Here is a rather silly question with an answer that won’t be any real use to anyone, but still won’t leave me alone: What is the heaviest place on Earth?
We all know that we would feel lighter if we were standing on the Moon or Mars because the gravity there is only a fraction of the one at home. In pyhsics exercises they always tell you that you should assume a local gravity of 10 m/s² (or 9.81 m/s² if they let you use a calculator), but it is always implied that the actual value differs from place to place. Stockholm has a different gravity than Istanbul etc.
There are probably a lot of factors going into this. I guess elevation would be an important part and that the lightest place on Earth is perhaps somewhere on top of the Himalaya, but what would be the place on earth where you have the highest gravity? Moving elevators etc. or taking a submarine/ digging a tunnel is not allowed. Where on the surface of the planet do you get the most Newton per Kilogram of your weight from just standing there?
And if you are standing there would it be wortwhile to wait for a certain time like a really low-tide? Should I visit there at 6 o’clock on a day of the full moon when the moon is on its perige or perhaps something like that?
This question is so stupid and totally useless that I am convinced that someone else must have gone through the trouble of finding the answer before.
No, because the Earth is not a point mass; if you went on a Journey To The Centre Of The Earth there would be a point where you would start to experience a decrease in gravity, because of the mass above you.
I thought so too at first, but looking at the wikipedia page you linked to and clicking around a bit on various links I realized that elevation above sea level does not translate into distance from the center of the earth by adding a constant factor. The earth is not really a sphere but more of an ellipsoid so you are a lot closer to the centre on the poles than at the equator. Another thing speaking against a tropical location for the heaviest place on earth might be the fact that centrifugal forces from the earth’s rotation are stronger there than in places close to the poles, but I don’t know if that counts for much.
I guess unless I want to dig down into the Ice of the Bentley Subglacial Trench from your link the heaviest place on earth would be a place on some arctic or antarctic shore…
That is almost certainly correct. Although the Dead Sea shore is the lowest dry-land point relative to sea level, you have to remember that the Earth is not spherical - it bulges, with the equatorial circumference greater then the polar circumference. That’s why the summit of Mount Chimborazo in Ecuador is the furthest land point from the Earth’s centre, despite being 8,500ft “lower” than Everest.
Seeing as the Dead Sea shore is less than 1500ft below sea level, it seems to me that if you stood on the beach at the northern edge of Greenland at sea level you’d be a lot closer to the Earth’s centre than you would at the Dead Sea.
Standing on the ice (~sea level) at the North Pole, you’d be heaviest of all, I imagine.
That’s all assuming the Earth is uniform density though, isn’t it? If there were vast deposits of heavier elements directly underfoot, that might also increase local gravity (although not by much, I expect).
If you stand at sea level anywhere in the world, your weight will be exactly the same. A mass of water is pretty effective in finding a uniform datum of equal weight as registered on a scale.
The reason that water bulges at the equater is due to the counteracting radial upward force wherer tangential speed of the earth’s surface is greatest. Whether your weight is affected by pure gravity or a combination of gravity and cetrifugal force is irrelevant to our concept of weight.
Tides are complex things, determined not only by the local gravity and the centrifugal force, but by the realities of moving water from place to place (which isn’t instantaneous), changes in density due to salinity and temperature, and other factors. If this weren’t the case, the water levels should be the same on both sides of the isthmus of Panama, and they aren’t. L. Spragfue de Camp made the interesting argument that Claudius Ptolemty and others thought the Indian Ocean must have been “land-locked” (isolated from the other seas by land, as many early maps show it), because they knew that “water finds its own level”, yet the water level on the different sides of the Sinai peninsula are measurably different.
This is from memory when I took physics a long time ago but I do remember reading that the Earth’s gravity was strongest (or the value of ‘g’ was highest) in Northern Norway and was weakest in East Africa.
Of course, I tok physics so long ago, Isaac Newton was still considered an upstart.
I’d say mangetout is correct in thinking that the value of ‘g’ also varies according to the geological properties of a particular area.
Also, as Lars-H mentioned, the Earth’s rotation plays a large part in this. Generally speaking, you’d be lightest when near the equator and heaviest at the North or South Pole.
I am fairly sure that it does not represent actual values, but merely additional corrections that have to be added or substracted after first calculating your supposed local gravity based on latitude.
It gives values for gravity anomalies from -60 to +60 milliGal. Since 1 m/s² is the same as 1 N/Kg, which is the same as 1 hectoGal this would mean that we are talking about maximal variations here of about 0.0006 m/s² here.
According to Wikipedia the difference between pole and equator is about 0.05 m/s² or about two orders of magnitude larger.
Wikipedia also says that the gravity will decrease by about 0.3 mGal per meter that you climb upwards so even the biggest anomalies from the GRACE maps could be simply compensated by climbing a 200 meter high tower. The changing effect of the gravity of the sun and moon appears to be in the same order of magintude as minor elevation changes.
So I the proximity to the poles seems far more important than almost any other factor. I guess unless I want to go to an antarctic research station the Island of Svalbard would be my best bet to feel really heavy. It is extremly far north and partly lies on an orange patch indicating medium extra heaviness on the map. India still seems to be the best place for loosing a few pounds, but I still am not sure if I would be better of climbing a high mountain in the Himalayas or staying closer to the equator.
How much does the centrifugal force (which is strongest at the equator) counteract gravity?
Obviously it can’t be very significant at all or the long/high jump records would all be set in
places near the equator, but I’ve always wondered about that…
Which tallies with what I said above - the total difference is of the order of 0.5%, of which about two thirds (i.e. 0.35%) is due to the centrifugal force, and the remainder because of the Earth’s squishedness (technical term). But of course the squishedness is also due to the centrifugal force…