tag:blogger.com,1999:blog-48750650406012141152024-03-21T09:30:31.176-07:00Not exactly soJoshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.comBlogger19125tag:blogger.com,1999:blog-4875065040601214115.post-81089299172688309332020-02-15T10:16:00.000-08:002020-02-16T08:13:06.366-08:00Floating balloon<style type="text/css">
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<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
An
inflated toy balloon follows an erratic track when the air escapes freely.
Would it be possible to let it float more or less stable in the air
with a controlled outflow? I managed to do exactly that by putting a
(glue stick) cap with a hole in the balloon outlet:<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbcCyAzsDVlUQ7by3TPwP1bRDrq4vFRJ9xexH9ic4zW4X21Ol44aoL0jnzMNsfHEgeNHpeqcM_P0_zan83TeZ1m-STHxiwzRlhat4v4QrBVayYF_jAZDWLwyvJNJiv2a01n_ccp3jkqEs/s1600/Ballon.jpeg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1024" data-original-width="768" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbcCyAzsDVlUQ7by3TPwP1bRDrq4vFRJ9xexH9ic4zW4X21Ol44aoL0jnzMNsfHEgeNHpeqcM_P0_zan83TeZ1m-STHxiwzRlhat4v4QrBVayYF_jAZDWLwyvJNJiv2a01n_ccp3jkqEs/s320/Ballon.jpeg" width="240" /></a></div>
<br />
I
started with a small hole. This did not elevate the balloon. By successively enlarging the hole I came to the point of floating. The mass of the cap makes sure that the balloon floats approximately upright.<br />
<br /></div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
An
interesting question is whether we can calculate that the floating
condition is met. For that, the thrust by the escaping air should equal
the gravitation force on the balloon, the cap and the enclosed air.<br />
<br /></div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
I
measured the following:</div>
<ul>
<li><div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
Diameter
of the inflated balloon: D~ 25 cm.</div>
</li>
<li>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
Diameter
of the hole in the cap: d~ 0.8 cm.</div>
</li>
<li>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
Time
the balloon floated: t~ 10 s. In this time all air escaped.</div>
</li>
<li>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
Mass
of balloon + cap: m~ 3 g.</div>
</li>
<li>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
Over-pressure
in the balloon (measured with a contra/Huygens barometer): 18 mbar=
1800 N/m².</div>
</li>
</ul>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
Assuming
the balloon is spherical, we compute the volume of the balloon as
4/3*pi*(25E-2/2)^3~ 8.2E-3 m^3. The gravitational force on the
balloon, the cap and the mass of the air inside is therefore:</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<br />
Fg~
(8.2E-3 * 1.3 + 3E-3) * 9.8~ <b><i>0.13 N</i></b>.</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<br />
Here the density of air was assumed to be 1.3 kg/m^3. Note
that the mass of the enclosed air is almost 4 times as much as the
balloon+cap mass. One does not notice the air because its weight is balanced by the Archimedean upward force (that's also why a volume of air surrounded by air does not move spontaneously!).<br />
<br /></div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
The
thrust for this case is given by this equation (from <span style="font-family: "liberation" serif , serif;">
</span><a href="https://www.grc.nasa.gov/WWW/K-12/rocket/thrsteq.html">https://www.grc.nasa.gov/WWW/K-12/rocket/thrsteq.html</a>):</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<br />
Ft=
me_dot * Ve + dp * Ae<br />
<br /></div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
The
meaning of the symbols is:<br />
<br /></div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
Ft –
thrust [N]</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<span style="font-family: "liberation" serif , serif;">me_dot –
mass flow rate through the hole [ kg/s ]</span></div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<span style="font-family: "liberation" serif , serif;">Ve –
the air speed just outside the cap [ m/s ]</span></div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<span style="font-family: "liberation" serif , serif;">dp –
the over pressure in the balloon [ N/m² ] </span>
</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<span style="font-family: "liberation" serif , serif;">Ae –
the area of the hole in the cap [ m² ]</span></div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<br />
The
mass flow rate is me_dot~ (8.2E-3 * 1.3) / 10~ 1.1 E-3 kg/s.</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<br />
The
air speed just outside the cap can be computed by imagining the
escaping air forming a cylinder of length L, with the ends having the
area of the hole. The area of the hole is Ae~ pi * (0.8E-2 / 2 ) ^ 2~ 5.0 E-5
m^2. This cylinder goes through the hole in 10 s. So we have:</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<br />
Ve~
(8.2E-3 / 5.0E-5) / 10~ 16.4 m/s.</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<br />
We
are now ready to compute the result of the thrust equation:</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<br />
Ft=
1.1E-3 * 16.4 + 1800 * 5.0E-5~ 1.8E-2 + 9E-2~ <b><i>0.11 N</i></b>.</div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<br />
This
is quite close to the gravitational force Fg~ 0.13 N, notwithstanding
assumptions as that the balloon is spherical, that we can see the escaping air
as a cylindrical volume, etc. Of course, to validate the approach followed, this experiment should be repeated.<br />
<br />
Note that the second term in the last equation is
5 times as large as the first term. This means that the thrust of the escaping air is negligible compared to the thrust due to the pressure difference between the balloon and the surroundings.<br />
<br /></div>
<div lang="en-US" style="line-height: 100%; margin-bottom: 0in;">
<span style="font-family: "liberation" serif , serif;"><br /></span></div>
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</style><br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-29932667490165516542018-06-14T10:41:00.002-07:002018-06-16T03:13:30.666-07:00Civilised contempt<br />
<br />
<span style="font-family: inherit;">Recently I read a book by Carlo Strenger. The Dutch title can be translated as "<span id="result_box" lang="nl">Civilized Contempt - A Guide to Defending Our Freedom".</span> The message of the book is essentially this: according to the author western people are nowadays too afraid of criticizing certain habits and beliefs of people from other cultures. They are too politically correct and too much into cultural relativism ("all cultures are equal"). Strenger's method of "civilized contempt" is to clearly state what views or habits of someone one does not like (the "contempting" part of the title), while at the same time not attacking the person itself (the "civilized"part). Apart from the question whether this separation will be felt as such by the person I wonder whether the book title is a good one. After all, "contempt" is quite a harsh word. I liked to know what the author's view is and therefore I sent the following e-mail to the author on March 17, 2018. Up till now I got no reply.</span><br />
<span style="font-family: inherit;"></span><br />
<span style="font-family: inherit;">---</span><br />
<span style="font-family: inherit;">Dear Prof. Strenger, <br />
<br />
I
read your book "Zivilisierte Verachting. Eine Anleitng
zur
Verteidiging unserer Freiheit", That is, in the Dutch
translation. <br />
<br />
It is clearly written which makes it
easy to agree or
disagree with you. I agree with the latter
part. However,
I have one main objection. One that even puzzles
me. <br />
<span style="font-family: inherit;">
<br />
It is that the title "Ziviliesierte Verachting"
("Beschaafde
minachting" in Dutch) is thus harsh in
my opinion that it
will hamper people to agree with the book
and/or method
or even read the book at all. <br />
<br />
I once
read about research into predicting the breaking up of
marriages.
From taped recording of conversations of
partners it appeared
that contempt being present
was the best predictor for breaking
up. <br />
<br />
I myself automatically relate "minachting"
to irrationality, spitting
on the ground and not being
civilized. Instead of expressing
disdain I would rather say
that I do not agree with someone's
views, reject them, see them
as dangerous, unfruitful, etc.
