typodupeerror

## Andromeda On Collision Course With the Milky Way217

ananyo writes "From the Nature story: 'The Andromeda galaxy will collide with the Milky Way about 4 billion years from now, astronomers announced today. Although the Sun and other stars will remain intact, the titanic tumult is likely to shove the Solar System to the outskirts of the merged galaxies. Researchers came to that conclusion after using the Hubble Space Telescope between 2002 and 2010 to painstakingly track the motion of Andromeda as it inched along the sky. Andromeda, roughly 770,000 parsecs (2.5 million light years) away, is the nearest large spiral galaxy to the Milky Way.'"
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## Andromeda On Collision Course With the Milky Way

• #### 770,000 parsecs? (Score:5, Funny)

by Anonymous Coward on Friday June 01, 2012 @01:30AM (#40176761)

I thought parsecs was a unit of time though? So 770,000 parsecs is about 4 billion years?

So 12 parsecs is about 20 hours?

• #### Re: (Score:2)

parsec is space.

take 1 astronomical unit as the opposite side length on a right-angled-triangle, one arc-second as the angle, and the length of the adjacent side will be 1 parsec.

• #### Re: (Score:2)

I thought parsecs was a unit of time though? So 770,000 parsecs is about 4 billion years?

So 12 parsecs is about 20 hours?

http://en.wikipedia.org/wiki/Parsec [wikipedia.org]

The parsec (symbol: pc) is a unit of length used in astronomy. It is about 3.26 light-years, which is equal to just under 31 trillion (3.1×1013) kilometres or just over 19 trillion (1.9×1013) miles.

• #### Re: (Score:2)

So. A measure of both distance and time, depending on your context.

• #### Re: (Score:3)

Nope, I don't see a unit of time in there, sorry.

P.S. you're all being trolled.

• #### Re:770,000 parsecs? (Score:5, Informative)

on Friday June 01, 2012 @04:41AM (#40177681)

So. A measure of both distance and time, depending on your context.

No. A parsec is "a distance corresponding to a parallax of one second". But here, "second" does not refer to the unit of time "second" but to an "arc-second", a specific angular value. If you have a circle, and you divide it into 360 parts, a single slice covers an angle of exactly one "degree" (do note that this in turn also does not refer to temperature). If you divide that slice into 60 parts, each slice covers an angle of 1 arc-minute. If you divide such a slice into another 60 parts, you get an angle that covers 1 arc-second.

But even if you had used a unit of time to define the parsec -- like in the light-year -- what you actually define is a pure length. Do note that you can define a light-year as both "the distance light crosses in an absolute vacuum in one solar year" or "9.4605284 x 10^15 meters". See how the latter does not include any reference to time? You could even express the light-year as the distance you can drive an object of a certain mass and shape when you accelerate it with a certain energy through a perfectly uniform medium of a certain density (thus slowing down the object eventually to a standstill).

You can define a length with the help of a unit of time, but you don't need to. That is also why the 1 astronomical unit distance used in the parsec is also not a unit of time; as the fact that it derives from the rotation of the earth around the sun is unimportant as long as the ultimately defined value remains a pure time.

• #### Re: (Score:3)

[...] the ultimately defined value remains a pure time.

Please mentally replace that part with "the ultimately defined value remains a pure unit of distance."

• #### Re: (Score:2)

Just remember that distance and time are interchangeable thanks to the speed of light.

• #### Re: (Score:2)

The sec in parsec refers to a angle on the circle (what is the radius when one arc second is 1 AU?).

• #### oh noews! (Score:4, Funny)

on Friday June 01, 2012 @01:31AM (#40176767)
can't we launch a mission to deflect it ? !
• #### Re: (Score:2)

Nope, this event is clearly unavoidable. There is no way we have enough time to relocate or divert it.

• #### Re: (Score:3, Funny)

by Anonymous Coward

Eh, the Sun itself only has about 4.5 billion years left in it...So Andromeda slamming into us might be a welcome change by then.

• #### Re: (Score:3, Funny)

by Anonymous Coward

Nope, this event is clearly unavoidable. There is no way we have enough time to relocate or divert it.

What if we used a crack team of roughnecks?

