What is Orbit: Definition and 1000 Discussions

In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating trajectory, although it may also refer to a non-repeating trajectory. To a close approximation, planets and satellites follow elliptic orbits, with the center of mass being orbited at a focal point of the ellipse, as described by Kepler's laws of planetary motion.
For most situations, orbital motion is adequately approximated by Newtonian mechanics, which explains gravity as a force obeying an inverse-square law. However, Albert Einstein's general theory of relativity, which accounts for gravity as due to curvature of spacetime, with orbits following geodesics, provides a more accurate calculation and understanding of the exact mechanics of orbital motion.

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  1. J

    Equation for time dilation of body in orbit around Kerr black hole?

    Inspired by the movie Interstellar which featured a planet orbiting a rotating supermassive black hole with an extremely high time dilation factor (slowed by a factor of 60,000 relative to observers far from the black hole), I was wondering if anyone knows of an equation for time dilation of...
  2. V

    How much force I have to apply to throw a stone out of orbit?

    I know escape velocity. in order to get out of Earth's orbit the object has to maintain 11.2 km/s speed. But If I want to throw a 1kg stone out of orbit... how much force I have to apply?
  3. W

    How Can You Throw a Baseball into Orbit from the Top of Mt. Chimborazo?

    Homework Statement If you were on the top of Mt. Chimborazo in Ecuador (0°S, 80°W, elevation 20,564 ft), with what minimum speed (and in what direction) would you have to throw a baseball horizontally so that it would go into a circular orbit about the earth? (Neglect air friction. Assume a...
  4. N

    Can someone explain the mathematics of this formula for Venus' orbit

    I've always been interested by the pattern within venus' orbit around the sun. I found this image and the formula of its retrograde motion in the upper right hand corner which confused me. What does it mean? can someone break this down in layman's terms...
  5. B

    Gravitational Effects of Gyros Near a Massive Object

    Given an object spinning on its own axis, in orbit around a planet with mass and that the object is traveling in the direction of its axis, does the axis continue to point at the same point in infinity as it rotates around the planet or does the axis follow the curvature of space around the...
  6. S

    Satellite in Space: Why Freely Falling?

    Q1 Why does a satellite(or any space capsule etc) moving in a stable circular orbit around Earth behaves like a freely falling body?? Q2 Why do the astronauts in these capsules are said to be in weightless condition?? i m not much convinced with the solutions to my doubts so i would appreciate...
  7. R

    Precession of relativistic orbit in pure inverse-square force

    PROBLEM: Show that Special Relativity predicts a precession of π(GMm/cl)2 radians per orbit for any elliptic orbit under a pure inverse-square force. where G is gravitational constant, M is mass of larger body, m is mass of smaller orbiting body, c is speed of light and l is angular momentum...
  8. B

    How Is Delta V Loss Calculated for Spacecraft?

    How do you calculate how much delta v is lost from gravity and atmospheric drag? I've been looking for days but I can't find anything that actually tells me how it's calculated. For example it takes 1.5 km/s - 2 km/s extra delta v for a low Earth orbit because of drag loss, how was that number...
  9. T

    Results from TLE & SGP4 propagation - don't seem right & with interpretation

    Greetings all ! I have this problem with SGP4 propagation, that I hope someone can help me out with. I acquired a TLE of the ISS from internet and used the C++ SGP4 propagator to compute future position and velocity vectors of the Station. I am unsure about some aspects of results though and...
  10. N

    Did Arthur C Clarke invent Geostationary orbit of satellites ?

    I have been told that the discovery of the Geostationary orbit of satellites was attributed to Arthur C Clarke the well known writer of Science Fiction stories. Is it possible that he also made a serious study of this subject and were there any formulas involved which he might have published...
  11. gcombina

    Circular Orbit / Practice Quiz #4, Question 27

    Homework Statement What is the acceleration due to gravity at an altitude of 1.00 x 10^6 above the Earth's surface, given that the radius of the Earth is 6.38 x 10^6 m?Homework Equations Using g = GMm/r^2 Fc = mv^2/r The Attempt at a Solution Fc = mv^2/r How can I solve this equation if I am...
  12. C

