20 replies to this topic

[CygnuS]

People always seem fascinated that the Milky Way Galaxy and Andromeda Galaxy are going to merge. I've always loved explaining it to people. I even have a PowerPoint presentation about it. 

But now I've learned that it might not happen (Astronomy magazine, Jan '25 issue page 9). What should I do now? Should I explain that it might not happen....or is there not enough proof yet to go that far? 

Is it possible it is still going to happen but much later than the predicted 5 billion years from now?

[NinePlanets]

Does it really matter either way?

[Napp]

Just say that it may happen.  Those around in 5 billion years can confirm whether it did or did not.  It's an interesting story to talk about what may happen. 

[AstroPhotog]

Hi CygnuS, say what you're comfortable with when telling others. After all, it's only theory at this point, and will be for generations. Over the years I've seen several scenarios described for the event and none of us will ever really know. Cheers!

[CygnuS]

Does it really matter either way?

The reason that it matters is because when you are trying to get people interested in astronomy you need to be a good storyteller. You need to embellish things occasionally because people (especially kids) enjoy that. You might just say something to a young person that sparks a lifelong interest in astronomy. 

But you also have to tell the truth, or at least as science currently understands it. 

I think I will just ignore it for now but if I hear a lot more about this non-merger it would be irresponsible to not mention it. I thought it was a done deal that the merger was going to happen. Was it never settled on? What has cast doubt? A new computer simulation? 

[Napp]

The reason that it matters is because when you are trying to get people interested in astronomy you need to be a good storyteller. You need to embellish things occasionally because people (especially kids) enjoy that. You might just say something to a young person that sparks a lifelong interest in astronomy. 

But you also have to tell the truth, or at least as science currently understands it. 

I think I will just ignore it for now but if I hear a lot more about this non-merger it would be irresponsible to not mention it. I thought it was a done deal that the merger was going to happen. Was it never settled on? What has cast doubt? A new computer simulation? 

I think you are overthinking this.  One or more groups runs some simulations and determines there is a good chance the galaxies will merge.  Another group runs a different simulation and gets different results.  These are not experiments proving anything.  A lot of asumptions are used in them because we do not have either enough or the right data.  Neither is a proof of anything but provide possible outcomes.  Much of what is currently accepted is based on just such modeling with a lot of assumptions.  It's subject to change as more data is collected and newer, hopefully better, simulations are developed.  If you are only wanting to present absolute 'truth' you're going to have very little to talk about.  

 

I think talking about the merger of two galaxies is an exciting topic.  There are ongoing mergers that are being observed.  Talk about such known mergers if it makes you more comfortable.  But I would still include possible scenerios for the Andomeda and Milky Way Galaxies.  

[Skywatchr]

The reason that it matters is because when you are trying to get people interested in astronomy you need to be a good storyteller. You need to embellish things occasionally because people (especially kids) enjoy that. You might just say something to a young person that sparks a lifelong interest in astronomy. 

But you also have to tell the truth, or at least as science currently understands it. 

I think I will just ignore it for now but if I hear a lot more about this non-merger it would be irresponsible to not mention it. I thought it was a done deal that the merger was going to happen. Was it never settled on? What has cast doubt? A new computer simulation? 

I would suggest to use the words "possibly" "may" and "things can change".   More observations and studies are needed to unlock the mysteries of the Universe.  And that their thoughts and contributions will be necessary for the future.  Any one of them could be the discoverer of something previously unknown, or an approach not yet conceived by anyone else.  There could be some unseen "Gravity well" or Gravity wave" that might change the direction that each or both Galaxies are currently moving in.  Similar to the wind you cannot yet see that can blow you off course in an aircraft or sea going vessel, or groups of. Give them possibilities to spark their imaginations.

[CygnuS]

I think you are overthinking this.  One or more groups runs some simulations and determines there is a good chance the galaxies will merge.  Another group runs a different simulation and gets different results.  These are not experiments proving anything.  

I'm pleading not guilty on this one and pointing to magazines. I go back and forth between Sky&Telescope and Astronomy. I've been getting one or the other for 30 years. I have seen several stories on the subject and this is the first time I have ever heard the merger might not occur. Do you think these magazines have known this all along but a non-merger doesn't make for a story that sells magazines? Why then would they pick now to reveal it? 

[Skywatchr]

I'm pleading not guilty on this one and pointing to magazines. I go back and forth between Sky&Telescope and Astronomy. I've been getting one or the other for 30 years. I have seen several stories on the subject and this is the first time I have ever heard the merger might not occur. Do you think these magazines have known this all along but a non-merger doesn't make for a story that sells magazines? Why then would they pick now to reveal it? 

Sales....   They gotta have something to print for each issue besides all the advertising. 

[Napp]

I'm pleading not guilty on this one and pointing to magazines. I go back and forth between Sky&Telescope and Astronomy. I've been getting one or the other for 30 years. I have seen several stories on the subject and this is the first time I have ever heard the merger might not occur. Do you think these magazines have known this all along but a non-merger doesn't make for a story that sells magazines? Why then would they pick now to reveal it? 

First, these are model runs based on existing data and theories and assumptions to fill in for unknowns.  And there are unknowns that are not included because they are unknown.  The models are constantly evolving.  None are gospel - there are too many unknowns.  Sometimes a following model is better but sometimes it's not.  It's an evolving process.

 

Science magazines are not a vault of the truth.  They select articles based in large part on what they think will draw attention to get readership and sell magazines.  If a lot of (not all) groups have published results indicating the two galaxies will merge then publishing another article on another group getting the same results is a bit ho hum.  It's not likely to excite the readership as much as an article on a group getting different results.  None of these models are 'truth'.  They are an evolving process.  Beings in the distant future will see what actually happens and it may not be a good match with any of the models we have today.

