Dark Matter: the Invisible 23% of the Universe
“Dark Worlds,” by Jonathan Feng and Mark Trodden, is an article from the November 2010 issue of Scientific American. This article discusses how scientists explain the existence of dark matter, even though it is indeed invisible. Dark matter can be indirectly seen through its gravitational effects on bodies such as planets and stars. For example, if light in space is inexplicably distorted, dark matter may very well be to blame. Although it is invisible, it has gravitational force, may have weak nuclear force, and there may also be other possible dark forces that are currently unknown. Dark matter weighs six times normal, baryonic matter, which makes up only 4% of the universe. Dark matter is made up of particles which very rarely interact with baryonic matter or even other nonbaryonic matter, which comprises a whopping 23% of the universe. Astoundingly, dark energy is said to represent 73% of the universe, where space that looks empty could be holding much energy.
On another note, WIMPs are ‘weakly interacting massive particles’ that react to the weak nuclear force and gravity. What is hypothesized about the weak nuclear force is that baryonic force-carrying particles, W and Z, are heavier than they ought to be, so something must be acting on them, i.e. the weak nuclear force. These force-carrying particles such as W and Z are known as these WIMPs, which were created by the big bang. The big bang caused many particles to collide so very high in energy; this both created and sometimes destroyed these WIMPs. An interesting fact is that all the WIMPs that existed 10ns after the big bang still exist today, no more, no less!
Physicists have even went as far as to calculate the number of WIMPs that are still with us today, and this precise number exactly accounts for the dark matter today. Another interesting possibility is that particles called Super-WIMPs are also involved in explaining missing mass in the universe. WIMPs may have decayed into these Super-WIMPs, which are hypothetically particles that are akin to WIMPs except in that Super-WIMPs exert NO weak nuclear force. Their gravitational exertion may still be seen in their impact on galaxies’ shapes and how these Super-WIMPs bend/stretch them with their pulling. Interestingly enough, these Super-WIMPs can explain why the universe has less visual lithium than anticipated.
Dark matter is observed through its gravitational effects on bodies in space or even in the laboratory. There is six times as much dark, nonbaryonic matter than normal, baryonic matter in the universe. Discovering evidence for WIMPs is very much at the forefront in astrophysics today, where scientists aim to find these particles’ annihilation, direct detection, and production. Annihilation is where two WIMPs collide and destroy each other, leaving remnants that consist of electrons, antielectrons/positrons, and neutrinos. Direct detection aims to pinpoint instances where WIMPs bump into particles and transfer their energy. Cryogenics slows molecular vibrations, so that this recoil (energy transfer) may be observed and documented. Finally, the goal in production is to synthesize WIMPs with particle colliders like the Hadron Collider, colliding protons with great speed and energy in the hope of creating a WIMP. This would be seen through protonal collisions where mass, speed, and energy all disappear from these protons in an instant.
Posted by Derek Melzar (2).