标签: universe

I was reading this month's issue of Discover magazine a few nights ago. At the back they had a piece titled "20 Things You Didn’t Know About Galaxies." The first point was that one of the first people to speculate that the Milky Way was not the only galaxy in the universe was the 18th century philosopher Immanuel Kant, who coined the term "Island Universe" to describe a galaxy.   Well, I for one thought that was pretty interesting. Previously, I'd thought no one had even considered the idea of galaxies until the 1920s when Edwin Hubble provided convincing evidence that the cloudy patches called nebulae in the night sky were located well beyond the Milky Way.     But that wasn't what grabbed my imagination. We've all heard size comparisons about different things, like "If protons and neutrons were the size of apples, then an electron would be the size of a..." Well, the author of the Discover article, Katherine Kornei, had something similar to this, but it was one I'd never heard before. This nugget of knowledge was as follows:   If the stars within galaxies were shrunk to the size of oranges, they would be separated by 4,800 kilometers (3,000 miles). If galaxies were shrunk to the size of apples, neighboring galaxies would only be a few meters apart.   I don’t know why, but this really made me think. I can't say exactly what it made me think, just that this little tidbit of trivia has lodged itself firmly in my noggin. How about you? Do you find this particular factoid to be of interest, or are you thinking "Everyone knows that" whilst trying to suppress a yawn?

I was lying in bed last night thinking about my recent blog, Why lunchtime is an illusion . In particular, I was thinking of the dynamic, ever-changing displays on the Poodwaddle.com website showing births and deaths and the total population of the planet (7,222,691,563 when I checked just a moment ago, but let's round it down to 7 billion for the purposes of these discussions). I know these counts are just a best-guess approximation based on what we know (and what we think we know), but I believe them to be close enough to the truth to make no difference. The "deaths" display is one that really sticks in my mind. As I get older, I become increasingly aware that one day I will be an element in that count (sad face). Actually, while we're talking about this, Paul Clayton pointed me at the Frequency page on xkcd.com. This really is awesome. I don't know who is in charge of xkcd, but he/she/it/they (see also my Gender-Neutral Prose blog) is/are absolutely amazing. This particular Frequency image provides a real-time graphical display reflecting the frequency with which a variety of disparate things are occurring as we speak. These include such off-the-wall items as a typical heartbeat, a fire department putting out a fire in the USA, a member of the UK parliament flushing a toilet, and a Sagittarius named Amelia drinking a soda (I couldn't make this stuff up if I tried). But that's not what I wanted to talk to you about... As I noted above, there are 7 billion-plus people on the planet Earth. I can't even wrap my brain around this. It scares me. Suppose we all had the same food to eat each day. Imagine 7 billion bananas being consumed for breakfast; 7 billion cups of coffee being quaffed during a mid-morning break; 7 billion cheese sandwiches being consumed at lunchtime; 7 billion chocolate cookies being nibbled in the afternoon; and 7 billion salmon fillets (along with, say, potatoes and peas) being scarfed for supper. Of course, the above would be an idyllic situation—the vast majority of people in the world should be so lucky—I daren't even think about the number of children with empty stomachs, not knowing where their next meal is coming from. At the other end of the spectrum we have people who consume much more than their fair share. I'm embarrassed to tell you how many cups of coffee I drink a day, for example. My mind is bouncing around from topic to topic like a Ping-Pong ball. Take a look at the following image, which is an artist's impression of what our galaxy, the Milky Way, looks like based on data gathered from a number of sources, including NASA's Spitzer infrared space telescope.   The Milky Way is about 100,000 light years in diameter. Our solar system is located in the Orion Spur approximately three fifths of the way from the galactic centre. I don't know about you, but this sort of thing makes me feel really insignificant (in a magnificent sort of way, of course). The thing is that by one path or another (the human brain is a strange and wonderful thing—it's certainly one of my three favourite organs), all of this this reminded me of Alone in the Universe by John Gribbin (click here to see my review ). Gribbin makes a very compelling case for the fact that we may well be alone (as an intelligent, technological race) in the universe. If we truly are the only intelligent, technological race in the universe, it would behoove us to take good care of each other and of the planet we call home. All I'm saying is that munching our way through 7 billion metaphorical bananas (they're the tastiest ones) a day is quite possibly not the best way to do this. What do you think?  

