A friend and I have been having an ongoing debate for years. We were at a pub on a wharf, watching shipping container ships and cruise ships come into dock, and he posed the question. With no wind, no waves, perfect conditions, could he move the ship at all?
In: Planetary Science
Assuming drag does not COMPLETELY stop the ship, which I feel is a reasonable assumption given that ships are built to move, then yes. Technically. It would be *mind bogglingly slow*, but yes. The ship would have so much inertia that you’d probably need scientific instruments to measure its movement, but there is no such thing as an immoveable object, so a very small force on a very big object produces a very very tiny acceleration.
Ideally, you’d want ropes and one hell of a pully system with like a 1,000,000:1 mechanical advantage. You’d have to pull a rope for a few miles to move the ship a couple of inches, but you could definitely do it.
Not likely.
Water still has friction resistance that needs to be overcome. Think of it this way, if you replaced the water with honey, would you expect to move it? The water moves very easily compared to honey, but still has friction. You have to push the water out of the way in the front, overcome the drag on the sides/bottom, and over come the suction to the rear as the ship moves forward and leaves a gap (very, very, tiny) the water has to move in to fill.
If you put the ship into space with no resistive medium you would be able to start it moving very, very, very slowly.
In theory you should be able to do this. Although it would take quite a bit of effort until you even got a noticeable movement. This would be similar to how people demonstrate pulling loaded trains, but a ship would have a lot more momentum but lower resting resistance. Top Gear also did something similar to this by pulling a 13,000 tonne freight ship with a small Citroen C3 compact car. The issues they had with the tiny bit of breeze shows that this would most likely be impossible to do in practice with a human but in theory there is nothing preventing it from being done in absolutely ideal conditions.
Drag force scales with velocity at all speeds, so if the ship is *completely* stationary (just to be clear, this is a “spherical cow in vacuum” kind of scenario, the ship will never be that still IRL), the drag is zero and you can push the ship. Reeeaaaaallyyyy slowly, though.
Assuming no water resistance
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150.000.000kg vs 75kg to start moving this at 1m/s it will take 150m/75=2.000.000 times the energy as you not pushing this weight.
On top of that you have to push the water in front of the ship away… So yeah no measurable movement at all.
Without wind, yes. You only have to overcome inertia and viscous drag which can be small if you propose acceleration/velocity to be really small.
With wind in picture, hell no if you have to fight against it.
Yes, it would. If you throw a ball to someone, that action would have a small but calculable change in the earth’s rotation. It would be vanishingly small, but real.
The same with the boat. It would be extremely tiny, but the force you applied would have a calculable and measurable impact on the boat.
Any distance? Of course. If it’s completely stationary it could be moved a few planc lengths by breathing on it a little bit, probably.
Yes. I grew up in a Navy town, and in the 1980’s you could get close to the ships. If you lean on one, they very very slowly start to move after a few seconds. I remember seeing someone push the USS Iowa when it was opened for tours after it was recommissioned. The drag equals out the force at a very low speed, but given enough time, a ship weighing thousands of tons could be moved a significant distance by single person.
There’s actually a competition in strongman circles called the [boat pull](https://youtu.be/507YvqWktTc?si=G5I5RVCxWFcUdPTn). I believe the boat they use is around 13 tons, which isn’t that big of a boat compared to the thousands of tons beheamoths like cargo and military vessels (especially big military ships as they’re armored, which significantly increases mass, thus friction from the water. Note that these dudes in the video are professional strongmen, with a honed technique for the boat pull competition. Note that a lot of power is coming from them pushing their legs against a solid wall, and not by standing freely or using their arms. They’re using *a lot* of energy to move that relatively small boat (compared to a container ship), and those dudes are *professionals*. If they have to exert themselves that hard for a 13 ton boat, they’re hopelessly outmatched against anything that’s multitudes larger, heavier, and displaces more water thus has more friction to combat.
This is anecdotal, but when I was in Boy Scouts, we did a trip called “Sea Base” at which you sail about the Florida Keys on (in our case) 40 ft. schooners. I, being the strongest in the group (sorry to brag) was tasked with making sure the boat didn’t hit the dock while we docked. My god, it was one of the most exhausting things I had ever done – and I was regularly weight training at the time. Every ounce of my strength was spent trying to keep a little ol 40ft. schooner from bumping the dock – and it still hit. Despite moving at a snails pace, it hit with enough force that the wooden decking on the aft started to compress and pop up.
Boats, yo. They’re heavy.
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