# Revealed: Milky Way's shocking cannibalistic dark past – it gobbled a whole dwarf eons ago

The Milky Way was formed after it engulfed a dwarf galaxy known as Gaia-Enceledus 10 billion years ago, astroboffins have suggested. The very idea is discussed in a paper, published in Nature Astronomy on Monday, that describes our galaxy’s violent past. The Milky Way began as a blob of stars roughly 13 billion years ago. …

1. #### Shame the timing's not quite right...

"Two thousand million or so years ago, at the time of the Coalescence, when the First and Second Galaxies were passing through each other and when myriads of planets were coming into existence where only a handful had existed before, two races of beings were already old; so old that each had behind it many millions of years of recorded history." - E. E. Smith

2. #### Why are there 3 dimensions?

A simple question. That magic number 3, why?

1. #### Re: Why are there 3 dimensions?

It's where practicality meets parsimony.

(I hope I don't regret this.)

1. #### Re: Why are there 3 dimensions?

It's a question I'm asking, not answering. Not some sort of trap.

Why 3 dimensions, why the observed properties?

a) We observe 3 dimensions.

b) Those dimensions appear independent of each other, e.g. a force along X independent of Y and Z.

c) Two can interact, independent of the third, e.g. a force or motion along XY independent of Z.

d) All three can interact, i.e. forces and motion along some XYZ direction

e) They are equal in scale or are measured as equal. A force along X behaves the same as a force along Y, and as a force along Z.

f) They are arbitrary oriented. You can pick any axis and align the other two and the rules above all works regardless of the direction of your first axis.

g) They are bi-directional, a force along X could be along -X, a motion along Y can travel -Y, Z with -Z, XY forces can all be reversed, ever push can have a pull.

-----

Time is a parameterization of motion over space, argued in a comment below. From which follows :

k) all 3 dimensions can be parameterized for motion over space the same way. i.e. time operates in *all* dimensions. You cannot have a dimension independent of time because it would violate d).

So why 3? It's easy to define the observed properties, but why are they?

If you have a model that creates property e), you might then wonder if it doesn't also need to create property b) and may also create a). So I ask.

Why would you regret asking?, the worst you'll get is someone quoting dead people as fake assumed authority. Insecurity not intellect.

Claptrap314 made some comments which caused me to google, which leads me to an awfully familiar thing. I've googled the wazoo out of twisting, topology, prime-number, knowing there will be an entire field of topology that already examined it, but that is the first time that paper has popped up.

1. #### Re: Why are there 3 dimensions?

I didn't expect that it would be a trap. Usually someone uses a hook like that as an excuse to spout off their ignorant, ill-considered, piss-poor excuse of a hypothesis as The One True Answer The Established Authorities Deny.

I can however respect you simply asking a question. Unfortunately, though, I don't think you've really advanced a discussion by stating your list of observations, since they're fairly self-evident. Would you like to respond to my conjecture instead?

1. #### Re: Why are there 3 dimensions?

Forget it. I've just read your responses below and you fit the pattern of someone spewing word-salad bollocks.

2. #### Re: Why are there 3 dimensions?

Maybe it only seems magical to us because we're 3 dimensional?

1. #### Re: Why are there 3 dimensions?

@"Maybe it only seems magical to us because we're 3 dimensional?"

How would you limit a three dimensional thing to only seeing the three dimensions that define it?

Consider flat world. It is 2D. To move from in-front of Bob to behind Bob, you have to pass above or below Bob. If you disappeared and re-appeared behind Bob, the rules of 2D space have been violated. Even if Bob cannot see the extra dimension, Bob would notice the breakage of the rules of his space.

So, look around. Where are the flywheels that disappear and reappear? The galaxies that spin in more dimensions.

They don't exist.

How exactly do you gatekeep that extra dimension to stop properties of 3D space leaking into and out of it, and how would it interact with 3D space if there can be no overlap in those forces and motions?

Dimensions {x,y,z,n} but no force and no motion in {x,n} or {y,n}, or {z,n}....

1. #### Re: Why are there 3 dimensions?

Consider flat world. It is 2D. To move from in-front of Bob to behind Bob, you have to pass above or below Bob

In a 2D world there is no above or below, those dimensions don't exist. You would have to go around Bob in one of the 2 dimensions. Or invent a hyperspace drive.

3. #### Re: Why are there 3 dimensions?

One of the great WHYs, there. Mathematicians (okay, topologists) note that three dimensions is the only one in which the linking number and the self-knotting number are the same. (1 in each case). Given the unreasonable predictive efficacy of mathematics to the physical world, this might be as good an explanation as any.

