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Old 03-04-2019, 17:03   #31
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Re: Aircon on yachts

Unless you have a good soft start system you’re going to need a way bigger inverter to get the compressor going. My new 10k btu system pulls 17A without soft start, 7A with (on startup) at 240V.

So the answer to your question is that it’s technically possible with a huge battery bank and big inverter, but really the answer is no in all practical terms without a generator.
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Old 07-04-2019, 04:11   #32
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Re: Aircon on yachts

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Maybe once upon a time, in a land far, far away


The metre is defined as the length of the path travelled by light in vacuum in 1/299 792 458 of a second."


The international nautical mile and the knot while not part of the SI are 'non-SI units accepted for use with the SI" and the nautical mile is defined as exactly 1852 m. (But the poms, define a nautical mile as 1853 m )
It is still an attempt to be one 10-millionth the distance from the equator to the pole. Specifying it based on distance covered in a period of time at light speed is just improving the accuracy and consistency, since the earth s not a perfect sphere.

They have done the same thing for English units also but it doesn't change the underlying source of those units.
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Old 07-04-2019, 06:00   #33
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Re: Aircon on yachts

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Maybe once upon a time, in a land far, far away


The metre is defined as the length of the path travelled by light in vacuum in 1/299 792 458 of a second."


So, light is faster or slower in a Vacuum?
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Old 07-04-2019, 06:06   #34
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Re: Aircon on yachts

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So, light is faster or slower in a Vacuum?
Light changes speed depending on the medium. Light travels slower in Earth's atmosphere than in a vacuum. Light travels slower in certain materials such as glass or plastic. That's how eyeglasses work. So the answer to your question is light travels faster in a vacuum than anywhere else that we know about.

It has been postulated that light might be able to travel faster than it does in a vacuum. But it's an unproven theory. Except on television science fiction shows where FTL (faster than light) engines are quite common.
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Old 07-04-2019, 06:42   #35
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Re: Aircon on yachts

So, Einstein and the “textbooks” are incorrect?
Speed of light is not a constant?
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Old 07-04-2019, 06:51   #36
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Re: Aircon on yachts

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So, Einstein and the “textbooks” are incorrect?
Speed of light is not a constant?
Go back and

reread your textbooks. Most have the caveat that the speed of light in a vacuum is constant.

Light traveling thru a medium is slower proportional to density. That’s how lenses and prism work.

One of Einstein’s big realisations was that the spread of light as it a appears to you is constant in all dirctections regardless of your speed. That has al sorts of implications for frames of reference and time dialation.
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Old 07-04-2019, 07:23   #37
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Re: Aircon on yachts

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Ahhh, but the nautical mile shares more similarities with the metric system then it does with the imperial system. For example, the length of both a nautical mile and metre are ultimately derived from the circumference of the earth.
Maritime and air travel maintained the Nautical mile and the knot (nm/hr) because until recently they depended on celestial navigation for long distance travel. This is because during the French Revolution when the Metric system was established they wrote most parts into law but not decimal angles (Grad, gradians or gons) or decimal time (10 “hour” per day) and they didn’t catch on.

If the grad or gon had caught on km and kph would be the default units in navigation.
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Old 07-04-2019, 07:53   #38
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Re: Aircon on yachts

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So, Einstein and the “textbooks” are incorrect?
Speed of light is not a constant?
Einstein never said speed of light was constant in all mediums. He said nothing could travel faster than a wave particle with zero resting mass (which light is). Einstein knew well that a perfect vacuum had a dielectric constant of 1.0 (by definition) and all other mediums (air, water, glass, plastic, etc.) have a dielectric constant greater than 1.0 and thus wave particles slow down as they pass through them.
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Old 07-04-2019, 09:07   #39
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Aircon on yachts

I’m unsure as to whether or not the speed of light has been measured in different mediums, but feel pretty sure you can refract and or reflect light without slowing it down, so I feel that lenses don’t work by varying speed.
I’ll actually bow out as it’s over my head, but was brought up believing that the speed of light was a constant.

I do believe it or not understand why the speed of light can’t be exceeded.
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Old 07-04-2019, 09:19   #40
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Re: Aircon on yachts

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I’m unsure as to whether or not the speed of light has been measured in different mediums, but feel pretty sure you can refract and or reflect light without slowing it down, so I feel that lenses don’t work by varying speed.
Well, that’s exactly how a lens works.

There is a big push these days in the super fast computer trading business. The computers that are hooked together by fiber optic cables are slower than computers connected wirelessly because the glass fiber slows down light more than air slows down the wireless data. You can send a wireless message from New York to London faster than a fiber optic cable.
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Old 07-04-2019, 09:33   #41
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Re: Aircon on yachts

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was brought up believing that the speed of light was a constant
Just like the calorie

the amount of heat required to raise the temperature of one gram of water

in order to be a standard unit, any "real life" measurement must include the **normally missing** qualifier

at a pressure of 1 standard atmosphere.

The boiling point of water is not 100°C at the top of Mt Everest, nor at the bottom of the Marianas Trench.
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Old 07-04-2019, 14:20   #42
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Re: Aircon on yachts

a64, if you want to dabble in quantum religions, look for articles about the speed of light--in a Bose-Einstein condensate. (The 5th state of matter and a fairly unknown one.) You can apparently do some terribly wrong things like slow down light to a crawl, it very much gives reason to say that our four dimensions are just a subset, a very limited subset, of reality and that our "rules" just show our ignorance. Add in the fact that you can split some particles in two, and the two pieces continue to show "quantum entanglement" meaning that if you rotate one--the other rotates, despite there being no physical connection.
Coming back to marine "aircon" (do they sell words by the letter in Oz and the UK?) it just means that if you've really got a grasp on physics, it should be possible to simply transfer the vibrations (the heat energy) to a different dimension, leaving the boat both cool and quiet.
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Old 07-04-2019, 16:32   #43
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Re: Aircon on yachts

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Just like the calorie

the amount of heat required to raise the temperature of one gram of water

in order to be a standard unit, any "real life" measurement must include the **normally missing** qualifier

at a pressure of 1 standard atmosphere.

The boiling point of water is not 100°C at the top of Mt Everest, nor at the bottom of the Marianas Trench.


Changing the boiling point with pressure doesn’t change the amount of heat required to raise the temp of the water.
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Old 07-04-2019, 16:53   #44
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Re: Aircon on yachts

Interesting.

Then why do the traditional unit definitions for both btu and calororie reference altitude or atmospheric pressure?
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Old 07-04-2019, 17:17   #45
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Re: Aircon on yachts

No idea, I thought the speed of light was a constant, remember.
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