The most important discoveries in physics of the last 50 years are Dark Matter, and so-called Dark Energy.
The two most precise methods to evaluate the accelerated expansion of the Universe disagree by 9%. This surfaces from a recent 2016 paper. I am astounded by the fact that different methods agree so much.
A paper detailing the discrepancy, reported on the pre-print server Arxiv in April by Adam Riess of the Space Telescope Science Institute in Baltimore, Maryland, and colleagues, accepted by The Astrophysical Journal, reveals the slight discrepancy between the methods we have of measuring the expansion of the universe.
One method looks at dimples in the cosmic microwave background (CMB), a glow supposedly left behind by the hot, early universe just a few hundred thousand years after the alleged Big Bang. Space-based observatories like NASA’s WMAP and ESA’s Planck have measured small fluctuations in temperature in the CMB. Assuming we understand the physics in extreme detail, the size of these fluctuations let physicists calculate how fast the universe was expanding when the universe began, some 13.7 billion years ago.
The other method measures how distant galaxies appear to recede from us as the universe expands, using stars and supernovae of type Ia, which have a known brightness to estimate the distance to those galaxies. These Type Ia supernovae measurements led to the discovery of dark energy, and earned Riess and other physicists in Berkeley and Australia a Nobel prize in 2011.
The discovery of Dark Energy was astounding (although rumors existed since the 1970s). The physics established in the early Twentieth Century did not predict Dark Energy anymore than Dark Matter (Dark Matter was indirectly observed around 1934, but mainstream physics obstinately refused to pay attention for many decades… And still does not, on the theoretical side).
In the case of Dark Matter, it is hoped by the Standard Persons of the Standard Model, that a mundane, anticipated explanation will surface, such as SuperSymmetry (“SUSY”). SUSY would provide for plenty of mass, because it adds plenty of particles (one for each existing particle). SUSY assumes a perfect symmetry between bosons and fermions.
But I don’t believe very much that SUSY, even if it existed, would explain Dark Matter, for a number of reasons. Somehow the mass of the Super Partners would have to add up to ten times the mass of everyday matter. That’s weird (to me). Even worse, SUSY does not explain why Super Partners would get spatially segregated, as Dark Matter is (as far as I know, only my own theory explains this readily).
Instead I believe an obvious logical loophole in Quantum Physics will provide (plenty of) Dark Matter. And it makes the observed spatial segregation between Dark Matter and normal matter, obvious. One could call that little pet of mine, the Quantum Leak Theory (QLT).
I do not see a natural explanation for Dark Energy. Nor do any of the established theories. Actually, Dark Energy is not described well enough to even know what is really going on (different scenarios are known as “Einstein Cosmological Constant”, or “Quintessence”, etc.).
Yet, it is imaginable, at least in my own theory of Dark Matter, that the mechanism creating Dark Matter itself could also produce Dark Energy. Indeed the QLT implies that long-range forces such as gravity change over cosmological distances (a bit like MOdified Newtonian Dynamics, MOND).
To come back down at the most prosaic level: supernovae distance measurements depend on knowing the distance to nearby pulsing stars very precisely (such as the Cepheid RS Puppis depicted above). The European Space Agency’s Gaia mission, an observatory launched last year, which is measuring the distance to 1 billion Milky Way stars, should help.
Many other telescopes will soon come on-line. Astronomy leads physics, just as it did, 25 centuries ago. Nothing beats looking out of the box, and peering in the dark universe.