And for those of us who do not, can you elaborate as to why exactly?

I believe the story referenced is "At The Core", where stars at the core of the galaxy have gone supernova and thereby started a supernova chain reaction expanding outward from the core into the surrounding stars of the galaxy.

https://en.wikipedia.org/wiki/At_the_Core

In one of Niven's short stories an alien corporation hires a Human pilot to fly to the galactic core. It's a publicity stunt to demonstrate the speed and range of a new FTL drive. When he gets close to the core, his ship is almost fried by the radiation wave front coming from a chain reaction explosion of suns in the galactic core. This drives events in many of Niven's later stories.

The devastation won't reach 'Known Space' for thousands of years, but the alien Puppeteers that funded the trip are paranoid herbivores. They immediately start a mass exodus of their whole species out of the galaxy, causing a massive economic crash along with many effects on other plot lines.

Niven's Known Space future (and past) history is an amazing and incredibly influential achievement. Highly recommended. Most of it consists of collections of short stories and novellas written over decades, so it's very digestible.

While these books sound interesting, “amazing and incredibly influential achievement” sounds more like something someone might say about a President than a sci-fi author.

I can only speak for myself, but Larry Niven's wonderfully imaginative stories have influenced my thinking more than any president ever did.

Larry Niven is still relevant while Millard Fillmore is not.

And yet few have ever heard this Larry while Millard Fillmore maintains the distinction of being the president with the coolest name.

If only Spiro T. Agnew would have made it.

Larry Niven's most famous work Ringworld, inspired both of the massively popular games Magic the Gathering, and Halo: Combat Evolved.

I suspect that Niven and Fillmore have roughly equal name recognition, though, simply by the nature that Niven is still alive, and appears to be more consequential long term.

Magic? What is the link there?

While Larry Niven is most famous for his hard science fiction, in the traditional sense of the term, he also has a fantasy universe, with a decent introduction at https://en.wikipedia.org/wiki/The_Magic_Goes_Away In this universe, magic is a finite quantity, which gets used up. The modern world is mundane not because magic is impossible, but because it was all used up.

(It would be interesting if he ever wrote the story set in this universe, after the modern times, in which humanity gets out to space, and, uh, hey guyz, magic kinda... works out here... what the heck? It wouldn't necessarily take long to figure out what the deal is with Earth being a dead zone, but it would cause some interesting political upheaval as suddenly the sparse space colonies that nobody thought were worth anything and barely even worth the effort became industrial powerhouses as the only place where magic works... and not just the tame, dying magic of Niven's stories, but the original wild, abundant magic the stories claimed Earth initially had.)

Nevinyrral's Disk, at a minimum.

https://gatherer.wizards.com/Pages/Card/Details.aspx?multive...

The entire concept of mana being generated from land.

I have heard of Larry Niven and never heard of Millard Fillmore.

Being outside the US I never covered past US presidents in school.

Even if the US, he isn't someone who would be covered.

Probably fewer than 10% of Harvard graduates could tell you anything substantive about Millard Fillmore’s presidency. He isn’t covered here either.

I'm possibly only aware of Millard Fillmore because of the Infocom game "Bureaucracy" and oddly enough:

"Jerry Pournelle named Bureaucracy as his game of the month for October 1987, stating that he and Larry Niven became "engrossed""

I've never heard of Millard Fillmore before.

Likely more people (inside the US and outside too) are more familiar with Fillmore St. in San Francisco[1], which is named for President Fillmore, and its famous theater / music venue of the same name.

1: https://en.wikipedia.org/wiki/Fillmore_District,_San_Francis...

The galactic core exploding is a major plot point driving the Known Space series.

There another short story by Niven where someone gazing at the moon sees it get as bright as the sun. They quickly come to the conclusion that some horrific event will end life on earth as soon as the earth rotates towards whatever made the moon so bright.

It's a fun little romp.