Gravity of the Sun?

  • Thread starter Bill Gavlas
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  • #1
I am missing something here. In old Star Trek episodes, Captain Kirk and Captain Picard were often caught in the gravitational pull of a nearby sun and had to really turn on the engines to escape this terrible force.

Where on earth did this concept of the sun’s gravity come from?

In case we have forgotten, the Sun is an enormous explosion. To say that it has gravity is inconsequential to the outward forces it exerts on the planets. It would seem to me that trying to measure the gravity of the Sun would be like trying to measure the gravity of an atomic bomb as it explodes. The gravitational field of the bomb casing is nothing compared to the outward force that the bomb produces.

The Sun’s gravitational field is negligible compared to the outward (anti-gravity) forces that it exerts on the planets that travel around it.

So, if the Sun is essentially pushing the planets out into space, how do the planets stay where they are in orbit about the Sun?

Iron, the metal that comprises at least some portion of the core in any planet, is attracted to electricity. The primary output of the Sun is electricity! The planets stay in orbit around the Sun due to the attraction of the planets to the Sun and not the gravitational pull of the Sun!

From time to time, you can visit the vacuum cleaner department of a major department store and see that they will have a beach ball floating in the air that is being exhausted from the vacuum. This is not proof that the vacuum cleaner is any better than any other vacuum, since it does not take a lot of air pressure to cause the beach ball to float, but it is an attention grabber to get you to notice the vacuum cleaners.

The beach ball is affected by the gravitational pull of the earth, yet it is suspended in space by the force of the air exhausting from the vacuum. The picture this produces is exactly the same way the planets and the Sun are related. The planets are attracted to the electrical output of the Sun, yet the Sun is forcing the planets into space by the sheer force of its’ explosive power.

A number of interesting observations can be made when viewing the relationship of the Sun to the planets in this manner.

First of all, the collapse of the Sun will occur much sooner than previously estimated. As the force of the Sun diminishes over time, Mercury will enter the outer edges of the Sun, and, if the surface of the Sun is not hot enough to vaporize the entire planet and blast its’ element back into space, Mercury will then initiate the collapse of the Sun. If the Sun is strong enough to blast the Mercurial elements into space, then Venus may be the culprit to cause the collapse.

Secondly, it is easy to calculate the density of a planet, thereby calculating the gravity of the planet. The surface area of a planet, in conjunction with its’ distance from the Sun can be used to determine the gravitational field of the planet. A planet with less surface area but a higher level of iron will be closer to the sun than a planet with a greater surface area and a lesser amount of iron.

It is not reasonable to use the same formulas that are used to calculate the moon’s travel round the earth when calculating the forces that cause the planets to travel around the Sun.

Where can I go to find more information concerning this subject?
 

Answers and Replies

  • #2
HazZy
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WHAT!?
 
  • #3
Originally posted by HazZy
WHAT!?

Yeah, what he said.

Someone will correct me if I'm wrong, certainly...

Gravity is related to MASS, is it not? I was always taught that gravity was a force of attraction between any two massive bodies, which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

So, the sun has mass, doesn't it? The planets have mass, don't they? So should there not be a gravitational attraction between the massive object (sun) in the center of the solar system and the massive, but less so, objects in orbit around it (planets)?

As far as comparing the sun to an atomic bomb, what is the mass of the explosion of an atomic weapon at it's peak? How long does that peak last? For that period of time, would the atomic weapon not have a gravitational effect on the Earth in relation to that mass?
 
  • #4
So - it appears that this is an incomprehensible topic? Something no one has considered? That is bizarre! It makes perfect sense that the Sun is pushing the planets into space.
The Sun is a gaseous object. How much mass can there be in that?
When I was at the planetarium in Boston, the scientist said that if one atom of iron materialized in the Sun, the Sun would collapse in seconds. Is there truth to that?
 
  • #5
HazZy
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Originally posted by Bill Gavlas
The Sun is a gaseous object. How much mass can there be in that?
1.989e30 kg, it contains over 99% of our solar systems mass.
 
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  • #6
When I was at the planetarium in Boston, the scientist said that if one atom of iron materialized in the Sun, the Sun would collapse in seconds. Is there truth to that?

That, I wouldn't know.

The Sun is a gaseous object. How much mass can there be in that?

2 x 10^30 kg

How did I come up with that? I didn't. I used http://zebu.uoregon.edu/~soper/Sun/mass.html [Broken] as a reference.

So - it appears that this is an incomprehensible topic? Something no one has considered? That is bizarre! It makes perfect sense that the Sun is pushing the planets into space.

Incomprehensible to me, yes, but maybe I'm just dumb... If you want to go back to your atomic bomb theory, take a look at the blast area near where an atomic bomb has been detonated. Trees, phone poles, and remnants of building structures are all leaning TOWARD the epicenter of the blast, not away. Yes, the blast pushed them out, but the air rushing back after the blast dissipated pulled them back in. If the sun is pushing the planets out, as you say, then all of the other stars in the rest of the universe are pushing the planets in, and I would think that they should be able to push them into the sun or crush them where they stand (orbit, whatever).
 
