Starts With A Bang

Comments of the Week #91: From Santa science to lonely galaxies

Image credit: ESO and Digitized Sky Survey 2. Acknowledgment: Davide De Martin.

“This whole Santa Claus thing just doesn’t make sense. Why all the secrecy? Why all the mystery?
If the guy exists why doesn’t he ever show himself and prove it?
And if he doesn’t exist what’s the meaning of all this?” -Calvin, via Bill Watterson

This is our last comments of the week for 2015, and Starts With A Bang can’t wait for the new year! All the great things we’ve worked so hard for this year promise to bring about an even better one in 2016. But that said, there’s still more science for this year! This past week saw the following:

We’re up to 125 donors in our Patreon campaign, my book is so close to being ship-able from Amazon, and in just a week I’ll be headed to Florida for the 227th AAS meeting! With all that behind us, let’s dive into your comments of the week!

Image credit: NASA/Goddard/Wade Sisler, of Brian Greene presenting on String Theory.

From Omega Centauri on the energy of the Universe: “Do we have a measure of the energy represented by the spacetime itself?”

That’s a very difficult question, because energy is not strictly defined for spacetime in General Relativity. We have ways of attempting to make sense of it, since all the different components of the Universe have well defined energies. This includes particles like photons, normal and dark matter, as well as neutrinos, but it also includes things like dark energy and spatial curvature, which are inherent to space itself, as well as field energy. But the problem is not everybody (i.e., all observers) agrees on what they would see.

In some static spacetimes, you can get energy conservation for the overall systems (if you sum all the particle), but in spacetimes like our own — an FLRW Universe — there’s no Killing vector, and hence no conservation law, that corresponds to energy. So that’s a long way of saying, “kind of, but not really.”

Image credit: Arp 230; Credit: ESA/Hubble & NASA; Acknowledgement: Flickr user Det58.

From Alan Doak on the same topic: “If I understand Ethan correctly, then if everything in the universe magically stopped emitting [photons] somehow, then the expansion of the universe would slow down?”

I do see where this question is coming from, even though the answer to the technical thing you asked is not what you’re looking for. What would keep the expansion of the Universe from slowing down is if you both stopped photons (and relativistic matter, too) from losing energy as the Universe expanded, and also increased the number of photons and matter particles so that the density remained constant as the Universe expanded.

Image credit: E. Siegel, from his new book, Beyond The Galaxy.

There was a theory, once, that proposed something very, very close to that: the Steady-State Theory of the Universe. If that were true, the Hubble constant would be a true “constant” rather than a parameter that decreases over time. Interestingly enough, when dark energy takes over so thoroughly — some 100 billion years from now — that’s the Universe we’ll be left with: one where the Hubble constant doesn’t appear to change at all over time. But to answer your original question, when you create photons from matter/massive particles, they lose energy faster than the matter/massive particles do, and so they cause the Universe’s expansion rate to drop a little more quickly. (All radiation, combined, is on the order of ~10^(-5) the current expansion rate.) So if you could stop the creation of new photons, you could — by a tiny, tiny amount — keep the expansion rate dropping at a slightly slower rate than it actually does.

Screenshot from my latest post on Forbes, as of Christmas Day. Who clicks on those? But they sure do slow down the experience…

From Michael Kelsey on the ‘hard problem’ of the internet: “I realize that I am being a perpetrator of the “tragedy of the commons.” The revenue from advertising is what provides sites like Forbes with the incentive (and ultimately, the ability) to make content available at all. By blocking those ads, I’m marginally reducing the “eyeball count” for them, and hence reducing the revenue gained from them.”

Again, this is the hard problem of the internet. How do sites make money from readers who don’t want to pay for the content they produce? How do writers and content-producers make money farther down the totem pole? And how do users still get a good experience? I’ve had my primary internet presence housed at four different sites:

Image screenshotted from Forbes.

I would like this “writing-and-communicating-about-the-Universe” thing that I do to be a full-time job for me; where it’s the thing I do. Honestly, people often look to me for advice on how to do it successfully, and I still need a day job. Setting up a Patreon has helped a little, but in many ways, this is a problem without a known solution. I’m hoping that Universities and Colleges discover my book and use it for their students, and that will help some. But really, I don’t know the accounting of all of it, and I don’t know how to fix it. For me, I’ve just whitelisted Forbes in my adblocker; the “ad-light” experience that comes with it doesn’t crash my browser like the regular “turn-off-adblock” experience does, and I guess that’s good enough for me.

But if Forbes isn’t viable for you, posts are still ad-free and on a 1-week delay on Medium.

