Galactic Interactions

Shakepseare & Relativity in-world this weekend

Posted on May 28th, 2009 — permalink

I’m going to be busy this weekend with a public outreach talk and some Shakespeare performances.

Saturday morning at 10AM SLT/PDT, I’ll be giving a talk entitled Time dilation and simultaneity in Special Relativity. This is part of the regular “Dr. Knop Talks Astronomy” public-outreach talk series given by MICA. If you’re curious about just why it is that moving clocks run slow in special relativity, drop by and I’ll explain it. You don’t need any math to understand the basics; with just early high-school algebra (the Pythagorean Theorem), you can even understand the equation for how slow clocks run. The talk will be at the MICA Large Amphitheater (StellaNova (213, 210, 32)).

Then, Saturday and Sunday from 4PM-5PM, Avatar Repertory Theater will be performing scenes from several Shakespeare plays in our “Shakespeare at the Pavilion” performance, in association with the San Diego City sim. We’ll do scenes from Twelfth Night, Julius Caesar, Hamlet, As You Like It, and A Midsummer Night’s Dream. See the A.R.T. site for more information.

I remind everybody that a Second Life account is free. Here is one place you can register for an account— that’s the registration portal for the SciLands, a contiguous group of regions of which MICA is a member. That will take you to the SciLands’ orientation spot. Both of the events above will use Second Life Voice, but you don’t need a microphone or a headset; you’ll just need your standard computer speakers to hear what’s going on. There are Second Life viewer applications for Linux, MacOs, and Windows.

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When Stars Collide

Posted on May 26th, 2009 — permalink

When I’ve given talks about colliding galaxies, I always start out by pointing that that the stars within a galaxy basically never collide with each other. This is, of course, an oversimplification….

You may have seen a “scale model” of the Solar System. It gives you a sense of how amazingly spread out things are… especially after you’ve made the hike to get to Saturn, never mind Uranus, Neptune, or the Kuiper Belt. But you never see a scale model of the nearby stars. Why? because things are even more amazingly spread out. Suppose I wanted to make such a scale model, and, here in Nashville, TN, I used a tennis ball to represent the Sun. To represent the nearest star, α Centauri, I’d need another tennis ball that is in New York City. Stars are really, really far apart from each other. Our galaxy is mostly empty space. (Well, actually it’s mostly dark matter, but within the disk of the galaxy, the mass density is more stars than dark matter. And, between the stars, there is interstellar gas, but the density of that gas is much lower than the density of gas in the best vacuum chamber we’ve built on Earth.)

However, there are places where this isn’t strictly true. We see some stars in globular clusters that are more massive than stars that have any business still being around in that globular cluster. (That is, globular cluster stars were all formed 11-13 billion years ago. Stars with higher mass have shorter lifetimes, so any star above a certain mass cutoff isn’t seen in a globular cluster.) One very likely explanation for this is that these stars are the result of a merger between two lower-mass stars.

It may also be possible in some very rich young clusters of stars that stars may collide with each other before the cluster disperses. The black hole at the center of our galaxy may very rarely “eat” a star. (No, we haven’t seen this happen.)

Last week, Jamie Lombardi of Allegheny college gave a seminar in Second Life as part of the MICA professional seminar series entitled “The Hydrodynamics of Runaway Collisions.” At the very beginning of the talk, he had to clarify that he was in fact talking about colliding stars. I give a lot of public-outreach astronomy talks for MICA (a different series, obviously, from the serious of professional seminars), and I have given a couple of talks about colliding galaxies. My own history as an astronomer leads me to think “collisions” to mean “between galaxies”– and the hydrodynamics, then, must be referring to the gas processes that might, say, feed an AGN.

However, cool things can happen when three stars have a close enough pass that their envelopes start to spill on to each other. Sometimes, two of the stars will merge (while the third one in the collision is ejected). Some of the gas is lost, but much of it stays behind in a more massive star. The timescale for these collisions is short enough that the stars will not evolve appreciably during the collision, so this may well be a way that you can make a star that’s more massive than what would naturally form out of star formation nowadays— especially if you can chain together several collisions. What Jamie was talking about, of course, probably only applies in very young, very rich clusters. The globular clusters in our Galaxy today are too old to have the kind of massive stars that Jamie was focusing on in his talk, and most of the star forming clusters nowadays have several orders of magnitude fewer stars than globular clusters do. But, globular clusters were once young….

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This Saturday at 10AM PDT in SL : “How We Know Dark Matter Exists”

Posted on April 29th, 2009 — permalink

As part of my regular Dr. Knop Talks Astronomy series of public astronomy lectures in Second Life, this coming Saturday I’ll be talking about how we know that Dark Matter really exists.

The talk will be at the Large Ampitheater on StellaNova. Note that a Second Life account is completely free! You can register for an account here. This is the “SciLands” entry portal, which will put you at the SciLands own orientation island. (StellaNova, the sim of MICA, is part of the SciLands.)

