Wednesday, July 18, 2018

Multiverse

In this article, Ethan Siegel valiantly tried to explain, in simple language, what "multiverse" is within the astrophysical/cosmological context:

Inflation doesn't end everywhere at once, but rather in select, disconnected locations at any given time, while the space between those locations continues to inflate. There should be multiple, enormous regions of space where inflation ends and a hot Big Bang begins, but they can never encounter one another, as they're separated by regions of inflating space. Wherever inflation begins, it is all but guaranteed to continue for an eternity, at least in places.

Where inflation ends for us, we get a hot Big Bang. The part of the Universe we observe is just one part of this region where inflation ended, with more unobservable Universe beyond that. But there are countlessly many regions, all disconnected from one another, with the same exact story.

Unfortunately, as is the problem with String theory, none of these have testable prediction that can push it out of the realm of speculation and into being a true science.

Zz.

Tuesday, July 17, 2018

94 Aluminum Pie Pans On A Van de Graaf

What happens when you put 94 aluminum pie pans on a Van de Graaf? Sometime you do things just because it is darn fun!



Now let's see if you can offer your own explanation for this silly thing! :) Happy 10th Anniversary on YouTube, Frostbite Theater!

Zz.

Monday, July 16, 2018

Neutrinos Come Knocking For Astronomy

I feel as if these are the golden years for astronomy and astrophysics.

First there was the discovery of gravitational waves. Then a major astronomical event occurred, and we were able to detect it using the "old" standard technique via EM radiation, and via the detection of gravitational waves from it. So now astronomy has two different types of "messengers" to tell us about such events.

Well now, make way for a third messenger, and that is ubiquitous neutrinos. Two papers published in Science last week detected neutrinos (along with the accompanying EM radiation) from a "blazer". The neutrino detection part was made predominantly at IceCube detector located in the Antarctica.

Both papers are available as open access here and here. A summary of this discovery can be found at PhysicsWorld (may require free registration).

Zz.

Friday, July 13, 2018

The Most Significant Genius

No, not Einstein, or Feynman, or Newton. Fermilab's Don Lincoln celebrates the hugely-important contribution of Emmy Noether.



I have highlighted this genius previously, especially in connection to her insight relating symmetry to conservation laws (read here, here, and here).

Zz.

Wednesday, July 11, 2018

First Human Scanned By Spectral X-Ray Scanner

Chalk this up to an application of high-energy physics in the medical diagnostic field. The first human has been scanned by a new type of x-ray scanner (registration required to read article at this moment).

The MARS scanner uses Medipix3 technology developed at CERN to produce multi-energy images with high spatial resolution and low noise. Medipix is a family of read-out chips originally developed for the Large Hadron Collider and modified for medical applications.

The Medipix3 detector measures the energy of each X-ray photon as it is detected. This spectral information is used to produce 3D images that show the individual constituents of the imaged tissue, providing significantly improved diagnostic information.

I'll repeat this, maybe to those not in the choir, that many of the esoteric experiments that you think have no relevance to your everyday lives, may turn out to be the ones that might save your lives, or the lives of your loved ones, down the road. So think about this when you talk to your elected political representatives when it comes to funding basic science.

Zz.

Thursday, July 05, 2018

Einstein Is Right Again!

... or rather, General Relativity passed another test.

This is on the heels of the first ever verification of GR at the galactic scale. This time it is a test of GR's strong equivalence principle involving a neutron star and two white dwarfs (no, not the kind from that Snow White movie).[1]

Archibald and colleagues’ study breaks new ground because the gravitational energy inside a neutron star can account for as much as 20% of the body’s mass. The authors’ results therefore imply that the accelerations of gravitational energy and matter differ by no more than a few parts per 105 — a tenfold improvement over the bound from lunar laser ranging.

More importantly, the authors have provided what is known as a strong-field test of general relativity. Unlike the Solar System, for which Einstein’s theory predicts only small deviations from Newton’s theory of gravity, the motion of a neutron star in a gravitational field invokes full general relativity in all its complex glory. Einstein’s theory passes this strong-field test with flying colours.

The more they test it, the more convincing it becomes.

Zz.

[1] A.M. Archibald et al., Nature, 559p73 (2018).

