A useful reminder of how profoundly strange physics can appear to the novice. The pair make some surprising points that I haven't seen expressed in quite the same way Well worth a read.
They do it well They have blazed a clear trail into forbidding territory, from the mathematical structure of space-time all the way to atom bombs, astrophysics and the origin of mass. Using clear language and a few clearly explained equations, they demystify physics' most counterintuitive claims. This is not only a painstakingly accessible explanation of spacetime, mass, particles, gravity, and a whole bunch of things that are just plain not simple.
It's also an explanation, for non-scientists, of what physicists do, and why they want to do it. What is mass? What has the speed of light got to do with energy and mass? In answering these questions, they take us to the site of one of the largest scientific experiments ever conducted.
Lying beneath the city of Geneva, straddling the Franco-Swiss boarder, is a 27 km particle accelerator, known as the Large Hadron Collider. Using this gigantic machine - which can recreate conditions in the early Universe fractions of a second after the Big Bang - Cox and Forshaw will describe the current theory behind the origin of mass. Alongside questions of energy and mass, they will consider the third, and perhaps, most intriguing element of the equation: 'c' - or the speed of light.
Why is it that the speed of light is the exchange rate? In other words, how the very fabric of our world is constructed. I would love to say that I understood every word and every example of this book, but unfortunately there were many times I felt like the concepts were far too complicated for me. I'm not an unintelligent person but my math and physics knowledge is rather old and rusty. I'll give it another 2 or 3 read through before making any firm judgements on the books.
I feel I have learned something from this book I just don't know what it is I've learned.. Jun 22, C rated it did not like it. Absolutely senseless. If he ever gets close to talking about the matter at hand, another long passage about a motorcyclist will pop up to "explain things" Look. The reason you use so many horrible analogies is because you are a horrible explainer!
Convey it the first time, don't waddle about. View all 5 comments. Feb 24, Kristin rated it really liked it. On a good day, high school physics class used to leave me feeling kind of for lack of a better word high.
This book brought back that old, familiar feeling, but in an even better way. In the end, I walked away with a much clearer understanding of Einstein's theories of special and general relativity than I ever achieved slogging through high school physics. I think our teacher must have been unable to articulate and synthesize the underlying questions that the equations sought to answer. The On a good day, high school physics class used to leave me feeling kind of for lack of a better word high.
This process is broken down into a few key steps: 1 an understanding that the speed of light is constant and therefore space and time must be "variables"; 2 the mathematical definition of spacetime and the formula needed to relate events within it; and 3 the definition of vectors in spacetime. It really is as simple as that. With an understanding of these key relationships, the elegance, beauty, and profound repercussions of the equation become crystal clear, even for those of us who never pursued physics beyond high school.
I did struggle with a few sections, particularly the bits about electromagnetism, the conservation of rotational momentum, and--I hate to say it--the "tiny physicists in elevators" analogy. In spite of my mushy understanding of those parts, I was still able to "go there" with the authors in the end.
The English major in me was a little miffed when they had a go at Murray Gell-Mann for taking his inspiration for the name "quark" from Finnegan's Wake , but otherwise I enjoyed the authors' playful, easygoing tone. You should. Enjoy Jan 13, Trevor I sometimes get notified of comments rated it liked it Shelves: science.
The best of this is how well they explain why it is not possible to travel faster than light — a really quite nice geometrical proof they offer. There are also some rather veiled digs made at Creationism and Intelligent Design which might have been better being said out loud rather than the curious sotto voce chosen here. My problem has been in trying to understand why the twin paradox happens?
The twin paradox is where you have a pair of twins and you stick one of them in a spacecraft and her brother gets left here on earth. The twin in the spacecraft zaps off at near light speed for a few years and when she returns her brother has been dead for a million years or so.
This was something nearly explained in The Fabric of the Cosmos , I think, although, not as well as is done here. In that book he talks about being in a spinning box in the middle of the universe and seeing the stars turning around you — how do you know it is you that is moving and not the stars.
When you think about it this is an amusing example, given Ptolemy, but his point is that you can tell you are moving and not the sky moving around you. If a body is experiencing an accelerating force it therefore experiences the universe differently from one that is experiencing a lesser force.
I might have missed it here, though, perhaps they did explain it. Why should accelerating make time slow down? View all 8 comments. Aug 13, Gary rated it it was amazing. Brian Cox picks a small area and gets deeply into if. I'll be reading it again.
Feb 29, Bob Nichols rated it it was ok. For those trying to nudge themselves into Einstein's world a little more, this book's title has great appeal. At some very general level, the equivalence of energy and mass can be understood, but the role of light "c" and light squared remains a challenge.
In the reverse, energy adds to mass. When energy heat is added to mass, mass For those trying to nudge themselves into Einstein's world a little more, this book's title has great appeal. When energy heat is added to mass, mass increases because energy itself has mass. At the heart of the understanding of reality, the authors make it clear that mass and energy are the same thing. They are not "disconnected entitites. This all prompts one to wonder what underlies and connects these two disconnected entities and why does conversion from one to the other occur.
Is the "pull - push" phenomena related in the sense that mass pulls energy into itself and energy seeks to escape mass? Is concentrated energy in mass gravity?
Is energy escaping mass "liberation"? If, as the authors note, the sun loses 4 million tons of mass every second in the form of radiated energy, does this mean that the earth is gaining some mass from that energy?
While the authors are quite lucid here and there, their discussion of the role of light in Einstein's equation was frustratingly opaque. Intriguingly, they seem to suggest that the speed of light is not the central factor. It is, rather, a way to measure distance in a time direction, but it is not clear how time spacetime relates to the discussion that energy and matter are equivalent.
