Tag: density

Posted in Science & Nature

The Titanic Door Debacle

Posted on by Jinavie

One of the most famous arguments in popular culture history is why at the end of the movie Titanic, Jack had to die when it clearly looked like there was enough space for both him and Rose to lie on the floating door.

Since the movie’s release in 1997, countless fans have lamented how the birds-eye view shows that both people could have laid side by side to fit on the door.

But alas, science is an unforgiving mistress and it has since been shown that it would have been physically impossible for the two lovers to survive together on that makeshift raft (which was a wooden panel, not a door).

The film actually shows Jack trying to get on to the panel, when it tilts and starts to submerge, nearly flicking Rose off. Jack realises that the panel would not support both of them and chooses to only keep his upper body on it, while fending off other survivors trying to latch on. Unfortunately, this is not enough to keep him alive as he quickly succumbs to hypothermia and sinks to the bottom of the ocean.

The important question is not whether the two would fit on the panel, but whether the panel is buoyant enough to support both of them.

Buoyancy is the force that makes things float in liquids. It depends on the volume of the floating object and the density of the liquid it floats in. If buoyancy is greater than the pull of gravity, the object floats.

Now, let us calculate how much buoyancy we would need to keep the panel, Rose and Jack afloat.

For the two to survive, no more than the door itself can be submerged, keeping the bodies above water level. Therefore, the volume of the submerged object is the volume of the raft. Estimating from stills from the film and Kate Winslet’s height, we can calculate the raft as being roughly 1.85m x 0.95m x 0.15m, or 0.264m³.

Ergo, the buoyancy of the panel would be Volume x Density of ice cold salt water x force of gravity = 0.264m³ x 1000kg/m³ x 9.8m/s² = 2587N (Newtons). If more than 2587N of weight is placed on top (including the panel itself), it would sink.

At the time of the production of Titanic, the estimated weight of Kate Winslet and Leonardo DiCaprio were around 549N and 686N respectively (note that in physics, weight is mass times the acceleration of gravity, measured in Newtons).

Subtracting these values from 2587 leaves us with 1352N free for the panel. Since we know the volume of the panel, as long as we know what wood it was made out of, we can find the density and calculate the final weight.

Three types of wood were commonly used on the Titanic: teak, oak and pine. The densities of these woods are 980kg/m³, 770kg/m³ and 420kg/m³ respectively, meaning that the door would be 2535N if it was made of teak, 1992N for oak and 1087N for pine.

Therefore, the maths show that for the two to have a snowball’s chance in hell of surviving together on the panel, it had to be made of pine. Teak and oak would have been too heavy.

This is where the final key becomes relevant: the wooden panel was likely made of oak.

The Maritime Museum of the Atlantic in Halifax, Nova Scotia, holds the largest piece of debris from the actual wreckage of RMS Titanic. If you look at this wooden panel (from above a doorframe), it looks remarkably similar to the wooden panel that Rose survives on. In fact, a replica of this debris was used for the filming of the film. The material of the actual wooden panel? Oak.

If the panel was made out of oak, it could only hold Rose, as 1992 + 549 = 2541N, which is just enough for Rose to stay afloat above the water level.

And there you have it. Not even the power of love can overcome the cold-hearted, brutal law of the universe that is science.

Posted in Science & Nature

Tip Of The Iceberg

Posted on by Jinavie

Icebergs are deceptive things. You may see a small bump above the ocean surface, but beneath the surface hides a massive block of ice. Using Archimedes’ principle of buoyancy, we can calculate exactly what proportion of an iceberg lies under the surface. Pure ice has a density of about 920 kg/m³ and sea water has a density of 1025 kg/m³. Ergo, we can calculate that about 10% of the volume of an iceberg is above water. Therefore, whatever you see above the surface, there is nine times the volume hiding beneath it.

“Tip of the iceberg” is a useful metaphor in describing many things. Our base instinct is to believe what we see at first glance. We rely on first impressions, we judge books on their covers and we tend to believe headlines before reading the full text of an article.

Although this is a useful way to process massive amounts of information that we are exposed to every day, it is certainly a flawed method because not only can we miss a vast quantity of information, also easily misinterpret or misunderstand things.

Take mental health for example. Because we cannot read minds, we take clues from people’s expressions, body language and what they tell us to gauge what is happening in their minds and hearts. We are reasonably good at gauging this, so we often make assumptions based on surface information.

We might assume our friend is happy because they are smiling, or that a couple’s marriage is harmonious because of cute photos on their social media. Conversely, we might assume that a stranger is rude to us because they are terrible people.

But the smiling friend may be suffering crippling anxiety and depression. The happy-looking couple may be at the brink of divorce because of relationship problems. The rude stranger may have lost a loved one just the day before. Things are not always what they seem and it makes an incredible difference to have the insight to see past the surface.

Another lesson to learn from the tip of the iceberg is that when we encounter a problem – whether it be with another person or even within ourselves – we should ask the question of what lies beneath. The problem we notice may just be the tip, with 90% of the issues hidden from plain sight.

For example, if you feel tense and easily triggered often, perhaps it is worth looking under the hood and going on an introspective journey to discover what past experiences and traumas may have caused the insecurities. If you keep feeling victimised, attacked or sensitive, examine what story your subconscious is telling you and try to correct the narrative, being the agent of your own story.

Avoid the fate of the RMS Titanic: look beyond the visible tip of the iceberg and be aware of the entire problem. You will be surprised how it changes your perspective of the world, the people you interact with and how you feel about yourself.

Image credit: https://www.smbc-comics.com/comic/hubris

Posted in Science & Nature

Lava

Posted on by Jinavie

Death by lava is an often-used trope in films, most likely because of its slow, dramatic nature and the poetic beauty of being engulfed by liquid fire. But unfortunately as with so many things in the film world, most movie scenes depicting a person slowly sinking into lava until they are completely submerged is completely unscientific.

Lava is essentially molten rock. Just as ice and rock have different densities (try smashing two together for comparison), water and lava have completely different densities. In fact, lava is just over three times denser than water and somewhere between 100,000 to 1,000,000 times thicker (viscosity). The extremely high viscosity is why lava does not flow well, much like thick syrup and pitch. Density matters because less dense objects float when placed in a denser substance. Human beings are slightly denser than water (1010kg/m³ vs 1000kg/m³), meaning we can float if we have enough air in our lungs to provide the buoyancy. However, we are far less dense than molten lava. Even if we were as dense as lava, the extreme viscosity would make it very difficult for us to sink as the lava would not flow away from you that quickly. Ergo, if you were thrown into a pool of lava, you would not sink into a dramatic death.

Instead, you would most likely experience an even more horrific death as you stay afloat on the lava, as the surface of your body touching the lava is burned. Typical lava is between 1100~1200°C – well beyond the ignition point of human flesh. Not only will the skin, fat and muscle melt and peel away, but it will light up like a wick. The flame will soon cover the entire person and they will not only burn, but combust. Ultimately, only ash and completely dried up bone will be left floating on the lava, which will also end up igniting eventually.

Unfortunately, objects made of material such as steel and most other metals are denser than lava. This means that the Terminator would actually sink as dramatically as it did in the ending of Terminator 2 if he were to descend into a pool of lava.

(NB: It is important to note that in the movie, he descends into a vat of molten steel, not lava. Therefore, the accuracy of that scene hinges on whether the Terminator is made of a metal alloy denser than molten steel)