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A is for Astronomy


Plain Talk with Brilliant Scholars

Welcome to Curioser and Curioser: Plain Talk with Brilliant Scholars, yet another new weekly online feature for Independent.com. Each Wednesday in this space, you can find interviews with noted scholars on topics ranging from science to society, arts to arithmetic. We’ll be going through the alphabet for the next six months, starting with this week’s “A is for Astronomy.” So read on, and let us know what questions and topics you’d like us to cover. In this first edition of Curioser and Curioser, reporter Martha Sadler contacted UCSB physics professor Robert “Ski” Antonucci. Her questions are both intentionally naïve and conceptually deep, providing something interesting for both astronomy no-nothings and experts alike. Said Sadler, “Some of the professor’s answers are short and easy to grasp, while others might require more study—but it’s all very interesting.” But before we get to the questions, here’s what Ski had to say about participating: “Okay Martha, I’ll try! These are of course deep questions. For some of them, science has provided a very clear precise answer which has been tested many, many times, and is essentially universally accepted by scientists. For some of the questions, it’s not so clear. And for one of them, we will probably NEVER know the answer with any certainty.” And here we go: How did the universe begin? If applicable, please explain how something came from nothing. This will be my most frustrating answer. There are ideas by people such as Steven Hawking about how “baby universes” are created, but they remain speculative, to say the least. I will say this, though: Just as the surface of a balloon is finite, yet has no boundary, the spacetime making up our whole universe may, according to present knowledge, also be finite yet have no boundary, either in time or space! This is because spacetime, in common with the surface of a balloon, has the property of curvature. So asking what happened before the Big Bang may be just like asking what is north of the North Pole! Can you describe the model of the universe that is based on ether? The idea is enjoying some vogue now. Is it at all respectable? In a word, no. The ether idea was rejected decisively a century or more in the past because of failed predictions too numerous to mention. The idea behind the ether was that light behaves in some ways like waves on the ocean, with speeds and frequencies and wavelengths. Since water waves travel in a medium (the water itself), it was thought that by analogy, there must be smooth space-filling substance for the electromagnetic wave (light) to travel in.

