Tuesday, August 22, 2017

Yes, you do weigh less at the Equator, and here's roughly how much

Earths Gravity
You can change your weight in many ways.  But, there is one way that doesn't require doing anything more than just travelling North or South.  Most dramatically, your weight is different at the Equator than it is at the North Pole.  This is due to the centrifugal force of the Earth's daily rotation.

The Earth spins one full rotation in a period just under 24 hours (kinda).  At a spot that is one inch from the North (or South) Pole, the speed of the ground as it rotates around the axis is literally just over 1/4in per hour.   By comparison, a common snail can slither 1837in per hour.  However, at the Equator, the speed of the ground as it rotates around the axis is a whopping 1,036 MPH!  This is faster than the Speed of Sound (761.2 MPH).  Thankfully, the laws of nature do a great job of making sure we do not notice such things as we walk about in your daily lives.

Even still, that is fast enough to notice the effect of the centrifugal force of Earth's spin on your weight.  Basically, you weigh less at the Equator than you do at the North Pole.  Your mass doesn't change, of course.  It's just that the pull of Earth's gravity is slightly mitigated by it's rotation about its axis.

That said, there are many factors that affect the local gravity.  The problem is that gravity itself is generally measured in terms that are meaningless to everyday life.  So, when an online local gravity calculator tells you that your local gravity in meters per seconds squared, that isn't all that helpful in finding out how much more or less you'll weight somewhere else.

I've created a simplified calculator as a spreadsheet .  It will tell you how much you'll weigh at any latitude based on your current weight at your current latitude.  The calculations on the spreadsheet are rough.  They do not take into account many factors that might affect your weight, nor are they precise enough for serious scientific studies.  However, they are close enough to satisfy whatever curiosity you might have.  As such, use the spreadsheet for entertainment purposes only, and have fun seeing how much less you'll weight at particular latitudes!

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