The world's largest oil tanker comes in at about 565000kg so if there were two of these leviathans 100m appart at sea (calm, no strong currents ) would there be a noticable attraction between them? I calculated a force of about 0.002N.

not really. 0.002N would be totally swamped by forces from the waves and wind. although, if they were in a massive tank with no waves or wind then they would drift together. It would work better in a vacuum.

If they were 1000m apart. Would they drift faster towards each other?

[math] F_{g}= G\frac{m_1M_2}{r^2} [/math]

 

Fg is the force due to gravity.

MrGamma, if they were a trillion lightyears apart, assuming no other forces causing motion, they would drift together.

If they were 1000m apart. Would they drift faster towards each other?

 

No. Since they would be ten times farther apart, and force of gravity varies with the square of the distance between objects, the force would be 1/100th as strong, or (apparently) about 0.00002N. They would start out accelerating 1/100th as quickly.

There is some evidence the following post is true...

 

There's a bit on the wp 'talk' page about it...

 

http://en.wikipedia.org/?title=Talk:Casimir_effect#ships

 

I can clearly see how it might be the case. But cannot remember whether I was told it in a lecture or just in passing...

 

There will actually be quite a strong force attracting them. It's due to an effect very very similar to the casimir effect:

 

http://en.wikipedia.org/wiki/Casimir_effect

 

But with sea waves...

Quickly then:

The world's largest tanker would most certainly be bigger than 565000 kg. How about 565000000 kg? (Somebody probably mixed up kg and tons, ships are often measured in tons).

 

That brings the force to about 2000 N.

With a mass of 565000000 kg, the acceleration will be an impressive 4E-6 m/s2.

 

Not in the mood to calculate how long it takes to travel 100 meters, because the acceleration will increase when they get closer (luckily for the poor researchers hanging around there with a stopwatch and a tape measure).

Edited August 8, 200817 yr by CaptainPanic

There will actually be quite a strong force attracting them. It's due to an effect very very similar to the casimir effect:

But with sea waves...

 

I am pretty sure that this force, if it exists, will only be present when the ships are very close together (i.e. not more than a few meters).

depends on the distribution of wave lengths on the water. sure, for the small surface waves you see on a calm day they will need to be close together but if you have massive long wave length waves then it'll work when they are further appart.

depends on the distribution of wave lengths on the water. sure, for the small surface waves you see on a calm day they will need to be close together but if you have massive long wave length waves then it'll work when they are further appart.

 

What is that called? Phase cancellation? Attenuation? Zero Resistance Attenuation? Is there a reference which talks about the phenomenon? Or is it theoretical math?

casimir effect.

It's quite possible to have the small waves laid ontop of larger waves... I recall seeing photos which showed ships about 5m apart straped together with bars to stop the problem...

Quickly then:

The world's largest tanker would most certainly be bigger than 565000 kg. How about 565000000 kg? (Somebody probably mixed up kg and tons, ships are often measured in tons).

 

I hold my hand up and shall proceed to the naughty boys corner

Edited August 9, 200817 yr by swansont
fix quote tag

It's quite possible to have the small waves laid ontop of larger waves

 

Radio would be pretty boring if it weren`t;)

casimir effect.

 

I'm not sure this is truely the casimir effect, as that really requires quantised waves....

 

But it's certainly very very similar and doesn't have it's own name.

yeah, i know its not the same but its the closest thing i could think of, at least a semi decent analogy.