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  • #7
russ_watters
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Originally posted by Bill Gavlas
So - it appears that this is an incomprehensible topic?
The topic isn't incomprehensible. Your idea is simply completely wrong. But what is incomprehensible is where the idea came from.
When I was at the planetarium in Boston, the scientist said that if one atom of iron materialized in the Sun, the Sun would collapse in seconds. Is there truth to that?
You must have misunderstood.
 
  • #8
You can't simply say my idea is wrong! That is analogous to ad hominem arguing! I need you to prove me wrong! I want to know why it is wrong! Just because you were taught that the Sun has this tremendous gravity doesn't mean that it is right! It may be tremendous gravity, but, the explosive force far outwheighs the gravity!
So what if the atomic bomb analogy isn't exactly right. There are different factors at work in space. The force from the Sun is constant, whereas, a bomb produces high pressure and low pressure events.
 
  • #9
FZ+
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Ok, consider this for a moment - where does most of the destructive power of a nuclear bomb come from?

Radiation? No.
Heat? No.

The power of the nuclear bomb comes from the shockwave it creates in the air when it explodes. This shockwave travels at the speed of sound, and that is what pushes apart buildings, flattens people against walls and other morbid things like that. Without the air to transmit the force, the only way bombs kill would be to incinerate you, or irradiate you.

Now let's look at the sun. Space has no air. Hence, it is impossible for the reaction that is the sun to generate a shockwave. It cannot exert the pushing force in this way. Heat similarly cannot be conducted or convected to us. The only thing that remains is radiation.

The sun does emit charged particles, which we call the solar wind. You can observe in in Auroras. But this effect is extremely weak, even on a body as large as the earth. Perhaps a few million newtons. The other source is direct photon pressure from the light hitting us. Given the intensity of the solar radiation, this is also tiny. Both of these are several orders of magnitude too small to be compared to the power of gravity, which is easily observable in earth's orbit.
 
  • #10
FYI - gravity is related to the density of an object rather than the mass of an object. Mass calculations cannot be used to determine the gravity of a planet. Just because Mars is bigger than the earth does not mean its' gravity is greater.

Also, we must consider relativity in all of this. We say that the force of the Sun is weak but in relation to what?

While you may speak of particles emitted by the Sun which you call Solar Wind, the earth is constantly bombarded by electrons from the Sun in the form of waves. Do you refer to these electrons as particles? Or, by particles, do you mean the protons of an atom? Or, are the particles simply free electrons that are not associated with a wave? I really don't know what is meant when someone refers to a particle.
 
  • #11
Zefram
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gravity is related to the density of an object rather than the mass of an object. Mass calculations cannot be used to determine the gravity of a planet.

Related maybe, attributable to, I don't think so.

Unless I missed the mark, Newton's law of universal gravitation looks like this:

F = GMm/r2

and F = ma

so

ma = GMm/r2

The little m's cancel out and the acceleration of gravity at some distance r from the center is equal to GM/r2.

If the massive body were more dense, the surface would be closer to its center (i.e. r would be smaller), so you'd be dividing by a smaller number (r2 would be smaller) and the acceleration at the surface would be greater.


Just because Mars is bigger than the earth...

Um.

edit// punctuation
 
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  • #12
HazZy
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Bill your making Newton toss in his grave!

Also electromagnetic waves are composed of photons, not electrons.
 
  • #13
OK - you got me with Newton's Law - but Newton came up with his law before the dicovery of Black Holes - didn't he?

I really did not want to go this deep - but - I guess I have to in order to explain this.

Newton's Law cannot be used to determine the gravity of the Sun, since the Sun is an explosive force that exerts pressure on the objects around it.

The opposite of the Sun is a Black Hole which exerts a gravitational field.

I have often read, although I cannot confirm it, that a teaspoon of the substance that exists after the collapse of a star would weigh a million pounds, or, something of that magnitude.

Now if Newton's Law were correct in all cases, how does the density of this substance since its' mass is so small gain such a weight?

And what is this substance?

And, isn't the weight of an object related to its' gravitational force?

If I could achieve a temperature that is lower than absolute zero (-451 F), which appears to be possible in space, I could strip the electrons from the proton of a hydrogen atom. What would I have if I could strip the electrons from a massive number of hydrogen atoms (which would happen if I went below absolute zero)? I would simply have the protons of the hydrogen atom left. What would happen then? Would the protons then bond? Since there are no electrons to keep them apart? Would I create a new element? Would I create a Black Hole?

Remember a cardinal rule of atomics; "Electrons flow from a greater concentration to a lesser concentration through the path of least resistance." Given that, electrons are primarily the anti-gravity part of the atom. They are held in place by the force exerted on them by the proton (and you can call that + or - I don't really care). They also insulate the proton from coming in contact with another proton.

If they were not caught in the gravitational pull of the proton, they would be heading into space as fast as possible.

