The Future of CMB Exploration

You would think that once the cosmic microwave background (CMB) has been discovered and studied, that was the end of it. That is not how science typically works, especially on something that has such a rich amount of information as the CMB.

This article reports on the next proposed major research effort in the US in further studying the CMB and refining the measurements that we currently have. The article gives you a good over view of what we currently know about the CMB, what we wish to extract out of it, and how it can be done. This appears to be a joint effort between two major science funding agencies in the US: the US Dept. of Energy and the US National Science Foundation, and will have an estimated cost of $650 million.

As someone who likes to include contemporary and most recent relevant news into my lessons, this will be another item that I will include in my Intro to Astronomy class.

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Total Amount of Matter in the Universe

We now have the most accurate measurement to date of the total amount of matter in our universe. A new paper published in The Astrophysical Journal[1] seems to indicate that our universe is composed of 31% matter, with the rest being dark energy.

And of that 31% of matter, 80% of that is dark matter, which we are still searching for. This means that the "ordinary matter" that is known within the Standard Model of elementary particle and that makes up you and I is only about 6.2% of the entire matter+energy of our universe. The remaining 93.8% are made up of "dark" stuff, i.e. dark energy and dark matter.

This means that we still do not know the nature of a huge portion of what makes up our universe. Would it be nice to be alive 50 or 100 years from now when we know more about these things then (hopefully!).

Z.

[1] https://iopscience.iop.org/article/10.3847/1538-4357/aba619

First Hint of CP Violation in the Neutrino Sector

The latest report on T2K results has been published[1], and it looks good for the upcoming long neutrino baseline experiment at DUNE and T2HK. The result may suggest that these two upcoming experiments may finally nail down CP violation in neutrinos, which will be a substantial advancement in our understanding on why there are more mater than antimatter in our universe.

The discovery of substantial leptonic CP violation would be groundbreaking. Its observation, together with evidence that a quantity known as lepton number has been violated (that is, not conserved), would provide strong circumstantial evidence for leptogenesis as the origin of the matter–antimatter imbalance.

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[1] T2K collaboration, Nature v.580, p.339 (2020).

What Really Happened At The Big Bang?

Don't you want to know?

Here is a simplified explanation of what the Big Bang is, and what the Big Bang is NOT!



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Einstein's Blunder Explained

This, actually, is a good and quick summary of the Einstein cosmological equation by Minute Physics. You'll get a brief history of the cosmological constant, and how it came back to life.



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What Is Dark Matter And Why Does It Matter?

First of all, let me explain something If you are not in an academic institution, or a research facility, etc., you may not know that for many of us, having regular, sometime weekly, colloquium or seminars is quite common. This is where we invite experts in various topics come to our institution or department and present a talk on a particular subject. I, myself, have given such seminars. This is how we learn about many things, often topics outside of our expertise or area of studies, and we learn about these things from authorities in these various fields. It is one of the unique privileges that we enjoy being in such an environment.

In other words, we do not learn about these topics from popular media, or even from 2nd or 3rd hand sources. And this usually takes time, i.e. it can't be done in short sound bites or in a few minutes.

I'm prefacing this video with such information because this is an example of a colloquium that we typically attend, and if you are not used to it, it may appear tedious to sit through an hour of such presentation. But there is usually no other way to learn about things, especially if you wish to learn about something beyond just a superficial level.

I've mentioned about dark matter many times on here, but here's another one. It is presented in a manner that even non-scientists may understand, even if you do not understand some of the intricate details.



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Multiverse

In this article, Ethan Siegel valiantly tried to explain, in simple language, what "multiverse" is within the astrophysical/cosmological context:

Inflation doesn't end everywhere at once, but rather in select, disconnected locations at any given time, while the space between those locations continues to inflate. There should be multiple, enormous regions of space where inflation ends and a hot Big Bang begins, but they can never encounter one another, as they're separated by regions of inflating space. Wherever inflation begins, it is all but guaranteed to continue for an eternity, at least in places.

