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The 21 cm line of hydrogen in Radio Astronomy

June 30, 2013 2 comments

 

This has been a wonderful discovery back in the 1950s that gave Radio Astronomy a good push forward. It also helped in mapping out our Milky Way galaxy (which we really can’t see very well!).File:Galaxy NGC 1232.jpg

It arose from a feature of quantum field theory, specifically from the hyperfine structure of hydrogen. (I’ll try to explain.)

You know that the hydrogen atom consists of a single proton at its central nucleus and a single electron moving around it somehow in certain specific quantized orbits. It cannot just circle around in any orbit.

That was one of Niels Bohr’s major contributions to our understanding of the atom. In fact this year we’re celebrating the 100th anniversary of his model of the atom (his major papers written in 1913). Some articles in the June issue of Nature magazine are in honor of Bohr’s work.

Normally the electron circles in the lowest orbit associated with the lowest energy state – usually called the ground state (the one with n = 1).

It is known that protons and electrons are particles that have “spin”. (That’s why they are sometimes also called ‘fermions’.) It’s as if they behave like spinning tops. (The Earth and Milky Way are spinning too!)

The spin can be in one direction (say ‘up’) or in the other direction (we label as ‘down’). (These labels of where ‘up’ and ‘down’ are depends on the coordinates we choose, but let’s now worry about that.)

When scientists looked at the spectrum of hydrogen more closely they saw that even while the electron can be in the same ground state – and with definite smallest energy – it can have slightly different energies that are very very close to one another. That’s what is meant by “hyperfine structure” — meaning that the usual energy levels of hydrogen are basically correct except that there are ever so slight deviations from the normal energy levels.

It was discovered by means of quantum field theory that this difference in ground state energies arise when the electron and proton switch between spinning in the same direction to spinning in opposite directions (or vice versa).

When they spin in the same direction the hydrogen atom has slightly more energy than when they are spinning in opposite direction.

And the difference between them?

The difference in these energies corresponds to an electromagnetic wave corresponding to about 21 cm wavelength. And that falls in the radio band of the electromagnetic spectrum.

So when the hydrogen atom shows an emission or absorption spectrum in that wavelength level it means that the electron and proton have switched between having parallel spins to having opposite spins. When the switch happens you see an electromagnetic ray either emitted or absorbed.

It does not happen too often, but when you have a huge number of hydrogen atoms — as you would in hydrogen clouds in our galaxy — it will invariably happen and can be measured.

Now it’s a really nice thing that our galaxy contains several hydrogen clouds.  So by measuring the Doppler shift in the spectrum of hydrogen — at the 21 cm line! — you can measure the velocities of these clouds in relation to our location near the sun.

These velocity distributions are used together with other techniques to map out the hydrogen clouds in order to map out and locate the spiral arms they fall into.

That work (lots of hard work!) showed astronomers that our Milky Way does indeed have arms, just as we would see in some other galaxies, such as in the picture shown here of NGC 1232.

The one UNKNOWN about the structure of our Milky Way is that we don’t know whether it has 2 or 4 arms.

References:
[1] University Astronomy, by Pasachoff and Kutner. 
[2] Astronomy (The Evolving Universe), by Michael Zeilik.

(These are excellent sources, by the way.)

August Kekule’s Benzene Vision

June 30, 2013 2 comments

The first time I heard of August Kekule’s dream/vision was from my dear mother! (My mom is a geologist who obviously had to know a lot of chemistry.)  I am referring to Kekule’s vision while gazing at a fireplace which somehow prompted him onto the idea for the structure of the benzene molecule C6H6. And then I heard that the story is suspect maybe even a myth cooked up by unscientific minds. Now I have learned that Kekule himself recounted that story which was translated into English and published in the Journal of Chemical Education (Volume 35, No. 1, Jan. 1958, pp 21-23, translator: Theodor Benfey). Here is an excerpt from that paper relevant to the story where Kekule talks about his discovery.

I was sitting writing at my textbook but the work did not progress; my thoughts were elsewhere. I turned my chair to the fire and dozed. Again the atoms were gamboling before my eyes. This time the smaller groups kept modestly in the background.    My mental eye, rendered more acute by repeated visions of the kind, could now distinguish larger structures of manifold conformation: long rows, sometimes more closely fitted together all twining and twisting in snake-like motion. But look! What was that? One of the snakes had seized hold of its own tail, and the form whirled mockingly before my eyes.    As if by a flash of lightning I awoke; and this time also I spent the rest of the night in working out the consequences of the hypothesis. Let us learn to dream, gentlemen, then perhaps we shall find the truth.

And to those who don’t think The truth will be given. They’ll have it without effort.

But let us beware of publishing our dreams till they have been tested by the making understanding.

Countless spores of the inner life fill the universe, but only in a few rare beings do they find the soil for their development; in them the idea, whose origin is known to no men, comes to life in creative action.  (J. Von Liebig)

I believe it is unnecessary to rule out or ridicule dreams, trances, visions in the pursuit of scientific truth. Because, after all, they still have to be tested and examined in our sober existence (as Kekule already alluded). I see them as extensions of thinking and contemplation, and surely there is nothing wrong with these.

