In past posts, when I've written about the expansion of the universe, I've generally referred to the rate of that expansion, the Hubble constant, as being around 70 km/s/megaparsec, that is, for every megaparsec a galaxy is distant from us, it's moving away at 70 kilometers per second faster. So a galaxy 100 megapasecs away … Continue reading Is cosmology in crisis?
I tweeted this yesterday, but it deserves a blog entry: Gravitational waves discovery now officially dead : Nature News & Comment. A team of astronomers that last year reported evidence for gravitational waves from the early Universe has now withdrawn the claim. A joint analysis of data recorded by the team's BICEP2 telescope at the South … Continue reading Gravitational waves discovery now officially dead
Marianne Freiberger reports on a discussion she had with Bernard Carr on whether or not multiverse theories are science. He has a suggestion for how we should classify these theories. With the possibility for indirect evidence in the future, maybe we shouldn't dismiss the multiverse as mere speculation, especially since it has many features that are … Continue reading Multiverse theories: “meta-cosmology”?
You can get background on what I'm talking about in this post here and here. Probably the best thing to do is let the experts weigh in on this. https://twitter.com/DavidSpergel/status/513848952513642497 https://twitter.com/seanmcarroll/status/513858867327823873 https://twitter.com/seanmcarroll/status/513869684647530496 https://twitter.com/AstroKatie/status/514040997139865600 It's interesting to note that the empirical evidence from BICEP2 has never been called into question, only the interpretation of that evidence. … Continue reading Cosmic inflation appears to have shifted from settled science back to speculation
The radius of the observable universe is often stated to be 46 billion light years. From a certain point of view, this is true, but I think it's a bit of a misleading statement. Occasionally you also see people say that the observable universe is 13.8 billion light years in radius, which is also true, from … Continue reading The size of the observable universe is complicated.
Stan Hummel called my attention to, and asked for my thoughts on this article: Big Bang Theory Challenged --"The Universe Should Not Have Lasted for More than a Second". British cosmologists are puzzled: they predict that the universe should not have lasted for more than a second. This startling conclusion is the result of combining the … Continue reading “The Universe Should Not Have Lasted for More than a Second”: The limitations of scientific theories
Think of the Big Bang, and you probably imagine a moment in time when matter, energy and space itself all burst into existence at once. Yet many astrophysicists now believe that the “Big Bang” was actually two distinct events: first the inaugural instant of space and time, and second the generation of most of the … Continue reading The Big Bang’s Identity Crisis – The Nature of Reality
Nature has an article up describing the problems with the BICEP2 results that are now being identified by various scientists. It's actually the second one I've seen them publish on this. The astronomers who this spring announced that they had evidence of primordial gravitational waves jumped the gun because they did not take into proper … Continue reading Growing doubt that gravitational waves were actually detected
Dan Kahan has an interesting post showing that when Americans are asked the, "Did humans develop from earlier species?" question, it matters how it is asked. As it's usually asked, when people answer, they are often asserting a religious cultural identity. But if it is asked with the qualifying "according to the theory of evolution", … Continue reading Americans may be more scientifically literate than evolution questions show
Ethan Siegel has an excellent post up contemplating the various models of the timeline of the universe. It’s only human to ask the most fundamental of all questions: where did all this come from? And we like to think we know the answer; it all came from the beginning. But if you think about it … Continue reading The theoretical preference for a timeless and eternal reality