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What was the pioneer anomaly? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, what's the first thing you think about when
0:11
Speaker 1: you see something in space you don't understand. Well, my
0:14
Speaker 1: first hope is always aliens. But my first thought is
0:18
Speaker 1: that it's probably a boring Mistand so as a scientist,
0:22
Speaker 1: your mind goes straight to the most dramatic explanation. Yeah,
0:26
Speaker 1: we're all hoping that somebody out there hits the science jackpot.
0:31
Speaker 1: Everybody wants to find the thing that frocks the world. Yeah,
0:34
Speaker 1: you know, people might not realize that science is a
0:36
Speaker 1: little bit like playing the lottery. It's mostly wrong numbers,
0:40
Speaker 1: but occasionally you get lucky and you win the alien jackpot.
0:44
Speaker 1: What's the price you might need to get wiped out? Yeah? Maybe,
0:48
Speaker 1: but think about what we might learn along the way
0:51
Speaker 1: in our dying moments. I am more hammy cartoonists and
1:09
Speaker 1: the creator of PhD comments. Hi, I'm Daniel. I'm a
1:13
Speaker 1: particle physicist, and I'm constantly on the hunt for something
1:16
Speaker 1: weird in science. Not in your department, in science in general.
1:21
Speaker 1: There's plenty of weird things in your department, weird stuff
1:24
Speaker 1: growing where it shouldn't be. But no, I'm looking for
1:26
Speaker 1: weird stuff in the data, hoping to win that jackpot
1:30
Speaker 1: is your data like it's a scratch of kind or
1:32
Speaker 1: like you make up the numbers. No, we are just
1:34
Speaker 1: looking at particles smashing together and hoping that something that
1:37
Speaker 1: comes out of it is unexplained. It's weird, it's something
1:40
Speaker 1: that our current theories of physics do not predict. Well,
1:43
Speaker 1: congratulations to all of you because you've won the jackpot.
1:45
Speaker 1: You are listening to our podcast Daniel and Jorge Explain
1:48
Speaker 1: the Universe, a production of I Heart Radio. And your
1:51
Speaker 1: prize is that you get to hear all about the incredible,
1:54
Speaker 1: amazing mysteries of our universe, all the weird stuff that's
1:58
Speaker 1: going on out there, all the little hints we have
2:01
Speaker 1: about weird stuff that might be going on that could
2:04
Speaker 1: be clues that reveal deep secrets about the nature of reality. Yeah,
2:08
Speaker 1: and just like a real lottery, this episode might be
2:10
Speaker 1: a winner or a dud. We'll find out. We'll have
2:13
Speaker 1: to scratch off the surface. The price is the same
2:15
Speaker 1: either way. That's right. The price is right meaning nothing,
2:18
Speaker 1: You get what you pay for. But yes, science is
2:22
Speaker 1: full of interesting mysteries out there, and it does happen
2:26
Speaker 1: a lot, doesn't it. Daniel, did the scientists look out
2:28
Speaker 1: into the world, or or try an experiment or do
2:31
Speaker 1: something and things don't happen the way you expect them
2:33
Speaker 1: to happen. Yep, everybody out there in graduate school knows
2:36
Speaker 1: that no experiment goes right the first time. But usually
2:39
Speaker 1: the reason you've got a weird result is that you
2:41
Speaker 1: messed it up a little bit. You didn't calibrate things,
2:44
Speaker 1: or you plug something in backwards, or you misread your
2:47
Speaker 1: instrument or something. Usually there's a conventional explanation. But what
2:50
Speaker 1: we're all looking for are those moments when you've done
2:54
Speaker 1: everything correctly but the answer is not what you expected. Yeah,
2:57
Speaker 1: don't they say that the real moments in science or
3:00
Speaker 1: not the eureka moments, but them that's interesting moments exactly
3:05
Speaker 1: wait a minute moment. There are sometimes those moments. There's
3:09
Speaker 1: a fantastic audio tape that's floating out there of recording
3:12
Speaker 1: of two astronomers listening to one of the first pulsars
3:16
Speaker 1: ever seen. They happen to be recording themselves for reasons
3:19
Speaker 1: I don't know, while they were observing, and you can
3:22
Speaker 1: hear them going, wait a second, look at this, Oh
3:24
Speaker 1: my gosh, is that what we think it is? WHOA
3:27
Speaker 1: that's interesting. Really, it's for real. Wasn't acted out so
3:30
Speaker 1: those especially they were being recorded. It's for real, it's
3:33
Speaker 1: for real. I encourage you to go out there and
3:35
Speaker 1: check it out. In fact, maybe we'll dig it out
3:37
Speaker 1: for our episode that's coming up on how pulsars were discovered.
