A product of the Dark Side
Sombrero Galaxy Credit: NASA/ESA and The Hubble Heritage Team (STScI/AURA)
Why is dark matter assumed to exist in the cosmos? From reading news headlines you would think it has been clearly identified and that we now know so much about this once elusive stuff. It has been sought in many different laboratory experiments for more than four decades now, but never found. Why then are astronomers so confident it is out there? Let me try to put this into context and I hope it will become clear. Continue reading
Keeping Science in Darkness
Sometimes the existence of a new ‘particle’ in physics has been proposed long before it was discovered by an experimentalist in a lab experiment. Some examples of this are the anti-electron (positron) proposed by Paul Dirac in 1927 and discovered in 1932; the neutron, predicted by Ernest Rutherford in 1920, and discovered by James Chadwick in 1932; the pi meson discovered by C. F. Powell’s group in 1947 but predicted by Hideki Yukawa in 1935; and in 2012 a particle was detected exhibiting most of the predicted characteristics of the Higgs boson, which was predicted by Peter Higgs and five others in 1964. For their prediction, Peter Higgs and François Englert, were awarded the Nobel Prize in Physics in 2013.
In astrophysics such a new ‘particle’ could be the planet Neptune. Its existence was mathematically predicted by Urbain Le Verrier before it was directly observed in 1846 by Johann Gottfried Galle at the Berlin Observatory. (There was some dispute over credit as John Couch Adams from Cambridge had separately made predictions on the position of the planet.)
Those predictions, which led to successful outcomes, were based on the established laws of nature; for Neptune it was Newton’s gravitational theory, and for particle physics, the newly developing quantum theory. Continue reading
The Standard Model of particle physics (SM) has been very successful at describing the elementary particles and the forces that bind them together. However, the Standard Model presents some significant problems for big bang theorists. This is because the SM does not contain any Dark-Matter particles, and the neutrinos in it are described as exactly massless. Which means that in its present form, it is in clear contradiction with the big bang model as required by various observations.
Those observations have led to the need to include Dark Matter in the standard (ΛCDM1) big bang model, particularly during the period of nucleosynthesis, just after the big bang beginning when the light elements were allegedly formed from hot hydrogen. Therefore, the Standard Model of particle physics is in stark disagreement with the requirements necessary for the formation of the first elements in the alleged big bang.
Where are the Dark-Matter particles?
All challenges to the standard ΛCDM big bang model have been met and overcome, so far, by assuming ‘unknowns’ particularly Dark Matter and Dark Energy, wherever and whenever needed. Astronomical observations have led big bang astronomers and cosmologists to look for these new unknown Dark-Matter particles to solve many of their problems resulting from such observations; for example, the formation of stars, galaxies and galaxy clusters, the testing of the big bang model with type Ia supernova measurements, the angular power spectrum of the CMB anisotropies, galaxy rotation curves, and in particular, as focussed on here, Big Bang Nucleosynthesis (BBN).2 Continue reading
Dark sector physics and the sterile neutrino
Abstract: And God saw the light, that it was good: and God divided the light from the darkness. (Genesis 1:4) In this modern era darkness has developed a new meaning. From various problems in cosmology a need has developed to postulate the existence of unknown types of energy and matter from the dark side. These are sought for in the dark sector of particle physics and in the description of the expanding universe acted upon by gravitation. Besides dark energy and dark matter, now a new dark component is being promoted—dark radiation—in the form of a sterile neutrino, which does not interact with electromagnetic radiation or matter except via gravitation. This has come about because of the dichotomy that has occurred when the total mass of the universe has been measured using two quite different methods. But this new development underlines the problems that have developed in cosmology, especially when the model (paradigm) being considered is a clear departure from the historical account in Genesis. Article first published by Answers Research Journal 7 (2014):357–361. PDF available here.
Is something dark going on in cosmology? If you thought dark energy and dark matter were hard to understand (and justify), now a new component has been added to the dark side—dark radiation.
When astrophysicists measure the total amount of matter in the universe using different methods, and different data sets, it has been found that they get quite different answers. Continue reading