapons available. The best way to keep soldiers alive is to not have wars. If war is already in progress or all diplomatic channels have been exhausted, then end it decisively and as quickly as possible. From a military standpoint victory is the only option available and Groves must do whatever it takes to accomplish it. Many people, including some of the scientists on the project have a really hard time understanding this point of view. The truth is, in war people die, or are permanently injured. If it is not the enemy then it is you and/or yours that are the victims. Most military personnel don’t enjoy killing, but they are trained to be as efficient as possible in accomplishing that task. Any weapon or advantage that ensures more of your guys come home whole, or never have to go must be pursued. This is Groves’ initial motivation for completing the project. If he can’t be on the front lines fighting he will do all that he can to give his country the largest advantage any country has ever had. And he must do it before anyone else does. It’s his job and he feels it is the right thing to do.

Many of the scientists start off the project as if it is a puzzle to be solved. They are getting the ultimate setup for a scientist: an unlimited budget, a free forum to exchange ideas, and all the tools required. This combination has them giddy with excitement. They have been given the opportunity to do something that has never been done before. It is now just a matter of attacking the problem and proving how smart they are. Here again we see people just doing their best to assist their countries.

Just because you can do something doesn’t mean you should do it. As the novelty of the new situation wears off and the pressure from the military sets in the scientists begin to ask themselves if they should build the device. I don’t think this becomes a problem until they realize they can actually accomplish their goal. But now it is too late. They no longer have the freedom to say no. There is a huge difference in the theoretical and the actual. There is no remorse associated with theory. Theories if found to be mistaken can be corrected. Lives, once taken cannot be returned. Because they are not trained to wage war the scientists cannot see things from a military perspective.

As the project progressed it seemed as if both Groves and Oppenheimer were more concerned with how they would be viewed if they didn’t deliver. They move to a more personal motivation. The other motivations are still there but now their reputations are at stake. It seems to me that both men developed something of a God complex. I’m not surprised. Groves sees himself in the position dictating life and death with the bomb. Oppenheimer sees himself controlling the fundamental forces of the atom. Before this project both of these areas belonged solely to God.

My feelings on nuclear power are based on more than 20 years working in, or around a nuclear power plant. Because I have spent so much time in the field it is hard for me to feel the fear and mistrust that so many others do. While I do not fear nuclear power, I do have a healthy respect for the potential dangers associated with it. That being said, I think the benefits of nuclear power outweigh the dangers associated with it.

The pros of nuclear power are easy to see. As the demand for energy continues to grow we must find a way to continue to meet those needs. Nuclear power provides a way to meet our energy needs without increasing our dependence on foreign oil or deface our own country with strip mining or ugly oil derricks. Energy independence is a growing concern and all possible sources of energy should be considered. Until we can

Where do I begin? It is easy to see why this movie is rated the worst physics movie ever. The non stop stream of false representations and outright ignorance of engineering and scientific principles is offensive at best.

The opening scenes.

Seems strange that the watch stops before the guy feels anything with his pacemaker. In fact he never seems to notice a problem with his heart rate at all. No heart attack no obvious increase or decrease in heart rate he just passes out. Maybe his pacemaker was controlling the oxygen he was receiving.

While it is always good to see birds crashing into things, I have some issues with their conservation of momentum and energy here.

The Shuttle landing.

Why is the shuttle landing in California? I guess the change in the EM field has already affected the weather in Florida where the shuttle normally lands. Not sure why they have the coordinates for the LA aqueduct system in the shuttle good thing they did though. The Shuttle pretty much flies like a brick on approach. How did they make such a large course change? How did the landing gear retract with the full weight of the shuttle on it?

The ship

Unobtainium? Nuff said!

If unobtainium converts heat and pressure to energy why is the mouse unharmed? Where did the energy go?

There must be some type of voltage regulation inherent in the miracle metal otherwise how can they just attach power cables to the hull and power the ship.

How can they move around in the ship? The internal pressure must be equal to the external pressure to keep from crushing the ship.

What type of reactor powers Virgil? Most reactors don’t use weapons grade plutonium. Enriched Uranium 235 is a much more likely choice but would not add much to the explosions as the safety features would have shut it down.

How is the image on the monitor transmitted back to the ship? Josh says its like a CAT scan but where is the receiver? There must be a lot of radiation given off to penetrate 3 feet of lead 50 yards away. The guy walking through the beam behind the lead is probably dead already.

How does the ship turn? What is the propulsion method? Trains follow tracks but there are no tracks here. It must be based on pushing material out for propulsion because when they hit the void they have no control.

The Story

If the reactor core is hot enough to melt the chain and burn though Josh’s gloves why isn’t he wearing his helmet? The air in there must be scorching his lungs, but it doesn’t matter as he will soon be dead from acute radiation sickness. Why doesn’t it melt through the deck grating? Maybe just the handles are hot.

The moderator (control rods) are part of the core (fuel assembly). Why place a neutron absorber next to a bomb in hopes of increasing the rate of fission?