3:40
Speaker 1: But yeah, most moments of scientific discovery like, dang it,
3:44
Speaker 1: my experiment didn't work. Well, maybe there's a better explanation,
3:47
Speaker 1: you know, after you check off all the boring explanations.
3:50
Speaker 1: Sometimes it's an exciting, fascinating explanation. Something new might be
3:54
Speaker 1: going on, or sometimes it's something routine. It could be
3:57
Speaker 1: either one absolutely and people might remember few years ago
4:00
Speaker 1: we thought we had discovered new trinos going faster than
4:04
Speaker 1: the speed of light. I won't say we there because
4:06
Speaker 1: I wasn't among the group of people I thought that
4:08
Speaker 1: was real. And humanity does something good, it's the royal
4:11
Speaker 1: we including when they mess it up, it's them, it's
4:15
Speaker 1: the Italians, them Italians. I won't touch that. But as
4:19
Speaker 1: soon as that paper came out and I saw that
4:21
Speaker 1: it had been written in Microsoft Word, I was like, no,
4:23
Speaker 1: there's something wrong with this paper. What do you mean?
4:26
Speaker 1: I wrote all my papers in Microsoft word. Yeah, point made.
4:30
Speaker 1: Actually I wrote them in Adobie FrameMaker, which tell you
4:33
Speaker 1: how old I am A little bit. Wow. That really
4:36
Speaker 1: does teach you. But usually, as in the case of
4:39
Speaker 1: the Fast and the Lighten New Trinos, is just a mistake.
4:42
Speaker 1: In that case, they forgot to plug a cable incorrectly
4:45
Speaker 1: and so their calibration was wrong and they mismeasured the speed.
4:48
Speaker 1: But sometimes these are famous experiments in the history of physics.
4:51
Speaker 1: We see something we don't understand and it's actually a clue.
4:55
Speaker 1: It's the first hint of a dramatic realization of uncovering
4:59
Speaker 1: something we had no idea about. And a great example
5:02
Speaker 1: is the photoelectric effect, which was an experiment around a
5:06
Speaker 1: hundred and twenty years ago that was the first clue
5:09
Speaker 1: that the universe was quantum mechanical. Yes, it was very
5:12
Speaker 1: illuminating and electrifying at the same time for humanity and
5:16
Speaker 1: very effective. Yeah. So today we'll be talking about one
5:19
Speaker 1: such mystery in science, and in particular in space science
5:22
Speaker 1: that happened a few years ago. Daniel right, how long
5:25
Speaker 1: ago was this or is it still ongoing? It was
5:28
Speaker 1: resolved a few years ago, but it went on for
5:30
Speaker 1: several decades. This is an outstanding mystery that puzzled people,
5:34
Speaker 1: that caused them to dig deep into their attic of
5:37
Speaker 1: ideas for possible boring and exciting explanations for what could
5:41
Speaker 1: be happening to this spacecraft. Yes, it involves spacecrafts and
5:46
Speaker 1: planets and basically just need toward space and mystery. And
5:49
Speaker 1: it's an interesting journey right here. Amazingly, there's almost no
5:53
Speaker 1: talk of aliens in this whole topic. Not yet. It
5:57
Speaker 1: spressed to surface Daniel and see if we can win
6:00
Speaker 1: the library here so to be on the program, we'll
6:03
Speaker 1: be talking about what is the Pioneer anomaly. Now, it's anomaly, right,
6:13
Speaker 1: not animone, Just get confused. It's not an underwater sea creature.