• #### Re: (Score:2)

It might work, but only if the boffins get it hopelessly wrong first despite all their fancy-pants book larnin'.

• #### Don't Panic (Score:3, Funny)

on Friday June 01, 2012 @01:32AM (#40176771)

Stop Panicking!!! This is no time to panic... Though if you do panic try to hold on to that feeling because it is the proper response to being told that your galaxy is on a collision course with another galaxy.

• #### Re: (Score:2)

I don't know whether to call Zaphod for help, or start stocking bottled water.
• #### Re: (Score:2)

I'm sure the Vogons are behind this...

• #### The worst danger.... (Score:2)

...is that it will attract the Eddorians.
• #### Re: (Score:2)

...is that it will attract the Eddorians.

Don't worry, in another 4 billion years, surely we will have met the Arisians. Right?

• #### Re: (Score:2)

And in the meantime, we will have developed incredible technologies which are able to output enormous amounts of power, allowing our ships to move at stupendous velocities so we can undertake the titanic struggle against the forces of Boskone!

Am I doing it right?

• #### Re: (Score:2)

770,000 Parsecs!?! Ha the Millennium Falcon could do it in less.

• #### Re: (Score:2)

I'm not panicking at all, for 2 reasons:
1. By then, I'll be long dead. At worst, some sort of crazy intergalactic radiation will have me back as some sort of zombie.
2. By then, it's quite possible the sun will be a red giant, which means that whatever we've evolved to over 4 billion years is either dead or capable of moving very very far away.

• #### Re: (Score:3)

capable of moving very very far away.

Why? When galaxies collide, they don't actually hit anything. Their stars just orbit the new centre of gravity (variable until the merger settles). Entire civilisations could rise and fall during the collision, and not notice it happening.

• #### Watch video of simulation of this collision (Score:5, Interesting)

on Friday June 01, 2012 @01:33AM (#40176785) Homepage
NVIDIA showed a simulation of this collision running on their latest Tesla GPGPU based on the "Kepler" architecture

Starts at around 1:00 on this video with a great explanation of the collision itself.

Sumit
(NVIDIA employee)
• #### Re: (Score:3, Informative)

by Anonymous Coward

Andromeda-Milky Way collision starts at 2:54, before that is a recap of the Fermi architecture.

• #### Re: (Score:3)

Less talking more animation.

Seriously they stop the thing like 20 times to talk.

• #### Re: (Score:2)

That's typical of visual media. Because they have no content they will forever repeat little snippets of what they have already told you to try to pad the whole thing and make it longer. Of course saving the actual reason you are watching the whole thing for for last is part of the "carrot and stick" model that's been used ever since communication media existed.
• #### Re: (Score:2)

I'm a little confused. In the video they themselves note that around 90% of the matter in the universe is dark matter, and as far as I'm aware its configuration around our galaxies isn't well known, so... isn't the simulation basically worthless? The article doesn't clear this up either, though perhaps the papers would.

• #### Interesting timing (Score:2)

It's an odd coincidence that it starts to happen around the time our sun goes red giant. Not that anything resembling Homo Sapiens would be around. 5 billion years ago we hadn't made it up to the level of bacteria yet. Impossible to say what Earth life would be like by then if it survived that long. Odds are all life would be wiped out well before we go red giant. Even another billion years from now conditions will be quite harsh. Too bad because in 7 billion years we'd have a very interesting sky.
• #### Re: (Score:3)

It really brings home an appreciation for the human race. For all the wailing and gnashing of teeth about environmental damage we really are the only chance for earth based biodiversity to survive.

• #### Re: (Score:2)

It really brings home an appreciation for the human race. For all the wailing and gnashing of teeth about environmental damage we really are the only chance for earth based biodiversity to survive.

Don't be so sure [arxiv.org].

• #### Re: (Score:2)

5 billion years ago we hadn't made it up to the level of bacteria yet.

I was under the impression that the Earth was only 4.5 billion years old.

Although I suppose you could go with panspermia and adopt the position that life here started 5 billion years ago; it just started somewhere else.

• #### Re: (Score:2)

A half billion years here, a half billion years there, pretty soon you've added up to some real time.

