surprise surprise!

as this picture shows, the (visible) light that we see with our own eyes is just a teeny tiny portion of what is called the electromagnetic spectrum:

the picture actually comes from a t-shirt (but if you happen to land on that page, please do not read any of the comments, they're all wrong!!!) but the designer borrowed the idea from a science book, so it's pretty useful. look at the names above: don't they evoke any memories?? gamma rays, x-rays, ultra-violet, infra-red, microwave, radio... although we might relate different real-life concepts to each of them, they are basically the same thing: radiation, light, just like the one we see with our very own eyes. just, with different, very different energy, the gamma rays being the most energetic, and down all the way to the radio.

astronomical objects, such as stars, galaxies and other stuff, emit all these sorts of radiation, from gamma to radio. fortunately for us, the earth's atmosphere absorbs most of them (because they would be dangerous or even lethal to living creatures), that means that from earth we can only observe in the visible and in the radio band. yes, they are also referred as spectral bands.

but if we shoot a nice (and super expensive) satellite up into the skies, so that it orbits the earth, then we can observe in the whole spectrum, and gain a lot more information about all sorts of astronomical sources and the physical processes happening there. that's why Planck and Herschel will be launched soon (check prev post) and many other satellites are already up there doing this job.

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beware: recently i'm reading over and over people writing that waves in other bands besides the visible are sound waves. like that we could listen to the sound of the stars. SO NOT TRUE. sound waves are one thing, electromagnetic waves (ie. light) are a totally different thing. maybe it's the "radio" word that creates confusion. maybe the word "frequency". whatever. the only difference between radio and visible and gamma rays is THEIR ENERGY!!!

don't know if i managed to be clear enough. maybe not. i'd need to get started with an intro to waves. and if you happened to be on this blog, you probably already know.

anyway: don't listen to stars - or to whatever other weird ideas crazy people have!!!

Image credits: Threadless - www.threadless.com