Image credit: Wikimedia Commons user Glogger, of the Santa Claus parade in Toronto, 2007.

From dean on the physics of Santa Claus: ““There’s someone downstairs.”
“Why do you think that?”
“I can hear the TV.”
I listen. Sure as crap the television is on, and I know it was off when I finished setting up and came upstairs.
I got up and went down to check: nothing was out of place, so I turned off the rogue television, tidied up the counter, and went back upstairs.
“What channel was the TV on Dad?”
“The Weather Channel” (I had to say something).
“Oh. Santa probably wanted to check for storms huh?”
Back to bed everyone went.”

A friend of mine asked me if I’d dress as (kilted) Santa and do an event for him last week, which I did. I had a little boy ask me if I was the real Santa, and I told him, “no, not yet. The real Santa’s my uncle, but maybe someday, when I get older and my beard turns white, I’ll get to be Santa.” He had a lot of questions about the real Santa, who was obviously still at the North Pole getting ready for Christmas Eve. It was a good decision.

From the Peak Oil Poet, Wow, and occasionally others….

Screenshot from, and this is just an example.

So… you’ve now exchanged over 100 comments total yelling at each other, fighting with each other, and trying to hurt one another deliberately. I’ve always been a fan of making peace, and I have no idea how to do that on the internet. So…

I’ll just ask. Can we try to state our opinions on science, politics, humanity, economics, math, whatever, without stating our opinions on which other commenters put which animate and inanimate objects where? Can it be my Christmas and New Year’s presents combined? Because you know what I don’t like to do? Ban commenters and/or moderate comments. It’s bad enough that I have to deal with anti-semitic slurs and threats from Forbes commenters (those need moderating); you’ve all been around long enough that you know how not to make this harder for me.

Image credit: E. Siegel, from his new book, Beyond The Galaxy.

From Naked Bunny With A Whip on new particles: “Why is it so hard to find a new particle? It’s probably been misfiled or lost between the couch cushions. Science is messy sometimes.”

There is an argument that we found one, once. A magnetic monopole, on February 14th (Valentine’s Day), 1982. From Blas Cabrera’s paper, it sure looked like one.

Image credit: Cabrera B. (1982). First Results from a Superconductive Detector for Moving Magnetic Monopoles, Physical Review Letters, 48 (20) 1378–1381.

We’ve never seen another, and it’s now assumed that this was a crazy fluke, a prank, or — worst of all — the only magnetic monopole in the entire Universe. And unless it was a prank and the prankster comes forward, or unless we actually find a second monopole, we’ll probably never know.

Image credit: Wikimedia Commons user Lunch, of a 2-D projection of a Calabi-Yau manifold, one popular method of compactifying the extra, unwanted dimensions of String Theory.

From Kevin on string theory as science (or not): ““The third prediction [the existence of supersymmetric particles] has come up empty, but we would need to achieve energies that are ~10^15 times higher than what the LHC can produce to rule out string theory entirely and falsify it.”
This third prediction is, therefore, a falsifiable prediction. Our inability to perform the test, to *do* the science, does not mean it is not a science.”

This, to be fair, is true. I feel like I overstated my case in the original title of the piece on Forbes. (Since amended.) The point I was trying to make was that String Theory is not a scientific theory; it is a mathematical theory and hasn’t reached the level of “scientific theory” that we require of other theories like evolution, gravity or QFT.

Image credit: ESO/L. Calçada.

As far as whether it’s science, I think it is in a lot of ways. I think it’s a scientific hypothesis and a scientific framework, and I think it has the potential to someday become a scientific theory. We can falsify certain models or realizations of it (as “unphysical”, as they don’t agree with the physics of the Universe), but I don’t think we can ever rule out all models. Even that generic one I made — about the existence of SUSY particles at all energies — I am sure will have exceptions, as a model will be made where the SUSY particles are “hidden” for some reason. Falsifiability just isn’t there yet, and String Theory’s prospects for being falsifiable, in principle, are unclear. It’s interesting, it’s a scientific pursuit, but it’s not a scientific theory.

Image credit: NASA / Apollo 17.

And finally, from PJ on the orange Apollo soil: “Hmm, common origin, or, common interchange?
Anyway, it’s xmas day here, so, happy & safe hols.”

The assumption is common origin, due to a great many similarities between the two bodies, and a consistent history that common interchange doesn’t provide. (How to ascribe the common atomic content of the Earth and Moon otherwise?)
And may you all have a happy and safe holiday season, and celebrate however you see fit. May your holidays be filled with kindness, wellness, and happiness. And for those of you (like me) in the western half of the Americas, may you stay warm this holiday season, too!