John Moffat (physicist)
Canadian physicist and cosmologist, Professor Emeritus in physics at the University of Toronto and adjunct Professor in physics at the University of Waterloo.
A much faster speed of light in the infant universe solved the horizon problem and therefore explained the overall smoothness of the temperatures of the CMB radiation, because light now traveled extremely quickly between all parts of the expanding but not inflating universe.
In estimating the amount of dark matter, cosmologists developing the standard model have to make some rather strong assumptions about their observations.
Inflation itself proceeds at a speed faster than the measured speed of light.
This is the only sure way I know to counter the anti-Copernican idea that the universe is accelerating in our epoch - to get rid of the problem entirely!
This is an extraordinary time in the history of science, in that we cannot only theorize about the beginning of the universe, but actually study the celestial fossils of how it happened.
Hunting for elusive dark matter is now a multibillion dollar international scientific industry.
Indeed, there is a now a minority of cosmologists who question a beginning of the universe at all; instead they favor a cyclic model with a series of expansions and contractions.
Experimentalists dream of some spectacular discovery such as the proof of the existence of black holes to justify the more than eight billion dollars it has cost to build the LHC.
The eighteenth-century German philosopher Immanuel Kant had conjectured that Messier's nebulae were distant "island universes" outside our Milky Way galaxy, but many scientists in the early twentieth century disagreed.
Almost 30 percent of the total matter-energy budget is said to be composed of so-called cold dark matter and almost 70 percent of "dark energy," leaving only about 4 percent as visible matter in the form of the atoms that make up the stars, planets, interstellar dust, and ourselves. Such is the degree of discrepancy between theory and observations today.
To physicists such as myself, the huge amount of invisible dark matter needed to make Einstein's theory fit the astrophysical data is reason enough for exploring modified gravity theories.
It may be that ultimately the search for dark matter will turn out to be the most expensive and largest null result experiment since the Michelson-Morely experiment, which failed to detect the ether.
One truth we have been able to count on concerning scientific persuit over the centuries has been that only testable theories survive the intense scrutiny of experimental science.
When I was a student at Trinity College, Cambridge, in the 1950s, Sir Isaac Newton's presence was still almost palpable.
Today, like the elusive planet Vulcan in the nineteenth century, dark matter is accepted by the majority of astronomers and physicists as actually existing. Dark matter, although it has never been seen, is part of the generally accepted standard model of physics and cosmology, which also includes the big bang beginning of the universe.
Is the reader feeling confused about the status of the black hole information paradox and black holes in general? So am I!
Einstein entertained counterintuitive notions that allowed him to pull physics from the mechanistic, clockwork universe of the eighteenth century up into the twentieth century.
It is hard to understand how this infinitely dense singularity can evaporate into nothing. For matter inside the black hole leak out into the universe requires that it travel faster than the speed of light.
It is difficult to falsify the hypothesis of dark matter, because, as with Ptolemy's epicycles, true believers can always add additional arbitrary features and free parameters to overcome any conceivable difficulties that occur with the dark matter models.
Could it be, nevertheless, that Einstein's theory is wrong? Might it be necessary to modify it—to find a new theory of gravity that can explain both the stronger gravity and the apparent antigravity being observed today—rather than simply throwing in invisible things to make the standard model work?