Here’s a description of the talk:

Modern cosmology tells us that the majority of the Universe is made up of stuff whose nature is largely unknown to us. Two thirds of it is Dark Energy; most of the rest is Dark Matter, the subject of this talk. Dark Matter interacts with normal matter through gravity, but otherwise it interacts hardly at all. Yet, we have very high confidence that this mysterious Dark Matter really does exist. Because it doesn’t interact with light, we haven’t seen it glowing, nor have we observed it absorbing background light as we’ve seen with dust clouds. All of the evidence we have for Dark Matter comes from its gravitational interaction with other matter, and with light. Yet, this evidence is extremely compelling. In this talk, I will attempt to convince you that there is no reasonable doubt that Dark Matter exists.

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Obama’s speech to the National Acaemy, my failure at my calling, and bad timing

Posted on April 28th, 2009 — permalink

It is a source of continual angst to me that I’m not teaching college physics at a small college.  It’s my calling, it’s what I’m supposed to be doing.  I sort of made a mistake by going to a research University (that really wanted to be even more of a research University, and was transitioning away from a balance in valuing teaching), but at the time it was the only job offer I had.  If you want to be faculty in physics and astronomy, you’re lucky to get in in the first place….  I would have been happy if I could have kept that job.  Alas, I failed, repeatedly, to get NFS (National Science Foundation) funding.  I tried reinventing my research program in an attempt to make something that would better match the preconception of the funding agencies.  Ironically, this was away from Dark Energy.  However, I was the only professor at my institution who was part of a large collaboration, and funding agencies aren’t interested in that.  Indeed, astronomy panels (at least 7 or so years ago) were suspicious of large collaborations in general.  But, still, no luck.  And, in my last few years, the knowledge (confirmed repeatedly by my department chair) that no NFS funding meant zero chance for tenure begin to weigh more and more heavily on me, and I became more and more dispirited, which made it increasingly difficult to produce any papers and to get good proposals written.  I was in a death spiral.

A year before I left Vanderbilt, I applied for jobs at small colleges, and got several interviews.  I did get one offer, but sadly, for family reasons, I wasn’t able to take the job.  The next year, I applied again, but only got a couple of phone calls, no actual interviews.  Now that I’m out, barring some particularly interesting angle, there’s very little chance of my being able to get back in.  There are just too many young hotshots out there with solid research records, no gap, and who aren’t already over 40.  This isn’t to say it’s inconceivable, but I’ve been on search committees, and I know what happens when they see somebody who’s more than 6 years in and not a superstar.

I can’t help but wonder, though, if things might have been different if the economy had crashed several years earlier, and if we didn’t have a president openly hostile to actual science in the white house.  In a speech to the National Academies, Obama announced that there’s going to be a huge increase in the budget for the NSF.  Mind you, only 1 in 6 grants were being funded, so even if it goes to 1 in 3 (which I doubt will really happen, because assuredly some of that NFS doubling will go to various big projects and other “rich get richer” sorts of things), it’s still difficult, you still spend a lot of your creative effort banging your head against thew all.  So, I might have had exactly the same outcome.  However, when grants were turned down, sometimes NFS program officers could only say they didn’t know what to say, because money was so tight; in previous years, they might have tried to help people applying figure out how to better tune their grants.  At 1 in 6, it was a complete crap shoot.

I can’t help but wonder if it might have been different.  If I was, in part, the victim of bad timing.

“A man is not old until regrets take the place of dreams.” –John Barrymore

The fact that I’m 40 doesn’t so much make me feel old.  The fact that I’m 40 and not spending my primary full-time-job creative effort on physics and astronomy, together with a realistic assessment that I’ll be able to get back into the sort of faculty job that I want, makes me realize that many (not all) of my primary dreams have in fact been replaced by regrets.

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This Saturday : “The Discovery of the Accelerating Universe” in Second Life

Posted on April 1st, 2009 — permalink

“Dr. Knop Talks Astronomy”, in association with MICA (www.mica-vw.org)

Saturday, April 4, 10AM SLT

http://slurl.com/secondlife/StellaNova/213/210/32

The Discovery of the Accelerating Universe

In 1998, two teams of astronomers observing supernovae discovered that the expansion of the Universe is accelerating. The speaker, Dr. Knop, was on one of the two teams, working with Saul Perlmutter. In this talk, I will describe just how it is that you can measure the expansion history of the Universe by observing distant exploding stars, and what surprising things we saw in our results that indicated to us that the expansion of the Universe was in fact accelerating. At the end, I’ll briefly mention some things about “dark energy,” the mysterious substance that is causing this surprising universal acceleration.

