Twenty-five years ago today - in the month when I was born - the Space Shuttle Challenger broke apart shortly after launch. Seven human beings were killed on that flight in the pursuit of knowledge, exploration and discovery. There can be few more noble, more fitting, more human causes for which to give one’s life.
Shortly after the disaster Ronald Reagan made this speech, widely regarded - and justifiably so, to my mind - as one of the greatest speeches of an American President.
At the end of his speech Reagan quotes the poem High Flight by American aviator John Gillespie Magee, Jr., who died in 1941 in a mid-air collision. A fitting tribute indeed.
Oh! I have slipped the surly bonds of Earth
And danced the skies on laughter-silvered wings;
Sunward I’ve climbed, and joined the tumbling mirth
of sun-split clouds, — and done a hundred things
You have not dreamed of — wheeled and soared and swung
High in the sunlit silence. Hov’ring there,
I’ve chased the shouting wind along, and flung
My eager craft through footless halls of air….
Up, up the long, delirious, burning blue
I’ve topped the wind-swept heights with easy grace.
Where never lark or even eagle flew —
And, while with silent lifting mind I’ve trod
The high untrespassed sanctity of space,
Put out my hand, and touched the face of God.
Unfortunately, when I went out to look at the Perseids the sky over Oxford was fairly cloudy - and in the clear parts, I didn’t manage to make out any meteors. Ah well, until next year. Did anyone else have any luck?
If not, I suggest you have a look at this beautiful set of time-lapse videos, taken of the shower in Joshua Tree National Park in California.
The bright stripe of stars across the sky is of course the Milky Way - the spiral galaxy that’s our home, viewed edge-on from our position inside it. The dark patches are lanes of interstellar dust: compare them to the patches you see in Hubble photographs of distant spiral galaxies, and you’ll be reminded that we do indeed live in one of those things!
I mentioned recently that I’ve just moved house. If you want an exciting view of my new home you can see it here, courtesy of the BBC (the segment starts at about 16:30)!
[The embedded video isn't working for me, but I can't tell if that's just the computer I'm writing it on - if you have trouble, use the direct link above]
Perhaps more excitingly, you can see my housemate Joe Zuntz talking about the iPhone application he’s written for Galaxy Zoo. As I’ve mentioned before, Galaxy Zoo is an online project to enlist the help of thousands of members of the public in classifying millions of images of galaxies taken automatically by telescope, so that the data can be more effectively used for scientific study. With this new app iPhone users can classify galaxies during spare time on the train or elsewhere. (It’s a bit of a shame the BBC segment doesn’t mention that the main Galaxy Zoo website lets you classify them online without a smart phone.)
The Perseids are a shower of meteors which fall on Earth every year in July and August. The shower lasts for a while, but the rate is expected to peak tomorrow night, when you may be able to see a few meteors every minute if you’ve got a good clear sky. I’d definitely recommend going out to have a look - it’s probably the most impressive astronomical event you can watch with your bare eyes, unless you’re lucky enough to live in range of the Northern or Southern Lights. It’s also one of the oldest recorded events: there are Chinese writings documenting the shower at least as early as 36 AD.
A short guide on how to look for them is here, but really you can’t go far wrong by heading out to an open dark area and looking up!
The Perseids last year. This is a combination of 227 separate images taken throughout the night and combined, to show the circular paths across the sky the meteors take due to the Earth's rotation. Click for credit.
Hello again, dear reader. It’s been a little over a month since I posted last, during which time I’ve been up to various things. I went to two conferences in Poland - one on the use of supercomputers in astrophysics, which is quite central to my PhD; and one on Wikipedia and its various sister projects, organised by the Wikimedia Foundation, which is nothing to do with my work - scientists are allowed hobbies! I also moved house to a lovely place in West Oxford. My landlord is now the mathematician and author Marcus du Sautoy, which I find pretty cool even if almost no-one else does.
And, I went to this exhibition as promised. I’ll have some things to say about that and maybe the conferences over the next few days.
In the meantime, here again is a video of Jupiter taken by Voyager 1 during its approach, for no better reason than that I find it absolutely awesome. You can read more about it at my post here.
There’s a series of exhibitions on at the moment in the Southbank Centre in London to celebrate the 350th anniversary of the Royal Society. One that I’m looking forward to visiting is called Our Cosmic Origins: building the Milky Way. It’s about simulating galaxies using computer models, and from a chat I had with one of the scientists from Durham who are organising it it sounds pretty good: they’ve got lots of nice videos and demonstrations, including a Wii game that lets you fling galaxies together in real-time in an effort to dislodge the Solar System from the Milky Way. There are also Real Scientists there to answer questions and explain what they get up to in this work every day.
