Dark Energy Question

[Xray the Enforcer]

It's not that you're wrong (and it's clear from the OP that you're way out of your depth), it's that you thought you knew more about physics than Starkess and you felt compelled to slap her down with a very specific verbal construction. Congratulations on being a mansplaining jerk. 

[Ser Scot A Ellison]

1 minute ago, Xray the Enforcer said:

It's not that you're wrong (and it's clear from the OP that you're way out of your depth), it's that you thought you knew more about physics than Starkess and you felt compelled to slap her down. Congratulations on being a mansplaining jerk.

If I came across as a mansplaining jerk or trying to slap down Starkess, I'm really sorry.  That's not what I was trying to do.  

And I am out of my depth.  It was just something I was thinking about and I brought it here because there are a fair number of people, Starkess among them, who could explain what I'm not understanding or what we all don't understand yet.

Again, I'm very sorry for "mansplaining".  It wasn't what I was trying to do at all.  

[Xray the Enforcer]

So, I think this is a teachable moment and I'm glad that we got here. 

Instead of saying something like "Actually...." (seriously, never say this), you could say something like "OK, I see what you're saying. But would the raisin analogy not also be true of inflation?" (I'm just using your phrasing, regardless of its scientific veracity here.) This indicates that you acknowledge Starkess's thoughts on this and you want to explore it further. 

Most (let's say 99.99999 percent) of the time, when someone pulls out the "Actually,...." construction on a person, it's meant to shut that person down. And a lot of times, men do it to women because we couldn't possibly know what we're talking about, and we should really just STFU because the menz be talkin'. This is a socially constructed thing, and it's hard to combat. But being aware of your language and how you use it is an important step to being a better, more equitable communicator. 

[Ser Scot A Ellison]

5 minutes ago, Xray the Enforcer said:

So, I think this is a teachable moment and I'm glad that we got here. 

Instead of saying something like "Actually...." (seriously, never say this), you could say something like "OK, I see what you're saying. But would the raisin analogy not also be true of inflation?" (I'm just using your phrasing, regardless of its scientific veracity here.) This indicates that you acknowledge Starkess's thoughts on this and you want to explore it further. 

Most (let's say 99.99999 percent) of the time, when some dude pulls out the "Actually,...." construction, it's meant to shut women down. Because we couldn't possibly know what we're talking about, and we should really just STFU because the menz be talkin'. 

I'm really sorry... absolutely not what I was trying to do.  I welcome and would love more discussion from those who know a lot more than I do.

I'll refrain from using "actually..." in the future.

[Xray the Enforcer]

Totally understood that you didn't deliberately mean to belittle Starkess. I just wanted you to know how something like that is perceived, especially by women in technical fields who get talked over all. the. time. And how to avoid it for the future.  And thank you. 

(also, not sure if you're on Twitter but following a number of female scientists -- especially chemists and physicists -- is really enlightening to the myriad ways that society questions their credentials. There was a hashtag on it a couple of months ago of all the ways that women were overlooked/denigrated in the sciences and it was really enlightening. I even saw a sin that I had myself committed in the past, so all I can say is that we always have something to learn!)

[Ser Scot A Ellison]

Just now, Xray the Enforcer said:

Totally understood that you didn't deliberately mean to belittle Starkess. I just wanted you to know how something like that is perceived, especially by women in technical fields who get talked over all. the. time. And how to avoid it for the future.  

Thank you.

[Kalbear]

7 hours ago, WinterFox said:

I mean, I thought that 1g is a measurement of how forcefully the earth pulls against us on its surface. But if we're accelerating towards or from something, wouldn't that effect be measurable?

 

Yes! It would be - and as it turns out, it is. While we probably don't feel it - I suspect the gravitational constant of earth's pull outweighs all the other forces that we can personally detect (such as, say, the sun's gravitational pull on us personally, or the moon's gravitational pull, or Jupiter's, etc), but we actually can measure things like the acceleration of the expansion of the universe. 

[Altherion]

3 hours ago, Ser Scot A Ellison said:

Altherion,

I understand that "inflation" is a phenomenon that occurred once in the early Universe.  What I wonder is whether it is also a continuing phenomenon occurring in the background that could be used to explain the acceleration of the spread of galactic clusters?  

Doesthat make more sense?  In other words some believe "inflation" happened in a big way early in the history of the Universe, then stopped.  What if it didn't stop but merely slowed down a lot?  What if that small but constant inflation can account for the acceleration?