But I would never use
"minachting". <br />
<br />
An amusing case is yesterday's
reaction of our prime minister's
Rutte's reaction to the most
recent campaign spot of Wilderds'
party PVV. The spot starts
with the words "ISLAM IS" and then
continues with a
few minutes of adding words like "DISCRIMINATION",
"VIOLENCE", "TERROR", etc. See
</span><a href="https://www.pvv.nl/"><span style="font-family: inherit;">https://www.pvv.nl/</span></a><span style="font-family: inherit;">. <br />
<br />
Rutte's
reaction was: "I believe I represent the vast part of
The
Netherlands if I say that I think this is distasteful." <br />
<br />
Well,
maybe a good politician is by definition politically correct.</span></span><br />
<span style="font-family: inherit;"><span style="font-family: inherit;"><span style="font-family: inherit;">Nevertheless, my question is: don't you think your book's
title is
counter productive? <br />
<br />
Yours sincerely, <br />
Jos
Groot</span></span></span><br />
<br />
<span style="font-family: inherit; font-size: xx-small;">--- </span><br />
<span style="font-family: inherit;"><br /></span><br />
<div style="text-align: center;">
<a href="https://craigssenseofwonder.files.wordpress.com/2014/02/unknown.jpeg"><img alt="I love this cartoon for the simplicity!" class="size-medium wp-image-1930" data-attachment-id="1930" data-comments-opened="1" data-image-description="" data-image-meta="{"aperture":"0","credit":"","camera":"","caption":"","created_timestamp":"0","copyright":"","focal_length":"0","iso":"0","shutter_speed":"0","title":""}" data-image-title="Unknown" data-large-file="https://craigssenseofwonder.files.wordpress.com/2014/02/unknown.jpeg?w=308" data-medium-file="https://craigssenseofwonder.files.wordpress.com/2014/02/unknown.jpeg?w=300&h=159" data-orig-file="https://craigssenseofwonder.files.wordpress.com/2014/02/unknown.jpeg" data-orig-size="308,164" data-permalink="https://craigssenseofwonder.wordpress.com/2013/02/14/critical-thinking-common-informal-fallacies-part-2/unknown-3/" height="212" sizes="(max-width: 300px) 100vw, 300px" src="https://craigssenseofwonder.files.wordpress.com/2014/02/unknown.jpeg?w=300&h=159" srcset="https://craigssenseofwonder.files.wordpress.com/2014/02/unknown.jpeg?w=300&h=159 300w, https://craigssenseofwonder.files.wordpress.com/2014/02/unknown.jpeg?w=150&h=80 150w, https://craigssenseofwonder.files.wordpress.com/2014/02/unknown.jpeg 308w" width="400" /></a></div>
<div style="text-align: center;">
<br /></div>
<div style="text-align: center;">
<br /></div>
Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-30258018814815486082017-02-28T13:08:00.001-08:002017-02-28T13:08:43.004-08:00The value of a book is in my head, not in the text<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4ZmKtjgKE3on6UydiOLyG4PBpuNPL54hQnB1y7bp0x9nGMS3WW0py7QMyRyXNm9GYhVlazIooM8nUWGzmbi2XcuvTsBwTMuhsf5Jx3w9ABmxYEsX3yh5e6jA_nPXV3aCDlzI4si9Nrrg/s1600/book.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4ZmKtjgKE3on6UydiOLyG4PBpuNPL54hQnB1y7bp0x9nGMS3WW0py7QMyRyXNm9GYhVlazIooM8nUWGzmbi2XcuvTsBwTMuhsf5Jx3w9ABmxYEsX3yh5e6jA_nPXV3aCDlzI4si9Nrrg/s320/book.jpg" width="287" /></a></div>
<br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-33549863191351393492017-02-17T05:46:00.000-08:002017-02-23T10:14:03.161-08:00The Myth Of The Myth Of Religious NeutralityNow and then I read a book that goes against my own beliefs, in an attempt to not getting stuck in these beliefs. My experience is that this practice stimulates my thinking more than reading just another book that is in line with those beliefs and hence gives me pleasant feelings only. The most recent example is 'The Myth of Religious Neutrality' with the sub title 'An Essay on the Hidden Role of Religious Belief in Theories', by Roy A. Clouser (1991). I must admit I did not read it entirely – I speed red some of the later chapters - because I was mostly interested in the claim of the (sub) title: that theories are based on religious belief.<br />
<br />
At first sight this claim is not unreasonable. Theories seem to me always based on some beliefs, albeit reasonable beliefs. For example belief in the validity of the logic used. But why should these beliefs be religious? Can Clouser proof the claim of the hidden role of religious belief?<br />
<br />
Clouser was a professor of philosophy and religion. His book is therefore systematic, quite profound, focusing on fundamentals and therefore not for the faint of heart. Although he is clearly a Christian, he is not a 'fundamentalist' which is according to him someone who holds the 'encyclopedial assumption'. This assumption entails 'that sacred Scripture contains inspired and thus infallible statements about virtually every conceivable subject matter'. This was centuries ago a common view point. In stead, Clouser believes in a more subtle but very fundamental influence: Scripture does not dictate the contents of theories directly, but provides the basic assumption(s) they are based on. Hence the 'hidden role' of religious belief. Throughout the book it becomes apparent that this belief should better come from the Bible, according to Clouser.<br />
<br />
How does Clouser proceed to prove the claim of the (sub) title? He starts out with some pleasantly clear, concise definitions. The one of 'religious belief' is a case in point: 'a religious believe is any belief in something or other as divine.' In this 'divine' means 'having the status of not depending on anything else', in other words, being self-existent. The Christian God is an (the only?) example. Three chapters are devoted to showing that theories in mathematics, physics and psychology are all based on a religious belief. That is, pagan beliefs, according to – again - his definition: a pagan belief is a belief that the divine is some part of the (God-)created universe, in other word, 'reality'. He gives as an example in physics Einstein's theoretical foundation. That is his (supposed) believe that the laws of logic and mathematics govern all reality (including human thought). This means that they are self-existent and thus divine. Hence Einstein's view is religious. In addition, because logic and mathematics are part of reality his religious belief is pagan. <br />
<br />
In fact, this ends the part of the book 'proving' the claim of the (sub) title. Is the proof valid? I do not think so. A major weak point is that the claim is based on self devised definitions. One can proof anything from properly constructed definitions. Take the definition of the divine being self-existent: it is questionable whether there are non-hypothetical independent entities at all (of course the Christian God is an example according to Clouser). The 'religious' creeps in through this questionable definition.<br />
<br />
After having shown that current theories make the wrong – pagan - assumptions Clouser devotes later chapters to biblical theories of reality and society. He skips mathematical, physical and psychological theories for two reasons: he does not have enough knowledge and his own 'theory of reality' comes into its own in social theories. The skipping further weakens his position.<br />
<br />
In the afterword Clouser questions whether his religious, Biblical view does not divide people. He thinks this is not the case, again for two reasons. The first is that giving fundamental reasons for differences between theories will not lead to intolerance. Secondly, these reasons will bring forth a fruitful communication. What he does not mention is that he says that the Christian Bible provides the best ground for theories to be based on, which of course has the potential to divide people.<br />
<br />
Clouser states that 'Having the right God is basic to all truth'. This looks to me as a basic assumption of himself. It seems to be the inspiration of his theory and the book in which it is described. A book which is unusual, faulty and nevertheless (or therefore?) thought provoking.<br />
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgd87NOoTbUZGsdTd5EpMpqx0iimq1mycTM7SqVRLmoABHLuQ-Q0v8CkdPk6DU9p2lsClM-9YwE4Vga-kHWMJxDLA2V-jqWUlnSlqb8aT3a7Iu5y1iBMo6IAgf00_tz13XjjyUluAUjU0s/s1600/Biggest-bias.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="241" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgd87NOoTbUZGsdTd5EpMpqx0iimq1mycTM7SqVRLmoABHLuQ-Q0v8CkdPk6DU9p2lsClM-9YwE4Vga-kHWMJxDLA2V-jqWUlnSlqb8aT3a7Iu5y1iBMo6IAgf00_tz13XjjyUluAUjU0s/s320/Biggest-bias.jpg" width="320" /></a></div>
