Category Archives: science

Unexpectedly On YouTube

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third law jet demoI don’t know why this possibility did not occur to me before. So let me give you a heads up if you do demos in your lectures. In Physics 100 (which I taught last semester) and in Astro 100 especially, we do a lot of demos to demonstrate various physics concepts. I did a post on the Newton’s third law jet propulsion demo some time ago (linked photo right). My colleague Ed Rhodes did this same demo in his Astro 100 class.

He received an email from one of the students in the class recently saying “Congratulations, you’ve been YouTubed…”.

Apparently, one of the students in the class used his or her mobile phone camera to […] Click to continue reading this post →

Light Cone

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bulb on a stringSo imagine that you’re standing at some spot, holding a big round bulb that can shine in all directions. At a particular time, you switch on the bulb and it shines out brightly. Who has a chance to see the light from your bulb? Let’s not worry about things like buildings, cars, etc., getting in the way of the light, but just imagine it can shine free in all directions. You’ll realize that there is a whole ball of light expanding away from the bulb – light going away from you in all directions. (The edge of that ball describes what is called a sphere, a two-sphere to be precise, denoted [tex]S^2[/tex] in the trade.) The sphere expands at the speed of light. You might imagine that eventually every point in space around you would be reached by your expanding sphere (let’s stay local and not worry about the expanding universe and so forth), and you’d be right. But when? When does it get to some particular point that you might care about? As soon as it takes the light the time it takes to get there, of course. It can’t get there any sooner than that.

Let me put it another way. Your sending out the light is a particular “event”. It took […] Click to continue reading this post →

On the EDGE

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Golden-rumped Elephant ShrewEDGE here stands for “Evolutionarily Distinct and Globally Endangered” and is a term that was coined to refer specifically to certain threatened species of animal around the world. They’re not always your big marquee animals (Lions and Tigers and Bears! Oh My!), and a great deal of them will be unfamiliar to you. (I’d never encountered the Golden-Rumped Elephant Shrew before, and I’ll admit that my life has been all the poorer for not having known about it before. It’s so cute! Furthermore, it has a golden rump. What’s not to like? Apparently, it is related to an elephant, somewhat distantly. Yes, it has a trunk, but it takes more than that to detemine its relationship to elephants! Update: – Here’s a Wikipedia article on elephant shrews, which could be a starting point for finding out more. The EDGE site has a lot of information too: here.

That unfamiliarity – blissful ignorance on our part – is part of the motivation. There’s a campaign to highlight them more, and raise both funds and awareness to enable […] Click to continue reading this post →

200 Calories

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What’s a calorie? Well, it is a unit of energy. If you take a gram of water and put some energy into it, you’ll raise its temperature (assuming it is away from its boiling point). If you succeed in raising the gram of water’s temperature by 1oC, you’ve put one calorie of energy into it.

But that’s not the calorie you probably have used in your everyday conversation. You’ve probably been talking about the Calorie. (Note the upper case C.) The Calorie, or the kilocalorie. It is 1000 times larger than the calorie of the previous paragraph. It’s the energy needed to raise the temperature of one kilogram of water by 1oC (assuming it’s not at its boiling point). That’s the Calorie you find discussed in the context of nutrition – the energy content of the food you eat.

Without further ado, let me show you what the Calories “look like”. Let’s take a reasonable number of them – 200. Each of the pictures below represents 200 Calories of a food, which you’d get from eating it. Mini peppers, gummy bears, and kiwi fruit: […] Click to continue reading this post →

Look Up!

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Comet McNaught seems to be a gift that keeps on giving. Last night here in Los Angeles, just after the sun set, I stepped out to look from a nearby elevated spot – and there it was. With binoculars, it’s an impressive sight, and possibly the last naked-eye visible comet sighting for a long time. Unfortunately, I have no equipment that I can use to take a decent photo for you, so I can’t share what I saw.

But you can go out and look. I give some viewing tips below.

What you’re probably puzzled about now is why the experts kept getting the “last chance to see” message wrong. People seemed very sure back on Wednesday that it would be gone from view -and I did a post to that effect myself- and and the same thing was said on Thursday and then on Friday.

