Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions #4

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Listener Questions #4 · Daniel and Kelly’s Extraordinary Universe

• 0:06
  Speaker 1: How do some bees make meat honey? What are tapeworms
• 0:09
  Speaker 1: up to in my tummy?
• 0:11
  Speaker 2: Can light escape from a black hole? What process produces coal?
• 0:15
  Speaker 1: Did Franklin hang that key from a kite? Why is
• 0:18
  Speaker 1: dark chocolate better than white?
• 0:20
  Speaker 2: How do moles smell underwater? Why is the planet getting hotter?
• 0:24
  Speaker 1: How can humans live on Mars? What's the hold up
• 0:27
  Speaker 1: with flying cars?
• 0:28
  Speaker 2: The current state of space law? The powerful mantis, shrimp claw?
• 0:32
  Speaker 1: Biology, physics, archaeology, forestry, really anything other than chemistry?
• 0:38
  Speaker 2: What diseases do you get from your cat? Well, we'll
• 0:41
  Speaker 2: find the answers to all of that.
• 0:43
  Speaker 1: Whatever question keeps you up at night.
• 0:45
  Speaker 2: Daniel and Kelly's answer will make it right.
• 0:48
  Speaker 1: Welcome to another Listener Questions episode on Daniel and Kelly's
• 0:52
  Speaker 1: Extraordinary Universe.
• 1:07
  Speaker 3: Hi.
• 1:07
  Speaker 2: I'm Daniel, I'm a particle physicist, and I've never read
• 1:10
  Speaker 2: a poem on the podcast before.
• 1:12
  Speaker 4: Hi.
• 1:13
  Speaker 1: I'm Kelly Wiener Smith. And my husband just assumed that
• 1:16
  Speaker 1: I'd be so bad at writing poems that when I
• 1:17
  Speaker 1: read it out loud to my daughter, he left the
• 1:19
  Speaker 1: room just so that he wouldn't be embarrassed. But you
• 1:22
  Speaker 1: know what, I had fun.
• 1:25
  Speaker 2: I hope he's blushing somewhere. Whenever he's listening to this, he.
• 1:28
  Speaker 1: Might skip all of our Listener Questions episodes from here
• 1:31
  Speaker 1: on out. But that's all right. I had a good time.
• 1:33
  Speaker 2: Well that's too bad, because those are my favorite episodes.
• 1:36
  Speaker 2: I love hearing what people are wondering about, helping them
• 1:39
  Speaker 2: unravel their confusion and getting to the topics that are
• 1:43
  Speaker 2: really in people's minds. It's my favorite way to interact
• 1:46
  Speaker 2: with our audience.
• 1:47
  Speaker 1: I love it as well, and I'm particularly excited about
• 1:50
  Speaker 1: this Listener Questions episode. You know, one because my daughter's
• 1:54
  Speaker 1: questions included and that's pretty cute. But two because we
• 1:57
  Speaker 1: got a biology question for me that I was she
• 2:00
  Speaker 1: is completely unaware of this group of species and they're
• 2:03
  Speaker 1: so creepy and right up my alley and it was
• 2:05
  Speaker 1: so much fun.
• 2:06
  Speaker 2: All right, Well, let's not waste any more time. Let's
• 2:08
  Speaker 2: dig into it today. We have questions about seasons on
• 2:11
  Speaker 2: Binary Star systems, about meat, wasp honey, and about how
• 2:16
  Speaker 2: gravity actually works.
• 2:19
  Speaker 1: Let's do it.
• 2:19
  Speaker 2: So our first question is from Aida. She's ten years
• 2:22
  Speaker 2: old and she lives in Virginia, and I think she
• 2:25
  Speaker 2: knows Kelly pretty well.
• 2:26
  Speaker 1: Great place to live, I'll just throw that in there.
• 2:30
  Speaker 2: Here's Ada's question.
• 2:32
  Speaker 5: Hi. I'm Ada, I'm ten years old. I have a
• 2:35
  Speaker 5: question for you. What would seasons be like if you
• 2:39
  Speaker 5: were on a planet in a solar system that had
• 2:41
  Speaker 5: two sons? Thank you?
• 2:43
  Speaker 2: All right? I like how she gets right to the point.
• 2:46
  Speaker 1: Yes, she's very succinct. I like that too.
• 2:48
  Speaker 2: Is she reading a book about life on a solar
• 2:51
  Speaker 2: system with two sons? Or where do you think this
• 2:53
  Speaker 2: question came from?
• 2:54
  Speaker 1: Gosh, you know, I'm sure it didn't come out of nowhere,
• 2:57
  Speaker 1: but I don't know where she heard about solarsis with
• 3:00
  Speaker 1: two suns. That sparkedness. Could have been science class at school.
• 3:03
  Speaker 2: Maybe she's writing a science fiction novel and she needs
• 3:06
  Speaker 2: some science consultation.
• 3:08
  Speaker 1: That's right, Yes, and she reached out to the right person.
• 3:10
  Speaker 2: Yeh, she certainly did. So let's dig into it first.
• 3:15
  Speaker 2: Let's remind ourselves why we have seasons on Earth, and
• 3:18
  Speaker 2: then we can teleport ourselves mentally to a solar system
• 3:21
  Speaker 2: with two stars and think about that one. So, on Earth,
• 3:24
  Speaker 2: the reason we have seasons is because the Earth is
• 3:26
  Speaker 2: tilted right. The Earth goes around the Sun, and there's
• 3:29
  Speaker 2: a plane there where all the planets go around the
• 3:32
  Speaker 2: Sun in the same plane, and the Earth also spins,
• 3:36
  Speaker 2: but the axis that it spins on is not perfectly
• 3:39
  Speaker 2: perpendicular to the plane of its orbit, so it's tilted
• 3:43
  Speaker 2: a little bit. It like leans over. Now, the Earth
• 3:45
  Speaker 2: is a sphere, so you know what is really leaning.
• 3:48
  Speaker 2: It's still a sphere when it's tilted. But what's leaning
• 3:50
  Speaker 2: is that axis of spin, that axis that controls the
• 3:53
  Speaker 2: day night cycle. So what's closer to the Sun is
• 3:56
  Speaker 2: the Northern hemisphere the spin lets you define a northern
• 3:59
  Speaker 2: and the southern hemisphere, Then the Northern hemisphere is closer
• 4:02
  Speaker 2: to the Sun during the summer, and the Southern hemisphere
• 4:05
  Speaker 2: is further from the Sun during the Northern hemisphere summer
• 4:08
  Speaker 2: and the Southern hemisphere's winter. It's not actually accurate to
• 4:11
  Speaker 2: say that the Northern hemisphere is any closer to the Sun.
• 4:14
  Speaker 2: Is just more exposed to the Sun because it's leaning
• 4:17
  Speaker 2: that direction, got it?
• 4:18
  Speaker 1: And you know, I've got to admit that every once
• 4:20
  Speaker 1: in a while, when I talk to like the few
• 4:21
  Speaker 1: friends I have in Australia, I still forget that they're
• 4:24
  Speaker 1: experiencing the opposite season that we are up here in
• 4:27
  Speaker 1: North America. And we regularly have a disconnect.
• 4:31
  Speaker 2: Yeah, exactly. And so if we didn't have a tilt.
• 4:34
  Speaker 2: For example, if the Earth's axis of rotation was perfectly
• 4:38
  Speaker 2: perpendicular to the plane of its orbit, then you wouldn't
• 4:41
  Speaker 2: have any seasons. You just always have I guess spring
• 4:44
  Speaker 2: or fall. Right, the days would be the same length
• 4:47
  Speaker 2: all year round. Going around the Sun wouldn't change your
• 4:50
  Speaker 2: experience at all.
• 4:51
  Speaker 1: No seasons, totally boring, just like living in California. You
• 4:55
  Speaker 1: knew where that was going halfway through the sentence.