In my post How it used to be: Seeing the stars at night , I talked about how–on the way back from our Boy Scouts meetings when we were about 10 years old (circa 1967)–my best friend, Jeremy Goodman, and I would each buy a bag of chips (French Fries) from the Fish-and-Chip shop at the bottom of his road. (FYI I think a bag of chips used to cost us a sixpenny piece – and these were "old pennies" before the country went to a decimal currency in 1971.) Our favorite time of the year was the fall when there was a chill in the air. Jeremy and I would take our bags of chips, walk up the road to his house, and – using various finger- and toe-holds and well placed vines – climb onto the flat roof of his garage. Then we would laze on our backs munching on our chips while we looked at the stars and talked about Life, the Universe, and Everything . The point is that we knew that there are billions of stars in our Milky Way galaxy (the estimate keeps increasing, but let's assume that there are several hundred billion stars). We also knew that there are billions of galaxies in the universe (again, the estimate keeps on going up, but it's now known that there are hundreds of billions, and perhaps trillions, of galaxies in the observable universe). We also fully believed in the possibility of alien life in general and – more specifically – intelligent alien life. In fact, I actually remember our wondering if there were the alien equivalents of Boy Scouts and – if so – if two of them were lying on their backs (or whatever), eating their chips (or whatever), pointing their tentacles (or whatever) in our general direction, and asking much the same questions; that is, we conceived them as wondering if alien life – which would be us as far as they were concerned – existed and so on and so forth. As I've grown older and been exposed to much more detailed information than existed in those days, I've come to understand that life is almost certainly rampant throughout the universe. We know that the basic building blocks of life, in the form of relatively complex molecules and amino acids and suchlike, have been found in meteorites and detected in gas clouds in space. And books like Wetware: A Computer in Every Living Cell by Dennis Bray explain how the first cells could have formed on Earth, how the eye could have evolved, and... more mind-bogglingly wonderful things than I can possibly discuss here (I would class this book as one of the "all-time great reads"). Thus, until recently, based on the fact that there are so many galaxies and stars, and that life seems to be poised to breakout given even the slightest encouragement, if you had asked me about the possibility of intelligent life in general – and intelligent life leading to a technological civilization with which we could possibly establish communication (assuming we were close enough spatially and temporally) – I would have said that I was a total believer. And then I read Alone in the Universe: Why Our Planet is Unique by John Gribbin. I have to tell you that this is a "bit of a downer", because Gribbin makes a very compelling case for the fact that we may well be alone (as an intelligent technological race) in the universe. The blurb on the back cover summarizes this book nicely and reads as follows: Are there other planets in the galaxy that can sustain life? Almost certainly so. Are any of them likely to be populated by intelligent beings? According to John Gribbin, one of today's most popular science writers, definitely not. In this fascinating and intriguing new book, Gribbin argues that the very existence of intelligent life anywhere in the cosmos is, from an astrophysicist's point of view, almost a miracle. So why is there intelligent life on Earth and (seemingly) nowhere else? What happened to make this planet special? Taking us back billions of years to a time before Earth even existed; Gribben lets you experience the series of extraordinary cosmic events that were responsible for our unique form of life within the Milky Way galaxy. Chapter-by-chapter, Gribbin walks us through topics like What's so special about our place in the Milky Way? What's so special about the Sun? What's so special about the solar system? What's so special about the Earth? What's so special about the Cambrian Explosion? and What's so special about us? Over the years, I've read all sorts of books that explore different facets of Life, the Universe, and Everything , but this book (a) taught me all sorts of things I didn't know and (b) tied all sorts of things together to give me a completely different perspective. Apart from anything else, I have long been aware that our continued presence in the universe is tenuous at best. There are all sorts of possible extinction level events that could take us out of the picture, such as a giant asteroid striking the Earth or our creating an artificial self-aware intelligence that subsequently decides that we are either a threat or simply surplus to its requirements and decides to help us exit stage left. The thing is that, although I think we as a race are precious and have a lot to offer, before reading Alone in the Universe I tended to be somewhat sanguine about things and to take the view that if anything did happen to wipe us out, at least there would be other intelligent species out there to carry on the good fight. But now that I have read Alone in the Universe , I'm really not so sure. It may well be that we are It , which makes it all the more important that we take better care of ourselves and the Earth (I, for one, am going to start exercising again as soon as I post this column). The bottom line is that I thoroughly enjoyed this book. It taught me lots of nuggets of knowledge and tidbits of trivia and made me look at things from a completely different angle; it's given me a whole lot of things to think about (and to worry about); and I would heartily recommend it.

