at what altitude above the earth's surface will a person's weight be half of what it is as the earth's surface
408176
Well, the weight of an object is inversely proportional to the distance sqaured.  According to Newton's Law of Graviation, F = (G * m1 * m2) / (r^2), in order to cut the force (or someone's weight) in half, the distance has to increase by the square root of 2, or 1.41ish.  Earth's radius is 3963 miles, so 1.41 times that is 5604 miles.  But that's the distance away from the core.  To get the altitude, subtract earth's radius.  You get an answer of 1641 miles above Earth's surface.  Hope this helped!
695350
Yes.\n\nIn fact there is a very nice relationship that when you are below the surface of the Earth (assuming the Earth is a perfect sphere), your weight is proportional to your radius from the center. E.g. if you were 1/3 of the way to the center (2/3 from the center), you'd weigh 2/3 as much as you do on the surface.\n\nThe proof uses a variant of Gauss's law from electromagnetics (because Newton's equation for gravity and Coulomb's equation for charge have the same form). Without delving into advanced calculus, the gravity that affects you depends only on the earth in the sphere below you - everything at your altitude and above cancels out. Since the volume of a sphere is proportional to r^3, but the gravitational force is proportional to 1/r^2, the remaining term is simply r - so your weight is proportional to the radius, if you're inside a sphere.\n\nOf course this assumes that the Earth's weight is distributed evenly. However, it's close enough to even for most purposes.
887515
Please be warned - there are MANY incorrect responses above.\n\nThe theoretical answer to your theoretical question is that you would be weightless at the centre of the earth because the forces of attraction would exactly cancel out.\n\nTo address some of the errors above:\nYou would not be pulled apart because the mass of the earth is not enough.  Similarly, you are not pulled apart when standing ON the earth, even though the earth is pulling your feet more strongly than your head.  If the earth were enormously massive then you would be (it's called being spaghettified, although it ought to have a different name if you are the centre!).\n\nThe force of attraction does NOT increase as you get closer to the centre of the earth.  The responder is thinking about Newton's Law of Gravitation which applies to POINT masses.  If you apply it to a large body such as the earth then you find that only the sphere underneath you attracts - the rest of it cancels out.  ie The earth is roughly 6400km in radius.  If you are 5000km from the centre then you will feel the force of attraction of a 5000km radius sphere of the Earth at a distance of 5000km - the force of attraction of the remaining 1400km 'shell' exactly cancels out.\n\nYou would not 'feel' the force of the sun (any more than you do on the earth) since its force of attraction is providing the centripetal force required to move you in a circle around the sun.\n\nThe force of gravity is NOT caused by the rotation of the earth.  In fact, if the earth stopped rotating we would all be a little bit heavier since a part of the force of gravity is being used to provide the centripetal acceleration necessary to keep us spinning around once per day, with the earth (on the equator this amounts to about 0.3%).\n\nYou also ask about gravitons!!  How they work is a difficult question since they are theoretical!  According to classical Newtonian theory, gravity is simply a fundamental property of matter - matter attracts other matter and that's that.  Newton himself was always uncomfortable about the idea of "action at a distance" but even his genius could not solve the problem, given the limitations of the time that he lived in.  Along came Einstein and gave a solution - matter distorts the shape of space and the apparent force of gravity is actually simply the result of an object moving in the distorted space.  Think of a heavy ball on a rubber sheet and another ball moving along.  It does not 'know' about the heavy ball but it changes its path towards the ball because the surface on which it is rolling has been distorted.\n\nThe graviton is an attempt to explain the phenomenon of gravity without recourse to considering distortions of space-time.  Bodies with mass emit particles called gravitons.  They interact with other massive particles.  The degree of ineraction can be calculated and reasonably easily represented on a Feynman diagram.  Try an internet search.  Huge tanks full of washing up liquid have been built down abandoned deep mine shafts to try to detect these particles.  Some 'events' have been noted but they remain elusive, as far as I know.\n\nHope this goes some way to answering your interesting questions.
