tag:blogger.com,1999:blog-40508268093936473542024-03-06T01:07:56.642+00:00The pondering of Kieran MacRaeIn this Blog I hope to offer discussions of various aspects of science in hope of increasing others understanding as well as my ownAnonymoushttp://www.blogger.com/profile/00451428961688975218noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-4050826809393647354.post-50292019876048984502014-03-07T14:06:00.000+00:002014-03-07T15:48:03.747+00:00Night Over Day Over Night, Examining Our Perception of Time<div style="text-align: center;">
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<span style="font-family: Arial, sans-serif;">I love
time. I like wearing my watch, keeping track of where my day is going
and I absolutely hate being late. Time is governed mainly by the
passing of days and nights: we work through the day and sleep at
night. This is the periodicity we all live by. But what if you tried
to break this cycle? What is you decided how long your day would be?
In 1974, in the small town of Los Almos, New Mexico, a man named Dr.
Mitchell Feigenbaum – a mathematical physicist who helped pioneer
chaos theory (a post on this is soon to come) – decided that a
24-hour day simply wasn't long enough.</span></div>
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<span style="font-family: Arial, sans-serif;">If this
thought occurred to a normal person, they would probably decide just
to go to bed earlier. You wake up earlier the next morning and are
able to seize the day. But Dr. Feigenbaum decided to increase the
length of his normal day to 26 hours, instead of the usual 24. It was
quite a task to take on. It would mean falling out of sync with the
passing of day and night. It would mean rejecting everything your
body considers natural, and face being awake in the dark, many hours
before the sun came up. In the end it became too much for Dr.
Feigenbaum and he gave up. There's only so much of waking up to the
sun going down that a man can take. [1]</span></div>
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<span style="font-family: Arial, sans-serif;">To me,
this attempt seems a little like trying to cheat time. If you were to
stick to this regime, for every 12 days that passed, you would be one
day behind the rest of the world. This cycle would repeat, as every
day you would be two hours behind everyone else. For you, 12 days
have passed. For the rest of the world, 13 days have passed. This
might seem like a victory. After all, you've gained more time,
haven't you? This regime will make it feel as if you're getting more
done because less time has passed in terms of days and weeks, but
really you're experiencing what everyone else is, just in a different
order. Nothing has changed. Time still passes, your existence has
just fallen out of sync with those around you. Your body will still
age at the same rate. You will still die. You just might consider
yourself a lot younger than others might.</span></div>
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<span style="font-family: Arial, sans-serif;">But what
if you isolate yourself away from natural light, any form of clock or
timekeeping equipment and society as a whole? In 1962, Michel Siffre,
a French speleologist – a person who studies caves – lived in an
underground cave in complete isolation. His only communication was by
shouting to a team at the mouth of the cave, which he did when he
woke up and went to sleep, so that they could record it. The team
weren't allowed to call back to him or give him any indication as to
what time it was outside. Siffre had a number of his own experiments
to conduct while underground but the main investigation was into the
human body's internal clock and how it perceives time when stripped
of all its gauges. At the end of the experiment, it was found that
Siffre's body clock changed only slightly: his day had become 24 and
half hours long. Siffre went on to conduct a number of follow-up
experiments, which included having others in isolation with him and
the results from these show that the group's body clocks were running
on 48-hour cycles. The group would be awake and functioning for up to
36 hours and then sleep for 12-14 hours before repeating. [<a href="http://www.cabinetmagazine.org/issues/30/foer.php">2</a>]</span></div>
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<span style="font-family: Arial, sans-serif;">The
results from this experiment are remarkable. Without the sun to aid
us, our bodies can experience twice the number of hours of
wakefulness, followed by twice the number of hours of sleep. If the
same experiment was carried out on the earth's surface, the
participants would be absolutely exhausted, largely because they
would be able to tell when it was night and when they believed they
should be sleeping. Time as we know it as the passing of day into
night and the belief that this controls our actions is an illusion.</span></div>
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<span style="color: black;"><span style="font-family: Arial, sans-serif;">We
do need sleep, but not the way you think. We rest at night because of
psychological reasons. For example, it's a lot easier to carry out
tasks when it's bright outside. However, before the invention of
street lights or light bulbs, our prehistoric counterparts had to go
out and hunt during the day when the sun was out in order to survive.
