Physics Questions about gravity

[ZionsRodeVos]

I know there are some here who like discussing things related to physics (the Traveler comes to mind). In the past few weeks my interest in physics has grown immensely. Probably because of a novel I am working on but I think that simply sparked the interest.

Anyway, for anyone who has pondered these questions or have thoughts I have some questions I'd like your perspective on. I of course can't handle the mathematics for such things yet and likely don't have much of the physics terms learned yet. Some of the questions may delve into astronomy too.

Theories about gravity seem to indicate that all mass has gravity and yet the gravity does not become strong enough to be felt until an object is about moon size. Why is that? Or is it that not everything with mass has gravity only the large objects? Is there any proof that smaller objects, say the size of a marble, have gravity?

[MrShorty]

Is there any proof that smaller objects, say the size of a marble, have gravity?

An early experiment by Henry Cavendish is considered one of the earliest successful efforts at measuring the density of the earth based on Newton's law of gravitation. Cavendish experiment - Wikipedia, the free encyclopedia and he could see the gravitational attraction between 300 pound balls and 2 pound balls. I would venture to say that, yes, with the correct equipment, we can show gravitational attraction between small objects.

Mathematically, Newton's law of Gravitation is probably the easiest expression to fix ideas. F=G*m1*m2/r^2 Newton's law of universal gravitation - Wikipedia, the free encyclopedia Two things to note from this equation. 1) the inverse square law -- meaning that the force due to gravity drops off quickly as the distance increases. and 2) the magnitude of G (~7E-11 N m2/kg2). the take home message would be that, in theory, everything exerts a gravitation pull on everything else. In practice, the force of gravity is so weak that at least one of the masses must be quite substantial before its gravity becomes discernible in practical ways.

[Lakumi]

Kaunis' beloved law, Kaunis be praised!

(sorry something from my novel lol)

[Anddenex]

If the earth was still, would it still have a gravitational pull? Would gravity still exist? With the movement of the earth, like a whirlpool, it draws other objects of less mass toward it. Objects of heavier mass are not drawn to it, but then again we would all then be sucked into the sun if that were true.

I once read, or listened probably, to an article specifying there isn't any gravity at all, or at least how we define gravity. I thought it was interesting.

[ZionsRodeVos]

The math is beyond me at this time. I will have to brush up on my calculus to have any hope in understanding the formula's.

I hadn't heard of the Cavendish Experiment and find it interesting. I may be blind but I looked at the diagram and I do not see a small x near the small ball to the right of the big ball. It looks to me like there is an h and n there but no x. Did I miss something with that diagram?

Anddenex are you referring to the rotation of the earth on its axis or the rotation of the earth around the sun? Or both?

So far in my quest to understand the source of gravity I am finding problems with each theory I find. Most likely this is due to my lack of knowledge and so I try to gain more in the hope it will increase my understanding of gravity.

[jerome1232]

My understanding is that the model for gravity hasn't changed much since 1916, general relativity is still the best we have to explain it.

The whole thing with mass bending space time etc.... I know perhaps this is old and elementary but...

[ZionsRodeVos]

I like elementary as it helps a person like me to understand and this video is very simple to understand. I've watched others that talked about general relativity that way. For some reason I just haven't been able to grasp the entire concept though.

One thing that bugs me about that is I can see clearly how that effects a planet but not how that would affect me, especially if I were to be in a hole and digging ... Hmm that just might explain what I just looked at with what would happen if you dug a hole through the earth and jumped in.

If space is warped even while you are underground that would explain why once you get to the center you would feel no gravity. But I don't see how space would be warped below the surface of the earth.

I also have a hard time understanding how warped space could have any influence on me since I seem to be able to pass right through that same space when walking around and going up and down stairs.

[Dravin]

Hmm that just might explain what I just looked at with what would happen if you dug a hole through the earth and jumped in.

It'd collapse in on itself as the Earth became increasingly plastic with depth (and thus temperature). Oh sorry, that's the geology answer, not the physics with spherical cows answer. :)

Edited July 10, 2013 by Dravin

[jerome1232]

I also have a hard time understanding how warped space could have any influence on me since I seem to be able to pass right through that same space when walking around and going up and down stairs.

The stairs example makes sense to me, it is difficult to climb the stairs because of the warped space time, where it's easy to descend the stairs for the same reason.

[Anddenex]

Anddenex are you referring to the rotation of the earth on its axis or the rotation of the earth around the sun? Or both?

I was referring to its rotation on its axis. The rotation around the sun adds a new dimension.

Honestly though, I don't know much, just from snippets I have read here and there, nothing deep though.

[ZionsRodeVos]

It'd collapse in on itself as the earth became increasingly plastic with depth (and thus temperature). Oh sorry, that's the geology answer, not the physics with spherical cows answer. :)

Yeah, that theory sets aside a lot to give optimal conditions and illustrate what would happen.