I propose that; the protons of an atom are the substance that comprises the heart of a Black Hole which is colder than we can imagine. Far colder than Absolute Zero! And you can't pass through it, as has been recently proposed, without being disassembled! Element by element!
 
  • #14
enigma
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Bill,

first off, saying you are wrong is not an ad hominem argument. Saying someone is wrong because they beat their wife (e.g.) is an ad hominem.

The sun is a giant ball of hydrogen. It has a mass of ~2*10^30kg. That is HUGE. Earth's mass is 6*10^24, 1000000 times less.

The vast majority of the sun's mass is not 'an explosion'; the only part which is 'exploding' is the core. It is happening because the sun's gravity is pulling all of the hydrogen in on itself until it gets hot enough with enough pressure for the individual atoms to start merging into helium. That is what a fusion reaction is. The fusion reaction in the core 'pushes' outward, which keeps the star from collapsing in on itself.

The sun glows because the energy (in the form of photons) released from the center excites the hydrogen on the way out, which then re-releases them. Eventually, they get out of the sun's surface and travel to us.

The thing you heard about iron is correct, but for a different reason:

It is related to the life cycle of stars. When a star is born, it has well over 99% hydrogen. As the star ages, that hydrogen turns into helium. As the hydrogen in the core gets used up, the star grows into a red giant. When the hydrogen in the core is all gone, then the helium stars to fuse together into larger atoms. When the helium gets used up, the next largest atoms start to fuse (the larger the atom, the harder to fuse). This process continues until you reach iron in the core. Fusing iron together takes more energy than it releases. That means that there is no way for the star to get energy from the fusion, so there is nothing left to hold it up. Game over. The core collapses, the star around it starts to collapse. When the core collapses all the way, the sudden impact of all the mass causes an explosion called a supernova takes place. Depending on the size of the initial star, a white dwarf (our sun), a neutron star, or a black hole will form in the 'rubble'.

The particles from the sun in the solar wind are usually ions (atoms with too few or too many electrons). Those are completely different from light, which is photons.

FYI - gravity is related to the density of an object rather than the mass of an object. Mass calculations cannot be used to determine the gravity of a planet. Just because Mars is bigger than the earth does not mean its' gravity is greater.

No, gravity is related to mass. If it were related to density, the Earth would have a much stronger force of gravity than the sun and all the Jovian planets as well. Giant gas balls are not very dense.

BTW, Mars is about 40% smaller than Earth.

Don't take Star Trek as fact. Sci-fi shows would have you believe that you'll fall into a black hole just by being near it. If the sun turned into a black hole tomorrow, we'd still happily orbit it the same as we always have been (only we'd be a lot colder).
 
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  • #15
chroot
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You can't simply say my idea is wrong!
Some ideas are so plausible that one needs to prove them wrong to be confident in dismissing them. Some ideas are so clearly, unambiguously wrong that any intelligent person would realize going through a formal proof would be a waste of time.

Bottom line: we don't have to thoroughly investigate every idea pushed by every crackpot. Nearly all of them are in fact worthy of quick, thoughtless dismissal -- yours included.
The thing you heard about iron is correct
The thing he heard, "if one atom of iron materialized in the Sun, the Sun would collapse in seconds," is in fact not at all true, enigma. Iron is important in stellar physics because it is the most stable nucleus -- but the presence of iron in a star has no consequence. Only when the core is predominantly iron is there a problem.

Point of fact, our own star, among many many others, has some iron in it.

- Warren
 
  • #16
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The explosion of a bomb expands. If the gravitational force of the sun is negligable, then why does the sun not expand?

Hurkyl
 
  • #17
enigma
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Originally posted by Bill Gavlas
Newton's Law cannot be used to determine the gravity of the Sun, since the Sun is an explosive force that exerts pressure on the objects around it.

Newton's Law can be used to determine the gravity of the Sun, but only inderectly by observing the rates that things orbit around it. The formulas are actually derivations of Newtons Laws done by Kepler.

The opposite of the Sun is a Black Hole which exerts a gravitational field.

No, the black hole is what remains after a superlarge star dies.

I have often read, although I cannot confirm it, that a teaspoon of the substance that exists after the collapse of a star would weigh a million pounds, or, something of that magnitude.

That is neutron star material. After a star collapses, what is left behind depends on the mass of the initial star. If the star is small, there isn't enough gravity to keep a lot of the initial mass around. Most gets blown away in the supernova, leaving a white dwarf, which is a hot ball of whatever reached the center of the supernova first (some iron, some hydrogen, etc.)

If the mass was bigger, then the gravity holds onto the stuff through the supernova explosion, and it falls into itself. Since there is no material left to do any fusion reactions, it collapses, and collapses, and collapses, until the pressure is so big that the atoms themselves cannot hold themselves up. The electrons collapse into the protons, the space between the atoms vanishes, and you end up with a ball of neutrons the size of a large city (IIRC on the size).

If the mass was even bigger still, then there is enough mass neutrons such that the neutrons cannot even hold themselves up. They compress down and down and down until the force of gravity is so strong in the proximity to it, that light cannot escape. That fact means that the event horizon forms, and we have a brand new black hole.

