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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: sci.physics.relativity
Subject: Re: the notion of counter-intuitiveness in relativistic physics
Date: Sun, 13 Oct 2024 11:48:32 +0300
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On 2024-10-13 06:19:44 +0000, Thomas Heger said:

> Am Mittwoch000007, 07.08.2024 um 23:28 schrieb Richard Hachel:
>> Le 07/08/2024 à 22:22, nospam@de-ster.demon.nl (J. J. Lodder) a écrit :
>>> Richard Hachel <r.hachel@jesauspu.fr> wrote:
>>> 
>>>> Le 07/08/2024 à 16:25, hitlong@yahoo.com (gharnagel) a écrit :
>>>>> On Wed, 7 Aug 2024 13:18:33 +0000, Richard Hachel wrote:
>>>>>> 
>>>>>> Le 07/08/2024 à 12:09, film.art@gmail.com (JanPB) a écrit :
>>>>>>> 
>>>>>>> Your biggest problem at this time is that you cannot understand the
>>>>>>> explanations given to you.
>>>>>> 
>>>>>> <http://news2.nemoweb.net/jntp?74ipUL6JcQu72w-mbGQ7BbVp7kU@jntp/
>>>> Data.Media:
>>> 1>
>>>>>> 
>>>>>> I laughed.
>>>>>> 
>>>>>> R.H.
>>>>>> Hmm, doesn't look like a laugh.  Maybe an OMG!  Meaning, you just
>>>>> realized that Jan is right.  Well, maybe a laugh would be appropriate,
>>>>> too, meaning "how could I have been so wrong!"
>>>>>> You come up with your D'=D.sqrt[(1+Vo/c)/(1-Vo/c)], which isn't
>>>> length
>>>>> contraction but Doppler shift, which is dependent on the sign of your
>>>>> Vo.  LC is NOT so dependent.  It would be a VERY strange universe if
>>>>> it were.
>>>> 
>>>> You say: "it's a Doppler shift".
>>>> And for sqrt(1-Vo?/c?)?
>>>> Isn't it a Doppler shift?
>>>> Yes, it's also a Doppler shift.
>>>> This is what Hachel calls the "internal Doppler effect".
>>>> Relativists call it the transverse Doppler effect, but the term is neither
>>>> fair nor pretty.
>>> 
>>> It was reasonable and fair nomenclature at the time.
>>> People didn't have relativity in order,
>>> and they discussed the motion of electrons in terms of variable masses.
>>> They discovered that the 'longitudinal mass' and the 'transverse mass'
>>> of the electron were different.
>>> It seemed quite reasonable at the time to extend the notion to light,
>>> because the terminology was already current,
>>> 
>>> Jan
>> 
>> The big problem with relativity is the almost complete absence of clear 
>> concepts.
>> There is no need to talk about transverse mass, longitudinal mass, and 
>> other such joys.
> 
> Mass is a scalar quantity and denotes the resistance to acceleration.
> 
> It is NOT 'quantity of matter' or similar!

There are many ways to quantify matter. Mass is one possibility,
especially when comparing pieces of the same kind of matter. If
you carry a gram of gold to another place its mass is still two
grams unless some matter has been added or removed as should be
expected about the quantity of the matter.

For some purposes other ways to quantify matter are better. Mass
is easier to determine than baryon number but the latter can be
regarded as more fundamental. Volume is easy, too, and often used
but is more sensitive to temperature.

For overload avoidance (of buildings, bridges, airplanes, ...)
mass is useful because the loads depend mainly on the mass.

-- 
Mikko