10/31/2022 0 Comments Circular orbit![]() The name “conic section” comes from the fact that all the above curves can be formed as intersections of a cone with a plane.Īnyway, these types of orbits (which trace out curves that are conic sections) are called Kepler orbits. Note that in the context of this article, we’ll be mostly discussing orbits in which one object orbits a central mass that is stationary (unless stated otherwise).Ĭonic sections are basically a geometric class of curves that include circles, ellipses, parabolas and hyperbolas. In Newtonian gravity, which is more or less the usual theory of gravity as a force between massive objects, all orbits under the influence of gravity are conic sections. We’ll look at exactly this next in the context of orbits. In these cases, the predictions given by general relativity are quite different than those given by Newtonian gravity. Now, the important thing is that general relativity is only necessary to describe gravitational fields that are extremely strong (such as in the case of orbits around black holes). In general relativity, on the other hand, gravitational forces are viewed as changes in the geometry of spacetime (curvature) due to energy being present (including mass) and all objects simply follow their natural paths in this curved geometry (geodesics). In the Newtonian picture, gravity is an attractive force between any objects with mass, to put it simply. You may also wish to check out my guide on learning general relativity on your own, which aims to give you a step-by-step approach on how you can learn general relativity by yourself without any kind of formal education.Īnyway, the main point that you need to understand about general relativity for this article is that general relativity describes gravity from a different perspective than Newtonian gravity with different (and more accurate) predictions. However, what does work objectively and give correct predictions is the mathematics of general relativity.įor this article, you won’t really need much math, but if you’re interested, I have an introductory article on general relativity that covers all the underlying principles of the theory as well as how these are described by the sometimes complicated mathematics of general relativity. This is why the whole geometric picture of general relativity is quite abstract in many cases and should not be taken too literally (like we sometimes see with awkward rubber sheet and billiard ball analogies of curved spacetime). The problem with it comes from the fact that it is not something we can just intuitively imagine. The idea of spacetime curvature is sometimes a little misunderstood. Any object moving along a geodesic will follow the curvature of spacetime, resulting in an apparent gravitational force that then allows the object to undergo orbital motion. General relativity explains orbits as paths through spacetime along which there are no external forces. So, how exactly does general relativity explain orbits? Orbits around black holes generally require the use of general relativity (as opposed to Newtonian gravity) due to the extremely strong gravitational fields of black holes. The first thing we’ll cover is how exactly general relativity explains orbits of objects under the influence of gravity. We’ll also look at how different types of black holes affect these orbits (such as how orbits look like around charged and rotating black holes). In this article we’ll be discussing all kinds of details about orbits around black holes, such as what kinds of orbits are possible (they can be very different from what we typically see when observing planetary orbits). At distances less than the IBCO, any orbiting body will inevitably spiral into the black hole due to gravity being too strong. However, these orbits can be extremely complicated and they can only occur at distances greater than the innermost bound circular orbit (IBCO). ![]() Now, can you actually orbit a black hole in the first place? One of the ways black holes differ from planets, for example, is that orbits around them can be much more intricate and complicated. To me, black holes have always been some of the most interesting phenomena in modern physics. ![]()
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