Now if Newton's Law were correct in all cases, how does the density of this substance since its' mass is so small gain such a weight?

I stated it above, but I'll just go through this last post of yours. Newtons Laws are correct in all cases. The mass is huge.

And what is this substance?

Hydrogen, some helium, some trace other elements

And, isn't the weight of an object related to its' gravitational force?

The mass is. The weight is how much the gravity pulls that mass, and is equal to m*g

If I could achieve a temperature that is lower than absolute zero (-451 F), which appears to be possible in space,

You can't go lower than absolute zero. You can't even reach absolute zero. Absolute zero means there is absolutely no energy present. It is impossible to pull further thermal energy out, and keeping something at absolute zero anywhere near (like... in the universe) something not at absolute zero will cause the energy to leak into the Ab 0 substance.

I could strip the electrons from the proton of a hydrogen atom. What would I have if I could strip the electrons from a massive number of hydrogen atoms

A whole bunch of hydrogen ions. :wink:

I would simply have the protons of the hydrogen atom left. What would happen then? Would the protons then bond?

Not unless you heated them up to a few million degrees. The + charges repel (a LOT), and it takes a lot of thermal energy (which is just an average of the individual molecules kinetic energy) to get them to overcome that.

Since there are no electrons to keep them apart? Would I create a new element? Would I create a Black Hole?

The electrons don't keep them apart. The electrons balance the charge, and allow complex molecules to form by electron 'sharing' between them.

Remember a cardinal rule of atomics; "Electrons flow from a greater concentration to a lesser concentration through the path of least resistance." Given that, electrons are primarily the anti-gravity part of the atom. They are held in place by the force exerted on them by the proton (and you can call that + or - I don't really care). They also insulate the proton from coming in contact with another proton.

That is not how QM or atomic reactions work, but the actual effects are out of my realm of knowledge.

If they were not caught in the gravitational pull of the proton, they would be heading into space as fast as possible.

It's actually the coulomb (electrical) force which keeps the electrons close by. Gravity is way too small to hold an electron near. The reason it holds planets in an orbit is because A) it acts over much larger distances than electricity, and B) It always attracts. Electricity both attracts and repels.

I propose that; the protons of an atom are the substance that comprises the heart of a Black Hole which is colder than we can imagine. Far colder than Absolute Zero! And you can't pass through it, as has been recently proposed, without being disassembled! Element by element!

You can't pass through a black hole.
 
  • #18
enigma
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Originally posted by chroot

The thing he heard, "if one atom of iron materialized in the Sun, the Sun would collapse in seconds," is in fact not at all true, enigma. Iron is important in stellar physics because it is the most stable nucleus -- but the presence of iron in a star has no consequence. Only when the core is predominantly iron is there a problem.

Point of fact, our own star, among many many others, has some iron in it.


I know that, warren. I did explain the phenomena, didn't I?

I also know that he misunderstood or misenterprited what was told to him, and a previous poster said that there was no truth to it at all, which is incorrect.
 
  • #19
HazZy
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Now if Newton's Law were correct in all cases
remember, newtons laws of motion (F=ma) break down at high speeds and ALL laws of physics break down at the singularity. we simply don't know what exactly is going on past the event horizon of a black hole (but we make a lot of guesses :wink:).
 
  • #20
LURCH
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Non-magnetic objects (asteroids without metal in them, big balls of water-ice, old astronaut gloves)orbit the Sun, the same way planets do.
 
  • #21
It is OK if you disagree with me. That is how we learn. I really want to thank everyone who has responded to this Post.

What I presented was merely an alternative to what we have been taught through the years. Right or wrong? I don't know. You have provided some excellent responses and a lot of food for thought. But you have still not given me what I wanted. Proof that what I proposed was simply not true!

There are a lot of forces in the universe that we can barely comprehend. To liken the output of the Sun to the campfire is a mistake. But even a campfire exhibits tremendous forces. You can float to the edge of the atmosphere with the energy of fire (in a hot air ballon).

You can say that it is not even worth considering the concept, but, that is your loss. Perhaps there is some logic in it if you would comprehend the thought that the rules are different for planets and stars. But then, I really don't know.

I would like to thank WazZy for bringing up the topic of Photons as opposed to electrons. I don't deny that Photons exist, but their role in electromagnetics is something I cannot comprehend as yet.

This really is a topic for another forum, but electromagnetics deals with the movement of electrons and not Photons. Electricity is produced by moving electrons through a piece of conductive material (i.e. copper). Everything on the electromagnetic spectrum can be reproduced using electricity. Unless you can explain a simple conversion from Photon to Electron and vice versa, then I'm lost! Since we can produce light and heat with electricity and electricity is simply electrons, how does a Photon get produced? Unless you have a very simple explanation, please don't try to answer that question.

Since I can melt iron with electrical energy, or, a gas, or, coal, or wood, where is the physical difference in the process?

Like I said, it is a topic for another forum.
 
