Re: New challenge to Einstein from experiment?

From: George Dishman (george_at_briar.demon.co.uk)
Date: 02/11/05 

Date: Fri, 11 Feb 2005 16:55:38 -0000

"Androcles" <Androcles@ MyPlace.org> wrote in message
news:SPvMd.1309$g4.1300@fe1.news.blueyonder.co.uk...
>
> "George Dishman" <george@briar.demon.co.uk> wrote in message
> news:cttud6$khh$1@news.freedom2surf.net...
>>
>> "Androcles" <Androcles@ MyPlace.org> wrote in message
>> news:SHbMd.50283$v8.34501@fe2.news.blueyonder.co.uk...
>>>
>>> "George Dishman" <george@briar.demon.co.uk> wrote in message
>>> news:ctrgo3$vnd$1@news.freedom2surf.net...
>>>>
>>>> "Androcles" <Androcles@ MyPlace.org> wrote in message
>>>> news:oUaMd.918$89.846@fe3.news.blueyonder.co.uk...
>>>>>
>>>>> "George Dishman" <george@briar.demon.co.uk> wrote in message
>>>>> news:ctrchh$uej$1@news.freedom2surf.net...
>>>>>>
>>>>>> "Androcles" <Androcles@ MyPlace.org> wrote in message
>>>>>> news:Lb5Md.45935$v8.24360@fe2.news.blueyonder.co.uk...
>>>>>>>
>>>>>>> <george@briar.demon.co.uk> wrote in message
>>>>>>> news:1107352195.486708.134410@o13g2000cwo.googlegroups.com...
>>>>>>>>
>>>>>>>> Androcles wrote:
>>>>>>>>>
>>>>>>>>> ... How anyone could claim V = (u+v)/ ( 1 + uv/c^2) is
>>>>>>>>> baffling to say the least, ...
>>>>>>>>
>>>>>>>> Don't worry, there's no need to be baffled. ...
>>>>>>
>>>>>> <snip simple analogy>
>>>>>>
>>>>>>> Oh really?
>>>>>>
>>>>>> OK, if you are still baffled, maybe you do have cause to
>>>>>> worry, but keep trying.
>>>>
>>>> Have you managed to grasp it yet?
>>
>>
>> Are you still trying to understand or has the
>> penny dropped?
>
> What, that you snip without answering?

OK, here's what I snipped, the question
was "Have you managed to grasp it yet?":

<unsnip>
<george@briar.demon.co.uk> wrote in message
news:1107352195.486708.134410@o13g2000cwo.googlegroups.com...
>
> Androcles wrote:
>>
>> ... How anyone could claim V = (u+v)/ ( 1 + uv/c^2) is
>> baffling to say the least, ...
>
> Don't worry, there's no need to be baffled. This
> simple analogy should help you understand.
>
> A door wedge is 8cm long and rises 2cm, that's a
> slope of 1 in 4. If the gap under the door is 3cm,
> I could stack two such wedges with the thin ends
> together to stop it swinging. What is the slope of
> the combined pair of wedges?
>
> If you said "2 in 4" you would be wrong. To find the
> total, you need to realise that it is the angles at
> the thin end that must be added. The angle in this
> case is arctan(1/4) or about 14 degrees, so the two
> wedges total 28 degrees. The tangent of that angle
> gives you the total slope of 2.13333 in 4. Generally:
>
> atan(total_slope) = atan(slope_1) + atan(slope_2)
>
> Now imagine someone slowly walking away from you at
> 0.25m/s. Draw a graph of the distance versus time
> and the _slope_ is 1m in 4s. If he sees another
> person walking a little faster in front and _he_
> measures that person's speed as 0.25m/s, then to
> calculate that persons speed as _you_ would measure
> it, you will again get the wrong answer if you add
> the slopes, you have to add the angles. The general
> formula is slightly different due to the geometry:
>
> atanh(total_speed) = atanh(speed_1) + atanh(speed_2)
>
> but qualitatively the principle is exactly the same.
>
> With hindsight, it's so obvious, it's hard to see
> how anyone could miss it ;-)
>
>> ... but then, I'm not psychologist or psychiatrist.
>
> Don't worry, you can understand it with some very
> basic geometry.

</unsnip>

> Not really, I have no degree in psychosis, mine is in math.

That's hard to believe if you claim to find such simple
maths "baffling".

The question remains, have you managed to grasp it yet?

> If I travel at 3c and you travel at 1c, my speed is
> greater than yours , by 3-1 = 2c and

Given:

 V = (u+v)/ ( 1 + uv/c^2)

and:

 V = 3c
 u = 1c

find v.

Hint: The answer isn't 2c.

Saying "If I travel at 3c ..." makes as much sense
as "Assuming sin(x) = 3 ..."

> V = (1+2) / (1 + 2/1) = 1, so if I travel at 3c and you travel at 1c, we
> arrive
> together. I call that psychosis.

I call it innumeracy.

George

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