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Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-271471924030844212015-04-25T11:27:00.001-07:002015-05-12T05:04:44.754-07:00The tangent shaped track of a rain drop on a slanted tubeThis picture made me think:<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQvTZVw_BIirj6N5R-yI1SaC7hwQix68WrenOVXJMXbypUfiYl0qSpQXGQ7IuyXJM7A9q4yI1uPj9t28W6TGCQuruhUutDeRLq7CzchEUJJh3dEPXUCJR05fnMSLzrWlAPy4Gonb0Th_Q/s1600/P1020534.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQvTZVw_BIirj6N5R-yI1SaC7hwQix68WrenOVXJMXbypUfiYl0qSpQXGQ7IuyXJM7A9q4yI1uPj9t28W6TGCQuruhUutDeRLq7CzchEUJJh3dEPXUCJR05fnMSLzrWlAPy4Gonb0Th_Q/s1600/P1020534.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 1 - Constellation of metal tubes.</td></tr>
</tbody></table>
I took it on a railway station. The constellation of metal tubes keeps the first floor up in the air. A close up of the central tube makes clear what attracted my interest:<br />
<br />
<div class="separator" style="clear: both; text-align: left;">
Look at the black tracks. Apparently rain drops fall down on the tube and create these dirt tracks while on their way down. All tracks converge to the gray strip.</div>
<br />
I wondered whether it would be possible to compute the track of a drop. This is a typical physics problem. It turned out to be possible, as these pictures demonstrate:<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMK0EoVnb81WMQczma4k5dZFasP1zNo-CTKjXc-E8NoA2PNPq3ccPxpIwn6A3shJ4NdNgaVLUsXpKJ53AAOCiXskLHjRmUcv7FDqEY097umomgMkSjLe-3RHIdj8dCpS3ytiJ-TUEz64g/s1600/P1020535.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMK0EoVnb81WMQczma4k5dZFasP1zNo-CTKjXc-E8NoA2PNPq3ccPxpIwn6A3shJ4NdNgaVLUsXpKJ53AAOCiXskLHjRmUcv7FDqEY097umomgMkSjLe-3RHIdj8dCpS3ytiJ-TUEz64g/s1600/P1020535.JPG" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 2 - Close up of Fig. 1.</td></tr>
</tbody></table>
<br />
The tube at the left is a different one than above and oriented vertically, to ease analysis. The blue track at the right resulting from theory resembles the track shape quite well. Note that it starts at the top at a position at the 'back' of the tube, visible in the plot right but invisible in the picture left.<br />
<br />
Surprisingly, it turns out that the track resembles the plot of a tangent function. Straight lines, parabolas, circles, ellipses, sines, exponential functions and others - I know where one can literally see them in the real world. To my knowledge this drop track is the only example of a tangent function coming to life. Let's proceed to sketch the proof of this.<br />
<br />
I used the Lagrangian formalism to solve the problem. This formalism is a generalization of Newton's laws. It allows one to use a suitable coordinate system, to handle constraints and to include frictional forces. For the latter I used a force which is linearly proportional to the speed of a drop. This is probably wrong, nevertheless it gives the reasonable result of above. Possibly the solution is not very sensitive to the type of friction one uses, as long as it leads to a constant velocity. Experiments show that drops move at a constant speed over an inclined surface.<br />
<br />
For such a cylindrical problem it is only natural to use cylindrical coordinates (<i>z</i>, <i>phi</i>). The angle <i>phi</i> varies from 0 to 2x<i>pi</i> when traversing a circle at constant <i>z</i>. Surprisingly, when the friction is relatively large the problem can be solved analytically. These equations for the motion result in this case:<br />
<br />
<i>z</i>= <i>c1</i> * t<br />
<br />
<i>phi</i>= 2 x atan(exp(-<i>c2</i> * <i>t</i> + <i>c3</i>))<br />
<br />
<i>t</i> is time in seconds. atan(<i>x</i>) is the inverse of tan(<i>x</i>). The constants are:<br />
<ul>
<li><i>c1</i>= -<i>mg</i>cos(<i>theta</i>)/<i>k</i>; <i>m</i>= drop mass [kg], <i>g</i>= gravitational acceleration (~9.8 m/s²), the frictional constant [kg/s], <i>theta</i>= the angle of the tube symmetry axis w.r.t. the direction of the gravitational force [deg].</li>
<li><i>c2</i>= <i>mg</i>sin(theta)/(<i>kr</i>); <i>r</i>= tube radius [m]</li>
<li><i>c3</i>= defines <i>phi</i> at <i>t</i>= 0 s.</li>
</ul>
<div>
Apparently the drop travels at constant speed <i>c1</i> in the -<i>z</i>-direction, down the tube. No acceleration, hence no net force is excerted on the drop. This occurs because the frictional and gravitational force cancel each other.This is similar to a snow flake that falls at constant speed during quiet winter weather. <br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMokvS9F0O-hNZqwqE9hcdBpstugedx3FIec3Zh8kgQlqpyUZD_KqntO3UcHdyDxFTM2guBxE-yUhiAfahq5vmW1z0YUSUQhYCzyUT2M7L3oDBQgLYNqbuIuX9EscS_8QWWwsynqkC0ks/s1600/Druppel3.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="508" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMokvS9F0O-hNZqwqE9hcdBpstugedx3FIec3Zh8kgQlqpyUZD_KqntO3UcHdyDxFTM2guBxE-yUhiAfahq5vmW1z0YUSUQhYCzyUT2M7L3oDBQgLYNqbuIuX9EscS_8QWWwsynqkC0ks/s1600/Druppel3.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 3 - Tube pictured such that it appears to be vertical (left) and the theoretical result (right). Due to the rotation the gravitational force is directed parallel to the vector pointing from (0, 0, 0) to (0, 1, -1). I.e., the force vector points <span style="font-size: 12.8px;">t</span><span style="font-size: 12.8px;">owards the reader, d</span><span style="font-size: 12.8px;">own right.</span></td></tr>
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I guessed reasonable values for the parameters like the mass and tuned them subsequently to get reasonable resemblance between the analytic solution and the picture. The plots of <i>z</i> (left) and <i>phi</i> (right) I got are:</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjF56tYm1w081RPcKk95rBrFVjnMAN4i_Rzjvz0qlWO23MhfYTgCurCDaH9Q0Ip2napjVk91-e5PkTR_xDXKzQu0O_uOwO7Nq8nMkcjmhDLQNBIcLDPoyf8_77aByoM6c4VYK0Znot90ls/s1600/TwoPlots.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjF56tYm1w081RPcKk95rBrFVjnMAN4i_Rzjvz0qlWO23MhfYTgCurCDaH9Q0Ip2napjVk91-e5PkTR_xDXKzQu0O_uOwO7Nq8nMkcjmhDLQNBIcLDPoyf8_77aByoM6c4VYK0Znot90ls/s1600/TwoPlots.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 4 - Plot of the cylindrical coordinates <i>z</i> (left) and <i>phi</i> (right) as a function of time <i>t</i>.</td></tr>
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The blue curve of Fig. 2 (right) results from transforming these to (<i>x</i>, <i>y</i>, <i>z</i>) coordinates and plotting the result. <em>phi</em> asymptotically approaches 0 degrees. This corresponds to the dark band of Fig. 1 (left)where all drops converge to.<br />
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Note that one can recognize the tangent function in the right plot. This is due to the fact that atan(exp(<i>t</i>)) is approximately equal to a shifted and scaled version of atan(<i>t</i>) and hence the two have nearly the same shape. Because <i>z </i>is proportional to <i>t</i>, the track of drops on a tube thus resembles the tangent function. Check for yourself in the right plot of Fig. 3. As said before, this is the only case I know of where this function is visible in the real world.<br />
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A note on programs: I used Wolfram Alpha (<a href="https://www.wolframalpha.com/">https://www.wolframalpha.com/</a>) to solve the differential equations and Octave (<a href="https://www.gnu.org/software/octave/">https://www.gnu.org/software/octave/</a>) on Linux Mint (<a href="http://www.linuxmint.com/">http://www.linuxmint.com/</a>) to visualize the solution. The best things in life are free (<a href="https://www.youtube.com/watch?v=-GoYa1uNhYs">https://www.youtube.com/watch?v=-GoYa1uNhYs</a>)!</div>
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<br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-55163930436179951332015-02-28T02:24:00.000-08:002015-03-02T13:20:42.611-08:00The road to reality - or beyond?I held Roger Penrose's book “Road to reality” popularizing physics highly but I changed my my view a bit. This was due to discussing his short article “On the second law of thermodynamics” (1994) with some philosophy of physics students.<br />
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The article deals with the second law of thermodynamics. This law states that the entropy - the amount of disorder - of a closed system on average increases with time. It implies that the entropy of the universe goes up in the future. But what about the past? Penrose's solution is his "Weyl curvature hypothesis". This hypothesis states that the Weyl curvature is zero (or at least very small) at the Big Bang, and with it the entropy. More important than knowing what Weyl curvature is, is understanding what it explains:<br />
