What Was It Like When The Universe First Created More Matter Than Antimatter?
“This is only one of three known, viable scenarios that could lead to the matter-rich Universe we inhabit today, with the other two involving new neutrino physics or new physics at the electroweak scale, respectively. Yet in all cases, it’s the out-of-equilibrium nature of the early Universe, which creates everything allowable at high energies and then cools to an unstable state, which enables the creation of more matter than antimatter. We can start with a completely symmetric Universe in an extremely hot state, and just by cooling and expanding, wind up with one that becomes matter-dominated. The Universe didn’t need to be born with an excess of matter over antimatter; the Big Bang can spontaneously make one from nothing. The only open question, exactly, is how.”
One of the biggest unsolved questions in physics today is how the Universe came to be filled with matter and not antimatter. After all, the laws of physics are completely matter-antimatter symmetric, and yet when we look at what we have today, every planet, star, and galaxy is made of matter and not antimatter. How did it come to be this way? The young, hot, but rapidly expanding-and-cooling Universe gives us all the ingredients we need for this to occur. We are certain of the exact mechanism, but theoretically, there are some enticing possibilities. Here’s a walk through one of those scenarios in great detail, but expressed so simply that even someone with no physics knowledge can follow it.
Here’s what the Universe was like when it was matter-antimatter symmetric, along with how it could have become matter-rich without breaking the laws of physics.
What Is (And Isn’t) Scientific About The Multiverse
“In this physical Universe, it’s important to observe all that we can, and to measure every bit of knowledge we can glean. Only from the full suite of data available can we hope to ever draw valid, scientific conclusions about the nature of our Universe. Some of those conclusions will have implications that we may not be able to measure: the existence of the multiverse arises from that. But when people then contend that they can draw conclusions about fundamental constants, the laws of physics, or the values of string vacua, they’re no longer doing science; they’re speculating. Wishful thinking is no substitute for data, experiments, or observables. Until we have those, be aware that the multiverse is a consequence of the best science we have available today, but it doesn’t make any scientific predictions we can put to the test.”
The multiverse is one of the most controversial topics in science today. On the one hand, it’s a remarkable story: perhaps our Universe, even beyond what we can observe, isn’t the only one out there. Perhaps there are many others, all generated in some early, pre-Big-Bang state, all disconnected from one another. This isn’t speculation; this part of it arises by combining the two well-established theories of cosmic inflation and quantum physics. Yet if we start trying to go further, such as making statements about the laws of physics, the values of fundamental constants, or the suitability of our Universe for life, we’ve lept out of the realm of science and into wild speculation or, worse, wishful thinking.
Come find out what is (and isn’t) scientific about the multiverse, and add a little bit of nuance to something you likely already have strong opinions on!
The Pillars Of Creation Haven’t Been Destroyed, Say New NASA Images
“Near-infrared observations can see through the dust, revealing a glittering tapestry of young, hot stars inside. But at longer wavelengths, cooler-temperature objects show up. Mid-infrared light revealed that a diffuse heat source was warming the nebula, suggesting a recent supernova. While the far-infrared showed where the gas is evaporating, we needed X-rays to know if the pillars were being destroyed.”
In a stunning new release, NASA’s Chandra X-ray observatory has put out a wide-field view of a large portion of the Eagle Nebula, including the famed Pillars of Creation. All told, some 1,700 X-ray sources were identified, perhaps 2/3rds of which are inside the nebula. There are proto-stars, young stars, and stellar corpses. But conspicuously missing from the entire field-of-view is any evidence of a supernova remnant. In 2007, infrared data from Spitzer suggested that there may have been a recent supernova, and hence the pillars may already have been destroyed. The new Chandra data weighs in on that, giving a definitive “no” for an answer.
Come see the incredible suite of images and learn about the science inside this cosmic beauty, on today’s Mostly Mute Monday!
So… what’s the story behind the profile pic?
Every year, I put together an extravagant new look for Halloween, and wear the look out occasionally whenever I feel it. If you see me at sci-fi conventions, there’s a good chance I’ll be dressed as a past costume/character. I have been doing this every year this century (so far), and you’re seeing my most recent one.
This past year (Halloween 2017), I went as Queen Elsa from Frozen. That’s the story!
Ask Ethan: How Large Is The Entire, Unobservable Universe?
“We know the size of the Observable Universe since we know the age of the Universe (at least since the phase change) and we know that light radiates. […] My question is, I guess, why doesn’t the math involved in making the CMB and other predictions, in effect, tell us the size of the Universe? We know how hot it was and how cool it is now. Does scale not affect these calculations?”
Our Universe today, to the best of our knowledge, has endured for 13.8 billion years since the Big Bang. But we can see farther than 13.8 billion light years, all because the Universe is expanding. Based the matter and energy present within it, we can determine that the observable Universe is 46.1 billion light years in radius from our perspective, a phenomenal accomplishment of modern science. But what about the unobservable part? What about the parts of the Universe that go beyond where we can see? Can we say anything sensible about how large that is?
