Comments on: Does the Earth move around the Sun?

By: Humankind’s Basic Picture of the Universe | Cosmic Variance

Humankind’s Basic Picture of the Universe | Cosmic Variance — Mon, 06 Nov 2006 04:45:52 +0000

[...] There are important issues of empiricism vs. idealism here. The kinds of questions addressed by “theoretical computer science” are in fact logical questions, addressable on the basis of pure mathematics. They are true of any conceivable world, not just the actual world in which we happen to live. What physics teaches us about, on the other hand, are empirical features of the contingent world in which we find ourselves — features that didn’t have to be true a priori. Spacetime didn’t have to be curved, after all; for that matter, the Earth didn’t have to go around the Sun (to the extent that it does). Those are just things that appear to be true of our universe, at least locally. [...]

By: nikita

nikita — Mon, 03 Apr 2006 14:16:46 +0000

see every body knows that the earth takes revolution around the sun and thats true why we should beconfused in such a question.

By: rosey

rosey — Tue, 15 Nov 2005 19:24:08 +0000

cows are mad

By: Amanda

Amanda — Tue, 15 Nov 2005 19:22:37 +0000

How many miles is the atmosphere from the earth’s surface?

By: Mark Wyatt

Mark Wyatt — Sun, 09 Oct 2005 01:22:21 +0000

I have put together a three part series on geocentrism. The first two parts are dealing with science, and the third deals with the Church position. Take a look.

Go to http://www.veritas-catholic.blogspot.com

Geocentricity 101: A beginner’s Course
Geocentricity 101, Part I: Basic Principles
Geocentricity 101, Part II: Basic Physics
Geocentricity 101, Part III: Scriptural and Church Position

Mark Wyatt

By: bittergradstudent

bittergradstudent — Wed, 05 Oct 2005 06:44:48 +0000

Belizean:

Mach’s principle makes explicit reference to “distant stars.”–i.e., objects infinitely far away. It then picks out a preferred reference frame by demanding stationarity with respect to these.

A priori, there is no reason to postulate the existence of such objects (in fact, until recently, it was reasonable to believe that the universe might have a finite volume, and therefore, a finite “maximal” diameter).

The equivalence principle is essentially a statemetn that there is no such thing as absolute acceleration–acceleration and four dimensional curvature are interchangeable concepts (speaking very loosely, find a coordinate system where F/m is the same as the Christoffel symbols). Hence, in GR, there are only equivalence classes of inertial reference frames (i.e., sets of frames which do not accelerate with respect to each other), rather than an absolute notion of inertial/non-inertial. That is, unless you invoke something like Mach’s principle, or a Geocentric principle, or a Heliocentric principle.

By: Belizean

Belizean — Tue, 04 Oct 2005 15:06:33 +0000

This is related to the old issue of Mach’s Principle in GR.

Even though things LOOK the same, you CAN tell the difference between 1) the stars spinning about you, and 2) your body spinning at the same angular rate.

So Mach’s Principle is not part of GR (even though it motivated Einstein).

And inertial reference frames have a preferred place in the theory in the sense that they are all connected by the modern version of the Equivalence Principle in a way that accelerated frames are not.

Hence, the Earth revolves around the Sun, because the former’s acceleration well exceeds the latter’s.

By: Jack

Jack — Tue, 04 Oct 2005 06:23:28 +0000

Oh yes, I meant to ask Sean: What is a “dark energy task force?” Sounds scary.

By: agm

agm — Tue, 04 Oct 2005 04:08:17 +0000

In the right reference frame, both the earth and the sun revolve around the server hosting this blog.

By: Phil Plait

Phil Plait — Tue, 04 Oct 2005 03:13:17 +0000

As it happens, I get real live geocentrists trying to use GR to claim that geocentrism is just as valid as heliocentrism. I find that amusing, because what they are really trying to show is that geocentrism is really the One True Way. It got so bad on my old bulletin board I wrote a FAQ for it:

Geocentrism, as advocated by creationists or other religiously fundamental people, is certainly wrong.

How, you may ask? What is going on is that you can do a change of reference frame to a geocentric one, and by relativity the math must still work out. I readily admit that. I do not understand all the math involved, but I will take it for granted that it works out, and that physically, geocentrism is just as valid as, say, heliocentrism.

But note the words “just as valid”. Also, by relativity, it cannot be any more valid; geocentrism is just another change of frame (although to a non-inertial one).

What geocentrists are saying is that geocentrism is the one, true frame. Creationists must say that because that is what is says in the bible. Now pay attention here, because this is the important bit: to say geocentrism isn’t wrong, you have to accept the premise that any frame of reference is just as valid as any other. But to claim that geocentrism is correct, you have to ignore that very same premise.

Geocentrism as the One True Way is therefore self-contradictory. It doesn’t work.