128964
No it is not equal. As we move upwards that is in altitude the gravitational pull decreases.If we go in more depth the the pull decreses. Moving towards the equator also decreases this pull of gravity. It is least at the poles. But for convenience we take the average of all these which comes out to be 9.8.This is also called the acceleration due to gravity.
1150073
That would sort of depend on what you land on, now wouldn't it? If you have a parachute you could jump from the top of the Petronas Towers in Malaysia and survive. I think the farthest a human has fallen accidentally and lived is under fifty feet, unless they just happened to fall into something soft like a snow drift.
323470
not really a question. All points of land are based on sea level. If you standing on the beach with your feet in the water your elevation would be 0. walk up it might be 1ft or more. standing on a mountain it might be 2500ft above sea level.
384862
The air is thinner the higher you go.
218928
I don't think there is an altitude limit... in any case I don't think you are going above 4000 meters... they should be ok...
1170472
You've got a couple of strange answers so far.  Look, the formula written above is correct, the mass of the earth is basically the same, but the mass of your surroundings isn't the same.  The pull of gravity is less the higher your elevation, greater the lower the altitude.  If you're on land with higher density, you'll have a greater pull then on land with a lower density.  Pretty much everywhere on land gravity isn't even, out in the middle of the ocean, it's very close to even.  But, keep in mind, these differences are pretty much negligible.  The only way to be able to measure the difference is with scientific equipment.  Actually, it's common practice to measure gravitational anomalies under ice sheets to gleam information about the formations underneath.
1041394
Actually, the term "weight of the earth" has no real meaning.  The mass of the earth can be calculated, but weight and mass are not the same thing.  Weight is usually used to express the apparent mass of an object in the Earth's gravitational field at the planet surface.  To speak of the Earth's weight is to try to speak of the Earth's apparent mass in relation to itself and its own gravitational field.  It's like asking how far a point is from itself.  It has no meaningful answer.  If your science teacher put this question to you in terms of weight instead of mass, they should go back to coaching PE or something.
671105
almost exactly, assuming someone on earth is doing the measurement. someone moving very fast would get a different result.
173277
25 lbs\nThe distinction between mass and weight becomes obvious when we move away from the earth's surface. For example, on the surface of the Moon gravity is only about one sixth as strong as on the surface of the earth. A one kilogram mass is still a one kilogram mass – mass is an intrinsic property of the object. However, the weight of the object – the downwards force due to gravity – is only one sixth of what it is at the surface of the earth; that is, only one sixth of what we would expect one kilogram to weigh.
214499
It all has to do with altitude. The higher you are from the earth, the colder it gets. Air is also thinner.
382880
Look at this page,\nhttp://mintaka.sdsu.edu/GF/explain/atmos_refr/horizon.html\nIt explains it very well mathmatically.\n\nThe answer would of course depend on the person's height above the Earth's surface and on the radius of the Earth, both of which are know/measurable.
52820
The gravitational pull on the moon is 1/6 that on Earth.  Note that on the Moon only your Weight (Pulling force of planet,etc) changes and not your Mass (Measure of amount of matter in an object).  So if your Mass is 100lb (approx 45kg) on Earth, it would still be 100lb on the Moon.  \nHowever your Weight changes from being 450N (450 newtons using the equation Weight = Mass x gravitational field strength on earth which is taken as 10N/kg) on Earth to 75.2N on the moon (1/6 that on Earth where g = 1.67N/kg)
90476
It is not effected to any significant degree.\n\nThe numbers used to do any calculations would absorb any effect which may occur.  For instance the mass of the Earth is about 5.9742 E24 kg.  But do you really think this is an exact number, no, it is just an estimate rounded off.  To try to use this value for the Earth's mass to try to calculate the effects of something so insignificant will not work too well.\n\nWhen you are standing on the Earth, you and the Earth together have a certain angular momentum.  When you jump, angular momentum must be conserved (its the law).  But now that your mass is rotating slightly farther out than it used to be, your angular momentum changes, there for the Earth's must change ever so slightly to compensate.\n\nIf you wanted "numbers and calculations", you did not specificy nearly enough information.
526135
It's about 1/6 earth gravity. (But don't forget to add in 1/6 of the spacesuit you have to wear, too.)