Einstein on theory, logic, reality

 

https://i0.wp.com/www.soundswitheinstein.com/wp-content/uploads/2012/12/einstein-guitar.jpg

Long ago (late 1980s) I attended a lecture by Einstein biographer I. Bernard Cohen. (Cohen actually interviewed Einstein and published it in the Scientific American in the 1955 issue.)

 
In his lecture, Cohen described Einstein’s view of scientific discovery as a sort of ‘leap’ from experiences to theory. That theory is not logically deduced from experiences but that theory is “jumped at” — or “swooped” is the word Cohen used, I think — thru the imagination or intuition based on our experiences (which of course would/could include experiments). This reminds one of the known Einstein quote that “imagination is more important that knowledge.”

In his book Ideas and Opinions, Albert Einstein said:

“Pure logical thinking cannot yield us any knowledge of the empirical world; all knowledge of reality starts from experience and end in it. Propositions arrived at by purely logical means are completely empty as regards reality. Because Galileo saw this, and particularly because he drummed it into the scientific world, he is the father of modern physics—indeed, of modern science altogether.”

(See Part V of his “Ideas and Opinions” in the section entitled “On the Method of Theoretical Physics.”)

In a related passage from the same section, Einstein noted:

“If, then, it is true that the axiomatic foundation of theoretical physics cannot be extracted from experience but must be freely invented, may we ever hope to find the right way? Furthermore, does this right way exist anywhere other than in our illusions? May we hope to be guided safely by experience at all, if there exist theories (such as classical mechanics) which to a large extent do justice to experience, without comprehending the matter in a deep way?

To these questions, I answer with complete confidence, that, in my opinion, the right way exists, and that we are capable of finding it. Our experience hitherto justifies us in trusting that nature is the realization of the simplest that is mathematically conceivable. I am convinced that purely mathematical construction enables us to find those concepts and those lawlike connections between them that provide the key to the understanding of natural phenomena. Useful mathematical concepts may well be suggested by experience, but in no way can they be derived from it. Experience naturally remains the sole criterion of the usefulness of a mathematical construction for physics. But the actual creative principle lies in mathematics. Thus, in a certain sense, I take it to be true that pure thought can grasp the real, as the ancients had dreamed.”

Note his reference to theory as being ‘freely invented’ (and even ‘illusion’) which echo the role of intuition and imagination in the scientific development of theory (but which are probably not completely divorced from experience either!).

The last two quotes above incidentally can be found online in Standford’s Encyclopedia of Philosophy: Einstein’s Philosophy of Science

 

Understanding Israel

December 9, 2012 Leave a comment

Israel’s decision to make plans on the E-1 region (not yet building, however, just planning at this stage) after the United Nations General Assembly vote on the Palestinian nonmember observer state has been much criticized.  In this post, I express my opinion on the Israeli response by contextualizing the many growing dangers in the region to Israel so as to understand where it is coming from.

My theory is that, yes, Israel has made its E-1 response to the UN vote but that this was idea was at the back of their minds only to be used as the last nail on the coffin amidst a serious growing regional threat. (I am aware of the US position, from back in the 1980s I think, that Israel should not build in E-1.)

Let us enumerate all these dangers that Israel faces to better appreciate its position and response.

1) There is the Iran nuclear threat to wipe Israel off the map. This is probably Israel’s biggest security concern right now – which only serves to justify Israel’s hardening position.

2) There are the regular Hamas rockets and missiles fired at Israel. These have increased in range and danger — e.g., the Fajr-5 rockets supplied by Iran to Hamas in Gaza.

3) There is the Hizbullah threat in Lebanon with 1000s of rockets and missiles aimed at Israel – and which are more deadly and with longer reach. (They can now reach Tel Aviv, Jerusalem, and other Israeli population centers.) Notice: the UN has done nothing about these.

4) There is the Islamist threat in the region, and especially in Egypt. Egypt is lead by the Muslim Brotherhood whose primary foreign policy is to establish an Islamist Caliphate empire with Jerusalem as its capital. There’s a trend to scrap the Peace Treaty. So that Treaty is only hanging by a hair.

5) Syria is quite unstable with its 2-year civil war. The danger exists, and is more probable, for Islamists to take it over the way they have in Egypt, Tunisia, Morocco, etc.

6) Turkey is an Islamist state though somewhat more ‘moderate’ but still quite hostile to Israel — and pretty thin-skinned about the flotilla fiasco which was their fault for not restraining the IHH. They have been confrontational with Israel and sympathetic to Hamas’ firing rockets at Israel. Being a NATO state, that does not bode well for Turkey and is certainly a danger to Israel.

7) Jordan looks to be quiet so far, but it can be affected by these regional trends – 40% of its population are Palestinian. Jordan could be in the news at any moment.

8) Sudan is a major arms depot/route for Iran to transfer and supply weapons to Hamas, Islamic Jihad, and other Islamists who want to infiltrate Israel from both Gaza and the Sinai. (Iran also supplies weapons to Hizbullah.)

