Sunday, July 30, 2017

Is Radiation Dangerous?

Believe it or not, there are still people out there who get scared witless and going out of their minds with their phobia about "radiation". I get questions related to this often enough that whenever I find info like this one, I want to post it here.

Don Lincoln decides to tackle this issue regarding "radiation". If you have little knowledge and idea about this, this is the video to watch.


Quantum Tunneling Time

Chad Orzel has highlighted a couple of papers (one still a preprint) on the issue of quantum tunneling time or speed. I missed these, just like him, but unlike him, I didn't have as glamorous of an excuse - I was busy finishing up teaching a summer physics class.

I'll let you read have the pleasure of reading his article, because he also gave a quick background on the quantum tunneling phenomenon, if you're not familiar with it. But as background information, I did quantum tunneling spectroscopy measurement for my PhD research and dissertation. So I'm familiar with this, but not in the sense of the detailed question on tunneling time. We simply used the phenomenon to measure the properties of the material of interest, even though in the end, I ended up looking into the detailed description of the tunneling matrix elements, which are often simplified or ignored.

Still, the issue of tunneling time has always been something in the back of my mind, and the question on whether this thing happens "very fast" or "instantaneously" (just like quantum entanglement) has always popped up now and then. It is good to see new studies on this, even though the combined conclusion out of these two results is still uncertain.


1. N. Camus et al., Phys. Rev. Lett. 119, 023201 (2017).

Tuesday, July 11, 2017

The Higgs - Five Years In

In case you've been asleep the past 5 years or so and what to catch up on our lovable Higgs, here is a quick, condensed version of the saga so far.

Where were you on 4 July 2012, the day the Higgs boson discovery was announced? Many people will be able to answer without referring to their diary. Perhaps you were among the few who had managed to secure a seat in CERN’s main auditorium, or who joined colleagues in universities and laboratories around the world to watch the webcast.

This story promises to have lots of sequels, just like the movies released so far this year.


The Universe's First Atoms Verify Big Bang Theory

The Big Bang theory makes many predictions and consequences, all of them are being thoroughly tested (unlike Intelligent Design or Creationism). These predictions and consequences are quantitative in nature, i.e. the theory predicts actual numbers.

Many of these "numbers" have been verified by experiments and observations, and they are continually being measured to higher precision. This latest one comes about from the prediction of the amount of certain gases during the early evolution of our universe.

But more data has just come in! Two new measurements, in a paper just coming out now by Signe Riemer-Sørensen and Espen Sem Jenssen, of different gas clouds lines up with a different quasar have given us our best determination of deuterium's abundance right after the Big Bang: 0.00255%. This is to be compared with the theoretical prediction from the Big Bang: 0.00246%, with an uncertainty of ±0.00006%. To within the errors, the agreement is spectacular. In fact, if you sum up all the data from deuterium measurements taken in this fashion, the agreement is indisputable.

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