Vera Rubin R.I.P.
Vera Rubin, whose work helped confirm the existence of dark matter, passed away December 25 at the age of 88.
In the 1960s, Rubin’s interest in how stars orbit their galactic centers led her and colleague Kent Ford to study the Andromeda galaxy, M31, a nearby spiral. The two scientists wanted to determine the distribution of mass in M31 by looking at the orbital speeds of stars and gas at varying distances from the galactic center. They expected the speeds to conform to Newtonian gravitational theory, whereby an object farther from its central mass orbits slower than those closer in. To their surprise, the scientists found that stars far from the center traveled as fast as those near the center.
After observing dozens more galaxies by the 1970s, Rubin and colleagues found that something other than the visible mass was responsible for the stars’ motions. Each spiral galaxy is embedded in a “halo” of dark matter—material that does not emit light and extends beyond the optical galaxy. They found it contains 5 to 10 times as much mass as the luminous galaxy. As a result of Rubin’s groundbreaking work, it has become apparent that more than 90% of the universe is composed of this invisible material. The first inkling that dark matter existed came in 1933 when Swiss astrophysicist Fritz Zwicky of Caltech proposed it. But it was not until Rubin’s work that dark matter was confirmed.
Rubin was a top notch astronomer, which is why she was part of this important discovery. She was also an exception, as at the time relatively few women were interested in becoming astronomers. Be prepared, however, for a slew of articles in the next few days focused not about her work and her contributions to science, but focused instead almost entirely on the sexist oppression she had to overcome in the evil sexist male chauvinist society of mid-twentieth-century America.
All those articles will be wrong. While there were certainly obstacles in Rubin’s way because of her sex, they were hardly as bad as it will be made out to be. Worse, this focus on gender and oppression will distract from honoring the passing of a great astronomer. It will also distract from the significance of her discovery, which continues to baffle astronomers a half century later.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Vera Rubin, whose work helped confirm the existence of dark matter, passed away December 25 at the age of 88.
In the 1960s, Rubin’s interest in how stars orbit their galactic centers led her and colleague Kent Ford to study the Andromeda galaxy, M31, a nearby spiral. The two scientists wanted to determine the distribution of mass in M31 by looking at the orbital speeds of stars and gas at varying distances from the galactic center. They expected the speeds to conform to Newtonian gravitational theory, whereby an object farther from its central mass orbits slower than those closer in. To their surprise, the scientists found that stars far from the center traveled as fast as those near the center.
After observing dozens more galaxies by the 1970s, Rubin and colleagues found that something other than the visible mass was responsible for the stars’ motions. Each spiral galaxy is embedded in a “halo” of dark matter—material that does not emit light and extends beyond the optical galaxy. They found it contains 5 to 10 times as much mass as the luminous galaxy. As a result of Rubin’s groundbreaking work, it has become apparent that more than 90% of the universe is composed of this invisible material. The first inkling that dark matter existed came in 1933 when Swiss astrophysicist Fritz Zwicky of Caltech proposed it. But it was not until Rubin’s work that dark matter was confirmed.
Rubin was a top notch astronomer, which is why she was part of this important discovery. She was also an exception, as at the time relatively few women were interested in becoming astronomers. Be prepared, however, for a slew of articles in the next few days focused not about her work and her contributions to science, but focused instead almost entirely on the sexist oppression she had to overcome in the evil sexist male chauvinist society of mid-twentieth-century America.
All those articles will be wrong. While there were certainly obstacles in Rubin’s way because of her sex, they were hardly as bad as it will be made out to be. Worse, this focus on gender and oppression will distract from honoring the passing of a great astronomer. It will also distract from the significance of her discovery, which continues to baffle astronomers a half century later.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Bob, speaking of revisionist history, what’s your take on the NASA movie coming out soon called “Hidden Figures”? Based on the trailers it looks like it may be another Hyper-Victimization Movie where the hero-victim triumphs in spite of the Evil White Man.
You probably know how much of it is based on truth and how much is drummed up for the sake of Identity Politics.
Is this another example of history being bent to make a political point?
Steve: In a word, yes.
I ignore such films. They are anti-American propaganda, generally designed not to laud the achievements of the individuals portrayed but to denigrate the achievements of everyone else.