Note that a two-dimensional universe with non-zero mass ALWAYS collapses on itself, three-dimensional universes have the broadest "interesting" set of initial conditions that may or may not collapse.

1. #### Re: Why are there 3 dimensions?

"Spontaneous knotting of self-trapped waves"

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3480719/

2. #### a two-dimensional universe with non-zero mass ALWAYS collapses on itself

Will that be true if you allow a full range of exotic material with things like inflation potentials that comsologist propose to explain our early universe ? If you allow 2-D, I think you have to allow "stuff" like this, and over longer timeframes.

1. #### Re: a two-dimensional universe with non-zero mass ALWAYS collapses on itself

If you allow 2-D, I think you have to allow "stuff" like this

You may have to incorporate exotic matter if you want your 2D universe to have a chance of being stable, but that doesn't make the presence of exotic matter a given in any conjecturable 2D universe.

4. #### Re: Why are there 3 dimensions?

Ok, I'll bite...

General Relativity states there are three spacial dimensions, plus a fourth: time.

String theory posits there are at least 10 spacial dimensions, plus time.

Bosonic string theory suggests there could be as many as 26.

Three is only magical in the bedroom, but it must be cautioned that under such conditions the uncertainty principle can be seen working at macroscopic levels. ;)

1. #### Re: Why are there 3 dimensions?

Three is only magical in the bedroom, but it must be cautioned that under such conditions the uncertainty principle can be seen working at macroscopic levels

Yes, that's Borisonic swing theory I believe.

To quote Lurcio, "You know what they say: two's company, three's tiring..."

2. #### Re: Why are there 3 dimensions?

Time clearly isn't a dimension.

It's a parameterization of motion over space. If there was no motion, then no time has elapsed, every experiment is in the same state, every perception of time in everyones head is the same, i.e. no motion = no time.

And since we perceive time using motion of electrons in our brains, the two are directly linked.

Likewise any experiment we do requires motion.

So time is not independent of space, its just a parameter used to define motion over that space.

---

3 is observed.

You can hypothesize extra dimensions, but the 3 observed ones have certain properties and none of your extra dimensions would have those same observed properties.

You can claim your extra dimension are equally valid, because your equation treats them as equally valid, but it's just your equation. You don't have 4 dimensions, you have 4 parameters, those parameters have to generate 3 and only 3 dimensions.

1. #### Re: Why are there 3 dimensions?

Have summer school holidays already started?

2. #### Welcome to the ergosphere.

"Time clearly isn't a dimension."

What do you mean by "dimension"? If you beg the question and define "dimension" in such a way that only the three, extant spatial dimensions can satisfy it, then of course you're correct. But then we already know that time and any extra dimensions are not a spatial dimensions of the sort we see around us - at least, not at temperatures we can survive in.

But if you define dimension as an "independent" variable necessary to describe your position, then time is a dimension. (And, potentially, so too is electric charge.)

1. #### Re: Welcome to the ergosphere.

"What do you mean by "dimension"?"

An axis consistent with observation of space.

"if you define dimension as an "independent" variable necessary to describe your position"

Well no, because its not independent, so you can define anything in space as a motion in that space.

If your brain moved an electron along X to a neuron to perceive time, and an event happened in space, then you can define that event in terms of the X position of the electron in the brain perceiving it. Without having a time dimension at all! You've simply mapped one position in space to another position it is related to, using the location as the parameter instead of t.

Hence t is an arbitrary parameterization of motion.

Since whatever physics did the event, is the same physics that moves the electron in your brain the two are linked. If the physics moved it twice as fast, you'd perceive it twice as fast. i.e. the scale is perceived not real. To perceive the reverse of time, the electron would have to have the reverse of the physics applying to the event. i.e. the direction is also perceived.

2. #### Re: Welcome to the ergosphere.

Special relativity allows time and the other dimensions to mix, so it's not really independent. In the same way i, j, k depend which way round you're looking at something.

Why three? Don't know, would suspect weak anthropomorphic principle means it has to be more than two, since forces in two dimensions behave differently, there are consequences for thermodynamics too.

5. #### Re: Why are there 3 dimensions?

Because the Cosmos came into existence through the interaction of three spinning rings. Hence three is a fundamental number, the Trinity etc. Also three is the beginning of form.

Consider a point or dot, some religions consider this to represent the Unity. In Hebrew Yod is a dot and is the 10th character. (maybe there are actually 10 dimensions!)

Then move the dot through space and we get get a line. This could represent the duality of left/right, positive/negative or night/day etc.

Only when the dot moves back into a triangle do we get the beginning of form. This is considered to be feminine, "Mother of all" type of thing.

N.B. The only Unity is the unmanifest of which we can only say what it is not.