<ol>
<li>The existence of the aforementioned second law.</li>
<li>The observation that the universe is homogeneous and isotropic at large scales.</li>
</ol>
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The far more popular and rivaling inflation theory explains only 2. </div>
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From the discussion it became clear that entropy has different definitions. The well established definition by Boltzmann is suited for the computation of the entropy of a gas. But what about that of the universe as a whole? Cosmology seems quite speculative.</div>
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<div>
Penrose is a good popularizer of mathematics and physics. His accompanying illustrations are unique. However, the danger is that the uninformed readers (as his readers will generally be) are seduced to see his speculative theories as being main stream. This occurs because he starts out in his books with accepted mathematical and physical material, slowly introducing his own speculations after that. Like the hypothesis of above and also his twistor theory. </div>
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The question is whether Penrose leads one to reality or beyond.</div>
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Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-66498761309171115802015-01-27T10:46:00.003-08:002015-02-15T04:48:20.019-08:00Two ways of "counting infinity"Do these sets have the same size? :<br />
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<div style="text-align: center;">
{1, 2, 3} and {1, 4, 9}</div>
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Is your answer the same if we extend the sets indefinitely, like this? :<br />
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{1, 2, 3, 4, ...} or {1, 4, 9, 16, ...}</div>
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Probably you determined the size by counting the number of elements in answering the first question. The sets {1, 2, 3} and {1, 4, 9} have each 3 elements so the answer to the first question is: yes, the two sets have the same size.<br />
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How to count the two infinite sets of the second question? This is impossible using conventional 1, 2, 3, --- counting. It would not end. Mathematician Cantor therefore proposed a method to find out whether two infinite sets have the same size, a way of “counting infinity”:<br />
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<div style="text-align: center;">
<i>If we can pair all the elements of two sets than they have the same size. </i></div>
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Because we can pair like this: {1, 1}, {2, 4}, {3, 9}, {4, 16}, ... Cantor's answer to the second question is the same as to the first: yes, the two sets have the same size. His method also works for finite sets, by the way. As such it is a generalization of the finite case.<br />
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But wait... something strange is going on. The set {1, 4, 9, 16, ...} is a proper sub set, a part of {1, 2, 3, 4, …} (not the same, hence “proper”). Nevertheless they have the same size. How can that be?<br />
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A mathematician's response might be that we should not speak of the <i>size</i> of a set but of its <i>cardinality</i> instead. That's the word Cantor introduced. This makes clear that we are dealing with the mathematician's world which differs from the ordinary world. In the ordinary world proper sub sets of a set are always smaller than the set - and infinite sets cannot be counted in this world. In mathematics proper sub sets of an infinite set can have the same <i>cardinality</i> as that set. Not the same <i>size</i>, which is just an everyday, non mathematical word.<br />
<br />
So in the mathematical world it seems that we gain something - cardinality as a measure for the size of sets - and we loose something: that proper sub sets of a set are always 'smaller' than that set.<br />
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This is a kind of friction I was uneasy with for decades. I realized myself all too well the difference between 'size' and 'cardinality' of above and especially the more or less arbitrary choice of Cantor's pairing principle. Would another, maybe better choice be possible?<br />
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It felt as an impasse to me but probably not to William Byers, the author of the book 'How mathematicians think - using ambiguity, contradiction, and paradox to create mathematics'. His main point is that ambiguity etc. - things that somehow do not feel right - stimulate the formation of new mathematical ideas. Difficulties advance mathematics.<br />
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This is not an idea pertaining exclusively to mathematics. For example, koans are the Zen equivalent given by zen masters to their pupils. These are paradoxical puzzles like: “"What is the sound of one hand clapping?" To solve these one has to widen one's view of the world. A poetic, musical analog is this line from Leonard Cohen's song "Anthem": “There is a crack in everything. That's how the light gets in.” Imperfections are necessary for advancement, seems to be the suggestion.<br />
<br />
Back to the original problem regarding infinity. How was it solved? About 100 years after Cantor the theory of “numerosities” was proposed by Vieri Benci. Like cardinality the numerosity is a measure for the size of a set. An important difference is that proper sub sets of a set have always a smaller numerosity than that set (while the cardinality can be the same).<br />
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Some more information can be found here: <a href="http://www.newappsblog.com/2014/03/counting-infinities.html">http://www.newappsblog.com/2014/03/counting-infinities.html</a>. From the discussion there it appears to me that numerosity is a more complicated concept than cardinality – but I can be wrong.<br />
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<br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-1964299307377593272015-01-19T10:36:00.001-08:002015-01-20T00:59:11.903-08:00'Mind and cosmos' by Thomas NagelMany people - and especially scientists - think that our current knowledge is sufficient to explain current life. Doubting the theory of evolution is not done. Nevertheless, this is exactly what philosopher Thomas Nagel does in his small book 'Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature is Almost Certainly False' (<a href="http://opinionator.blogs.nytimes.com/2013/08/18/the-core-of-mind-and-cosmos/?_r=0">http://opinionator.blogs.nytimes.com/2013/08/18/the-core-of-mind-and-cosmos/?_r=0</a>).<br />
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Neo-Darwinism implies that the combination of mutation and natural selection (darwinism) drives evolution. It does not explain the existence of non material aspects of life like consciousness, cognition and value. This is no surprise, because science does not include these aspects.<br />
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Nagel pleas for looking for a naturalistic theory that describes the order that governs the natural world from the inside out. That is, a theory without supernatural elements. The order should lead without surprises and maybe inevitably to consciousness, cognition and value. Non material matters might also exist in some form in the beginning to evolve from there.<br />
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After investigating several solutions Nagel concludes with a teleological theory as feasible and the most probable. Teleology dates back to Plato and Aristotle. It states that development is aimed at a goal or purpose. This in contrast to ordinary causality, where effects follow causes. Teleology could in this case work by guiding mutations such that life as we know it arises in time. This guiding is necessary because Nagel beliefs that neodarwinism is 'too slow' for the development of life as we know it. The teleological guiding law would be just another natural law.<br />
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The book surprised many people because Thomas Nagel is a respected,
atheistic philosopher. Teleological views do not fit into this picture.
