
Not long ago, the center of the Milky Way exploded - dnetesn
https://phys.org/news/2019-10-center-milky.html
======
mannykannot
When this was first noticed (2013) I recall statements (possibly speculative)
that the irradiated part of the Magellanic Stream might have glowed brightly
enough to be visible in the night sky. If so, it would have subtended about
half a degree, about the same width as the moon and the sun.

~~~
ianai
And here we are stuck with just a sun and moon!

------
rbanffy
I guess that's why we won't be hearing radio signals from the Magellanic
clouds...

Now, seriously, what would be a safe distance for an Earth like planet to be
from such an unlucky event?

------
andyljones
Paper: [http://www.physics.usyd.edu.au/~jbh/share/Papers/JBH-
Ionizat...](http://www.physics.usyd.edu.au/~jbh/share/Papers/JBH-Ionization-
Cones-Oct19.pdf)

------
FrameworkFred
Given that we're able to aim telescopes at things that are billions of light
years away, I wonder how close we are to being able to see the reflection of
such a thing when it actually happens on some celestial body 3.5 million light
years away.

~~~
ljf
I remember as a child thinking I had fixed time travel (in a very limited
sense) when I wondered why we didn't just stick a bunch of mirrors far far
away, and then aim them back at the earth and use telescopes to look back at
the dinosaurs etc.

While that wouldn't work for heaps of reasons, I like your idea. I guess the
issue would be discerning 'when' such a thing happened, and finding the right
item to look back at, which would be a difficult challenge...

~~~
jerf
You need natural mirrors, because as others have pointed out, they have to
already be there, you can't get ahead of the light to put them there.

It has been suggested that black holes could provide this mirror, but it
requires resolving not just something the size of Earth, but something much
_smaller_ , at a distance of 30 million light years +. Unfortunately you
actually start hitting up against the limits of spacetime's resolution itself
fairly quickly. But at least in principle, it is possible that some lucky
photon has bounced off a dinosaur, and has traveled all the way out there, and
all the way back to Earth, just now, that if you knew where to look in the
sky, perhaps such a photon might even enter your eye now. Or perhaps there is
some human out there who really has "seen" the dinosaurs. But you'd never
really know.

~~~
klank
What are these "limits of spacetime's resolution" you speak of?

Beyond speculation, I'm not aware of anything showing spacetime to be
discrete.

~~~
fmihaila
> What are these "limits of spacetime's resolution" you speak of?

> Beyond speculation, I'm not aware of anything showing spacetime to be
> discrete.

It is a prediction of loop quantum gravity [1]:

 _In 1988, Carlo Rovelli, Lee Smolin, and Abhay Ashtekar introduced a theory
of quantum gravity called loop quantum gravity. In 1995, Rovelli and Smolin
obtained a basis of states of quantum gravity, labelled by Penrose 's spin
networks, and using this basis they were able to show that the theory predicts
that area and volume are quantized. This result indicates the existence of a
discrete structure of space at very small scale._

[1]
[https://en.wikipedia.org/wiki/Carlo_Rovelli#Loop_quantum_gra...](https://en.wikipedia.org/wiki/Carlo_Rovelli#Loop_quantum_gravity)

~~~
jerf
It's a prediction of other things, too. Even just sheer every-day quantum
mechanics sets a limit, too; eventually you're asking to nail down a photon's
origin with so much precision that you lose the frequency or something, things
you don't normally think about even in the most extreme astronomy today, but
become relevant when discussing bouncing photons around a black hole 30
million light years away.

~~~
klank
Modern QM formalization doesn't predict a discrete spacetime. Or, if it does,
nobody has been able to demonstrate this, to my knowledge.

------
facethrowaway
I am guessing this would lead to solar system-scale destruction? Putting a
base on Mars doesn’t seem like it would do much to counter such an event if it
headed our way?

~~~
hoorayimhelping
From my understanding, something that can wipe out the entire solar system at
once is highly unlikely.

Huge bursts of concentrated energy coming out of black holes are usually tight
beams of high energy particles and light (x-rays, gamma rays) moving very fast
and aligned with the object's poles. The focused beam of energy is what is
deadly to life. If it's not tight and focused and moving fast, the energy
dissipates out into space.

The solar system is huge and extends in three dimensions. A burst of energy
that hit earth directly could miss Mars (or the moon, or the space around the
earth and the moon) entirely. To sterilize a specific planet, the event has to
be close (within like 10,000 light years I seem to remember reading) and the
poles of the object undergoing the event have to be pointing at the planet.

~~~
simonh
If the black hole was only 1,000 light years away, and the angle of divergence
of the beam was only 0.1 degrees, by the time the beam hit our solar system it
would be about 2 light years across, or 126,000 AU.

Compared to interstellar distances, our solar system is tiny.

------
jwr
For those of us who read Larry Niven's sci-fi novels, this headline is… both
amusing and somewhat scary.

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

~~~
simonh
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.

~~~
vonseel
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.

~~~
dwoozle
Larry Niven is still relevant while Millard Fillmore is not.

~~~
frogpelt
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.

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

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

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

~~~
perl4ever
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""

------
a_t48
Does 3.5M years ago count as “not long ago” in astronomy time scales?

~~~
rbanffy
In cosmological terms, it's more like "earlier today". Our ancestors were
already walking around, talking to black monoliths and crushing skulls by
then.

~~~
ifdefdebug
I hate that movie.

~~~
unnouinceput
Which movie?