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Astronomical References in Shakespeare

Posted on February 14th, 2009 — permalink

Thanks to Brian Cooksey for the shout out last time I was a contributor to the 365 Days of Astronomy Podcast. I’ve also done today’s podcast, all about astronomical references in Shakespeare’s tragedies… starting with Romeo & Juliet, what with it being Valentines day and all. Go and listen to the podcast!

For your viewing pleasure, I’ve also got a transcript of the podcast here:

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“Science at Play” — a play writing workshop in Second Life

Posted on January 19th, 2009 — permalink

Starting today at 2PM PST, I and others will be leading playwriting workshops at the Kira Cafe. The genesis of this idea came from Piet Hutt, one of the directors of the Kira Institute, after I gave an informal talk about what it was like to perform live theater in Second Life. As the mission of Kira is to talk about science in context, he thought it would be neat if we were to try putting on some plays related to science. One recent example is the play “Copenhagen” by Michael Frayn, although myself I am more familiar with “Hapgood” and “Arcadia” by Tom Stoppard.

The discussion evolved, and we decided that perhaps it would be interesting to think about getting people together to talk about writing plays, perhaps very short plays, that explore things related to science— and that are written from the beginning understanding both the advantages and the limitations that come from performing theater in Second Life (as opposed to live on stage).

If this sounds interesting to you, feel free to drop by the Kira Cafe today, and over the next few weeks on Mondays at 2PM SLT, to join us. The Kira Cafe can be found in Second Life at BaikUn (198, 76, 99).

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The Big Bang and Evolution : when does a theory evolve so much that it deserves a new name

Posted on November 21st, 2008 — permalink

I am currently visiting Colgate University, giving a physics colloquium about dark energy. I’m hosted by my friend Jeff Bary (who’s a first year professor there). Yesterday evening, his class gave presentations about discoveries that they’d researched. A few of the talks touched on the Big Bang. Afterwards, I was sitting around musing with Jeff and the departmental chair, Thomas Balonek. Thom was saying that it’s disingenuous for us to claim that we’re still talking about the Big Bang as it being the same theory that we had all those decades ago. What with the introduction of inflation, cold dark matter, dark energy, it’s changed so much that really it’s not entirely the same theory any more. I argued that the basic picture is the same– the Universe expanded from a very hot, very dense state to its current form– that it warrants having the same name.

I then asked the question: which theory has evolved more, the Big Bang or Biological Evolution? To point a finer point on it, let’s go back to the (say) 1950’s or early 1960’s, when people were arguing about Big Bang vs. Steady State cosmology, before the discovery of the Cosmic Microwave Background, well before the introduction of inflation to solve the flatness and horizon problems. Take what people were talking about then as the Big Bang, and compare to what we talk about today. Has that changed more or less than the Theory of Evolution has changed from what Darwin originally envisaged when he wrote the Origin of the Species?

To be sure, the theory of Evolution is better understood and understood in better detail than the Big Bang theory. They both share the feature that they are theories describing the evolution of a system, not it’s origin (although both the name of the cosmological theory, and the title of the work that started Evolution, both would seem to indicate that they do). We know a whole lot more about both today than we did then. Both have features today that people in the early days couldn’t have anticipated. (I understand the cosmology better, of course, but know, for instance, that DNA and the genetics gives us an actual mechanism for Darwin’s Evolution.)

So, what do you think? Which one has changed more? And is either theory similar enough to what was originally proposed that it deserves the same name, or should we have changed the name by now?

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Popular Astronomy Talk in Second Life, Friday 8AM PDT (11AM EDT)

Posted on October 9th, 2008 — permalink

I’ll be giving a talk entitled: “We Are Starstuff: the Cosmic Origins of the Chemical Elements” as a part of the MICA public talks series. The talk will be at the Galaxy Dome in Spaceport Bravo.

Remember, a Second Life account is free!

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Randall Munroe and the Size of the Observable Universe

Posted on October 4th, 2008 — permalink

Randall Munroe of the fabulous webcomic xkcd has a great logarithmic height poster showing the size of everything from folks all the way up through the edge of the Solar System, on to the radius of the observable Universe. As a logarithmic plot, each gap of the same size vertically on the plot represents a doubling of the distance from the surface of the Earth; this is why he can show things of such vastly different scales as people and the whole Universe in the same plot.

But, wait, I thought you cosmologists kept saying that the Universe was infinite! How can this picture show the whole Universe then?

It doesn’t… it shows the observable Universe. Because the Universe is only 14 billion years old, and the speed of light is finite, we can only see things that are as far away as light has had time to reach us from. There is more Universe beyond that, but the light hasn’t reached us from it yet; the part of the Universe beyond our horizon is not the observable Universe.

But wait… if the Universe is only 14 billion years old, then, we should only be able to see things that are 14 billion light-years away… yet the xkcd pictures says the top of the Universe is 46 billion years away. What’s up with that?

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