97% of the observable universe is forever unreachable

The other day, I was reading a post by Ethan Siegel on his excellent blog, Starts With a Bang, about whether it makes sense to consider the universe to be a giant brain.  (The short answer is no, but read his post for the details.)  Something he mentioned in the post caught my attention. But … Continue reading 97% of the observable universe is forever unreachable

Complex life in the universe may be much rarer than previously thought

At least, according to a couple of astrophysicists: Complex life may be possible in only 10% of all galaxies | Science/AAAS | News. The universe may be a lonelier place than previously thought. Of the estimated 100 billion galaxies in the observable universe, only one in 10 can support complex life like that on Earth, a … Continue reading Complex life in the universe may be much rarer than previously thought

The size of the observable universe is complicated.

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.

Tegmark’s Level II Multiverse: bubble universes

I recently finished reading Max Tegmark’s latest book, ‘Our Mathematical Universe‘, about his views on multiverses and the ultimate nature of reality.  This is the second in a series of posts on the concepts and views he covers in the book.  Tegmark postulates four levels of multiverse.   In the first post of this series, I described Termark's Level I … Continue reading Tegmark’s Level II Multiverse: bubble universes

Where is the Earth located?

http://www.youtube.com/watch?v=8_l8CxIieVQ I enjoyed this video, but I wonder about Fraser's statement that cosmologists think if you travel in one direction long enough you'll eventually end up back where you are.  That is one model, but not the only one.  It depends on space being curved, and tests currently show it to be flat. Of course, … Continue reading Where is the Earth located?

Ask Ethan #12: How far is the distant Universe? – Starts With A Bang

Ethan Siegel's blog, Starts With a Bang, is one of the best science astrophysics blogs on the web. Ask Ethan #12: How far is the distant Universe? – Starts With A Bang. In this post, he tackles an issue I often see a lot of confusion over, even from science reporters.  When talking about extreme … Continue reading Ask Ethan #12: How far is the distant Universe? – Starts With A Bang