And if you are a geologist then I may just have some other questions for you.

The stairs example makes sense to me, it is difficult to climb the stairs because of the warped space time, where it's easy to descend the stairs for the same reason.

Hmm, I'll need to think about this more.

I was referring to its rotation on its axis. The rotation around the sun adds a new dimension.

Honestly though, I don't know much, just from snippets I have read here and there, nothing deep though.

Fine with me, I just wanted to be sure I understood you before I gave my doubts about what you said.

The thing that bothers me about gravity being generated by the earths rotation on its axis is that it seems to me to be too slow by itself to generate gravity since it takes 24 hours to make one rotation on its axis.

And I probably know less than you about all this and am just using my limited learning and logic to try and understand while also asking others what they think and trying to learn from the theories physicists have put forth such as Newton and Einstein.

[estradling75]

I also have a hard time understanding how warped space could have any influence on me since I seem to be able to pass right through that same space when walking around and going up and down stairs.

First understand that you live in a warp of space caused by the earth itself.. That is what your body is used to and adapted to.. Trying to detect minor variations of warped space while here is like trying to see the stars when the sun is shining. (Plus your body is not really equipped to sense such small changes)

You need large changes in the warped space and then you can sense those... They feel like freefall (getting out of the warped space of earth... Which we can simulate) or increased G-forces aka weighting more (for when you move into a greater warped area... Which we can also simulate)

[ZionsRodeVos]

Thanks! It is some of the simplest things that elude me such as the fact that I am used to this warped space and can't detect minor changes.

[Anddenex]

Fine with me, I just wanted to be sure I understood you before I gave my doubts about what you said.

The thing that bothers me about gravity being generated by the earths rotation on its axis is that it seems to me to be too slow by itself to generate gravity since it takes 24 hours to make one rotation on its axis.

And I probably know less than you about all this and am just using my limited learning and logic to try and understand while also asking others what they think and trying to learn from the theories physicists have put forth such as Newton and Einstein.

As to my limited knowledge, which I wouldn't say is greater than yours, I have understood the terminology "gravitational pull" with regard to the rotation of each planet.

Again, I haven't studied this enough to give really any strong conclusion.

[estradling75]

Thanks! It is some of the simplest things that elude me such as the fact that I am used to this warped space and can't detect minor changes.

Well if you are looking for perspective consider this... The International Space Station orbits at just over 400 kilometers away. On the surface of the earth 400 kilometers is a day or weekend trip... and people do it all the time its easy, but it is not fighting the warp.

However that same easy distance going against the warp caused by the earth requires specialized equipment, tons of power, and costs alot. So much that it is only in our recent history have we been able to do so. It is the biggest barrier by far to any kind of local space travel.

[Windseeker]

Don't care about the science, I just want one of these already.

[Traveler]

I know there are some here who like discussing things related to physics (the Traveler comes to mind). In the past few weeks my interest in physics has grown immensely. Probably because of a novel I am working on but I think that simply sparked the interest.

Anyway, for anyone who has pondered these questions or have thoughts I have some questions I'd like your perspective on. I of course can't handle the mathematics for such things yet and likely don't have much of the physics terms learned yet. Some of the questions may delve into astronomy too.

Theories about gravity seem to indicate that all mass has gravity and yet the gravity does not become strong enough to be felt until an object is about moon size. Why is that? Or is it that not everything with mass has gravity only the large objects? Is there any proof that smaller objects, say the size of a marble, have gravity?

Mathematically there is a direct relationship of mass and gravity. This means that the force of gravity increases at the same rate that the mass of objects increase. The mathematics of gravity has worked quite well since Newton. However, there have been slight variants observed. Most of the corrections have been made by the adjustments of relativity. There are additional problems at the sub atomic particle level that is mostly explained by quantum mechanics and particle theory.

If you are writing sifi please do not confuse mass with weight. In essence weight is a calculation of gravitational force that varies according to the distance between two objects. Mass is a constant and remains independent of other objects.

Gravitational theory is problematic and outside of the mathematics of gravity little can be demonstrated. For example there is little to explain exactly what gravity is. Relativity attempts to explain the attraction of gravity as the warping of space time. The problem is that to explain the warping of space time we indirectly reference a force that maintains physical things moving in space time - that in essence does not exist. Thus objects traveling in a straight line get bent with gravity and become affected by divots or holes in space time.

To complicate matters farther the recent discovery of Dark Energy has the potential of changing much of what we thought we knew about gravity. This is because gravity is a force that will work against the expansion of the universe and dark energy is the force that pushes the universe out causing expansion. Many scientists believe that Dark Energy is some kind of anti gravity but this has not been proven.

