Profile cover photo
Profile photo
David Ratnasabapathy
I read a lot and I teach Math
I read a lot and I teach Math


Post is pinned.
Hi +Christof Harper,

Three years ago I insulted you in the comments to +Andreas Schou​ 's post here:

I am sorry.

I was rude where you were polite. I was intemperate, ignorant, and worse, blindly arrogant and dismissive towards you. My outburst was unprovoked and ruined a perfectly good discussion.

I'd have done better to listen than speak. Given that I commented I should have had the courtesy to respond intelligently when you engaged. At the very least I should have remained polite.

Thanks for reading.

David Ratnasabapathy
Add a comment...

Post has attachment

The Amazing Dr Baker

...She found that babies routinely received silver nitrate eyedrops to prevent blindness from gonorrhea. But bottles of the solution often became contaminated... Baker invented a foolproof sanitary solution: beeswax capsules, each containing enough solution for one eye. The capsules could not become contaminated and the drops inside could not evaporate. The method was soon being used around the world, and the rate of blindness in babies plummeted. ...
Add a comment...

Test post to see if g+ is sufficiently important to be blocked.
Add a comment...

Post has attachment
The UNIX Hater's Handbook
Is a hilarious detailing of the boobytrapped idiosyncracies of a much beloved family of OS's:

Here's a way to amuse and delight your friends (courtesy of Leigh Klotz).

First, in great secret, do the following:
% mkdir foo
% touch foo/foo~

Then show your victim the results of these incantations:
% ls foo*
% rm foo~
rm: foo~ nonexistent
% rm foo*
rm: foo directory
% ls foo*

Last, for a really good time, try this:
% cat - - -

(Hint: press ctrl-D three times to get your prompt back!)
Add a comment...

Post has attachment
The 1969 Easter Mass Incident
This story is too good to be true; but even if it isn't, if there were a collection of these I'd buy it in a heartbeat. I laughed and laughed and laughed.

Behold, the story of a priest who believed in the spirit over the literal.
Add a comment...

Post has shared content
I totally agree. An educated mind has a better chance of being an enlightened one.
Add a comment...

Should one tip when the service is bad?
Oh yes. would probably not go to the manager and request, say, an 8% reduction in the bill because the service was a bit sloppy.

If we wouldn't demand reductions from the manager, we shouldn't impose them on the staff.
Add a comment...

Post has attachment
Wikipedia's an excellent resource for science and math. Turns out it's so much more. Mysterious deaths, fascinating people, incredible idiocies...
Add a comment...

Post has shared content
It's the OnOff star from Vernor Vinge's A Deepness in the Sky!

That's a deeply disturbing book. It's got an all-too-plausible description of a slaver society based on mind control.
iPTF14hls, a Very Unusual Supernova Refusing to Die

An exploding star, named iPTF14hls, has erupted continuously for the last three years, and it may have had two other outbursts in the past, astronomers report in the Nov. 9 Nature. Such a tireless supernova could be the first example of a proposed explosion that involves burning antimatter in a stellar core — or it could be something new altogether.
None of the theories and hypotheses fully explain all aspects of this object.

To quote the first line of the letter published in the previously mentioned journal Nature: “Every supernova so far observed has been considered to be the terminal explosion of a star.” In summary, when a massive star blows itself up, it should remain dead. This is something astronomers have witnessed thousands of times before with absolutely no exceptions.

That is, until now.

“This supernova breaks everything we thought we knew about how they work,” said the study’s lead author Iair Arcavi, a NASA Einstein Postdoctoral Fellow at the University of California-Santa Barbara and Las Cumbres Observatory, in a press release (
“It’s the biggest puzzle I’ve encountered in almost a decade of studying stellar explosions.”

The star iPTF14hls was discovered in September 2014 by the Intermediate Palomar Transient Factory, and astronomers identified it as an exploding star in January 2015. It was thought then that it was a single supernova event (Type II-P) that would dim in about 100 days, but instead, it continued its eruption for more than 600 days while fluctuating in brightness at least five times. The brightness varied by as much as 50% on an irregular timescale, as if it was exploding over and over again.

As previously said, there is no known theory that explains the observation.

One hypothesis is that it could be the first example of an explosion that involves burning antimatter in a stellar core. That would cause the star to become extremely unstable, and undergo repeated bright eruptions over periods of years.
Another hypothesis is the pulsational pair-instability supernova (, a massive star that may lose about half its mass before a series of violent pulses begins. On every pulse, material rushing away from the star can catch up with earlier ejected material, producing bright flashes of light as it collides, simulating an additional explosion (see Supernova impostor: But that hypothesis does not explain the continued presence of hydrogen or the energetics observed.

► Image: This artist’s impression shows dust forming in the environment around a supernova explosion.
Credit: ESO/M. Kornmesser >>


► LCO Press Release>>

► Lawrence Berkeley National Laboratory (Berkeley Lab) Press Release>>

► Paper: Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star. Iair Arcavi, D. Andrew Howell, Daniel Kasen, Lars Bildsten, Griffin Hosseinzadeh, et al. Nature. 551, 210–213; 9 November 2017.doi:10.1038/nature24030>>

Further reading and references

► This star cheated death, exploding again and again>>

► This Star Went Supernova … And Then Went Supernova Again>>

► iPTF14hls>>

► Antimatter>>

#Universe, #Research, #Astrophysics, #Supernova
Add a comment...
Wait while more posts are being loaded