The book is rejected by many if not most philosophers.<br />
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The book is interesting to me because I belief already quite some time that neodarwinism is too slow and could be repaired by a teleological 'fix'. It is therefore a pity that the book is difficult to read and understand - at least for me. There are many long sentences and it lacks a decent summary of the main lines of reasoning. Taking more time for reading it would increase my understanding. However, I will not do this because I seriously doubt whether philosophy can contribute much conclusive to this subject. Maybe science should come to the rescue again?<br />
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<br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-30194488570241362732015-01-10T03:07:00.000-08:002015-01-10T04:25:22.100-08:00IDEOLOGIES and ideologiesLast week about twenty people were killed in Paris due to a clash of two ideologies: one religious and one of free speech.<br />
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Friday morning I boarded a rush hour train to Leiden. I sat down opposite to a young woman with a black headscarf. She telephoned softly while the Metro (a free newspaper) was lying opened in front of her on the small window table. I was curious and turned my head slightly to see if she was reading about the Parisian affair. That was not the case. Then, while continuing calling, she rearranged her newspaper and with small shocks pushed the underlying Metro in my direction. <br />
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Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-70021354710602968352014-12-19T04:27:00.000-08:002014-12-31T02:28:21.540-08:00Why you should not read this!<div class="separator" style="clear: both; text-align: left;">
You should not read this because you are using digital media right now which causes symptoms of dementia, according to Manfred Spitzer in his book "Digitale dementie" (in Dutch; in English the title would probably be "Digital dementia"). He is very negative about the use of digital media:</div>
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"Digital media cause us to use our brain less so that the intellectual performance decreases over time. It even hampers brain development in young people; so right from the start the intellectual capacity stays under the attainable level. This does not only concern our thinking, but also our will, emotions and above all our social behaviour. These effects haven been already demonstrated often and proceed along different mechanisms clarified by research, especially brain research."<br />
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The book is a cascade of research results against digital media use and lacks a balanced view. He does not mention any advantages. In my view he misses at least three important general points.<br />
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The first is that the future is made right now. If people - and especially children - use digital media now they will do so in the near future. The balance of human capacities change over time, which is nothing new. For example, people get currently worse at hand writing and better at typing. Typing skills are what the future needs, more than hand writing. How many people nowadays use a quill pen to write? You'd better go with the flow in order to fit into the future world. <br />
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The second point is that people try to push their abilities to the limits. So if one loses the ability of fine coordination as learned from hand writing, something will substitute for that. This does not hold for all people, of course. That is what the last point covers.<br />
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The last point is that what people do with a new thing or idea depends foremost on their traits instead of the novelty itself. For example, lazy people tend to do "lazy things" with a car or a computer, moderate people make moderate use of tablets and cell phones, etc. The virtues and vices of people (<a href="http://en.wikipedia.org/wiki/Outline_of_self">http://en.wikipedia.org/wiki/Outline_of_self</a>) become apparent in the use of things and ideas, quite independent of those things and ideas.<br />
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<br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-29065183512872611072014-12-01T14:13:00.000-08:002014-12-06T15:41:31.651-08:00What the world is made ofEver wondered what the world is made of at the lowest level? Are particles the ultimate building blocks? Or fields? A combination of particles and fields? Or... structures? There are people that are investigating the possibility that structure is all there is. No particles, no fields, structures only. Only relations between - yes, between what, exactly? It is easy to give a mathematical example of a structure. For example the structure consisting of this simple relation: being separated by 1. This generates the integers -3, -2, -1, 0, 1, 2, ... and many other examples. Note that only the relation of being separated by 1 is essential. The numbers -3, -2, ... are not. They can be seen as mere positions, place holders. Not as objects.<br />
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I tried to imagine physical reality to be based on structures only. No particles, no fields, nothing of those. This is much more difficult than the previous mathematical example of a structure. After all, we live in a world in which we experience (see, touch, measure, ...) objects like dogs, trees, etc. Objects that may stand in certain relations to each other, like "the dog is 2 meters to the left of the tree". So what we experience in our daily lives are objects that form a structure: objects + structure. Not structure only. To make it plausible that our physical world can be thought of as being made of structures only I will first discuss a mathematical example, the Cantor set. See also: <a href="http://en.wikipedia.org/wiki/Cantor_set">http://en.wikipedia.org/wiki/Cantor_set</a>.<br />
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To construct the Cantor set we start with a black line segment extending from 0 (left) to 1 (right). This is the top line segment of this figure:<br />
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The second step is to remove the middle third of this segment without the end points. This leaves the two line segments [0, 1/3] and [2/3, 1] of the second line from the top. The third step is to remove the middle thirds from [0, 1/3] and [2/3, 1] in a similar fashion. This gives the four line segments of the third line. Proceeding in this way gives an ever larger number of ever smaller segments. The Cantor set is what remains after an infinite number of iterations. It consists of a large number of points, <i>not</i> segments. For example the points 0, 1, 1/4 and 3/10 belong to the set. In fact the Cantor set contains an uncountable number of points: it has the same cardinality as the length 1 segment we started with. The cardinality is the mathematical measure for the number of points of a set.<br />
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There is a significant difference between the results after a finite number of iterations and the Cantor set. After a finite number of iterations we got a structure and objects. The
objects are the line segments of the picture which have a property: their length. However, the Cantor set consist of points only. Points have no properties, they only indicate a position. So to me the Cantor set seems to be a nice example of a structure without objects.<br />
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Now for the physical example. I see a parallel with the physical world. At the scale of everyday life we see for example a person to which we can attribute a multitude of properties: length, weight, hair colour, left eye colour, right eye colour, etc. Zooming in it seems that the number of properties decreases. For example, an electron is thought to be a point particle with only three properties: mass, charge and spin. Also at the atomic level we see mostly empty space with atoms and electrons scattered throughout. This suggests that at smaller scales we lose properties and gain empty space. Maybe if we zoom in deeper and deeper the limit is what the Cantor set is: a structure without objects.<br />
<br />
We can also go the other way by zooming out. Imagine we look at the Cantor set with a microscope with a certain spatial resolution. All the holes between points with are larger than the resolution will be filled up. This gives one of the iterates above, which consists of segments. So a structure becomes visible as a structure with objects. Because we always probe nature at a finite resolution we always experience objects. This can be generalised from the Cantor set to a general set of points.<br />
<br />
The above speculations (which are not entirely water tight, I admit) lead to an amusing thought: that if we zoom in on matter every time we see some object that we like "to get our hands on" it falls apart in separate smaller objects. And at the bottom level there is structure only. No objects. Only a mathematical description of a structure. People advocating that "everything is mathematics" will probably love this view.<br />
<br />
Finally, a famous saying is "we are star dust" because a person's mass consists for approximately 93 % of elements produced in stars. Dust is often taken as a model for a set of points. "We are star dust" remains true from the above structural point of view albeit in a different sense.<br />