• #### don't panic, it's just the end of the world (Score:5, Informative)

on Friday June 01, 2012 @01:37AM (#40176807)

It's been known for a long time that Andromeda had a velocity towards the Milky Way (easily measured by its blue-shift), but no one could tell what its lateral velocity was, therefore whether it was going to actually collide or whether it was in an eccentric orbit. Actually measuring such a tiny side-shift, against more distant galaxies, of a source which is not actually a single defined object, where every part of it is in separate motion, in just 8 years, is pretty fucking impressive.

• #### Oh no! Not the Galaxy! (Score:5, Funny)

on Friday June 01, 2012 @01:56AM (#40176907)

That's where I keep all my stuff!

• #### Re: (Score:2)

That's where I keep all my stuff!

I keep the Galaxy in my pocket. And in case it crashes, I just reboot it. What's all the fuss about?

• #### Andromeda is coming HERE? (Score:2)

You think maybe the Kelvans are behind this?

• #### AAAHHHHHH! (Score:2, Funny)

by Anonymous Coward
AAAAHHHHHHHHHH! *pause for breath* AAAAHHHHHHHHHH!
• #### Re: (Score:2)

AAAAHHHHHHHHHH!
*pause for breath*
AAAAHHHHHHHHHH!

Yeah and that for the next 4 billion years!

• #### whew! (Score:3)

<jabberwock.poetic@com> on Friday June 01, 2012 @02:59AM (#40177233)

(wiping sweat from brow)
I thought for a moment that TFA said 4 million years.
Hey, 4 billion is a long time. No need to panic.

If we still depend on the Sun in 4 billion years, we're screwed anyway. Maybe we could've burried deep underground or something, shielded from the heat and toxic atmosphere, but we need to become a lot more mobile if we intend to live on as a species (not that it's likely to be the same species as it is today).

• #### Crossover (Score:3)

on Friday June 01, 2012 @03:43AM (#40177451)

Andromeda / Star Trek crossover, about time.

• #### The Perseus Galaxy (Score:2)

Wow, so we live in the Perseus galaxy and Andromeda really does have a rock chained to her (the M33 galaxy). Oh yeah, and for those who think I'm speaking nonsense:

Andromeda is an Ethiopian princess from Greek mythology who, as divine punishment for her mother's bragging, the Boast of Cassiopeia, was chained to a rock as a sacrifice to a sea monster. She was saved from death by Perseus, her future husband (Wikipedia [wikipedia.org]).

• #### Imagine (Score:5, Interesting)

on Friday June 01, 2012 @04:41AM (#40177683)

Imagine how awesome the sky would look once Andromeda is near enough to dominate the view.

Imagine how awesome the sky would look with two galaxies, one of them much larger than our own, sprawling around it.

Imagine how such a view might affect the belief systems and cultures of all the advanced life forms that might be able to perceive it.

Hopefully, I will be there, billions of years in the future, and be able to experience it.

• #### Re:Imagine (Score:4, Informative)

on Friday June 01, 2012 @09:20AM (#40179041)
Imagine how awesome the sky would look once Andromeda is near enough to dominate the view.

Andromeda is already that big in the sky - it's over four times the size of the full Moon as seen from Earth right now. It's *extremely* diffuse though (and will continue to get more diffuse as it gets closer), so it's quite dim and generally isn't visible except from relatively dark sites.
• #### Re: (Score:2)

Andromeda is already that big in the sky - it's over four times the size of the full Moon as seen from Earth right now. It's *extremely* diffuse though (and will continue to get more diffuse as it gets closer), so it's quite dim and generally isn't visible except from relatively dark sites.

Why will Andromeda get more diffuse?

• #### Re: (Score:3)

Wow, I really didn't know that. I found this site [blogspot.de] showing an image with a nice size.

It's quite amazing to think about how huge and close it is, to occupy such a relatively large portion of the sky. Too bad we can't appreciate it's splendor. I wonder if the view will improve as it gets closer. A poster above mentioned that it will get diffuser the closer it gets, but I wonder why.

• #### Re: (Score:2)

Before we start making plans for Andromeda-crash watching parties, let's not forget that at about the same time our sun will become a red giant and expand to beyond the orbit of Mars.