~~~
jes5199
“2001, a space odyssey”. post above is making a reference to the opening scene

------
keyle
They said it would have been a massive event, but what would our ancestors
have seen?

------
nerdponx
They said the flare lasted 300,000 years, but how quickly does something like
this start? How fast does it go from "nothing" to "full strength"?

Also if there was any form of life orbiting a star in the path of this flair,
is it safe to assume that said life is no longer alive? At least if that life
resembles us in its tolerance (or lack thereof) for radiation.

~~~
yourapostasy
> Also if there was any form of life orbiting a star in the path of this
> flair...

Based upon a couple other articles I read [1] [2], it sounds unlikely there
were other galaxies or smaller structures in the path of this flare. I only
see references to a very directional cone at the poles of the Milky Way, and
the cone only intersects a trail of gases left behind by the Magellanic
Stream.

Were there somehow orphaned planets, solar systems or smaller galaxies in the
path of those cones not mentioned in the articles however, then the gamma
rays, X-rays and highly ionizing gases in those cones of energy would
certainly strip away most if not all of the atmosphere of any Earth-like
planet, and kill all forms of life as we know it unless it was in some kind of
weird, tidally-locked configuration that kept one side always facing the
originating, ejecting side of the cone.

These flares would make a great plot device setup for a story in the Xeelee
Sequence or /r/HFY. We find out the flares are deployed as weapons, used as a
kind of galactic-scale sawed-off shotgun against another galaxy. Or the flares
are galactic-grade energy reactor experiments gone horribly awry, and are the
cause of one Great Filter at the Kardashev Type-III scale.

[1] [https://www.sciencealert.com/something-in-the-centre-of-
our-...](https://www.sciencealert.com/something-in-the-centre-of-our-galaxy-
colossally-erupted-3-5-million-years-ago)

[2] [https://earthsky.org/space/explosion-milky-way-center-
seyfer...](https://earthsky.org/space/explosion-milky-way-center-seyfert-
flare-magellanic-stream)

~~~
jacobush
Is there a name for some kind of inverted Kardashev scale, where higher
civilizations decide to slow down and go miniature, conserving as much energy
and information as possible?

Possibly as a) some kind of bet to hide from other civilizations and b) to
delay the heat death as long as possible.

~~~
yourapostasy
My go-to entry point for exploring those kinds of questions was Isaac Arthur.
He goes into the Kardashev scale [1], dying Earth [2], dying stars [3],
farming black holes [4], and going past iron stars [5]. A Boltzmann Brain's
description bears remarkable similarity to the Judeo-Christian concept of God
before time begins, and has been fertile ground for ruminations [6], though
none with any verifiable claims backing them in our current knowledge of
physics [7].

Now if we could only restructure our implementation of capitalism to be pinned
to advancements towards resolving physics questions to survive those kinds of
timescales and challenges instead of locked down to a single planet's worth of
baryonic matter and cognitive capacity...

[1]
[https://www.youtube.com/channel/UCZFipeZtQM5CKUjx6grh54g](https://www.youtube.com/channel/UCZFipeZtQM5CKUjx6grh54g)

[2]
[https://www.youtube.com/watch?v=p58yFf7aZsM](https://www.youtube.com/watch?v=p58yFf7aZsM)

[3]
[https://www.youtube.com/watch?v=GpYGMIZ9Bow](https://www.youtube.com/watch?v=GpYGMIZ9Bow)

[4]
[https://www.youtube.com/watch?v=Qam5BkXIEhQ](https://www.youtube.com/watch?v=Qam5BkXIEhQ)

[5]
[https://www.youtube.com/watch?v=Pld8wTa16Jk](https://www.youtube.com/watch?v=Pld8wTa16Jk)

[6] [https://turingchurch.net/does-god-emerge-from-boltzmann-
brai...](https://turingchurch.net/does-god-emerge-from-boltzmann-brains-in-
the-fabric-of-reality-7583c3dac485)

[7]
[https://www.reddit.com/r/AskPhysics/comments/6btjud/what_if_...](https://www.reddit.com/r/AskPhysics/comments/6btjud/what_if_there_is_a_god_and_its_a_boltzmann_brain/)

~~~
jaaron
Great list! I'm bookmarking this.

------
_bxg1
They probably would've mentioned this in the article were it the case, but I
wonder if it was visible at all in the night sky? We can see part of the Milky
Way, after all. I guess there wouldn't have been writing yet but could such a
thing have made it into oral history? Was there even oral history yet?

~~~
onychomys
No oral history, sorry. 3.5MYA, we were still Austropithecenes, basically as
smart as a modern day chimp or gorilla, but bipedal. The little numbers in the
tree here show divergence time:

[https://en.wikipedia.org/wiki/Australopithecus#Phylogeny](https://en.wikipedia.org/wiki/Australopithecus#Phylogeny)

------
kristianp
No mention of what observations they made to come to this conclusion. Not in
the press release I guess.

------
Faction
They said the flare lasted 300,000 years, but how quickly does something like
this start? How fast does it go from "nothing" to "full strength"?

------
leemailll
So for laymen as us, how far is the center from us in light years?

~~~
andyjohnson0
26,490 ± 100 light years or 8,122 ± 31 parsecs

[https://en.wikipedia.org/wiki/Galactic_Center](https://en.wikipedia.org/wiki/Galactic_Center)

------
Yuval_Halevi
So basically we are not on the way of bursts exploding from the poles of the
center, we are perpendicular to the bursts trajectory?

~~~
tejtm
normally