• 5:00
  Speaker 2: Exactly, we'd all be happy all year long, right, it'd
• 5:03
  Speaker 2: be amazing, so dull. And there are other tiny factors
• 5:08
  Speaker 2: that also affect the weather and the seasons, things like
• 5:11
  Speaker 2: the elliptical orbit, or the Earth doesn't orbit in a
• 5:14
  Speaker 2: perfect circle around the Sun. It's an ellipse, which means
• 5:17
  Speaker 2: sometimes it is closer to the Sun and sometimes it's
• 5:20
  Speaker 2: further from the Sun. But this is a smaller factor
• 5:23
  Speaker 2: than the tilt, which really dramatically changes how many hours
• 5:26
  Speaker 2: of sunlight you get every day. The Earth is closest
• 5:29
  Speaker 2: to the Sun in January and furthest from the Sun
• 5:32
  Speaker 2: in July, so actually that counters the effect. It makes
• 5:35
  Speaker 2: the summer slightly less severe and the winter's slightly less severe.
• 5:39
  Speaker 1: Is that why the year starts in January? Or did
• 5:43
  Speaker 1: that have nothing to do with the calend No.
• 5:45
  Speaker 2: That's totally random. Yeah, Oka's totally right. And also the
• 5:50
  Speaker 2: Earth tilt processes a little bit. It's not always in
• 5:53
  Speaker 2: the same direction. It itself rotates a little bit, like
• 5:56
  Speaker 2: a wobbly top. These are small factors, and that's affected
• 5:59
  Speaker 2: by like the Jupiter and all sorts of other stuff.
• 6:02
  Speaker 2: So mostly the Earth has seasons because it's tilted, So
• 6:05
  Speaker 2: the northern hemisphere is getting more light and the southern
• 6:07
  Speaker 2: hemisphere is getting less light during the northern hemisphere summer.
• 6:10
  Speaker 2: All right, but that's a simple system, single planet going
• 6:13
  Speaker 2: around a single star. So what about a binary star
• 6:16
  Speaker 2: system in Ada's mind?
• 6:18
  Speaker 1: Can I back you up for a second? Are most
• 6:20
  Speaker 1: planets tilted so like the Moon has a very little
• 6:22
  Speaker 1: bit of a tilt. Is Earth weird having a twenty
• 6:25
  Speaker 1: three point four degree tilt?
• 6:27
  Speaker 2: It's not weird to have a tilt like Urinus is
• 6:29
  Speaker 2: tilted much more dramatically ninety seven degrees, basically totally on
• 6:33
  Speaker 2: its side. Other planets are tilted more or less. The
• 6:36
  Speaker 2: tilt we think comes from being hit. Like everything in
• 6:40
  Speaker 2: the Solar System formed together from a big swirl. That's
• 6:43
  Speaker 2: why everything is rotating in the same plane, and most
• 6:46
  Speaker 2: of the planets are spinning in the same direction they
• 6:48
  Speaker 2: move around the Sun, which is the same direction that
• 6:51
  Speaker 2: the Sun is spinning itself. The whole Solar system is
• 6:54
  Speaker 2: one big swirl, which then coalesces into a star and
• 6:57
  Speaker 2: planets which all have the same swirl. But then you
• 7:00
  Speaker 2: can get hit by something from outside the Solar system
• 7:02
  Speaker 2: and it can knock you off axis a little bit.
• 7:05
  Speaker 2: So we think that's probably the source of the Earth's tilt,
• 7:07
  Speaker 2: and other planets tilt as well.
• 7:09
  Speaker 1: With all the stuff that's colliding, Would it be reasonable
• 7:12
  Speaker 1: to expect that having no tilt would be rare because
• 7:15
  Speaker 1: there's so many collisions that probably knock you off angle.
• 7:17
  Speaker 2: Yeah, As the Solar system forms, it's a little chaotic
• 7:20
  Speaker 2: and things hit each other, so the average tilt is
• 7:22
  Speaker 2: going to be zero, but it's unlikely for everything to
• 7:25
  Speaker 2: have exactly zero tilt. Got it just the same with it,
• 7:28
  Speaker 2: Like all the solar systems in the galaxy on average
• 7:31
  Speaker 2: have zero tilt relative to the plane of the galaxy,
• 7:34
  Speaker 2: but most of them are tilted relative to the plane
• 7:36
  Speaker 2: of the galaxy. They're not all aligned with the actual
• 7:39
  Speaker 2: rotation of the galaxy.
• 7:40
  Speaker 1: All right, So let's move on to systems with two sons.
• 7:43
  Speaker 2: All right. So system with two sons sound exotic, right,
• 7:46
  Speaker 2: You're like, ooh wow, two sons, how cool, But the
• 7:49
  Speaker 2: truth is that they're not actually that rare. Binary star
• 7:52
  Speaker 2: systems are all over the galaxy. It's a significant fraction
• 7:56
  Speaker 2: of the stars in our galaxy have a partner star.
• 8:00
  Speaker 2: And the reason is that that big cloud of gas
• 8:02
  Speaker 2: that collapses to give you a star usually it's part
• 8:04
  Speaker 2: of a much bigger cloud. So stars are born together.
• 8:08
  Speaker 2: Often you have two, three, four, five stars all born together,
• 8:12
  Speaker 2: which begin a complicated swirl as they're forming. So you
• 8:15
  Speaker 2: have these nurseries. We have a lot of star forming
• 8:18
  Speaker 2: happening at the same time, and so stars are born
• 8:21
  Speaker 2: with partners. And the reason we have a lot of
• 8:23
  Speaker 2: binary star systems is that it's basically the most number
• 8:26
  Speaker 2: of stars you can have in a system and have
• 8:28
  Speaker 2: it be stable. Like you can have two things orbiting
• 8:31
  Speaker 2: each other and have that be stable, like the Earth
• 8:33
  Speaker 2: and the Sun or a star and another star. But
• 8:36
  Speaker 2: you add a third object and it becomes chaotic, it
• 8:39
  Speaker 2: becomes really complicated and unstable. So if you have three stars,
• 8:43
  Speaker 2: for example, what's very likely to happen is one of
• 8:46
  Speaker 2: them is going to get ejected and you're going to
• 8:48
  Speaker 2: end up with a single star and then a pair
• 8:50
  Speaker 2: of stars. So you have a lot of binary star
• 8:52
  Speaker 2: systems out there, not very many trinary systems or quaternary systems,
• 8:57
  Speaker 2: or not even know the descriptions for five or more stars.
• 9:01
  Speaker 1: So why is it more likely to get ejected than
• 9:03
  Speaker 1: to get pulled into one of the other two stars
• 9:05
  Speaker 1: and then just make like, I don't know, a big star,
• 9:07
  Speaker 1: a big explosion.
• 9:10
  Speaker 2: Yeah, well that could happen also, but you know, stars
• 9:13
  Speaker 2: are small compared to the distances between them, and so
• 9:16
  Speaker 2: actual collisions are pretty unlikely, but they can spiral in
• 9:20
  Speaker 2: and combine. That certainly does happen as well, But there's
• 9:22
  Speaker 2: just many more outcomes where they get ejected, and just
• 9:25
  Speaker 2: like in our Solar system, there's been chaos. We think
• 9:27
  Speaker 2: probably there was another giant planet which got ejected from
• 9:31
  Speaker 2: the Solar System because of the interaction between all the planets.
• 9:34
  Speaker 2: So you have a lot of binary star systems out there,
• 9:37
  Speaker 2: and then you have to think about the planets around
• 9:39
  Speaker 2: those binary stars, and it becomes tricky already because now
• 9:42
  Speaker 2: the planet is sort of like that third object. So
• 9:45
  Speaker 2: you might wonder like, hey, isn't the planet just going
• 9:47
  Speaker 2: to get ejected the way like a third star would
• 9:49
  Speaker 2: get ejected, And the answer is yes, it's not easy
• 9:52
  Speaker 2: to have planets around binary stars in a stable way.
• 9:56
  Speaker 2: There's two ways to do it, and both of them
• 9:58
  Speaker 2: basically make it look more like a binary star system.
• 10:01
  Speaker 2: So one solution is you have the two stars near
• 10:04
  Speaker 2: each other and the planet is far away, so it's
• 10:07
  Speaker 2: sort of like, yeah, there are three objects there, but
• 10:09
  Speaker 2: really it's sort of a nested set of binary systems.
