Relativity
drorzel | February 27, 2011A few lines of dialogue that I wrote today:
"So, the treats I eat represent the matter falling into the black hole, while my poop--"
"You are not coming to my class and pooping to demonstrate Hawking radiation. Don't even think about it."
"I guess that means you don't want to hear my take on the black hole information paradox, then?"
My life is very strange.
drorzel | February 16, 2011Sean Carroll and Brad DeLong have each recently asserted that relativity is easier to understand than quantum mechanics. Both quote Feynman saying that nobody understands quantum mechanics, but Sean gives more detail:
"Hardness" is not a property that inheres in a theory itself; it's a statement about the relationship between the theory and the human beings trying to understand it. Quantum mechanics and relativity both seem hard because they feature phenomena that are outside the everyday understanding we grow up with. But for relativity, it's really just a matter of re-arranging the concepts…
drorzel | January 27, 2011I probably ought to get a start on the big pile of grading I have waiting for me, but I just finished a draft of the problematic Chapter 7, on E=mc2, so I'm going to celebrate a little by blogging about that.
One thing that caught my eye in the not-entirely-successful chapter on momentum and energy in An Illustrated Guide to Relativity was a slightly rant-y paragraph on how it's misleading to talk about the energy released in nuclear reactions as being the conversion of mass into energy, because what's really involved is just the release of energy due to the strong force. It struck me as…
drorzel | January 27, 2011Subtitled "Understanding Einstein's Relativity," David Mermin's It's About Time is another book (like An Illustrated Guide to Relativity) that grew out of a non-majors course on physics that Mermin offers at Cornell. It's also an almost-forty-years-later update of an earlier book he wrote on the same subject. And it's been a really good resource for writing the book-in-progress, which I ought to repay by reviewing it here.
Like the Illustrated Guide, this is a book that aims to teach students something about how relativistic kinematics actually works. Unlike the Illustrated Guide though, this…
drorzel | January 10, 2011I'm always a little hesitant to post reviews of books that I'm using as reference sources when I'm writing something, because it feels a little like recommending that you skip past my book and go to my sources instead. This is, of course, completely irrational, because however much I my use a given book as a resource, what I'm writing is going to cover a different set of topics, with a slightly different slant. And since the folks at Cambridge University Press were kind enough to send me a review copy of Tatsu Takeuchi's An Illustrated Guide to Relativity, I really kind of owe it to them to,…
drorzel | January 6, 2011I've reached a point in the book-in-progress where I find myself needing to talk a little about particle physics. As this is very much not my field, this quickly led to a situation where the dog asked a question I can't answer. But, hey, that's why I have a blog with lots of smart readers...
The question is this:
What are all these extra particles for?
Or, to put it in slightly more physics-y terms: The Standard Model contains twelve material particles: six leptons (the electron, muon, and tau, plus associated neutrinos) and six quarks (up-down, strange-charm, top-bottom). The observable…
drorzel | December 10, 2010I'm currently working on a book about relativity, but I still spend a fair amount of time thinking about quantum issues. A lot of this won't make it into the book, because I can't assume people will have read How to Teach Physics to Your Dog before reading whatever the relativity book's title ends up being, and because explaining the quantum background would take too much space. But then, that's what I have a blog for...
Anyway, the section I was working on yesterday concerned causality and faster-than-light travel, specifically the fact that they don't play well together. Given Tuesday's…
drorzel | November 25, 2010It's Thanksgiving here in the US, so blogging will be light to nonexistent. For the sake of those looking for a quick escape from the chaos of a family gathering, or, you know, those poor benighted souls in other countries for whom this is just another Thursday, here's a thematically appropriate poll about science:
What are you most thankful for?online surveys
Have a great holiday/ Thursday.
drorzel | November 24, 2010Given that I'm currently working on a book about relativity, I'm spending a lot of time idly thinking about various relativistic effects. Many of these won't end up in the final book, but they're fun to think about.
One thing that occurred to be earlier, while thinking about something else entirely, is the Doppler shift. In particular, I was thinking about the detection of planets around other stars, which is often done using the Doppler shift due to the orbiting planet's tug on its star. If the orbit is more or less aligned with our line of sight to the star, then the star wobbles back and…
drorzel | November 16, 2010Fall term classes ended yesterday, officially-- my last class was Friday-- so I'm shifting over to spend more time working on the sequel to How to Teach Physics to Your Dog, which involves talking to Emmy about relativity. Progress has been slower than last time, largely because the previous book was written while I was on sabbatical and before SteelyKid was born. But there's also a structural issue that's giving me some problems.
This is partly a matter of familiarity with the material-- I'm a low-energy physicist, so I've never needed to worry all that much about relativity. A bigger issue…
drorzel | November 12, 2010As mentioned in yesterday's post on ion trapping, a month or so back Dave Wineland's group at NIST published a paper in Science on using ultra-precise atomic clocks to measure relativistic effects. If you don't have a subscription to Science, you can get the paper for free from the Time and Frequency Division database, because you can't copyright work done for the US government.
