Does acceleration greatly affect gravity

[Killa Klown]

I've thought of this new concept of gravity that I'm not sure if it is correct. I was wondering does acceleration affect gravity more than mass. See everything with gravity so far that we know of has some type of rotation going on. So does that mean that it is not mass that carries gravity but the force of acceleration (which also depends on the mass of the object to have a strong enough force to accelerate).

[Bignose]

See everything with gravity so far that we know of has some type of rotation going on.

 

Erm, no. Let's look at Newton's law of universal gravitation:

 

[math]F=G \frac{m_1 m_2}{r^2} [/math]

 

F is the magnitude of the gravitational force between the two masses

G is the gravitational constant

m_1,2 is the masses of the 1st and 2nd objects, respectively

r is the distance between the two masses

 

This theory has been validated time and time again. Where exactly is the "some type of rotation going on"?

[Killa Klown]

It's going on on the entire shpere or solar system

[Bignose]

No, Newton's law predicts exactly the same gravitational force, whether the obejct is rotatng or not. Look at the equation again, there are no terms whatsoever for rotation. If rotation were important to the gravitational force, shouldn't there be a term for the period or speed or angular momentum?

 

Look, Venus' mass is pretty close to Earth's (Venus' mass is 82% that of Earth's), as is it's diameter (95% of Earth's). If you could walk around on its surface, the force of gravity pulling you to the surface would be pretty close to the same as on Earth. Just to put a number to this discussion, you would weigh about 90% of your Earth weight on Venus. But, Earth rotates on its axis once a day, but Venus rotates on its axis once every 243 Earth days. The fact that Venus rotates significantly more slowly than the Earth does not change the fact that the gravity on Venus' surface is pretty close to Earth's.

 

Gravity is a function of an object's mass, not it's rotation. I am aware of no evidence that has ever shown gravity to be a function of rotation, if you have some to present to substantiate your theory, I'd much like to see it. However, like I said above, Newton's Law of Universal Gravitation has been tested over and over and over, and it comes up correct every time. It's going to take a lot of really good evidence on your part to overthrow it.

[Killa Klown]

There was this experiment conducted by NASA in 1966. The experiment was conducted on the spaceflight gemini XI. The experiment involved using the rotation of a tether to create artificial gravity. It was both a sucess and a failure. It did create artificial gravity, but very little of it.

[theCPE]

Artificial gravity due to rotation is not the same thing as gravitational attraction between two objects.

 

The rotation is actually causing a centripetal force which feels like gravity.

 

Any outside observer not rotating with cylinder would not feel this "gravity" as it is not a real gravitational force.

[Killa Klown]

But do you think that by making the acceleration faster and more powerful we can create a artificial gravitational force strong enough to act similar to the gravitational field on earth. Thereby creating what one could consider gravity.

[insane_alien]

yes but it will still not be gravity.

[Killa Klown]

I know it's not "the gravity" but it's artificial gravity so it can be considered a type of gravity (if there is more than one type).

[ecoli]

I know it's not "the gravity" but it's artificial gravity so it can be considered a type of gravity (if there is more than one type).

artificial gravity is just the science-fiction name. The force is only perceived by humans to feel like gravity, but it actually not the same force.

 

Current theory says only one type of gravity exists... but the models are is changing all the time:

 

http://www.newscientist.com/article.ns?id=mg18524834.000

 

but note, that this article is not talking about the same thing you are.

[Bignose]

There aren't "types of gravity" There is gravity which is a function of mass, and then there are ways of mimicing gravity termed "artifical gravity". But, mimicing is not the same as being.

 

I can mimic Albert Pujol's baseball swing, but sure as heck cannot hit home runs like him. I can mimic Tiger Wood's golf swing, but sure as heck cannot hit 300+ yard drives. I can mimic President Bush's voice, but that doesn't make me the President. See what I am saying -- just because there are ways of mimicing gravity, doesn't make them gravity.

 

In this case, the mimicing of gravity is caused by being flung outward by the spinning. If you spin at just the right speed, that flining can feel exactly the same as 1 Earth's gravity. But, we don't define forces by how they feel. And just because the flinging from being spun mimics gravity, does not mean that it is gravity.