• 10:12
  Speaker 2: You have like the stars on one side and the
• 10:14
  Speaker 2: planet that are orbiting each other, and then inside the
• 10:17
  Speaker 2: sort of star system, you have two stars moving near
• 10:20
  Speaker 2: each other. That's one situation, basically, like replace the Sun
• 10:23
  Speaker 2: with two stars close to each other or closer to
• 10:26
  Speaker 2: each other than to the planet. The other possible configuration
• 10:29
  Speaker 2: is you have a star and a planet like the
• 10:31
  Speaker 2: Earth and the Sun, and then you have another star
• 10:33
  Speaker 2: that's much further away, so like put a star near
• 10:36
  Speaker 2: Pluto or something much further from the Earth than the
• 10:39
  Speaker 2: Sun and then it's far enough away that it's not unstable.
• 10:43
  Speaker 2: Then you have like again a nested set of binary systems.
• 10:46
  Speaker 2: You have three objects, but really it's like two objects
• 10:50
  Speaker 2: acting as one and then in a binary system with
• 10:53
  Speaker 2: the third object.
• 10:54
  Speaker 1: Okay, so then let's talk about seasons. In the first
• 10:57
  Speaker 1: scen area, where you have two stars that are right
• 10:59
  Speaker 1: next to each other, do they act like one just
• 11:02
  Speaker 1: megastar when you sort of aggregate their effects.
• 11:05
  Speaker 2: Yeah, they act like one megastar. It's going to be
• 11:08
  Speaker 2: very similar to as if you had one bigger star.
• 11:11
  Speaker 2: It's going to be different and more dramatic in terms
• 11:13
  Speaker 2: of like sunrise and sunset. Sunrise will be longer and
• 11:17
  Speaker 2: sunset will be longer, and there'll be times when you
• 11:19
  Speaker 2: have like one star above the horizon and one below,
• 11:22
  Speaker 2: so you could have effects like you could have a
• 11:24
  Speaker 2: sunrise where there's already a star in the sky, and
• 11:27
  Speaker 2: then you have basically two sunsets, one more dramatic than
• 11:30
  Speaker 2: the next. So that would be really cool, but it
• 11:32
  Speaker 2: wouldn't really affect the seasons very much, right because the
• 11:36
  Speaker 2: planet's relationship to the star is basically the same. If
• 11:39
  Speaker 2: you have a tilt and you have an orbit that's
• 11:41
  Speaker 2: going to determine your seasons. So in that situation where
• 11:44
  Speaker 2: you have a planet around a binary star system where
• 11:46
  Speaker 2: the stars are close to each other and further from
• 11:48
  Speaker 2: the planet, the seasons are going to be very much
• 11:50
  Speaker 2: like here on Earth.
• 11:51
  Speaker 1: I feel like it would be amazing to wake up
• 11:53
  Speaker 1: to a sunrise with two stars in the horizon. That
• 11:56
  Speaker 1: sounds really cool. But all right, So then our second scenario,
• 11:59
  Speaker 1: you say, there's one sun that's kind of close to
• 12:01
  Speaker 1: the planet and another sun that's super far out. Is
• 12:05
  Speaker 1: it far enough out that it doesn't really impact climates
• 12:08
  Speaker 1: and seasons anymore?
• 12:11
  Speaker 2: Unfortunately? Yeah, So the boring answer is for there to
• 12:14
  Speaker 2: be a planet in this situation, that star has to
• 12:16
  Speaker 2: be kind of far away. The closer you get it,
• 12:19
  Speaker 2: the more dramatic and the impact on seasons and day
• 12:21
  Speaker 2: night stuff, etc. But also the more unstable it is. Like,
• 12:25
  Speaker 2: if you have the planet be the same distance from
• 12:27
  Speaker 2: both stars, so it's like very dramatic, then that system
• 12:30
  Speaker 2: is totally unstable and it's not gonna last for very long.
• 12:34
  Speaker 2: So you got to push that second star kind of
• 12:36
  Speaker 2: far away, which means really it's gonna be in the
• 12:39
  Speaker 2: sky more like a bright star. Than a real sun
• 12:42
  Speaker 2: and not really gonna affect your seasons. You're gonna have
• 12:45
  Speaker 2: one totally dominant star and then a second star that's
• 12:49
  Speaker 2: gonna sometimes make the night a little brighter or even
• 12:52
  Speaker 2: the day a little brighter, but it's not gonna have
• 12:54
  Speaker 2: that much effect. But you know, in a science fiction
• 12:56
  Speaker 2: sort of inspiration, we can move that second star in
• 12:59
  Speaker 2: as as much as possible and pretend that it does
• 13:02
  Speaker 2: have some impact because there's some crazy dynamics that happen
• 13:05
  Speaker 2: in that scenario.
• 13:07
  Speaker 1: Okay, let's go for it. What is that like super winter?
• 13:12
  Speaker 2: Yeah, exactly. If you think about the periods when you
• 13:15
  Speaker 2: have sunlight, that really is what determines the seasons. Right
• 13:18
  Speaker 2: in a single star, single planet system, it's the number
• 13:21
  Speaker 2: of hours per day of sunlight you get that determine
• 13:24
  Speaker 2: the seasons. And in the summer you're getting more sun.
• 13:26
  Speaker 2: In the winter, you're getting less sun. Now put that
• 13:28
  Speaker 2: second star around, say we have the second star, you know,
• 13:31
  Speaker 2: in Mars orbit or something crazy, then you're going to
• 13:35
  Speaker 2: be getting sunlight all sorts of weird configurations, like there
• 13:37
  Speaker 2: can be parts of the year where each star is
• 13:41
  Speaker 2: illuminating a different side of the planet. Put the planet
• 13:44
  Speaker 2: between the two stars. Right, they're all in a line.
• 13:47
  Speaker 2: You have star, planet Star, then every part of the
• 13:49
  Speaker 2: surface is seeing a star. Right, It's like the whole
• 13:52
  Speaker 2: world has noon at the same time, right, which would
• 13:56
  Speaker 2: be crazy. So you have periods where the whole planet
• 13:59
  Speaker 2: is seeing star, and then other scenarios where like in
• 14:03
  Speaker 2: a line it goes star star planet where half of
• 14:06
  Speaker 2: the planet is seeing both stars at the same time,
• 14:10
  Speaker 2: and if they're both pretty close, that's gonna be superday.
• 14:13
  Speaker 2: That's like super noon, right, and that's gonna be very intense,
• 14:16
  Speaker 2: super duper hot. And also you'll get a weird effect
• 14:19
  Speaker 2: there where potentially the stars eclipse each other. So like
• 14:23
  Speaker 2: you know, we have solar eclipses and lunar eclipses, this
• 14:25
  Speaker 2: would be like a stellar eclipse where one sun is
• 14:28
  Speaker 2: behind the other sun briefly. That would be awesome.
• 14:31
  Speaker 1: Don't look at either.
• 14:36
  Speaker 2: But I actually looked up a simulator to try to
• 14:38
  Speaker 2: figure out exactly what would happen through the year, and
• 14:40
  Speaker 2: it depends crucially on the orbit of that second star.
• 14:45
  Speaker 2: If that second star has a period of about a year,
• 14:47
  Speaker 2: like the same as the planet's orbit, then you're gonna
• 14:50
  Speaker 2: have a regular cycle. But you're gonna have times in
• 14:53
  Speaker 2: the year where even at the equator you have no darkness,
• 14:55
  Speaker 2: like you see one sun and the planet spins and
• 14:57
  Speaker 2: you see the other sun. And so that's going to
• 15:00
  Speaker 2: be very summary, right, because it's all about the hours
• 15:03
  Speaker 2: of sunlight you get and other parts of the year
• 15:05
  Speaker 2: where you're seeing both suns at the same time, so
• 15:07
  Speaker 2: you're getting fewer hours of daylight, but they're more intense,
• 15:11
  Speaker 2: they're brighter. So you're gonna have these really weird periods.
• 15:15
  Speaker 2: I don't know how the plants would respond to that,
• 15:17
  Speaker 2: or how you would evolve in that kind of.
• 15:18
  Speaker 1: Configuration circadian rhythms, mm hmm.
