THE SOUTHWORTH PLANETARIUM
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2022-2023: LIX
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Sunset: 5:00 p.m.
Civil twilight begins: 6:21 a.m.
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Moonset: 8:25 a.m. (2/8/2023)
Julian date: 2459983.21
"Let us be moral. Let us contemplate existence."
-Charles Dickens (born 211 years ago today)

THE BI-WEEKLY ASTRONOMER
Tuesday, February 7,2023
Maximum Earth Gravity

____________________________________________
The 'Daily Astronomer' has gone away until the beginning of the new school
year.For now, it has been replaced with 'the Bi-Weekly Astronomer,' which
will post every Tuesday and Friday at noon.        When the DA does return
-and it most assuredly will- we will reboot our 'Big History' series.
Thank you all for your patience and understanding. And, of course, thank
you for reading the DA...or BWA
______________________________________________

Our very first BWA takes us to the now overflowing Pandora's Jar to answer
a question about where on Earth one would have to go in order to weigh the
most.

Where could a person feel the maximum gravity on earth?
<https://thesciencebase.quora.com/Where-could-a-person-feel-the-maximum-gravity-on-earth>

I would like to offer two answers to this question.

First, where along Earth’s surface would one experience the maximum surface
gravity? If Earth were both perfectly spherical and uniformly dense the
surface gravity would be constant along any point on the surface. Instead,
however, Earth can be regarded as an oblate spheroid. Earth ‘bulges’ at the
equator due to the planet’s rotation.

[Image credit: Humboldt State University]

Although the difference between the polar and equatorial diameters is
slight, it does cause the value of Earth’s surface gravity to vary with
latitude. Why? Because an object along the equator will be farther from
Earth’s interior than an object at either pole.

Toward the equator, Earth’s surface gravity is at a minimum, around 9.77
m/s^2 The highest will be around either pole. So, where would one find the
maximum point?

Christian Hirt, a geoscientist affiliated with Western Australian Centre
for Geodesy, Curtin University, Perth, Western Australia, Australia and his
team conducted a thorough survey of Earth’s surface gravity through data
collected from satellites such as GOCE.* In the 12 August 2013 issue of
Geophysical Research Letters they produced ultra high resolution images of
Earth’s gravitational field. The team also estimated the points of minimum
and maximum surface gravity.

The maximum point is located in the Arctic Sea at latitude 86.71°N
longitude 61.29° W. Here the surface gravity value is 9.83366 meters per
second-squared.

Second answer:

However, the maximum gravitational pull one could experience on Earth would
not be at this point along the surface of the Arctic Sea. Instead, the
maximum ‘surface gravity’ of 10.7 meters per second squared occurs at a
distance of 3740 km from Earth’s center, the region between the mantle and
the outer core known as the Gutenberg discontinuity.

Earth’s surface gravity is highest (10.7 meters per second squared) along
the Gutenberg discontinuity, the region separating the mantle and the outer
core.

The surface gravity is maximum here because of the higher densities of the
material within this region. Gauss’ law tells us that the gravity an object
experiences is truly related to the mass within a certain volume because of
the inverse square law. If you are close to a highly dense region, the
matter near you will have more of an effect that the less dense material
that is farther away.

So, if you want to experience the maximum surface gravity while still
remaining on Earth’s surface, go to the Arctic Sea. If, however, you want
to experience the maximum surface gravity anywhere on or in the planet,
venture down to the Gutenberg discontinuity.

I hope this answer proves helpful

*GOCE = Gravity field and steady-state Ocean Circulation Explorer.



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