6:17
Speaker 1: It's not something you want deep fried and served before
6:20
Speaker 1: your dinner. It's an anomaly. It's something that's not understood,
6:23
Speaker 1: that's anomalous, and it's something that happened in space around
6:26
Speaker 1: what time. Well, it has to do with the Pioneer spacecraft,
6:30
Speaker 1: which was launched in the seventies and has one of
6:32
Speaker 1: these incredible careers. You know, they expected to go on
6:35
Speaker 1: for several years and then it operated for decades and
6:38
Speaker 1: decades and decades and of course it's still out there, right,
6:41
Speaker 1: Pioneer ten and Pioneer eleven are still out there flying
6:45
Speaker 1: out into the depths of space being pioneers. Of course,
6:49
Speaker 1: now I have to admit I did not know what
6:52
Speaker 1: the Pioneer spacecraft is or the anomaly. I was a
6:54
Speaker 1: little puzzled by this, but as usually, we were wondering
6:57
Speaker 1: how many of you out there no or new this
7:00
Speaker 1: Pioneer anomaly is. So thank you to everybody who volunteered
7:03
Speaker 1: to answer these questions. If you'd like to participate for
7:06
Speaker 1: a future episode, please don't be shy. Right to me
7:09
Speaker 1: two questions at Daniel and Jorge dot com. So think
7:12
Speaker 1: about it for a second. If someone asked you what
7:14
Speaker 1: the Pioneer anomaly is or was, what would you say.
7:20
Speaker 1: Here's what peopled to say. I don't know, but I
7:23
Speaker 1: imagine it's an abnormality're pretending to spacecraft or something. I'm
7:31
Speaker 1: not totally sure what the Pioneer a normally is. Um
7:34
Speaker 1: I can end the guest that has something to do
7:36
Speaker 1: with the Pioneer spacecraft that were launched in the early seventies.
7:40
Speaker 1: And I think, and now a very long why, I
7:45
Speaker 1: have no idea. I don't know I have no idea
7:48
Speaker 1: what the Pioneer anomaly was, but I assume it has
7:51
Speaker 1: something to do with the Pioneer spacecraft and obviously something
7:57
Speaker 1: that you would not normally expect to have of help them.
8:01
Speaker 1: I think that the Pioneer anomally was maybe like this
8:05
Speaker 1: first irregularity found about our universe, and since it's the
8:11
Speaker 1: Pioneer anomally, I think that this maybe marked like a
8:17
Speaker 1: turning point for scientists and made them more curious about
8:20
Speaker 1: what other anomalies can be found in our universe. Al Right,
8:24
Speaker 1: not a lot of name recognition here, No, I was
8:27
Speaker 1: a little surprised. I thought this was a little more famous.
8:30
Speaker 1: I remember hearing about this in high school and thinking, woh,
8:33
Speaker 1: that's cool. I bet that's something real. Whoa you heard
8:36
Speaker 1: about it in high school? Like, oh yeah, like in
8:39
Speaker 1: physics class, or how did you hear about it from
8:41
Speaker 1: your physics parents. I was a nerd, big shocker, so
8:46
Speaker 1: I just kind of interested in this stuff, and you know,
8:48
Speaker 1: anything out there in space that was unexplained, anything that
8:51
Speaker 1: might be a clue as to how something is working
8:54
Speaker 1: in the universe. I gobbled that stuff up to what
8:56
Speaker 1: I heard that we didn't understand where this spacecraft was
9:00
Speaker 1: and what it was doing, and why I was doing
9:02
Speaker 1: these weird things I thought. I think the real anomaly
9:06
Speaker 1: is that you used the past tense when you said
9:08
Speaker 1: you were a nerd. It's not up to me to
9:12
Speaker 1: evaluate that. All right, Well, there is something called the
9:15
Speaker 1: Pioneer anomaly, and let's break it down for people. Daniel,
9:18
Speaker 1: what is the Pioneer anomaly? So, as expected, it's an
9:22
Speaker 1: anomoly that has to do with the Pioneer spacecraft and
9:25
Speaker 1: specifically is that we didn't understand where it was going
9:29
Speaker 1: and why it seemed to be going off course for
9:32
Speaker 1: reasons we did not understand. Okay, so it was a spacecraft,
9:36
Speaker 1: meaning like a satellite. I always get confusible to say
9:40
Speaker 1: spacecraft because I imagine you know, Battlestar Galactica or you know,
9:45
Speaker 1: people in uh in a cockpit or something. But really
9:48
Speaker 1: would just mean, like, you know, any device we launched
9:51
Speaker 1: into space is called the spacecraft. Yeah, it's not a
9:54
Speaker 1: satellite because it's not in orbit around Earth or any
9:57
Speaker 1: other sort of body. It's just sort of sent out
9:58
Speaker 1: there to explore. And it's called pioneer because it really
10:02
Speaker 1: was a pioneering mission. It was the first thing from Earth,
10:05
Speaker 1: first scientific object sent out to explore the outer Solar System.