  • #22
HazZy
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well first of all it's HazZy :wink:. secondly, FZ+ explained clearly why your theory wouldn't work. forces need a medium to travel through, be it gas/liquid/solid. we would experience forces from the sun if we were a great distance closer to it(we'd be burnt to a crisp long before we got close enough), but feeling the force from the explosions of the sun at our current distance would be like feeling the force from a nuclear bomb detonated on the moon, it just doesn't happen. it's good to stick with your theories, but when you have several laws of physics against you it's time to give up.
 
  • #23
Janus
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Originally posted by Bill Gavlas
But you have still not given me what I wanted. Proof that what I proposed was simply not true!

The proof lies in the fact that the planets orbit the sun with periods that exactly match The orbits predicted due to the force of gravity form the sun, as do comets, asteroids, etc.

The proof also lies in the fact that we can launch space probes from the Earth and have them arrive at the destination planet with great accuracy. The trajectories of those probes are calculated by taking into account the gravity of the Sun.

For your idea to be correct, neither of the above would be true. Your system would lead to a Planets that orbit much differently than they do, and space probes that miss the planet they are aimed at by wide margins.


[quote
Unless you can explain a simple conversion from Photon to Electron and vice versa, then I'm lost! Since we can produce light and heat with electricity and electricity is simply electrons, how does a Photon get produced? Unless you have a very simple explanation, please don't try to answer that question.

Since I can melt iron with electrical energy, or, a gas, or, coal, or wood, where is the physical difference in the process?

[/QUOTE]

When electrons(or anything with a charge) accelerate(such as when they vibrate), they give off energy in the form of photons. As electrons push through a conductor they "stick" a little to the atoms of the conductor, which cause these atoms to vibrate. Since the atoms contain charges, they shed this energy of vibration in the form of Photons. The more energetic the vibration, the higher the energy (and frequency) of the photons. First you get low energy photons alone ( far-infrared) then you start to add near-infrared, red, orange, etc. (the conductor will begin to glow). As the conductor gets hotter, it adds more colors until it is emitting all of the visible spectrum and it will be "white hot" .

When you use a flame to heat an object up, the only difference is in the manner in which the atoms are made to vibrate. (Of course if they vibrate too much, they will break the bonds holding them together, and your object being heated turns to liquid, and many subtances liquify(or become gasses ) long before they get to the "glowing" stage.)
 
  • #24
Thank You Enigma! I can't believe it took so long to get to the point where someone would admit that their is a difference between calculating the gravity of a planet as opposed to calculating the gravity of a star.

In your post, you say that Kepler had to derive rules for calculating the gravity of the sun from Newton's Laws. Kepler accounted for the factors that are different in a star as opposed to a planet.

The gravity of a star is offset by the outward force it is exerting on the objects that are near enough to be affected by the solar blast.

I never said that we could not calculate the effect, but Enigma admitted that Newton's Law had to be modified by Kepler to account for the difference. We must keep in mind that our formulas are relative to what we experience and built in adjustments are automatic based on what we see from our tiny little planet.

We do seem to have difficulty calculating the gravity of Mars correctly. It appears that Newton's Laws may have to be adjusted for Mars as well.

But, if we ever do travel to other solar systems, we do need to account for the difference in the output of the sun, in that system as opposed to the gravity or mass of the sun.
 
  • #25
Zefram
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Bill, here's a short activity on what I believe enigma was referring to, if you're interested: http://imagine.gsfc.nasa.gov/YBA/cyg-X1-mass/mass-of-sun.html [Broken].
 
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  • #26
Janus
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Originally posted by Bill Gavlas


In your post, you say that Kepler had to derive rules for calculating the gravity of the sun from Newton's Laws. Kepler accounted for the factors that are different in a star as opposed to a planet.

The gravity of a star is offset by the outward force it is exerting on the objects that are near enough to be affected by the solar blast.

I never said that we could not calculate the effect, but Enigma admitted that Newton's Law had to be modified by Kepler to account for the difference. We must keep in mind that our formulas are relative to what we experience and built in adjustments are automatic based on what we see from our tiny little planet.


BIG problem here :

Kepler, Johannes: born 1571 , died 1630

Newton, Isaac: born 1642, died 1727

It would be a little difficult for Kepler to have modified Newton's laws, when Newton wouldn't even be born until 12 years after Kepler's death.

The fact is that Kepler's laws were derived through pure observation.

Newton's laws of gravitation were then developed indendentally shown to be in perfect agreement with Kepler's observations.

Example:

Kepler's second law, " The radius vector of easch planet passes over equal areas in equal periods of time" or the 'Law of Areas" . Was porven through the " Theorum of areas" where Newton was able to prove that a body being acted on a single center-acting force would sweep out eqaul areas in equal times . (I will not repeat the theorum here as it requires a number of graphics. But it is air tight.)