We can, but only if we make certain assumptions. Come find out what we know (and think) past the limits of what we can see on this week’s Ask Ethan!
A Cosmic First: Ultra-High Energy Neutrinos Found, From Blazing Galaxies Across The Universe
“A new scientific field, that of high-energy neutrino astronomy, officially launches with this discovery. Neutrinos are no longer a by-product of other interactions, nor a cosmic curiosity that barely extends beyond our Solar System. Instead, we can use them as a fundamental probe of the Universe and of the basic laws of physics itself. One of the major goals in building IceCube was to identify the sources of high-energy cosmic neutrinos. With the identification of the blazar TXS 0506+056 as the source for both these neutrinos and of gamma rays, that’s one cosmic dream that’s at last been achieved.”
From all over the Universe, cosmic particles zip around, occasionally colliding with Earth. These high-energy cosmic rays collide with our atmosphere, and we see the results in a cascading shower of particles. At the same time, we’ve detected ultra-high-energy neutrinos at observatories like IceCube, which originate not in our atmosphere, but from the distant astrophysical source where they were produced. At long last, we’ve matched up these two signals and found a location for them: an ultra-distant blazar some 4 billion light years away. From our perspective, with a quasar jet pointed right at us, it’s one of the brightest objects in the Universe. And now, for the first time, we know at least one place where these particles originate.
It’s an incredible cosmic first, and you won’t want to miss all the details on how we found these high-energy neutrinos and what it means for our Universe!
Hey where can I start learning about astrophysics? Do I start with astronomy and physics separately and start combining? I don't know I'm kinda lost : (!
Well, it depends on what you mean. If you mean you want to start studying astrophysics, I would recommend starting with learning physics and then learning about the environment of space and the objects in it, so that you can apply physics to what’s in space. The “how” of how it all works is astrophysics.
If you just want to learn about it as a layperson, know that’s what you’re getting into: how everything in space works, according to the laws of physics. What are the phenomena that exist, and the physical processes that cause/drive them?
My blog, Starts With A Bang, is a great place to start, and a book I wrote as an intro to cosmology/astrophysics, Beyond The Galaxy, is a great next step. Other people will give you other recommendations but that is where I would start.
What Was It Like When The Universe Was At Its Hottest?
“At the inception of the hot Big Bang, the Universe reaches its hottest, densest state, and is filled with matter, antimatter, and radiation. The imperfections in the Universe — nearly perfectly uniform but with inhomogeneities of 1-part-in-30,000 — tell us how hot it could have gotten, and also provide the seeds from which the large-scale structure of the Universe will grow. Immediately, the Universe begins expanding and cooling, becoming less hot and less dense, and making it more difficult to create anything requiring a large or energy: E = mc2 means that creating a massive particle requires at least enough energy.
Over time, the expanding and cooling Universe will drive an enormous number of changes. But for one brief moment, everything was symmetric, and as energetic as possible. Somehow, over time, these initial conditions created the entire Universe.”
As soon as the Universe was filled with matter, antimatter, and radiation in the hot, dense state known as the Big Bang, it begins to expand and cool. For one brief moment, the Universe reached its maximum temperature and density, and had enough energy to spontaneously create anything at all that Einstein’s energy-mass equivalence would allow. But this state not only wouldn’t last, but it also was never arbitrarily or infinitely hot! There’s a limit to how energetic the Universe could have ever been, and we’ve determined it’s at least 1000 times smaller than the Planck scale. This is still trillions of times more energetic than anything the LHC ever created.
What was it like when the Universe was the hottest its ever been? Come find out on What-Was-It-Like-Whensday! (See what I did there?)
How A Failed Nuclear Experiment Accidentally Gave Birth To Neutrino Astronomy
“The scientific importance of this result cannot be overstated. It marked the birth of neutrino astronomy, just as the first direct detection of gravitational waves from merging black holes marked the birth of gravitational wave astronomy. It was the birth of multi-messenger astronomy, marking the first time that the same object had been observed in both electromagnetic radiation (light) and via another method (neutrinos).
It showed us the potential of using large, underground tanks to detect cosmic events. And it causes us to hope that, someday, we might make the ultimate observation: an event where light, neutrinos, and gravitational waves all come together to teach us all about the workings of the objects in our Universe.”
When you build an experiment to look for an effect you’ve never seen before, it’s an extremely risky endeavor. If what you’re expecting to find is actually there, the payoff is tremendous: like the LHC finding the Higgs. If there’s nothing to find, like the direct detection searches for WIMP dark matter, the null result can be viewed as a colossal (and expensive) failure. One such failure was the construction of an enormous, 3,000+ ton detector facility to look for proton decays. The proton, as you may have heard, is stable, so in that regard, the experiments looking for decays were wildly unsuccessful. But that same setup is extremely sensitive to neutrinos, and in 1987, we used a nucleon decay experiment to successfully find the first neutrinos from beyond the Milky Way!
Come get the story of KamiokaNDE, and learn how it went from being an unsuccessful nucleon decay experiment to the birth of multi-messenger astronomy!