Tuesday, July 03, 2018

What Type of Physicist Are You?

... leader, successor, or toiler?

A new bibliometric study has found that authors can be roughly grouped into three categories: lead scientists who are already prominent in their fields, successors who are early career scientists, and toilers, which are those who do a lot of the dirty work but aren't going anywhere.

When looking at the citation data for mathematicians, psychologists and physicists, the authors identified three broad clusters that are “loosely based” on how the citations per year changes over time. Leaders tend to be experienced scientists who are widely recognized in their fields, which results in an annual citation increase. The successors tend to be early-career scientists who have had a surge in their citations in recent years. Toilers, meanwhile, may have a high citation count, but this stays mostly constant and may even drop slightly.

Not sure of the significance of this study, but hey, it's another criteria to classify people!

Zz.

Saturday, June 23, 2018

Super Kamiokande and Extremly Pure Water

This is a rather nice overview of Super Kamiokande, a neutrino detector in Japan. It has produced numerous ground-breaking discoveries, including the confirmation of neutrino oscillation many years ago. Unfortunately, the article omitted an important incident at Super-K several years ago when there was a massive implosion of the phototubes.

The article has an interesting information that many people might not know about extremely pure water, the type that is used to fill up the detector tank.

In order for the light from these shockwaves to reach the sensors, the water has to be cleaner than you can possibly imagine. Super-K is constantly filtering and re-purifying it, and even blasts it with UV light to kill off any bacteria.

Which actually makes it pretty creepy.

"Water that's ultra-pure is waiting to dissolve stuff into it," said Dr Uchida. "Pure water is very, very nasty stuff. It has the features of an acid and an alkaline."
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Another tale comes from Dr Wascko, who heard that in 2000 when the tank had been fully drained, researchers found the outline of a wrench at the bottom of it. "Apparently somebody had left a wrench there when they filled it in 1995," he said. "When they drained it in 2000 the wrench had dissolved." 

In other words, such pure, deionized water is not something that you want to drink.

And this leads me to comment on this silly commercial of PUR drinking water filter. It showed an ignorant public complaining about lead in the drinking water, even though he was told that the amount is below the safety level.



A drinking water contains a lot of other dissolved minerals, any one of which, above a certain limit, can be dangerous. Even that PUR commercial can only claim that it can REDUCE the amount of lead in the drinking water, not completely removed it. It will not be zero. So that guy should continue complaining about lead even with PUR filter.

If this person in the commercial is representing the general public, then the general public needs to be told that (i) you'll never be able to get rid completely of all contaminants in drinking water and (ii) pure water will dissolve your guts! This is why we set safety levels in many things (360 mrem of radiation per year, for example, is our acceptable, normal background radiation that we receive).

Zz.

Friday, June 22, 2018

General Relativity Passes Its First Galactic Test

Ethan Siegel is reporting the latest result of a test of General Relativity at the galactic scale.[1]

This effect of gravitational lensing, which occurs in both strong and weak variants, represents the greatest hope we have of testing General Relativity on scales larger than the Solar System. For the first time, a team of scientists led by Tom Collett performed a precise extragalactic test of General Relativity, and Einstein's theory passed with flying colors.

This new result also puts a strong damper on alternative theories of gravity, such as MOND.

For the first time, we've been able to perform a direct test of General Relativity outside of our Solar System and get solid, informative results. The ratio of the Newtonian potential to the curvature potential, which relativity demands be equal to one but where alternatives differ, confirms what General Relativity predicts. Large deviations from Einstein's gravity, therefore, cannot happen on scales smaller than a few thousand light years, or for masses the scale of an individual galaxy. If you want to explain the accelerated expansion of the Universe, you can't simply say you don't like dark energy and throw Einstein's gravity away. For the first time, if we want to modify Einstein's gravity on galactic-or-larger scales, we have an important constraint to reckon with.

This is definitely a big deal of a result.

Zz.

[1] T.E. Collett et al., Science v.360, p.1342 (2018).

Friday, June 15, 2018

Is Theoretical Physics Wasting Our Best Minds?

