Category: physics

The best free response answer of the year goes…

The best free response answer of the year goes to this kid

Regular

GOT ACCEPTED IN A DREAM PHD PROGRAM I can’t control myself

diaryofabrokegirl:

diaryofabrokegirl:

Phases

A note on triple and critical points

The Pressure – Temperature of a pure substance is commonly plotted as follows:

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When you take a look at such a graph, there are two points on it that are particularly fascinating. (rest are all boundaries) : The Triple and Critical point.

Most people might be familiar with a triple point. This is where the solid liquid
and gaseous phase are in equilibrium.

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 In the above animation, Gas phase is at the Top half of the container, Liquid at the bottom and Solid phase is sandwiched between the two phases.


If one keeps moving past the triple point and along the liquid vapor boundary line on the P-T diagram, one would notice that this boundary line terminates at a distinct temperature and pressure !!!

This point is known as a Critical point.

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Beyond this point distinct liquid and gas phases do not exist and the substance is known as a super-critical fluid.

In order to understand what that really means, watch the following didactic demonstration of a super-critical fluid transition: (It is absolutely beautiful)

One of the reasons why the critical point is crucial is that close of the critical point, small changes in pressure or temperature result in large changes in density. And industries love to take advantage of this to fine tune their processing methods.**

Have a good one!

* We have discussed the phase diagrams for only pure substances here. But phase diagrams for mixtures are interesting too. Check this out.

** Decaffeinating coffee + Video demonstration of decaffeinating using Supercritical CO2  

What can science tell us about history repeating itself?

Poincaré Recurrence theorem

The Poincaré recurrence theorem states that certain finite systems
will, after a sufficiently long but finite time, return to a state very
close to the initial state.

The  Poincaré recurrence time tells you how long one should wait for the recurrence to occur.

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Now if we churn out the numbers for the universe, the Poincaré recurrence time comes out too be this special number:

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If we abstract ourselves from the possibility of experimentally testing it out, the key takeaway from this is that the Poincaré recurrence time is a finite number and one does not need to wait forever to observe the recurrence of events in the universe.

Therefore in Physics it does not make any physical sense to talk beyond this time scale.

Great question! Thanks for asking!

May 11,2018  – Richard Feynman’s 100th BirthdayRemembering a…

May 11,2018  – Richard Feynman’s 100th Birthday

Remembering a man whose passion for understanding the laws of nature was seeded in every milestone of his life- Richard.P.Feynman. 

Though it has been more than 30 years since he has passed away, the
legacy that he left as  both a brilliant physicist and a masterful
storyteller and teacher continues to live on forever.

* Feynman playing the bongos

Introducing FYP’s book club

We are starting a new segment on the blog where we recommend one or two books in Math or Physics that everyone can read.

And this month it is : A Mathematician’s Apology by G.H.Hardy which is available for free to download here and here

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You are absolutely welcome to share your comments and reviews here once you are done. Also, if you would like us to check a book out, do let us know too!

Have a good one!

How Does Our Earliest Picture Of The Universe …

How Does Our Earliest Picture Of The Universe Show Us Dark Matter?

“So all you need to do, to know whether your Universe has dark matter or not, is to measure these temperature fluctuations that appear in the CMB! The relative heights, locations, and numbers of the peaks that you see are caused by the relative abundances of dark matter, normal matter, and dark energy, as well as the expansion rate of the Universe. Quite importantly, if there is no dark matter, you only see half as many total peaks! When we compare the theoretical models with the observations, there’s an extremely compelling match to a Universe with dark matter, effectively ruling out a Universe without it.”

If your young Universe is full of matter and radiation, what happens? Gravitation works to pull matter into the overdense regions, but that means that the radiation pressure must rise in those regions, too, and that pushes back against the matter. On small scales, this pushback washes out the gravitational growth, but on large-enough scales, the finite speed that light can travel means that no wash-out can happen. Dark matter, however, doesn’t collide with radiation or normal matter, while normal matter collides with both radiation and itself. If we can calculate exactly how these three species interplay, we can calculate what types of patterns we expect to see in the Big Bang’s leftover glow, and then compare it with what we observe with satellites like WMAP and Planck. And what have we seen, exactly, when we’ve done that? 

