Comments of the Week #60: from the entire Universe to sexism in science

“I do not think, sir, you have any right to command me, merely because you are older than I, or because you have seen more of the world than I have; your claim to superiority depends on the use you have made of your time and experience.” -Charlotte Brontë

Our exploration of the Universe, near and far, continues here on Starts With A Bang, as we've looked at the entire Universe, our local corner of it, dark matter and even the most human of issues. Make sure you catch up on anything you missed, including:

• The shape of the Universe (for Ask Ethan),
• The friends star (for our LEGO-rich Weekend Diversion),
• The Milky Way's most recent supernova (for Mostly Mute Monday),
• The science of the local group,
• Dark matter: giver of life, and
• Stop sexism in science (for Throwback Thursday).

In addition to these, I had two new pieces appear over at Forbes that give us a deep glimpse into our Universe as well:

• Even Cosmic Distances Need To Be Adjusted For Inflation, and
• NASA's New Images Of Our First Asteroid, Ceres, Sheds Light On Its Greatest Mystery.

As always, you didn't disappoint with all you've had to say, so let's dive into your Comments of the Week!

Image credit: Christopher Vitale of Networkologies and the Pratt Institute.

First, a comment from Erik Martino Hansen: "How space can be perfectly flat and at the time of the big bang have had a finite size. [...]It is possible to be flat and finite in size without some kind of edge?"

It is very, very much possible to be perfectly flat and have a finite size. Think of -- if you like two dimensions -- a flat sheet of paper. You can imagine the paper extending in all directions infinitely, or you can imagine just a finite sheet of it; so long as our observable Universe is smaller than the true size, we'd never know the difference. Think now, if you want it to be flat, finite and edgeless, what could you do? Well, if you "rolled up" one dimension to make a cylinder, and then "rolled up" the other to connect in a donut/torus-like shape, you'd have a flat, edgeless Universe.

I'm not the first nor the only person to point this out; an additional great answer came from our diligent, particle physicist commenter Michael Kelsey, who added:

We don’t know whether “space” (the larger system of which our whole observable universe is a part) is finite or infinite. We don’t know whether it has an edge, or is a closed, unbounded surface. The inflationary hypothesis is close to your option (1): The expansion rate was so fast that an initially tiny patch could grow immensely in a very short time. The consequence is that our observations correspond to a tiny patch of that tiny patch, so we don’t know about what’s “outside.”

We do know (observationally) that our observable universe, currently 46 billion light years in radius, is at least five times larger than that (if it were smaller, there would be observable features in the CMB). We know that it is not a closed flat surface (like a torus), because we do not have observations of repeated structures in the CMB (that is, we aren’t seeing “all the way around” the Universe multiple times).

The only thing I'll add to this is that the latest SDSS observations of baryon acoustic oscillations have placed the curvature constraints to be so tight that, so long as the Universe isn't topologically closed, the radius of curvature (either positive or negative) is constrained to be at least fifty times as large as the portion of the Universe presently observable to us. (As of January, 2015.)

Image credit: NASA/WMAP Science Team.

From Tjd on the shape of the Universe: "[This article] finally cleared up the shape of the universe for me. Great article got me thinking. We may never know the true shape because of the limitation of light."

This is factually accurate. As more and more time goes by, we can see farther and farther back into the Universe's past, and to greater and greater cosmic distances. But the Universe's expansion is accelerating! So even though -- as time goes on -- we're seeing out to greater distances in the Universe than ever before, we're never going to see arbitrarily far, and learn whether the Universe has a "true shape" that's different from perfectly flat.

Unless there's some great, cosmic conspiracy afoot, it's very likely that the Universe we see will forever be indistinguishable from flat on the largest, global scales.

Image credit: Steve Price, of The Friends Star, via flickr at https://www.flickr.com/photos/pricey73/16736883714/in/album-72157652349….

From This story is limp as fuck on the LEGO friends star: "This is the werdist thing i have ever seen, and im 11 so yea!"