The authors are clear that time and space are one thing, and that light years a unit of time can be used to measure distance. The authors seem to say that "c" is relevant because particles of light are massless. Elsewhere, the authors say that spacetime is like "cosmic maple syrup" with some mass Higgs field? When that happens, does light pick up mass? The authors say other things about light that are also unlcear: that there's a cosmic speed limit and that there is such a thing as "allocated speed" and a cosmic "speed quota," and that everything hurtles through spacetime at the same speed.
All of this is somehow related to the "c" in the Einstein equation. At this point, it's an achievement for the lay reader to simply identify what he or she does not understand. This is all challenging stuff. Perhaps the real problem is the inability to transfer our earth-bound perspective as that has evolved to be into these cosmic realms that operate on such vastly different scales. View all 12 comments. Dec 26, Merilee rated it it was amazing.
Superb review of latest in particle physics and spacetime. Cox explains things as clearly as possible, but I believe I will need to reread this before I could begin to explain any of it to anyone else. Aug 15, Bruno Espadana rated it really liked it Shelves: non-fiction , read , ebook , popular-science. Which, in this case, is probably most of us.
And it works. You might feel a bit lost at times, but things will fall into place. Dec 07, Blair rated it really liked it Shelves: science-physics. The challenge of writing any popular science book is that the audience has different levels of knowledge.
The author needs to choose the appropriate level of knowledge to aim the writing at. To understand my perspective, you should know my background: A long time ago I completed first year university science before switching into computers. I have since read a number of popular science books on relativity and quantum mechanics. I am presently taking on-line university physics courses to get a deeper understanding.
I have thus seen many of the ideas in this book before, and understand the mathematics. Frequently they give a hokey apology I got very tired of chalk dust and then present complex mathematics in prose.
Important steps are often skipped. I can tell you that I had to read much of this book several times, and do the math on paper to try to understand it. Following Einstein, the authors devote a chapter to this subject. This is fine with me, because I am taking my electricity course for precisely this reason.
Briefly, experiments in the 19th century showed that a moving magnetic field generates electric current, and an electric current generates a magnetic field. These mutually reinforcing forces create an energy wave, which can be described by a wave equation.
This equation gives us the speed at which the wave must travel, which turns out to be the same as the speed of light. Thus light is just another type of electromagnetic wave. Einstein assumed all movement is relative, and that the laws of physics are always the same no matter what is perceived to be doing the moving. His genius was to take this result literally, and conclude that the speed of light must always be constant no matter how it is measured.
The book claims on page 27 the speed of light is determined by the ratio of the strengths of the electric and magnetic fields. That looks like a product to me, which makes intuitive sense if they are reinforcing each other. But this stuff is over my head, so did they oversimplify, or do I have it wrong? Riding the Relativity Railroad with Pythagoras Now we get to the classic thought experiment of measuring the relative passage of time on a train from the perspective of an observer on the platform.
The passenger measures time by shining a light from one position to another one meter above it. The observer on the platform sees the light taking a longer path because the light pulse is moving along with the train. We can use the Pythagorean theorem to calculate the rate at which time appears to slow down, known as time dilation. While it is cool that such basic math can be used to derive relativity, for some reason the author chooses not to call this by its usual name of Lorentz factor.
This stuff seems to make sense when I read it, then I wake up in the middle of the night and it does not make sense any more. For example, I wondered if the above result is only true at the exact moment when the train passes the observer. No, it turns out that time dilation does not depend on the direction of motion. This is still not obvious to me, and I could have used an explanation in the book. I find it easy to get confused about which clock is running slower. I have to remind myself of what I call the Spoiled Princess Principle: You are the center of the universe.
You do not move, everything else moves relative to you. Your clock always runs at the same rate. Stretching time does not seem as strange as the fact that space contracts in front of you when you are moving. The example he gives is that if we go fast enough, we can get to the Andromeda galaxy, which is three million light years away, in fifty years of our time. Are we going faster than light?
No, my spoiled princess, remember that is only how it appears to you. How it looks to the people who sent you is coming up next. According to the equation, light, which goes the speed of light, takes no time at all to reach its destination.
It suggests that a photon traveling between you and Andromeda is everywhere on its path simultaneously. Does this not mess with causality? Is there any connection with wave nature of particles in quantum mechanics? The Imaginary Single Speed in Minkowski Space-time I was aware that travelling in space means that you also travel in time, and nothing can go faster than light. But the introduction of Minkowski space-time was a revelation. It begins with the observation we just made that distance in space changes depending on the relative motion of the observer.
This violates causality, which means this model does not work. But, of course, he knows the answer in advance. He then constructs a hyperbolic curve to demonstrate this relationship. It solves the causality problem, but visually the arithmetic is clearly false. Squaring it gives a negative number, hence the minus sign. Now it makes mathematical sense, but why did he not explain this? Anyway, the amazing result is that the speed of light is not just a limit, it is the only possible speed!
When we think we are standing still, we are zooming through the time dimension at the speed of light. When we move in space we have to slow down our movement through time to compensate. The Mystery of the Time Travelling Twins I think the twin paradox is the key mystery in special relativity.
One twin takes a round trip to Andromeda on a fast spaceship while his sister remains behind on Earth. When the travelling twin returns, he thinks it took one hundred years, but the Earth, including his sister, is now six million years older. After all the work we have done, I thought I was finally going to understand it.
But at the end we are told the whole calculation fails because it does not take into account the acceleration required to turn the spaceship around. How can he do this to me?
0コメント