Big Bang for beginners-8: Star formation and dark 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.)

For previous posts in this series, see here.

In the study of our universe so far, one fact becomes resoundingly clear. Humans occupy a tiny volume of the universe. All our scientific theories have been discovered using data that has been generated within that volume. What gives us the confidence that these same laws can be applied to distant regions as well? One answer is that we have no choice but to make that assumption. Another is that when do make such an extrapolation we get a reasonably satisfactory understanding of the behavior of distant stars and galaxies, thus justifying our decision.
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Big Bang for beginners-7: What lies beyond the edge of the universe?

(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.)

For previous posts in this series, see here.

The idea of an infinite space that has always existed and in which everything else just moves around seems intuitively reasonable, at least to those who are comfortable with the concept of infinity. But the idea that there is no edge or boundary to the universe is much harder to grasp.

Going back to our raisin bread analogy, asking the question “What is beyond the edge of the universe?” is akin to asking what exists outside the space occupied by the dough. The answer is that there is no space outside the dough. The dough is all the space there is. This is where the raisin bread analogy starts to be misleading because we cannot help but view the dough as expanding inside the space of the oven, and it is hard to eliminate that unwanted extra image of oven walls. (If we wish, we can envisage a small portion of the dough and speak of the boundary of that portion alone, but that is not the boundary of space as a whole. It would be like speaking of the boundary of our Solar System or the Milky Way galaxy.)
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Big Bang for beginners-6: The evidence

(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.)

For previous posts in this series, see here.

Why has the Big Bang theory become the standard model for understanding the origins of the universe? In the 15th century and earlier, most people thought that the Earth was the center of the universe and that the stars were embedded in a celestial sphere beyond the outer planets and that the size of the universe was not much larger than the Solar System. The Copernican revolution (with the publication of his book in 1543) displaced the Earth from the center of the universe. This led to suspicions that the universe could be very large, possibly even infinite, but there were at that time no good theories to explain its origins and structure.
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Big Bang for beginners-5: Some conceptual challenges

(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.)

For previous posts in this series, see here.

Although the story of the Big Bang in its essence is quite simple and straightforward, it contains many fascinating subtleties that are worth exploring further. It is good to get some conceptual hurdles and misconceptions out of the way right now.

When we use the words ‘Big Bang’ it immediately conjure up certain images. We immediately think of familiar explosions, like bombs or firecrackers going off. We envisage a big noise and the exploding pieces hurtling away from the center of the explosion and spreading out into the surrounding space at great speed. This image captures correctly the idea of a hot compressed beginning with a fixed amount of matter spreading out through space and getting cooler and more dilute with time. But there are important ways in which the image is inaccurate.
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Big Bang for beginners-4: The speed of cosmic evolution

(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.)

For previous posts in this series, see here.

What may surprise people is how rapidly the universe went from a very hot initial state to one in which it was cool enough for atoms and molecules to form. If we push our theories back as far as we dare, bearing in mind that we have stretched them to the limits and that we may well be wrong in some aspects, the earliest time that we can speak of is 10-43 seconds after the Big Bang (called the Planck time). i.e., this is 0.0000… 0001 seconds (43 zeros in all, including the one before the decimal) after the Big Bang. In other words, it is a really tiny time. It is estimated that the temperature of the universe at that time was about 1030 degrees. That is 10 followed by 30 zeros, a really huge number.
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Big Bang for beginners-3: The basic story

(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.)

For previous posts in this series, see here.

The starting point of the Big Bang story is a cosmic event that started out small and expanded rapidly (like an explosion). This event brought into being the universe we now inhabit and produced all the matter that our universe is presently composed of, though not in its present form. The time at the beginning is arbitrarily set to zero.

We do not know what happened right at the very beginning (at time zero by our convention) because our known theories are believed to not apply right at the beginning. So our story begins very shortly after the Big Bang occurred. It is believed that what existed then were quarks, gluons, electrons, and photons that were moving freely around in a hot dense gas called a plasma. (There were also a few other exotic particles that I will ignore as they are not central to a basic understanding of the evolution of the universe). As the universe expanded over time, these quarks and gluons and electrons and photons eventually became the ordinary matter that we now have. No new matter was created after the Big Bang, but the form that the matter took did change dramatically.
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Big Bang for beginners-2: The nature of energy

(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.)

For previous posts in this series, see here.

In order to understand the Big Bang theory, we also need to have an understanding of the nature of energy in addition to that of matter that was discussed yesterday. The word ‘energy’ has a technical meaning in science but has also entered into the vernacular and thus has been used to mean many things. In everyday language, it usually signifies the source of the ability to do things, such as move objects or break them up or put them together. So gasoline provides the energy to run cars, coal the energy to heat things, and so on.
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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!)
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Emotional reactions to Darwin

(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.

Because of the holidays and travel overseas where internet access will be sporadic, I am taking some time off from writing new posts and instead reposting some of my favorites (often edited and updated) for the benefit of those who missed them the first time around or have forgotten them. New posts will start again on Monday, January 18, 2009.)