How can the San Francisco bay boil? A body of water that large should be able to dissipate the heat with maybe only a rise of a few degrees at most.

The Golden gate bridge begins to melt but not the cars? Plastic and aluminum have lower melting points than steel.

If electrical current takes the shortest path why does the lightning run down the middle of the street in Rome?

With that much static electricity in the air you would think someone’s hair would be standing up.

How does a plastic television case discharge such a large electric shock?

What kind of torch are they using to cut the crystal? The torch temperature would be less than the surrounding temperature if it is an oxygen based flame.

Why didn’t Iverson get vaporized when his suit was punctured? Where did all that kinetic energy go? Assuming the suit remained intact due to being made of unobtainium, the difference in pressure and temperature should have compressed and flash fried him inside the suit.

I’d like to see the calculations for the amount of torque needed to jump start the core.

Are they implying that scuba divers made the connections to lift Virgil? I hope not!! 800 feet is too deep for scuba gear.

Since unobtainium converts heat and pressure to energy the active sonar must have located it by its lack of return.

The ocean floor would have caused problems getting an accurate fix using active sonar. They would have been better off listening for the hum of machinery or the ultrasonics using passive sonar.

Having spent a lot of time in a cramped tube with a nuclear reactor made this movie incredibly hard to watch. The writers take advantage of the fact that most people have no clue as the the truth about these things. While this list is not all inclusive it is more than enough to show why this movie is rotten to “The Core”.

Throwing nuclear warheads at the problem seems like a good idea at first but there must be another way to solve this problem without the use of these weapons. I have decided to adjust the asteroid’s trajectory through the use of existing (or close to existing) NASA technology.

Assumptions:

The asteroid will be intercepted at twice the distance between the earth and the Moon: 7.69×10⁸ m

Diameter of asteroid: 5 km Asteroid velocity: 1.1 x 10⁴ m/s

Density of asteroid: 5500 kg/m³ Diameter of the Earth: 1.3 x 10⁷ m (add 25 km for atmosphere)

We must also assume we can actually land on the asteroid. NASA is currently investigating The Orion Asteroid Mission which will involve landing on a near Earth asteroid. We have to take some liberties here as the proposed Altair lander will not have the load capacity required.

The Plan

My plan is to intercept the asteroid and apply enough force to slightly change its direction. Based on the radius of Earth and preventing damage to the atmosphere we need a minimum change of 6.6 x10⁶ m on the y axis. This distance will require a course change of 0.492°. This will require a velocity in the y-axis of 94.4 m/s. The calculated volume and mass of a spherical shaped asteroid with a diameter of 5km and density of 5500kg/m³ are 6.54 x10¹⁰ m³ and 3.60 x 10¹⁴ kg respectively. There is no way we can do this. Time to change the assumptions.

New Assumptions

Assuming the movie’s constant velocity of 22,000 mph, 18 days to impact, the distance from Earth to Moon of 3.844 x 10⁸ m, and the required conversion factors; I calculate the asteroid is a distance of 39.78 times the distance from Earth to the Moon or 1.53 x 10¹⁰ m away. Since we cannot change the velocity of 1.1 x 10⁴ m/s we only have 16.10 days to impact. We will initiate course change no later than impact minus 8.09 days (7.69 x 10⁹ m); the zero barrier. Since we cannot currently be ready and travel this distance in 8 days, I will assume this event doesn’t occur until sometime after 2020. By this time the Ares V rocket and NASA’s Project Constellation should be operational. I also assume we will have a continuous presence in low earth orbit for launching spacecraft.

Diameter of asteroid: 2 km Asteroid velocity: 1.1 x 10⁴ m/s

Density of asteroid: 5500 kg/m³ Diameter of the Earth: 1.3 x 10⁷ m (add 25 km for atmosphere)

Thrust of Ares V 1^st Stage: 19.8 MN (6 RS-68 engines @ 3.3 MN each)

Rocket firing time: 5 minutes Specific Impulse (I_sp) RS-68: 4 kN∙ s /kg

The calculated volume and mass of a spherical shaped asteroid with a diameter of 2km and density of 5500kg/m³ are 4.19 x10⁹ m³ and 2.30 x 10¹³ kg respectively.

Calculations

Required course change: Tan θ = 6.60 x 10⁶ m / 7.69 x 10⁹ m = 8.58 x 10^-4

θ = Tan^-1 (8.58 x 10^-4) = 0.0492°

Required velocity y-axis (v_y): Tan θ = v_y / 1.1 x 10⁴ m/s

v_y = Tan θ x (1.1 x 10⁴ m/s) = (8.58 x 10^-4 ) x (1.1 x 10⁴ m/s) = 9.44 m/s

Required Acceleration y-axis (a): v_f = v₀ +at so, a = v_f / t (when v₀ = 0 as it does in this case)

a = (9.44 m/s) / (300 s) = 0.0315 m/s²

Required Thrust: F = ma

F = ( 2.30 x 10¹³ kg)(0.0315 m/s²) = 7.24 x 10¹¹ N = 7.24 x 10⁵ MN

Conclusions

Based on the calculated thrust for the Ares V 1^st Stage we will need 36565.7 of them to generate the required force. Even if we had this many rockets manufactured it is highly doubtful they could be transported, attached, and fired 5 minutes prior to the zero barrier. Switching to the current solid rocket boosters (12.5 MN) would take 57920 boosters but they cannot last for 5 minutes. If we substitute the RS-68 with the Soviet Union’s RD-170 (47.322 MN) it will require 15299.44 rockets; which is still out of the question.