• 15:21
  Speaker 2: It's gonna be a total mess, but it would be regular,
• 15:24
  Speaker 2: you know. And if, for example, the second star has
• 15:26
  Speaker 2: a longer period, it takes longer to go around that
• 15:29
  Speaker 2: first star and the planet, then its affects can slide
• 15:33
  Speaker 2: through the year, right, It's not like every June we
• 15:36
  Speaker 2: have double sun, every January we have one sun. It
• 15:39
  Speaker 2: can slowly offset and that must really affect like the
• 15:43
  Speaker 2: development of a civilization, you know, because we use the
• 15:46
  Speaker 2: regular seasons, and the regular day night cycle really is
• 15:49
  Speaker 2: a way to tell time. So either you have to
• 15:52
  Speaker 2: have much more complex mathematics before you can even begin
• 15:55
  Speaker 2: to use a calendar and develop it. Or maybe you
• 15:57
  Speaker 2: get some art or quicker because the calendar is more
• 16:00
  Speaker 2: complicated and it inspires more interesting mathematics. But the short
• 16:03
  Speaker 2: answer is that the seasons are going to be intense
• 16:06
  Speaker 2: and complicated, and it depends on a lot of the details,
• 16:09
  Speaker 2: exactly how fast that second star goes around the first star.
• 16:12
  Speaker 1: I wonder if it would hinder the establishment of civilizations,
• 16:16
  Speaker 1: because like being able to plan things like when you
• 16:18
  Speaker 1: plant your crops seems really important. I wonder if we'd
• 16:21
  Speaker 1: all be like wanderers because planning just isn't worth even trying,
• 16:24
  Speaker 1: but really fun to think about it. You know, there's
• 16:26
  Speaker 1: got to be a couple of sci fi novels in.
• 16:27
  Speaker 2: There, Yeah, exactly. And you know there's the famous book
• 16:31
  Speaker 2: The three Body Problem, where they have essentially this question,
• 16:35
  Speaker 2: except it's actually the four body problem because they have
• 16:37
  Speaker 2: three stars and a planet. I don't know why they
• 16:40
  Speaker 2: like couldn't figure out how to count to three. It's
• 16:43
  Speaker 2: already complicated enough with two stars. You don't need a
• 16:45
  Speaker 2: third star.
• 16:47
  Speaker 1: Yeah. Well, when Ada's done with her math homework, will
• 16:51
  Speaker 1: have her listen to this explanation and hear what she
• 16:54
  Speaker 1: had to say.
• 16:56
  Speaker 2: Maybe we should have her on in real time for
• 16:58
  Speaker 2: a follow up. Let's do it, hi Ada, thanks very
• 17:03
  Speaker 2: much for your question. I was curious what you thought
• 17:06
  Speaker 2: about our answer and if you have any follow up questions.
• 17:10
  Speaker 5: I understood like what I heard when I listened to
• 17:17
  Speaker 5: the podcast, m H. And I do have one follow
• 17:24
  Speaker 5: up question.
• 17:25
  Speaker 2: Oh goodie, what is it?
• 17:26
  Speaker 6: So?
• 17:28
  Speaker 5: Was our sun in this our source system like part
• 17:35
  Speaker 5: of a different source system and then was it ejected
• 17:38
  Speaker 5: out or was it just not like that?
• 17:45
  Speaker 2: Yeah, that's a great question. Unfortunately we don't know the answer.
• 17:48
  Speaker 2: Most stars are born with other stars nearby. There's like
• 17:52
  Speaker 2: sibling stars sometimes two, three, five, seven, as part of
• 17:55
  Speaker 2: a big nursery, and then they're separated, as you know,
• 17:59
  Speaker 2: gravity lings them around. But we don't know the history
• 18:02
  Speaker 2: of our star that far back, so probably it was
• 18:05
  Speaker 2: born with other stars, but we don't actually know. Maybe
• 18:08
  Speaker 2: one day we'll figure out some way to figure it out,
• 18:11
  Speaker 2: but for now we don't know the answer. Thank you,
• 18:14
  Speaker 2: thanks so much for your question.
• 18:32
  Speaker 1: All right, so now for something absolutely totally different, we
• 18:36
  Speaker 1: have a fantastic question from listener James Palmer, and it
• 18:40
  Speaker 1: is a question about meat bees otherwise known as vulture bees,
• 18:44
  Speaker 1: which I had not heard of, but is absolutely right
• 18:47
  Speaker 1: up my alley. So let's hear the question.
• 18:50
  Speaker 4: Hey, Kelly and Daniel, I have a burning desire to
• 18:52
  Speaker 4: know everything about meat wasps. I just heard about them,
• 18:56
  Speaker 4: and I feel like there's a lot to discuss here,
• 18:58
  Speaker 4: Like apparently they are carnivorous and the eat on like
• 19:00
  Speaker 4: flesh and like maybe it's rotting. Then they use that
• 19:03
  Speaker 4: to make their honey and stuff like meat honey. Please
• 19:09
  Speaker 4: tell me everything.
• 19:12
  Speaker 1: Meat honey, Daniel. You're dying to know about meat honey.
• 19:16
  Speaker 4: Right.
• 19:16
  Speaker 2: Well, you know, we have lots of different kinds of
• 19:18
  Speaker 2: honey here in California, and often it's sold to us
• 19:21
  Speaker 2: by promoting the kind of flowers that the bees visit,
• 19:23
  Speaker 2: like ooh, this is lavender honey or wildflower honey, and
• 19:27
  Speaker 2: you're supposed to imagine that you can taste the lavender
• 19:30
  Speaker 2: as you're eating the honey. And so I'm wondering, now,
• 19:32
  Speaker 2: meat bee honey, is it gonna taste like pepperoni or
• 19:35
  Speaker 2: what's going on?
• 19:36
  Speaker 1: Oh gosh, you know, to be honest, I would never
• 19:39
  Speaker 1: try it. But there's not a lot of honey that
• 19:42
  Speaker 1: is meat honey. So there's a lot of bees that
• 19:45
  Speaker 1: make something called honey, but there's only three species that
• 19:49
  Speaker 1: do this meat honey thing exclusively. So I think maybe
• 19:52
  Speaker 1: we should start with how honey is made. Yea, because
• 19:55
  Speaker 1: I actually didn't understand this very well.
• 19:57
  Speaker 2: I have this naive understanding that like bee eat pollen
• 20:01
  Speaker 2: and then do something internally and then vomit up honey.
• 20:03
  Speaker 2: How wrong is that?
• 20:04
  Speaker 1: Yeah? I thought that too, Okay, totally, like almost one
• 20:07
  Speaker 1: hundred percent. Okay, so that was my thought too. Okay,
• 20:09
  Speaker 1: So let's start with the European honey bees as an example. Okay,
• 20:12
  Speaker 1: So this is APIs Melfera, and what they do is
• 20:16
  Speaker 1: they go out and they go to flowers, and the
• 20:18
  Speaker 1: flowers produce both nectar, which is like sugar water, and pollen,
• 20:23
  Speaker 1: which has a lot of protein. And so these fill
• 20:25
  Speaker 1: two very different rolls for the bees. So they get
• 20:28
  Speaker 1: their carbohydrates from the nectar, okay, and that's gonna become honey,
• 20:32
  Speaker 1: and then the pollen is their protein source. And sometimes
• 20:35
  Speaker 1: the pollen like gets in the honey. It almost sounds
• 20:37
  Speaker 1: like it's accidental, but mostly the honey is from the nectar.
• 20:43
  Speaker 1: Not from the pollen, but.
• 20:44
  Speaker 2: The bees also eat the pollen. I thought the pollen
• 20:46
  Speaker 2: was incidental and going along for a ride, and it
• 20:48
  Speaker 2: was part of the plants deal with the bees, Like
• 20:50
  Speaker 2: you can eat the nectar, but then I'm gonna get
• 20:52
  Speaker 2: the pollen all over you and you're gonna drop it
• 20:54
  Speaker 2: on another flower and help us reproduce.
• 20:57
  Speaker 1: No, they eat it too. Oh no, they eat it
• 20:59
  Speaker 1: and they feed it to like the baby bees, and
• 21:02
  Speaker 1: so it's like a very important protein source. I didn't
• 21:05
  Speaker 1: know that either. And actually there's four different kinds of bees.
• 21:08
  Speaker 1: There's the honey bees, the orchid bees, the bumblebees, and
• 21:11
  Speaker 1: the stingless bees. And they're all categorized by having what
• 21:14
  Speaker 1: are called corbicula and these are like chunky thighs with
• 21:19
  Speaker 1: like a way to like stick the pollen on there.