I’ve heard that some research astronomers at other universities are currently entertaining the notion of ether, as reported in last month’s National Geographic article titled “Dark Mass’s Rival.” Ether seems to answer a lot of questions, reducing pressure on the curious layperson to understand Einstein’s general and special theories of relativity, black holes, and string theory, as well as dark matter. This article presents a completely new and idiotic use of the word ether. These people have apparently redefined the term in their minds to mean anything that fills all of space. It’s just very unfortunate that they picked a word with all of that historical baggage. I don’t think the scientists working on this are confused about the usage, but for sure it confuses the hell out of members of the public who are trying to follow these things intelligently. However, I suppose it’s semantics and people can say what they want. Remember this from Through the Looking Glass? “When I use a word,” Humpty Dumpty said, in a rather scornful tone, “it means just what I choose it to mean—neither more nor less.” “The question is,” said Alice, “whether you can make words mean so many different things.” “The question is,” said Humpty Dumpty, “which is to be master. That’s all.” Here ether is referring to some hypothetical substance that might in principle invalidate the arguments for dark matter. The idea is so hypothetical that it’s not worth considering except by a few specialists. The chance that it is correct is miniscule, as the proposer essentially acknowledges. That doesn’t mean it’s bad science: People should always be coming up with wild ideas and checking them out. But it’s completely nutty to bother the public with them at this stage of development. There has been a gigantic unexpected discovery that is totally worthy of everyone’s attention. There is a newly discovered space-filling material that has revolutionized our view of the universe, though it has nothing to do with light propagation. It’s a million times more important than the so-called “ether” discussed in the article. This discovery has told us what the dominant component of matter is in the universe—dark energy—and explained the observed flatness of space overall. So what is dark energy? It’s been discovered over the last decade that the expansion of the universe is speeding up. Since the three forces in nature (electroweak, strong, and gravity) known in 1995 can’t explain an acceleration of universal expansion, is was posited that perhaps there’s a previously unknown substance that fills all space, and that one sample of the stuff repels other samples of the stuff. This would cause the expansion to speed up, just as an attractive force such as the usual gravitational force would cause the expansion to slow down. It wouldn’t be crazy to call it antigravity, but that term isn’t very well defined. Again, in no way does this conflict with relativity. In fact there is a mathematical place in Einstein’s equations for putting in a repulsive force, should one ever be discovered, and the observed acceleration may be a manifestation of such force. If we’re stuck with relativity, can you just explain why space and time can’t be two different things instead of spacetime? I prefer them as two different things. Let’s make an analogy with sound waves. Sound waves comprise compressions and rarefactions (thinning) of the air (or water, etc). It does need a medium in which to exist, by its very definition. In a vacuum, there can be no sounds at all. Suppose you are at the train station and you hear the whistle of a stationary train blow in preparation for leaving the station. You can use pressure sensors to measure the sound wavelength. If the tone is middle C, each wave is about four-feet-long. When a similar train approaches the station, the waves are bunched up (this would be true of a water wave as well), and we measure a shorter wavelength, say three feet. Now suppose the train is stationary, and we are approaching it. The whistle blows, and we measure the wavelength as the full four feet! The crucial point is that, while in the second and third cases the distance between train and listener is decreasing, in only the second case is the measured sound wavelength shortened. That must always be the case if a wave is propagating through a stationary medium such as the air or (for light) an ether. But light simply doesn’t behave that way. Whether the light source is moving towards us, or vice-versa, you still get the compression in wavelength. In fact, for that reason, it’s not possible to say whether it is the train or the listener that is “really” moving based on this experiment. You know how space goes on forever and ever and ever and ever and ever? Do you think the infinitude is infinitely filled with galaxies and the like? We don’t know whether or not space goes on forever. Do you know that when you look at the sun (don’t try this), you do not see the sun as it is right now? Since it took about eight minutes for the light (carrying the image of the Sun) to get to Earth, we’re actually seeing the Sun as it was eight minutes earlier! Of course, it probably doesn’t look much different now, but this establishes the principle that when we look at distant objects, we see the objects as they were back in time. There is overwhelming evidence that the age of the universe is close to 14 billion years. I can’t explain it all here, but the first simple and powerful clue was that all the galaxies are observed to be separating from each other. So using the formula “distance = speed times time,” we can calculate how long it’s taken for the galaxies to get as far apart as they are today. The answer is 14 billion years. If you look at an object so far away that the light we now see actually left the object 13 billion years ago, we say that the object is 13 billion light years away. We see the object as it was 13 billion years ago, and thus when the universe was only 1 billion years old. We can study a certain signature of light left over from the early history of the universe. It’s called the Cosmic Microwave Backround. and its existence was predicted in advance with all the exact right properties! We see this light as it was emitted when the universe was only 300,000 years old. So we can see things as they were closer and closer to the beginning of time. Now ask me what the universe is like 50 billion light years away. Answer: Don’t know! According to present understanding, the light from any objects that far away simply hasn’t gotten here yet, so we can’t see them, however big our telescopes! The maximum distance that we can see due to the finite age of the universe