Geocentrism is correct.

[Eclogite]

I hope you know what you are talking about because I don't have the slightest clue

Only an Australian could appear smarter by confessing his ignorance.:cup:

I love it.

 

[bystander 1: Aren't his clothes magnificent?

Bystander 2: Absolutely.

Aussie: Stone me. The blighter's starkers!

 

With apologies to Hans Christian Anderson.]

[CraigD]

Then in theory, if you drop two different bodies of mass, they should fall at different rates. If acceleration is based on the bodies' mass.

If you drop two bodies of different mass toward the same large “central” body, they fall at exactly the same rate. If you drop the same small body toward two large bodies of different masses (eg: Earth vs. the Moon) it falls at different rates. Also, if you “drop” the same large body (eg: Earth) toward two different small bodies (eg: a 1 kg rock vs. a 2 kg rock), if falls at different rates.

 

Consider a large body – let’s call it “Earth”, with a mass of about 6*10^24 kg - and 2 smaller bodies – let’s call them “big rock”, with a mass of 2 kg, and “little rock”, with a mass of 1 kg – both at a distance slightly – let’s say 19.6 meters - above the surface of the Earth – about 6380000 m from Earth’s center.

 

Consider the system consisting of just Earth and little rock. The force on Earth toward little rock and little rock toward Earth is about:

G*M1*M2 / r = 6.672*10^-11 * 6*10^24 * 1 / 6373000^2 = about 9.8 kg*m/s/s.

The acceleration of little rock toward Earth, then, is: 9.8/1 = 9.8 m/s/s.

The acceleration of Earth toward little rock is a tiny: 9.8/6*10^24 = about 1.6*10^-24 m/s/s.

 

Consider the system consisting of just Earth and little rock. The force on Earth toward big rock and big rock toward Earth is about:

G*M1*M2 / r = 6.672*10^-11 * 6*10^24 * 2 / 6373000^2 = about 19.6 kg*m/s/s.

The acceleration of big rock toward Earth, then, is: 19.6/2 = 9.8 m/s/s.

The acceleration of Earth toward big rock is a tiny: 19.6/6*10^24 = about 3.2*10^-24 m/s/s.

 

Note that big rock and small rock experience exactly the same acceleration toward Earth. Note that Earth accelerates toward big rock at exactly twice the rate that it accelerates toward little rock.

 

From this we can conclude that, for the Earth – big rock system, the 2 two bodies would actually collide in slightly less time than for the Earth – little rock system. The difference, however, in tiny:

Time = (2*distance/acceleration)^.5 = about (39.2/9.8)^.5 = 2 seconds

[math]\Delta[/math]Time = (39.2/(9.8 + 1.6*10^-24))^.5 - (39.2/(9.8 + 3.2*10^-24))^.5 = about 0.000000000025 seconds

 

If, instead of little rock and big rock, we use much larger “small” objects – let’s call them Mercury, mass 3.3*10^23 kg and Mars, mass 6.4*10^23, and calculate how long it takes them to collide with the earth if dropped from a same height as before (for simplicity, we’ll assume, unrealistically, that Mercury and Mars, though very massive, have the same diameter as little and big rock), the difference will be more noticeable:

Mercury’s acceleration toward Earth = about 9.8 m/s/s

Mars’s acceleration toward Earth = about 9.8 m/s/s

Earth’s acceleration toward Mercury = about .5421 m/s/s

Earth’s acceleration toward Mars = about 1.051 m/s/s

So,

Mercury collides with Earth in (39.2/(9.8 + .5421))^.5 = about 1.946 seconds

Mars collides with Earth in (39.2/(9.8 + 1.051))^.5 = about 1.901 seconds

[arkain101]

-Geocentrism is correct

-Geocentrism as an Absolute is incorrect, and likewise Heliocentrism as an Absolute is incorrect as well. They are relative truths.

 

Further the Mean-centrism is also a relative truth. Mean-centrism is the view that everything orbit's around a common attraction point, which I forget how it's found but it's part of the n-Body gravity systems

 

 

Imagine a black hole light years away rotating around the earth every 24 hours!

