| The universe is expanding at an increasingly faster | | | | from the core of galaxies was moving as fast or |
| rate, and much of it we cannot "see." Current | | | | faster than the matter near the core. This was |
| explanations for these two phenomena gave rise to | | | | opposite to what was expected. Studying these |
| terms such as dark energy and dark matter. The | | | | "rotation curves" in many galaxies revealed that this |
| former is very mysterious and little is known about | | | | was happening everywhere. The cause is believed to |
| its nature, and the latter is understood a little more. | | | | be a huge amount of mass acting gravitationally that |
| In 1999 I attended a talk on the observed | | | | isn't detectable. This "missing" mass obviously doesn't |
| acceleration in the rate of expansion of the universe | | | | interact with electromagnetic energy and seems |
| at Harvard University. Dark energy is believed to be | | | | completely transparent. That is why we call it dark |
| responsible for this accelerating expansion, and seems | | | | matter. |
| to permeate all of space. Just by virtue of the void | | | | Some of this dark matter is accounted for by |
| of this "space," it may be filled with a constant | | | | ordinary types of matter containing atoms. This |
| energy that acts repulsively, sort of a powerful | | | | baryonic form includes candidates like brown dwarfs, |
| negative pressure. This is typically referred to as the | | | | gas that is not luminous or glowing, and Massive |
| cosmological constant. Quintessence is a scalar field | | | | Astrophysical Compact Halo Objects (MACHOs) such |
| quantity in quantum mechanics that serves as | | | | as black holes and neutron stars. The vast majority |
| another proposed form of dark energy. The | | | | of dark matter, however, is considered nonbaryonic. |
| difference is that the energy density varies in both | | | | This form includes Weakly Interactive Massive |
| time and space. Of all the mass-energy throughout | | | | Particles (WIMPS), such as neutrinos and other |
| the entire universe, dark energy accounts for nearly | | | | hypothetical elementary particles. Since their presence |
| 3/4 of the total. | | | | can only be inferred from gravitational effects on |
| In the mid 70's, a world-renowned woman | | | | visible matter, these elusive dark components of the |
| astrophysicist, Dr. Vera Rubin, found that the visible | | | | universe are very little understood. |
| matter (stars, gas and dust) spreading further out | | | | |