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Old 07-04-2019, 22:14   #46
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Re: Aircon on yachts

To the unenlightened I will disclose that a meter is the distance from the ground to my belly button, within an accuracy of a hair or two.

Seriously now.
The value of the metric system is not in what the units itself represent. Those things are meaningless and we could as well use body parts like they used in the past.

The real practical value of the metric system is in the easy of use, and the easy of making mental calculations. Not that many people do this days, kids don't do 2x3 without using a calculator, let alone work out the volume of a fuel tank, but that aside, tens and hundreds are just a matter of adding zeros or taking them away. Try doing that with imperial. Nightmare.
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Old 07-04-2019, 22:40   #47
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Re: Aircon on yachts

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Originally Posted by a64pilot View Post
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.
It absolutely has. Speed of light in a vacuum is what you're thinking about, which is of course a theoretical number since there's no such thing in reality. The speed of light in molten Sodium is apparently only about 30-odd mph, which is about as slow as it's been measured.

Refraction is nothing but slowing light down.
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Old 07-04-2019, 23:03   #48
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Re: Aircon on yachts

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Originally Posted by Tillsbury View Post
It absolutely has. Speed of light in a vacuum is what you're thinking about, which is of course a theoretical number since there's no such thing in reality. The speed of light in molten Sodium is apparently only about 30-odd mph, which is about as slow as it's been measured.

Refraction is nothing but slowing light down.

Melting point of Sodium: 97.79 °C

https://abcnews.go.com/Technology/story?id=99111&page=1


"The speed of light is normally about 186,000 miles per second, or fast enough to go around the world seven times in the wink of eye. Scientists succeeded in slowing it down to 38 mph. They did this by shooting a laser through extremely cold sodium atoms, which worked like “optical molasses” to slow the light down."
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Old 08-04-2019, 00:16   #49
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Re: Aircon on yachts

Newtonian Physics was based on time being absolute. Einstein thoroughly debunked that with his views on Relativity. Speed is a function of time, and Einstein proved that time is relative to the observer. If the speed of light is fixed, then please solve the following situation: You are in a spaceship with a velocity of 0.5 the speed of light, you shoot a photon of light forwards from your spaceship. Logically you would conclude that the photon has a velocity of 1.5x speed of light. According to the thinking that light cannot exceed 186000 miles/sec, this can't happen. Quantum physics has shown that a photon on light can be simultaneously in 2 places, and that the state of something is not fixed until it is observed (Schrödingers Cat).
Now, this is somehow all related to putting Aircon on a boat
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Old 08-04-2019, 01:07   #50
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Re: Aircon on yachts

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Changing the boiling point with pressure doesn’t change the amount of heat required to raise the temp of the water.
For "normal" usage with "normal" accuracy required...true. If you are raising 1cc of water from 10c to 11c at 1m altitude vs 1000m altitude, you will be hard pressed to measure a difference because the difference is so tiny.

But for situations where you need extreme accuracy, the answer is pressure does change the amount of heat needed to raise 1 cc of water by 1 degree.

If you take 1cc of water at 1 atmosphere and and increase the pressure, it will now occupy a space smaller than 1cc...if you now add more water (at the higher pressure until you have 1cc in volume), you need more energy to heat because there is more water to heat up.

Works the same english or metric units.
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Old 08-04-2019, 04:08   #51
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Re: Aircon on yachts

Thanks, makes sense, googling did not reveal such a clear explanation.

Always a matter of finding the right combination of keywords, but in such an abstruse topic some prior knowledge of the domain is needed.
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