• 21:23
  Speaker 1: And so like I saw a bee on one of
• 21:25
  Speaker 1: our flowers the other day and I was like, what
• 21:27
  Speaker 1: is this orange? Like it's like they've got bling on
• 21:29
  Speaker 1: their hips. I know, as an ecologist, I should have
• 21:31
  Speaker 1: been like mortified that I didn't know what this was already.
• 21:34
  Speaker 1: But anyway, those are like four carrying pollen around so
• 21:36
  Speaker 1: they can bring it back to the.
• 21:37
  Speaker 2: Hive, I see, And so do the plants get anything
• 21:40
  Speaker 2: out of it? I thought bees were pollinators.
• 21:42
  Speaker 1: Yeah, I think some of it still like falls off
• 21:44
  Speaker 1: and lands in the right place, so the pollination still happens.
• 21:47
  Speaker 1: But the bees aren't moving the pollen around as a favor.
• 21:50
  Speaker 1: It's more like incidental. So that's how nature. No one
• 21:55
  Speaker 1: helps anyone out in nature unless they have to, all right.
• 21:57
  Speaker 2: So bees drink pollen and then they use that to
• 22:00
  Speaker 2: make the honey. How do they actually make the honeyes
• 22:02
  Speaker 2: that inside the bee? Or is that in one of
• 22:04
  Speaker 2: their little hexagonal cooking vats.
• 22:07
  Speaker 1: Bees drink nectar. They don't drink the pollen.
• 22:10
  Speaker 2: Oh sorry, right, yes, okay.
• 22:11
  Speaker 1: That's okay. Or they sometimes drink a honeydew, which is
• 22:14
  Speaker 1: this like sweet fluid produced by insects as like a
• 22:17
  Speaker 1: way to attract organisms that like protect them from natural enemies.
• 22:21
  Speaker 1: They collect it in this special organ where they collect
• 22:24
  Speaker 1: all of this sugary water, and you know, they can
• 22:27
  Speaker 1: use it a little bit for like their flight to
• 22:29
  Speaker 1: get from place to place, but they're you know, trying
• 22:31
  Speaker 1: to bring it back to the hive. So they fill
• 22:33
  Speaker 1: up this organ and I think that something like half
• 22:35
  Speaker 1: of their body weight can end up being this sugary water.
• 22:39
  Speaker 1: But the sugary water is nowhere near concentrated enough to
• 22:43
  Speaker 1: be honey. So what they do is they bring it
• 22:45
  Speaker 1: back to the hive and they regurgitate it to bees
• 22:48
  Speaker 1: whose job it is to try to get some of
• 22:51
  Speaker 1: the water out and concentrate the sugars more. And so
• 22:55
  Speaker 1: those bees they like start kind of partially regurgitating it
• 22:59
  Speaker 1: and blowing these like bubbles that increase the surface area,
• 23:02
  Speaker 1: so some of the water evaporates off it.
• 23:04
  Speaker 2: Didn't know that the physics of honey look at that, Yes, right, And.
• 23:08
  Speaker 1: I hadn't imagined that so much of honey involved vomit.
• 23:11
  Speaker 1: But there you go, so much fun hanging out with biologists.
• 23:16
  Speaker 2: When I'm vomiting, I'm not busy also trying to concentrate
• 23:19
  Speaker 2: it and evaporate it. So I have like gooey or vomit.
• 23:22
  Speaker 2: I guess that's what a bee does.
• 23:24
  Speaker 1: I mean, you're not so great at multitasking. Too bad.
• 23:28
  Speaker 2: I'll work on that. I'll work on that. You know,
• 23:30
  Speaker 2: good to have goals. Yeah, all right, So bees vomit
• 23:32
  Speaker 2: up the nectar, and then other specialized bees help evaporate
• 23:36
  Speaker 2: and concentrate it into honey. So that mean that honey
• 23:39
  Speaker 2: is just nectar that's been concentrated down or is there
• 23:42
  Speaker 2: some fermentation that also happens.
• 23:44
  Speaker 1: That's just one of the stages of evaporation that gets
• 23:47
  Speaker 1: a little bit of the water out, and then when
• 23:49
  Speaker 1: they store it in the combs, like the you know,
• 23:51
  Speaker 1: honey combs, I'm under the impression that some more evaporation
• 23:54
  Speaker 1: happens there. So bees produce a little bit of heat
• 23:57
  Speaker 1: by like, you know, shaking their wings really fast. That
• 23:59
  Speaker 1: also produces some airflow over the honeycombs, and that combination
• 24:03
  Speaker 1: of heat and then air moving throughout the colony and
• 24:07
  Speaker 1: then sort of back out of the hive, that finishes
• 24:09
  Speaker 1: evaporating off the water until you get to a point
• 24:12
  Speaker 1: where you've got enough concentrated sugar that you've got honey.
• 24:15
  Speaker 2: Wow. Fascinating.
• 24:17
  Speaker 1: Yeah, I didn't know any of that. That was awesome.
• 24:19
  Speaker 2: So then it makes sense that if I'm eating the
• 24:21
  Speaker 2: honey from bees that visited lavender, it shit tastes like
• 24:24
  Speaker 2: lavender because it really is like concentrated lavender nectar.
• 24:27
  Speaker 1: If lavender nectar smells like lavender, I don't know that
• 24:32
  Speaker 1: it does. And I'm one of those people who has
• 24:34
  Speaker 1: had honey from different places and been like, it's all
• 24:36
  Speaker 1: honey to me. I don't have a delicate paletate.
• 24:39
  Speaker 2: Okay, So now tell us about meat wasps. Where do
• 24:42
  Speaker 2: they get their supplies to make honey?
• 24:45
  Speaker 1: Okay?
• 24:45
  Speaker 2: So I'm terrified of this answer, by the way.
• 24:48
  Speaker 1: Yeah, all right. So the best honeymakers are the European
• 24:51
  Speaker 1: honey bees, the best in terms of like producing honey
• 24:53
  Speaker 1: that humans like, but a bunch of other kinds of
• 24:55
  Speaker 1: bees they make similar honey, but often their honey is
• 24:58
  Speaker 1: nowhere near as like concentrated with sugars. It's more watery.
• 25:02
  Speaker 1: And there's a group of bees called the stingless bees,
• 25:05
  Speaker 1: and now we're getting closer to the vulture bees. So
• 25:08
  Speaker 1: the stingless bees they make honey, but their honey tends
• 25:11
  Speaker 1: to be more watery, and instead of storing it in
• 25:13
  Speaker 1: those combs, they make these little waxy pots, and it's
• 25:18
  Speaker 1: harder to get it out of those waxy pots, and
• 25:21
  Speaker 1: it's like more watered down when you do. So people
• 25:24
  Speaker 1: did still keep these bees for sugary fluids, but as
• 25:28
  Speaker 1: soon as honey bees came along, a lot of the
• 25:30
  Speaker 1: stingless bees that do this more watered down, harder to
• 25:32
  Speaker 1: get honey, they became less popular to culture. But so
• 25:37
  Speaker 1: these stingless bees, they also get their nectar from flowers,
• 25:40
  Speaker 1: but there's a group in the genus Trigona where they
• 25:45
  Speaker 1: seem like they're less interested in flowers. So instead of
• 25:48
  Speaker 1: going to flowers for nectar, they get their sugars from
• 25:52
  Speaker 1: things like rotting fruits. They'll like take the sugars from that.
• 25:56
  Speaker 1: And instead of getting pollen, they get their protein from
• 26:01
  Speaker 1: dead animals, dead vertebrates in particular.
• 26:04
  Speaker 2: I see. So that's why they're called vulture bees, because
• 26:06
  Speaker 2: vultures are scavengers. They don't kill anything. They eat already
• 26:08
  Speaker 2: dead stuff. So these vulture bees will get their protein
• 26:11
  Speaker 2: not from pollen, but from dead animals.
• 26:13
  Speaker 1: You're saying, that's right. And they'll get their sugar, which
• 26:16
  Speaker 1: they used, you know, like make their honey stuff. They
• 26:18
  Speaker 1: get that from things like writing fruit are free they find, Okay,
• 26:22
  Speaker 1: So then the question is do they make meat honey?
• 26:26
  Speaker 1: This is important and the answer I think is maybe.