 

First the black hole can not contain the same mass that it does. The earth would have to. But the earth does not as we can test and understand.

 

Let alone billions of stars and sun moving faster than the speed of light around the earth.

 

Being that geocentrism can not obey the laws of physics as understood, it can not be more than relative percievable truth. It surely is not a relative possibility. With this said, it does appear there is such thing as some type of absolute in a relationship between two things C motion and C inertia C^2 interaction max.

[Michaelangelica]

If you drop two bodies of different mass toward the same large “central” body, they fall at exactly the same rate. If you drop the same small body toward two large bodies of different masses (eg: Earth vs. the Moon) it falls at different rates.

If, instead of little rock and big rock, we use much larger “small” objects – let’s call them Mercury, mass 3.3*10^23 kg and Mars, mass 6.4*10^23, and calculate how long it takes them to collide with the earth if dropped from a same height as before (for simplicity,

Dropped from where?

[IDMclean]

Question. In a closed system, with two bodies of mass at a given distance. With equal, or disportionate mass. Would not the acceleration towards one another be equal, from each one's frame of reference?

 

That is to say to the sun it appears that the earth is accelerating towards it, and the sun is stationary. For the Earth it appears exact in opposite. Which one is correct? Relativity says both, as I understand it.

[CraigD]

If you drop two bodies of different mass toward the same large “central” body…

Dropped from where?

From about 19.8 meters above the Earth’s surface, which is about 6380000 m from its center, the same as in the previous examples with “big rock” and “little rock”.

[IDMclean]

[math]T_{earth}^2 = \frac{4\pi^2}{Gm_{sun}}r^3[/math]

[math]T_{sun}^2 = \frac{4\pi^2}{Gm_{earth}}r^3[/math]

[CraigD]

In a closed system, with two bodies of mass at a given distance. With equal, or disportionate mass. Would not the acceleration towards one another be equal, from each one's frame of reference?

That depends on precisely how one defines “acceleration”.

 

If one defines it at the rate of change in the rate of change in the distance between the 2 bodies, then yes, both bodies measure the same “relative acceleration.” If one measure it relative to distant objects less affected by either body’s mass (which is technically cheating, if the 2 bodies are truly a “closed system”) or by carefully measuring the force experienced in the direction of the other body, using a sensitive accelerometer, of indirectly (for example, by measuring the body’s ocean tides), one can determine what component of the relative change in distance is due to your body’s acceleration toward the other, and the other’s toward yours.

 

This simple example applies to objects that are either falling toward one another, or orbiting one enough with very high orbital eccentricity. For nearly circular orbits like the Earth-Sun’s, however, the mutual centripetal force due to gravity can be calculated by using the same methods, even though it doesn’t correspond to the distance between the 2 bodies.

That is to say to the sun it appears that the earth is accelerating towards it, and the sun is stationary. For the Earth it appears exact in opposite. Which one is correct?

The Earth is accelerating toward the Sun at about 333000 times the rate that the Sun is accelerating toward the Earth. This can be determined from an observer moving with either body, in orbit around either body, or in an effectively unrelated inertial frame (such as an observer on a planet orbiting a distant star).

Relativity says both, as I understand it.

General Relativity’s Equivalence Principle says only that an experiment carried out locally – without the ability to measure distant objects – can’t determine if it is traveling in a straight line, falling toward, or orbiting another body. By the principle, an experiment confined to an infinitely small point on the surface of the Earth can’t determine that the Sun, any other body exists, or even the Earth itself, exists. The experiment can detect a force due to the gravitational attraction of the Earth, the Sun, or any other body, but it can’t determine that that force is due to gravity, created by a mechanical traction motor, a rocket engine, etc.

 

In researching this post, it noted that the wikipedia article “Equivalence principle” lists many usages of the term, including “the weak equivalence principle,” reading “All bodies at the same spacetime point in a given gravitational field will undergo the same acceleration”. Note that this doesn’t say “two bodies in different spacetime points in different gravitational fields will undergo the same acceleration”.

[Michaelangelica]

Sorry

I give up.

This thread is beond my understanding.

[Qfwfq]

Only an Australian could appear smarter by confessing his ignorance.

