In China, there is a popular nursery rhyme: Once upon a time there was a mountain, in which there was a temple, in which there was an old monk telling a story to a little monk. The story he was telling is: Once upon a time there was a mountain, in which there was a […]
Self-similarity: Properties and Applications Read More »
February 18th 2021, 12:55 PST. A room in California erupts in cheers and applause as mission control watches its robot land on another planet. After years of preparations and almost seven months of space travel, Perseverance arrived safe and sound on the Red Planet, ready to study its environment for a planned duration of two
Persevering with Mars Exploration Read More »
Last week’s blog post was entitled To be MAD or not to be MAD. In it, my colleague Doosoo Yoon did a good job of discussing two models used to describe the accretion disks of matter flowing onto a black hole. These models started a discussion in our research group meeting this week for a
To be MAD or not to be MAD: problematic naming conventions in astronomy Read More »
Infalling on to the black hole may drive materials crazy. How on earth can they keep their sanity while all bodies undergo extreme gravity? These days, most researchers who are simulating an accreting flow around a black hole choose the condition of the accretion disc between the “SANE” and “MAD”. Now you may think that
To be MAD or not to be MAD Read More »
Radio galaxies are a class of active galactic nuclei that shine very brightly at radio frequencies but also radiate across the entire electromagnetic spectrum too. Powered by accretion of matter onto a central fast-spinning supermassive black hole, radio galaxies can display extended radio structures- jets. Jets emit radiation strongly at radio frequencies and can propagate
The curious case of FR0s: The relatively new class of radio galaxy Read More »
This is second part in the series of posts about Spaghettification. In this part we go over the idea of how gravity squeezes objects. We will also briefly discuss how to make tidal forces stronger. Squeezing Now let’s rotate the rod so that it is oriented with both ends equally distant from the Earth, while
MasterChef Universe : Spaghetti(fication) with Black Holes (Part II) Read More »
Can black holes make spaghetti? Like Obama, black holes would reply ‘Yes we can’! To top that off they can make spaghetti out of anything – using their ‘gravitational machinery’. In this three part series we will see how black holes employ gravity to do so! Before we go exploring black hole’s ‘spaghetti skills’, in
MasterChef Universe : Spaghetti(fication) with Black Holes (Part I) Read More »
In part II we saw that in a non-rotating black hole, the spatial and temporal coordinates are exchanged. Now we can take a step further, to consider the case of a rotating black hole. The line element in such spacetime has very complicated coefficients, but we don’t need the specific expressions here. So let’s just
Can you Discriminate between Space and Time? (Part III) Read More »
In part I we showed that space and time coordinates lead to different types of interval, spacelike and timelike respectively. Hence if we are given a line element expression in terms of any coordinates, we can figure out which of the coordinates are spatial and temporal, by looking at the sign of their coefficients. The
Can you Discriminate between Space and Time? (Part II) Read More »
What is the universe? All of space and time along with their contents. The unity of space and time is well-embodied in its Chinese term: Yu Zhou, where “Yu” means all of space and “Zhou” means all of time. However, what is space and what is time, and what is their difference? This is an
Can you Discriminate between Space and Time? (Part I) Read More »