Food could be cooked at night by the fire, they could rest their
bodies while they slept and then the process would repeat. It's this
history that affects the way we think today. If our ancestors hadn't
slept at night, would we still do so now? </span></span>
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<span style="color: black;"><span style="font-family: Arial, sans-serif;">These
are just some of the aspects of time that might not have been known, and a few experiments I wanted to share with you. I hope you now have
a different view on time and our passing through it. I hope you think about these things next time it's late and your feeling tired and ask yourself if you really are tired or is it just that its late?</span></span></div>
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<span style="color: black;"><span style="font-family: Arial, sans-serif;">[1]
James Gleick, Chaos, 1998</span></span></div>
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<span style="color: black;"><span style="font-family: Arial, sans-serif;"><span style="font-size: small;"><i>I
hope you enjoyed this post on some of the stranger aspects of our
existence in time. If there is anything you felt was incorrect in
this post, please let me know as I'm always keen to improve. If you
have any questions you want to ask please do and I'll do my best to
answer. Thanks for taking the time to read this and please look out
for my next post which will be talking about the effects of time
dilation and Einstein’s special relativity.</i></span></span></span></div>
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Anonymoushttp://www.blogger.com/profile/00451428961688975218noreply@blogger.com2tag:blogger.com,1999:blog-4050826809393647354.post-77776394637560053222014-03-01T14:17:00.003+00:002014-03-01T14:19:13.269+00:00My Week in the World of Physics<div style="text-align: left;">
<b style="font-family: Arial, Helvetica, sans-serif; font-size: x-large;">This week in my life as a physics student</b></div>
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<span style="font-family: Arial, Helvetica, sans-serif; text-align: left;">I am a third year physics student studying at Strathclyde university and this week has been a really good week and I just wanted to share this with all of you who may end up reading this.</span><br />
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<span style="font-family: Arial, Helvetica, sans-serif; text-align: left;">I have been organising taking part in an internship with the university during this summer coming, and this week I finally got all my applications sent off! It is even more exciting because the internship is going to be in conjunction with the Beatson Cancer Research institution so I will be working along side the leading experts in cancer research to try and help advance the imaging techniques used in analyzing cancer cells. I applied to a number of funding bodies one of which is the Carnegie Undergraduate Vacation Scholarship. </span><br />
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<span style="font-family: Arial, Helvetica, sans-serif; text-align: left;">This is a highly prestigious award that is very competitive and each applicant gets an academic grading based on there past exam marks and I was lucky enough to receive</span><span style="font-family: Arial, Helvetica, sans-serif; text-align: left;"> the highest grading. outstanding excellence, an A. I also sent of the application to the dean of science because i was under the impression he had to give the academic grading which turned out to be incorrect but he told me that the project looked very interesting. This doesn't seem like much of a statement, but to hear that from the dean of science made me feel like I have a much better chance at getting awarded the bursary. So now I just have to wait several months before hearing back so my fingers are crossed!</span></div>
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<span style="text-align: left;"><span style="font-family: Arial, Helvetica, sans-serif;">This blog was started this week as a way of getting some feed back on an assignment I had due that involved discussing how to explain entropy to a group of high school students. The post was very well received and I got excellent feed back from several different people and got it handed in in plenty of time. If you like you can <a href="http://macrae94.blogspot.co.uk/2014/02/entropy-full-yet-simple-definition.html">read that post here</a>. This was really great I had no idea so many people would enjoy reading it, so thank you to the people that did.</span></span></div>
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<span style="font-family: Arial, Helvetica, sans-serif;">As part of my course I have weekly lab sessions that involve four hours in the lab twice a week. I always enjoyed labs as I love getting to preform experiments. One of the experiments I got to do was the Millikan oil drop, which is a famous physics experiment that determined the charge of an electron and showed that it is quantised, so I never had a problem with this class but this week I finished my final experiment and have finished my labs 4 weeks early. This means that my weekly contact time in uni is only a meager 10 hours which is very exciting. I will need to spend this time doing revision and other assignments but on the whole I've still gained 8 hours a week to fill with whatever I want.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif;">So it's been a good week and hopefully I will have many more good weeks to come when the decisions about the bursaries come through.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif;">On a final note I have been reading an Astronauts Guide to Life on Earth by Chris Hadfield. It has been a really inspiring read about one mans journey through life in the build up to becoming an astronaut, it is a real insight into what it really takes to do the job that all children want to do and then to hear the details of what being in space and working on the international space station is really like. Its been fantastic and I would highly recommend it to everyone.</span></div>
Anonymoushttp://www.blogger.com/profile/00451428961688975218noreply@blogger.com0tag:blogger.com,1999:blog-4050826809393647354.post-30314182989986995752014-02-23T13:29:00.000+00:002014-03-01T14:18:47.624+00:00Entropy a full, yet simple definition.<span style="font-family: Arial, Helvetica, sans-serif;">I am a third year physics student and have been given an assignment as part of my statistical physics call to discuss how I would explain entropy to a class of senior high school students in order to show my understanding it. This is what I have come up with and would appreciate any feed back and especially highlighting anything I got wrong.</span><br />
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: 16pt;"><b>Entropy</b></span></div>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">First
I would define Entropy in the most succinct way “Energy depends to
disperse”. So everything from a candle being lit that disperses
heat energy out from the flame, to a rock being dropped into a pool
of water and the energy going out in the form of the ripples and
splashes.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">Heat
energy dispersing then leads on to the heat death of the universe.