Where inflation ends for us, we get a hot Big Bang. The part of the Universe we observe is just one part of this region where inflation ended, with more unobservable Universe beyond that. But there are countlessly many regions, all disconnected from one another, with the same exact story.

Unfortunately, as is the problem with String theory, none of these have testable prediction that can push it out of the realm of speculation and into being a true science.

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Dark Energy Levels Not Too Constrained For Star Formation

I've always had a bit of a problem with the anthropic scenario of our universe, i.e. the idea that we are living in a universe JUST fined-tuned to allow us to exist. My problem isn't with the observations so far, but rather how much people are already thinking that this must be true, the data are set, and that we can run away with it. Certainly many people outside of cosmology have tried to spin this into whatever directions that they want.

So when news like this comes along, I just want to yell "I told you so!". It is not that I agree or disagree with the conclusion, but it is to point out that in our attempt to understand all of this, our knowledge is still in its infancy, and that we really don't know enough yet to be able to say things one way or the other on many of the big issues. We do have a fuzzy idea on what direction it is going, but in a number of things and observations, more is required to understand things even better.

The new studies ran the simulation on the star formation of our universe against the amount of dark energy in our universe. They can, to put it crudely, dial in various level of dark energy in their simulations. They found that there is a wider range than initially expected for our present universe to form, i.e. it is not in a very narrow range that was thought of. So keeping everything relatively the same, we could see this present universe that we're in for a large range of dark energy.

The simulations allowed the researchers to adjust the amount of dark energy in the universe and watch what happened.

The results were a surprise. The research revealed that the amount of dark energy could be increased a couple of hundred times – or reduced equally drastically – without substantially affecting anything else.

So for dark energy, the parameter is not as "fine tuned" as one expected.

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https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/sty846/4963750?redirectedFrom=fulltext

https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/sty879/4966995?redirectedFrom=fulltext

Hawking's Final Paper Is Published

The late Stephen Hawking's final paper written while he was alive, has been published. You can get the full version of it at that link.

If you missed it, read Ethan Siegel's earlier explanation of the paper.

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The Friedmann Equation

Astrophysicist Ethan Siegal picked the Friedmann equation as the "most important" equation in the universe.

The first Friedmann equation describes how, based on what is in the universe, its expansion rate will change over time. If you want to know where the Universe came from and where it's headed, all you need to measure is how it is expanding today and what is in it. This equation allows you to predict the rest!

I don't have the "most important equation" in the universe for my pick, mainly because I don't know the criteria for picking such a thing. And often times, people confuses "interesting" with "important", which need not be mutually inclusive.

It's still fun to read what other physicists think is the most important equation, even if I don't necessarily agree with their picks.

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What Astronomers Wish You Know About Dark Matter And Dark Energy

If you do a search of this blog, you will encounter numerous entries on both "dark matter" and "dark energy". It is something I've covered quite often, mainly because it is still an ongoing and active research area in astrophysics/astronomy/cosmology. Even high-energy physics/elementary particle physics is getting into the picture with particle astronomy.

In this article, Ethan Siegel gives you a condensed version of what "dark matter" and "dark energy" are, and what you need to know about them. But more importantly, if you think that you can discard them, you need to do more than just say that they are not needed.

It wasn't always apparent that this would be the solution, but this one solution works for literally all the observations. When someone puts forth the hypothesis that "dark matter and/or dark energy doesn't exist," the onus is on them to answer the implicit question, "okay, then what replaces General Relativity as your theory of gravity to explain the entire Universe?" As gravitational wave astronomy has further confirmed Einstein's greatest theory even more spectacularly, even many of the fringe alternatives to General Relativity have fallen away. The way it stands now, there are no theories that exist that successfully do away with dark matter and dark energy and still explain everything that we see. Until there are, there are no real alternatives to the modern picture that deserve to be taken seriously

It might not feel right to you, in your gut, that 95% of the Universe would be dark. It might not seem like it's a reasonable possibility when all you'd need to do, in principle, is to replace your underlying laws with new ones. But until those laws are found, and it hasn't even been shown that they could mathematically exist, you absolutely have to go with the description of the Universe that all the evidence points to. Anything else is simply an unscientific conclusion.