I just finished reading this book The First Three Minutes: A Modern View of the Origin of the Universe by (why I was reading it is a long story for a different time and place). It is by Steven Weinberg. Although the book avoids any equations as it tries to put the details of the Big Bang origin theory "within the grasp of the general reader", it was still a pretty tough read. I think I grasped about half of the specifics, especially as the roster of those elusive sub-atomic particles to keep in mind kept growing. I'm not here to complain, since I did learn quite a bit. The basic premise of the book—and the theory it describes—is a detailed and complex exercise using two tracks: combining observations and data from distant sources (which, of course, represent a look "back in time") along with backwards extrapolation of the universe around us now, to figure out what must have been "back then" to get us to our present state of matter and energy. It's like looking at a hole in a target and determining where the bullet that made it came from, based on the hole's angle and size. It can be done, but it's not easy, and there are many sources of error—both assumptions and measurement—which affect the accuracy of the answer. I won't attempt to summarize the book. Let's just say that those first moments—I hesitate to call them milliseconds, seconds, minutes, or any designations like that—were pretty bizarre. The temperature was 100,000 million Kelvin (yes, 10 11 K) and most of the particles were electrons, positrons, and the massless photons, neutrinos, and antineutrinos; atoms as we now have them had not yet formed. If that's not enough for you, the universe was highly concentrated, with an energy density of 21 x 10 44 electron volts/liter, equivalent to a mass density of around 4 x 10 9 kilograms/liter. I am reading this, and while Dr. Weinberg is a pretty smart fellow (co-winner of the Nobel Prize in 1979 for work on the unification of the weak force and electromagnetic interaction between elementary particles, see here ), but I am still wondering: can this be true? Are we getting a little ahead of ourselves, by extrapolating back to time t=0 while making many unprovable assumptions, even though they may seem logical or sensible, and are even consistent with our present understanding? I also thought about something I read in a book by another brilliant physicist, Richard Feynman (although I don't remember which one of his many it was). He made some points that have stuck with me for many years, along these lines: Is it meaningful or make sense at all to talk about units of time, such as seconds, in the era of the Big Bang? How was this time measured, or even measurable, in this period? Should we even assume that the laws of physics as we know them now were the same back then in those first instants, given the unimaginable density and temperature of the energy and material of the universe? When you think about it, there's really no way to know. You can certainly make a case that under such extreme temperature and density, our "normal" laws of atomic and general physics were not yet in place, or not the way we understand them today. It's somewhat analogous to knowing that as you make water colder, yes, the motion of the atoms slows down continuously as you slide down to 0 K—but assuming that nothing special happens at 273 K (0 deg C). Yet we know that the intermolecular bonds undergo a phase change and the water goes from liquid to solid state. There are inflection points and thresholds for properties of materials; who knows what rules the subatomic particles obey are at 10 11 K and 10 9 kg/l? When I finished the book, my first thoughts were that is all quite interesting, but so what? The details of the birth of the universe have no direct impact on our work today, so what's the lesson here? But the more I thought about it (perhaps I do have too much time on my hands) I realized that engineers and scientists do have the same class of problem, although less difficult. How so? There are many times when you have a system problem where you can't directly observe the necessary points, or where you can only infer what might earlier have caused the problem based on later events and observations. You can't go back in time because the specific cause has passed, or maybe the root cause is shielded, concealed, or unobservable due to the system's design, structure, or physical setup. As a result, you have to make some assumptions and extrapolate backwards to figure out, hopefully, what really happened "back then" and "back there" to lead you to where you are now. That is our "small-bore" analogy to how an engineer's problem can have the same challenges, though on a much smaller scale, as physicists trying to work out the origins of the universe. Have you ever had to work backwards and make assumptions when you needed to unravel a problem? How did that work out?