We see that the Universe must contain dark matter to explain the observations. No alternative theory can match it.

Forget WIMPs, Axions And MACHOs: Could WIMPzil…

Forget WIMPs, Axions And MACHOs: Could WIMPzillas Solve The Dark Matter Problem?

“But what, exactly, is dark matter? And, moreover, can we be certain it exists? There are a huge suite of detectors and experiments out there searching for it, and yet no robust, verified, direct detection has ever been reported. There is no smoking gun we can point to and say, “this was an event caused by an interaction with dark matter.” The overwhelming majority of detectors out there are looking for WIMP-type dark matter, with a small contingent also looking for axions. (MACHOs, or other sources of “normal” dark matter, have been ruled out.) But all of this may be misguided. Dark matter might not be any of those things we’re looking for. In fact, it’s arguable that the candidate with the best motivations for it have no experiments to their name at all: WIMPzillas!”

Many detractors of dark matter point to the fact that we haven’t directly detected it yet as evidence that dark matter doesn’t exist. Yet practically every dark matter search that’s ever been performed has focused on just one particular class of dark matter: WIMPs. Well, WIMPs have been constrained very tightly, and we’re no closer to seeing WIMP dark matter than we were decades ago. But in that same time span, we’ve seen a number of exciting discoveries, including neutrino masses, come to fruition. Related to neutrino masses is the idea that there would be super-heavy right-handed neutrino counterparts to the light ones we see today. Could these “WIMPzillas” be the dark matter we’ve been looking for?

The theoretical motivation is compelling, and yet there are no detection experiments looking for one. Perhaps we need to fix that!

fuckyeahphysica: Diamagnetic Levitation -Ig Nobel prize…

fuckyeahphysica:

Diamagnetic Levitation -Ig Nobel prize (2000)

In the previous post we took a look at how combinatorics and paramagnetism gel together. In today’s post we will talk about levitating frogs and diamagnetism.

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                                         Diamagnetic material

A diamagnetic material is one which would rather ‘die’ than be attracted to a magnetic field (it opposes the magnetic field).

Paramagnetic materials on the other hand are those which love to align themselves paralled to the magnetic field.

The opposition of this magnetic field sets up a restoring force that pushes it away from the field. For example take a look at this diamagnetic tomato which is being a baby about a strong magnetic field and keeps moving away.

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                                       PC: University of Hull

Why does the frog levitate?

Frogs and most living creatures on earth contain high concentrations of water and water is a weakly diamagnetic material.

Here is the diamagnetic levitation of a tomato which, as you know is flush with water:

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                      Gif source credit:  Radboud Universigy

In order to accomplish this a very large electric current is made to pass through a ‘bitter electromagnet’.

This generates a high magnetic field around the frog. The frog being diamagnetic opposes this field generating a opposing force.

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             PC: mriquestions

Now since the frog is light in weight, the diamagnetic force generated is sufficient to overcome the effects of gravity enabling the frog to levitate.

Can Humans be levitated like this ?

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Well, for levitating a frog that weighed around 25 gms one had to use a 15 Tesla coil. A typical MRI machine uses only a 3 Tesla coil and this took 5 times that.

The magnetic fields required to levitate a human is too crazy to be achieved at the moment but as research in superconductors advances maybe we will be able to get to a high enough magnetic field to at the least test it out.

Have a great day!

Sources:

From levitating frogs to a nobel prize

Much more detailed explanation on the levitating frog

** BONUS: A follower of this blog pointed us to this video by The Action Lab who performed this crazy demonstration using a large Neodymium Magnet and a mouse.

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It should be of no surprise to you that this works since most living creatures on earth contain high concentrations of water and water is a weakly diamagnetic material.

Have a great day!