SGU Episode 789
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|SGU Episode 789|
|August 22nd 2020|
|SGU 788||SGU 790|
|S: Steven Novella|
|B: Bob Novella|
|C: Cara Santa Maria|
|J: Jay Novella|
|E: Evan Bernstein|
|Quote of the Week|
|But too often, “common sense” is the safe harbor of ignorance and an excuse for intellectual laziness. They don’t need facts because they already know the truth—their common sense has spared them the effort of investigation or thought.|
|Randy Wayne White, American writer|
Voiceover: You're listening to the Skeptics' Guide to the Universe, your escape to reality.
COVID-19 Update ()
(laughs) (laughter) (applause) [inaudible]
Oleandra Snake Oil ()
Moon Capsules ()
Vision Debate ()
Black Dwarf Supernova (44:25)
- ScienceDaily: 'Black dwarf supernova': Physicist calculates when the last supernova ever will happen
S: Bob, what is a black dwarf supernova?
B: The end of the universe just got a little bit more interesting, perhaps, with this new research suggesting that white dwarf stars could end their lives at the extreme end of the universe, with what’s being called a black dwarf supernova. If you’ve read about and kind of think you have a good idea of what white dwarf stars are, that term, "black dwarf supernova," should be very surprising, a little shocking. This research was recently published in the monthly notices of the Royal Astronomical Society. Yeah, this is pretty dramatic. White [dwarf] stars simply don’t have the mass to create the conditions required to go supernova. It’s just not there. So how could it happen? What kind of scenario is needed to actually make that happen? So to answer that, though, we’re going to have to go over what a normal supernova is.
This is the classic supernova I’m talking about: type-2 supernova, or, more descriptively, a core-collapse supernova. This happens in stars that are big—8 to 50 solar masses—really big. Supermassive stars like this—and all stars, of course—go through the periodic table, fusing successive elements to create this outflowing energy that they need to fight against the relentless inward pull of gravity. It’s a struggle to maintain its equilibrium, and it’s something that the star does its entire life. So things go swimmingly for hundreds of millions of years, and then, of course, iron is formed, and this is an absolutely critical milestone. With iron, there’s no net energy gain in this scenario from fusing iron and nickel, it turns out. So it just sits there in the core like a lump, not fusing anything. This inner core does compress as much as it can, but those electrons eventually refuse to be driven closer due to degeneracy pressure, which is such a fascinating concept. I love the different, various flavors of degeneracy pressure; look into if you’re interested. So what happens is that once enough iron is created, though, it keeps building up, and eventually you pass what’s called a Chandrasekhar limit of 1.44 solar masses, and the degeneracy pressure says, "Screw this!" and it collapses. Bam! The iron-nickel core collapses very, very fast. When that collapses, the outer core is like Wile E. Coyote going off the cliff. It’s like, "Whoa, whoa, whoa!" For, like, two seconds, he’s, like, "What’s going on?" Then the outer core collapses to the inner core. Now, the inner core collapses, but then it runs up against another degeneracy pressure—neutron degeneracy—and it stops, right there. So the outer core bounces off of that, traveling at, I think, a quarter of the speed of light, and that bounce creates the outward push that just blows about the rest of the star, and you’re left with just the core. And you see the conventional supernova that we see in our telescopes, and movies, and in our imaginations. So that’s a supernova in a big star.
Smaller stars—less than that, say 0.5 solar masses and above to maybe close to 8—they never get to iron. They just don’t ever make it. They stop after making elements like carbon and oxygen, primarily. There may be a little bit of neon and magnesium, and when it’s all said and done, you’re left with something as big as the Earth with a mass of around the Sun: a white dwarf. Basically, there was never enough mass to overcome that electron degeneracy pressure, right? Just wasn’t enough there. So the electrons held—it just never collapsed. But you basically have a core that’s got carbon and oxygen, and conventional wisdom has been saying for many, many years that fusion stops and it just cools down over trillions of years. And eventually, theoretically, after 1020 years, it chills so thoroughly that it becomes a black dwarf star. And, from there—depending on what sources you look at—from there, a black dwarf star can exist essentially indefinitely. Nothing’s going to happen to it, unless, of course, there’s proton decay, and that’s not good. But, if there is no proton decay, then, yeah, "indefinitely" is a word I’ve seen in a lot of research. It could last a very, very long time, which is putting it mildly.