Kepler's Third law, " The cubes of the mean distances of any two planets from the sun are to each other as the square of their periodic times, OR ,
a1³/a2³ = p1²/p2²
This is also known as the "Harmoinic law"

Newton arrived at this same conclusion allong the following:

Force of gravity
Fg = GMm/r²

Centripetal force needed to hold mass 'm' moving at a speed of 'v' in a circular path
Fc = mv²/r

For for a body of mass 'm' orbiting a bocy of mass 'M'

Fg = Fc, therefore;

GMm/r² = mv²/r

solving for v we get:

v = [squ] (GM/r)

The circumference of this orbit is

C = 2r[pi]

so the period of the orbit would be

p = 2r[pi] /[squ] (GM/r) which reduces to

p = 2[pi] [squ](r³/GM)

If we want to compare the periods of two bodies at different distances form body "M" we get

p1 = 2[pi] [squ](r1³/GM)
and
p2 = 2[pi] [squ](r2³/GM)

dividing them into each other we get:

p1/p2 = 2[pi] [squ](r1³/GM)/2[pi] [squ](r2³/GM)

the '2[pi]'s cancel out

p1/p2 = [squ](r1³/GM)/ [squ](r2³/GM)

Square both sides:

p1²/p2² = (r1³/GM)/ (r2³/GM)

the 'GM's cancel out:

p1²/p2² = r1³/ r2³ or

r1³/r2³ = p1²/p2²

For a circular orbit r is the mean orbital distance so r = a, thus:

a1³/a2³ = p1²/p2²

(you can also use calculus to show that this alos holds for non- circular orbits.)

Newton gets the same answer as Kepler, via a different method. Theory meets observation and agree.

All of our orbital caculations are based on the above, and they always come out correctly, match actual observation, and produce accurate practical results.

We use the same formula to place a satellite in orbit around the Earth as we use to get a probe from Earth to Jupiter, and they work in both cases.
Ergo, there is no difference in the way an object orbits a planet and the way it orbits a Sun or star.
 
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  • #27
enigma
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Originally posted by Bill Gavlas
Thank You Enigma! I can't believe it took so long to get to the point where someone would admit that their is a difference between calculating the gravity of a planet as opposed to calculating the gravity of a star.

No. You are misunderstanding. If you don't understand something clearly, you really do need to check with the person who told you before you go off prattling your new facts.

In your post, you say that Kepler had to derive rules for calculating the gravity of the sun from Newton's Laws. Kepler accounted for the factors that are different in a star as opposed to a planet.

There are no factors different in a star's gravity as opposed to a planet's, Bill. He derived the rules for calculating the a planet's (or satellite's orbit) from F=ma.

F=ma doesn't give enough information to tell the path of a planet.

You need to do several manipulations to get the position and velocity as a function of time.

The gravity of a star is offset by the outward force it is exerting on the objects that are near enough to be affected by the solar blast.

No. The solar wind is totally insignificant compared to the force of gravity. TOTALLY insignificant.

I never said that we could not calculate the effect, but Enigma admitted that Newton's Law had to be modified by Kepler to account for the difference. We must keep in mind that our formulas are relative to what we experience and built in adjustments are automatic based on what we see from our tiny little planet.

No I didn't. I said that F=ma needs to have some calculations done to give well-documented elliptical results. I NEVER said that there was a difference in the force of gravity based on what is acting.

We do seem to have difficulty calculating the gravity of Mars correctly. It appears that Newton's Laws may have to be adjusted for Mars as well.

No we don't. No they don't.

But, if we ever do travel to other solar systems, we do need to account for the difference in the output of the sun, in that system as opposed to the gravity or mass of the sun. [/B]

Really Bill, I'm losing my patience with you. You continue to claim that a star has this large outward 'explosive' force. I (and others) have pointed out where you were misunderstanding things, but you are still clinging to it. You now are saying that I have validated your ideas, when you know damn well I did absolutely nothing of the sort.

The modifications to Newtons laws are not modifications along the lines of: "Okay... maybe it's F=2ma"

They are calculus derivations converting the linear equation: F=ma into the position and velocity of orbiting satellites as a function of time. F=ma still applies, it's just been converted to deal with special case situations.

*************************************************

Thank you for the correction, Janus. That's what comes when you're taught the Newton->Kepler derivations... the little details like "Kepler didn't do this, his calculations gave the same results as Newton, but didn't provide a cause" get brushed to the wayside.
 
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  • #28
HazZy
101
0
newtons laws were never derived by kepler, it was the other way around. (edit: you guys post too quick! :smile:)

and bill, you're way off base bud.
 
  • #29
russ_watters
Mentor
21,863
8,829
I'm really starting to think this whole thread is a joke. The guy knows enough of the terms that he should understand what they mean, but is throwing them around so (seemingly) randomly I think he's doing it on purpose. Unless of course he's 13 in which case maybe he's just saying words he's heard but hasn't leaned yet (however there are a couple of damn smart 13 year olds on this board). So its possible he hasn't learned any physics yet and is just trying to invent it hemself with no starting information.

Bill, if you truly are tring to figure this stuff out, I'm not sure we can cover all of high school physics in one thread. I suggest you start searching the web for things like "newtonian physics."
 