 

Also, you never answered my questions... "If rotation were important to the gravitational force, shouldn't there be a term (in Newton's Law of Universal Gravitation) for the period or speed or angular momentum?" and if you had any evidence that simply spinning would change the gravitational effect of an object. Ideally, this would be two seperate experiments -- The first experiment measures the gravitational force between two objects both of which are not spinning at all, and the second measures the gravitaional force between those two exact same obejcts one of which is spinning. If you perform this experiment and the gravitational forces are different, then you have the evidence to support your theory. But, right now, there is no evidence to support your idea at all, which means as far as we know, it is wrong. I'm sorry, but without evidence, your idea is wrong. Period.

 

Edit: I just wanted to reply a little to ecoli's post there, which brings up a great aside. While there are mountains and mountains of evidence that support Newton's Law above, which means science has a very good grasp on how gravity behaves. Meaning, in terms of using Newton's laws for predictions it is great -- we know how to launch probes to fly next to and take pictures of comets, and know how to launch probes to land on Mars, etc. etc. However, sceince does not have a very good grasp on how gravity works. I.e. the graviton has been proposed, but has never been confirmed measured. Which means that there is much uncertainty on how gravity does what it does. But, we know what gravity does and what affects what gravity does (i.e. the masses of and the distance between objects), and it does not include whether one or both or neither of the objects is spinning.

[Killa Klown]

What force can the "artificial gravity" be considers as.

[Killa Klown]

Can it be possible to use the rotational gravity theory to create a successful gravity mimicing machine for astronauts to use in their spacecraft and not have as many problems with weightlessness.

[Bignose]

What force can the "artificial gravity" be considers as.

 

It is inertia. An object in motion continues along the same line at the same speed until another force acts on it. So, consider being on the inside of a spinning ring. You are moving along sideways because of inertia, but because the floor is moving around in a circle, the floor gets in your way and turns you in just a little. Well, now inertia moves you along that slightly different line, but again, another bit of floor gets in the way and turns you again. Repeat over and over. If the ring is large enough, the floor won't have a very significant curve to it, but because inertia keeps forcing you to run into the floor, this running into the floor mimics the force of gravity. Hence, you get an "artifical gravity"

 

And, yes, this sort of system can be used to mimic gravity for longer spaceflights or habitation of space stations. The first act of Kubrick's film 2001 has a great example of what one such space station could look like. http://carriedaway.blogs.com/carried_away/2005/03/2001_where_are_.html Look at the second picture on that guy's blog.

[swansont]

The equivalence principle of general relativity tells us that you can't tell the difference between gravity and any other acceleration. Any acceleration will be "artificial gravity" (as three posters have already implied or stated)

[Jean Maxwell]

Well and look at what we have here. The expansion of the universe has been observed, if gravity where much different say it did function is such a way that more attraction was generated due to acceleration, or spin.

 

What would happen is that would GREATLY alter the balance of cosmic expansion. More gravity would require a greater outward surge of inflation, or expansion to balance to what we observe.

 

It would alter other observable phenomena such as the formation of galaxies, somthing that isnt fully understood yet, but is being studied heavily.

 

Very intersting line of thinking however.

 

As I was reading this post I began thinking about some abstractions of gravity.

 

I am fairly new to physics and understand certain things less than clearly.

(I hope I can effectivley explain this heh)

 

We observe all massive bodies form shperes for reasons of symmetry, and see the heaviest of materials "sift" to the center.

 

What IF we could organize the heavy material in a different fashion.

(I know I know it would inevitably crush itself back to a sphere)

But suspend disbelief for a moment and supose that we have a technology that could allow us to take the heaviest material and form it into whatever structures we wanted.

 

What shapes could we make that would significatly change the shape of spacetime?

 

Would it really change at all? Or would the force only be lessened, spacedout, and diffusal, canceling ect?

 

I guess alot of the answers to this question would come from a full understnding of the nature of Quantum gravity, and the nature of spacetime.