Stick around, kid. It gets a lot werder from here. I have a feeling you're gonna like it.

Image credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: R. Fesen (Dartmouth College) and J. Long (ESA/Hubble).

From Omega Centauri on our galaxy's most recent supernova: "I would place high odds, that there have been other “invisible” [M]ilky [W]ay supernovas since then. Cas A was easy to detect because it was nearby and radionoisey, and not behind the inner regions of the galaxy, where the dust is much thicker. In fact there have probably been several."

This is actually an outstanding bet, Omega. When you look around at our galaxy, it's true, the galactic plane obscures practically everything (in the optical) with its copious amounts of dust. But it's that very same region -- replete with gas and dust -- which is where the vast majority of new stars and star clusters form. We took a look at that not too long ago on a previous Mostly Mute Monday.

If the dust weren't there, you'd imagine we'd be able to see these newborn stars crackling away, and when they run out of fuel, we'd be able to see their spectacular fireworks shows. For a long time, technology was simply incapable of detecting these. While the Cas A supernova remnant was first found in the radio in the 1940s, there's more likely a more recent one: Supernova Remnant G1.9+0.3, near the galactic center itself.

The image above, taken from 11 days' worth of Chandra data, is of a supernova remnant so young it was thought to have occurred only in the late 1800s. It was first observed by the Very Large Array of radio telescopes in the 1980s, but by time Chandra observed it again in the 2000s, it had increased in size by ~15%, indicative of an age of less than 150 years!

Now, there's too much we don't know about this object for certain to be completely sure that this is what we think it is, but it's very likely. Considering that Milky Way-sized galaxies typically display one-to-four supernovae per century, we may have had even more since then. Time -- and better observations -- will be the only way to tell.

Image credit: NASA, ESA, Z. Levay and R. van der Marel (STScI), T. Hallas and A. Mellinger.

From eric on the science of the local group: "The series of artistic renderings showing the merger of Andromeda and the Milky way are interesting, but it leaves me wondering a couple things.
1. Is this really accurate (in terms of how the sky would look at various points in our future)?
2. Will the Milky Way merge with any of the smaller galaxies in our local group before we merge with Andromeda?
3. If so, what would those mergers look like? Equally spectacular? After all, the other objects in the local group may be small compared to Andromeda, but they’re still galaxies."

So there are three separate questions here, and I'll do my best to take them all on. First off, no, this isn't really accurate, in the sense that Earth will continue to move, stars will live-and-die (and move relative to us), new, bright ones will appear and disappear, and the individual details of what we see are not able to be represented accurately. The overall gist of what we're illustrating is right, but the individual details are most likely grossly incorrect.

For your second and third questions, there are many, many small, dwarf galaxies that are merging with us all the time. While we say that there are a few larger ones in our local group: Andromeda, the Milky Way, Triangulum, and the Large Magellanic Cloud, the reality is that there are 50+ discovered dwarf galaxies, and probably many more still undiscovered. Most of them will eventually merge with either us or Andromeda, and some of them are merging with us right now.

In particular the Canis Major Dwarf and the Sagittarius Dwarf Galaxy are both in the process of merging with ours, similar to how a small galaxy is merging and being ripped apart, tidally, by NGC 5907, above. These things are anything but spectacular to an interior observer, and are incredibly difficult to detect at all; they will not change the size, shape, structure or night sky of hardly anyone in our galaxy.

My advice? Wait for the big one. It's only a major merger -- where major is defined by having a galaxy of at least a third the mass of the one you're in -- that will really disrupt the structure of your galaxy, and have a chance to turn a spiral galaxy into an elliptical. The only galaxy in our local group that meets that criterion is Andromeda; everything else, even the Triangulum galaxy, is minuscule (less than 10% of our mass) compared to us.

Image credit: ESO/L. Calçada.

From Soegeng Wibowo on dark matter: "Can dark matter have antigravity?"

And the answer from commenter Wow: "No."