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<br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-62664421899307047552014-11-29T01:14:00.000-08:002014-11-30T03:00:35.480-08:00Change your money for a better worldEver went weak at the knees and felt the urge to make the world socially just and more sustainable? The book "Een @ander soort geld" ("A different kind of money"; <a href="http://www.strohalm.nl/eenandersoortgeld.html">http://www.strohalm.nl/eenandersoortgeld.html</a>) by Helen Toxopeus promises a solution: an alternative to the current money system.<br />
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<br />
The underlying idea is to change the rules of the economic game, by using a different kind of money than we currently do. Think of changing the rules of Monopoly which will inevitable change the course of the game. It is done by using software (Cyclos: <a href="http://en.wikipedia.org/wiki/Cyclos">http://en.wikipedia.org/wiki/Cyclos</a>) that controls the way virtual money ("credits") is used. Two important characteristics are: <br />
<ol>
<li>It puts a penalty on (or makes it impossible to) spending credits too soon outside the local community. Hence it limits globalization. </li>
<li>Tax has to be paid for credits that are not spent. This will prevent the rich from becoming too rich and at the same time stimulate the economy.</li>
</ol>
As a physicist I am able to compute the behaviour of simple dead systems like falling objects and oscillating pendulums. Therefore I shiver at the thought of modelling complex economical systems "running on" a large number of living people embedded in a dynamical environment while at the same time having the boundary conditions of being socially just and sustainable. Therefore I was glad to see that (variants of) the system were already tried out and continue to be tried out. <br />
<br />
Toxopeus based her book on a series of interviews with Henk van Arkel, who pioneered alternative money systems and is CEO of STRO, "Social Trade Organization" (English: <a href="http://www.socialtrade.org/">http://www.socialtrade.org/</a>; Dutch: <a href="http://www.strohalm.nl/index.php">http://www.strohalm.nl/index.php</a>). The way our current money system works is explained in some detail. Like the way it is created and what the consequences of interest are. Interest is seen as a big evil. Several alternative systems and experiences with them are described. This is mixed with a sketch of Toxopeus' own development from being a banker at ABN AMRO via gaining interest in crowd funding to her current positions as a researcher in the field of innovation and sustainability in money- and exchange systems. This mix of the factual and the personal makes the book more accessible. The (former) banker questioning van Arkel is a good way to understand van Arkel's ideas for the average reader who grew up with the usual money system. The book actually has a second, more formal and detailed part by van Arkel himself. As a whole it makes for an interesting and entertaining read. It is currently under translation. In line with the content of the book one can get it for free. Payment is not needed if it is returned or passed on to another reader. Only if one keeps it payment is expected.<br />
<br />
I think it is good that alternative money systems are being invented, implemented and tested. Maybe not to change the current money system entirely but as being complementary. There is a theory that a mixture of money systems stabilizes a society.<br />
<br />
I have some criticism on this particular alternative money system:<br />
<ol>
<li>In the system it is impossible to save credits for the time when you are not able to work any more. So at that age you see your (limited) savings steadily evaporate while not being supplemented.</li>
<li>Stimulating spending credits (I saw an example interest of 6 %/year on savings) stimulates working. Isn't this the same as having to work for a mortgage, putting an unwelcome pressure on people? </li>
<li>Who is "turning the knobs" in Cyclos? For example, who defines interests?</li>
<li>It seems that some parameters like the interest are fixed. In the current system the interest is at least more free. Is this additional degree of freedom not necessary for a system to adjust to varying circumstances?</li>
<li>I came across three "van Arkels": the aforementioned Henk, his
brother Jan van Arkel who is the publisher of the book and a certain
Roder van Arkel, "project manager Cyclos". I do not know for sure
whether Roder is family of the other two. Probably new ideas have a
tendency to originate from a group of closely related people. However,
if things grow bigger it is not advisable to keep such a group
regulating the money system, the software and the press.</li>
<li>If I borrow my lawn mower to my neighbour. As a consequence I cannot use it for some time, it ages, and my neighbour has the advantage of its use and not having to have one. Isn't this enough reason to expect some kind of "interest" from my neighbour? Doesn't the same hold for money?</li>
</ol>
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<ol></ol>
Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-22777601408498664972014-11-16T06:57:00.001-08:002014-11-16T10:23:00.927-08:00Only two races<style type="text/css">blockquote { direction: ltr; color: rgb(0, 0, 0); }blockquote.western { font-family: "Liberation Serif","Times New Roman",serif; font-size: 12pt; }blockquote.cjk { font-family: "Droid Sans"; font-size: 12pt; }blockquote.ctl { font-family: "Liberation Sans","Arial",sans-serif; font-size: 12pt; }p { margin-bottom: 0.25cm; direction: ltr; color: rgb(0, 0, 0); line-height: 120%; }p.western { font-family: "Liberation Serif","Times New Roman",serif; font-size: 12pt; }p.cjk { font-family: "Droid Sans"; font-size: 12pt; }p.ctl { font-family: "Liberation Sans","Arial",sans-serif; font-size: 12pt; }a:link { }</style>
<br />
<div class="western">
A citation by the late neurologist and psychiatrist Victor Frankl to start with:<br />
<blockquote class="tr_bq">
From all this we may learn that there are two races of men in this
world, but only these two—the “race” of the decent man and the “race” of
the indecent man. Both are found everywhere; they penetrate into all
groups of society. No group consists entirely of decent or indecent
people. In this sense, no group is of “pure race”—and therefore one
occasionally found a decent fellow among the camp guards. </blockquote>
This is what Victor Frankl wrote in his book "The
meaning of life", in which he described how he survived
the Holocaust.<br />
<br />
His dichotomy also holds for Muslims. The
rise of IS emphasizes this. Every two months I talk in The Hague with some Muslims from the
Lahore Ahmadiyya movement (<a href="http://en.wikipedia.org/wiki/Lahore_Ahmadiyya_Movement_for_the_Propagation_of_Islam">http://en.wikipedia.org/wiki/Lahore_Ahmadiyya_Movement_for_the_Propagation_of_Islam</a>). They interpret the word "jihad"
as striving for something good or opposing against something bad. Different forms of jihad exist: suppression of bad desires to get nearer to God,
persistence in believing, mission work and that of war. This last, armed jihad is only allowed under special circumstances.
For example for self defence, on behalf of a legal
government, etc. According to the Lahori's the way the media use "jihad" and "jihadist" is often misleading.<br />
<br />
There is nothing new under the sun. A religion or other ideology (think of communism) is based on a book, which is interpreted such by one group and so by
another. Sometimes just in a way that suits one best, leading to
misunderstanding and conflicts. Already a few thousands year ago Seneca the Younger noted that religion - and feel free to generalize "religion" to "belief" or "ideology" - is highly ambiguous:<span class="st"> </span><br />
<blockquote class="tr_bq">
<span class="st"></span><span class="st">Religion is regarded by the common people as true, by the wise as false, and by the rulers as useful.</span></blockquote>
--<br />
<br />
Since I wrote this the Ahmadiyya Lahore Movement organised a meeting to explain things. See (in Dutch):<br />
<br />
<a href="http://www.omroepwest.nl/nieuws/25-09-2014/wat-de-ware-jihad-haagse-moskee-geeft-uitleg">http://www.omroepwest.nl/nieuws/25-09-2014/wat-de-ware-jihad-haagse-moskee-geeft-uitleg</a><br />
<br />
and<br />
<br />
<a href="http://www.omroepwest.nl/nieuws/28-09-2014/tientallen-mensen-ge%C3%AFnteresseerd-jihad-uitleg-den-haag">http://www.omroepwest.nl/nieuws/28-09-2014/tientallen-mensen-ge%C3%AFnteresseerd-jihad-uitleg-den-haag </a><br />
<br /></div>
Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-84086536135065909342014-11-09T13:21:00.000-08:002014-11-10T09:47:10.441-08:00Don't blame the battery too soonMy Nokia 100 phone was not able to charge its empty BL-5CB battery any more. The phone shop employee I consulted blamed the battery and advised to replace it. This type of battery can go through hundreds of charge-discharge cycles so I suspected something different was going on. My idea was that the phone was not able to charge the battery because of the empty battery state, probably the voltage being too low. I chose to increase it a bit by heating it in a hot air stream. This solved the problem: my phone is up and running again.<br />
<br />
Of course one should be cautious with heating batteries. A safer but somewhat more complicated method is to charge the battery a little in an external battery charger: <a href="http://klkl.co.uk/2008/08/10/help-my-phone-wont-charge-heres-the-solution/">http://klkl.co.uk/2008/08/10/help-my-phone-wont-charge-heres-the-solution/</a>.<br />
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<br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-77224727296877491722014-11-09T04:36:00.000-08:002014-11-10T10:27:50.195-08:00On future physical theories<style type="text/css">p { margin-bottom: 0.25cm; direction: ltr; color: rgb(0, 0, 0); line-height: 120%; }p.western { font-family: "Liberation Serif","Times New Roman",serif; font-size: 12pt; }p.cjk { font-family: "Droid Sans"; font-size: 12pt; }p.ctl { font-family: "Liberation Sans","Arial",sans-serif; font-size: 12pt; }a.cjk:link { }a.ctl:link { }</style>