10:10
Speaker 1: It was the first man made object to go through
10:12
Speaker 1: the asteroid belt. For example, it was the first close
10:14
Speaker 1: flyby of Jupiter, Like the first close up pictures of
10:17
Speaker 1: Jupiter came from Pioneer. So when was it launched. It
10:21
Speaker 1: was a while ago, right, maybe older than us. It's
10:23
Speaker 1: been a nerd since longer than I have. Pioneer ten
10:26
Speaker 1: was launched in March of seventy two, and Pioneer eleven
10:29
Speaker 1: in April of seventy three. And you know, these were
10:32
Speaker 1: iconic missions. Before this, we didn't really know what things
10:35
Speaker 1: looked like out there. We had telescopes from Earth that
10:37
Speaker 1: were pretty good, I guess, nothing compared to what we
10:40
Speaker 1: have now. But if you call up in your mind
10:42
Speaker 1: an image of Jupiter, you probably have a pretty detailed
10:44
Speaker 1: image thanks to Hubble and thanks to all the spacecraft
10:47
Speaker 1: we sent to visit close up. But in the seventies,
10:50
Speaker 1: if you tried to do that, all you could have
10:51
Speaker 1: was like a blurry smear. We just didn't know in
10:54
Speaker 1: detail what these planets looked like until we went to
10:57
Speaker 1: visit them. So this was the first spacecraft to go
11:00
Speaker 1: and do that. Wow, even our telescopes couldn't get us
11:02
Speaker 1: a good picture. I mean they were all right, but
11:04
Speaker 1: nothing compared to what Pioneer could do. And it was
11:06
Speaker 1: an exciting moment even for the public. When these pictures
11:09
Speaker 1: started to come back. They had like a prime time
11:11
Speaker 1: television show to release these to the public, and people
11:14
Speaker 1: were glued to their screens. That TV show actually won
11:17
Speaker 1: an Emmy. Really, they had a whole show where they
11:19
Speaker 1: just revealed the photographs. Yeah, exactly. It was exciting. People
11:23
Speaker 1: wanted to know, so it was really popular. It was
11:26
Speaker 1: you know, back in the day, every sort of launch
11:28
Speaker 1: was a special moment, and these kind of pictures they
11:30
Speaker 1: were priceless. They still are now. Was it a daytime
11:33
Speaker 1: Emmy or a prime time Emmy? Those are two very
11:35
Speaker 1: different things. I think it was a prime time Emmy.
11:39
Speaker 1: That's the good one. Right, Well, it depends on you
11:41
Speaker 1: know what you're going for. So they launched a spacecraft
11:44
Speaker 1: in seventy two, and they launched like a brother, like
11:46
Speaker 1: a sibling sister spacecraft in the next year. Yeah, Pioneer
11:50
Speaker 1: ten went to visit Jupiter and then Pioneer eleven did
11:53
Speaker 1: Jupiter and Saturn, and this is the end of the series,
11:56
Speaker 1: like these are ten and eleven. There was Pioneer six,
11:58
Speaker 1: Pioneers seven, Pioneer eight, Pioneer line. Those are in sort
12:01
Speaker 1: of solar orbit there like experimental spacecraft to develop the technology.
