Weight Variation by Latitude

Weight Variation by Latitude refers to the claims that scales have measured masses to weigh slightly less near the equator and slightly more near the polar areas. It is asserted that this is due to a combination of the centrifugal effect from the rotation of the earth and the increased mass at the equator.

Upon assessment of the experiments supporting this, it is found that these experiments are conducted with the scale and test body exposed to the surrounding atmosphere. A scale is calibrated for one area and then taken to another area, uncalibrated. Measures are not taken to isolate the test body and the measuring device from the influences of the environmental atmosphere. It is known that pressure and humidity affects scales. It is also known that that pressure is greater at the poles and lesser at the equator. It is further known that pressure is greater at lower altitudes near sea level and lesser at higher altitudes. Humidity likewise has a relationship with between latitudes and altitudes.

Andrew Huszczuk, Ph.D. writes:

Scales Affected by Atmosphere
From Drift in Measurements with Analytical Balances we read:

One precision scale manufacture lists many factors which can affect a scale:

Factors That Can Affect Your Scale’s Accuracy

If the air pressure from the calibration environment is different than the operating environment, it will effect the scale. Also listed on the page are temperature and humidity which can affect the operation of a precision scale.

Bathroom Scales
Inconsistent scale readings are also readily seen at home in bathroom scales. If left uncalibrated, the reading will vary wildly.

Can I Trust My Bathroom Scale?

Kern Gnome Experiment
The precision scale manufacturer Kern conducted a public test of the variation of weight by latitude, showing that weight changed when a ceramic gnome and one of its precision scales were sent to members of the public at different latitudes:

Website: http://gnome-experiment.com/



Scale Not Calibrated
The scale was calibrated in Germany and then sent to different areas:

https://www.chemistryworld.com/news/gnomadic-experiment/4924.article

Long weigh from gnome: The bizarre experiment where a garden ornament travels the world to measure gravity

Procedure
Members of the public were instructed to place the gnome onto the scale and to record their results:



Spring Scale Experiment
The Spring Scale Experiment shows a similar methodology of calibrating in one area and taking to another:

http://physicstasks.eu/930/spring-scale-on-the-pole-and-on-the-equator



The book Practical calculations for engineers describes the same method:

Worldwide Air Pressure Gradient
The following sources explain that air pressure has a relationship with latitude, being lower near the equator and greater near the poles:

https://www.pmfias.com/pressure-belts-pressure-systems-equatorial-low-sub-tropical-high-sub-polar-low-polar-high/

World Distribution of Sea Level Pressure

and further down:

https://en.wikipedia.org/wiki/Polar_High

Worldwide Humidity Gradient
Humidity, like temperature and pressure, has a relationship with the equator as well:

https://en.wikipedia.org/wiki/Humidity#Climate

Addendum
When one examines the properties of the air they will find that other elements too are related to temperature, pressure, and humidity, such as air viscosity and thermal diffusivity -- all of which may affects the operation of scales. It is due to the complex nature of the air that scale manufacturers and metrologists recommend calibrating often, whether a scale is indoors or outdoors. Indeed, a company's failure to calibrate its scales in certain fields can result in fines and even legal action.

Adopting this basic and reasonable level of scrutiny, an experiment based on uncalibrated scales and different environments must only be questioned for validity.