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An Astrophysicist Describes Stephen Hawking's Last Paper

The astrophysicist in this case is, of course, Ethan Siegel, who I've cited here a few times.

In this article, he describes what Hawking's last paper is all about, if you want simple description of it. The link to the preprint (we'll update this post if and when it is published) is also given if you don't have it already.

Here is, in a nutshell, what they do. They create a (deformed) conformal field theory that is mathematically equivalent (or dual) to an eternally inflating spacetime, and investigate some mathematical properties of that field theory. They look, in particular, at where the border of a spacetime that inflates for an eternity (forward in time) versus one that doesn't, and choose that as the interesting problem to consider. They then look at the geometries that arise from this field theory, try to map that back onto our physically inflating Universe, and draw a conclusion from that. Based on what they find, they contend that the exit from inflation doesn't give you something eternally inflating into the future, with disconnected pockets where hot Big Bangs occur, but rather that the exit is finite and smooth. In other words, it gives you a single Universe, not a series of disconnected Universes embedded in a larger multiverse.

There! Do you even need to read the actual paper after that?

😁

BTW, let's also give some love to his co-author, Thomas Hertog, who seems to be left out in many of this discussion and news articles.

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Thermal Footprints of Early Stars

Imagine being able to detect signals coming from the first stars formed in our universe, almost 180 million years after the Big Bang. This is why this astounding feat has been receiving popular media coverage.

A new paper published in Nature this week reports on the measurements of thermal radiation from such events.

A long-standing theory that still awaits testing predicts that absorption of UV radiation from early stars by nearby clouds of hydrogen could have driven T_S back down to T_G, but not lower. In other words, the cosmic dawn would make the gas seem colder when observed at radio frequencies. This would create an absorption feature in the spectrum of the background radiation left over from the Big Bang.

Bowman et al. now report the possible detection of just such an absorption signal. The authors measured T_S , averaged over much of the sky and over a contiguous range of radio frequencies; each frequency provides a window on a different time in the Universe’s past. The measurement is very difficult because it must be performed using an extremely well-calibrated VHF radio antenna and receiver, to enable the weak cosmological signal to be separated from much stronger celestial signals and from those within the electronics systems of the apparatus used. 

For those of you who are not familiar with science, when you read the link, please read how the experimenters made the effort to ensure that their results are not due to their experimental technique or instrumentation.

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New Measurement of Hubble Constant Brings New Puzzle

The most extensive measurement of the Hubble constant based on observations made by the Hubble telescope (how appropriate) has revealed a discrepancy between its value and those made earlier by ESA's Planck satellite.

Planck’s result predicted that the Hubble constant value should now be 67 kilometers per second per megaparsec (3.3 million light-years), and could be no higher than 69 kilometers per second per megaparsec. This means that for every 3.3 million light-years farther away a galaxy is from us, it is moving 67 kilometers per second faster. But Riess’s team measured a value of 73 kilometers per second per megaparsec, indicating galaxies are moving at a faster rate than implied by observations of the early universe.

The Hubble data are so precise that astronomers cannot dismiss the gap between the two results as errors in any single measurement or method. “Both results have been tested multiple ways, so barring a series of unrelated mistakes,” Riess explained, “it is increasingly likely that this is not a bug but a feature of the universe.”

The arXiv version of the paper can be found here.

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Why Did Matter Matter?

Ethan Siegel has yet another nice article. This time, he tackles on why we have an abundant of matter in our universe, but hardly any antimatter, when all our physics seems to indicate that there should be equal amount of both, or simply a universe filled with no matter.

