Archive for February, 2009

Track space debris on Google Earth

Friday, February 27th, 2009

After the recent collision between two satellites which I mentioned, Robert Simpson at Orbiting Frog has written a program that allows you to track the debris in real time using Google Earth. He’s got a list of other objects you can track too (downloads here) including the International Space Station, Hubble Space Telescope, and debris from the Chinese missile test I mentioned. I haven’t tried them out yet, so let me know if you do.

Tracking orbiting debris with Google Earth. Credit: Robert Simpson

Tracking orbiting debris with Google Earth. Credit: Robert Simpson

Via Bad Astronomy.

Posted in Space travel | No Comments »

Solar prominence

Tuesday, February 24th, 2009

This is a Solar prominece, a column of gas being lifted by the Sun’s magnetic field into a twisted claw-shape. The picture was taken by a satellite called SOHO.

A Solar prominence. The blue dot in the top right shows the size of the Earth. Credit: ESA and NASA

A Solar prominence. The blue dot in the top right shows the size of the Earth. Credit: ESA and NASA

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Posted in Astronomy, Stars, Sun, Tuesday Pictures | 2 Comments »

Galileo and the IYA

Saturday, February 21st, 2009

2009 is the International Year of Astronomy, and was chosen because it’s the 400th anniversary* of the first use of the telescope for astronomy, by Galileo Galilei. The instrument had only been invented the previous year, and Galileo made significant improvements to its design and turned it to scientific use.

The first use of an astronomical telescope seems like an event worth celebrating for its symbolic significance, but Galileo also made some groundbreaking scientific discoveries in the first two years of its use. I’m going to talk about four of them here.

Galileo published his observations in his book Sidereus Nuncius, or “Starry Messenger”. A scanned copy complete with his hand sketches of what he saw is here.

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Posted in Astronomy, History of science, Instrumentation | No Comments »

Space debris

Saturday, February 14th, 2009

On Tuesday two satellites collided above Siberia: one belonged to Russia, and the other was a commercial craft owned by an American company. The Russian satellite had been disused for a while, but the American was busily transmitting mobile phone signals - until Tuesday.

Satellites are fairly big things (these two weighed around 500 and 900kg), and orbiting the Earth means moving very quickly. Exactly how quickly depends on the height of the orbit: the closer to Earth a satellite is the stronger it feels the pull of gravity, so the faster it needs to be moving to keep itself aloft. This collision took place almost 800km above the Earth’s surface, at which height the satellites were moving at around 30,000 km an hour (or 8 km per second). Being hit by a tonne of metal moving that fast is dramatic, to say the least! A back-of-the-envelope estimation by Phil Plait (whose blog I recommend, by the way) puts the amount of energy released in the collision at about 20 billion Joules - that’s as much as five tonnes of TNT releases on explosion.

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Posted in Space travel | 4 Comments »

The Universe: a brief tour

Saturday, February 14th, 2009

To start my series of introductory astronomy posts, let’s take a quick tour of the universe and its contents. I’ll cover most of the topics here in more detail later, providing details to fill in this framework.

The Solar System

Let’s begin with the familiar Solar System. The Sun is orbited by four rocky planets (of which Earth is the largest); four gas giant planets all much larger than Earth; and many tiny ‘dwarf planets’, asteroids and comets made of rock and ice. They stretch through space over a diameter of 10 billion or so kilometers, but Earth is pretty near the centre at just 150 million km from the Sun.

The planets to scale

The size of the planets to scale (distances not to scale). Click for a bigger version. Credit: NASA

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Posted in Astronomy, Introductory topics | No Comments »

Happy Darwin Day!

Thursday, February 12th, 2009

Today is Darwin Day, a “global celebration of science and reason” held to celebrate Darwin’s birthday. This year it’s his 200th - and later this year will be the 150th anniversary of the publication of his On the Origin of Species. Both Nature and Scientific American have evolution-related podcasts up to mark the event.

There are plenty of people writing exciting things about Darwin and evolution for today and plenty of stuff already written*, but here are a few reasons I think evolution is exciting:

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Posted in Biology | No Comments »

NGC 4921

Tuesday, February 10th, 2009

Here’s a beautiful image recently released by Hubble, showing the spiral galaxy NGC 4921 in the Coma cluster.

NGC 4921

NGC 4921 - click for bigger image. Credit: ESA/Hubble


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Posted in Astronomy, Galaxies, Tuesday Pictures | No Comments »

Manifesto

Tuesday, February 10th, 2009

Welcome to The Cosmic Web!

I intend to write mainly about two topics here, though I may also wander into other territory. The first is astronomy, which I’ll be pitching towards the proverbial intelligent layman. I’ll start out with some posts introducing basic concepts and topics in astronomy, and might review some recent papers I think will be of interest.

The second topic is science communication. I will try to include a reasonable proportion of positive posts about this to balance the inevitable “oh gods the popular press is so bad at science reporting”, but I make no promises.

I’d welcome any comments or questions, either general or related to specific posts, and particularly suggestions for topics you’d like to see covered or news stories and papers you think I might find interesting.

The ‘I’ above is Olaf Davis, a graduate student in Astrophysics at Oxford University.

Posted in Meta | 5 Comments »

The Drake Equation: intelligent life and not-so-intelligent journalism

Tuesday, February 10th, 2009

“Number of alien words quantified” says the BBC, reporting on work by Duncan Forgan which used a simulation of a Milky Way-like galaxy to predict the abundance of technological civilisations. The article makes it sound pretty definitive: “Intelligent civilisations are out there and there could be thousands of them, according to an Edinburgh scientist.” “The current research estimates that there are at least 361 intelligent civilisations in our Galaxy and possibly as many as 38,000.”

One often hears scientists opine that there are almost certainly other intelligent life-forms in the universe, but putting a hard lower-bound on the number would be pretty awesome. Let’s see if we believe it, shall we?

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Posted in Astronomy, Biology, Science communication | 5 Comments »