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Physics, Astronomy & Cosmology / Magnetism prevents us walking through walls?

« on: 10/05/2011 15:40:48 »

Good Afternoon,

I saw a documentary the other day which was talking about magnetism and how important this
force is in the universe. The programme stated that it was magnetism at the atomic level that
prevented our hands from being able to push through a wall for example.

It was explained that atoms are mostly space with basically protons, neutrons and electrons
making up the parts. I just wondered is it magnetism that is holding the electrons in orbit
around the nucleus of an atom? If something is emitting some kind of magnetic field, is there
a way to neutralise that magnetic force with an opposite or negative version of that magnetic
field?

Many thanks for your time and patience in reading and answering my question,

Graham

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Physics, Astronomy & Cosmology / What is Time? If there was no light would Time cease to be?

« on: 20/10/2010 10:52:06 »

Please excuse me if I am asking a stupid question, but I am trying to understand exactly what time is. When I think about time I immediately link it to light. Astronomers often tell us that they are able to take pictures of the universe billions of years in the past and that this is due to the amount of time it takes for light to travel. As I understand it, if I am looking up into the night sky what I am seeing is actually the past, in the case of the sun light I am seeing approximately 8 minutes into the past where as looking at the stars I could be looking many millions of years into the past. This is where I start to get boxed in with my own limited knowledge and perhaps some of you more knowledgeable people could enlighten me. If there was no light would time cease to exist altogether? I appreciate anyone taking the time to help me try and understand this.

Graham

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Chemistry / What is Colour?

« on: 06/03/2008 10:12:31 »

I was pondering something today and not being of a particularly scientific nature i wonder if someone out there may be able to help. I will state what i understand to be true, please feel free to correct and adjust what i am saying and hopefully i can come to understand the whole concept.

I was trying to understand what the concept of colour is, and how that relates to the elements and objects we see around us. As I understand it, colour is the by product of how Photons interact with a given thing as well as the perspective of the person or thing that is viewing it. Lets assume that i have perfect vision for the purposes of this conversation.

So i have a dish in front of me that contains one gramme of pure gold, lucky me!! The light photons hit the gold atoms, and interact with the electrons. Some might pass through the mass, some might be refracted away from my eyes but some will hit the electrons and then will be returned to my eyes. The result of this process is that i see an object that is Gold in colour.

I guess my first question is why i see any colour at all and the one gramme of gold is not just see through. As i understand it there are no solid elements from the periodic table of elements that are see through. I imagine that this is because the photons are not able to simply pass through the gold atom unaltered. Some are absorbed, some pass through and some are reflected, the photons that are reflected are interpreted as gold by my eyes.

Do the photons interact with the Electrons, Nucleus or Both? I am assuming that the electrons have very little to do with the colour that we see as if we were to change the charge of the one gramme of gold atoms from neutral and therefore change the amount of electrons per neutral atom from 79, the actual colour of the gramme of gold remains the same. This leads me to the conclusion that the aspect of colour must be determined by the interaction of the photons with the nucleus of the atom.

From my basic knowledge of Chemistry the Nucleus is comprised of many smaller components but can be generalised as Protons and Neutrons. In Gold we have 79 Protons, and if the number of protons were changed then the atom would no longer be gold. The number of Neutrons in Gold is 118 (∑(197-79)), and the number of Neutrons can change in the atom without creating a new element, instead this just creates a new isotope of Gold. To the best of my knowledge changing the number of neutrons would not alter the colour of Gold. So does this mean that the colour of Gold, has a direct relationship to the fact that it has 79 Protons, and it is the interaction of light Photons with the 79 protons that leads to me seeing Gold as a gold colour?

Finally, I know that Glass is normally made of Silicon and Oxygen and some types of glass have traces of boron, calcium and sodium. How is it that Silicon in its normal state is not see through but when combined with Oxygen it suddenly is? Is it because on its own Silicon would has 14 protons but when combined with Oxygen this results in SiO2 which has 30 Protons?

Well i think i have spouted just about enough rubbish to give you an idea at what i am getting at and also where my mind is currently at so that someone can hopefully help me out and point me in the right direction.