So here’s the new bit. The new bit goes against this idea that fusion has stopped for these dwarf stars. Theoretical physicist Matt Kaplan, assistant professor of physics at Illinois State University, says that there is fusion happening, even if there’s no intense heat or pressure that you would think would be required for that to happen. So it accomplishes this, he says, by using quantum tunneling and just a really, really, really times a trillion long time. Really long time.
C: (laughs) Really.
B: So quantum tunneling is fascinating. It describes subatomic particle passing through what would seem like an insurmountable barrier. Like a lame example: you’re gently bouncing a ball against a wall only to find out that it disappears and reappears on the other side. That’s kind of what’s happening at the subatomic scale. If you want to be a little more accurate and technical, it has to do with a tiny piece of the wave function extending beyond the barrier, meaning that there’s a very, very small, but finite probability that it will appear in that area. But this is real. This tunneling is real and you wouldn’t have your computers or the sun would barely shine without it. Did you know that tunneling is a critical component for making stars shine? When hydrogen atoms—the classic image of, say, proton-proton fusion is that the hydrogens atoms smash together with such force that they fuse, and you end up with a helium atom and some extra energy, and that’s star shine right there. That’s why stars shine. And that’s pretty obviously, amazingly simplistic. But what’s really happening is that these hydrogen atoms are, for the most part, getting close enough—they’re getting very close, but not close enough to fuse—and what happens is they’re actually tunneling that last little bit of the way. They’re tunneling and fusing because of the tunneling. So I’m not saying that fusion wouldn’t happen without tunneling, but it would be tiny. It would be a tiny effect. I’m not sure what the universe would look like, but it would be pretty boring and not very well lit.
So tunneling is critical, even just for regular fusion. So the fact that this guy is saying that tunneling is happening with these white dwarf stars in the deep future hopefully will make a little bit more sense. So this is what they believe will happen: As the star cools into a black dwarf, heavier elements like oxygen, neon, and magnesium will migrate to the core, where they will get close enough for tunneling to happen more frequently. Tunneling happens more frequently when things are close together. If they’re far apart, it could still happen. You could theoretically have one particle tunnel a mile, but the odds of that happening—you would probably need a universe quintillion to the quintillionth power long in order for that to happen, but it theoretically could happen. It’s just much less likely.
So you’ve got these elements coming closer into the core of the black dwarf. He says that, over time, they will fuse into iron. And, then, once you have iron, then what I just described for the core collapse is supposed to happen. It builds up the iron over many, many, many, many eons. It builds up the iron and eventually it could get over the Chandrasekhar limit, and then it could collapse and then cause a supernova at the end of the universe, essentially. And, remember, when I say "over time," I mean over time. I’m going to put some numbers to it. The biggest black dwarf stars, they’re going to supernova first, right? Because they’re the biggest, they’re going to create enough iron in order to go supernova. And it’s going to take 101100 years. And I have four exclamation points in my notes.
C & E: (laugh)
B: 101100 years!!!! How many years is that? I actually found the number! That’s one hundred—
E: What! There’s no—
B: —Oh, yeah! I found it! That’s one hundred trecenquinsexagintillion years.
B: Oh boy! Yeah.
S: Oh that’s [inaudible].
E: Wait a minute…
B: Yes. It’s even got "sex" in the name, which makes it even better.
B: Yes! So…but guys—
E: Whatever happened to "bajillion" or "kazillion"?
C: That’s a sexy number.
B: Yes. That number ends with sexagintillion, and I love it. So that’s just 10 to—that’s just the biggest black dwarves, guys. What about the small guys? These are small—
E: Yeah. What about them?
B: These are white dwarves that may exist now that are, unfortunately, not like the Sun. The Sun’s just doesn’t have quite enough mass for this to happen, it seems. But stars that are slightly bigger than the Sun could eventually go. And they will be—they could be, if this theory holds out—this could be the last fireworks of the universe. Their numbers put it at—get this one!— 1032,000 years. 1032,000 years! I never thought I’d find a number for that, but I found it. I found a number to describe 1032,000. I had to do a little addition here, but it comes—this number is: 10 sextillion tremilliatrecenduotrigintillion years. [note 1]
C: (laughs) What?!
