Saturday, November 24, 2007

Dark Matter (aka Aether?)

Have a look at this video from Scientific American (double click the arrow):

video

In the video, the guy stirs coffee with floating crumbs and notes the crumbs nearer the middle rotate at a different angular rate than crumbs further out. He then spins a compact disk (CD) and notes all the marks on it rotate at the same angular rate because they are embedded in the disk itself.

He says the stars in our galaxy rotate more like the marks on the CD, which leads scientists to postulate the existence of "dark matter", an invisible, undetectable substance that fills what appears to be empty space between the stars. Dark matter/energy constitutes the vast majority of the Universe.

According to http://en.wikipedia.org/wiki/Aether_(classical_element), "Albert Einstein, in an interpretation he offered for his theory of special relativity, dismissed [aether] ... though he later reinstated a logical need for an aether in a commentary on his theory of general relativity, modern astrophysical theories refer to this as Dark Energy/Matter."

I, like classical scientists, cannot fathom an "action at a distance" force field, such as gravity, without some physical matter filling the void between the masses that are attracted to each other by that force. Were classical scientists basically correct about aether and is the modern notion of dark matter/energy simply a refinement of that concept?

Ira Glickstein

1 comment:

joel said...

Ira said:

I, like classical scientists, cannot fathom an "action at a distance" force field, such as gravity, without some physical matter filling the void between the masses that are attracted to each other by that force. Were classical scientists basically correct about aether and is the modern notion of dark matter/energy simply a refinement of that concept?

Joel responds:

I believe that this is a good illustration of what may be called "perceptual prejudices." Except for quantum theory, our mental models of how things work always need to feel comfortable, i.e. be consistent with our senses. That's why we picture atoms, molecules and the like as hard shell spheres. It's an extension of the human tendency to anthropomorphize. We personally are incapable of causing action at a distance, so we don't like the notion. We are perfectly comfortable with models that involve pushing and pulling when we are in contact, because that's what we perceive that we do. However, we do neither. If I pull a ball toward me, I'm really getting my hand around the other side of it and pushing with my fingers. Add to this the fact that my fingers never actually come in "contact" with the ball. There is always an intervening field, be it electrostatic, gravitational or Van der Waal that separates us from another object. We just don't see it.

Classical scientists devised such invisible substances as caloric and aether to satisfy their anthropomorphic or perceptual prejudices. Neither one is really necessary. There's an interesting difference between these two however. In the case of caloric, a better model came along (molecular vibration) when caloric couldn't be warped any further to fit new data. In the case of aether, it was simply dropped when interferometer data contradicted the model. For me, the dark matter explanation of excess temperature and mass of the universe, is just another example of the invention of invisible substances to satisfy a human perceptual need. Although our anthropocentric models of the universe help us to computationally to account for everything, philosophically speaking they may obscure the deeper nature of the world we live in. We should remember that the caloric model of heat reached its maximum complexity and popularity just before it collapsed under the weight of Count Rumford's cannon boring experiments.