    Period of a Proton's Orbit arount magnetic field

    Homework Statement A proton moves perpendicular to a magnetic field of .005 T. What is the period of the proton's circular orbit? Homework Equations 1. T=2pi/v 2. FB=qv x BThe Attempt at a Solution I know I need to solve for velocity first so I can use the period equation, but I don't...
  13. gcombina

    Satellite in Orbit (Quiz#4, 26)

    A satellite in orbit around the Earth has a period of one hour. An identical satellite is placed in an orbit having a radius that is nine times larger than that of the first satellite. What is the period of the second satellite? (a) 27 h (c) 4 h (e) 0.04 h (b) 3 h (d) 9 h** I...
  14. K

    Mass in a satellite changes orbit

    Homework Statement A i kg mass is in a satellite must move to a higher orbit. energy must be added. Can this energy be added at one time, by shooting the mass? Homework Equations Potential energy: ##E_p=\frac{GMm}{r}## Gravitational force: ##F=\frac{GMm}{r^2}## The Attempt at a Solution The...
  15. K

    Satellite in orbit losing speed

    Homework Statement A satellite is put into a stationary orbit around earth, i.e. it stays above one point, then it passes through a cloud and looses 10% of it's kinetic energy. it is stabilized again in a new orbit, what's the new radius. Homework Equations Attraction force...
  16. avito009

    Can You Orbit the Photon Sphere Without Being Pulled into the Event Horizon?

    Am I right when I say that you can orbit the photon sphere and still be not pulled towards the Event Horizon but you need to orbit (In your spaceship) at the speed of light?
  17. P

    A quick question about Elliptical/Circular Orbit

    Hi everyone. So I got this question in a test, but I'm not exactly sure about the answer. Q: For a planet moving in an elliptical orbit, why is 1/2Iω^2 not the correct expression for its kinetic energy? Thanks a lot in advance.
  18. A

    Orbit Precession Angle: Find & Condition for Cycles

    the problem says: "consider a particle with orbit ##r(\phi)=\frac{r_0}{1-\epsilon \cos (\beta \phi)}## ##\epsilon \in ]0,1[## and ##\beta=cte## a) Find the precession angle. b) What is the condition to the trayectory is totally cyclic?? __________________ I don't understand why i calculare...
  19. A

    Trying to calculate Orbit figures with C# and 3D space

    Hello smart people! I am trying to make a simulation of an orbit with C#. I have come so far that I more or less only need a way to convert the apoapsis, periapsis and ascending node to 3D space vector3's. If it is possible, I want to avoid longitude and latitude? Anyone have any suggestions...
  20. Basimalasi

    What causes an object to orbit around another?

    I watched a lot of videos and read a lot of articles regarding the orbit of the Earth around the sun and I just did not get it ..if they're both attracted to each other by a force then why don't the Earth just hit the sun like two magnets attracted to each other ..what causes that "Orthogonal"...
  21. M

    Orbital period of two moons in the same orbit

    1. Homework Statement Two identical moons of mass m maintain opposite positions in the same circular orbit of radius R around a planet of mass M. Find T2 the square of the orbital period. 2. Homework Equations T2=(4*pi2*R3)/ ( G*M ) [b]3. The Attempt at a Solution Hi...
  22. T

    Orbit Determination Issue (Method of Gauss, in Escobal's text)

    So I'm coding up some initial orbit determination stuff in MATLAB (for personal education; I love this stuff), and I am using 'Methods of Orbit Determination' by Escobal as a guide. I already got Vallado's code to work, now I'm just comparing other methods. I'm having an issue with one of his...
  23. S

    Uniform Circular Motion vs Circular Orbit due to Gravity

    In uniform circular motion, (eg, a mass on the end of a string moving in a horizontal circle) centripetal force is the only thing causing acceleration. we have the kinematic relationship V=RW or velocity is proportional to radius. I.e a bigger radius means greater linear speed? For the...
  24. B

    Creating an equation of a 2D path of an orbit

    Hi all This question came up to me when I was playing a game called KSP (a space sim game): Given an initial velocity and starting altitude, how do you create a 2D Cartesian equation of the orbit of that projectile around earth? For example if I told you a projectile is traveling at a...
  25. R

    Calculate Interstellar Rock Orbit in Solar System

    Is it possible to calculate the entire orbit of an interstellar piece of rock that has entered our solar system from observing the parameters and trajectory of that rock exhibits while inside our solar system?
  26. S

    Calculating Orbital Radius from Albedo and Temperature?