 

But its interesting to think about. My initial design was inverting mass from center to exterior and have us walking around on the inside of a sphere, but I quickly realized that if I used a quantum gravity thought process enteracting with a higs feild then it would not allow us to walk around the inside with a simple heavy "crust" and hollow interior. It would require massive "lumps" at intervals, and then I started to think well hell then I might as well make it a sphere, and again there is no point to the thought experiment.

 

But then I thought well, if spacetime is fabric like, then a spiral structure with super massive beams could "twist" it enough to detect. ( Whats the thoughts on high density energy such as the lasers possed in this guys "time Machine" theory http://www.physorg.com/news63371210.html )

 

Also I dont really understand the fundamental reason energy could create gavity? any explaination would be awesome. ; - )

 

This idea is NOT original I know, but I wanted to hear other opinions, and perhaps I have not thought of something relevant that has been observed, or some geometry, Im very weak in maths, have just started my formal training.

[Severian]

The equivalence principle of general relativity tells us that you can't tell the difference between gravity and any other acceleration. Any acceleration will be "artificial gravity" (as three posters have already implied or stated)

 

That line of reasoning does not lead to that conclusion. Since the equivalence principle does indeed tell us that you can't tell the difference between gravity and any other acceleration, then any acceleration really is gravity when viewed in the correct frame.

[swansont]

That line of reasoning does not lead to that conclusion. Since the equivalence principle does indeed tell us that you can't tell the difference between gravity and any other acceleration, then any acceleration really is gravity when viewed in the correct frame.

 

"Really is gravity" implies a mass nearby, though, does it not? What's wrong with just saying it's all acceleration, and it doesn't matter what the source is?

[Killa Klown]

Well what if the scientific understanding of gravity originating from mass (I'M JUST SAYING) ends up being somehow proved wrong.

[Bignose]

Well what if the scientific understanding of gravity originating from mass (I'M JUST SAYING) ends up being somehow proved wrong.

 

Then a more accurate theory will replace the one we have. At its very core, science if very objective. If a new theory comes along, explains everything the old theory does, predicts new things the old theory didn't, or predicts things better than the old theory, and there is sufficient evidence that the new theory is more correct the new theory will be adopted. Science is objective in that a theory is measured by how well it predicts phenomena. If a new theory predicts better or more than the old theory, the new theory is considered better. It really is that simple.

 

But, science is also objective in rejecting speculations without evidence, such as the one you presented in this thread. There is no evidence that rotation of an object affects its gravitational force, so science rejects that claim. It is all about the evidence.

[Killa Klown]

Well what if the earth is to big to perform a scientific experiment to actually gain proof that the theory can actually be correct. Think about this, name one thing that has a gravitational pull that doesn't contain some type of accelerating force of some type.

 

Can someone at least guess of something, I won't mock you for your resply, I just can't come up with ANYTHING myself that contains gravity BUT doesn't contain acceleration.

 

I know I'm not right, so someone at least answer the question.

[insane_alien]

any non-zero force acting upon a non-infinite mass will produce an acceleration.

[Bignose]

insane_alien is referring to that most basic of physical laws [math]F=ma[/math]

 

F = force

m = mass, and

a = acceleration

 

Simply put, if there is a mass, there is a gravitational force associated with that mass. And force is proportional to acceleration. If there is force, there is acceleration, no matter what the force is from. Drag, friction, rocket boosters, or gravity.

[someguy]

Well what if the earth is to big to perform a scientific experiment to actually gain proof that the theory can actually be correct. Think about this, name one thing that has a gravitational pull that doesn't contain some type of accelerating force of some type.

 

I guess it depends on how small you go and how much you trust about what is currently most believed when you go that small, and i guess it also depends on what causes mass. how small can you go before there's no mass anymore? can you even do that? personally i think that mass is energy and that energy causes the warping of space time, energy is pretty much in all cases that i can think of unless you go so small i don't know like for your question, some type of motion. The only kind of different thing is light. which seems to be more in the realm of warping of space time rather than like most other things that exist that have mass.

[Killa Klown]

So there is absolutely no mass in the know Universe that contains gravity BUT does not contain any type of Accelerating Force.