Monday, May 21, 2012

Refrigerator Magnets

How many time has it happened that you came home and find magnets stuck to your door.  Instead of throwing them away or immediately putting them on your fridge , lets try and learn something about them. Here is a short, easy and fun-to-do scientific experiment with refrigerator's magnets. For our experiment we need two magnets and we will try to stick them together in different ways.

Watch the video to understand what we are going to do and then read the explanations

Try and repeat the experiment shown in the video. Put the magnets together and try to slide one of them up and down. There can be three possibilities:
1) The magnet will slide smoothly
2) The magnet will jump and make a noise
3) The magnets will not hold very well

If the magnets do not hold well, turn one of them 90 degrees and try again, than you will have either option 1 or 2 depending on the direction you choose to slide the magnet (up-down or left-right). Change the direction of sliding and the direction of one of the magnets until you encounter all three possibilities given above.

So why is this? A full explanation of magnetism will require to go into a detailed explanation about magnetic fields and is really unnecessary. We will focus just on remembering that a magnet has its end referred to as the north and south poles. When a north pole is attached to a south pole, the magnets will pull each other, but when attempting to attach a north side to a north side, the magnets will reject each other.
The refrigerator magnets have indeed the two poles but the poles are lined out one next to the other, like columns, within the magnets. Look at the illustration below to see how it works.
Refrigerator Magnet
Refrigerator Magnet is built from strips of North and South next to each other
So when we attached our refrigerator magnets in a way that a north meets south, they  attach strongly. In one direction (for example: up-down) we can slide them with ease, since even if we slide them, the south pole is still on a north pole, but when we try to slide them in the other direction (left-right), it happens that the north pole meets another north pole which immediately rejects it until it finds the next south pole, this makes the non-smooth movement and the loud noise.
When the magnets are attached in the other direction, the north poles meet north and south poles all the time. This creates rejection of the magnets and attracts force which more or less eliminates each other and the magnets do not stick, or connect very loosely.

Sunday, May 20, 2012

Making a pinhole projecter for viewing the sun

A pinhole projector can be used to watch the sun safely. Even if you do not have a solar telescope or a special solar eyeglasses you can still watch the Venus transit with this simple homemade pinhole projector. It can be used during eclipses and during the Venus transit. All you need is a box, as large as possible. For the Venus transit a bigger box is required or simply connect several boxes together.

All methods for viewing the Venus transit safely

Here are the steps to create the pinhole projector.

1) Cut a hole in the box
2) Cover it with foil
3) Make a tiny hole in the foil using a booby pin
4) put the box toward the sun
5) Never look directly at the sun!
6) A tiny projected sun will appear at the end of the box
7) The sun size is about 1/100 of the box length
8) You can even use a refrigerator box!

Here is how it looks

A box to project the sun image
The Box. Notice the foil on the right.

 The sun is projected in the box

 The sun is projected in the box
 The sun is projected in the box
And a short video which will explain how to use it...

All methods for viewing the Venus transit safely

Cassini's Highlights

Cassini is a spaceship orbiting around Saturn sine 2004 and at least until 2017. Cassini left earth in October 1997 with the European Space Agency's Huygens probe. The probe was equipped with instruments to study Titan, Saturn's largest moon. It landed on Titan's surface on Jan. 14, 2005, and returned spectacular results. Cassini finished its primary mission but since the spaceship is functional the missions was extended at least until 2017.
This article will present several of Cassini's best photos. There are thousands of greats photo and new are acquired every day. for some of the photo it seems like an artist photographer aimed the spaceship's cameras to get the composition. Enjoy the results and keep checking for great new Cassini's photos.
The first photo will give a full portrait of Saturn. This is an old photo from 2005. This is not a single photo, it is a mosaic of 126 taken over 2 hours from 6.3 million km (4 million miles). A full resolution version of this photo is here

Saturn (2005): Cassini NASA JPL
Saturn (2005): Cassini NASA JPL
Saturn rings cut Titan just like Chinese's chop-sticks. Below the smaller moon Mimas. Only the edge of the rings is visible. the center of the rings is in Saturn's shadow!