    Homework Statement Assume that a planet can have an atmosphere if the escape speed of the planet is 6 times larger than the thermal speed of the molecules in the atmosphere (also known as the root-mean-square molecular velocity). Suppose a hypothetical object having the same mass and radius...
  27. S

    Need help solving a differential equation for orbit.

    I want to be able to map the position of a planet given initial position, velocity, and acceleration. I know the equation for Gravitational force (Newtonian) is: F=-GMm/r^2 Using Newtons second law this gives: m(d^2x/dt^2)=-GMm/x^2 Then simple Algebra yields: (d^2x/dt^2)+GM/x^2=0 I...
  28. collinsmark

    Kerbal Space Program - Efficient Launch into Orbit

    Efficient launch into orbit. Designing a small, simple, efficient and stable launch vehicle to get into Kerbin's orbit can be done pretty easily. But in order to avoid building oversized, overcomplicated, drag prone behemoths (like the one I was using in the first post of this thread), one...
  29. X

    I'm trying to simulate moon orbit around earth, my moon is broken.

    Homework Statement Alright, this is probably going to be a long one. For a school project I am trying to simulate (in 2D) our moon's orbit around the earth, to eventually simulate a spaceship doing a hohmann transfer between LEO and LLO whilst being affected by both the Earth's gravity and...
  30. F

    Calculate the orbital velocity in a geostationary orbit

    Homework Statement Calculate the orbital velocity in a geostationary orbit (the circular orbit around the Earth which has a period of 24 hours) and show that its radius is approximately 40,000 km. A satellite is to be inserted into a geostationary orbit from an elliptical orbit with perigee at...
  31. W

    Measuring Earth's Orbit: Methods and Distortions Explained

    How do scientists measure the distance between the Earth and sun as it orbits? Do they use visual distance or do they account for distortions?
  32. T

    Q&A: EM Orbits & Tides: Attraction & Repulsion?

    1. Can a magnet orbit another magnet (of opposite charge) despite the fact that their masses are insufficient to generate the orbit; i.e., their orbits are caused only by the EM force? 2. Would/could the EM attraction between them generate tidal effects on the two magnets? 3. If you had two...
  33. C

    Explaining How Astronauts in Low Earth Orbit Stay Cool

    Hello, Can someone please explain to me how Astronauts in Low Earth Orbit do not instantly fry up when in direct sunlight? How does the International Space station, for example, not become a torch-lit super-oven when the sun's rays hit its walls? Thank you for helping me understand, and...
  34. shott92

    Einstein on the orbit of mercury, how does this fix Newton's theory?

    hi guys, i have a very limited knowledge of physics, and have an engineering background. but i saw on a program i was watching yesterday about the solar system, one of the comments made on there was about how Newton's equation for gravity was what was used to find "neptune??" however it...
  35. C

    Stability Condition for Circular Orbit

    Homework Statement Show that the stability condition for a circular orbit of radius a, i.e. f(a) + \frac{a}{3} (\frac{df}{dr})_{r=a} < 0 is equivalent to the condition \frac{d^2V(r)}{dr^2} > 0 for r=a where V(r) is the effective potential given by V(r) = U(r) +...
  36. M

    Period of falling through asteroid vs orbit

    Homework Statement Homework Equations See below The Attempt at a Solution My book derives the period of oscillation through the tunnel: T = 2pi/w = 2pi*sqrt(m/k) = 2pi*sqrt(3/(4pi*G*p)) = sqrt(3pi/(G*p)) Where p is the density of the asteroid, and G is the Newton's gravitational...
  37. C

    Time Comet Remains Within Earths Orbit

    Homework Statement A comet is going in a parabolic orbit lying in the plane of the earth’s orbit. Assuming that the earth’s orbit is a circle of radius a. The points where the comets orbits intersects the earth’s orbit are given by: cos θ = −1 + 2p/a where p is the perihelion distance...
  38. T