The exhibition’s on until next Sunday. I’m going to try and make it down to London to see it, though I’m a bit busy at the moment with moving into a new house. But if any of you gets the chance to go, do let me know what it was like!
That was the Japanese spacecraft Hayabusa (Japanese for “peregrine falcon”), returning to Earth two days ago after a seven year voyage. It went to explore an asteroid called 25143 Itokawa, which orbits the Sun at an avergae distance a bit further than the Earth but closer than Mars.
Lots of other spacecraft have flown close by asteroids to look at them before, but Hayabusa did something special: it actually landed on the asteroid briefly, so it could collect a sample and bring it back to Earth. This is the first time that a manmade machine has landed on a celestial body other than the Moon and returned home, which is a pretty exciting first.
The plan was for the craft to fire some metal pellets into the surface of the asteroid, and catch the debris thrown up by the impact to bring back for study. Unfortunately though, a problem with the firing mechanism may mean that the pellets weren’t fired (it can be hard to be sure what’s going on on a robotic craft a hundred million kilometres from home). But even if they didn’t fire, it’s possible that the craft itself threw up enough dust to catch - the pellets were to make absolutely sure - so there’s a chance we’ll have a usable sample anyway.
365 Days of Astronomy is website with daily podcasts (5-10 minute long sound clips) about various aspects of astronomy. Today’s podcast is by yours truly, and is titled “What’s in a name? The story of parsecs”.
It should be appearing on the site at some point today - in the meantime, have a listen to some of the others. There’s a lot good stuff on there.
One of my readers (thanks, Sister Lynn!) drew my attention to an article in the New York Times last week reporting a recent discovery by a team at Fermilab (the Fermi National Accelerator Laboratory). Their result pertains to the question of why the Universe has so much matter compared to antimatter.
Antimatter
Every type of matter particle which exists - electrons, protons, neutrons and others - has a corresponding ‘antiparticle’. The antiparticles are very similar to their particle counterparts, having the same size and mass - in a way they’re very like a mirror-image version, and also have reversed electric charge. Antimatter seems very exotic to us, not least because of the well-known fact that a particle and its antiparticle brought together will annihilate each other and release a colossal amount of energy, making antimatter very unstable and impossible to keep sitting in a jar without special precautions.
But this exoticness isn’t really inherent to the antimatter: after all, antimatter people living on an antimatter planet wound find a blob of matter just as strange and dangerous as we find them. Even the naming is arbitrary: neither type is more ‘anti’ than the other, since there’s a complete symmetry between them.
But why, if antimatter is so natural and so naturally paired to matter, is it rare and exotic when ‘normal’ matter is everywhere? Why are the two not equally abundant?
That question is one of the most important ones facing physics today.
A month or so ago I wrote about the galaxy NGC 4522 undergoing the process of ‘ram pressure stripping’ as it falls through a cluster of galaxies. Although the space between the galaxies seems pretty empty it has a thin gas floating in it - and there’s enough there that a galaxy ploughing through at hundreds of kilometers a second feels an enormous wind in its face, with the result that is gas is blasted off it into a trailing cloud. This stripping is a fairly interesting process with profound consequences for the galaxy in question, so astronomers are obviously interested in studying it. But - as is often the case when you study such a vast and slow-moving beast as a galaxy - some questions can be difficult to answer just by looking through a telescope.
A simulated galaxy undergoing ram stripping. The image is about a million light years top to bottom.
For example: what’s the most important property of the gas in determining the amount of stripping that goes on? Is it the density of the gas, or the speed at which the galaxy hits it? Then again, does the temperature of the gas have a bigger effect? To answer this question observationally we’d find lots of galaxies undergoing stripping, measure all the quantities we’re interested in, and look for a relationship. But it might not turn out to be as simple as all that. For instance, the gas tends to be hotter and denser in bigger clusters. So if we find a relationship between stripping and density, it could just be telling us about the cluster mass. Since cluster masses are often quite hard to measure accurately - and in fact we often measure them by looking at the gas temperature - sorting out which variables are affecting what can be tricky.
My name's Olaf Davis, and I'm a PhD student in the Astrophysics group at Oxford. This blog is mainly about astronomy and mainly aimed at the layman (no physics or maths training required!) but I sometimes stray into other areas which interest me, particularly maths and science reporting and communication.