<br />
Philosopher of physics Dennis Dieks (<a href="http://en.wikipedia.org/wiki/Dennis_Dieks">http://en.wikipedia.org/wiki/Dennis_Dieks</a>) gave a talk in Dutch on expectations he has for the future of physical theories:<br />
<br />
<a href="http://www.sg.uu.nl/opnames/van-kern-tot-kosmos/van-kern-tot-kosmos-de-wereld-volgens-natuurkunde-en-filosofie">http://www.sg.uu.nl/opnames/van-kern-tot-kosmos/van-kern-tot-kosmos-de-wereld-volgens-natuurkunde-en-filosofie</a> (start around 2:10:00) <br />
<br />
My translated, approximate transcription is below. Any errors due to interpretation and translation are my responsibility. Topics are: <br />
<ul>
<li>The increasing abstraction and generality of physical theories. </li>
<li>The disappearance of classical explanatory categories like space and time from theories (like in Verlinde's novel gravitational theory: <a href="http://en.wikipedia.org/wiki/Entropic_gravity">http://en.wikipedia.org/wiki/Entropic_gravity</a>). </li>
<li>The increase of the number of theories that explain observations equally well (like the different interpretations of quantum mechanics). </li>
</ul>
<ul></ul>
<div style="text-align: center;">
<b>--- </b></div>
<br />
<div style="text-align: center;">
<b>“The unreasonable success of physics” - Dennis Dieks</b></div>
<br />
Let me start with a kind of hymn to physics: physics has offered many impressive results. Some decades ago physicist and Nobel prize winner Eugene Wigner wrote a famous paper "The unreasonable success of mathematics in the natural sciences." Of course it is miraculous that mathematics thought up somewhere in a garret is applicable in physics. Like the differential geometry utilized in Einstein's theory which stemmed from several decades before that theory. However, I am not much impressed by this argument. Lots of mathematics appears from garrets. Nevertheless, only a small part of it is used in physics. It would be interesting to conduct research to find out if the “unreasonable success”is really as miraculous as often assumed.<br />
<br />
For me the real miracle is that physics is so successful. That there are regularities such that things proceed as expected. That buildings stay exactly in place, and that I am able to trace back a pair of spectacles I lost. The predictions are very accurate, to many decimal places. Much of modern physics – like Erik Verlinde's new gravitational theory - deals with only some last decimal places. Hence the discussion about a theory of everything is in some sense a non-discussion, because we already have such a theory for all ordinary applications of physics in biology, psychology, chemistry, etc. The new developments - strings, super gravitation - will make practically no difference for this type of applications. Discussions about existing applications can all be had on the basis of existing physics. Modern physics is a matter of steadily adding digits after the decimal place. In this sense the growth of physics is completely cumulative. The accuracy of our predictions steadily grows. I agree with former speaker Fred Muller: with regard to structure new theories are extensions of older ones. This is a cumulative process. During this steady accumulation revolutions take place. For example, the character of space and time in Newton's theory is completely different from that in the one of Einstein. The same holds for mass. For Newton it is the property of a particle, of a physical system. In relativity it is completely different, because here mass depends on speed. The character of mass has changed. In a certain sense we live since relativity theory in a different world than before. That is what I call a revolutionary transition. At the same time there is a cumulative growth of structures. How can these two things be reconciled? Below some more about this. <br />
<br />
First some more examples of revolutionary changes. In classical physics objects are localized. Space and time are very important as a kind of stage on which matters take place. From a philosophical viewpoint space is a principle of individuation: points act to discern things. Objects at different positions are different. On the contrary, in quantum mechanics particles do not have exact positions and velocities. This is a revolutionary change. Words (like "particle") do not change. Notwithstanding, if one looks more closely, they refer to different objects. At the same time certain relations keep unchanged in different theories. One will understand that if the objects change, the relations have to become more abstract. They have to cover more, because each theory includes the preceding one and the character of things changes continuously. The structures – the end products of the cumulative development - become more general and in some sense also more meaningless. More vague, because they have to include more. More possible realities should fit in.<br />
<br />
Elements disappearing more and more from these increasingly vague structures are space and time themselves. I do a prediction about a tipping point: in the newest theories space and time will lose the function they always had. Quantum mechanics itself already suggests this. Therefore we do not need a new theory as that of Verlinde to see this, in which space and time are emergent properties. A suggestive example from quantum mechanics is teleportation. According to Einstein, Podolsky and Rosen (and Bohm later on) it is possible to have a non-localised state. Think of a particle here and one far away. So they have very different positions, but can simultaneously share certain properties. The total spin can be defined (it is 0), however it cannot be reduced to those of the individual particles. For example to the sum of the individual spins. There is something holistic about the system, so to speak. This immediately suggests it can be utilised to send signals. When one determines the spin of particle A, than one knows for sure the spin of B. It turns out that this cannot be utilised straightforwardly. One cannot transmit signals at a speed exceeding that of light. So it appears as if the classical space and time ideals can simply be maintained. Nevertheless there is something strange going on. This is what we call teleportation and comes to light if one inspects the situation more closely. [ what follows is an explanation of the mechanism of quantum teleportation of which a translation does not make much sense. See <a href="http://en.wikipedia.org/wiki/Quantum_teleportation">http://en.wikipedia.org/wiki/Quantum_teleportation</a> in stead ] It is possible with the help of the transmission of 2 classical bits (for example through a telephone line) to teleport the state of particle A to particle B. This is strange from a classical viewpoint, because the state contains much more information than 2 bits, which can be characterised by a real number between 0 and 1. Space and time apparently function as a stage on which everything happens and on which things propagate. However, when one takes a closer look at it one notices that teleportation cannot be done through the ordinary propagation of signals. It is as if the information goes through a back door from A to B – not through space and time. A signal is needed but it is not the signal itself that transmits the information. Hence from quantum mechanical computations processes follow that can not be interpreted as processes that propagate in space and time. Therefore I think that quantum mechanics already hints towards the idea that space and time are a kind of emergent phenomena. I think that quantum mechanical computations (in Hilbert space, for the informed) are more fundamental than what we can understand in terms of space and time.<br />
<br />
We can expand on this. There are indications that we can regard gravitation as a kind of statistical phenomenon emerging from a much deeper, microscopic level. However, the aforementioned phenomenon that one needs to be increasingly general now takes revenge. This is because one has to incorporate all previous views in the new view. The new view contains hardly information of the kind one likes to have. That's apparent from Verlinde's model. It is based on information, not on particles or other physical systems. However, what is information really? Is talking about information not a kind of second choice because one does not know exactly what it is all about? 0-s and 1-s are only ways to represent information. Information is always information about something. An advantage of Verlinde's theory is that this is not important any more. One is no longer interested in what type of fundamental process underlies gravitation. It is sufficient to assume there is such a process to which statistical mechanics can be applied. This is exactly a theory that is helpful as soon as one does not know what is going on exactly. So on the one hand Verlinde's theory is a giant leap forward, but at the same time it is a kind of failing to admit that one cannot go beyond a certain border. That it is not very important what is going on beyond that border.<br />
<br />
We are on the verge of developments in which space and time lose their ordinary function and that we focus on deeper lying matters that are to a certain extent unimportant. So the former question what the information is about remains unanswered. This is an example of a general trend in physics. Classical explanatory concepts like causality, space and time and propagation of things disappear from sight. Abstraction increases and one cannot explain matters any more in ordinary ways. <br />
<br />