is called the Cosmic Horizon. The volume of space within the Cosmic Horizon is called the Observable Universe. There are ideas about what lies beyond that, or regarding the existence of alternate universes. They may be true but I don’t think they can ever be tested decisively, so I’m not too interested in them. Do phenomenon also get infinitely small, such as worlds within worlds? No one knows this. So far it seems to be true. Maybe we’ll never be able to answer the question, because whatever extremely small pieces of matter that we do discover, I think it’s always possible that they’re made of even smaller pieces. Do you suppose the universe is comprised entirely of cause and effect chains, or is there wiggle room for chance, divine intervention, or human will? There is definitely, definitely room for chance, and this has been proven many times! Suppose we have two atoms of radioactive Uranium. These atoms are according to present, very solid knowledge, exactly the same. Yet one will emit a radioactive particle before the other, by chance!!! Is there a point at which astronomy ceases to be intuitive, or at least analogous to something we can sense? Yes. Often in science it turns out that a pattern in nature cannot be explained by an analogy to something in everyday life, and some behavior in nature seems to run counter to our intuition. Relativity and quantum mechanics are two excellent examples. The reason is likely to be that our intuition and common sense evolved for preferentially passing on our genes on a planet with gravity is weak compared to that of a black hole. On earth, where things generally move much slower than a light beam and so many particles are involved, intuition about the effects of quantum mechanics does not help us biologically. At that point, what good does it do to study it? Most of us would say that’s where it gets extremely interesting and seductive. There are also many crucial technological applications. For example, pilots and others often find their location to good precision by receiving radio signals from the “Global Positioning System” of satellites. For this to work, we need to know the exact locations of the satellites at any given time. These positions can only be predicted very precisely by using Einstein’s theory of gravity, which includes the mixing of time and space, black holes, etc. (Remember, theory does not mean hypothesis in science. We call it Einstein’s “theory” of gravity even though all its predictions have come true perfectly!) Thus, if Einstein’s theory weren’t known, this positioning system wouldn’t work, and planes would crash all the time. When do you think we will communicate with creatures on other planets? This one is way too hard. I think we should at least try listening though. It’s not that expensive compared to other things. There are efforts being made to detect signals from intelligent extraterrestrial beings, though not on this campus. See for example seti.org on the internet. If you allow them to use your computer when you’re not using it, your machine may be the one to find the extraterrestrials. This particular research group was portrayed in the book and movie Contact. The major characters in that story are real people, although of course they haven’t yet found any extraterrestrials. Do you think the terrestrial distinction between plant and animal, or even animate and inanimate, is universally applicable? I sure don’t know. Roughly speaking (biologists will cringe at this simplification), plants get their energy from light, and animals get their energy from chemicals (usually synthesized by plants using light energy). I wouldn’t be too shocked if there were the same two general categories on other planets. Is there any reason to think extraterrestrial beings will resemble earthlings, or are they just as likely to be spherical or incredibly small or large or something? It is extremely likely that they will be extremely different from us in their level of biological and technological evolution. There is a wonderful explanation of this in Carl Sagan’s book The Dragons of Eden. He says that to get a feeling for the history of the universe, let’s pretend the whole thing took just one year. On that scale, if the origin of the Big Bang expansion was on January 1, then Sagan estimates that the formation of the Earth would have taken place somewhere near the middle of September. The first fossils come from organisms that lived in October. The dinosaurs were around in late December. Humans arrived at very roughly 1:30 p.m. on December 31. Neolithic civilizations emerged on 11:59:35 p.m. on December 31. The Renaissance in Europe occurred at 11:59:59 p.m. And just about on the dot of New Year’s, we developed the technology to self-destruct, and to start contemplating interstellar travel. His point is, even if by some chance life evolves on another planet in exactly same way as it does here, it would be impossibly unlikely for it to be synchronized with life on Earth so closely that they look the same and have the same technology. It is much, much more likely that life on the other planet would be millions or billions of years behind us or ahead of us. Is there anything you’d like to address? Yes, I’d like to tell you my view on the scientific method, which I don’t think is controversial. I simplify it to two essential steps. 1) Development of a hypothesis based on a collection of observational and experimental data. This step is an example of inductive reasoning, dreaming up a general pattern or equation based on study and contemplation of much experimental information, often aided by what one might call intuition or even genius. 2) The second step of the scientific method is deduction of the consequences of the proposed formula, to see if it “pans out.” For example, since all the predictions of quantum mechanics have come true perfectly, this is the theory of greatest value in understanding the universe, and in, say, reproducing recorded music. Note that in science the word “theory” is used for a pattern of behavior, no matter how solid the explanation may be. That’s different from the usage in everyday life [which implies something that is unproven]. In my opinion, all other belief systems (astrology, religious creation myths, etc.) are based on the first step, and the second step is simply neglected. In scientific experimentation, we engage in a respectful dialogue with nature, and we change our ideas when they lead to predictions which don’t come true.

Keep the Conversation Alive

Learn more about Ski and his research by clicking here or email him at ski@physics.ucsb.edu.

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