I have highlighted a number of CP-violation experiments on here, which is something mentioned in the article. But it is nice to have a layman-type summary of the baryo-lepton-genesis ideas that are floating out there.

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Determining The Hubble Constant

Ethan Siegel has a nice article on the pitfalls in determining one of the most important constants in our universe, the Hubble constant. The article describes why this constant is so important, and all the ramifications that come from it.

As you read this, notice all the "background knowledge" that one must have to be able to know how well certain things are known, and what are the assumptions and uncertainties in each of the methods and values that we use. All of these need to be known, and people using them must be aware of them.

Compare that to the decision we make everyday on things we accept in social policies and politics.

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Biggest Highlight of the Year

This is the last day of 2017, and man, what a year it has been.

To me, the most monumental discovery and event of the year is the serendipitous observation of the merging of two neutron stars. This celestial event was observed by both conventional astronomical observatories via the detection of EM radiation (light), and by VIRGO/LIGO, which detected the gravitational waves. To many people, this marks the distinct beginning of gravitational astronomy.

There are already papers pouring out of this event, and many more to come. There are already strict constraints on alternative gravitational theories just from this one event. I expect many more to fall as we continue to shake the tree.

Who knows if such an event will occur again some time soon (or within my lifetime), but this is exciting stuff where a new channel and method to observe such event has opened up. I definitely consider this as one of the top monumental discoveries in my lifetime.

Happy New Year, everyone!

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The Universe's First Atoms Verify Big Bang Theory

The Big Bang theory makes many predictions and consequences, all of them are being thoroughly tested (unlike Intelligent Design or Creationism). These predictions and consequences are quantitative in nature, i.e. the theory predicts actual numbers.

Many of these "numbers" have been verified by experiments and observations, and they are continually being measured to higher precision. This latest one comes about from the prediction of the amount of certain gases during the early evolution of our universe.

But more data has just come in! Two new measurements, in a paper just coming out now by Signe Riemer-Sørensen and Espen Sem Jenssen, of different gas clouds lines up with a different quasar have given us our best determination of deuterium's abundance right after the Big Bang: 0.00255%. This is to be compared with the theoretical prediction from the Big Bang: 0.00246%, with an uncertainty of ±0.00006%. To within the errors, the agreement is spectacular. In fact, if you sum up all the data from deuterium measurements taken in this fashion, the agreement is indisputable.

The more they test it, the more convincing it becomes.

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Host Interrupts Female Physicst Too Much, Audience Member Intervened

Hey, good for her!

The moderator of this panel interrupted physicist Veronika Hubeny of UC-Davis so much that audience member Marilee Talkington (appropriate name) got so frustrated that she intervened.

While watching a panel titled “Pondering the Imponderable: The Biggest Questions of Cosmology,” Marilee Talkington noticed that the moderator wasn’t giving physicist Veronika Hubeny, a professor at UC Davis and the only female on the panel, her fair share of speaking time.

So when the moderator, New Yorker contributor Jim Holt, finally asked Hubeny a question about her research in string theory and quantum gravity, then immediately began speaking over her to explain it himself, Talkington was furious.

Fed up with the continuous mansplaining, Talkington interrupted Holt by yelling loudly, “Let her speak, please!” The crowd applauded the request. 

You can read the rest of the story here.

Certainly, while it is awfully annoying, based on what Dr. Hubeny described, she didn't think it was a blatant sexism. Rather, she thought that the host was just overly enthusiastic. But you may judge that for yourself if the host didn't give the only female member of the panel a chance to speak.

But yeah, good for Ms. Talkington for intervening.

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Dark Energy Is Not An Illusion

This is a good intro to Dark Energy if you want to know more about it. Even if you don't buy into Ethan Siegel's argument, you at least have a good description of what we know of about Dark Energy at the moment, and why certain explanations for what have been observed have been ruled out.

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