This paper generated quite a bit of interest when it came out, because it demonstrates the time-slowing effects of relativity without any need for exotic objects like black holes or particle accelerators-- they deal…
drorzel | October 18, 2010As you may or may not be aware, we are once again in the middle of a DonorsChoose fundraiser to support public school students and teachers. The good news is, the Uncertain Principles entry for the 2010 Challenge is in second place among ScienceBlogs blogs with $373 in donations thus far; the bad news it that more than half of that money is from the initial contribution I made when I set the challenge up.
We've done much better than this in the past, but I realize these are tough economic times, and people may not have as much disposable cash to give to charity. I was thinking, though, about…
drorzel | September 8, 2010The theory of relativity takes its name from a very simple and appealing idea: that the laws of physics should look the same to moving observers as to stationary ones. "Laws of physics" here includes Maxwell's equations for electricity and magnetism, which necessarily means that moving observers must see the same speed of light as stationary observers (Einstein included the constancy of the speed of light as a second postulate in his original relativity paper, but it's redundant-- the constancy of the speed of light is a direct consequence of the principle of relativity). This leads directly…
drorzel | September 2, 2010"Hey, dude, whatcha doin'?"
"Signing these contracts. I'm not sure why they need four copies, but they do."
"Contracts for what?"
"The new book. Remmeber, the one we've been talking about these last few weeks? Sequel-of-sorts to How to Teach Physics to Your Dog? About relativity?"
"Oh, yeah, that's right! We're doing another book! Where do I sign?"
"What do you mean, 'Where do I sign?' You're a dog."
"I could, you know, put a paw print on the line, or something."
"I suppose you could, but it wouldn't be legally binding. Dogs aren't allowed to sign contracts."
"You know that's horribly…
drorzel | August 12, 2010The problem with writing about fake physics is that once you start, it's hard to stop. And there's always something new and disreputable to find, such as this hideous bit of scammery. As I said in How to Teach Physics to Your Dog, if quantum physics really allowed you to amass vast wealth just by wanting it, Dave Wineland's publications wouldn't need to acknowledge funding from a handful of acronyms-- he'd be able to bankroll his own research out of his personal fortune..
Quantum physics is not magic. It allows many things that seem weird and counterintuitive, but those effects are very…
drorzel | June 5, 2010Since I was going to be down here anyway to sign books at the World Science Festival Street Fair, Kate and I decided to catch one of the Saturday events at the Festival. It was hard to choose, but we opted for the program on Hidden Dimensions: Exploring Hyperspace (Live coverage was here, but the video is off), because it was a physics-based topic, and because I wrote a guest-blog post on the topic for them.
(No, we didn't go to the controversial "Science and Faith" panel, opting instead to have a very nice Caribbean dinner at Negril Village, just around the corner. I'll take excellent…
drorzel | June 1, 2010While I mostly restricted myself to watching invited talks at DAMOP last week, I did check out a few ten-minute talks, one of which ended up being just about the coolest thing I saw at the meeting. Specifically, the Friday afternoon talk on observing relativity with atomic clocks by Chin-Wen Chou of the Time and Frequency Division at NIST in Boulder.
The real technical advance is in a recent paper in Physical Review Letters (available for free via the Time and Frequency Publications Database, because government research isn't subject to copyright): they have made improvements to their atomic…
drorzel | May 1, 2010The APS now gives out an Abraham Pais Prize for History of Physics, which gives you some idea of how influential his work was, in particular "Subtle Is the Lord..." The Science and Life of Albert Einstein, which won prizes and sits in a prominent position on the bookshelves of many physicists. Like a lot of influential works, though, it's kind of odd to read it much later than some of the works it has influenced.
The ordering of the subtitle is very deliberate, and accurate. This is first and foremost a book about Einstein's science, with a biographical structure and occasional biographical…
drorzel | April 12, 2010What's the application? LIGO stands for Laser Interferometer Graviitational Wave Observatory, because (astro)physicists feel free to drop inconvenient words when making up cute acronyms. This is an experiment to look for disturbances in space-time caused by massive objects, which would manifest as a slight stretching and compression of space itself.
What problem(s) is it the solution to? 1) "Can we directly observe the gravitational waves that are predicted by the equations of General Relativity?" 2) "Can we detect things like colliding black holes, because that would be awesome!"
How does it…
drorzel | April 8, 2010Via Twitter, Michael Barton is looking for some good books about physics. I was Twitter-less for a few days around the period of his request, and this is a more-than-140-characters topic if ever there was one, so I'm turning it into a blog post.
The reason for the request is that he's going to be working as an intern at the Einstein exhibit when it visits Portland, which makes this a little tricky, as relativity is not an area I've read a lot of popular books in (yet-- that's changing). That will make this a little more sparse than it might be in some other fields.
There's also an essential…