Comments on: What are the Lagrange points? http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/ I am an astronomer, writer, and skeptic. I likes reality the way it is, and I aims to keep it that way. My real name is Phil Plait, and I run the Bad Astronomy blog. Fri, 21 Nov 2008 18:16:57 +0000 http://wordpress.org/?v=2.3.1 By: On the topic of other skeptic/science blogs. « Northwest Skeptics http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-123928 On the topic of other skeptic/science blogs. « Northwest Skeptics Wed, 08 Oct 2008 07:25:03 +0000 http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-123928 [...] astronomer and does great work in describing the forces at play in space. His video posts with squishy brain suns and candy planets have been some of the most informative and yet entertaining things I’ve seen. A truly [...] […] astronomer and does great work in describing the forces at play in space. His video posts with squishy brain suns and candy planets have been some of the most informative and yet entertaining things I’ve seen. A truly […]

]]> By: Rhett Allain http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-109328 Rhett Allain Mon, 04 Aug 2008 18:48:17 +0000 http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-109328 It's me again. I thought about this some more and it seems that this centrifugal force thing is common enough that I put a post on my blog about it - http://dotphys.net/files/bad_physics.html I think the best point against centrifugal force being real is the example of a person sitting in a car that is accelerating forward. What is the force that pushes that person back into his/her seat? Yes, there is no such force. It is exactly the same for circular motion and the centrifugal force. Alas, this blog post is too old. No one will even see these comments anyway. So why am I still talking? I don't know. It’s me again. I thought about this some more and it seems that this centrifugal force thing is common enough that I put a post on my blog about it - http://dotphys.net/files/bad_physics.html

I think the best point against centrifugal force being real is the example of a person sitting in a car that is accelerating forward. What is the force that pushes that person back into his/her seat? Yes, there is no such force. It is exactly the same for circular motion and the centrifugal force.

Alas, this blog post is too old. No one will even see these comments anyway. So why am I still talking? I don’t know.

]]> By: Rhett Allain http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-108349 Rhett Allain Sat, 02 Aug 2008 14:42:26 +0000 http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-108349 AHHH!!!!! My EARS!!!!! I can't believe you said centrifugal force was real. When I think of forces, I think of fundamental forces (gravity, electromagnetic, strong nuclear, weak nuclear). These are forces. Which of these fundamental forces (if it is indeed real) is centrifugal force? You may counter - but what about friction??? Is friction a fundamental force? I say yes. Friction is a macroscopic phenomena caused by the electromagnetic interaction between atoms in the two materials. It is fine to TREAT the centrifugal force as real in your calculations, that works depending on your frame of reference, but as one commenter pointed out: not all frames are equal (non-inertial frames are different than inertial). A much better way to deal with "this centrifugal stuff" is to go back to Newton's 2nd law, when written like this: F_net = dp/dt (left off the vector signs) then the "centrifugal" part would fall on the right side as a change in momentum due to circular motion. Just because you can algebraically move it to the left side of the equation does not make it a real force. I feel better now. (maybe I will talk about this more on my blog) AHHH!!!!! My EARS!!!!! I can’t believe you said centrifugal force was real. When I think of forces, I think of fundamental forces (gravity, electromagnetic, strong nuclear, weak nuclear). These are forces. Which of these fundamental forces (if it is indeed real) is centrifugal force? You may counter - but what about friction??? Is friction a fundamental force? I say yes. Friction is a macroscopic phenomena caused by the electromagnetic interaction between atoms in the two materials.

It is fine to TREAT the centrifugal force as real in your calculations, that works depending on your frame of reference, but as one commenter pointed out: not all frames are equal (non-inertial frames are different than inertial).

A much better way to deal with “this centrifugal stuff” is to go back to Newton’s 2nd law, when written like this: F_net = dp/dt (left off the vector signs) then the “centrifugal” part would fall on the right side as a change in momentum due to circular motion. Just because you can algebraically move it to the left side of the equation does not make it a real force.

I feel better now. (maybe I will talk about this more on my blog)

]]> By: Tom Marking http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-106545 Tom Marking Tue, 29 Jul 2008 03:29:45 +0000 http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-106545 "@Kurt, As no reference frame is special, both centripedal and centrifugal forces are real, they merely depend upon which frame one chooses." The equivalence of all reference frames (special theory of relativity) only applies to non-accelerating reference frames. “@Kurt,
As no reference frame is special, both centripedal and centrifugal forces are real, they merely depend upon which frame one chooses.”

The equivalence of all reference frames (special theory of relativity) only applies to non-accelerating reference frames.

]]> By: Kevin F. http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-106087 Kevin F. Sun, 27 Jul 2008 17:52:09 +0000 http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-106087 And it looks like I messed up my linking, too! <a href="http://www.jwst.nasa.gov" rel="nofollow">http://www.jwst.nasa.gov</a> And it looks like I messed up my linking, too! http://www.jwst.nasa.gov

]]> By: Kevin F. http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-106086 Kevin F. Sun, 27 Jul 2008 17:50:43 +0000 http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-106086 You got the link wrong for the James Webb Space Telescope. the correct link is <a href-"http://www.jwst.nasa.gov/" rel="nofollow">http://www.jwst.nasa.gov/</a> - you didn't have the www at the beginning. You got the link wrong for the James Webb Space Telescope. the correct link is http://www.jwst.nasa.gov/ - you didn’t have the www at the beginning.

]]> By: DaveS http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-106076 DaveS Sun, 27 Jul 2008 16:54:31 +0000 http://blogs.discovermagazine.com/badastronomy/2008/07/25/what-are-the-lagrange-points/#comment-106076 You're right, of course, Shoe. I was thinking of classical dynamics. You’re right, of course, Shoe. I was thinking of classical dynamics.

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