There are more problems - for example one theory of gravity utilizes a sub atomic particle called a graviton that is similar to photons and the Higgs Boson in that the gravity may exist both as particles and waves and transmit like the Higgs Boson the properties of gravity rather than mass.

One last note - all particles with mass, regardless of how small will manifest the force of gravity on anything else with mass. One great question is why gravity is so week compared to the other forces (like electromagnetic force) yet in great distances is the dominate force of the universe. This is something that has not been figured out yet. I have a personal theory that utilizes another dimension - but to prove my theory I need access to a very expensive particle accelerator.

The Traveler

[Anddenex]

Don't care about the science, I just want one of these already.

Now someone is actually talking about important vehicles. Our scientists and developers need to get smarter, quicker, I am not getting any younger. :)

[ZionsRodeVos]

Well if you are looking for perspective consider this... The International Space Station orbits at just over 400 kilometers away. On the surface of the earth 400 kilometers is a day or weekend trip... and people do it all the time its easy, but it is not fighting the warp.

However that same easy distance going against the warp caused by the earth requires specialized equipment, tons of power, and costs alot. So much that it is only in our recent history have we been able to do so. It is the biggest barrier by far to any kind of local space travel.

I like this example.

Don't care about the science, I just want one of these already.

Yep, I'd love one too.

Mathematically there is a direct relationship of mass and gravity. This means that the force of gravity increases at the same rate that the mass of objects increase. The mathematics of gravity has worked quite well since Newton. However, there have been slight variants observed. Most of the corrections have been made by the adjustments of relativity. There are additional problems at the sub atomic particle level that is mostly explained by quantum mechanics and particle theory.

I've started looking into quantum mechanics and I think particle theory too. Is either or both of these what they call string theory?

If you are writing sifi please do not confuse mass with weight. In essence weight is a calculation of gravitational force that varies according to the distance between two objects. Mass is a constant and remains independent of other objects.

Yep, I'm writing a sci-fi novel and do believe I have understood the difference between weight and mass. Whatever your mass is it stays the same unless you have a way of changing it, such as disintegrating a huge portion of a moon or planet would change its mass.

Gravitational theory is problematic and outside of the mathematics of gravity little can be demonstrated. For example there is little to explain exactly what gravity is. Relativity attempts to explain the attraction of gravity as the warping of space time. The problem is that to explain the warping of space time we indirectly reference a force that maintains physical things moving in space time - that in essence does not exist. Thus objects traveling in a straight line get bent with gravity and become affected by divots or holes in space time.

Does this problem of maintaining physical things moving bother many physicists? Is this why it is still called a theory even though the mathematics for it are very good?

To complicate matters farther the recent discovery of Dark Energy has the potential of changing much of what we thought we knew about gravity. This is because gravity is a force that will work against the expansion of the universe and dark energy is the force that pushes the universe out causing expansion. Many scientists believe that Dark Energy is some kind of anti gravity but this has not been proven.

When was this Dark Energy discovered? Hmm, hadn't realized there was a force like Dark Energy working against gravity. I need to learn more about it.

There are more problems - for example one theory of gravity utilizes a sub atomic particle called a graviton that is similar to photons and the Higgs Boson in that the gravity may exist both as particles and waves and transmit like the Higgs Boson the properties of gravity rather than mass

I've been learning about graviton's too. Do you think that if it is found that graviton's exist that will replace the portion of Einstein's theory that spacetime is warped?

One last note - all particles with mass, regardless of how small will manifest the force of gravity on anything else with mass. One great question is why gravity is so week compared to the other forces (like electromagnetic force) yet in great distances is the dominate force of the universe. This is something that has not been figured out yet. I have a personal theory that utilizes another dimension - but to prove my theory I need access to a very expensive particle accelerator.

The Traveler

Can you go to CERN and use theirs? Could anyone with interest go there and set up experiments?

That is part of what bothers me why physicists say gravity is so weak and yet I feel it very strongly keeping me on earth.

[NeuroTypical]

Is there a "Help The Traveler obtain his particle accelerator" fund? If so, I'm in for five bucks.

[Lakumi]

I wish I could Kamehameha but that's not in the cards either

[Windseeker]

Now someone is actually talking about important vehicles. Our scientists and developers need to get smarter, quicker, I am not getting any younger. :)

You know I thought we were getting close when I read up on Choas theory (String theory?) and how they identified gravity particles. But I havn't heard anything big since.

Edited July 9, 2013 by Windseeker

[Windseeker]

I wish I could Kamehameha but that's not in the cards either

There is hope.

Kamehameha- YouTube

[Lakumi]

There is hope.

Kamehameha- YouTube

though I will admit nothing good can come if I gain Dragonball Z powers:lol:

[jerome1232]

In science, a theory is something that is very nearly fact. It is backed up by experiments repeatedly and hasn't been disproven.