Tuesday, 28 September 2010

Why is the sun "burning" in space?

The wording of this question can turn the meaning around completely. Let's look at the right question and the wrong one. I see it being asked too many times, so hopefully I'll set this right for some people.

The wrong question: Why is the sun burning in space?

Outer space has no gasses in it. Thus there is no pressure and a person without protection would experience his blood boiling, extreme cold and possibly his less protected areas popping out of his body. But that's beside the point. No gasses means no oxygen or any other oxydiszng agent for that matter. Thus, nothing can combust in space. Therefore, the sun is not burning.

The right question:   What causes the sun to emit heat and electromagnetic waves?

Well I'm not that good with words. Basically, the sun is not burning. A complex reaction called fusion is constantly occuring deep at it's core. At one point it it's life, the Sun was nothing more than a cloud of hydrogen gas. Somehow a few hydrogen molecules got together, they formed a gravitational pull, pulling in more and more molecules. Eventually the ball was so heavy that the pressure at the core caused two Hydrogen molecules to fuse. What followed was a sight that not even holywood special effects artists can portray. The Sun lit up like a christmas tree and started fusing hydrogen atoms to form helium. This reaction is egzothermic, meaning it emits heat, which is basically a certain wave in the electromagnetic spectrum.

Now our Sun is forming heavier elements like oxygen and nitrogen in itself. When it's life time comes to an end, the Sun will explode in a supernova, releasing all the elements out into space, where they will gather together as dust and maybe, one day, form another planet, perhpas even similar to Earth.

Why do plants grow towards the sun?

Plants are all around us and chances are you've come across a few in your life. Also we've heard countless times that "without sun, plant's couldn't grow". I won't get into why they actually need sun light to grow and what processes happen, let's just take it for a fact now. Most plants are adapted to absorb as much light rays as possible, they grow wide and thin leaves and in such a manner that the leaves would not block the sun for other ones. Another adaptation is that parts of the plant turn to the sun - the blossom, the leaves, even the stem.

sprounds reaching towards the light source


Why does this happen? Well this phenomenon is called phototropism. The process is not yet fully understood by scientists, but current models say that there's a hormone called auxin in plants, which releases H+ ions to the unlit tissues of the plant. The pH value decreases and the cell walls are acidified and therefore weakened. This turn of events also activates an enzyme expansins, who also breaks the cell walls. As they become fragile, gravity takes over and the whole plant bends towards the direction of the light source. As thousands of these processes occur all over the plant, it forms the movement we have come to know as photoropism.

Monday, 27 September 2010

Why is metal hard?

First of all, let me tell you that not all metals are hard under STP (standart temperature and pressure), for example, the well-known metal mercury is liquid under room temperature and one atmosphere of pressure. However, most metals are hard because of metallic bonds. As the atoms of a particular metal draw close together, their respective electrons do not stay attached to the atoms. Instead, they detach and for a "electron sea" in layman's terms.

Individual atoms and free electrons.
As you can see from the atomic structure, a metal is hard because it's atoms are close together, forming layers.  Gasses, on the other hand, have molecules that drift far and wide apart, thus creating a large volume, low density compound. The free electron sea is also the reason why all metals conduct electricity, the electrons are free to move, that is to say, they carry the current.