The Cosmos is reality, we live in a simulated Universe.

Well you asked! Now you know :)

1. #### Re: Why are there 3 dimensions?

Verily , you ARE a Mystic Megabyte !

2. #### Re: Why are there 3 dimensions?

Hence three is a fundamental number, the Trinity etc.

So it's a number invented by the Catholic Church some time in the 3rd century CE?

(It's what they call an 'Inferred[1] Doctrine' - one for which there is no direct evidence but is created to try to explain some parts of the text. Except it kinda destroys a whole bunch of others..)

Hebrew Yod is a dot

Err.. no. It's more akin to an apostrophe (but bigger). You do (in Modern Hebrew) get vowel points which are dots (which can be above or below the letters that they affect) but they didn't exist in Biblical Hebrew (which didn't have vowels at all - which leads to amusement when evangelicals insist on saying 'Jehovah'[2] or 'Yahweh' for YHWH since we can't be sure about how the tetragammnaton was acually pronounced - especially as the ancient Hebrews used 'adonai' instead so as to avoid blashphemy..).

[1] Nothing to do with cats.

[2] BiblicalHebrew didn't have the 'J' sound. Strictly speaking, 'Jesus' would have been 'Yeshua'..

6. #### Re: Why are there 3 dimensions?

Why do you think there are only 3 dimensions?

1. #### Re: Why are there 3 dimensions?

And how does that make you feel?

1. #### Re: Why are there 3 dimensions?

You're not really talking about me -- are you ?

7. #### Re: Why are there 3 dimensions?

With any other number of spatial dimensions you don't have stable orbits for planets.

We observe a Universe compatible with intelligent life because in Universes which aren't compatible we wouldn't be around to observe them.

8. #### Re: Why are there 3 dimensions?

Easy one

We are made of electromagnetic fields all our interactions are governed by EM and EM is 3 dimensional thus we can only see touch experience the 3 dimensions of EM. We are simply trapped in the 3d of EM and like flat landers can not leverage to any higher ones. QED

.

1. #### Re: Why are there 3 dimensions?

Erm,

EM fields exert force on 3d objects with no obvious touch point - aren't we at > 3 right there by the logic in the argument for observations of extra dimensions by their spooky skipping around 3d ojects?

9. #### Re: Why are there 3 dimensions?

Some physics theories claim that there are only 2 dimensions (holography) and that the 3 apparent dimensions emerge from the resulting hologram.

10. #### Re: Why are there 3 dimensions?

Because everything falls flat at 2.

And blows your mind at 4+

A 3D universe is where 3D beings may come to exist.

11. #### Re: Why are there 3 dimensions?

There aren't 3, there's rather more than that, as per quite a number of well-known hypotheses about the universe, some more well-founded than others. Heck, even I can get up to a minimum of 6 dimensions being necessary starting from first principles and based on the evidence of the world around us (something I have done for fun), and that's without considering some of the more esoteric things like how the strong and weak nuclear forces propagate (because I'm just not up to tackling the necessary for those). I can well believe there are rather more than 6 necessary in order to make the whole shebang work. 3 definitely isn't enough, though.

3. #### The Milky Way’s next merger event is expected to be with Andromeda,

"the collision isn’t expected for another 4.5 billion years. "

Oh good. That means Leo Apotheker won't be around anymore, I expect, to not look at Andromeda's books in preparation for the merger.

1. #### Re: The Milky Way’s next merger event is expected to be with Andromeda,

"Oh good. That means Leo Apotheker won't be around anymore..."

Don't bet on that, zombies can last for a long time if they are careful.

4. #### Verb choice!

> The two bodies eventually met and smashed into one another.

I know it makes for exciting prose, but given the density of matter in a galaxy (to a first approximation, there's nothing there...) it's much more appropriate to evoke two clouds of thin smoke gently coalescing over unimaginably long timescales.

1. #### Re: Verb choice!

That's only true in a puny human time frame. In galactic terms it was high-speed headlong smash.

2. #### Re: Verb choice!

much more appropriate to evoke two clouds of thin smoke gently coalescing over unimaginably long timescales

But, but, but - where's the jeopardy or explosions? You canna make a fillum without those y'know!

1. #### Re: Verb choice!

Michael Bay is that you ?

5. #### Re: we live in a simulated Universe

Free to download, but they sting you with content. Graphics are quite good, though. And the physics engine is mostly free of bugs.

1. #### Re: we live in a simulated Universe

Free of bugs !? Umm .... quantum theory

1. #### Re: we live in a simulated Universe

Free of bugs !? Umm .... quantum theory

That's not a bug, it's a feature.