I’m guessing that this is because although they can track the position rather well, they […] Click to continue reading this post →

Andromeda Now Makes Sense

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andromeda IRThe Andromeda Galaxy is bigger than previously thought. Perhaps as much as five times bigger. I know that you’re thinking – “Oh, that’s because most of it is dark matter, right?” No, this is not another dark matter story. In fact, there are many newly discovered stars from a recent study! The suburbs of the galaxy are much more extensive than previously identified. It’s rather good news, since the galaxy makes more sense than it did before, in the context of our understanding of how galaxies form and evolve. (Image above is of Andromeda in the infra-red, from NASA.)

The point here is that current theories of evolution for galaxies have the oldest stars Click to continue reading this post →

All Hands on Deck

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all hands on deck Well, it’s the middle of the Bleak Midwinter, and the first day of classes of the new semester. Mine start tomorrow. It is time to get myself back into the classroom-teaching frame of mind -although to be honest I don’t think the break was long enough for me to have got sufficiently far removed from it: 85% of the research tasks that I wanted to do during the break remain undone.

Anyway, I must sit and contemplate what I am going to talk about in the graduate course entitled “Selected Topics in Particle Physics”. It’s my lunch break, so I thought I’d chat to you for a bit.

Rumour has it that everyone is expecting some sort of string theory course, reasonably complementary to the one that my colleague Nick Warner taught here two years ago. I’ve no interest in just teaching the standard string theory topics – a good and motivated graduate student can just look them up in a book if motivated enough (if they can’t they’re in the wrong business) – and so I’d like to throw in some material that is not packaged together in the standard way, and give them an education that emphasizes powerful ideas and techniques that are relevant to more than just standard string theory research, but theoretical physics in general.

You see, this is one of the wonderful things about the topic that you don’t hear about much when people say things (and write books for a general audience) about how much it is supposedly taking over smart young minds and leading them astray: It is a fantastic framework for training good physicists for whatever new and useful ideas and physics will come along in the future, whether it is string theory or some other topic. The point is that string theory has developed in so many different ways, and […] Click to continue reading this post →

Dark Matter in 3D

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Have a look at this:

hubble 3d dark matter

What is it? It is an image of part of the three dimensional (see below) distribution of clumps of dark matter in our universe, produced by an extensive survey using the Hubble telescope. How did they produce it, given that dark matter is -by definition- not visible? They deduced the presence of the chunks of dark matter by looking at the gravitational […] Click to continue reading this post →

Categorically Not! – Movement

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The next Categorically Not! is Sunday 7th January. The Categorically Not! series of events that are held at the Santa Monica Art Studios, (with ocassional exceptions). It’s a series – started and run by science writer K. C. Cole – of fun and informative conversations deliberately ignoring the traditional boundaries between art, science, humanities, and other subjects. I strongly encourage you to come to them if you’re in the area. There’s a website of past and upcoming events here. You can also have a look at two of the last two descriptions I did of some events here and here, and the description of a recent special one on Uncertainty that was held at the USC campus is here.

Here is K.C. Cole’s description of the upcoming programme:

“Movement: You can’t leave home without it. In fact, you can’t get anywhere without it—whether you’re trying to bring about political change, compose music, send a robot to Mars, or merely make your way across a room. You can’t even […] Click to continue reading this post →

Science on TV – Having Your Say

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Recall that I told you about the pilot for the upcoming show Wired Science in an earlier blog post. It airs today, (Wednesday, January 3) on PBS. It was made by KCET here in Los angeles, and as you may recall from the post, in August I learned some interesting things about the context in which the show sits. It is rather interesting. It’s all part of a head-to-head competition, or “experiment” as PBS are calling it.

You see, there are two other shows being piloted on PBS over the next couple of weeks too. One is Science Investigators, made by WGBH, Boston, and the other is 22nd Century, made by Towers Productions (I think). They are three different takes on a science TV show format. The casting, scripting, presentation… all these things vary a great deal.

They’re really trying to come up with newer, more accessible formats, with the aim of getting science out there to the general public. This is a great thing. Only one show will “win”, sadly. The prize is the go ahead to make more episodes, and have them air on PBS. The judges…. this is the important part… The Judges are YOU. Go to the PBS site […] Click to continue reading this post →