• 26:31
  Speaker 6: Oh.
• 26:32
  Speaker 2: Really.
• 26:32
  Speaker 1: So there's only three species of these vulture bees, and
• 26:35
  Speaker 1: they're all in the same genus, they're all closely related.
• 26:38
  Speaker 1: It does turn out that there's a fair number of
• 26:40
  Speaker 1: stingless bees that where like, if meat is left out,
• 26:44
  Speaker 1: they'll go ahead and get some protein from it, but
• 26:46
  Speaker 1: they're not required to get protein from it, so they're
• 26:48
  Speaker 1: called facultatively necrophagic, which means they'll like eat dead stuff
• 26:52
  Speaker 1: when they've got the chance, but they don't have to.
• 26:54
  Speaker 1: But these vulture bees are obligately necrophagic, so they have
• 26:58
  Speaker 1: to eat dead stuff. And currently they're really good at it,
• 27:01
  Speaker 1: Like they've got ways to sort of attract other members
• 27:03
  Speaker 1: to come so that they can like very quickly with
• 27:05
  Speaker 1: these specialized mouth parts scrape a bunch of like rotting flesh.
• 27:10
  Speaker 1: Oh my god, yeah, your face is like priceless.
• 27:12
  Speaker 2: It should be called nightmare bees. Yikes.
• 27:15
  Speaker 1: Yes, it's intense pretty metals. So then it's a little
• 27:17
  Speaker 1: bit unclear what happens. So I found a nineteen eighty
• 27:20
  Speaker 1: two paper that described what they were doing, and it
• 27:24
  Speaker 1: said the bees masticate and consume flesh at the feeding site.
• 27:29
  Speaker 1: They do not carry pieces of flesh to the nest,
• 27:32
  Speaker 1: but appear to hydrolyze it with a secretion produced by
• 27:36
  Speaker 1: either mandibular or salivary glands, which gives the feeding site
• 27:40
  Speaker 1: a wet appearance. Side note iw.
• 27:44
  Speaker 2: That means they're slabbering right their slabberry and they have
• 27:47
  Speaker 2: meat slabber.
• 27:47
  Speaker 1: They've got meat slabber, and their saliva is starting the
• 27:50
  Speaker 1: process of breaking down the meat. That's what that means.
• 27:53
  Speaker 1: And that says individual bees captured well feeding, then forced
• 27:56
  Speaker 1: to expel the contents of their crop. So essentially they
• 27:58
  Speaker 1: made these meat bees. Through up, we're carrying a slurry
• 28:02
  Speaker 1: of flesh measuring between thirty seven and sixty five percent
• 28:06
  Speaker 1: dissolved solids by volume.
• 28:07
  Speaker 2: So a slurry of flesh. Isn't that like a nine
• 28:10
  Speaker 2: Inch Nails album title or something.
• 28:14
  Speaker 1: I feel like we have to get in touch with
• 28:16
  Speaker 1: prent Resnor now and find some way to convey this
• 28:19
  Speaker 1: to him.
• 28:19
  Speaker 2: Oh boy wow.
• 28:21
  Speaker 1: And so then the question is how do they store
• 28:22
  Speaker 1: it when they get back. So I've read this paper
• 28:24
  Speaker 1: from twenty twenty one and they were laying out some
• 28:26
  Speaker 1: different hypotheses for what happens. It looks like that meat
• 28:29
  Speaker 1: slurry gets stored in pots. Maybe it gets mixed with
• 28:32
  Speaker 1: some of the sugary stuff they collect. I think at
• 28:34
  Speaker 1: the end of the day, it's not really clear what
• 28:37
  Speaker 1: they do how it's stored how long it's stored, but
• 28:40
  Speaker 1: you probably could say they make something called meat honey,
• 28:43
  Speaker 1: like they're taking that flesh slurry, they're storing it in
• 28:47
  Speaker 1: these pots. It looks like it quote unquote matures for
• 28:52
  Speaker 1: about two weeks into a paste that is also a
• 28:55
  Speaker 1: little bit sugary. So they do appear to be making
• 28:58
  Speaker 1: something like meat honey. Let's go for it. Looks like
• 29:01
  Speaker 1: part of this process and if your wife we're here,
• 29:03
  Speaker 1: maybe she'd be excited about this part. Part of it
• 29:05
  Speaker 1: appears to involve the microbiome. So these vulture bees have
• 29:10
  Speaker 1: microbiomes that include acidophilic bacteria, so bacteria that do really
• 29:15
  Speaker 1: well in acidic environments. And you find similar categories of bacteria,
• 29:20
  Speaker 1: they're not the exact same species, similar categories of bacteria
• 29:23
  Speaker 1: in the guts of like vultures. So it seems like
• 29:26
  Speaker 1: there's some kinds of bacteria that team up with organisms
• 29:29
  Speaker 1: that eat dead flesh to sort of help process it
• 29:32
  Speaker 1: and maybe also help make it safer, because bacteria that
• 29:34
  Speaker 1: get to the flesh first start producing like toxins maybe
• 29:37
  Speaker 1: to ward off these competitors, and these acid loving bacteria
• 29:41
  Speaker 1: sort of help make it all happen, and your face
• 29:43
  Speaker 1: is just priceless.
• 29:44
  Speaker 2: Right now, I'm so glad I don't eat breakfast because
• 29:47
  Speaker 2: I'd be throwing it up into breakfast slurry right now,
• 29:50
  Speaker 2: and some bees could come along and make breakfast.
• 29:52
  Speaker 1: Honey, meat honey, and so James, I have to thank you.
• 29:57
  Speaker 1: I had never heard of these before. And let's go
• 30:00
  Speaker 1: ahead and hear if you learned everything you wanted to
• 30:03
  Speaker 1: know about meat honey, and.
• 30:06
  Speaker 2: If you're ever gonna eat honey again.
• 30:09
  Speaker 6: I think it's safe to say that you taught me
• 30:10
  Speaker 6: everything I asked for and a lot more. So thanks
• 30:13
  Speaker 6: ver so much for that, guys. I appreciate it.
• 30:31
  Speaker 2: All right. Our last question comes from Hans in the
• 30:34
  Speaker 2: Netherlands who has a nephew in Perth, and they've been
• 30:37
  Speaker 2: disagreeing about which direction the Earth is accelerating and how
• 30:42
  Speaker 2: gravity actually works. Let's hear the question from Hans.
• 30:46
  Speaker 3: I have a question concerning freefall, as I understand it,
• 30:49
  Speaker 3: when you're in freefall, you don't move it all. Instead,
• 30:52
  Speaker 3: the Earth is ration to watch you. Now my question
• 30:55
  Speaker 3: is this. I live in Howder, which is in the
• 30:57
  Speaker 3: rest of the Netherlands. I have a nephew in Perth, Australia,
• 31:01
  Speaker 3: which is roughly the opposite side of the earth. Well,
• 31:04
  Speaker 3: we decided to jump out of an airplane on the
• 31:06
  Speaker 3: same time, which way is the earth moving? Thank you
• 31:09
  Speaker 3: very much for your answer.
• 31:10
  Speaker 1: All right, so you know, maybe first we should start
• 31:12
  Speaker 1: with the disclaimer that you shouldn't do this unless you're
• 31:15
  Speaker 1: a professional. Have you ever done sky jumping or have
• 31:19
  Speaker 1: you ever jumped from a plane?
• 31:20
  Speaker 2: I one time did skydiving. Yes, I jumped from an
• 31:23
  Speaker 2: airplane exactly one time. And I did it one time
• 31:26
  Speaker 2: because I did my homework and I looked up how
• 31:28
  Speaker 2: often people die skydiving, and it turns out it's very
• 31:32
  Speaker 2: very rare to die the first time you jump, and
• 31:34
  Speaker 2: it's very very rare to die after like ten jumps.
• 31:37
  Speaker 2: But there's a danger zone between like two and nine jumps.
• 31:42
  Speaker 2: And my understanding is that the first time you jump,
• 31:44
  Speaker 2: you're very careful, you're freaked out, you check all the straps,
• 31:47
  Speaker 2: you're like following all the safety videos, and when you
• 31:50
  Speaker 2: survive that first time, you're like, oh, maybe it's not
• 31:52
  Speaker 2: so dangerous. And then you get sloppy. And when you
• 31:55
  Speaker 2: get sloppy and you're like feeling confident, that's the danger zone.
