[hist-analytic] Materialism and mass as a unit of measurement

Baynesr at comcast.net Baynesr at comcast.net
Tue Feb 1 07:39:26 EST 2011


I'll close my comments on massless photons by just summarizing and then going on to the philosophy, which is somehow (but unsurprisingly) getting lost. 

When a physicist sees 'm', he thinks rest mass. Photons have no rest mass; when physicists do speak of the mass of a photon at all, which is rare, they mean an *equivalence* in terms of energy. In the case of any other particle in the universe (I repeat "any other"!) attribution of mass does not depend on mere conversion (of *units*) between mass and energy. Moreover, if photons had mass the universe would fall apart. As one physicist remarks: 

"Atoms molecules and life are entirely dependent on the fact that electrons have no mass ." Leonard Susskind ( Stanford, originator of string theory) 

Now for some philosophy. I don't understand Roger's remarks here on what philosophers ought to be saying about mass. I need an answer to the following question: What is a physical entity? How is this determined noncircularly? So far I haven't received a reply on this, which is fundamental. 

I'll get to other posts soon. 

Regards 

Steve 

----- Original Message ----- 
From: "Roger Bishop Jones" <rbj at rbjones.com> 
To: hist-analytic at simplelists.co.uk 
Sent: Sunday, January 30, 2011 1:20:37 PM 
Subject: Re: Materialism and mass as a unit of measurement 

On Sunday 30 Jan 2011 01:01, Baynesr at comcast.net wrote: 

> No, I don't believe that a photon has mass. 

But modern physics does, and the experimental evidence 
supports this. 

> As I have 
> maintained, following others of course, it may have 
> "relativistic mass" (as you again remind us) and in this 
> sense of 'mass' the "mass" of an photon can be 
> calculated in relation to its energy. But this 
> calculation is little more than the same kind of 
> calculation obtained in converting from yards to meters; 
> it is not the sort of calculation of (rest) mass that 
> goes into determining the mass of a table or chair or 
> alpha particle or positron etc.. It is mass in a 
> Pickwikean sense. Again, a photon is a bundle of energy; 
> that energy may have an equivalence to mass, but only as 
> a yard may have its equivalence in meters. 

But in general relativity you don't have a separation 
between mass and energy, you just have mass/energy, and even 
that is relative to a frame of reference rather than 
absolute. 
There is nothing in the theory to allow you to tease these 
two apart (to the best of my knowledge). 

> Owing to this, when a scientist puts on his philosophical 
> cap and gown and pronounces all things material he 
> cannot mean all things that exist have mass. 

He certainly CAN mean that. 
It is a coherent position. 
You have to ask him (or read him) to discover whether he 
does in fact mean that. 

But surely a philosopher doing metaphysics will not usually 
want to put forward a metaphysic which is incompatible with 
currently accepted physics? 
In that case if he has says he is a materialist and accepts 
relativity, he must be counting as existing mass as it is 
conceived in that theory. 

Alternatively he might call himself merely a physicalist 
(not a materialist) and allow himself a mass/energy 
ontology. 
But the physicist will likely tell him he has not improved 
matters, for the distinction between mass and energy cannot 
be drawn in any absolute way (that's one aspect of why the 
theory is relativistic). 


> What does 
> he mean? Once he abandons mass as definitive of the 
> physical, then guys like J. Kim (the best living 
> philosopher on the mind/body problem), will have 
> trouble, e.g. bringing Ned Block's "drainage" argument 
> against supervenience to a halt. This is where the 
> physics becomes important to philosophy in this context; 
> the rest is science. Science is not philosophy. 

You mean, once he abandons your preferred conception of mass 
in favour of the one which appears in general relativity. 

As far as the mind/body problem is concerned, surely he does 
not need to get into details about what physically exists, 
he can leave that to the physicist. 
There might be things over and above mass and energy, even 
if the two can be separated. 
What about charge and spin? 
What about force fields (for forces other than gravitation)? 

I don't know the answer to these, but I don't see why a 
physicalist philosopher or a mind/body philosopher should 
care much about these details. 
Though I'm sure there are many interesting metaphysical 
issues. 

Anyway, my main point of interjection (since I don't know 
Kim's work) has been to respond to your critique based on 
the relativistic equations when interpreted in terms of rest 
mass. And I don't see how this can have any force given 
that they are not intended to be interpreted in that way. 

Roger Jones 






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