Light entertainment

19 06 2010

The more we have, the narrower our perceptions seem to become. In a world where information is delivered through our iphones and blackberries we now control precisely when and what reaches us. You only care about Justin? Set you RSS, twitter and facebook settings to focus on everything Bieber.

We could lament about how everything is changing and how we can shut off from reality. But that isn’t the point of the post. We just want people to step back for a second. To think about our world, and our place in Universe.

It’s easy to think stars (the ones in the sky, not those in Hollywood) are too far away, too esoteric and ultimately too irrelevant to worry about (actually, doesn’t that sound like movie stars too?). Of couse, the Sun tells us every day that isn’t the case. Our stellar neighbour is the power source for over 99% of the life on our planet.

In fact, even before the Sun was around, the atoms in our bodies were being processed by a massive star that likely died in an enormous explosion. Much the same way that life on our planet is in balance between death and rebirth, so generations of stars grow and die. A lifetime of tens of millions of years might seem long, but in a Universe billions of years old, some stars are born and die in the blink of a cosmic eye.

So stardust we are. More than a line from a song, it describes our planet and everything on it. Yet our connection to stars is actually even more complex.

Stop for a second to think about the light from stars. What creates it?

The nuclear fires in the centre of stars release enormous amount of energy in the form of gamma-ray radiation – a form of electromagnetic radiation like light, only with a much, much higher energy. This radiation interacts with all the material, a soup of particles physicists call a plasma, between the core and the surface of the star. This journey will turn the energy of the gamma-rays into an entire spectrum of different wavelengths of electromagnetic radiation, including the light that we see.

And so off into the depths of space heads the light created by the nuclear fires. On its journey through the depths of space it will follow the shortest path it can. Following the curves in spacetime that Einstein predicted, its journey to the Earth can take millennia.

Perhaps the strongest interaction it will face on its journey to your eyeball is that with our own atmosphere. Far from being a featureless ether, our atmosphere will bend and distort the light that passes through it. Think of it being like a constantly changing lens. That’s also the reason why stars twinkle. The light from them is constantly being shifted and bent by very small amounts.  Telescopes have a really hard time with this, but that‘s another story.

So eventually our single piece (or photon) of light, carrying a tiny packet of energy that was born in the unimaginably intense nuclear fires of a star, arrives at your eyeball.  What happens then?

The amazing results of billions of years of evolution kick in. The rods and cone cells in our eyes contain proteins that can change their configuration when light interacts with them. Through a complex cascade of chemical reactions the energy of the light is converted and amplified into an electrical signal travelling along your optic nerve.

The optic nerve is more than one single nerve fibre, each one actually bundles together over a million individual fibres. The precise destination of the nerve endings is equally complex. But if you trace the connections, many of them wind up at the back of your head, in the part of the brain called the visual cortex.

How does our electrical signal wind up in a thought about seeing a star? While we know a lot about how brain activity relates to things we observe, the true nature of consciousness remains one of nature’s greatest mysteries. We can trace a lot of activity in the brain, but the “why” of consciousness remains elusive.

So we’ve gone from the energy of the nuclear fires in a star, to energy involved in signals travelling down your optic nerve, to the energy in your visual cortex. Not only are you stardust, you contain the energy of starlight.

If you thought you weren’t connected to the stars, think again.

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19 06 2010
Tweets that mention Light entertainment « Ecogirl & Cosmoboy's Blog -- Topsy.com

[…] This post was mentioned on Twitter by Linda Campbell, Rob Thacker. Rob Thacker said: New blog post about how we are connected to the stars – it's more than about being stardust… "Light entertainment" http://bit.ly/a6Oxza […]

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