March 12, 2010

Big Bang for beginners-1: The nature of matter

(My latest book God vs. Darwin: The War Between Evolution and Creationism in the Classroom has just been released and is now available through the usual outlets. You can order it from Amazon, Barnes and Noble, the publishers Rowman & Littlefield, and also through your local bookstores. For more on the book, see here. You can also listen to the podcast of the interview on WCPN 90.3 about the book.)

I was recently asked by a relative to provide a simple explanation of the Big Bang theory 'in words of one syllable', i.e., without using jargon or esoteric scientific concepts and in a way that it could be understood by non-scientists. So here goes my attempt at fulfilling that request. In doing so I have tried to follow a paraphrase of Einstein's dictum that says that when explaining something we should make things as simple as possible, but not simpler. In other words don't distort in the search for simplicity. In trying to achieve this goal, I have created a multi-part series. (I promised my relative that my explanation would be simple, not short!)

But it is inevitable that in explaining a sophisticated scientific theory like the Big Bang to non-scientists, in essence telling it in the form of a story, some distortions will creep in, not the least because this is not my area of specialization and so I may simply not be as up-to-date as I should be. An excellent site for more current and authoritative information is one put together by Professor Edward Wright of UCLA. In particular he has put together a tutorial and a valuable FAQ page that enables one to quickly find answers to questions, and I have helped myself from that resource so generously provided.

I will readily acknowledge that I will also consciously introduce some distortions by taking the kind of liberties that film makers do when adapting books to create a screenplay, by omitting those characters that are peripheral to the story in order to maintain focus and brevity. My main omissions will consist of some elementary particles of matter that do not add anything to the basic story. Those who want a highly readable yet more accurate treatment of the basics of the theory are well advised to seek out what I think is still one of the best popular treatments of this subject, and that is Steven Weinberg's The First Three Minutes (1988). Though it does not have anything about the more recent observations and refinements (such as dark matter, dark energy, and cosmic inflation), the basic paradigm it presents is still valid.

The Big Bang theory seeks to explain how the physical universe that we now inhabit came about. Since it now consists of lots of stuff, one needs to first start by looking at what that stuff (i.e., ordinary matter) consists of. This exercise turns out to be like peeling an onion. As each layer of matter is examined, it reveals another layer below it.

Most everyday stuff (plants, animals, plastics, etc.) is made up of tiny but complex entities called molecules that give them their distinctive properties and which are held together by attractive forces. To separate matter into individual molecules, we need to apply an external force that is sufficient to overcome the force that binds a molecule to its neighbors. Doing so requires us to expend some energy as well.

Each individual molecule is in turn made up of simpler entities that we call atoms, which are also held together by attractive forces. Atoms are the units of matter that distinguish one element from another, and there are a little over a hundred such elements, oxygen, hydrogen, iron, carbon, being a few of the well-known ones. The periodic table lists all of them. A very simple molecule is that of water, which consists of just three atoms, two atoms of hydrogen and one atom of oxygen, held together by attractive forces. Other molecules, like the DNA that exist in the core of our body's cells and contain our genes, consist of millions of atoms joined together.

Atoms were once considered the most basic units of matter. They were thought to be indivisible but we know now that that is not true and that they too are composite objects, consisting of a tiny central core (called the nucleus) and electrons outside the nucleus, again held together by attractive forces. Electrons do seem to be truly fundamental particles that cannot be broken up into any smaller constituents.

The nucleus of an atom, however, turns out to be yet another composite object that consists of still smaller entities called protons and neutrons.

The protons and neutrons are now known to be composite objects too, consisting of even smaller entities called quarks and gluons.

So to summarize, when we peel off the layers of matter, the component units of which it is made are, in order of decreasing size:

This is where things stand now.

Are the quarks and gluons (and electrons) the ultimate constituents of matter? We don't know for sure but given past history with the onion-like nature of matter, we should not be too surprised if searches reveal yet another layer beneath the current one.

Why is it that we do not know if quarks and gluons are the ultimate components of matter? The reason comes down to the fact that it takes force and energy to separate matter into its smaller constituents, and the force and energy required increases rapidly as one moves down the chain of matter. It takes a small amount of energy to separate molecules into atoms. It takes much more energy to separate atoms into nuclei and electrons. (Some electrons can be removed from atoms by just rubbing materials together, which is the source of what we call 'static' electricity.) It takes much greater energy to separate nuclei into protons and neutrons, which is why we need huge and expensive accelerators to do so. When it comes to separating protons and neutrons into quarks and gluons we seem to have reached the limits of our ability. We have not actually been able to create quarks and gluons as free objects but instead can only study them while they are still inside nuclei.

The reason that we cannot produce free quarks and gluons is thought to be due to the fact that the forces holding them together in protons and neutrons are like the forces exerted by rubber. When you try to separate two objects that are joined by a piece of elastic, the force you need to apply keeps increasing as the objects move apart. With real rubber bands, the band breaks at some point and the two objects break free of each other. But with the rubber band-like forces holding quarks and gluons together, we have not been able as yet to create forces that can break the bands, leaving us unsure whether they can be broken if only we could to make the forces large enough, or whether they simply cannot be broken, ever.

Next: The nature of energy

POST SCRIPT: Harry Markopolos

In my series on financial frauds, I wrote about the Bernie Madoff scandal and how Harry Markopolos's repeated warnings that Madoff was running a scam were ignored by the regulatory authorities and the media. He appeared recently on The Daily Show to repeat those charges.

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Thanks for this Mano. It will be good to have a refresher (and you are already pretty much at the limit of what was taught when I was in school!). I have a basic understanding of the Big Bang, but struggle to visualise it. If you aren't planning on covering it in this series, another area that I really really really struggle to get any sort of comprehension is String Theory - so if you think you can simplify that sufficiently, it could make a pretty good post/series of posts.

Posted by Bill on March 12, 2010 07:32 PM


I am afraid that string theory may be a little too far out of my reach. It is highly mathematical and abstract. I have not been a fan of it because of its lack of an empirical basis and so have kept my distance. Its star also seems to be fading because of the lack of contact with data.

This does not mean it is wrong, of course, but just that I would have little more to add to what any informed layperson would know.

Posted by Mano on March 13, 2010 09:14 PM

Thanks Mano. Shame. I would just love to get a mind picture of all those vibrating strings and extra dimensions; knew that it was highly mathematical (extra dimensions make perfect sense in a mathematical context, but the real world???)

Love reading your stuff.

Posted by Bill on March 14, 2010 04:14 AM

We experimentalists are always poking fun at theorists but we save our meanest jokes for the string theorists.

While I have no problem with the idea of people working on a potentially faulty theory, what I have never understood is the glut of people that work on string theory. Perhaps it is because I don't grasp the actual research problems, but it seems like there simply cannot be THAT much work to do if there is no data to fit the model to.

Posted by Jared A on March 16, 2010 03:04 PM


You may be interested in the book The Problem With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next by Lee Smolin, himself a lapsed string theorist, who argues that string theory has badly led the field astray.

I bought the book recently and glanced through the first chapter but haven't had time to read it yet, though I will soon.

Posted by Mano on March 16, 2010 04:17 PM

Thanks Mano,

I've always been a fan of Stephen Hawking's books, as they seem to break down this sort of material for the layman. I think it is a very important subject for people to learn about, but has typically been enshrouded in dense academic prose.

Posted by Brian on March 21, 2010 08:40 PM

I can only agree Mano, it's almost as though some of the information is intended to be hidden away. Steven Hawking's is well worth the read for anyone - and his books deserve their popularity.
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Posted by Pat on May 3, 2010 05:58 PM