How do huge ships stay afloat

They do that with a little help from the principles of density and buoyancy. Cruise ships can weigh upwards of 71, tons 65, tonnes. They displace the equivalent amount of water when they press down on the ocean, which meanwhile pushes up and keeps the ship afloat, or buoyant. That's why when engineers talk about how heavy a ship is, you'll hear them talk about displacement instead of weight. To keep from sinking, the cruise ship has to displace its weight in water before it's submerged.

That's a lot easier to do if the cruise ship is constructed in a way so that it's less dense than the water below it. Think of it as the difference between dropping a bowling ball in the water and trying to submerge a beach ball. The bowling ball can't displace enough water before it's submerged, so it sinks. The beach ball does the opposite and floats. Engineers help ships to achieve buoyancy by choosing lightweight, sturdy materials and dispersing the weight of the ship across the hull.

The hull , or body of the ship below the main deck, is typically very wide and has a deep base line , or bottom. You can unsubscribe at any time. More info. MSC Cruises has announced four new ships that are to hold a record-breaking 6, passengers. Royal Caribbean's Harmony of the Seas is the largest on the ocean, at a staggering , tonnes. So why do ocean giants like this stay afloat on the water when a tiny stone would sink to the bottom in an instant? Everything on Earth, whether on the surface or under water, has the weight of everything higher up pushing down on it.

Yes, right now as you read this, the weight of all of the air above you, right up to the top of the atmosphere, is pushing down and in on you. The resulting force is about Water is relatively heavy — go down just 30 feet and the weight of the water per square inch on your body will equal the weight of the hundreds of miles of air above you. The answer is simply that the water below you is pushing up.

There you are, underneath the surface in a swimming pool. Water wants to be where you are — your body has displaced a whole lot of it.

If you suddenly disappeared, water would rush in to fill the space. Additionally, those lightweight materials need to be used in a design which allows them to displace their weight in water before they submerge. Most of that design is implemented in the hull which is the body or shell of the ship which sits below the main deck and pushes the water out of the way and allows the vessel to float.

Through years of trial and error, engineers have found making the hull rounded, wide and deep helps disperse the weight of the ship across the body of the ship. Large cruise ship hulls are shaped like the letter "U. Just staying afloat and cruising smoothly isn't enough; a cruise liner's hull design must also protect the people inside against obstacles like icebergs, reefs and sandbars which could rip apart the ship's outer layers.

To prevent a major catastrophe , shipbuilders typically use extra-strength steel and build their ships with double hulls meaning one hull inside the other as an extra precaution. Cruise ships also have bulkheads which can help them stay afloat in case of major damage.

These watertight dividers are installed throughout the interior of a ship and can be closed to seal out water rushing in through a damaged hull. Limiting the water inflow can ultimately keep the ship from flooding and sinking. As of , the biggest cruise ship in the world measures about feet tall, and even the average cruise ships still have impressive height. So what keeps them from tipping over in the water? The answer is, again, in the hull design. First, you must understand the difference between the ship's center of gravity and its center of buoyancy.

According to Engineering Toolbox , a ship's center of gravity the central focus point for gravity's downward push cannot be changed.