We don't know what caused inflation so maybe there is some tiny residual effect, but the mechanism responsible for the current acceleration of expansion is almost certainly different. The current acceleration appears to be due to the energy of empty space ("dark energy"). The more space there is, the faster it expands (this gives you exponential growth). Again, we don't know what caused inflation... but space was relatively tiny back then so we can be pretty confident that it wasn't dark energy.

[Kalbear]

 

[Future Null Infinity]

Ser Scot,

Sorry for my english,

Indeed, the space-time can move faster than light, it is not prohibited by the general relativity, the speed limit applies only for objects and particles

The accleration of the expansion of the Universe is not a property of the space-time because it accelerated, decelerated and again it is accelerating now

the deceleration after the inflation indicates :

- the actual acceleration is not related to the inflation so the actual acceleration is not the continuation of the inflation

- The acceleration-deceleration-acceleration observation suggests that space-time is not responsible for its acceleration, rather, an external force is acting upon it making it accelerating, this is why scientists proposed dark energy as the main force

We know that the universe is expanding and not the galaxies are moving faster because all the galaxies are moving away from us, if it was the movement of the galaxies we will see some moving away and some getting closer but it is not the case, it's the exapnsion of the universe that drive all the galaxies to move away in all directions

[Free Northman Reborn]

On 2017/05/16 at 1:33 PM, Xray the Enforcer said:

So, I think this is a teachable moment and I'm glad that we got here. 

Instead of saying something like "Actually...." (seriously, never say this), you could say something like "OK, I see what you're saying. But would the raisin analogy not also be true of inflation?" (I'm just using your phrasing, regardless of its scientific veracity here.) This indicates that you acknowledge Starkess's thoughts on this and you want to explore it further. 

Most (let's say 99.99999 percent) of the time, when someone pulls out the "Actually,...." construction on a person, it's meant to shut that person down. And a lot of times, men do it to women because we couldn't possibly know what we're talking about, and we should really just STFU because the menz be talkin'. This is a socially constructed thing, and it's hard to combat. But being aware of your language and how you use it is an important step to being a better, more equitable communicator. 

Teachable moment?

Firstly, are you talking in the guise of moderator or in the guise of giving your personal opinion here? If the former, well then I guess I have nothing to say.

If the latter, don't make me laugh. What parralel SJW universe do I find myself in here? Scott's lack of knowledge on the subject is one thing, and he can rightly be proven wrong as a result. Asking people not to use a condescending tone in case it hurts someone's feelings? What is this? Kindergarten?

[Kalbear]

15 minutes ago, Free Northman Reborn said:

If the latter, don't make me laugh. What parralel SJW universe do I find myself in here? Scott's lack of knowledge on the subject is one thing, and he can rightly be proven wrong as a result. Asking people not to use a condescending tone in case it hurts someone's feelings? What is this? Kindergarten?

Actually, if you had read the response you'd understand why they're asking not to use that tone - because it shuts down the ability to be proven wrong as a result, as those who might consider responding to you to correct you and prove you wrong won't. 

[maarsen]

For those that are interested  Scientific American has an interesting article this month that touches on this issue, and more. 

[The Anti-Targ]

I thought more recently that questions have been raised about the validity of the accelerated expansion observation. Which possibly makes this bit of Tyson's Cosmos series out dated.

It's one of the problems with pop science. A lot of people will interpret pronouncements in such shows as fixed and proven, when the opposite turns out to be the case a few years down the line. But that does not mean pop science shows should not be part of the scheme of science communication to the masses. But science communication to the masses needs to keep reiterating that such snapshots of what's known (or thought to be known) are not immutable and pretty much most things that are known are best interpretations of current and historic observations, not absolute facts. And these interpretations could change with a single observation tomorrow.

But then you have to educate people that while we don't know things absolutely, this should not paralyse decision making, or make people dismiss interpretations they don't like as probably false, merely awaiting the new data to show them as false. We should still makes decisions based on the best interpretation of the data we have.

[Ser Scot A Ellison]

TAT,

I'd love to see the articles challenging the findings regarding the acceleration of the expansion of the Universe.  Would you mind sharing?

[Altherion]

11 minutes ago, Ser Scot A Ellison said:

I'd love to see the articles challenging the findings regarding the acceleration of the expansion of the Universe.  Would you mind sharing?

There's this one from Nature, but, as the sixth video in the list I pointed you to earlier explains, it's much less sensational than it sounds. The accelerating expansion is implied by several distinct measurements and disproving it is difficult. There are also explanations (example) which still posit an accelerating expansion, but try to do it without dark energy.

[Ser Scot A Ellison]

I found this article in which a team claims a larger dataset of "Type 1a" supernovea shows no acceleration but that the Universe is expanding at a constant rate.