There is another thing that amplifies matters: the philosophical problem of theoretical underdetermination. In physics and in science in general one tries to formulate theories. Observation is an important input and theory should be in accordance with it. The more theories get separated from our daily lives – dig deeper, so to speak - the more they contain what cannot be observed. However, in theories is much more we cannot observe. As physics evolves this unobservable part grows. Compare this to a sphere. What can be observed is at the surface, the remainder lingers below it. If the radius increases the observable surface increases, however, the unobservable volume increases even faster. This brings the problem of underdetermination to light. It is the same as in mathematics in which one has to estimate a number of parameters on ground of only a limited amount of data. The equivalent physical problem is is that one has too few observations to fix all the parameters of a theory. A logical consequence is that many theories are possible based on exactly the same data. This is already happening in quantum mechanics. All those different interpretations that mostly correspond with respect to structure but sometimes differ a bit are all able to explain all known observations. They are empirically equivalent. Quantum mechanics is only an example of this phenomenon. Future physical theories will be more and more abstract, predict more accurately (higher accuracy), while at the same time being less uniquely determined. The theory of Verlinde is an example of this. One can image that one can have many different implementations of the underlying 0-s and 1-s which will make no difference for the structure above. <br />
<br />
A tipping point will thus be the disappearance, the fading of space and time in physical theories which will make no difference for our daily lives. After all we have to deal with left and right, etc. A second point is that theories will be less uniquely determined. There will be more discussion possible about what is the true character of reality. It is a kind of enormous advance which is accompanied by a slow slipping away of the means to gain knowledge about details.<br />
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<div style="text-align: center;">
<span style="font-size: x-small;"> Space-time stage.</span></div>
Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-1583763696701969482014-11-07T04:20:00.000-08:002014-11-07T04:20:10.573-08:00Not her dayYesterday I was waiting for the train, sitting on a bench on the platform, reading a news paper. Suddenly a female voice sounded: "Don't you think that God is the most important there is, Sir? That we should think a lot about Him?" I looked up and saw a slim bespectacled woman, dressed somewhat old fashioned in dark colours, with slightly worn out shoes. I was not into a religious discussion with her at that moment. Not knowing how to get around it I restored to straight reality: "I have a consultation with some Muslims tonight". Her voice turned a degree brighter: "Oh, you are also an evengalist, eh, doing evangalistic work?"<br />
<br />
Unexpectedly, she than walked to some nearby young males and started a conversation. After a few minutes one of them discovered that he had missed the train. <br />
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It was not her day.<br />
<br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-83127847688876783082014-11-02T11:30:00.000-08:002014-11-09T01:18:26.489-08:00Garden-variety mathematicsA mathematics teacher of mine once told with some pride about the first and last time he had used mathematics for a practical purpose. It concerned calculating the length of the rope he needed to tie his houseboat to the quay. For this he had used Pythagoras' theorem. His use of Pythagoras' theorem makes it part of what I call garden-variety mathematics: mathematics used for a practical purpose, at home for example. Let me expand garden-variety mathematics with two more examples.<br />
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A woman recently told me that she needed a ladder for rebuilding her house. She had to know the length of this ladder and calculated it with the 'sine' function. This was the first time this goniometric function was of practical use for her, outside the class room. Moreover, she discovered that she got the same answer with the 'cosine'!<br />
Hence, garden-variety mathematics minimally consists of Pythagoras' theorem and a part of trigonometry: the sine and cosine functions.<br />
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Now of course I cannot stay behind. So here you have it, the bookcase I developed myself:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEl1TkFuYS1I14fMe2-esz9HaKJsO-7vxlOiDbVaDWSMhnCU2aV3ByoOo3n34fpz5TKZ4gEQGKXWHSZslOWKM9MtVPh0nUBWvFR6rYx1PL2W_D9K4DEKczp7cDhg-cAEspnVbiCsA2WR8/s1600/Boekenkast.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEl1TkFuYS1I14fMe2-esz9HaKJsO-7vxlOiDbVaDWSMhnCU2aV3ByoOo3n34fpz5TKZ4gEQGKXWHSZslOWKM9MtVPh0nUBWvFR6rYx1PL2W_D9K4DEKczp7cDhg-cAEspnVbiCsA2WR8/s1600/Boekenkast.jpg" height="82" width="400" /></a></div>
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At first sight the division of shelves may seem a bit strange, therefore, let me explain the rationale behind it. First of all, I liked to store as many books in it as the total space could accommodate. As a consequence, there should for example not be many high compartments with only small pocket books in them. To solve this optimization problem I made a histogram of the height of my books. Discerning three sizes - small, medium, large - gave the following proportions:<br />
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<i>small:medium:large= 11:8:2</i></div>
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The proportions do not fix the compartment division exactly. The precise shape followed from demanding that it is robust and foremost: that it should please the eye. With respect to the latter, it pleases my eye because of the four overlapping stair cases each consisting of three ascending horizontal steps. What also adds to the beauty is the near mirror symmetry around horizontal and vertical lines through the centre. Less obvious is the exact 180 degree rotational symmetry around the centre. <br />
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Ok, with this contribution I expanded garden-variety mathematics to Pythagoras' theorem, some trigonometry, histograms and a bit of geometry. Who can add to this?<br />
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<span style="font-size: x-small;">This article is a translation of <a href="http://nietexact.blogspot.nl/2014/08/huis-tuin-en-keuken-wiskunde.html">http://nietexact.blogspot.nl/2014/08/huis-tuin-en-keuken-wiskunde.html</a> (August 17, 2014).</span>
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<br />Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-41587145917391580832014-10-28T12:08:00.000-07:002014-11-09T01:15:14.496-08:00Does gravel beat shadow?One of the funniest pictures I know:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6FHha4_mGWhAT8Ayc_BjHRPB70DAn6qryjqKuFrIeQyyZ8OqfX2HVinkkg2WTp_pjIBgX-sjxdqSVCOHlQFiEO5hs4g8b5JTfOtX5Hq-y-MLFGsSuscvpri7fZz2itYar2MhBoryXuQtG/s1600/DoesShadowBeatGravel_bijgesneden.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6FHha4_mGWhAT8Ayc_BjHRPB70DAn6qryjqKuFrIeQyyZ8OqfX2HVinkkg2WTp_pjIBgX-sjxdqSVCOHlQFiEO5hs4g8b5JTfOtX5Hq-y-MLFGsSuscvpri7fZz2itYar2MhBoryXuQtG/s1600/DoesShadowBeatGravel_bijgesneden.jpg" height="241" width="400" /></a></div>
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These children are puzzled by shadow: it does not disappear when they throw gravel on top of it. It reminds me of Jung, who used the term "shadow" for unconscious negative personal traits. The picture suggests that these are also hard to get rid of.<br />
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<span style="font-size: x-small;">Picture source: "The shadow club - the greatest mystery in the universe and the thinkers who unlocked its secrets", Roberto Casati.</span><br />
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<span style="font-size: x-small;">This article is a translation of <a href="http://nietexact.blogspot.nl/2014/10/winnen-steentjes-van-schaduw.html">http://nietexact.blogspot.nl/2014/10/winnen-steentjes-van-schaduw.html</a></span><span style="font-size: x-small;"> (October 28, 2014).</span>
Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0tag:blogger.com,1999:blog-4875065040601214115.post-594229438833706452014-10-28T11:52:00.002-07:002014-11-09T01:19:56.651-08:00Why exactly "Not exactly so"?What is the reason for the title "Not exactly so" of this blog? Coming up with a good title is not that simple. I followed a routine I sometimes use in buying a birthday present: first buy the present, than devise a fitting story. <br />
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"Not exactly so": because of my supposedly narrow background this blog will deal with subjects from the exact sciences. However... because of my broad interest many other subjects will be dealt with. The gist of my fitting story is this algorithm:<br />
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<b>IF</b> subject from within the exact sciences <b>THEN</b><br />
it will come clear that it has an inexact side to it<br />
<b>ELSE</b> % not an exact subject<br />
eh... then it is a subject from outside the exact sciences<br />
<b>END</b> % of blog-title-interpretation-algorithm<br />
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<span style="font-size: x-small;">This blog is the continuation of the blog nietexact.blogspot.com which is written in Dutch. Translated versions of my favourite articles that appeared there will appear here in due time.</span><br />
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<span style="font-size: x-small;">This article is a translation of <a href="http://nietexact.blogspot.nl/2014/08/waarom-precies-niet-exact.html">http://nietexact.blogspot.nl/2014/08/waarom-precies-niet-exact.html</a></span> <span style="font-size: x-small;">(August 5, 2014).</span>Joshttp://www.blogger.com/profile/14667361344937894839noreply@blogger.com0