The Birth of Atoms

Your body contains trillions of atoms, of many different elements. There are atoms of hydrogen and oxygen, carbon and nitrogen,...but your body also contains many atoms of calcium, nickel, potassium, iron...even gold!


In all, there are 92 different types of atoms, most of which can be found in the molecules that make up the tissues of your body.

Since we know that when the universe formed, the only elements around were hydrogen and helium, where did all these other types of atoms come from?

The answer is quite startling...all of the atoms in your body, other than helium and hydrogen, weremanufactured in the center of a supernova...a star that once existed, but destroyed itself in a gigantic explosion!

To understand how this is possible, we need to look at what atoms are. The simplest atom is hydrogen, which contains a nucleus composed of one proton, circled by one moving electron. The next simplest atom, helium, has a nucleus with 2 protons, and is circled by 2 electrons.


The biggest naturally occurring atom is uranium, with 92 protons, and 92 electrons.

(For simplicity, we will ignore the fact that these atoms also contain neutrons in their nuclei.)

                                  

 It is possible for small atoms to combine to form bigger ones...but only under intense heat and pressure...the millions of degrees found in the center of a star. This process is called nuclear fusion.

Large stars will be so hot in their interior that hydrogen atoms are forced together to form helium atoms, helium atoms are forced together to form still larger atoms,...and so on. Eventually, large stars will contain in their interior, shells of many different heavier atoms, some as big as iron (57 protons).

If the star is large enough, when it runs out of fuel it will collapse in on itself. The relatively cooler outer layers hit the incredibly hot interior, and a massive explosion occurs, called a supernova. Stars that do this don't live very long...while a smaller star like our sun may burn for tens of billions of years, a massive star that is destined to become a supernova may burn out and explode in a matter of a few million years...a ten-thousandth of the lifetime of our sun.

During this explosion, temperatures rise once again; coupled with intense pressure, this is enough energy to force larger atoms to combine, creating all of the heavier elements from iron to uranium!

This explosion is so large that it propels the contents of the star out into space...including all the heavy elements it has made. Vast clouds of atoms of all types remain, where once there was a star.

We know that at the beginning of the universe, there was only hydrogen and helium. Massive stars formed from these gases, burned out in a few million years, and spewed the heavy elements they created into space around them.

This process has occurred over and over since the universe began some 17 billion years ago. We can observe it still happening today, in our large telescopes.

When our star (the sun) and its family of planets formed from interstellar gases some 5 billion years ago, those gases were already well seeded with heavy elements formed in supernovas that occurred in our interstellar neighbourhood in the previous 12 billion years. All of the heavier elements that went into forming the earth, the ground, the biosphere,... everything... came from this interstellar gas cloud. And so did all the elements in your body!

If you would like to learn more astronomy & astrophysics, visit 'We Are Not Alone'.

Ref Link: http://www.worsleyschool.net/science/files/thebirth/ofatoms.html

                                                                                                                                                                                      

E=mc2 Explained

 

Albert Einstein is perhaps the most famous scientist of this century. One of his most well-known accomplishments is the formula E=mc2


Despite its familiarity, many people don't really understand what it means. We hope this explanation will help!


One of Einstein's great insights was to realize that matter and energy are really different forms of the same thing. Matter can be turned into energy, and energy into matter.



For example, consider a simple hydrogen atom, basically composed of a single proton. This subatomic particle has a mass of


0.000 000 000 000 000 000 000 000 001 672 kg


This is a tiny mass indeed. But in everyday quantities of matter there are a lot of atoms! For instance, in one kilogram of pure water, the mass of hydrogen atoms amounts to just slightly more than 111 grams, or 0.111 kg.


Einstein's formula tells us the amount of energy this mass would be equivalent to, if it were all suddenly turned into energy. It says that to find the energy, you multiply the mass by the square of the speed of light, this number being 300,000,000 meters per second (a very large number):
                   
                 E=mc2 = 0.111 x 300,000,000 x 300,000,000 = 10,000,000,000,000,000 Joules


This is an incredible amount of energy! A Joule is not a large unit of energy ... one Joule is about the energy released when you drop a textbook to the floor. But the amount of energy in 30 grams of hydrogen atoms is equivalent to burning hundreds of thousands of gallons of gasoline!


If you consider all the energy in the full kilogram of water, which also contains oxygen atoms, the total energy equivalent is close to 10 million gallons of gasoline!


Can all this energy really be released? Has it ever been?


The only way for ALL this energy to be released is for the kilogram of water to be totally annhilated. This process involves the complete destruction of matter, and occurs only when that matter meets an equal amount of antimatter ... a substance composed of mass with a negative charge. Antimatter does exist; it is observable as single subatomic particles in radioactive decay, and has been created in the laboratory. But it is rather short-lived (!), since it annihilates itself and an equal quantity of ordinary matter as soon as it encounters anything. For this reason, it has not yet been made in measurable quantities, so our kilogram of water can't be turned into energy by mixing it with 'antiwater'. At least, not yet.


Another phenomenon peculiar to small elementary particles like protons is that they combine. A single proton forms the nucleus of a hydrogen atom. Two protons are found in the nucleus of a helium atom. This is how the elements are formed ... all the way up to the heaviest naturally occuring substance, uranium, which has 92 protons in its nucleus.


It is possible to make two free protons (Hydrogen nuclei) come together to make the beginnings of a helium nucleus. This requires that the protons be hurled at each other at a very high speed. This process occurs in the sun, but can also be replicated on earth with lasers, magnets, or in the center of an atomic bomb. The process is called nuclear fusion.


What makes it interesting is that when the two protons are forced to combine, they don't need as much of their energy (or mass). Two protons stuck together have less mass than two single separate protons!


When the protons are forced together, this extra mass is released ... as energy! Typically this amounts to about 0.7% of the total mass, converted to an amount of energy predictable using the formula E=mc2.

Elements heavier than iron are unstable. Some of them are very unstable! This means that their nuclei, composed of many positively charged protons, which want to repel from each other, are liable to fall apart at any moment! We call atoms like this radioactive.


Uranium, for example, is radioactive. Every second, many of the atoms in a chunk of uranium are falling apart. When this happens, the pieces, which are now new elements (with fewer protons) are LESS massive in total than the original uranium atoms. The extra mass disappears as energy ... again according to the  formula E=mc2! 
 "This process is called nuclear fission."

these nuclear reactions release a small portion of the mass involved as energy. Large amounts of energy! You are probably more familiar with their uses. Nuclear fusion is what powers a modern nuclear warhead. Nuclear fission (less powerful) is what happens in an atomic bomb (like the ones used against Japan in WWII), or in a nuclear power plant.



Albert Einstein was able to see where an understanding of this formula would lead. Although peaceful by nature and politics, he helped write a letter to the President of the United States, urging him to fund research into the development of an atomic bomb ... before the Nazis or Japan developed their own first. The result was the Manhatten Project, which did in fact produce the first tangible evidence of E=mc2 ... the atomic bomb!

Ref Link : http://www.worsleyschool.net/science/files/emc2/emc2.html