 

http://www.sciencealert.com/no-the-universe-is-not-expanding-at-an-accelerated-rate-say-physicists

Could such a result bring back "steady state"?

[The Anti-Targ]

1 hour ago, Ser Scot A Ellison said:

TAT,

I'd love to see the articles challenging the findings regarding the acceleration of the expansion of the Universe.  Would you mind sharing?

I was mostly channelling my brother who is a physics PhD, but not a cosmologist. To whit a couple of extracts from his emails:

Quote

Way back around 2001 when people were getting Nobel Prizes for finding the accelerating universe, I recall I told a few ... that this could be hype.  I've always thought the supernova data could be misleading, but not being a cosmologist I had to stay silent.

Now it seems I might have been right all along:
http://slashdot.us15.list-manage1.com/track/click?u=aab6529d3675bd877963a652d&id=8b449cadba&e=59bbe8eb5b
Simulation Suggests 68 Percent of the Universe May Not Actually Exist

There folks have run new simulations that take into account better approximations for General Relativity which tentatively suggest the dark energy supposedly accelerating the universes expansion is mythical, and that ordinary matter can cause pockets of accelerated expansion.

I love this kind of science which debunks Nobel Prizes.  So many Nobel Prizes get awarded way too soon, and of course many too late or never.

And follow up comment to some questions:

Quote

Yeah, the improved GR sims still have an accelerating expansion, but I think the new research suggests the accelerated expansion is only in pockets. It is now in question globally.  There could be an average acceleration without a global acceleration depending on how one does the averaging. The problem is our universe is not like a balloon, it has no boundary.   So the simulations you see in the videos of the AVERA model are misleading, since they depict a sphere expanding.  Our universe is not a sphere!  So how one computes an average expansion acceleration is tricky. And currently the real expansion we see is poised on such a knife edge between eternal expansion and eventual collapse that I can imagine a little uncertainty could tip it either way.  Over the past 20 years it has just become almost blind orthodoxy that "observations" confirm a run-away expansion.  And I think that should now be put in doubt.  It might not be wrong, but I think there should at least be more circumspection.

Dark energy (a positive cosmological constant) is ultimately the only way global accelerated expansion can occur. That's because everything else that's known is gravitationally attractive, including radiation.  So the currently observed average accelerated expansion could be of a different character, it should not persist over time once galaxies and the bubble walls get thinned out enough. But the new AVERA sims do not rule out a positive cosmological constant either, they are just saying perhaps it is not a necessary hypothesis at this point in time.

 

[Altherion]

52 minutes ago, Ser Scot A Ellison said:

I found this article in which a team claims a larger dataset of "Type 1a" supernovea shows no acceleration but that the Universe is expanding at a constant rate.

 

http://www.sciencealert.com/no-the-universe-is-not-expanding-at-an-accelerated-rate-say-physicists

Could such a result bring back "steady state"?

This would be ever so much easier if you just watched the videos, but if you prefer not to, here's an article. The answer to your question is almost certainly no.

As far as I can tell, there are two distinct sources of the headlines. The first is the Nature paper I linked to above. This is ultimately the reference for the link in your post and it does not say what the link says. The Nature paper finds that from supernovae alone, there is roughly a 99.7% chance ("3 sigma") that the expansion is accelerating. Now, this is a surprising result because we expected something considerably higher, but it is nevertheless consistent with previous results. If this was the only proof of an accelerating expansion that we had, it would not be very convincing, but of course neither would the original measurement from 20 years ago. There are additional constraints from independent measurements (the amount of matter in the universe, the cosmic microwave background and baryon acoustic oscillations) which drastically increase our confidence in the acceleration of expansion.

So, why the headlines that say the expansion of the universe is not acceleration? It's hard to be sure, but I think what they did was stop at the 3 sigma result and conclude that since 3 sigma results are typically not very convincing, there is no conclusive evidence of the acceleration.

The second source is the AVERA simulation which The Anti-Targ's post above describes in considerable detail. This makes an interesting proposal: it does not question the fact that from our point of view the acceleration appears to be expanding, but it shows that under certain assumptions this might not be indicative of a universal acceleration of expansion. That is, our observable universe is a pocket of space in which the galaxies appear to be accelerating away from each other, but this is not true in the universe as a whole (which we cannot observe). This is worth considering, but the obvious question is how one would make a simulation of something one cannot observe. We'll have to wait and see whether this goes anywhere.

[The Anti-Targ]

What's steady state anyway? Regardless of accelerated expansion or not, we're eventually heading to heat death of the universe in several trillion years are we not? So under no scenario is there a steady state in the manner most people might think.