Before you continue reading this, let me be very clear right off the bat that there are TWO separate issues here that I will be discussing, and they are thinly connected simply by the over-general reference of "theoretical physics" made by the author of the article that I will be citing.

In this Forbes article, Ethan Siegel highlights the main point made by Sabine Hossenfelder in her book "Lost In Math". Siegel not only pointed this out, but also did an in-depth description leading up to the "naturalness" philosophy that is prevalent in the esoteric fields of physics such as string, etc.

If you are a theoretical particle physicist, a string theorist, or a phenomenologist — particularly if you suffer from cognitive dissonance — you will not like this book. If you are a true believer in naturalness as the guiding light of theoretical physics, this book will irritate you tremendously. But if you're someone who isn't afraid to ask that big question of "are we doing it all wrong," the answer might be a big, uncomfortable "yes." Those of us who are intellectually honest physicists have been living with this discomfort for many decades now. In Sabine's book, Lost In Math, this discomfort is now made accessible to the rest of us.

Certainly this is thought-provoking, and it isn't something I disagree about. For science to give up on empirical evidence, and simply pursue something that looks "natural" or "beautiful" is dangerous and verging on being a religion. So my feelings are consistent with what has been said in the article.

Now comes the other part of the issue. It has always been my pet peeve when someone over-generalize physics as being predominantly being "high-energy physics, astrophysics, string theory, etc...", i.e. the esoteric fields of study. In this case, "theoretical physics" certainly is NOT dominated by those fields. There are theoretical studies in condensed matter physics, atomic/molecular physics, medical physics, accelerator physics, etc... etc., i.e. fields of studies that are certainly not esoteric, have lots of practical applications, etc.

In fact, I would argue that the esoteric fields of physics represents the MINORITY in terms of the number of practicing physicists that we have around the world. As a zeroth-order approximation of this claim, I decided to look at the members of the APS. The APS Divisions correspond to the number of members who declared themselves to be in a certain field within physics. Note that not all members made the declaration, and it is also not uncommon for a member to declare more than one division.


First of all, 79% of APS members are accounted for in this chart for the 2018 membership. Now, what is the percentage of members within the so-called esoteric fields of Astrophysics, Gravitation, and Particles and Fields? 14.9%. Even if you include Nuclear Physics into this, it will come up to 19.8%

Now, forget about theoretical or experimental. Can 19.8% represents ALL of physics? The fields of studies that a lot of people associate physics with are done by ONLY 19.8% of physicists! Using them, one will get a severely inaccurate representation of physics and physicists.

In fact, if you look at the fields more commonly associated with the physics of materials (condensed matter physics and Materials Physics), we get 18.2%, almost as big as Astrophysics, Gravitation, Particles and Fields, and Nuclear Physics combined! Condensed matter physics alone dwarfs other fields, being almost twice as big as the next division, which is Particles and Fields.

But what is more important here is that outside of the 19.8% of physicists in these esoteric fields, an overwhelming percentage of physicists (59.2%) are in fields of studies that are associated with practical applications of physics. So if you were to bump randomly into a physicist, chances are, you will find someone who works in a field related to something of practical importance and NOT a high-energy physicist, a nuclear physicist, etc.

This is my round-about way of complaining that Ethan Siegel article should not be a damnation of "theoretical physics" in general, because the overwhelming percentage of theoretical physics is NOT about these esoteric topics that have been mentioned in his article. Rather, theories in other parts of physics rely very heavily on empirical observations and verification, i.e. the good and tested way of doing science. In those areas, we are definitely NOT wasting our best minds!

A while back, I said that physics is not just the LHC. It is also your iPhone. Even that requires modification. We should say that physics is predominantly your iPhone, with only a smidgen of LHC added as garnishing. That is a more accurate representation of the field as a whole.

Zz.

Wednesday, June 13, 2018

MinutePhysics Special Relativity Chapter 6

If you missed Chapter 5 of this series, check it out here.

Here's Chapter 6 of the Minute Physics series on Special Relativity. This time, they are tackling a topic that I see being asked numerous times : velocity addition. ("If I'm traveling close to the speed of light and I turn on my flashlight.....").

I know that this topic has been covered here many times, but it is worth repeating, especially since someone may have missed the earlier ones.



Zz.