    Calculating Earth's Orbital Velocity from Varying Distance to the Sun

    Homework Statement Given that the Earth's distance from the sun varies from 1.47 to 1.52x10^11m, determine the minimum and maximum velocities of the Earth in it's orbit around the sun. Homework Equations F=G\frac{m1m2}{r^2} E=K+U ? The Attempt at a Solution I think the...
  39. M

    Orbit change due to hypothetical mass change

    Hi everyone, I want to discuss the following question: What would happen to the distance between two objects with masses M and m with M >> m if the central mass M was time-dependent (e.g. the moon's orbit if the mass of the Earth would increase slowly)? My theory goes like this: The...
  40. A

    Exploring Earth's Orbit with a Changing Sun

    Homework Statement If the mass of the sun were 1/2 it's current mass suddenly show the orbit of the Earth would be a parabola... The Attempt at a Solution I'm not sure what kind of approach to apply here, if the total energy equals zero then the orbit is a parabolic trajectory, if it is less...
  41. G

    Speed of satellite in geosynchronous orbit

    Homework Statement Derive an equation and solve for the speed of a satellite in geosynchronous orbit. You may NOT use the value of the satellite's altitude or radius in your calculations. If you do, you will receive no credit. You should use your knowledge of forces and uniform circular...
  42. E

    Analogy between satelite orbit and mass oscillating through earth

    The period of a satellite revolving around the Earth earth at surface height is equal to the period of any mass thrown through a hole of the earth(which gains a simple harmonic motion)... It seemed really interesting to me... Why both of these periods are same? T=2 π √(R/g)
  43. U

    3D Harmonic Oscillator Circular Orbit

    Homework Statement I found this in Binney's text, pg 154 where he described the radial probability density ##P_{(r)} \propto r^2 u_L## Homework Equations The Attempt at a Solution Isn't the radial probability density simply the square of the normalized wavefunction...
  44. A

    Calculating Satellite Orbit Time

    Homework Statement The average speed of an orbiting satellite is 20,000 mph. How much time is required for the satellite to orbit Earth? (the satellite is orbiting 250 miles above the Earth’s surface, and remember that the Earth has a radius of 3,963 miles.) Homework Equations t=d/v...
  45. M

    Is a Helicopter on a Geostationary Orbit?

    Is a helicopter which is stationary relative to the surface on a geostationary orbit? Why, or why not?
  46. xpell

    Orb.mec: Is the inclination of an ecliptic-perpendicular orbit 113,4º?

    I'm trying to understand this one. Let's imagine we want to launch a satellite to the perpendicular-to-the-plane-of-the-ecliptic orbit ("passing through the North and South ecliptic poles", or perpendicular to the Sun-Earth line, through the Earth). Since the Earth's axial tilt is around 23.4º...
  47. Shadow236

    Magnitude of acceleration given the orbit

    Homework Statement A satellites are placed in a circular orbit that is 3.22 × 105 m above the surface of the earth. What is the magnitude of the acceleration due to gravity at this distance?Homework Equations a = MG/R^2The Attempt at a Solution For the above formula I have trouble because I do...
  48. S

    Relativistic effects of a low orbit around supermassive objects

    Hi everyone, first post here. Lurking for a while but it was time to register.. I'm trying to conceptualize an idea in which humans are sent to orbit a very massive object, like a neutron star, a magnetar or even possibly a black hole. I would like the ship to be relatively close to the surface...
  49. C

    Understanding Gravity & Orbit in Our Solar System

    Keeping in mind I am a person that did not go to school...This must be a common question. Can be maddening for you guys to keep reading it over and over. Would be happy to read any links you want to post. I did a search on Gravity and Orbit, and did not see this topic. But those words garner a...
  50. S

    Hydrogen atom: potential well and orbit radii

    Hello, I happened to open up an old book by Sah, and in it he says: "it is evident that the electron orbit radius is half the well radius at the energy level E_n" The orbit radius is r_n=\frac{4*\pi*ε_0*\hbar^2*n^2}{mq^2} and the potential well...
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