12:05
Speaker 1: But these have all lasted for decades, Like we heard
12:08
Speaker 1: from Pioneer ten last in two thousand and three, which
12:12
Speaker 1: is like thirty years after we launched it. Wow. Now
12:16
Speaker 1: it's kind of weird because if you're like Pioneer number thirteen,
12:19
Speaker 1: are you still a pioneering the thirteen first want to
12:25
Speaker 1: do something? That's true? But Pioneer tend you know, it
12:29
Speaker 1: was the furthest object from humanity for a long time,
12:33
Speaker 1: and it was like the farthest humans have had an
12:35
Speaker 1: impact on the universe was Pioneer ten. More recently, we
12:39
Speaker 1: sent Voyager one, which was launched in seventy seven and
12:42
Speaker 1: it was going faster. So it's now the furthest object
12:46
Speaker 1: from humanity, even though it left later. Now paint the
12:48
Speaker 1: picture for us, what what do these spacecraft look like?
12:51
Speaker 1: They basically look like a big satellite dish, which is
12:55
Speaker 1: how they communicate back to us, and then there's like,
12:57
Speaker 1: you know, a cube of electronics strap to the back
13:00
Speaker 1: and that's where you have like instruments and you know,
13:03
Speaker 1: things that make measurements. This one has like a cosmic
13:06
Speaker 1: rate telescope on it, something to analyze plasma, something to
13:10
Speaker 1: analyze radiation. And then they've got a few things sticking
13:13
Speaker 1: off of them, like these big arms that stick off,
13:15
Speaker 1: and that's where the power sources are. For example, these
13:18
Speaker 1: things are powered by radiation. There's a radio isotope thermoelectric
13:24
Speaker 1: generator's plutonium in it, and it's basically just plutonium is
13:28
Speaker 1: decaying and that the energy from the decay turns into heat,
13:31
Speaker 1: which then they turn into electricity, and that powers this thing.
13:34
Speaker 1: It's like a plutonium battery. Well, it's a nuclear powered
13:38
Speaker 1: spacecraft basically, right, Yeah, how else could you power this thing?
13:41
Speaker 1: Solar panels wouldn't be effective after decades when you're so
13:44
Speaker 1: far from the Sun that it just looks like another star,
13:48
Speaker 1: and we couldn't charge up our batteries and send them
13:51
Speaker 1: out there. So really nuclear power is the only way
13:53
Speaker 1: to power these very very long lived spacecraft. All right.
13:56
Speaker 1: So we sent it out, and we sent it out
13:58
Speaker 1: to Jupiter and Saturn, and as something happened along the way,
14:03
Speaker 1: something weird happened. Yeah, the weird thing is that it
14:06
Speaker 1: wasn't flying the way that we thought it should. A
14:08
Speaker 1: Pioneer turns out to be sort of unexpectedly a really
14:11
Speaker 1: really sensitive instrument to measure gravitational pull of everything in
14:15
Speaker 1: the Solar System, and that's because it almost never fires
14:18
Speaker 1: its thrusters. It's just sort of like a ball we
14:21
Speaker 1: threw out into space. A lot of the other satellites
14:24
Speaker 1: that we send out there, like Voyager, it's got a
14:26
Speaker 1: bunch of thrusters and it's constantly firing them to change
14:28
Speaker 1: this direction. So it's hard to predict exactly where it
14:31
Speaker 1: should be. A Pioneer, it's just spin stabilized, and we
14:34
Speaker 1: just launched it out there, so we can use sort
14:36
Speaker 1: of Newton's theory of gravity and then Einstein's modification to
14:39
Speaker 1: predict exactly where it should be at any given moment.