Saturn's rings, Titan and Mimas
Saturn's rings, Titan and Mimas. Credit: NASA
This is an amazing photo showing the dwarf moon Daphnis (Its diameter is only 8km) which orbits in the ring. The small gravitational effects of the little moon on the rings is quite visible!

Daphnis between Saturn's rings NASA JPL
Daphnis between Saturn's rings NASA JPL
The next photo shows the shadow of Titan (diameter: 5150km ) on Saturn. If you happen to be in that shadow you would see a total solar eclipse. The rings face the sun, so their shadow looks very thin.
Titan's shadow on Saturn
Titan's shadow on Saturn NASA JPL
Small moon Pan travels between the rings in the Enkce gap. You will need to take a good look at the photo. Pan is not the moon in the bottom of it (the moon at the bottom is Janus) . It is in the middle and it shed a long shadow over the rings.

Pan shadow on Saturn's rings
Pan shadow on Saturn's rings NASA JPL
Now for a game of who is who. Two moons (Dione and Rhea) are attache to each other? well no, the distance between the moons is 500,000km, but the timing makes them looks like they go one over another
Dione and Rhea together
Dione and Rhea together NASA JPL

There are also videos (Cassini's does not have a video camera, the video was created from a series of photos). This video shows Saturn's Aurora in Infrared light.

Another strange look on Saturn's north pole
Auroras over Saturn
Auroras over Saturn NASA JPL

A closeup of Titan. From time to time, Cassini's has opportunities for flybys, a very close approaches to Saturn's moons from time to time.
Clouds on titan. NASA JPL
Clouds on titan. NASA JPL

What happened to Hyperion that gave it this unusual shape?

Hyperion. NASA JPL
Hyperion. NASA JPL

The moon Enceladus is another strange moon. It has lots of activity on it, including geysers which erupts jet streams to the space.

Saturn's moon Enceladus
Saturn's moon Enceladus

 Surface of Enceladus
Surface of Enceladus
Surface of Enceladus

Saturn's rings are very thin. Mostly their thickness is just 10 meter! but from time to time there are mountains in the rings. look for them in the next photo and see that these mountains (up to 2500 meters) cast long shades on the rings' plane)

Saturn's rings
Saturn's rings
Saturn's rings are dynamic. The ring are composote from millions small particles and they change constantly.

Dione from 115,000 km
Dione from 115,000 km

There are more great photos and more will come in the future. All photos are taken from CICLOPS - Cassini Imaging Central Labortary for Operations
Which includes photos from the last decade and even before Cassini arrived Saturn (take a look for Jupiter photos!)

Monday, May 14, 2012

Venus Phases

Venus is one of the two inner planets. An inner planets is a planet that its orbit is inside the Earth orbit. There are only too such planets, Mercury and Venus. Inner planets have some major characteristics:
  • Their angular distance from the sun is small and thus they are seen only some hours after sunset or before sunrise. Unless near the poles, it is impossible to see Venus at midnight. As a result, inner planets will never be in opposition, but unlike any other planets they will be twice in conjunction with the sun, one when they are behind the sun (superior conjunction) or in front of the sun (inferior conjunction). When they are directly in from of the sun the inferior conjunction is called a transit.
  • Inner planets has phases just like the moon, and from the same reason. At superior conjunction the planet is totally illuminated but since it is close to the sun we can't see it. As the planets moves it wans until is is half lit and when it gets closer to Earth it become a crescent. Since it get closer to earth it get bigger and bigger. Venus will show its phase with even the smallest magnification. A telescope of even a binoculars at 7x or 10x will do, but the binoculars must be very stable, preferably mounted on a tripod. Mercury is much smaller and a telescope is required to see its phases.
Crescent Venus
Crescent Venus

Since Venus has an atmosphere it can be viewed even in inferior conjunction. Such viewing is dangerous since Venus is very near the sun. It is possible to view it just after sunset when Venus is high or from the poles when Venus Is moving almost parallel to the horizon for many hours. Viewing it will see a disc around Venus. Of course this can't be views during a transit. The next inferior conjunction for Venus are 11-Jan-2014, 15-Aug-2015 and 25-Mar-2017 (every 19 months).