This is a suggested ultimate fate of the universe, in which all the
heat from all the stars and other processes will have dispersed all
there energy so that the universe is left in a thermal equilibrium.
If this were to happen then there would be no energy left to produce
work and so no more processes would be able to occur and the universe
would more or less than come to a stop. The name “Heat Death”
implies extraordinarily high temperatures however this is not the
case is all the heat energy were to disperse it would result in a
very low temperature due to the sheer size of the universe and the
finite amount of heat energy being spread over it.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">I
would then say that there is more to entropy than that and that it
involves several different definitions of different processes
involved in thermodynamics, starting with the zeroth law of
thermodynamic. The zeroth law is a very simple and somewhat obvious
statement, it states “If two systems are in thermal equilibrium
with a third system, then they must be in thermal equilibrium with
each other”. In other words systems are in thermal equilibrium when
they all have equal temperatures.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">From
this I would lead onto the first law of thermodynamics. The first law
is simply a statement of the conservation of energy “(Change in U)
= (Change in Q) + (Change in W)” where U is the internal energy, Q
is the heat energy and W is the work done. This is why the “Heat
Death” would occur as since there would be constant heat energy Q,
there can subsequently be no change in the Work done W. It is
important to note the Q and W are functions of state. This means that
they do not depend on the history of how they got to that state. So,
they can travel by any path and the path they took does not influence
the final value.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif;"><span style="font-size: small;">Now
the next most important system to consider is reversible and non
reversible processes. A reversible process is one that can be undone
without resulting in any change to the system or its surroundings,
now this is unfortunately not possible and is an idealized process as
for instance you cant un-bake a cake, or un-pop a balloon. But even
on a much smaller level, if you wheel your chair across a room a
breeze is created and when you wheel it back another breeze is
created. the previous breeze is not sucked back towards the chair.
However, in general the main thing that cannot be undone is the
entropy of the system because as we will find out. Because in nature,
entropy always increases. </span>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">Take
for instance the graph shown in figure 1 , if the process was
reversible then the area under the graph would be zero and so nothing
would change, However, since there are no reversible processes the
path back to the starting point will be not be equal to zero and so
will result in some amount of work done. But, if this happens the
change in internal energy will be zero as it has returned back to the
starting point so if you look at the first law of thermodynamics this
implies that the heat energy is equal to the negative of the work
done. In other words, heat in = work out, and work in = heat out.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">Figure
