Archive for the 'Physics' Category

A 10-Year-Old Asks about Black Holes

I have a 10-year-old cousin who is very curious about the world, and physics in particular.  When his mother sent me two very interesting questions that he asked about black holes, I had fun coming up with some answers for him.  His questions and my answers are reproduced below. (Yes, some of the language isn’t quite as precise as it should be, but I intentionally glossed over a few details. Hopefully I didn’t say anything wrong as a result.)

If a black hole “sucked in” only photons, would it increase in mass?

Photons “die” when they interact with something, but if they do die, then what are they interacting with in the black hole?

These are two great questions, and I had fun coming up with answers to them. I gave a short answer, but any good physics question brings up a lot of related ideas, so I also put a longer answer that brings up some other ideas.

Short answer:
Yes. Einstein taught us that energy and mass are two aspects of the same thing. Even though the photons are massless on their own, their energy can increase the mass of the black hole when they are absorbed. The event horizon prevents any information from escaping a black hole, so we can’t know exactly what the photon interacts with.

Longer answer: Continue reading ‘A 10-Year-Old Asks about Black Holes’

Buried by Papers

A recent article in The Chronicle of Higher Education blames the increased number of published scientific articles on “an avalanche of low-quality research,” and claims that this avalanche is damaging academia. I agree that there are certainly problems associated with the large volume of published research, but is it truly the crisis that the article claims?

It becomes more difficult finding articles for a particular area of interest, as the arXiv feed for the limited area of high energy phenomenology dumps 20+ articles into my RSS reader every evening. This is not entirely unmanageable, as I mostly scan abstracts for anything related to my current work, and ignore the rest.  Plus, it is 2010, and a search function can turn up a paper on any topic I desire.  However, the number of articles makes it more difficult to keep abreast of more subfields, and tangentially-related, though helpful, articles in other fields go unnoticed.  Cross-pollination of ideas has been essential throughout the history of science, but it is more difficult in this era of increased specialization.  The increased number of papers in all areas can’t be helping matters.

Continue reading ‘Buried by Papers’

Talent is a Process

With the semester over, I was able to dive into a couple of books that I had been waiting to read.  On the surface, they seem very different in subject matter, but reading them in succession allowed for some interesting insights.

The first book that I read was David Shenk’s The Genius in All of Us, whose thesis is that the usual conception of talent is incorrect.  Rather than being innate, talents are developed over years of sustained practice. (The canonical 10,000 hours of practice to become an expert, popularized by Malcolm Gladwell’s Outliers.)

The book, which is shorter than it looks due to the notes that fill about half of the volume, covers a variety of interesting topics to help debunk the notion that talents and other personal qualities are inborn.  The author describes a new understanding of genetics by throwing out the classic “nature vs. nurture” distinction, and arguing that the two are inextricably linked through the interaction of genes with their environment.  He goes too far with this in the final chapter, discussing the impact of epigenetic material (stuff other than DNA) on gene expression.  While there seems to be some credible and recent research on the effects of lifestyle on heredity, his assertion that “we may well be able to improve the conditions for our grandchildren by putting our young children through intellectual calisthenics now” seems to me to be a gross overstatement of the research.  Although much of the rest of the book is couched in this genetic argument, it isn’t dependent on his perhaps flawed understanding of the biology.

To determine the true sources of talent, Shenk discusses everything from the history of intelligence testing and “gifted” designations to the reasons for the athletic dominance of certain ethnic groups in their chosen sport.  (It is interesting to note that people used to wonder what genetic gifts allowed Jewish players to dominate basketball in the 30s and 40s, in much the same way that people discuss black players today.)  However, it seems that the most important factor for the development of talent is still the same: deliberate practice.

Deliberate practice requires more than just hard work, and it is not achieved by simply “putting in your 10,000 hours,” although both hard work and large amounts of time are certainly required.  Instead, it involves pushing beyond one’s current skill level to the point of failure, then picking up the pieces and trying again.  This type of practice is not necessarily enjoyable, but pushing beyond current limits is the only way to improve.  The practice activities have to be focused on particular aspects of the performance, with appropriate refinement and feedback for improvement.