There is no doubt that Darwin’s ideas about evolution by natural selection carry a huge emotional impact. For many people the idea that “we are descended from apes” is too awful to contemplate and is sufficient reason alone to dismiss any claim that natural selection holds the key to understanding how we came about. (Of course, we are not descended from apes. The more accurate statement is that apes and humans share common ancestors, making them our cousins, but even this refinement does not take away the stigma that supposedly comes with being biologically related to animals such people consider inferior.)
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Looking for deep ancestors

(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.

Because of the holidays and travel overseas where internet access will be sporadic, I am taking some time off from writing new posts and instead reposting some of my favorites (often edited and updated) for the benefit of those who missed them the first time around or have forgotten them. New posts will start again on Monday, January 18, 2009.)

Richard Dawkins in his book The Ancestor’s Tale (2004) tells a fascinating story. He models his book on a journey that, rather than moving through space to a particular destination, is moving in the temporal dimension, going steadily back in time. He calls it a “pilgrimage to the dawn of evolution.” He starts with present day humans and follows them back into history. One reason he gives for going back in time instead of starting at the beginning and going forwards as is more commonly done is to avoid a common trap of perception. When you tell the story forwards, it is hard to avoid giving the impression that life evolved purposefully, that human beings were somehow destined to be. This is counter to evolutionary theory that says that evolution is not directed towards any goal. It tells us how the present emerged from the past. It does not tell us how the future will emerge from the present.

Dawkins points out that the another advantage of telling the story backwards is that you can choose any of the current species and go back in time and tell pretty much the same story.

As I have mentioned earlier, we quickly (in just 2,000 years) reach the time when the most recent common ancestor lived and soon after that (about 5,000 years ago) reach a point when all our ancestors were identical.

But this convergence of ancestry is not just for humans, it is for all species. If we go far enough back in time, even my dog Baxter and I share the same ancestor, which I find a very appealing notion.

Anyway, here is a concise summary of the landmarks on this pilgrimage back in time, along with some other landmarks.

About 10,000 years ago, the agricultural revolution began and about 12,000 years ago saw the beginnings of language. About 160,000 years ago saw the beginning of what we would consider modern humans, and beyond that we start reaching the precursors to modern humans, a famous milestone being the fossil Lucy, dated to 3.2 Mya (million years ago).

As we go further back in time in this pilgrimage, other species start ‘joining us’ in our journey. What this means is that we reach times at which an earlier species existed which then split into two branches and diverged evolutionarily to what we see now. So if we go back further in time, we should cease to view the pilgrims on the journey as a combined group of humans and other species but instead see the travelers as that earlier common ancestor species. He calls these common ancestors ‘concestors’. (Concestor 0 in Dawkins’ scheme is the most recent common ancestor of all humans (or MRCA) that I have discussed earlier and who lived just a few thousand years ago.)

Going back in time, at 6 Mya we meet concestor 1 when we join up with the ancestors of chimpanzees. As we go even back further, we (and when I say ‘we’, I remind you that we should not think of ‘us’ as humans at this point but as the common ancestor species of humans and chimpanzees) join up at about 40 Mya successively with gorillas, orang utans, gibbons, and finally monkeys. Remember that the ‘pilgrims’ look different as we pass each concestor point.

Concestor 8 occurs at about 63 Mya when we join up with mammals like lemurs and lorises. (Just prior to this, around 65 Mya, was when all the dinosaurs went extinct.) As you can imagine, concestor 8 would not look much like present-day humans at all.

About 75 Mya, we join up with rats, rabbits and other rodents (concestor 10), at 85 Mya with cats and dogs (concestor 11), at 105 Mya with elephants and manatees (concestor 13), at 310 Mya with snakes and chickens (concestor 16).

At 340 Mya, we make a big transition when join up with the ancestors of amphibians, such as frogs and salamanders (concestor 17). This point marks the first time that animals moved out of the water.

Around 440 Mya we join up with various kinds of fish (concestor 20), and around 630 Mya with flatworms (concestor 27).

After various other species ancestors’ join ours, the next big rendezvous occurs at about 1,100 Mya when we join up with the ancestors of fungi, such bread molds and truffles (concestor 34).

Some time earlier than that (passing the connection with amoeba at concestor 35) but before 1,300 Mya (it is hard to pin the date) is when the next major transition occurs when we join up with green plants and algae. This common ancestor is concestor 36.

At about 2,000Mya we arrive at concestor 38 where every species is now represented by a eukaryotic (nucleated) cell.

At about 3,500 Mya we meet up with our earliest ancestors, the eubacteria (concestor 39), the original form of life.

Dawkins’ reverse story can be seen visually, told in a beer commercial in 50 seconds flat to the pounding beat of Sammy Davis Jr. singing The Rhythm of Life. (A minor quibble: There is one way in which this fun visual representation is not accurate. It shows three humans going back in evolution until we join up with ancestors of the present-day amphibians (concestor 17) in identical parallel paths. This is ruled out by the reductio ad absurdum argument written about earlier, where it was established that all present day humans must have had a single common ancestor in any earlier species.)

I must say that this book was an exhilarating journey. To see the whole of the evolution of life going backwards and merging together was a nice new way of seeing the process. Those of you who are interested in the grand sweep of evolution written for a non-specialist will find Dawkins’ book a great resource.

POST SCRIPT: The Boxer

A live performance of Simon and Garfunkel singing one of my all-time favorite songs The Boxer.