# Difference between Earth's magnetic field and Earth's gravitational field [closed]

I have a misconception about this. Are these really different? If so then how?

And one more problem is that, whether satellites orbit around the Earth because of Earth's Magnetic Field or Earth's Gravitational Field?

• They are two completely different things. See Earth's gravity and Earth's magnetism. – user243267 Dec 9 '19 at 9:51
• Don't the names of the fields suggest they are different? Magnetic versus gravitational? – Kyle Kanos Dec 9 '19 at 11:45

## 1 Answer

Your question is too broad and too basic to answer it directly in any way. But I will try to answer it by using some very important checkpoints you will have to pay attention if you decide to study physics and in particular classical mechanics.

Gravity and magnetism. These two are completely different phenomena of physics. Gravity acts as a force between two masses while magnetism acts as a force between magnetic poles (which is just an idealization of a region of space where magnetic flux seems to get higher, but it really is a force that acts upon moving electric charges). Electric charges are influenced by magnetic forces in very complicated ways (see Maxwell's equations) while gravity can't influence electric charges at all. The "gravitational charge" (the mass), comes in just one flavour (positive mass), while magnetic poles can be positive or negative, creating much more varied consequences. In fact, magnetism can be attractive and repulsive at the same time, while gravity is just attractive. Magnetic poles always come in pairs, north and south, while a gravitational mass is independent of whatever is going on in the rest of the universe and can be conceptually isolated entirely without the need of another mass.

However, some attempts have been made to compare the two concepts since the inception of modern science. Renaissance revolutionary scientists like William Gilbert speculated about the Moon been bounded to Earth by some influence that could be related to magnetism. Later, Newton showed that the force acting on the Moon (or any satellite) was in fact gravity. The force of gravity between two masses, $$m_1$$ and $$m_2$$, separated a distance $$r$$ can be expressed by Newton's universal Law of gravitation:

$$F = -G \frac{m_1m_2}{r^2}$$

And the force between two magnetic poles of two different magnets follows an equation of the similar form

$$F = \frac{\mu}{4\pi} \frac{q_{m_1}q_{m_2}}{r^2}$$

While the expression for gravity is in the universal form (to which understand it completely) the expression for the magnetic poles, $$q_{m_1}$$ and $$q_{m_2}$$, is a particularized form of a much more general set of laws that involve electric charges and currents. But this it is an interesting way to compare both forces (even if they are in general totally diferent): In this situation both forces operate following the inverse of the square of the distance.

One striking difference between the two formulas is the proportionality constant they include. For gravity this constant is $$G = 6.674\cdot 10^{-11} \; N\cdot m^2/kg^2$$ and for the magnetic force the constant is $$\mu/4\pi = 10^{-7} \; N/A^2$$. Without any smart analysis of this we can tell that gravity can be said to be much weaker than magnetism: like $$10^4$$ times weaker. That would kind of suggest that magnetism is the force operating between planets but is not. The forces here also depend on the magnitude of the charges involved; Earth has a huge "gravitational charge", a.k.a. a huge mass, while its magnetic field is as strong as a loosely held magnet in a fridge. Also the fact that magnetism has a way larger constant for the force formula means that it decays with distance to nothing and it is only powerful enough at close ranges. Satellites, the Moon or everything that falls into Earth is strongly influenced by gravity. Galaxies, which also have magnetic fields, attract one another by gravitational interaction even if gravity is still "the weaker force", because of the extreme amounts of mass they have and the ridiculously small intensity of the magnetic fields involved.

Another interesting relation between the two is the one you can make using relativity, for certain regimes. Gravitomagnetism tries to create a Maxwellian system of equations for gravity with some success, but still is not a very usefull way of describing the physics of both, rather than an elegant mathematical detour with interesting points.

Many theoretical physicists devote their entire life to the concept of unification of forces, so resemblances and links between the two are often made in the most sofisitcated levels of physics, using Einstein's relativity or Quantum Mechanics. We are far away from the ideas of classical mechanics here but just so you know there are efforts to reconcile the two in a unified framework of understanding. That said, our current understanding of physics separates both completely and all the efforts to merge these forces have been failed in some way or another (for now), so they have to be quite different in nature (at least in first approximation) if decades of scrutiny and weird speculation (such as extra physical dimensions) have not completely succeded in merging the two.

• Your question is too broad and too basic to answer it directly in any way. If you think this, then making an answer is not the best option. Questions that are too broad to have a direct answer are supposed to be closed on this site. In general you should not reward poor questions with answers. – Aaron Stevens Dec 9 '19 at 13:51
• You are So Mean @Aaron – Saikat Das Dec 9 '19 at 17:33
• @SaikatDas I am sorry you feel that way. I don't associate posts on here with how a person actually is, so my comments are not personal in any way. I would say the same thing on any off-topic question on this site. – Aaron Stevens Dec 9 '19 at 19:03