One hundred years of discoveries: Quarks, Antimatter, Dark Matter and Dark Energy
The today’s discoveries have the same impact as the discoveries made hundreds of years ago have had. History faced lots of discoveries, many of them forcing the scientists to rethink all the theories that they thought to be accurate, and the fact that nowadays we are witnesses of this kind of breakthroughs only tells us how limited we still are and how much we still are to discover.
Steven Hawking, a genius mind trapped into an almost complete paralyzed body, has shown to the public in his bestseller „A brief history of time” that the Universe’s mechanics can be explained using common language and no equation, he proved that you don’t have to be a genius to understand it. I was interested in the Universe since I was a child, but at that time and many years later, I thought that the laws that govern it are too complicated for me, so I didn’t bother to understand it, I was just enjoying it. I still think so, but that doesn’t stop me now to bind piece by piece like in a puzzle game and see the bigger picture, just like one uses the computer doing amazing stuff like playing games or movies, but not knowing that ALL the data that a computer knows and works with is a pair of numbers, 0 and 1, absolutely nothing more. Everything else is code, complex instructions wrote by humans on how the computer has to juggle with 0 and 1 in order to show nice images on the screen. About the same way I see the Universe showing amazing stuff, see it at work juggling with matter and energy in frozen-in-time images taken billions years ago, but not knowing the details, the mathematical equations that explain everything. Almost everything.
Molecules are made of atoms, atoms are made of nucleus and electrons, the nucleus consists of protons and neutrons and these two particles are made of quarks. They are interesting because they are quite odd. One odd thing about quarks is that they come in six flavors (types, but that’s how they called them): up, down, strange, charm, top and bottom, each having different properties. The existence of other subatomic elementary particles has been proposed in 1964 but it took ten years for the physics community to observe the first four quarks and become convinced that the quark model is fully valid. One year later the charm, top and bottom quarks have been discovered although the top quark could only be fully observed twenty years later, in 1995.
The quarks combine in groups forming so called hadrons, the most stable of which are protons and neutrons. Unlike the electrons, neutrons and protons, the quarks cannot be observed in isolation, they can only be studied within hadrons. The two types of hadrons are the baryons (combinations of three quarks, like the protons and the neutrons) and the mesons (one quark and one antiquark).
Another odd thing about the quarks is the fact that they have fractional electric charge values. Up, charm and top quarks have an electric charge value of +2/3e (e - elementary charge) while down, strange and bottom quarks have an electric charge of -1/3e. A proton is composed of three quarks, two up quarks and one down quark, so its electric charge value is 2/3 + 2/3 – 1/3 = +1 (positive charge value). The neutron consists of two down quarks and one up quark, so its electric charge value is 2/3 – 1/3 – 1/3 = 0 (neutral, no electric charge).
One of the latest theories regarding the dark matter implies that it could consist of mesons, combinations of one quark and one antiquark, thus particles with no electric charge.
An antiparticle (another interesting stuff that I missed), like the antiquark, is a particle that has the same mass as another particle but has opposite values for the electrical charge and magnetism. The interaction of a particle and its antiparticle results in annihilation and it is the ideal way of fully transform matter into energy according to one of Einstein’s most important equations: E=mc^2 (Energy equals Mass times Light-speed square). Collisions like this are now artificially created using the Large Hadron Collider or LHC in Geneva. On March 30, 2010, they managed to collide particles at energy of 7 TeV (Tera Electron-Volts), which is a huge milestone. This kind of collision happen all the time in the Universe (at higher energy) but that was the first time one has been created in a laboratory. The interpretation of the results will be available hopefully by the end of 2010.
A collision between a gram of matter and a gram of antimatter would produce almost as much energy as one thousand fuel tanks used to transport space shuttles on orbit would.
It is called dark because until now no one knows for sure what it is exactly. Dark matter is undetectable by emitted or scattered electromagnetic radiation because it does not consist of particles of which ordinary matter does (atoms), so it cannot interact with any devices. The only force that directly affects the dark matter and allows us to study it is gravity.
The concept of dark matter (formerly called missing matter) appeared when scientists concluded that the stars situated on the galaxies' outer rim travel too fast, and considering the galaxy’s total mass, its gravitational force should not be able to hold them on orbit. The only explanation was that the galaxy should contain far more mass that the one that can be observed. The same thing happened with star clusters and even galaxy clusters. The gravitational lenses also suggest that more mass than the one observed is needed in order be able to bend the light the way they do.
However, matter consisting of particles other than atoms is almost science fiction, and not only for amateurs but for scientists too. One other proposed explanation was that the gravitational force is still not fully understood and its current form must be incomplete. It happened before when Einstein proved that Newton was wrong, why can’t it be happening now? Therefore, scientists proposed that the gravity acts different on far distanced objects, as an exception for Einstein’s relativity. Few unsuccessful attempts have been made, but some scholars are still more or less skeptical.
Another theory regarding the true nature of the dark matter came as a consequence of the existence of parallel universes theory. Before Einstein, we lived in a three-dimensional space, and he introduced the forth dimension – time. It is possible that sometime in the future we will discover other dimensions and possibly another identical universe(s) around us (theoreticians do think about this seriously). If there is another universe out there, well, we might not be able to see it because we’re limited, but again, the gravity would shape it for us just the way it shapes the dark matter. This is when the ideea that the dark matter could in fact indicate the presence of another universe born.
Big Bang theory explains how the entire universe emerged from one tiny spot in space, in a very small fraction of a second (in fact, the whole matter was so concentrated in that spot that the space-time curvature made the concepts of time and space meaningless). Following logic, the science community believed that the expansion of the universe in slowing down due to the gravitational forces between objects in space, and that at some moment, the universe would stop or would begin to contract again in one tiny point (the Big Crouch theory). So the universe would not have a beginning or an end, but it would expand and contract forever.
That was the best theory we had, until we looked at the stars and galaxies with the proper tools and realize that every object in the observable universe is moving away from us and away from each other (except Andromeda galaxy, which our galaxy is on collision course with), the same way as the dots painted on a balloon “move” away from each other when the balloon is filled with gas.
As if this wasn’t enough to torment scientists’ mind, they also found that the universe expands at an accelerated speed, thus confirming the Big Bang theory. And nothing explains these mysteries better than the existence of another type of energy which acts as a gravitational pull but in the opposite direction. This unknown energy it is now called dark energy and it fills about 75% of the observable universe.