• 31:59
  Speaker 2: Then and if you survive like nine or ten jumps,
• 32:01
  Speaker 2: you become really good at it, and then you're back
• 32:04
  Speaker 2: in the safe zone. So I did it once. I survived,
• 32:07
  Speaker 2: and I'm never doing it again.
• 32:09
  Speaker 1: Wait, you controlled your own parachute and everything when you jumped.
• 32:11
  Speaker 2: I got to pull my parachute, but it was a
• 32:13
  Speaker 2: tandem jump of strapped to another dude who was there
• 32:15
  Speaker 2: to like make sure I did it right.
• 32:16
  Speaker 1: But yeah, when I did it, there was a dude
• 32:18
  Speaker 1: on my back. Okay, I mean, did you ask the
• 32:20
  Speaker 1: guy on your back is this your second to ninth jump?
• 32:23
  Speaker 1: That's the guy you need to ask. I think that's right.
• 32:27
  Speaker 2: It might be his second and ninth jump that day.
• 32:29
  Speaker 2: I think these guys go up all the time.
• 32:31
  Speaker 1: Yeah, yeah, I think so too.
• 32:33
  Speaker 2: But it was sort of terrifying because they told us, hey,
• 32:35
  Speaker 2: you can change your mind at any moment. And the
• 32:37
  Speaker 2: friend I went with, she was standing at the edge
• 32:40
  Speaker 2: of the door ready to jump out, and she was like, yeah, no,
• 32:43
  Speaker 2: I can't do it, and they're like, no, you're doing it.
• 32:45
  Speaker 2: And she's like, you said I could change my mind,
• 32:47
  Speaker 2: and they're like, we were lying. Nobody changes their mind,
• 32:49
  Speaker 2: and then they pushed her out the door.
• 32:53
  Speaker 1: I had brought a boyfriend who you know didn't end
• 32:55
  Speaker 1: up marrying, maybe not surprisingly after you hear this story
• 32:57
  Speaker 1: for his birthday. Oh and he got to the door
• 33:00
  Speaker 1: and he said, I don't want to do it. And
• 33:02
  Speaker 1: the guy strapped to his back looked at me, and
• 33:03
  Speaker 1: I said, and I pointed out, and the guy jumped.
• 33:08
  Speaker 1: And you know, my boyfriend was happy afterwards that he
• 33:10
  Speaker 1: did it, but he had also tried to back out
• 33:12
  Speaker 1: at the last second.
• 33:13
  Speaker 2: So folks, when they tell you you can back out,
• 33:15
  Speaker 2: don't believe them if you don't want to jump, and
• 33:17
  Speaker 2: don't go up in the plane. Yeah, all right, but
• 33:19
  Speaker 2: today we are not giving advice about ways to risk
• 33:22
  Speaker 2: your life and get adrilline thrills. We're talking about understanding
• 33:26
  Speaker 2: the fundamental nature of gravity, how does it work? And Hans,
• 33:30
  Speaker 2: I think is responding to a conversation we had about
• 33:32
  Speaker 2: gravity and freefall and who's really accelerating, in which an
• 33:36
  Speaker 2: explanation I gave is that the Earth is accelerating up
• 33:39
  Speaker 2: and out towards you. You're not falling towards the Earth.
• 33:43
  Speaker 2: And so I think it's worthwhile to revisit that explanation
• 33:46
  Speaker 2: a little bit and then unpack it in the context
• 33:48
  Speaker 2: of Hans's question, All.
• 33:49
  Speaker 1: Right, let's go for it. So if you jump out
• 33:51
  Speaker 1: of a plane, what does Newton say is happening?
• 33:54
  Speaker 2: Yeah, So, from a Newton point of view, if you're
• 33:56
  Speaker 2: on the surface and you see somebody jump out of
• 33:58
  Speaker 2: an airplane, you say, is a force of gravity and
• 34:01
  Speaker 2: forces create acceleration. So gravity is accelerating you down towards
• 34:05
  Speaker 2: the surface. And that's Newton's explanation. And from the point
• 34:08
  Speaker 2: of view of the person on the surface, that makes
• 34:09
  Speaker 2: perfect sense because you see somebody's velocity and they're accelerating
• 34:13
  Speaker 2: because their velocity is changing, and so it looks perfectly
• 34:16
  Speaker 2: like there's a force there and the person is accelerating.
• 34:19
  Speaker 2: From the point of view of the jumper, right, they
• 34:22
  Speaker 2: jump out of the airplane, they see the surface of
• 34:23
  Speaker 2: the Earth rushing towards them. Right, they see Earth accelerating
• 34:27
  Speaker 2: towards them. Now, velocity is perfectly relative, right, And so
• 34:31
  Speaker 2: you might wonder, like, well, who's right, who is actually accelerating?
• 34:36
  Speaker 2: And this is where Einstein comes in, because Einstein tells
• 34:39
  Speaker 2: us that, like, velocity is relative, but acceleration is not.
• 34:44
  Speaker 2: So let's unpack what that means for a moment like
• 34:46
  Speaker 2: we say that distance is relative, like Kelly and I
• 34:49
  Speaker 2: are three thousand miles from each other right now. And
• 34:52
  Speaker 2: when we say distance is relative, we mean that you
• 34:54
  Speaker 2: have to measure it relative to somewhere else. Like I
• 34:57
  Speaker 2: can say I'm three thousand miles from Kelly. I can't
• 35:01
  Speaker 2: just say I am three thousand miles. That doesn't have
• 35:04
  Speaker 2: any meaning, right, I have to say what I'm three
• 35:05
  Speaker 2: thousand miles away from. Velocity is also relative. I can
• 35:10
  Speaker 2: say I have zero velocity right now relative to Kelly,
• 35:14
  Speaker 2: but I don't have zero velocity relative to the Sun.
• 35:16
  Speaker 2: And I don't have zero velocity relative to some particle
• 35:20
  Speaker 2: that's speeding towards the Earth at almost the speed of light.
• 35:22
  Speaker 2: In fact, I'm traveling at nearly the speed of light
• 35:24
  Speaker 2: relative to that particle, right And so velocity is only
• 35:28
  Speaker 2: defined relative to other stuff. And that's confusing because when
• 35:33
  Speaker 2: somebody jumps out an airplane, you wonder, like, well, are
• 35:35
  Speaker 2: they moving towards the Earth? Is the Earth moving towards them?
• 35:38
  Speaker 2: Both of those are perfectly valid. Because velocity is relative,
• 35:41
  Speaker 2: you can't say which one's actually moving. But now you
• 35:44
  Speaker 2: get to acceleration. Acceleration is different. Acceleration is not relative.
• 35:49
  Speaker 2: Velocity is relative. It's a property of a pair of objects,
• 35:52
  Speaker 2: me and Kelly, and me and the Earth, me and
• 35:54
  Speaker 2: the Sun. But acceleration is a property of an object.
• 35:57
  Speaker 2: I can tell if I'm accelerating. You can tell if
• 36:00
  Speaker 2: you're accelerating. How can you do that? Well, say, for example,
• 36:03
  Speaker 2: you're in a truck and you have a bowling ball
• 36:05
  Speaker 2: in the back of the truck. You can tell when
• 36:07
  Speaker 2: somebody hits the brake on the truck. You can tell
• 36:09
  Speaker 2: when somebody accelerates because the bowling ball in the back
• 36:12
  Speaker 2: of the truck will respond. What happens if you hit
• 36:14
  Speaker 2: the brakes, the bowling ball keeps going and will bang
• 36:18
  Speaker 2: into the front of the truck bed. And if you accelerate,
• 36:21
  Speaker 2: the bowling ball rolls backwards towards the back of the
• 36:24
  Speaker 2: truck bed. So you can measure your acceleration yourself. You
• 36:27
  Speaker 2: don't need to measure relative to the Sun or the
• 36:30
  Speaker 2: Earth or your podcast co host or anything like that.
• 36:34
  Speaker 2: So that means you can do something interesting. You can
• 36:35
  Speaker 2: ask like, well, is the guy who jumped out of
• 36:39
  Speaker 2: an airplane is he accelerating? Or is the guy on
• 36:42
  Speaker 2: the ground on the Earth are they accelerating because both
• 36:45
  Speaker 2: of them think the other one is accelerating. But Einstein says, no,
• 36:48
  Speaker 2: you can actually just measure it and you can tell
• 36:50
  Speaker 2: the answer.