Steve/ Mr. Z.;
I would totally agree with the “anti-American” characterization. Anything to trash white, male, engineers, and slam the Country in the process.
The movie comes out in January & is based upon a book by Margot Lee Shetterly, called “Hidden Figures.” (Features Jim Parsons from Big Bang Theory, as well.)
https://www.c-span.org/video/?414833-1/margot-lee-shetterly-discusses-hidden-figures
Thanks Guys, I was afraid of that. My son saw that it had Astronauts and Dr. Sheldon Cooper in it, so now he wants to see it. Hopefully he will forget about it between now and when it opens….. LOL
Speaking of Dr’s, The Rev Martin Luther King must be rolling in his grave these days. We have gone from one extreme to the other. Everything is now identity politics and PC revisionism. Very Sad.
Boy, did you call that one Bob…… My local Planetarium (in a public high school!) has a FB page, and on that page today they re-posted an article from Astronomy.com about Vera Rubin passing. But just re-posting it wasn’t enough, they felt the need to add an editorial comment above the posting:
“Rubin confirmed the existence of dark matter while fighting against entrenched sexism.”
I didn’t follow the link to the article, so for all I know that’s a quote from it, but it just highlights what Mr. Z posted above. It’s not enough that she was an accomplished Scientist, they have to make sure we know she was a Triumphant Victim in the Social Justice Wars…..
” Each spiral galaxy is embedded in a “halo” of dark matter—material that does not emit light and extends beyond the optical galaxy. They found it contains 5 to 10 times as much mass as the luminous galaxy. As a result of Rubin’s groundbreaking work, it has become apparent that more than 90% of the universe is composed of this invisible material.”
Unless, it is not. As usual, I am skeptical. More matter, dark or not, would serve to pull a galaxy apart not make stars go faster in there revolution around the galaxy. There are hundreds of examples of galaxy collisions resulting in the elongation and disruption of the smaller galaxy. If there was an “90%” invisible matter “halo”, it would be rubbing up against other galaxies creating vortices which would tear apart the universe. There would be disruptions “the cause of” we would not be able to see or explain. Also this matter would have to be concentrated not to extend out so far therefore it would be in the form of dark stars, dark planets, dark energy… All of it invisible, undetectable except for a few outer stars moving faster than they seam that they should. This is unlikely bordering on fantasy.
I’m no scientist, and I do not have the answers. But I can pretend to. For instance the movement of the stars is as it would be if there is no central mass in a galaxy. The stars are not orbiting a supermassive black hole, they are attracted to each other. The mass of one side of the galaxy holding in check the mass of the other side. The stars moving faster will be relegated to the outer edge, trying to escape the combined gravity of billions of stars in the galaxy. The slower stars in the middle are pulled in both directions, without enough momentum to move beyond where they find themselves. (Think of a planets center. There is no gravity there because one side cancels out the other. The walls rotation is slow as compared to the crust) Their very existence is proof that there is no super massive black hole eating them. If there was, there would be a giant void in the center with fast moving stars around this void.
Apply Ochman razor, and you will rarely be wrong…. Only no one will believe you.
Max–
(I only play at being an Astrophysicist on the Interweb myself.)
As for super-massive black-holes, there’s a common misattribution that they “suck” everything into themselves. But that only happens with matter close by. As long as you stay beyond the event-horizon, you can orbit a black hole indefinitely without being sucked in.
Gravity is relatively weak– depends heavily on distance, and angular momentum is always conserved.
Our Galaxy’s Black Hole is Sagittarius A* —
Tracking Stars Orbiting the Milky Way’s Central Black Hole
https://youtu.be/duoHtJpo4GY
or, one with narration:
The Centre of a Galaxy “Supermassive Black Hole in the Heart of Our Galaxy” part 1
https://youtu.be/MDrY4g522q8
I really wish “they” hadn’t used the terms “dark energy” and “dark matter” as descriptors– I think it obfuscates what they really mean to say.
Not to say the Standard Model is complete in all it’s particulars, but it does get us most of the way. If we can figure out how to quantize gravity, then we are in business, big time.
Check this out if you have a spare hour– Public lecture, but hits on the high points:
http://www.gresham.ac.uk/lectures-and-events/the-search-for-dark-matter
I too am only a physicist on the inter web but I know this.