 

You can't present any of these models as what will happen.  Rather talk about the possibilities these models present.  Talk about how we observe galaxies in collision, mergers and near misses. Talk about what may happen with the Andromeda and Milky Way galaxies.  Nobody knows what will happen.  We can only talk about what we think the possibilities are that may happen.  And different groups have different ideas.  It's okay to say we don't know but here are some ways we think it could go.  I think that stirs folks to think and use their imaginations. 

[RamStrocsop]

Sales.... They gotta have something to print for each issue besides all the advertising.

🤣 😂😆

[CygnuS]

I'm not sure I'm buying the conspiracy theory that it is sensational journalism. If that was the case they would have gone back and forth on the subject to stir things up. Why would they have waited 30 years for their first reversal?

(Or however many years they first learned of the merger) 

[Napp]

I'm not sure I'm buying the conspiracy theory that it is sensational journalism. If that was the case they would have gone back and forth on the subject to stir things up. Why would they have waited 30 years for their first reversal?

(Or however many years they first learned of the merger) 

I doubt there is any conspiracy and I won't go so far as 'sensational journalism'.  However, the companies have to sell magazines to stay in business.  That means they need to publish articles that catch readers' interest.  Maybe the article that has caused you so much concern may include new data or a different approach - something that the editors thought readers would find interesting. 

 

What I and I think others are suggesting is approaching the topic from a different perspective.  You seem to be upset that 'something' was established in the past and now it's not so what do I do.  That's science.  Things that were accepted yesterday are not today because of new findings or new ideas.  I doubt there was any conspriacy here.  Different groups attack the same problem from different approaches and get different results.  That's part of the scientific process.  Look at the quandry of the Hubble Constant known as the Hubble Tension. 

 

Personally, I think you have a more interesting story to tell now about the future of our galaxy.  Explore the possibilities.  We don't have the definite answer but we can talk about the different theories.

[CygnuS]

 

 

What I and I think others are suggesting is approaching the topic from a different perspective.  You seem to be upset that 'something' was established in the past and now it's not so what do I do.  That's science.  Things that were accepted yesterday are not today because of new findings or new ideas.  

I understand how science works. And no, I am not upset that this information is different than I have thought it was all these years. I guess I am upset with myself for not looking into it enough to know that there is a doubt about the merger. 

But I really haven't had my OP question answered. Is there a strong enough belief that the merger might not happen that I should change what I say? If the short clip in Astronomy magazine is all there is, then I won't alter it. If it is the only study out of 100 that thinks the merger won't happen, then it is hardly worthy of mention during a speech geared toward the general public, many of whom don't even know the North Star isn't the brightest one.

[NinePlanets]

Just tell them they will merge, then challenge them to prove you wrong.

 

Done.

 

Next?

[HouseBuilder328]

Why does this prediction keep changing on whether they will hit each other or not?  Is it because of the sheer size of space and we don't know the trajectories?    (like whether 2 bullets will hit each other if you fire a gun with people on opposite sides of a football stadium)

[CygnuS]

Why does this prediction keep changing on whether they will hit each other or not?  

I was surprised to learn that it changed once so I'm not sure how many times it has changed. It sounds more like a disagreement and not necessarily a change. I was surprised to learn there are people who think the merger won't happen. And yes I know folks. No need to repeat it. That's how science works. But I still don't know what evidence has materialized that indicates the merger won't happen. One computer simulation disagreeing with another I guess. It must be different sets of data that was put in. So the debate must be with the data, not the simulation. 

[Dave Mitsky]

There's an online article on this topic from Astronomy at https://www.astronom...erge-after-all/

Here's part of the abstract from the original paper.

It is commonly believed that our own Milky Way is on a collision course with the neighbouring Andromeda galaxy. As a result of their merger, predicted in around five billion years, the two large spiral galaxies that define the present Local Group would form a new elliptical galaxy. Here we consider the latest and most accurate observations by the Gaia and Hubble space telescopes, along with recent consensus mass estimates to derive possible future scenarios and identify the major sources of uncertainty in the evolution of the Local Group over the next 10 billion years. We find that the next most massive Local Group member galaxies -- namely, M33 and the Large Magellanic Cloud -- distinctly and radically affect the Milky Way - Andromeda orbit. While including M33 increases the merger probability, the orbit of the Large Magellanic Cloud runs perpendicular to the Milky Way - Andromeda orbit and makes their merger less likely. In the full system, we find that uncertainties in the present positions, motions, and masses of all galaxies leave room for drastically different outcomes, and a probability of close to 50% that there is no Milky Way - Andromeda merger during the next 10 billion years.

 

A pdf of that paper can be seen at https://arxiv.org/pdf/2408.00064

A short video that Starman1 posted in an earlier CN thread on this topic appears at https://www.youtube....h?v=d078KeA7Rn0

 

 

[CygnuS]

Thank you so much Dave. This is so like you, to be this helpful.

It's nice to see science work like science is supposed to work. For folks like me (who aren't as smart and well informed as folks like you) it can be frustrating. This study says that there is a 50% chance that the merger won't happen. IF it is the only study that says that.....and 100 other studies say there is a 95-100 % chance the merger will happen......then this study doesn't mean much.

For the average reader it can be difficult to know what to believe because gathering all the information from all the studies on a particular subject can be a daunting task. That is why it is sometimes best that we have no opinion at all. But that is also boring. 

[archer1960]

Interesting. I'm surprised that the mass of the LMC is large enough to have a significant effect on the MilkyWay/Andromeda merger probability. Obviously more detailed modeling is needed, but I wouldn't think it would be that difficult to do, given sufficient knowledge of the masses and current velocities of the various components of the system.

[Steve Cox]

Why then would they pick now to reveal it? 

Money...it's that simple.