• 36:51
  Speaker 1: And the answer is that the person who jumped is accelerating.
• 36:54
  Speaker 2: No, the answer is the person on the earth is accelerating. No, yes, absolutely.
• 36:58
  Speaker 2: Imagine you jump out an airplane and you're holding a
• 37:00
  Speaker 2: box with like a billiard ball in it. Right, what's
• 37:03
  Speaker 2: going to happen to that ball? You feel like you're
• 37:05
  Speaker 2: accelerating towards the surface of the Earth. But you look
• 37:07
  Speaker 2: at the ball. The ball is not moving inside the box.
• 37:10
  Speaker 2: The ball is going with you. It has exactly the
• 37:12
  Speaker 2: same experience you do. Now somebody on the surface of
• 37:15
  Speaker 2: the Earth, they have a ball in the box. That
• 37:18
  Speaker 2: ball is pulled towards the surface of the Earth. That's
• 37:21
  Speaker 2: measuring acceleration. Another way to do this is to have
• 37:24
  Speaker 2: a scale. So you jump out of an airplane with
• 37:26
  Speaker 2: a scale, and now you stand on the scale. Are
• 37:29
  Speaker 2: you going to measure anything? No, because there's nothing pushing
• 37:32
  Speaker 2: you onto the scale. Whereas if you put the scale
• 37:34
  Speaker 2: in the surface of the Earth and you stand on it,
• 37:37
  Speaker 2: you're going to measure your weight. Right, that weight is
• 37:40
  Speaker 2: actually measuring your acceleration. Einstein says, what's happening there is
• 37:44
  Speaker 2: the surface of the Earth and that scale are accelerating
• 37:48
  Speaker 2: up and out right. So a scale is like an accelerometer.
• 37:53
  Speaker 2: And so when you jump out of an airplane, you
• 37:54
  Speaker 2: can measure that you're not accelerating. You're in free fall.
• 37:58
  Speaker 2: There is no gravitational force on you, because there is
• 38:00
  Speaker 2: no gravitational force on the surface of the Earth. What
• 38:04
  Speaker 2: you're measuring is not the force of gravity. The weight
• 38:07
  Speaker 2: doesn't measure the force of gravity. It measures the acceleration
• 38:10
  Speaker 2: of the surface of the Earth up and out away
• 38:14
  Speaker 2: from the center of the Earth.
• 38:16
  Speaker 1: That's counterintuitive, yeah, exactly, but it actually makes much more sense.
• 38:20
  Speaker 2: The way to think about forces and acceleration and gravity
• 38:23
  Speaker 2: is to remember that there can be apparent forces like say,
• 38:28
  Speaker 2: for example, you have a merry go round and somebody
• 38:30
  Speaker 2: spins the merry go round. You feel this force pushing
• 38:34
  Speaker 2: you off the merry go round, right, But there's no
• 38:36
  Speaker 2: force there. There's nobody pushing on you. It feels like
• 38:39
  Speaker 2: there's a force. There's an apparent force what we call
• 38:41
  Speaker 2: in physics a pseudo force, because you're accelerating, because you're
• 38:45
  Speaker 2: rotating creates this pseudo force. So some things in the
• 38:49
  Speaker 2: universe can create these pseudo forces that make it seem
• 38:52
  Speaker 2: like there's a force when there isn't really one. And
• 38:54
  Speaker 2: that's what space does. That's what gravity is. Gravity isn't
• 38:58
  Speaker 2: a force. It's just that space is bent in certain ways,
• 39:01
  Speaker 2: and objects like to follow the curvature of that space. So,
• 39:05
  Speaker 2: for example, near a huge mass, space is bent and
• 39:08
  Speaker 2: objects like to follow the curvature of space, which brings
• 39:12
  Speaker 2: them towards the center of that mass. You jump out
• 39:15
  Speaker 2: of an airplane, space is curved there. Because you're near
• 39:18
  Speaker 2: the Earth and your natural motion is towards the surface
• 39:21
  Speaker 2: of the Earth, and you need acceleration. You need a
• 39:24
  Speaker 2: force to prevent you from moving in free fall, to
• 39:27
  Speaker 2: work against the motion of space and time. So I
• 39:30
  Speaker 2: understand Hans's question. Hans is like, hold on, you're saying
• 39:32
  Speaker 2: the Earth is accelerating. How can it be accelerating up
• 39:36
  Speaker 2: in the Netherlands and up from Perth? Right, it seems
• 39:39
  Speaker 2: like it's going in two directions. And that's because you're
• 39:41
  Speaker 2: thinking about the Earth as a single sphere moving in
• 39:45
  Speaker 2: one direction or moving in the other direction. Instead, imagine
• 39:48
  Speaker 2: it as a sphere with variable radius. Gravity is trying
• 39:51
  Speaker 2: to shrink the Earth down into a dot, and the
• 39:54
  Speaker 2: structure of the Earth is pushing back up and out
• 39:56
  Speaker 2: in every direction. So the answer is that it's accelera
• 40:00
  Speaker 2: up and out in the Netherlands and up and out
• 40:03
  Speaker 2: in Perth. Both are out away from the center. If
• 40:06
  Speaker 2: there wasn't that acceleration, if the whole Earth was just
• 40:09
  Speaker 2: a bunch of particles following the curvature of space time,
• 40:12
  Speaker 2: it would collapse into a black hole. That's what gravity
• 40:14
  Speaker 2: wants to do. It gathers stuff together because it bends space,
• 40:18
  Speaker 2: and then the motion of those particles follows that bend
• 40:21
  Speaker 2: space and things fall together. So Earth has to push
• 40:24
  Speaker 2: up and out just to maintain the same distance from
• 40:28
  Speaker 2: the center. So it's counterintuitive because now I'm saying you
• 40:31
  Speaker 2: have to accelerate just to maintain a constant distance from
• 40:35
  Speaker 2: the center of the Earth. That's very counterintuitive, but it's
• 40:38
  Speaker 2: true because their natural motion is to fall in towards
• 40:41
  Speaker 2: the center, and you have to accelerate, which means counter
• 40:44
  Speaker 2: your motion relative to gravity, to avoid doing that. So, yeah, Hans,
• 40:49
  Speaker 2: the Earth is accelerating up under you and up under
• 40:52
  Speaker 2: your nephew in Perth.
• 40:53
  Speaker 1: Who does that make right? That's the important question.
• 40:58
  Speaker 2: Let's just all sit down over a night, play the
• 41:00
  Speaker 2: meat honey and work it out.
• 41:02
  Speaker 1: Oh no, let's never do that. Let's never ever do that,
• 41:06
  Speaker 1: or at least let's not be told that we're eating
• 41:08
  Speaker 1: meat honey if that's what we're having.
• 41:10
  Speaker 2: All right. Well, I hope that cleared it up for Hans.
• 41:12
  Speaker 2: Let's send him o answer and see if he's got
• 41:14
  Speaker 2: some follow up questions.
• 41:16
  Speaker 3: Hi, Daniel and Katie, thank you very much for your answer.
• 41:20
  Speaker 3: It was very enlightening. It still seemed somewhat counterintuitive to me,
• 41:24
  Speaker 3: but I believe I can now understand what you mean,
• 41:27
  Speaker 3: in particular the idea that you shouldn't see the Earth
• 41:30
  Speaker 3: as a solid object, but as a constant moving against
• 41:33
  Speaker 3: gravity to maintain the shape instantly. This reminds me of
• 41:36
  Speaker 3: Alison Wonderland. You have to run to stay in place.
• 41:39
  Speaker 3: I hope this makes any sense to you. Thank you
• 41:42
  Speaker 3: very much again, Hans.
• 41:43
  Speaker 1: Well, thanks to everybody who submitted a question. Please, we
• 41:46
  Speaker 1: want more people to submit more questions, and if you've
• 41:50
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• 41:52
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• 41:54
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• 41:56
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• 41:59
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• 42:00
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• 42:02
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• 42:04
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• 42:07
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• 42:12
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• 42:15
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• 42:19
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• 42:23
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• 42:24
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