A classical universe would be boring and physicists wouldn't get to play with cats.

[Why no cat icon?]

2. #### Re: we live in a simulated Universe

It's not too bad but it's got quite a few problems due to it being a rush job. The bloody client insisted it had to all be completed by Sunday.

3. #### Re: we live in a simulated Universe

Respawn time is ridiculous.

1. #### Re: we live in a simulated Universe

Well a lot of people think you respawn straightaway, but there's no guarantee you will be a high level character again. Apparently you can play as animals as well.

Other people believe you respawn in one of another couple of servers depending upon your in game behaviour. Apparently there is some sort of toxicity problem amongst players and this is supposed to help, but it doesnt seem to be having much of an effect...

1. #### Re: we live in a simulated Universe

Apparently there's a god-mode where the respawn time is 72 hours with no loss of XP.

4. #### Re: we live in a simulated Universe

Free to download, but they sting you with content. Graphics are quite good, though. And the physics engine is mostly free of bugs.

Shareware. Free for limited functionality, if you want full functionality (e.g. not watermarking output and so forth) you have to pay extra. Some free functionality couldn't work without dark matter and dark energy, so they included it to allow those specific free functions to work, but in general they masked it, hid it from anything else, direct observation and usage, until you pay the license fee, then you'll be able to access them.

6. #### Should have chosen a better name.

OK I get using the name Gaia in your naming of this new "galaxy" a) it was the name of the spacecraft you used to conduct the investigations and b) it is the mother goddess who helped "seed" the Earth (new planets formed from the union of the galaxies).

But why add "Enceladus" to that. Enceladus was one of Gaia's sons, one of the giants who fought against Zeus and the Greek gods and lost. Plus in greek myth he's buried under Mount Etna and still spitting his vengeance at Zeus the sky father. Ok he lost the fight and disappeared into the Earth (as this dwarf galaxy disappeared into the Milky Way), but thats it. It feels like a bit of a stretch.

I feel like Ouranos would have been a better choice (yes yes i know that's Uranus in english, but unless you know greek whose going to realise that?). Ouranos had his junk removed by Chronos (time) which seeded the earth wherever the blood (and the rest) landed (new planets forming), and was imprisoned in the centre of the Earth never to be freed again (eaten by the milky way). Oh and he was at least married to Gaia. much better choice in my opinion.

Sorry, I've been listening to too much Mythos by Stephan Fry...

7. Dear Mr Register,

You have a typo in the first sentence! You put "Gaia-Enceledus"

Unless that is the US spelling? In that case, please ignore my superfluous noise!

Best regards,

karlkarl

8. #### Earthmen are not proud of their ancestors, and never invite them 'round to dinner.

In the worlds before Monkey, primal chaos reigned. Heaven sought order, but the phoenix can fly only when its feathers are grown.

The four worlds formed again and yet again, as endless aeons wheeled and passed.

Time and the pure essences of Heaven, the moisture of the Earth, the powers of the Sun and the Moon all worked upon a certain rock old as creation, and it magically became fertile.

That first egg was named Thought.

1. #### Re: Earthmen are not proud of their ancestors, and never invite them 'round to dinner.

Is his flying cloud made by Hairbus?

9. #### The image - that's Andromeda (M31), not the Milky Way...

Or am I missing the point ...?

1. #### Re: The image - that's Andromeda (M31), not the Milky Way...

I have the same problem with the A2 and the Thanet Way

2. #### Re: The image - that's Andromeda (M31), not the Milky Way...

The Reg hack probably had a bit of trouble finding a full image of the Milky Way.

1. #### Re: The image - that's Andromeda (M31), not the Milky Way...

Yep, galactic selfie sticks are bloody expensive these days...

1. #### Re: The image - that's Andromeda (M31), not the Milky Way...

Surely a physicist would have an infinitely long perfectly rigid rod lying around somewhere. I suspose the problem would be cutting it down to size.

10. You don't want a whole dwarf in Uranus

1. #### A s s h o l e !

;-) xd

11. But don’t panic: the collision isn’t expected for another 4.5 billion years.

So enough time to get Brexit sorted out. Just.

1. So enough time to get Brexit sorted out. Just.

Optimist.

12. One ate the other ? Surely they agreed a merger.

13. #### Figures of speech

"Elsewhere, at the same time, Gaia-Enceladus, a dwarf galaxy, was quietly unfolding, too."

Can anyone picture the unfolding of a galaxy? And quietly, not that anyone would have heard it out in space anyways.

Seriously, read up on Orwell's rules. Use your metaphors sparingly and only where they enrich your text.

## POST COMMENT House rules

Not a member of The Register? Create a new account here.