Newtonian physics doesn’t work on the small scale, therefore they had to imagine a new physics; Quantum Physics.
Why is it so hard to imagine Newtonian physics not working on the grand scale and having to invent something that is undetectable; dark matter to rescue the theory?
I consider dark matter to be on par with the unreproducible super-luminal expansion of the proto big bang to rescue a theory that has to be “adjusted” every time new data is obtained.
Maybe the observed macro variations somehow balance the observed micro variations to Einsteins theory of relativity and point toward a solution to the unified field theory?
I should ask my daughter who actually does have a degree in physics
Max noted: “The stars are not orbiting a supermassive black hole, they are attracted to each other.” and: “(Think of a planets center. There is no gravity there because one side cancels out the other.)”
I, too, am not a physicist, but my orbital mechanics class was full of interesting lessons.
Gravitational attraction works similarly to Max’s statement. Inside a planet of uniform density, if there were a hole drilled through the center, like a bead for a necklace, the gravitational pull would decrease linearly as we approach the center, where it would become zero. An orbit within such a gravitational field would not be the same elliptical orbit as it is on the outside of the planet, where gravity decreases as we get farther from (not nearer to) the center.
Galaxies have a similar observed mass distribution, except they are not so nicely uniform; large mass in the center, not much at the edges. If mass and gravity are the only things responsible for stars orbiting the center of galaxies, then the observations show that the distribution that we see does not adequately explain the observed speeds of the observable stars.
Vera Rubin’s use of Occam’s razor on the various hypotheses brought her to the conclusion that there is mass and gravitation that we have not yet observed.
The uncertainty of science suggests that this could be incorrect. Perhaps there are forces that act on galactic scales, and we do not have the means to measure or recognize such forces. After all, if we lived on electrons in atoms, would we recognize gravity?
However, for now, dark matter is the working hypothesis, and perhaps one day we will manage to find some.
Thank you all for your kindness and your comments, I truly am trying to understand how this all works and to wrap my brain around it.
Wayne, I watched your links, they were very informative. They talked about the stars orbiting Sagittarius A* and it would seem that only a few dozen stars are affected due to the inverse squared law of gravity. ( I find this law applies to heat and magnetism as well ) It does not have the mass, nor is it possible to have enough mass to hold a galaxy together as in Newtonian physics. According to her model, the slower stars are inside of the “central bulge”. The faster stars just outside the bulge and are traveling at the same speed as the furthest stars in the galaxy. Like a giant LP record. The dark matter is acting like glue holding every star in the same speed frame no matter your distance from the center.
You said, “I really wish they hadn’t use the phrase “dark energy” and “dark matter”, I think it obfuscates what they really mean to say”.
The woman giving the lecture would agree with you, she preferred the title “Clear Matter”
Also she admittedly had no clue what this would be. She even use the phrase similar to what I started my first post. Dark matter is Baryonic material ( vast amounts of dust, rock, planets, asteroids, brown dwarf stars, anything that does not give off light ) or it is something else…
Peter f, You are right in the point that they are turning to quantum physics to explain because they cannot see what the cause is. They brought up neutrons, positrons, cosmic radiation… at which point they brought up the most elusive particles in which all their hopes are now vested. Wimps. Weak massive particles emanating from the center of the galaxy. It reminded me of something I read before… Wikipedia on ether
In the late 19th century, luminiferous aether, aether or ether, meaning light-bearing aether, was the postulated medium for the propagation of light.[1] It was invoked to explain the ability of the apparently wave-based light to propagate through empty space, something that waves should not be able to do. The assumption of a spatial plenum of luminiferous aether, rather than a spatial vacuum, provided the theoretical medium that was required by wave theories of light.
The concept was the topic of considerable debate throughout its history, as “”it required the existence of an invisible and infinite material with no interaction with physical objects.”” As the nature of light was explored, especially in the 19th century, the physical qualities required of the aether became increasingly contradictory. By the late 1800s, the existence of the aether was being questioned, although there was no physical theory to replace it.
“Newton rejected light as waves in a medium because such a medium would have to extend everywhere in space, and would thereby “disturb and retard the Motions of those great Bodies” (the planets and comets) and thus “as it [light’s medium] is of no use, and hinders the Operation of Nature, and makes her languish, so there is no evidence for its Existence, and therefore it ought to be rejected”
I agree with Newton. This theory of ether, to make your point, is the best hypothesis they had until Einstein proselyted the “Theory of Relativity” so, we will wait until new evidence is found and a better theory comes about.