Sizzle

Poof

• #### Not an unexpected result (Score:4, Interesting)

on Friday June 01, 2012 @04:51AM (#40177721) Journal

Isolated clusters of galaxies (such as the local group) are expected to have low total angular momentum (basically because the initial condition has low angular momentum, and in the absence of large mass anisotropy nearby, there is nothing to change this.) The mass of the local group is dominated by Andromeda and us, and hence so is the angular momentum. If the us/Andromeda pair has low angular momentum about their centre of mass (and given the pair is gravitationally bound), they will both pass close to that centre of mass - i.e., they will collide.

Of course, having an actual measurment is much more satisfying than having a theory.

Also - although they can be spectacular from outside, galactic collisions aren't expected to have bad results for life living on their planets. The biggest effect is that colliding dust clouds trigger a burst of star formation, so the night sky will be pretty.

It has been a few decades since I studied this, so I hope this is all accurate.

• #### order of magnitude (Score:2)

The diameter of the sun is 1e9 meters. The distance to the closest star, Alpha Centauri, is about 4e16m (40 lightyears)...Let's put that in context:
Suppose the sun is the size of a grain of sand, say 1mm (1e-3mm), the distance to the nearest grain of sand is 40 kilometer. So a collision between galaxies is basically collision between empty spaces...
• #### Re: (Score:2)

Ironically, your example was off by an order of magnitude. Alpha Centauri is 4 light years or 4e15m away.
• #### Re: (Score:2)

Ironically, your example was off by an order of magnitude. Alpha Centauri is 4 light years or 4e15m away.

And Alpha Centauri isn't even the closest star, Proxima Centauri is.

• #### Re: (Score:2)

I was going to challenge your assumptions about the nature of empty space in regards to collisions between large bodies. I was told in school that all matter consists largely of empty space. So I examined the common element iron:

The diameter of the nucleus of an iron atom is 1.26e-8 cm. The standard atomic weight of iron is 55.845 (which is equivalent to 55.845 gm/6.022e23 atoms or 1gm/1.0783e22 atoms). The density of iron at room temperature is 7.874 gm/cm^3. So 1 cubic centimeter of iron weighs 7.874 gram

• #### The Inhibitors already knew... (Score:3)

on Friday June 01, 2012 @06:18AM (#40178037)

How come nobody's mentioned Alastair Reynold's Revelation Space [wikipedia.org] series yet? Doesn't anyone here read SF?

The fact that the Milky Way and Andromeda galaxies will eventually collide is the motivation of the Inhibitors.

• #### Finally! (Score:2)

At last, mankind will have a convenient and cheap way of intergalactic travel: Wait for it to come to us.
• #### Oh Great! (Score:2)

Oh Yay, more bad Sci-Fi with Kevin Sorbo....

Why cant they let that whole show just die?

• #### note from the future (Score:2)

Note from the future: Ironically that was the same year the members of the United States Congress finally stopped their partisan political bickering.
• #### Oh great, and I have a haircut that day. (Score:2)

I hate having to re-arrange my schedule like this.

• #### And about a Billion years from now... (Score:2)

The photos we get from our space telescopes will be so much sharper as things get closer!

Unfortunately, we won't even be here as a species in a million years. We'll either have died out, or long since left the planet, Earth won't even be remembered as a story told to children. And that's assuming we could even recognize ourselves after some period of evolution.

Personally, I'm betting on the died-out version. Our civilization has limited energy resources, and limited vision for the future. Once the oil runs

• #### Re: (Score:2)

I dunno, I think it's fairly likely that the knowledge that we came form Earth will still be available in a million years (assuming we don't go the died-out way).

I say that mostly because we don't seem to be losing much history these days, everything (no matter how trivial and stupid) is recorded somewhere. I definitely would agree that it would be considered special in any way, but I feel like it'll still be knowledge that's available to be had easily.

• #### No surprise (Score:2)

Andromeda on Collision Course With the Milky Way

I knew Kevin Sorbo couldn't drive.

• #### Don't worry (Score:2)

Under the Republicans we are turning so far to the right that we could easily miss it.

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If I have seen farther than others, it is because I was standing on the shoulders of giants. -- Isaac Newton

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