The second problem with our assumption sis that the earth is not a sphere. It’s flattened a bit at the poles and bulges out at the equator. The ring around equator is larger than a ring around the poles by 21 km, which makes the poles closer to the center of the earth than the equator! Free-fall at the poles is slightly more than free-fall at the equator.
But before you book a trip to skydive in Ecuador, Colombia, Brazil, Sao Tome, Gabon, the Republic of the Congo, the Democratic Republic of the Congo, Uganda, Kenya, Somalia, Maldives, Indonesia or Kiribati, let’s talk about the assumption we made… The earth really does rotate. That’s not a surprise. How does this affect the value of g then? The bottom line is that gravity changes with altitude from 9.78 to 9.84 m/s2., mostly due to the earth spinning, but some to the earth not being a perfect sphere.
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As astronomers discovered objects orbiting other stars, they recognized the need to improve the definition for planet. In August 2006, the Internataional Astronmmical Union (IAU) set up three guidelines on what to call a planet. they are:
1) It is in orbit around the Sun.
2) It has sufficient mass to assume hydrostatic equilibrium (a nearly round shape).
3) It has “cleared the neighborhood” around its orbit.
Other objects share an object with Pluto, so they downgraded Pluto’s status to “dwarf” planet.
The decision to downgrade Pluto is controversial and the debate still continues.
what is the reason Pluto is not a planet, does it have to do with size or something else