People misuse the term "antigravity" all the time, using it to refer to any sort of repulsive force. Electromagnetism is not antigravity; radioactive decay is not antigravity; buoyancy is not antigravity; even dark energy is not antigravity. An anti-gravitational force would be something that acted just like the gravitational force, except with the opposite sign, as though something had negative mass (or energy).

As far as we can tell, no such thing exists in the Universe, and there is no phenomenon that indicates such a thing exists.

Image credit: Ayodhya Ouditt/NPR, via UNC Charlotte at http://advance.uncc.edu/news/2012-07-13/how-stereotypes-can-drive-women….

And finally, there were many many many comments on this issue, but here's an excerpt of one by Denier, on the issue of sexism in science: "The motivation for the posting of this article was a set of comments made about the appearance of Amanda Peet. One of the comments was singled out for shaming was as follows:
Not the Amanda Peet you’re thinking of, I’m afraid.
http://individual.utoronto.ca/amandapeet/
This comment was in response to another poster who had conflated Amanda Peet the Physicist and Amanda Peet the Celebrity. For making this comment, this poster who had absolutely no history of making sexist comments and arguably didn’t even make one here, was tarred as a sexist in a subsequent post by Ethan.
While this massive overreaction in the noble effort to have all people treated as people seems to be harmless or even helpful, that view is naïve. Unfortunately there is no shortage of naïve people. The quick jump to outrage on display here is not uncommon."

I understand where you're coming from, here. What you're saying is:

1. I didn't do anything wrong.
2. I certainly didn't do anything sexist.
3. I made a joke -- a quite funny joke -- about someone's name, that happens to be identical to another name.
4. And because of this, I'm being wrongly accused, perhaps even convicted, of being a sexist, when I am not in any way.

Right?

Now, I don't know Amanda Peet personally, but I do know them professionally -- from their work -- and from their web presence, webpage and publications. Some of those things are not for me to share with you, but perhaps others are.

This, above, is Amanda Peet, the actress. And this, below, is Amanda Peet, the physicist.

So I want you to imagine that you're Amanda Peet, the string theorist. You're already a rarity: a woman in a heavily male-dominated field. You've got the same name as a famous, young, beautiful actress who's far more famous than you are, and if people weren't already judging you on your looks, speculating about your sexuality and gender identity (hint: they were), you just happened to get dealt a hand of cards that make that all the more likely.

Did you do anything wrong, Denier, by making that observation? Not in isolation, but you've got to realize that you are not in isolation. You are not the first person to make that joke, it is not a funny (or new) joke, and it's one that just serves as a reminder that no matter how professional someone is, if that person happens to be different in some way from what you expect them to be, that will be the first and perhaps foremost thing that person will be judged on.

We do have a problem in many STEM fields in particular that make it a discouraging (and sometimes an outright hostile) environment for people who aren't straight, white men to make careers out of. It isn't only STEM fields, of course, but that's where I work, that's what I experience, and that's the one thing I can stand up and say, "I want to make this a better work environment for everyone who wants to work in this environment."

So whether you're sexist or not isn't the issue. Whether you mean to discourage women or not isn't the issue. Whether you think someone should be strong enough to get hit with a freight train of unfairness and shrug it off isn't the issue. In short, it isn't about you at all, and I couldn't care less about what you feel you're being accused of, fairly or unfairly. It's about demanding that people be treated with respect as they would like to be respected.

You will mess up; I will mess up; all of us will mess up at some point. But when we do, the proper response is not, "I didn't do anything wrong," but to learn what we can do to not mess up again, and to create a better, safer, more inclusive environment for everyone who wants to be in it. That's not the case right now, and that very fact -- that the environment as it exists right now is harsher for women than men -- is why I say it's sexist, and that there is institutional sexism. Not that you're sexist, but that sexism exists, it has these effects, and that if we want this situation to get better, it's up to us all to do something positive about it.

You don't have to agree with me, in fact I suspect many of you won't, but that's my stance on it, and that's one of the things I'll keep fighting and advocating for.

So thanks for a great week, everyone, and I'll see you back here next week for more wonders, joys and stories of the Universe!