I just finished reading Steven Weinberg's The First Three Minutes: A Modern View of the Origin of the Universe by (why I was reading it is a long story for a different time and place). Although the book avoids any equations as it tries to put the details of the Big Bang origin theory "within the grasp of the general reader", it was still a pretty tough read. I think I grasped about half of the specifics, especially as the roster of those elusive sub-atomic particles to keep in mind kept growing. I'm not here to complain, since I did learn quite a bit. The basic premise of the book—and the theory it describes—is a detailed and complex exercise using two tracks: combining observations and data from distant sources (which, of course, represent a look "back in time") along with backwards extrapolation of the universe around us now, to figure out what must have been "back then" to get us to our present state of matter and energy. It's like looking at a hole in a target and determining where the bullet that made it came from, based on the hole's angle and size. It can be done, but it's not easy, and there are many sources of error—both assumptions and measurement—which affect the accuracy of the answer. I won't attempt to summarize the book. Let's just say that those first moments—I hesitate to call them milliseconds, seconds, minutes, or any designations like that—were pretty bizarre. The temperature was 100,000 million Kelvin (yes, 10 11 K) and most of the particles were electrons, positrons, and the massless photons, neutrinos, and antineutrinos; atoms as we now have them had not yet formed. If that's not enough for you, the universe was highly concentrated, with an energy density of 21 x 10 44 electron volts/liter, equivalent to a mass density of around 4 x 10 9 kilograms/liter. I am reading this, and while Dr. Weinberg is a pretty smart fellow (co-winner of the Nobel Prize in 1979 for work on the unification of the weak force and electromagnetic interaction between elementary particles, see here ), but I am still wondering: can this be true? Are we getting a little ahead of ourselves, by extrapolating back to time t=0 while making many unprovable assumptions, even though they may seem logical or sensible, and are even consistent with our present understanding? I also thought about something I read in a book by another brilliant physicist, Richard Feynman (although I don't remember which one of his many it was). He made some points that have stuck with me for many years, along these lines: Is it meaningful or make sense at all to talk about units of time, such as seconds, in the era of the Big Bang? How was this time measured, or even measurable, in this period? Should we even assume that the laws of physics as we know them now were the same back then in those first instants, given the unimaginable density and temperature of the energy and material of the universe? When you think about it, there's really no way to know. You can certainly make a case that under such extreme temperature and density, our "normal" laws of atomic and general physics were not yet in place, or not the way we understand them today. It's somewhat analogous to knowing that as you make water colder, yes, the motion of the atoms slows down continuously as you slide down to 0 K—but assuming that nothing special happens at 273 K (0 deg C). Yet we know that the intermolecular bonds undergo a phase change and the water goes from liquid to solid state. There are inflection points and thresholds for properties of materials; who knows what rules the subatomic particles obey are at 10 11 K and 10 9 kg/l? When I finished the book, my first thoughts were that is all quite interesting, but so what? The details of the birth of the universe have no direct impact on our work today, so what's the lesson here? But the more I thought about it (perhaps I do have too much time on my hands) I realized that engineers and scientists do have the same class of problem, although less difficult. How so? There are many times when you have a system problem where you can't directly observe the necessary points, or where you can only infer what might earlier have caused the problem based on later events and observations. You can't go back in time because the specific cause has passed, or maybe the root cause is shielded, concealed, or unobservable due to the system's design, structure, or physical setup. As a result, you have to make some assumptions and extrapolate backwards to figure out, hopefully, what really happened "back then" and "back there" to lead you to where you are now. That is our "small-bore" analogy to how an engineer's problem can have the same challenges, though on a much smaller scale, as physicists trying to work out the origins of the universe. Have you ever had to work backwards and make assumptions when you needed to unravel a problem? How did that work out?