Edward, you are right that dark matter is the working hypothesis, but I still do not see the relevance in that it does not explain why all the stars are moving at the same speed… If dark matter has not glued them in place, then it is distributed in such a way that increases the velocity of a galaxies outer stars at the same time that it slows the inner ones. Dark matter would need to overlay the galaxy adding 90% more mass being distributed thicker at the center then moving outward but no farther than the edge of the galaxy. This explanation reminds me of “another dimension” perhaps that interacts with ours. Or a higher state of reality like Dr. Strange astral plane, Star trek subspace, Babylon 5 hyperspace… Or even infinite dimensions and realities linked by this quantum connection. All of which we cannot see or measure.
But it gets more complicated, apparently the same force is causing galaxies to collide. And not just move past each other and then on into infinite space… They are slowing down, coming around and slamming into each other until they combine. Galaxy clusters are found everywhere.
The only clue I have as to a possible key to the problem is the example i’ve used before to illustrate gravitational anomaly’s on earth. Why there would be a bulge caused by tidal forces in the opposite direction of gravity (Sun/Moon) in violation of all of gravity’s laws. They say it is inertia that causes it??? How could it cause a low tide at an exact right angle to the sun and moon? The only low tide by logic and theory would be on the opposite side of the planet facing away from the gravitational effect. And yet the difference between the two tides is 3%. I believe that is the only gravitational effect and that something else is causing the tides related to but not caused by gravity. ( we are in a constant state of freefall) If The sun and moon can pull the water up 6 feet higher, then using the inverse square law… Wouldn’t the Suns gravity, further from the earths surface, be able to pull the space station out of orbit?
Sorry about the book, I had days to think about this.
Max–
Appreciate your efforts. (I know it’s hard to whip up a coherent post, especially on such an all inclusive topic.)
[Gresham College does have a lot of material– public lectures– you might enjoy, wide range of topics including “space.” They have an excellent series on Newtonian gravity as well. Most but not all of their material is also hosted through YouTube.]
Reference the Earth’s tides; The Earth is not perfectly round & the Ocean’s are a fluid. There’s no anomaly as to what is going on in that regard. Gravitational forces of the Earth, Moon, and Sun, influence the motion of liquids on Earth.
Reference the ISS; Others are better equipped to explain why it orbits as it does. It’s always moving in a straight line, but it is always “falling” towards the Earth. I believe it’s correct to say, “velocity overcomes local gravity for orbits.”
Our Solar System is gravitationally bound to our Sun. Concurrently, our Sun is in orbit around our own galaxy, and our whole galaxy is busily zooming through space. (I believe the orbital period for our Sun is on the order of 250 million years, something like that.)
I believe it’s Galaxy M31 (Andromeda galaxy) that will eventually crash into our galaxy. We are both moving towards each other, although at different relative speeds.
Some galaxies are moving towards other galaxies, while some are moving away from others; depends on what galaxy you are in, where it is in space, what direction it is moving, and if its gravitationally influenced by other galaxies.
(There is no “center” of the Universe and we are not it.)
Concurrently– physical space between galaxies is always expanding, at a rate we believe is constant.
In the case of Andromeda colliding with the Milky Way galaxy, the space between us continues expanding, but not as fast as the relative motion between/toward the two, so they will eventually collide, despite the increasing space between us.
(I believe it’s safe to say as a general matter; “everything has an escape-velocity relative to everything else.”)
One point that is vital– Fritz Zwicky & Vera Rubin did not maintain that “all stars move at the same speed.” That’s not the argument.
Depending on ones distance from a “central mass point,” all of these objects should obey orbital-mechanics laws, but they don’t. And as Edward noted– one explanation would be that there is additional mass, that we can not see or detect given our current methods & understanding.
Stars in outer spiral-arm locations of galaxies, are not moving at the same speed we would predict they move given the mass for which we can readily account.
Angular momentum and speed are always conserved quantities.
“Space” is not infinite in size, although we strongly believe it will continue to expand into “infinity.”
