The Spacetime Of Galilean Relativity Viewed Through Systemic Functional Linguistics

Penrose (2004: 386-7):

What Galileo teaches us is that the dynamical laws are precisely the same when referred to any uniformly moving frame. … There is nothing to distinguish the physics of the state of rest from that of uniform motion. In terms of what has been said above, what this tells us is that there is no dynamical meaning to saying that a particular point in space is, or is not, the same point as some chosen point in space at a later time. In other words, our cinema-screen analogy is inappropriate! There is no background space — a ‘screen’ — which remains fixed as time evolves. 

We cannot meaningfully say that a particular point p in space (say, the point of the exclamation mark on the keyboard of my laptop) is, or is not, the same point in space as it was a minute ago. To address this issue more forcefully, consider the rotation of the Earth. According to this motion, a point fixed to the Earth’s surface (at the latitude of Oxford, say) will have moved by some 10 miles in the minute under consideration. Accordingly, the point p that I had just selected will now be situated somewhere in the vicinity of the neighbouring town of Witney, or beyond. But wait! I have not taken the Earth’s motion about the sun into consideration. If I do that, then I find that p will now be about one hundred times farther off, but in the opposite direction (because it is a little after mid-day, and the Earth’s surface, here, now moves oppositely to its motion about the Sun), and the Earth will have moved away from p to such an extent that p is now beyond the reach of the Earth’s atmosphere! But should I not have taken into account the sun’s motion about the centre of our Milky Way galaxy? Or what about the ‘proper motion’ of the galaxy itself within the local group? Or the motion of the local group about the centre of the Virgo cluster of which it is a tiny part, or of the Virgo cluster in relation to the vast Coma supercluster, or perhaps the Coma cluster towards ‘the Great Attractor’? 

Clearly we should take Galileo seriously. There is no meaning to be attached to the notion that any particular point in space a minute from now is to be judged as the same point in space as the one that I have chosen.

Blogger Comments:

From the perspective of Systemic Functional Linguistic Theory, the general confusion here is of 'location' with 'thing'. First, a second-order location (space realised in a projected image) is confused with a first-order thing onto which the image is projected (a cinema screen). Then, a location ('point in space') is confused with a thing ('the point of an exclamation mark'), which naturally leads to the confused notion that a location changes its location ('is not the same point in space') as processes unfold.

If 'location' and 'thing' are not confused, then it is things that change their locations — relative to other things — as processes unfold.