Why can't we see the Gravity?

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In summary: Just a metal box.In summary, an accelerometer cannot measure the force of gravity, and a gravitometer does not measure gravity.
  • #1
We can see the Effect of the force of gravity. But how come we can't see the force itself?
 
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  • #2
I think we are "looking" real hard, at least for a particle or wave.

But on another level, why suppose that our eyeballs are built to see much at all? Extraordinary instruments with a huge dynamic range, ultimate sensivitity of close to a single photon, that they are, but in the end very narrowband EM detectors. Gravity is not EM.
 
  • #3
Science_Rebel said:
We can see the Effect of the force of gravity. But how come we can't see the force itself?

Your question is rather puzzling.

You can see the effect of wind, but you can't see wind itself.

You can see the effect of electrostatic force, but you can't see the force itself

You can see the effect of x-ray, but you can't see x-ray itself

You can see the effect of heat, but you can't see heat itself

etc...etc...

So, why did you pick on "gravity" only?

Gravity (and forces in general) isn't an object. It has no physical substance for visible light to be reflected on and then hit your eyes, where by a series of nerves and electrical signal transfer that to your brain and you "see" it. However, this kind of "seeing" is very limited in range. Your eyes can only see a very limited range of EM spectrum. It is not a very good indicator of what are around us in our world.

Zz.
 
  • #4
You make a good point ZapperZ.
 
  • #5
First off, what do you mean by "see"?

No device can be built that directly detects the force due to gravity because any gravitational field is locally equivalent (i.e., indistinguishable by measurement) to a uniform gravity field. Consider, for example, an accelerometer.

An accelerometer is a physical device comprising a case that loosely holds some object (e.g., a mass attached to a spring). The loosely held object will accelerate with respect to the case if the case is subjected to some external force that does not affect the subject object. Equipment inside the accelerometer measures the motion of the sensed object with respect to the case.

A uniform gravity field affects the case and the sensed object equally. There is no way to measure the acceleration due to gravity in a uniform gravity field. The equivalence principle says that on a small enough scale, any real-world gravity field is indistinguishable from a uniform gravity field.

An accelerometer can measure the departure of the gravity field from uniformity. However, such departure is immeasurably small for typical accelerometers. A properly constructed accelerometer (one in the loosely held object is shielded from all external forces but gravity) can measure any force other than gravity. But it cannot measure gravity.

A gravitometer, for example, is a kind of accelerometer. Despite its name, a gravitometer does not measure gravity. Objects fixed on the surface of the Earth experience an upward force exerted through contact with the Earth's surface that counteracts the gravitational force. Gravitometers measure this contact force, not the gravitational force.
 
  • #6
Is it wrong to still think that gravity is bending of spacetime, because of mass? Or is the most common way (and most expected way) to think of gravity as gravitons, or a certain particle/wave that makes gravity?

I find the bending of spacetime so nice to think of that I want it to be that way.
 
  • #7
"Bent" with respect to what? And what causes this "bending"? Gravity is tautological in general relativity. Physicists like to look for root causes. Tautologies are not root causes.
 
  • #8
Jarle said:
Is it wrong to still think that gravity is bending of spacetime, because of mass? Or is the most common way (and most expected way) to think of gravity as gravitons, or a certain particle/wave that makes gravity?

I find the bending of spacetime so nice to think of that I want it to be that way.

Now you should know better than to start something like that in this thread. The OP appears to ask a rather elementary question about "force" in general. We should not complicate things further by bringing in General Relativity.

Furthermore, there have been tons of thread and posts in the GR forum as it is already that have already answered this question. So let's not hijack this thread into something more convoluted.

Zz.
 
  • #9
Doesn't an Etovos device "see" gravity?
Much like a charged particle sees another charged particle.

It doesn't seem to qualify as an accelerometer.
No springs.
 

1. Why is it that we can't see gravity?

Gravity is a force that is invisible to the human eye. It is a phenomenon that exists between objects with mass, and is responsible for pulling objects towards each other. While we can observe the effects of gravity, such as objects falling to the ground, we cannot directly see the force itself.

2. If gravity is invisible, how do we know it exists?

The existence of gravity has been proven through scientific experiments, observations, and mathematical equations. For example, Sir Isaac Newton's law of universal gravitation explains the relationship between mass and gravitational force. This, along with other evidence, confirms the existence of gravity.

3. Why does gravity affect objects differently?

Gravity affects objects differently because it is dependent on the mass and distance between objects. The larger the mass of an object, the greater its gravitational force. Additionally, the closer two objects are to each other, the stronger the gravitational force between them.

4. Can we ever see gravity in action?

While we cannot see gravity itself, we can observe its effects. For example, we can see the effects of gravity when objects fall to the ground, or when planets orbit around a star. We can also use tools such as gravitational wave detectors to indirectly observe the presence of gravitational waves.

5. Is there any technology that can help us "see" gravity?

There is currently no technology that allows us to directly see gravity. However, advancements in technology, such as gravitational wave detectors, have allowed us to better understand and study the effects of gravity. Scientists continue to research and develop new technologies that may one day allow us to "see" gravity.

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