You have all these dangers facing Israel and in addition you now have the Palestinians threatening Israel with the diplomatic vote at the United Nations.  All these threats put together from all around do a lot to undermine a two-state solution for a Palestinian state and a Jewish state living side by side in peace. These can only harden Israel’s position.

As a matter of fact, Palestinian collusion with all these regional players who threaten Israel have contributed to making the two-state solution much less viable. (It may in fact be dead.)  What is Israel going to do? Support a hostile Palestinian state right on its border in addition to the already existing threatening Islamist states? Accede to a Palestinian state that looks to become an Islamist Palestinian state?  Not in your life. Look at Gaza! Is that the kind of Palestinian state they’re hoping for? (One that is inspired by Egypt’s Muslim Brotherhood?)  In any case, we have two Palestinian visions and there’s no way for Israel to make peace with both of them if those two Palestinian camps can’t live together in peace.

Therefore, the way to fight the UN Palestinian vote, and to fight these many regional dangers, is to threaten the contiguous geography for the Palestinians. So in sum: no Palestinian state so long as they collude with those who want to wipe Israel off the map, fire rockets at Israel, and threaten Israel diplomatically. Actions not aimed at contributing to peace will not lead to a Palestinian state. Israel will build where it wishes. That, in my view, is a much better response than bloodshed.

The UN can make all the laws it wishes, but so long as it makes these laws without regard to Israel’s security given the all-round dangers, these laws will be one-sided, naive, futile, and they will be opposed and fought. Israel’s laws will take precedence over laws cooked up by an antisemitic body (comprising many nations some of whom are already ruled by thugs).  It will also mean that the UN has yet again failed to be the institution that it was designed to for. After all, the UN already failed several times before; e.g., in Congo, in Darfur, Sudan, in Syria.

Children of older fathers

August 23, 2012 Leave a comment

Sometimes when you put separate studies together you could get what seems a confusing picture (or maybe no picture at all?) — particularly seeing how they word their conclusions. Here is an example on studies related to offspring of older fathers.

Study 1. Older fathers have longer telomeres in their chromosomes as they age, so the offspring of older fathers inherit these longer telomeres, enhancing the life expectancy of the offspring.  This was reported by the BBC and is based on a study published in Proceedings of the National Academy of Sciences.

Study 2. Children born to older fathers have a greater likelihood of developing autism or schizophrenia.  Reported by Nature Magazine (here’s Nature’s summary of the actual Nature study) and also quite recently by the BBC.

Study 3. The life expectancy of people with schizophrenia is lower than average, and can be lower by as much as 10 to 15 years. Reported by the BBC and based on a study done by the British Biomedical Research Centre for mental health, and published in the online journal PLoS ONE.

 
These conclusions aren’t necessarily in contradiction to one another (even if verbally they seem to be). It depends on the various rates (such as the smaller fraction of schizophrenics, for example, compared with the many who don’t get mental illness). So if you’re normal and descended from an older father ‘the chances’ are better that your longevity will get a boost (statistically!) if you don’t get a mental illness like schizophrenia. (Barring a Study 4 and Study 5, about which I know nothing and which could wreck my post!)

I’ve often wondered if in some societies around the world these effects and results could be varied depending on the people being studied. There are still numerous factors beyond our control. (Anyway, whatever your condition, I hope this makes you feel better!) 🙂

Why I’m supporting Mitt Romney

August 10, 2012 Leave a comment

Here are my short & quick reasons for supporting Mitt Romney for US president.

1. Move to repeal Obamacare. Some businesses are already raising commodity prices because of it (e.g., one pizza chain) — and food prices are already on the rise outside of that.

2. Give the US economy a boost — a change in leadership helps give the economy a better turn. I’m with former mayor of Carmel, California, Mr Clint Eastwood who said we need a change in leadership and is endorsing Romney. I think he’s right. (And I won’t argue with the man with no name.)

3. Get the unemployment rate down, as it was under Bush. It went up when Obama became president.

4. Stronger and assertive foreign policy — not one that apologizes and bows to other leaders in shame. Many in Europe and Mideast are now taking a lesser view of Obama than in 2008 — his weakness loses the respect a president ought to have. Stand up to China and Russia more. The reset button gotten rusty and ain’t working. (Remember the reset button Hillary gave Putin?) Stand up to Iran more, and treat our friend Israel as a friend.

 

US Unemployment

August 7, 2012 Leave a comment

During 28 of the 38 months Obama has been in office (till ~ March 2012) the US unemployment rate was in the 9%-10% range. Under Bush most rates were in the 5%-6% range. Source: Bureau Labor Statistics.

US youth unemployment (ages 16-24) under Obama = 18.5% in 2009; 19.1% 2010; 18.1% 2011 – up from 14.0% in 2008.

California unemployment rate averaged to 11%-12% under Obama. Under Bush it averaged 6%.

Florida’s unemployment rate mostly in 10%-11% range under Obama. Under Bush they were mostly under 6%.

African American unemployment rates increased by 6+ points under Obama: 31-33% in 2009-2011 – up from 24.8% in 2008.