Stardate Friday 23rd September 2005 Issue 151

Of course, if you fancy taking the scenic route to Aquapharm you can make you way through our sparkling new homepage.  Don’t worry about getting lost though – you’ll still find the same fun-filled content behind the scenes.

OK, so we can’t all live in sunny Spain, the best place to have a look at the October 3^rd annular eclipse, but that doesn’t mean that if the skies clear we won’t have a fabulous view of one of the most amazing natural phenomena of all time!

People were once terrified by the sun’s light being blotted out, but now we are mesmerised, and with good reason.  When else can you really grasp that we are on a small spinning globe, orbiting a huge ball of burning gas?!

An eclipse happens when the Moon passes between the Earth and the Sun – effectively getting in the way.  By an amazing coincidence, the apparent size of the Moon is the same as the apparent size of the Sun (most of the time), as seen from Earth.  This is entirely down to their sizes and distances from us.  In total eclipses the sizes are a perfect match.  But since the Moon isn’t in a perfectly circular orbit the distance changes and sometimes the apparent Moon size is not big enough to cover the entire disk of the Sun.  A ring of light remains around the edge - this is an annular eclipse.

In the UK we won’t see the entire annular eclipse but the Moon is certainly going to take a reasonable bite out of the Sun this time.   

OK, so now you want to see it… and not for the last time we’ll point out that LOOKING STRAIGHT AT THE SUN CAN BLIND YOU – AT NO POINT DURING AN ANNULAR ECLIPSE SHOULD YOU LOOK AT THE SUN.

The Moon starts to bite at around 8.50am BST and will finish around 11.20am BST, with the maximum bite at 10am BST.  They’ll be around 65% of the Sun’s disk covered, slightly more in the south and less in the north.

So if you aren’t allowed to look at the Sun during the annular eclipse how are you going to see it?  You’ll have to keep reading, as we have the perfect activity for you!

If you can’t wait to have a look at the October 3rd eclipse you’ll need to be prepared.  LOOKING DIRECTLY AT THE SUN IS VERY DANGEROUS!  Don’t look with your naked eyes, don’t look through sunglasses and definitely do not look at it through a telescope or binoculars…

You will need:

• A piece of cardboard – A4 size is more than big enough
• A large sheet of white paper
• A pin

Additional:

• A mirror

What to do:

1. Make a small hole in the centre of the cardboard – start small and if you think it is too small make it bigger, obviously the reverse does not work.
2. Put the piece of paper on the ground.
3. Stand with your back to the Sun and hold the card with the hole out in front of you.  Move it around until you see an image of the Sun on piece of paper.  During the eclipse you’ll slowly see the round sun turn into a crescent as the moon cross it.

And an alternative, snazzier pin hole camera…

1. Use your cardboard with a hole to cover a mirror.
2. Point the cardboard-covered mirror at the Sun and let the Sun’s reflection through the hole beam onto a wall.
3. Balance it on books so that you can sit back and enjoy the spectacle.

What’s going on?

Every point on the Sun emits some light.  If we draw rays of light coming from the Sun in all directions we can see how the whole Earth is illuminated.  Imagine holding up the card with the small hole in it.  Only some of the Sun’s rays can pass through the pinhole and land on the paper screen.  Rays from the top of the Sun pass through and down and end up at the bottom of the screen while those from the bottom go upwards through the hole and end up at the top of the paper screen.  On the screen is a small upside down and back-to-front image of the Sun.

If you have a big hole lots of rays can pass through, so the image is bright but it will be a bit fuzzy.  Imagine drawing rays from a single point on the Sun through the hole.  Because the hole is big a number of rays can fit through, landing at different points on the screen – so there is more than one point on the screen which corresponds to a single point on the Sun.

A small hole will sharpen the image but it will be dimmer and trickier to see – so it is important to reach a happy medium.

They might be brightly coloured and they may have groovy images on them, but can your periodic table poster do all this?  ICT guru Roger Frost takes us on a tour of a new breed of interactive whiteboard periodic table…

			Periodic table – Nucleus and Electrons After seeing a few periodic tables on the ‘net’, you might wonder how great it would be if the wall could come alive too. Well this great example does just that… Click the helium symbol and see two electrons move in an orbit, click lithium and another electron appears in a new orbit, keep going up to krypton by which time you see the well defined orbits. Prefer to see the nucleus?  Switch to see it and see how this builds up too. For advanced work, s,p and d-orbitals also change alongside a line spectrum. Here’s a periodic table possibly cleverer than Mendeleev! See “David's Whizzy Periodic Table” free at:  http://www.colorado.edu/physics/2000/applets/a2.html Whiteboard rating: 3 p orbitals, filled

Thanks Roger!

NASA Eclipse For years any Google search will immediately turn up Fred Espenak’s NASA Eclipse page for all your eclipse info.  With more whistles and bells than you’ll know how to use, this fab complete reference site is perfect for all eclipses; lunar and solar, past, present and future.  Keep an eye on future lunar eclipses - more common than solar ones but still very exciting – but I’m afraid the October lunar eclipse won’t be visible here though.  http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html

Swim for it So you thought swimming was all about sport?  Well there is more science in your pool than you ever realised.  If you have ever had a look at a stagnant pond then you’ll know that that is what your pool would turn into without some chemistry, biology, physics and a great deal of engineering.  Play Swim For It, collect the coins and watch as the pop-ups let you in on the secrets of keeping the pool hygienic and what happens when it isn’t! http://www.planet-science.com/wired/ games/swimforit

Thanks for reading – hope you enjoyed this week’s offerings.  Keep emailing to planet-science.news@nesta.org.uk with events, activities and jokes.

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