  • #30
FZ+
1,599
3
I'll make a summary to try and clarify a bit.

Point 1.
Newton's laws are that of UNIVERSAL gravitation. The same law applies to all matter. Einstein's addentum in Relativity is to correct for very high velocities, or very strong gravitational fields. In most cases, the approximation of classical gravitation is sufficient. This does not mean the gravity is the only force in play. But rather the success of models that considers only gravity signifies gravity's dominance in such cases.

Point 2.
Gravity is a function of mass only. However, black holes exist because of their density. The black hole matter is neutronium, or quark soup. Photons repel too much to form a stable solid, while neutrons are held together strongly by the strong nuclear force.

Point 3.
The explosive force of the sun is imperceptible in comparison to that of gravity. This has been repeated shown by experiments involving solar sails etc, and can be demonstrated by measurement. No conventional shockwave can exist in a vacuum, and photons/solar wind are too weak. The sun is a nuke in space. Nukes are relatively harmless in space. That's why we have not been torn apart yet.
Force pushing away <<<<<<<< Effective force pulling
This is further incompariable to the camp fire, as that is an effect of buoyancy from low density in a higher density medium.

Point 4.
F does not equal ma. Newton's second law states that F = the rate of change of momentum (mass *velocity) This simplifies to F = ma when mass is constant. A computer algorithm can model the solar system using F=ma and newton's law of gravity to reasonable accuracy. But to get, say the function of the ellipse or the angular momentum of planets, sophisticated calculus based methods must be used.

Point 5.
Electrons can indeed be converted into energy by annihilation with a positron. The reverse can also occur. But conventionally, the photon given out is a factor of the energy CARRIED by the electron, which emerges as a self propogating energy wave/partical duality. Photons are packets of mutually supporting electric/magnetic fields. They also act as the agents behind ALL electromagnetic interactions.

Point 6.
The fundamental forces of the universe have been shown to be functions of Gravity, Nuclear Strong and Electroweak forces. You cannot postulate additional forces without justification, in terms of actual evidence.

Point 7.
Quantum wave particle duality refers to things having the properties of BOTH conventional particles (momentum, discrete existence etc), and conventional waves (wavelength etc). The fact electrons exhibit wave particle duality does not remove their particle characteristics.

Point 8.
Relativity refers to reference frames. For this the reference frame is earth, or our defined unit of the newton. Relativity does not negate measurements.

Point 9.
In atomic situations, electrons have insignificant mass to make gravity a factor. But they have real postive mass that can be shown by experiments to change their momentum. They are most definitely not anti-gravity. The EM attraction is governed by F = k * q * Q / r^2 where q and Q are the charges of the two particles, and k is derived from a fundamental constant. This is completely different from gravity as (a) mass is not a factor, (b) it is dipolar and (c) it has no effect on spacetime.

Point 10.
Heat is just another way of saying kinetic energy of particles (ie. molecule/atoms), or a measure of entropy in a system (irrelevant in this context)
 
  • #31
drag
Science Advisor
1,100
1
Greetings !

If I may, I'd like to try my own sum up.
Bill, you're saying that the fact a star
explodes should alter its gravitational
effects. Well, on Earth when an explosion
occurs there are shock waves passing through
the air (air fluctuations) that TRANSMIT the
force. In space there is no air or other
particles in any reasonable amount to
really affect something.

Now, the Sun does produce the solar wind and
EM radiation. The solar wind changes but next
I'm about to calculate the pressure of the
EM radiation and I think the pressure of the
solar wind is ussualy at least even less than
that or at least not much greater.
Now, at Earth's distance from the Sun
each square meter receives about 1,400 watts.
Although some of it is reflected and some
of it goes into non-elastic processes let's
just treat it all like in the case of
a simple elastic collision.
We know :
R = 6.4 * 10^6 m
E = 1,400 J
thus : A = 1.286 * 10^14 m^2
and according to E = M * c^2 :
M = E * A / c^2 = 2 kg
so the momentum = M * c = 6 * 10^8 N * sec
and even multiplying that by a factor
of two (to account for the solar wind and
whatever) the centrifugal acceleration
increase of the Earth is so small that
for 4.5 billion years and considering the
Sun is less active today it's still just
a few tens of meters.

In conclusion, who cares it's one huge
explosion ?! Gravity rules ! :wink:

Live long and prosper.
 
  • #32
Andre
4,509
74
What a fantastic thread this is. So we have a dispute on how gravity works. Here is the view of PC Klein, that I found somewhere else on the net (credit to (Q)):

When a cat is dropped, it always lands on its feet, and when toast is dropped, it always lands buttered side down. Therefore, if a slice of toast is strapped to a cat's back, buttered side up, and the animal is then dropped, the two opposing forces will cause it to hover, spinning inches above the ground.

If enough toast-laden felines were used, they could form the basis of a high-speed monorail system.

In the buttered toast case, it's the butter that causes it to land buttered side down - it doesn't have to be toast, the theory works equally well with Jacob's crackers. So to save money you just miss out the toast - and butter the cats.