1. Area under the graph of pressure against volume is the work done.
In more mathematical terms dW = -p dV where p is the pressure and dV
is the change in volume.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">I
would then go on to talk about the Carnot cycle. The Carnot cycle is
a very important process that describes and idealised heat engine,
one which in reality is not achievable but is important in the
fundamental understanding of thermodynamics. It is best explain with
use of a diagram shown in figure 2.</span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkUoXlHi4F-KOtMpPBL-H1kC-lRRpE8qT_xHdNza_Yh0egH8wp5DSDRka7lMfHSA4SI2I-cViEEMRDSONcE7A2YD75sgYoCIsEuzbCEb9wY-NTy4STQXfiwA888FGe56w1yvf1zJfdh2PB/s1600/Untitled.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="font-family: Arial, Helvetica, sans-serif;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkUoXlHi4F-KOtMpPBL-H1kC-lRRpE8qT_xHdNza_Yh0egH8wp5DSDRka7lMfHSA4SI2I-cViEEMRDSONcE7A2YD75sgYoCIsEuzbCEb9wY-NTy4STQXfiwA888FGe56w1yvf1zJfdh2PB/s1600/Untitled.png" height="274" width="320" /></span></a></div>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">Figure
2. Diagram of the Carnot cycle which runs from point A-B, B-C and so
on back to point A.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif;"><span style="font-size: small;">From
figure 2 it should be said that the green lines pointing up and down
are adiabatic processes which is a process that occurs without loss
or gain of heat, and the lines marked T1 and T2 are isothermal which
simply means they occur at constant temperatures. This is a process
that uses an ideal gas which again is not attainable in reality but
helps to define what is happening. So the gas is expanded from A-B
and B-C and then compressed from C-D and D-A taking it back to its
original point. Q1 is the heat into the system at a higher
temperature and Q2 is the heat going out of the system at a lower
temperature. </span>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">From
this the thermal efficiency can be calculated by dividing the work
out by the heat energy in and it is found that this must be less than
one due to Clausius's statement which we shall come back to later.
This shows that no system, apart from an idealized one, can be 100%
efficient. This is important to know apart from the implications in
to creating efficient engines and such in real life but it also
implies that no matter what you do energy will be lost. In a sense,
entropy is the measure of the amount of energy that is not available
to be converted to work in the system. E.g. how much energy is lost
and this, is the second law of thermodynamics.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">I
would then go on to explain more details of the second law. The
second law of thermodynamics can be quite hard to define and
understand conceptually. There are two statements of the second law
of thermodynamics that are vital in our understanding of it. The
first is Clausius's statement which is “No process is possible
where the sole result is the transfer of heat from a colder to a
hotter body.”. The second is Kelvins statement which is “No
process is possible whose sole result is the complete conversion of
heat into work” and this relates back to what was defined with the
Carnot cycle.</span></div>
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<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">These
two statements are of paramount importance even though they do seem
somewhat obvious it is important to consider that if they did not
explicitly define these facts then they would be up for
interpretation and could have changed the way many systems were
considered and not for the better.</span></div>
<div align="LEFT" style="margin-bottom: 0cm;">
<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">Together
they can be used to disprove any other form of engine apart from the
one which we know and use today in which heat goes into the engine,
work is put out but there is also an exhaust to vent any excess heat.</span></div>
<div align="LEFT" style="margin-bottom: 0cm;">
<span style="font-family: Arial, Helvetica, sans-serif;"><br />
</span></div>
<div align="LEFT" style="margin-bottom: 0cm;">
<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">Mathematically
entropy, S, can be defined as dS = dQrev/T where dS is the change in
entropy, dQrev is the change in heat energy in an reversible system,
and T is the temperature. This results in the unit of entropy being
J/K or Joules per Kelvin which makes sense when entropy is the
measure of energy lost of a system at a given temperature.</span></div>
<div align="LEFT" style="margin-bottom: 0cm;">
<span style="font-family: Arial, Helvetica, sans-serif;"><br />
</span></div>
<div align="LEFT" style="margin-bottom: 0cm;">
<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">Finally
we must look at the fundamental equation of thermodynamics. First
remember the 1<sup>st</sup> law of thermodynamics: dU=dQ+dW, and we
also now that dW = -pdV and finally we know that the entropy change
of a reversible process is: dS = dQrev/T. If we put all these
equations together we get the final equation:</span></div>
<div align="LEFT" style="margin-bottom: 0cm;">
<span style="font-family: Arial, Helvetica, sans-serif;"><br />
</span></div>
<div align="LEFT" style="margin-bottom: 0cm;">
<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">dU=TdS-pdV in a reversible process.</span></div>
<div align="LEFT" style="margin-bottom: 0cm;">
<span style="font-family: Arial, Helvetica, sans-serif;"><br />
</span></div>
<br />
<div align="LEFT" style="margin-bottom: 0cm;">
<span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">But,
it should be noted that all these terms are functions of state and so
do not depend on the path they took which means that this equation
must also hold true for irreversible processes. This is the
fundamental or central equation of thermodynamics as it allows
entropy to be meausred as a physical value of all systems.</span></div>
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