B: That’s the number. That’s how many years we’re talking about. I just love that these numbers have been thought about and are actually written down somewhere. So, yeah, a lot of years. Now, remember, that assumes that proton decay does not occur because I think, if proton decay kicks in, then that’s like 1040 years. So none of this will happen. It’s still a long time. It’s cool to think that these things could exist that deep into the future, but that’s so far into the future, guys. Even I have never heard of numbers this deep into the heat death of the universe. I mean, black holes will gone. Black holes won’t last much more than 10100 years. What’s 10100 compared to 101100 or 1032,000? It’s nothing! Entropy is essentially at maximum. It’s just so deep into the future. There’s going to be nothing. Nothing—besides these black hole supernovas, I guess—not much else will exist besides maybe electrons or some low-grade heat, where you can’t do any work. It’s going to be fun. But it’s just kind of nice to know that deep in the future, where there may be these little explosions of coolness that happen right before the very bitter, bitter end.
S: Cool. Yeah. That’s a long time.
B: Yeah, this is a fun one.
S: So almost as long as this news segment?
S: All right.
B: Yeah. You will cut it shreds, I’m sure.
S: Let’s go on.
B: I already cut it, you know? I already cut it down for you.
S: I don’t doubt it.
E: (laughs) He edited for you, Steve.
B: I pre-cut out. I was going to go off on electron degeneracy pressure. But I said, "Nope. Steve definitely cut that out, so I won’t put it in."
Pentagon UFO Task Force (55:27)
Who's That Noisy? ()
- Answer to last week’s Noisy: Ringing rocks
New Noisy ()
Name That Logical Fallacy ()
Science or Fiction ()
|Science||2.8x as energy dense|
|Science||70m tonnes annually|
|Bob||2.8x as energy dense|
|Cara||2.8x as energy dense|
|Evan||2.8x as energy dense|
Voiceover: It's time for Science or Fiction.
Theme: Hydrogen Fuel
Item #1: The majority of hydrogen is produced by electrolysis from water and is as clean as the source of electricity used in this process.
Item #2: The global production of hydrogen is more than 70 million metric tons annually, which could theoretically produce 2.3 billion MWh of electricity. (US energy production is 4.1 billion MWh annually.)
Item #3: Hydrogen is about 2.8 times as energy dense as gasoline by weight.
Steve Explains Item #2
Steve Explains Item #1
Steve Explains Item #3
Skeptical Quote of the Week ()
But too often, “common sense” is the safe harbor of ignorance and an excuse for intellectual laziness. They don’t need facts because they already know the truth—their common sense has spared them the effort of investigation or thought.
– from Chapter 4 of "Captiva", by Randy Wayne White, American writer
S: —and until next week, this is your Skeptics' Guide to the Universe.
S: Skeptics' Guide to the Universe is produced by SGU Productions, dedicated to promoting science and critical thinking. For more information, visit us at theskepticsguide.org. Send your questions to email@example.com. And, if you would like to support the show and all the work that we do, go to patreon.com/SkepticsGuide and consider becoming a patron and becoming part of the SGU community. Our listeners and supporters are what make SGU possible.
Today I Learned
- Fact/Description, possibly with an article reference
- Bob surely used the "Name of a Number" generator from the "How High Can You Count" webpage, at least for 101100, but the generator (and the rules it follows, described in both the aforementioned page and the "Large Numbers" webpage) gives a different name for 1032,000: one hundred decmilliasescenquinsexagintillion. He mentions "doing some addition," so it's possible he tried to mash up some of the rules, albeit mistakenly. Ten sextillion is for 1022. Tremilliatrecenduotrigintillion is for 1010,000
- Science-Based Medicine: Oleandra – The New COVID Snake Oil
- Ars Technica: Could a Dragon spacecraft fly humans to the Moon? It’s complicated
- Nautilus: This Vision Experiment Resolved a Centuries-Old Philosophical Debate
- ScienceDaily: 'Black dwarf supernova': Physicist calculates when the last supernova ever will happen
- Large Numbers
- How High Can You Count? The English Name of a Number
- Chalkdust: Names for large numbers
- Space.com: What does the Pentagon's new UFO task force mean? Experts weigh in.
- [url_from_SoF_show_notes publication: title]
- US DOE Office of Energy Efficiency & Renewable Energy: 10 Things You Might Not Know About Hydrogen and Fuel Cells
- US DOE Alternative Fuels Data Center: Hydrogen Basics
- [url_for_TIL publication: title]