The orbital-motion tag has no wiki summary.
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1answer
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Radial fall in a Newtonian gravitational field [duplicate]
Suppose an object of mass $m$ starts at rest at a radial distance $ r_0$ from a perfectly spherical mass $M$ (where $m << M$), $r_0 > R =$ radius of $M$.
Can we analytically determine when ...
28
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1answer
442 views
Why are our planets in the solar system all on the same disc/plane/layer?
I always see pictures of the solar system where our sun is in the middle and the planets surround the sun. All these planets move on orbits on the same layer. Why?
15
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4answers
2k views
Are tidal power plants slowing down Earth's rotation?
Are tidal power plants slowing down Earth's rotation to the speed of the orbiting moon? (1 rotation per 28 cca days)
Are they vice versa increasing the speed of moon orbiting by generating some ...
12
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2answers
1k views
What did general relativity clarify about Mercury?
I frequently hear that Kepler, using his equations of orbital motion, could predict the orbits of all the planets to a high degree of accuracy -- except Mercury. I've heard that mercury's motion ...
4
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1answer
306 views
How does an object falling into a plain Schwarschild black hole appear from near the black hole?
I know that when viewed from infinity (or from a very large distance from the black hole event horizon), an object that falls into the black hole will appear to slow down and will become more and more ...
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3answers
488 views
Questions about the Solar System
Most images you see of the solar system are 2D and all planets orbit in the same plane. In a 3D view, are really all planets orbiting in similar planes? Is there a reason for this? I'd expect that ...
5
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11answers
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Why do we say that the earth moves around the sun?
In history we are taught that the Catholic Church was wrong, because the Sun does not move around the Earth, instead the Earth moves around the Sun.
But then in physics we learn that movement is ...
3
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1answer
367 views
About binary stars and calculating velocity, period and radius of their orbit
I saw somewhere about being able to measure the velocity, period and radius of a binary star orbit by looking at red shift and blue shift.
I understand it but can someone give me an example of ...
13
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5answers
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Why do we always see the same side of the Moon?
I am puzzled why we always see the same side of the Moon even though it is rotating around its own axis apart from revolving around the earth. Shouldn't this only be possible if the Moon is not ...
6
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2answers
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What exactly is the microgravity field in orbit?
The ISS and other objects in orbit still experience small acceleration outside from the perfect line of orbit (of the system CM). For instance, two objects in the ISS that are let to be at rest will ...
6
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10answers
959 views
Is the distance between the sun and the earth increasing?
M = mass of the sun
m = mass of the earth
r = distance between the earth and the sun
The sun is converting mass into energy by nuclear fusion.
$F = \frac{GMm}{r^2} = \frac{mv^2}{r} \rightarrow r ...
2
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3answers
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Can a photon be made to orbit a known (or undiscovered theoretical) body?
Can a photon through some process be made to orbit a celestial or any other object?
Two follow-up questions.
Can this orbit be described as the photon crossing its own path.
Will this ...
2
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2answers
495 views
Why is the center-of-mass of 2 bodies at the focus of their elliptical orbits?
Why is the center-of-mass of 2 bodies (which interact only via Newtonian gravity) located at a focus of each of the elliptical orbits?
I know that when there are no external forces, the center of ...
5
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2answers
200 views
Why is there this asymmetry between the two foci of an orbital ellipse?
Why does the Earth revolve with the Sun at one of its foci? Does the other focus do nothing? Why is there this asymmetry in our solar system?
3
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2answers
262 views
When is the right ascension of the mean sun 0?
I understand that the right ascension of the mean sun changes (at least over a specified period) by a constant rate, but where is it zero? I had naively assumed that it would be zero at the most ...
3
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1answer
233 views
When and how were relative distances to the planets first measured?
I understand that the absolute distance to a planet can be measured using earth-baseline (e.g., diurnal) parallax, and that the first reasonably accurate such measurement was made for Mars by Cassini ...
3
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1answer
225 views
How do I calculate the time it would take for a space craft launching from earth to reach another planet?
I am making a matlab program the my final project for my programming class in college. I have chosen this problem, but I am bashing my head against the wall trying to figure out the equations and how ...
2
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2answers
294 views
Does the length of the sidereal day vary systematically?
I'm confused about some properties of the sidereal day, in particular whether its duration varies systematically over the course of the year.1 It seems to me that that must be the case, but the ...
6
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2answers
216 views
Are there planetary systems where the planes of orbits vary greatly?
Inspired by this question, are there any known planetary systems with largely varying planes of orbit? For example a system where two planets have perpendicular planes?
3
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2answers
218 views
Deviation from Earth's orbit
How much orbital deviation is required for the Earth to get knocked out from current orbit so it either moves away from Sun or towards the Sun?
3
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4answers
657 views
Can a balloon float into space? (+orbital velocity)
After watching the recent "space jump" a question arose. Why can a balloon not float into space? Can one be made/designed to do this?
Next, everything in orbit is falling back to earth. It only ...
2
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1answer
791 views
What are the temperatures of objects in Low Earth Orbit (LEO)?
What is the temperature of objects in Low Earth Orbit?
Consider LEO to be 600km to 800km.
0
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2answers
139 views
General Relativity & Kepler's law
According to Kepler's law of planetary motion, the earth revolves around the sun in an elliptical path with sun at one of its focus.
However,
according to general theory of relativity,
the earth ...
0
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1answer
174 views
What path would advanced spaceships take to move between planets? [closed]
Right now, space travel is all about carefully moving between orbits. If you want to go from Earth to Mars, you wait until the two planets are correctly aligned, and then place yourself into an ...
0
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1answer
151 views
Condition for circular orbit
I am a little confused about the condition for circular orbit. Goldstein's Classical Mechanics has the condition for circular orbit as $$f^'=0\tag1$$ where $f^'$ is the effective force. I understand ...
0
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3answers
378 views
Missing something basic about simple orbital mechanics
I seem to be missing something basic.
I've been trying to get a simple orbital simulation working, and my two objects are Earth around the Sun.
My problem is this. I placed the Earth at 93M miles ...
