[samcottle (OP)]

Hi everyone,

Here's another theory I came up with. I heard Neil deGrasse Tyson talking about how the Earth bulges at the Southern Hemisphere, that it's an oblate spheroid, and it got me thinking that perhaps this bulge is due to gravitational influences not from the rest of the galaxy, but from the rest of the universe. This would imply not only that the universe as a centre of mass but also that it is enormous, way beyond our current understanding. Could it be possible to calculate what sort of mass would be needed to produce this bulge over those sorts of distances?

[evan_au]

perhaps (Earth's) bulge is due to gravitational influences not from the rest of the galaxy, but from the rest of the universe

Tidal forces decline as something like the cube of distance.
- Jupiter, although it is much more massive than the Moon, has a much lower tidal influence on Earth than the Moon, because it is more distant
- The Moon has a larger influence than the Sun, even though the Sun is far more massive
- You can effectively ignore the influence of any stars beyond the Sun
- or indeed, any influence from the Galaxy or the Universe.

This is because the Universe pulls on both sides of the Earth almost equally, so it produces no detectable tidal bulge.

I suspect that to explain the Earth's slight pear shape, you would need to look at more local things like land (south pole) vs sea (north pole),  ice loading,  and convection currents in the Earth's mantle.
See: https://en.wikipedia.org/wiki/Figure_of_the_Earth#More_complicated_shapes

[samcottle (OP)]

Thanks, will look into it.