# Is there any opposition to gravity? [closed]

we have friction which opposes motion of moving body on another surface, resistance or reactance which opposes current, reluctance which opposes flux etc ,each and every physical phenomena there is opposition like wise we any oppsition to gravity .

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• Buoyancy opposes gravity. – S. McGrew Apr 10 at 0:40
• It's not quite clear from your question what you're looking for. Friction and resistance are somewhat similar in that there's an associated dissipation. Reactance and reluctance, on the other hand, do not have an associated dissipation. There are obviously forces that oppose the gravitational force but I assume you're thinking about some kind of 'gravito-resistance' or 'gravito-reactance' that gives rise to an opposing force due to a (changing) mass current? – Alfred Centauri Apr 10 at 1:28
• The point is just that the examples you gave works for gravity, once gravity is the force that causes the motion, eg downward an inclined or falling through atmosphere. No kind of antigravity field, anyway. – Alchimista Apr 10 at 11:09
• @S.McGrew I don't know if I would word it that way. Buoyancy is more a consequence of gravity's interaction with fluids than it is an actual opposition. – JMac Apr 11 at 17:34
• ytivarg – PM 2Ring Apr 11 at 18:32

Gravity isn't a force in general relativity, but by opposition to gravity, the only thing I can think of is another pseudo force called the centrifugal force. This force likes to push objects away from the center. But in general, with gravity being such a weak effect, there is ''resistance'' against it in every day circumstances, but probably not the type you were thinking of.

While it is not in opposition to gravity in the typical sense, Dark Energy could be considered such an opposition.

Gravitational "force" is merely a result of an objects movement forward in time through curved spacetime. As time flows forwards, dark energy expands the space of the universe and gravitational bodies are separated by space and gravitational forces are lessened.

So while neither is explicitly a force per say, both gravity and dark energy seem to result from a forward flow of time, one apparently pulling objects together, the other, seemingly, pushing them apart.

If I understand your question correctly, you are more or less looking for what parameter in an equation you can dial up to decrease the effects of gravity. Since you mention current and resistance, I think it might be helpful to look at things from the perspective of fields and object interactions.

Point 1:

Ohm's Law is: $$V=IR$$ Thus if you dial up the resistance as you said, you are reducing the current. Another way to write Ohm's Law is: $$\vec{E}=\vec{J}\rho$$ Where $$E$$ is the Electric Field, $$J$$ is current density, and $$\rho$$ is resistivity. Notice that what you are really doing is resisting the effects of a field. It is by resisting the effect of the field, that the rate of charges past a point decreases. So what is resistance exactly? It is the essentially any object which blocks the mean free path of a charge. So in a circuit, this tends to be atoms, valence electrons, and what not. In essence, it's not a force, or a 'particular' thing, but a collection of objects that "resist" the charge motion.

Point 2:

Where does $$E$$ come from? It is from the equation: $$\vec{E} = {kq\over{r^2}}\hat{r}$$ In other words, it is a constant times a charge divided by the square of the distance from the field source. We can derive a similar field equation for gravity: $$\vec{g}= {Gm\over{r^2}}\hat{r}$$ If you wanted to build an "Ohm's Law" for gravitational fields, then you could write it as the following: $$\vec{g}=\vec{v}*?$$ There isn't really a physics variable that I can stick in for that question mark.

Point 3:

So what is that something, well if we are sticking to the Ohm's Law analogy, it should be a collection of objects that are blocking the free path of the object in motion (in this case only a mass instead of a mass with net charge). This is really just any objects that can be collided with. Since matter exists at all sort of scales, depending on the size of your moving object, this could be anything from air molecules in an atmosphere (air resistance), water molecules in a glass of water (buoyancy), or if it was a planet or star sized thing you could even say a densely packed asteroid belt or space junk would behave similarly.

That was kind of a roundabout way to get there, but in summary. The things that resist moving objects under the influence of a gravitational field are objects that contact the object in motion. This is far more eloquently summarized in Newton's First Law.

"Object's in motion will remain at rest or in uniform motion in a straight line unless acted upon by an external force." In this case, it's the sum of many small external forces.

In the example you gave, where resistance opposes current, that can be shown by the equation;

$$V=IR \rightarrow I = \frac{V}{R}$$.

Likewise, with reluctance and flux;

$$\mathcal{R}=\frac{\mathcal{F}}{\Phi}$$.

As we can see from these equations, it is not so much that they "oppose" each other, it is more that they are inversely proportional to one another. Therefore, to find the "opposition" to the force caused by gravity, we have to look at the equation for universal gravitation;

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

As you can see, the force is inversely proportional to the distance between the masses squared (assuming all other factors are kept constant), so I would say the "opposition" to gravity is simply distance (or seperation).

In one sense, no, we haven't discovered any kind of magic anti gravity field. That said, the floor does a pretty good job of opposing gravity to keep you out of the center of the Earth.

Non-inertial reference frames can have psuedo forces which seem like anti gravity (that's why the moon doesn't fall on us), but nothing you could use to make a sci-fi style hovercraft.

Well if an object is in free fall, considering the object is not in vacuum,then the air resistance will oppose gravity,which is the only force acting on the object during free fall.

Think about temperature. Temperature is the average energy per unit volume. When you take away energy, the temperature goes down. At some point its all gone and we call that (absolute) zero.

Gravity is also caused by energy. If you take energy out of an area, its gravity goes down. Just like temperature, you can only go to zero, there's no "negative energy" and thus no "negative gravity". So: no, you can't do that.

Yes, this does mean that areas with higher temperatures have higher gravity. However, the coupling constant is very small. So if you heat up something the gravity will go up, but by some tiny amount compared to the gravity it has just by existing and E=mc^2.