Based on Specific Impulse (I_sp) RS-68 a 5 minute burn will require 9.05 x 10⁹ kg of fuel for each rocket.

(24 kN∙ s /kg)(MN/1000kN)(1/7.24 x 10⁵ MN) = 3.315 x 10^-8 s/kg (per rocket)

(300 s)(kg / 3.315 x 10^-8 s) = 9.05 x 10⁹ kg (per rocket)

For a total of 3.31 x 10¹⁴ kg of fuel.

This seemed like a good plan at first but until we develop stronger rocket engines it is just not possible. Nuclear weapons and drills don’t seem quite as crazy now. The largest nuclear weapon was 57 megatons but can be modified for a yield of 100 megatons. Unless it is a shaped charge most of the force will be wasted, so we better use a couple of them.  Even the we have to hope none of the pieces are too large.  We could end up with multiple impacts that collectively do the same amount of damage. I guess that’s why they call it Armageddon. It is the end of days at our current level of technology.

My new plan: Pray!

Apparently John Kruger has the ability to erase the immutable laws of physics along with the identities of his Witsec clients. The laws of conservation of momentum and conservation of energy were broken on several occasions throughout this film. While I don’t have the time to deal with things like explosive decompression in an airplane, or how one can perform high altitude drops with no protective gear. I will visit the physics (or lack thereof) of the rail gun used in the movie “Eraser.”

The first analysis deals with the conservation of momentum between the shooter and the projectile. The following assumptions were made:

Mass of shooter = 90kg

Mass of projectile= 0.003 kg (Slightly smaller than a standard M-16 round.)

Using equation 12.2 from the book and a speed of 0.9c the calculated momentum of the projectile is 1854900 N∙s. Since momentum must be conserved this means the shooter must have a momentum of -1854900 N∙s. If the shooter has a mass of 90 kg then his velocity will be 20610 m/s in the opposite direction of the projectile. This obviously can’t be right because the shooter doesn’t move and in some cases continues to move forward.

If we try the calculation again using the standard (low speed) momentum calculation it looks like this:

P = mv

P = 0.003 kg (119916000 m/s)

P = 359748 N

With this momentum the velocity of the shooter is as follows:

V_shooter = (P_shooter) / (m_shooter)

V_shooter = (359748 N) / ( 90 kg)

V_shooter = 3997.2 m/s in the opposite direction of the projectile

This velocity equals 8943 mph. The shooter is unaffected so it seems obvious that momentum is not conserved and Hollywood has taken advantage of the reality warping powers it possesses.

What about the victim, Darryl?

Assuming he is 185 lbs (83.9 kg) and using the movie footage we can calculate his velocity immediately prior to impact with the wall, his acceleration due to the projectile, and the force associated with this acceleration.

He seems to travel about 20 feet (6.096 m) over 1.11 seconds.

d = ½ (v₀ + v_f) ∆t

v_f = (2d / ∆t) – v₀

v_f = ( (2)(6.096 m) /1.11 s) – 0 m/s

v_f = 10.984 m/s

This is about 24.57 mph which seems consistent with the damage done to the wall, but where’s the projectile? Since the wall doesn’t explode like everything else hit by one of these projectiles it must still be in Darryl. If so his velocity should be as follows:

V_Darryl = (P_projectile) / (m_Darryl)

V_Darryl = (359748 N) / ( 83.9 kg)

V_Darryl = 4287.8 m/s in the same direction as the projectile

This velocity equals 9593.6 mph. Darryl obviously isn’t moving this fast and he appears to be mostly intact when he hits the wall so all of the projectile’s energy was not transferred to him. Since energy must be conserved I can only assume it is in some type of holding area or transferred for one of the later fantastic explosions.

Things that make me go“Hmmmm?”

1. In one scene we see gases being ejected from the end of the rail gun barrel and perpendicular to it also. Since no gunpowder is used I guess the gas can only be vaporized aluminum. That may explain why the projectile is so much smaller than the barrel of the gun.
2. Since the heat of vaporization for aluminum is 294 KJ/mol just how much power is the portable battery actually putting out?
3. If the battery pack puts out enough current to accelerate the projectile to near the speed of light, and in the process vaporize some aluminum, for multiple shots, but remain light enough to be carried easily by one man; why is Cyrez making weapons? This type of battery technology would make much more money and could be sold on the open market. Goodbye oil dependence, hello high speed electric cars.

The first scene I looked at was the use of the starboard bow thruster to change the cruise ship’s course. I wanted to find out how much thrust was needed to overcome the the momentum of the ship.