At a minimum, the observable universe is 14 billion light-years (spherically) in size, although there are valid reasons to suspect the true physical size is 3-5X’s that number.
In the distant (distant) future, the only stars we will be able to see, are those in our own galaxy (and M31 as it approaches us & vice-versa)– the other galaxies will all eventually recede out of our view, as space continues to expand.
It’s early & I need my coffee, so excuse my brevity.
Personally, I’m not a string-theory guy myself
I never pass up an opportunity to shill for Dr. Roger Penrose and his theories.
You might find him interesting.
>>Even if you don’t agree with his conclusions, he does an excellent job explaining factoids of which we are pretty confident which lead up to his theory.
Conformal Cyclic Cosmology (Roger Penrose)
https://youtu.be/FBfuAVBdcW0
And while I’m at it– I’ll throw in
“Quantizing gravity, and why it is difficult”
by Leonard Susskind (He explains why he thinks it’s impossible to do so)
https://youtu.be/yK4rhkcsQDc
and if I’m going to be moderated, I’ll throw in this link as well:
Gravity and Quantum Mechanics
– The Quest for Unification
Joe Polchinski
https://youtu.be/FqwXeeXnDZg
(Personally, I’m not a string-theory guy myself, but that’s just a personal preference.)
PeterF– you broach some interesting topics, but I need my coffee first.
Personally, I see no reason Newtonian Physics wouldn’t explain correct motion on large scales.
That having been said, Newtonian Physics only works at “normal” scales. (Defining what is “normal,” is the rub.) Objects or Particles which move at relativistic speeds, start to get one into the Quantum and Relativity mode of gravity.
If we are taking a Vote– I suggest we have one of these “cosmology type” threads every few weeks or so, it’s a fascinating topic.
Max– highly recommend this presentation from Dr. Penrose.
It’s tangential to dark-matter, but interesting nonetheless.
(Does address, in part, some of what PeterF was getting at…)
Roger Penrose
Twistors and Quantum Non-Locality
2011
https://youtu.be/hAWyex1GKRU
Max wrote: “This explanation reminds me of “another dimension” perhaps that interacts with ours.”
Oh, boy! This gets into quite another interesting topic: string theory — which is actually a hypothesis, since no experiments have yet supported it. String theory requires additional dimensions that we have yet to measure.
Talking about additional dimensions brings up more interesting topics. For instance, we talk about physical bodies as having six dimensions of freedom: three physical/directional (x, y, z) and three rotational (pitch, yaw, roll). Generally, we do not think of these rotational dimensions like we do the directional dimensions.
Which makes me ponder the possibility that the attribute of mass being — or is related to — another dimension, because then our basic system of units (time, distance, mass) would be based solely on various dimensions, in this case five dimensions, rather than the four we currently think of them as.
Then there is the unobserved dimension that must exist in order for space to curve, like the 2D models that help visualize the curvature due to gravity or the balloon demonstration to visualize the expanding universe.
Like the ether hypothesis, I worry about the correctness of dark matter and dark energy hypotheses. But like the ether hypothesis did, they help us to explain what we see in the universe.
Remember, we keep learning more and more as we explore. We have come a long way since the days when we thought that the world was the back of an enormous turtle, which was held up by another turtle, which was held up by other turtles all the way down. (I have to admit, the “turtles all the way down” story is a 20th century creation, but it brings up questions of foundations and original creation.)
wayne wrote: “There is no “center” of the Universe and we are not it.”
Speak for yourself. You may not be the center of the Universe, but I am. And one of these days I will come up with a hypothesis as to why and how the whole universe revolves around me.
wayne wrote: “Angular momentum and speed are always conserved quantities.”
That is a slight misstatement. It is not speed that is conserved but energy, where kinetic energy is related to speed, but can be converted into potential energy (related to height), as when a ball is thrown upward. Both speed and height are related to escape velocity.
Also, speed and height energies can be converted into heat energy, as with reentry bodies. But I am complicating what was supposed to be a simple explanation. Energy and momentum, including angular momentum, are conserved, even when the energy is converted into mass. There I go complicating it, again.
Life was so much simpler, back when it was turtles all the way down.
Whether it turns out to be right, wrong, or eventually needs modification, Vera Rubin made an important contribution to cosmology.
Edward–
Good stuff.