Big Bang for beginners-12: Measuring the rate of expansion 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.

We seem to be living in a runaway expanding universe. Given that we are confined to such a tiny region of what seems like an infinite space, how can we know so much about it? It is indeed a tribute to the doggedness of the scientific endeavor that we can investigate the universe so methodically and tease out answers to questions that at first glance might seem hopelessly out of reach. In this post, I want to give some further background about how we have figured out some of this information.

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Big Bang for beginners-11: Relativity theory

(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.

So far I have been simply describing what the Big Bang theory says without giving much of the theoretical background. But Einstein’s General Theory of Relativity (like Darwin’s theory of evolution by natural selection) has had such a profound effect on our relationship with the rest of the universe that I feel obliged to give readers, at least for cultural purposes, a glimpse of what the theory is and why it is so powerful, even if it remains obscure in its details. So for the sake of greater completeness and for the benefit of those who want to know more, in this post and the next I will give some of the theoretical background to what I have been saying so far, and hope that even those who are averse to algebra will stick with me through it and get some of the flavor of how the theory works.
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Big Bang for beginners-10: The cosmological constant

(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.

To understand what is going on with dark energy, we need to look at something called the cosmological constant.

Einstein’s General Theory of Relativity, when expressed as equations in their most general form, contains a constant term (called the cosmological constant) whose value is unspecified by the theory itself but influences how the universe evolves with time. A positive value for this constant would have the effect of acting like an outward pressure trying to ‘push’ the universe apart, counteracting the gravitational attraction that is trying to pull it together. A zero value would do nothing, leaving gravity as the only (attractive) force. A negative value would be like a ‘pull’, adding to the attractive force of gravity.
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Big Bang for beginners-9: Dark 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 addition to the appearance of dark matter, another interesting development arose when observers tried to determine the curvature of the universe, an important fact in determining the ultimate fate of the universe.

To understand this consider, as an analogy, a ball thrown upwards from the surface of the planet. It will slow down as it goes up due to the gravitational attraction of the planet’s mass. But will the ball eventually fall back to the ground or will it escape from the planet and go on forever? The answer depends on both the speed of the ball and the size of the planet. For a given speed of the thrown ball, if the mass of the planet is below a certain value, its gravitational pull on the ball is not sufficient to bring it back and the ball will escape and travel out in space forever.
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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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