Are astronomers convinced that dark matter is the answer?

Are astronomers convinced that dark matter is the answer? Is it likely that there is a simpler alternative theory to help explain why general relativity fails at galactic scales? I will answer the second question first: no. All the simpler alternatives have been tested and they fail to explain all the observations. It is very … Read more Are astronomers convinced that dark matter is the answer?

Is space expanding faster than the speed of light?

In the November/December 2015 edition of StarDate Magazine, I quote Merlin as follows, “Astronomers see the earliest galaxies as they looked about 13 billion years ago. Since the time when those galaxies emitted the light that astronomers now detect, though, space itself has expanded, so the galaxies are now 48 billion light-years away.” If those … Read more Is space expanding faster than the speed of light?

Can we find exoplanets (and possibly extraterrestrial life) by beaming low-frequency waves towards them?

If X-ray and radio beams can emit from black holes and the like in interstellar space, can lower frequency waves on the middle to low end of the spectrum be emitted from high-powered beams on Earth and then detected by telescopes – like a sub pinging to its target – in order to search for … Read more Can we find exoplanets (and possibly extraterrestrial life) by beaming low-frequency waves towards them?

Immediately after the Big Bang, did light stop at the edge of the Universe?

Can light travel without a carrier such as a gravitation field? Light does travel via a carrier, in the same way gravity does. If we think about light as a continuous phenomenon, this carrier is the electromagnetic field, just as gravity is “carried” by a gravitational field. If we think about light as a particle, then … Read more Immediately after the Big Bang, did light stop at the edge of the Universe?

How likely is it that the Universe is closed, rather than flat?

Based on the 2001 WMAP results, the Universe is flat with a 0.4% margin of error. But what exactly are the chances of the Universe being finite but unbounded? I know it’s an unanswered question in cosmology, but is there any estimate? The short answer to this question is that the Universe cannot be both flat and … Read more How likely is it that the Universe is closed, rather than flat?

How is HETDEX different from other dark energy surveys?

In the November issue of Scientific American, there is an article on the Dark Energy Survey, “Seeing in the Dark.” How is this survey similar to – or different – from HET-DEX (besides being in Chile instead of Ft Davis)? As the Scientific American article states, the five-year Dark Energy Survey (DES) will cover 5000 square degrees … Read more How is HETDEX different from other dark energy surveys?

Does light accelerate when approaching the edge of a black hole?

Does the speed of light increase as it nears the event horizon due to the influence of a black hole’s gravitational pull? The short answer is no, the speed of light is always the same. To explore the subtle aspects of this question, we will consider it in the context of Albert Einstein’s general theory of … Read more Does light accelerate when approaching the edge of a black hole?

Does the matter inside a black hole have temperature and density?

Does the degenerate matter inside a black hole have a temperature, or is it so compact it’s functionally at absolute zero? Also, if event horizon scales with mass, does matter inside the event horizon have a specifiable density? Thanks for a very intriguing question. The basic answer is that no one knows and that it … Read more Does the matter inside a black hole have temperature and density?