It’s easy to imagine this deliberate practice as applied by a musician: seeking out more challenging pieces of music to play, focusing on the most technical measures, playing them repeatedly in solo practice, and later for a demanding instructor.  Or we can imagine the chess student, poring over volumes of opening and closing strategies, learning the tricks of the masters through solo study of their games, before testing those skills against ever tougher competition.

And of course, we can see this playing out with athletes, as it did in the other book I read to start my summer: Chris Ballard’s The Art of a Beautiful Game, which has chapters that discuss several of the basic components of basketball.  Though the book is wonderfully written, and a great read for any basketball fan, I couldn’t help but notice a strange battle playing out between the belief in natural athletic talent with the evidence of his descriptions of the players’ relentless practice habits.

Continue reading ‘Talent is a Process’

Liveblogging CDMS Talk from My Couch

Post-Talk UPDATE:

My take: No conclusive discovery of dark matter, but we couldn’t realistically expect that anyway.  However, there are two events that, while not definitively dark matter, can’t be ruled out either.  The announcement wasn’t earth-shattering, but it was nonetheless exciting.  It was cool for me to be in on what may be the early stages of a big and important discovery, both by watching the announcement live and by being at the institution that hosts the experiment.

My semester is over, so I’m at home, sitting on my couch, watching the CDMS talk streaming live. Here’s some of my thoughts as I watch: Continue reading ‘Liveblogging CDMS Talk from My Couch’

Rumors of the Dark Side

UPDATE: Direct link to the streaming video of the announcement.  Live blogging of the event at SLAC via JoAnne at Cosmic Variance.

You may have heard the wild rumors circulating around the physics blogosphere about the CDMS (Cryogenic Dark Matter Search) experiment taking place deep underground in an abandoned mine in northern Minnesota.  The rumor (which apparently started with this post at Resonaances) took some unusual behavior by the CDMS team, combined with the rumor of an article being published in Nature, led many to speculate that they were planning to announce detection of dark matter.

It turns out that these rumors were overly dramatic — apparently there is no Nature article, and Priscilla Cushman from the University of Minnesota has downplayed the rumors, calling them “lots of smoke and not much fire.”

However, they are still making dual announcements today at 5 o’clock EST, one at SLAC and one at Fermilab, and one will be webcast here.  So they have some sort of semi-major announcement, but that doesn’t necessarily mean a claim of detection.  It could be a significant improvement on their experimental limits, or maybe detections at a level that doesn’t allow them to make any big claims.  For more thoughts on what might be announced, and what it might mean, see this post.

And now for a little speculation of my own:

Continue reading ‘Rumors of the Dark Side’

Unsolicited Advice, Volume I

So you want to be a physicist?  Hey, me too!  While I don’t know everything there is to know about getting there, I might be farther along than you are, and have some wisdom that I’ve accrued along the way that I can impart to you, even though you never asked for it.  Hence, this series of Unsolicited Advice.  (I would be remiss if I didn’t mention the inspiration I got from Cosmic Variance.  Plus I borrowed stole the name.)

Since this is Volume I, we’ll start early: before college.

Nurture Your Interest

If you’re reading this, and you’re not yet in college, then I’m willing to bet that you got interested in physics by reading one of the many popular books on physics.  It’s a great way to get into physics (it’s the way I got into it all those years ago).  You should continue to feed that interest in any way you can: read more books, watch tv specials, and discuss what you’ve learned with anyone who will listen. Continue reading ‘Unsolicited Advice, Volume I’

Number the Stars

My uncle asked me an interesting physics-related question the other day, so I thought I’d share the question and my answer on the blog:

Q: If a trillion seconds take 30,000 years and there are three trillion stars in the universe, it would take ninety thousand years to count them at one per second. So how do we know?
Before you click through to my explanation, why not take a few minutes to think about how you might answer this?  How DO we count that which is essentially uncountable?

A hint, by way of another question: How would you count the number of grains of sand on a beach?  What’s your strategy for those “guess how many candies are in this jar” type of games?

Now, after you’ve mulled it over for a little bit, here’s my response:

Continue reading ‘Number the Stars’