Why not the sun revolves around the Earth?

In summary, the conversation discusses why it is considered that the Earth revolves around the sun and not the other way around. It is explained that analyzing planetary motion from the Earth's frame is not wrong, but it is simpler to use the center of mass frame. The conversation also touches on the misconception of a universal frame of reference and the importance of considering different frames when analyzing motion. The use of semi-cyborg goggles as a metaphor is also mentioned.
  • #1
hackhard
183
15
why was Earth considered to revolve around the sun and nt the other way round?
why is it wrong to analyze planetary motion from Earth frame?
 
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  • #2
hackhard said:
why is it wrong to analyze planetary motion from Earth frame?
It's not wrong, but the system's center of mass frame is closer to an inertial frame, making the math simpler.
 
  • #3
I can't find it now but I remember reading somewhere about someone lamenting the supposed poor education of our kids by claiming that such-and-such percentage of kids couldn't "correctly" answer whether the Sun orbits the Earth, or the Earth orbits the Sun. However, of course, the statement "The Earth orbits the Sun" and "The Sun orbits the Earth" are equally true! They are each true in different reference frames. Of course the center of mass of the Earth-Sun system is very close to the center of the Sun. Also, it's a known fact that the Ptolemaic model is definitely not true. However, the real problem is that the public implicitly assumes that there is a universal frame of reference. Humans evolved on the surface of the Earth, where the ground you are walking on is an always present obvious frame of reference, so that shapes our psychology.
 
  • #4
A.T. said:
the system's center of mass frame is closer to an inertial frame, making the math simpler.
can you please explain how ?
 
  • #5
hackhard said:
can you please explain how ?
Look up inertial and non-inertial frames of reference.
 
  • #6
so analyzing motion from sun frame saves from worying about pseudo forces
 
  • #7
hackhard said:
can you please explain how ?
Let me explain how. As David Neves explained sun and Earth is in fact revolving around their common center of mass and to analyze this motion you also need to consider the position of the center of mass and position of sun and earth. However since the sun is much more massive than earth, the center of mass of this system is inside the sun. So we can say that the Earth is revolving around the sun(not center of sun but very close to it). So even though the center of mass is not inertial we can approximate it because in that way we can take position of center of mass constant and this makes life easier because we don't deal with a function of time anymore but a constant.
 
  • #8
Note that the center-mass frame is not precisely the rest frame of the sun, although it's very close, because the mass of the sun is much larger than the mass of the earth, but more precise is to say that both the Earth and the sun orbit around their common center of mass. The reason is that in this frame the two-body problem reduces to an effective one-body problem, namely that of a mass ##\mu=m_1 m_2/(m_1+m_2)## orbiting around the origin in a gravitational potential $$V(r)=-\Gamma m_1 m_2/r=-\Gamma \mu (m_1+m_2)/r.$$
 
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  • #9
hackhard said:
why was Earth considered to revolve around the sun and nt the other way round?
why is it wrong to analyze planetary motion from Earth frame?
If only that they can find a fixed reference in the universe, then we may able say what is moving around what. With respect to that reference, chances are the sun might be revolving around the Earth or may be the earth. What are your thoughts on this?

Is it not right that massive objects revolves around the lighter ones in a vacuum? What are the odds?
 
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  • #10
Ronie Bayron said:
Is it not right that massive objects revolves around the lighter ones in a vacuum?
depends on choice of frame
isolated particles can appear to revolve and revolving particles can appear to purely translate when viewed from certain non-inertial frames
 
  • #11
hackhard said:
depends on choice of frame
isolated particles can appear to revolve and revolving particles can appear to purely translate when viewed from certain non-inertial frames
I think Galileo was half right for that fact--(not unless rebutted by someone)
Anyhow, I admired your semi-cyborg goggles:smile:. Is it functional? Just asking.
 
  • #12
There are other planets orbiting the Sun, and the Earth is so small, so it's not very useful to consider the center of mass of the Earth and Sun. The Sun is so much more massive that you might as well neglect the mass of the Earth.
 

1. Why was it originally believed that the sun revolved around the Earth?

Before the 16th century, the ancient Greek philosopher Aristotle proposed that the Earth was the center of the universe and that all celestial bodies, including the sun, revolved around it. This belief was supported by the Catholic Church and became the dominant view in Europe for centuries.

2. How was the geocentric model eventually disproven?

In the 16th century, Polish astronomer Nicolaus Copernicus proposed the heliocentric model, which stated that the sun was the center of the universe and that the Earth and other planets revolved around it. This was confirmed by observations made by Galileo Galilei and Johannes Kepler, using the newly invented telescope.

3. What evidence supports the heliocentric model?

One key piece of evidence is the observation of the phases of Venus, which were only possible if Venus revolved around the sun and not the Earth. Additionally, the heliocentric model accurately explained the retrograde motion of planets and the varying speeds of their orbits.

4. Why did it take so long for the heliocentric model to be accepted?

The heliocentric model challenged long-held beliefs and went against the teachings of the Catholic Church. Galileo's support of the model led to his trial and house arrest by the Church, causing many to fear persecution if they openly accepted the idea. It wasn't until the 18th and 19th centuries that the heliocentric model became widely accepted.

5. Is there any evidence that still supports a geocentric model?

No, there is no scientific evidence to support a geocentric model. Our current understanding of gravity, planetary motion, and the laws of physics all point to a heliocentric model as the most accurate description of our solar system.

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