I guess I must be quite a dumb ***, because I got what KAC meant by the sentence that Michaelangelica had quoted. However, I got the impression that KAC wasn't aware that Boerseun and Jay-Qu were talking about the same thing! :hihi:

[Qfwfq]

That depends on precisely how one defines “acceleration”.

;)

What it depends on is which system of reference one chooses. As KAC says, that's what relativity is all about, and the point of GR is that of not being restricted to a restricted class of them.

 

It's all a very subtle matter... :P :hihi: :evil:

[CraigD]

Sorry

I give up.

This thread is beond my understanding.

It's all a very subtle matter... :D :hihi: ;)

It’s possible that we’re making this thread more subtly and opaque than it need be.

 

The old geocentric theory for the motion of the planets predicted that an observer far off in space, looking down on the plane of the orbit of the planets, would the various bodies orbiting the Earth, looking something like this:

 

The heliocentric theory predicts that you’d see the planets orbiting the sun, loking something like this:

Without the Earth being so big – Copernicus, and Andreas Cellarius, the guy who made this beautiful illustration 120 years after Copernicus, only had the basic arrangement, not the scale, correct.

 

We can (and have, with the out-of-the-ecliptic-orbiting Ulysses spacecraft) look at the solar system, and it looks heliocentric.

 

To resolve geocentrism with the law of universal gravitation – which bench-top experiments have demonstrated is correct – we’d have to predict that the Earth’s mass is many thousands of times that of the Sun or any of the other planets. Based on modern data from many different sources and scientific disciplines, this isn’t the case.

 

The simple picture described by Heliocentrism isn’t exactly correct – a far-off observer looking down on the solar system would, with sufficiently sensitive instruments, be able to detect a substantial wobble of the Sun, showing that it isn’t truly stationary, but itself orbiting around a complicated and changing center of gravity with the other planets (the Sun orbits roughly around a point about 300,000,000 m, or about 7% of its diameter, above its surface, in the direction of Jupiter) – but it’s pretty close. The old Geocentric model isn’t even vaguely what a distant observer would see.

 

I think this tread, and other sites like the ”Catholic Truths” markjwatts pointed out, make the issue confusing by resurrecting the term “geocentricism” to use it in the very different context of Relativity. Though it’s not inaccurate to say “Relativity makes any point the center of everything”, Relativity doesn’t invalidate the generally accurate description of the solar system made by the heliocentric model, or suggest that geocentricism should not have been discarded in favor of it. When it comes to reasonably accurately describing the motion of the solar system, the heliocentric model is just fine.

[IDMclean]

Fair description, and perhaps I didn't understand the difference of Relative Earth versus Geo Centric. My point was however, that from any inertial frame, of a small number of orbiting bodies system, it will seem like all other bodies of the system are orbiting about each other, and/or about the inertial frame of reference.

 

However if you find the Common Attraction point (of the system), and use that as your Inertial Frame you will find all bodies orbiting about that point.

 

Here is a Hypothesis, based on that understanding:

If we know the whole universe, then we should be able to find the universal attraction point. Therefore we should be able to observe the universe from that point.

[CraigD]

Here is a Hypothesis, based on that understanding:

If we know the whole universe, then we should be able to find the universal attraction point. Therefore we should be able to observe the universe from that point.

To test this hypothesis, we first need to define “attraction point”.

 

A simple, classical mechanical definition, going back nearly as far a Kepler, is that an attraction point is the focus of the conic sectional (elipse, etc.) path that a body follows, if that body’s not subjected to some force other than the gravitational one toward that point. This definition works well if there are only 2 bodies in the system, or if there are many bodies, but one of them is much larger than the others, allowing us to consider each large-small body pair to be in a separate 2-body system. It also requires that each body be a “point source” – mass with zero diameter – or that the diameters of the bodies are so small compared to the space between them that we can consider them to be points. This is roughly the case for the solar system (big Sun, small planets), or most planetary satelite systems. It works adequately, but less well for close-in satellites, such as artificial ones in Earth orbit.

 

It’s not exactly correct, however. Each planet doesn’t exactly follow an ellipse focused at the same point in space (near the Sun), and satellites follow roughly follow ellipses far away from this point.

