Path: csiph.com!news.swapon.de!fu-berlin.de!uni-berlin.de!not-for-mail From: Oscar Benjamin Newsgroups: comp.lang.python Subject: Re: [Still off-top] Physics [was Requests author discusses MentalHealthError exception] Date: Fri, 4 Mar 2016 17:35:00 +0000 Lines: 47 Message-ID: References: <56d16e6a$0$1593$c3e8da3$5496439d@news.astraweb.com> <56d5cbef$0$22142$c3e8da3$5496439d@news.astraweb.com> <56d7a130$0$1611$c3e8da3$5496439d@news.astraweb.com> <101Cy.1411363$QP2.758114@fx42.am4> <56d8d10e$0$1587$c3e8da3$5496439d@news.astraweb.com> <87lh5yjzob.fsf@elektro.pacujo.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: news.uni-berlin.de I08Z6fkJHz0X+f+imPmsJAEw/mXJwle+UNJx4QGYt9XQ== Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.023 X-Spam-Evidence: '*H*': 0.95; '*S*': 0.00; 'subject:: [': 0.03; 'cc:addr:python-list': 0.09; 'benjamin': 0.09; 'pointless': 0.09; 'undefined.': 0.09; 'whole.': 0.09; 'alpha': 0.15; 'subject: \n ': 0.15; '(resulting': 0.16; '2016': 0.16; 'cc:name:python list': 0.16; 'differs': 0.16; 'energies': 0.16; 'proportion': 0.16; 'received:io': 0.16; 'received:psf.io': 0.16; 'subject:exception': 0.16; 'wrote:': 0.16; 'subject:] ': 0.19; 'together.': 0.20; 'cc:2**0': 0.20; 'cc:addr:python.org': 0.20; 'context.': 0.22; 'precise': 0.22; 'defined': 0.23; 'header:In-Reply-To:1': 0.24; 'appear': 0.26; 'rest': 0.26; 'sense': 0.26; 'message- id:@mail.gmail.com': 0.27; '*the': 0.29; 'dimensions': 0.29; 'subject: [': 0.29; 'mass': 0.33; 'rate.': 0.33; 'similar': 0.33; 'previous': 0.34; 'gives': 0.35; 'received:google.com': 0.35; 'could': 0.35; 'replaced': 0.35; 'something': 0.35; 'received:209.85': 0.36; 'depends': 0.36; 'two': 0.37; 'say': 0.37; 'associated': 0.38; 'difference': 0.38; 'received:209': 0.38; 'why': 0.39; 'subject:-': 0.39; 'rather': 0.39; 'where': 0.40; 'still': 0.40; 'some': 0.40; 'term': 0.60; 'total': 0.62; 'different': 0.63; 'strictly': 0.64; 'march': 0.64; 'binding': 0.66; 'physics': 0.66; 'subject:off': 0.66; 'sum': 0.69; 'exceed': 0.72; 'state.': 0.72; 'subject:skip:M 10': 0.72; 'theoretical': 0.72; 'overall': 0.72; 'carried': 0.76; 'divide': 0.84; 'oscar': 0.84; 'subject:author': 0.84 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=6TCkwuoyZ4SpugYxuXhIm6gDNR0IP+hfIpYOye+anBE=; b=HOUf4g/nZ3cSNKMDOloOlckuiUEW65B2fUUbC1Mf5MsWQ+EwcJxyZb5rdSeJHaAvzj M5tP8+HOHKQH7FePHbwr0bX2Ahwl0RozcsjzZJI5mYX+/1ACUs3MmX9FdxShR4NdSitG DtfHmk9a0NakPhmtOBLhTyhdUKf4z/UI+tPUPI8VSqts7AWEMonktwkHDQbpUqxAmRfj zV6I5f+yProgkVl4yMd1f/G4wogO96YJawPPIqZPPCSRMwKGjuFDo133GSMh18A/7ZlT 0lxGIEA7GN4lGxIbatb7yPbj5BU1WVBqlKtFgtZgmLPB7JreXLDD5F7C3okvkWYf1mpB ps3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=6TCkwuoyZ4SpugYxuXhIm6gDNR0IP+hfIpYOye+anBE=; b=LXJH6JT0tjyJEA1zofovL8Fu5GG4dKq3d6EgtTq5uCNr4BNpX6mawK8k633MDIUAdr dm4bLJJB6iiiqybj4UmbfrXNFYTr6izQpCYqUeYBKTWmJno6eZJHJNuhSnrPOrlngAcU kKxfA7/S9Bz7aar8WslfvQh1TEH7esCi+2V0N8vT65h3fwmxaMhqWSYc4aO972MCHkna Vc9Pm0HXAlg7nMK58xRtfN1+uisc1zqklHe8nZr3bhim9oC8nHh6jy9nqaUfaJLQgXsM sRC38kw6+nxZ/3lkOEU0tv+m5dsr8901ioDW+A0mvOCEXxeybt9lRXeMQc7HcdwQXEH+ DptA== X-Gm-Message-State: AD7BkJKXJ/YlkNAdEx8Ctk5tOVDb1H2rNWXCOUsI/FfH5zxz94i7zs1D6ZadRarhgyrFIP2zeDHH8bcE18152g== X-Received: by 10.25.210.4 with SMTP id j4mr3701459lfg.130.1457112920429; Fri, 04 Mar 2016 09:35:20 -0800 (PST) In-Reply-To: <87lh5yjzob.fsf@elektro.pacujo.net> X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Xref: csiph.com comp.lang.python:104044 On 4 March 2016 at 10:38, Marko Rauhamaa wrote: > Oscar Benjamin : > >> The mass is carried by the new particles. The new particles may have a >> total *rest mass* which differs from the total rest mass of the >> previous particles. However the total mass is the rest mass plus the >> mass associated with the "kinetic energy" of the particles. >> >> [...] >> >> Mass and energy are not interchangeable in the sense that you can >> exchange one for the other with e=mc^2 giving the exchange rate. >> Rather mass and energy are *the same thing*. Although they are >> different concepts defined in different ways and having different >> dimensions and units they are inseparable: e=mc^2 gives us the >> proportion in which the two appear together. > > A physicist mentioned to me that the word "mass" has replaced the term > "rest mass" in modern Physics lingo. It depends on the context. Rest mass or similar can still be used where you want to stress the difference (as I was doing). > That's why you say a photon is > "massless" even though every observable photon has a relativistic mass. > It's all in the terminology. That's just a casual use of terminology. If we want to be precise then it's pointless to even refer to the "rest mass" of something that is never at rest. The masslessness of photons comes from an extrapolation that leads to a divide by infinity: strictly speaking it's just undefined. > As for the existence of a negative mass, it is interesting to note that > the (rest) mass of an alpha particle is less than the sum of the (rest) > masses of its constituents. About 1% of the mass is "missing." Since the binding is associated with negative energy it has a negative contribution to the energy/mass of the particle as a whole. This is true of any bound state. Something I don't know is if there's some theoretical reason why the binding energy could never exceed the sum of the energies of the constituent particles (resulting in an overall negative mass). -- Oscar