Also, should there be an imbalance between the effects of cat and butter, there are other substances that have a stronger affinity for carpet.

Probability of carpet impact is determined by the following simple formula:

p = s * t

where p is the probability of carpet impact s is the "stain" value of the toast-covering substance - an indicator of the effectiveness of the toast topping in permanently staining the carpet.

Chicken Tikka Masala, for example, has a very high s value, while the s value of water is zero.

t indicates the tone of the carpet and topping - the value of p being strongly related to the relationship between the colour of the carpet and topping, as even chicken tikka masala won't cause a permanent and obvious stain if the carpet is the same colour.

So it is obvious that the probability of carpet impact is maximised if you use chicken tikka masala and a white carpet - in fact this combination gives a p value of one, which is the same as the probability of a cat landing on its feet. Therefore a cat with chicken tikka masala on its back will be certain to hover in mid air.

Therefore, the monorail system should be powered by cats smeared with chicken tikka masala floating above a rail made from white shag pile carpet.

Author: PG Klein.
 
  • #33
Originally posted by Bill Gavlas
You can't simply say my idea is wrong! That is analogous to ad hominem arguing! I need you to prove me wrong! I want to know why it is wrong! Just because you were taught that the Sun has this tremendous gravity doesn't mean that it is right! It may be tremendous gravity, but, the explosive force far outwheighs the gravity!

Sorry if this has already been said, but I don't have time to read all the replies. Anyway, gravity balances the outward pressure of the extremely hot particles and nuclear reactions, and when gravity isn't strong enough to counteract the inner forces of the star, it explodes (in short). What's to explain?
 
  • #34
maximus
495
4
Originally posted by Bill Gavlas

Where on earth did this concept of the sun’s gravity come from?

In case we have forgotten, the Sun is an enormous explosion. To say that it has gravity is inconsequential to the outward forces it exerts on the planets. It would seem to me that trying to measure the gravity of the Sun would be like trying to measure the gravity of an atomic bomb as it explodes. The gravitational field of the bomb casing is nothing compared to the outward force that the bomb produces.

The Sun’s gravitational field is negligible compared to the outward (anti-gravity) forces that it exerts on the planets that travel around it.

So, if the Sun is essentially pushing the planets out into space, how do the planets stay where they are in orbit about the Sun?

Iron, the metal that comprises at least some portion of the core in any planet, is attracted to electricity. The primary output of the Sun is electricity! The planets stay in orbit around the Sun due to the attraction of the planets to the Sun and not the gravitational pull of the Sun!

From time to time, you can visit the vacuum cleaner department of a major department store and see that they will have a beach ball floating in the air that is being exhausted from the vacuum. This is not proof that the vacuum cleaner is any better than any other vacuum, since it does not take a lot of air pressure to cause the beach ball to float, but it is an attention grabber to get you to notice the vacuum cleaners.

The beach ball is affected by the gravitational pull of the earth, yet it is suspended in space by the force of the air exhausting from the vacuum. The picture this produces is exactly the same way the planets and the Sun are related. The planets are attracted to the electrical output of the Sun, yet the Sun is forcing the planets into space by the sheer force of its’ explosive power.

A number of interesting observations can be made when viewing the relationship of the Sun to the planets in this manner.

First of all, the collapse of the Sun will occur much sooner than previously estimated. As the force of the Sun diminishes over time, Mercury will enter the outer edges of the Sun, and, if the surface of the Sun is not hot enough to vaporize the entire planet and blast its’ element back into space, Mercury will then initiate the collapse of the Sun. If the Sun is strong enough to blast the Mercurial elements into space, then Venus may be the culprit to cause the collapse.

Secondly, it is easy to calculate the density of a planet, thereby calculating the gravity of the planet. The surface area of a planet, in conjunction with its’ distance from the Sun can be used to determine the gravitational field of the planet. A planet with less surface area but a higher level of iron will be closer to the sun than a planet with a greater surface area and a lesser amount of iron.

It is not reasonable to use the same formulas that are used to calculate the moon’s travel round the earth when calculating the forces that cause the planets to travel around the Sun.

Where can I go to find more information concerning this subject?


there are so many errors here i don't know where to begin. first an answer to the first question: "Where on earth did this concept of the sun’s gravity come from?" uhhh, on observation of our orbit around the sun.

next: the outward force of the sun "pushing" the planets around it? wrong. it's the gravity.

you know, i give up. basically everything you said is without any scientific backing and wrong.
:wink:
 
  • #35
russ_watters
Mentor
21,863
8,829


Originally posted by maximus
there are so many errors here i don't know where to begin. first an answer to the first question: "Where on earth did this concept of the sun’s gravity come from?" uhhh, on observation of our orbit around the sun.

next: the outward force of the sun "pushing" the planets around it? wrong. it's the gravity.

you know, i give up. basically everything you said is without any scientific backing and wrong.
:wink:
This SOOOO did not need to be resurrected.
 

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