 

So even though any system consisting of a finite number of bodies has a center of mass, it’s not very useful, then, to consider this point to be a “system/universal attraction point” of special significant to every body in the system. The motion of bodies are usually dominated by their most massive neighbors, requiring the choice of specific “centers of attraction” for each large body(s)-many small body system.

 

This is further complicated by the lack of a computable (not requiring an infinite number of calculations to compute a finite interval of time) method of exactly determining the motion of 3 or more bodies of similar mass – the famous “3-body” or “n-body” equation problem. So precise gravitational mechanics require a combination of appropriate simplifying assumptions and numeric approximations. And this is just to solve them under classical mechanical law. General Relativity adds a new layer of complication to calculations (which is over my head), and likewise has no closed form for 3 or more bodies.

[IDMclean]

When I am not on lunch break I will make an effort to find the example of what I am talking about.

 

However, I don't mean simply for our solar system, nor for our galaxy. It has been claimed by some that we see the whole universe, and that it has defined dimensions. In a closed universe, as that is the kind I believe in, the number of bodies are finite, if and only if new bodies can not be generated, which I do not believe.

 

I am a severe skeptic of the Big Bang theory, universal spacetimes, and other such claims that are made from within the atmosphere of this little blue marble. I believe somewhat in blackholes, but until we observe one and poke it with a stick I will remain skeptical of them.

 

The mean attraction point is the pov about which all bodies are orbiting, relative to that point, so I purpose an experiment which will either prove or disprove the "known universal dimensions" theorem. If we have mapped the whole universe then we should be able to, eventually, calculate the mean point; therefore, w should be able to define a universal center.

[Qfwfq]

I think Craig, what he means is quite simply the centre of mass of the universe.

 

Conceptually, this is perfectly correct although not very practical. Back when I was attending the first year general physics course, there was a guy that was son of an astronomer. He occasionally tried to show off that he was a researcher's son and was somewhat a know-it-all and, when the professor had just finished discussing the topic of inertial coordinates and paused to let students ask questions, his hand shot up and stretched somewhat forward and he said, rather assertively,

"Yes, professor, shouldn't the inertial frame be placed in the c. m. of the universe?"

and then sat there looking very pleased with himself for having posed such a knowledgable query. The professor, a quite wise old man, settled back into his chair, smiled, and then said:

"You find the c. m. of the universe for us, and then we'll all

immediately

rush to put it there!"

[markjwyatt]

When I am not on lunch break I will make an effort to find the example of what I am talking about.

 

However, I don't mean simply for our solar system, nor for our galaxy. It has been claimed by some that we see the whole universe, and that it has defined dimensions. In a closed universe, as that is the kind I believe in, the number of bodies are finite, if and only if new bodies can not be generated, which I do not believe.

 

I am a severe skeptic of Big Bang, Universe Space-Time known and other such claims that are made from within the atmosphere of this little blue marble. I believe somewhat in Blackholes, but until we observe one and poke it with a stick I will remain skeptic of them.

 

The Mean Attraction point, is the pov from which all bodies are orbiting about, relative to that point. It was something I encountered while researching gravity.

 

So I purpose a experiment which will either prove or disprove the "known Universal Dimensions" theorm. If we have mapped the whole universe, then we should be able to (eventually) calculate the mean point, and therefore define universal center.

 

I think you are on the right track, and If you read my blog you will see that I talk a lot about relativistic interpretations of geocentrism. Still, ultimately, I think relativity was created to escape the reality that earth is in the center of the universe and not moving. The book, Galileo Was Wrong by Robert Sungenis, Ph.D., and Robert Bennett, Ph.D. explains this very well. In short, science has been faced with observation after observation and experiment after experiment that indicates that earth is smack dab in the center and/or not moving. Rather than explore the possibility, they have made science more comlicated to reconcile their assumptions (earth is moving and not at center) with their observations (earth is not moving and not at center). Thus we are told space is a 4-D hypercube or donut, matter shrinks in the direction of trael, etc. All these oddities cancel out the observations of earth at center and not moving.

 

Mark Wyatt