14:42
Speaker 1: And when they measure to see where it actually was,
14:45
Speaker 1: it turns out it was kind of off course. Wait
14:47
Speaker 1: a minute. First of all, we just threw it out there.
14:50
Speaker 1: It doesn't have like, you know, a thrusters to steer
14:53
Speaker 1: it or to change its direction. It does have some
14:55
Speaker 1: small thrusters and a little bit of fuel but these
14:58
Speaker 1: are just in case it needs, of course correction. But yeah,
15:01
Speaker 1: unlike later, spacecraft is primarily just like a rock that
15:05
Speaker 1: we throw out into space. Now we keep it spinning
15:08
Speaker 1: a right that helps stabilize it to go in the
15:10
Speaker 1: right direction. But essentially we just toss it out there
15:12
Speaker 1: and then we just measure to see where it went,
15:15
Speaker 1: and that tells us something about like the gravity that
15:18
Speaker 1: experiences along the way. That's wow. And how do we
15:21
Speaker 1: know where it is? If we just throw it out
15:23
Speaker 1: on into space. It sends us messages and it answers messages,
15:27
Speaker 1: and we can tell how far away it is by
15:29
Speaker 1: how long those messages take to come back. And we
15:31
Speaker 1: can also tell how fast it's going by the Doppler
15:35
Speaker 1: shift of its messages. The faster it's going, the more
15:38
Speaker 1: the wavelength is change of the messages that return. So
15:41
Speaker 1: we have those two pieces of information, how far away
15:43
Speaker 1: it is and how fast it's going. And I guess
15:45
Speaker 1: we triangulate like if we've talked it one day and
15:48
Speaker 1: then we talked it the next month, and we can
15:49
Speaker 1: sort of as the Earth move, we can is that
15:51
Speaker 1: how we can tell where it is? Yeah, Also because
15:53
Speaker 1: we can tell where the signal is coming from right
15:55
Speaker 1: and located in the sky, and so we can tell
15:58
Speaker 1: where it is, how far way it is, and how
16:01
Speaker 1: fast it's moving, and then we compare that to like
16:03
Speaker 1: our model of where we think it should be. Are
16:05
Speaker 1: you want to keep up to date and like is
16:07
Speaker 1: this thing going in the right direction and isn't it
16:09
Speaker 1: a crash into Jupiter or just fly by? Right? All right?
16:12
Speaker 1: So then we threw this spacecraft into space and it
16:16
Speaker 1: didn't go where we thought it would, right, that's the anomaly.
16:19
Speaker 1: That's the anomaly. It was hundreds of kilometers off course.
16:23
Speaker 1: Something was pulling on this thing. It was slowing it
16:26
Speaker 1: down in a way that we did not understand. There's
16:29
Speaker 1: some small acceleration of this thing towards the Sun that
16:33
Speaker 1: didn't have an explanation from any known physics. Weird, hundreds
16:37
Speaker 1: of kilometers off course, that's that's not a little. It's
16:39
Speaker 1: not a little like if I if I missed an
16:42
Speaker 1: address by kilometers of being another state. Yeah, it's actually
16:47
Speaker 1: a really really tiny effect, but it adds up over
16:50
Speaker 1: the thousands and thousands kilometers of its journey. The effect
16:54
Speaker 1: of this force, this unexplained anomalous force, is ten billion
16:58
Speaker 1: times smaller then the acceleration we feel here on Earth
17:02
Speaker 1: from the gravitational pull of the Earth. So that's small
17:04
Speaker 1: effect really adds up over the lifetime the decades of
17:08
Speaker 1: this craft's flight to get it hundreds of kilometers off course,
17:12
Speaker 1: all right, And so and we knew one thing about it,
17:14
Speaker 1: which is that this mystery acceleration was directed towards the Sun.
17:19
Speaker 1: That's one clue. That's one clue. The other clue was
17:22
Speaker 1: that the same thing happened for Pioneer eleven wasn't just
17:26
Speaker 1: like some weird thing like, oh, maybe we shot Pioneer
17:28
Speaker 1: tan off in the wrong direction or make a mismeasurement
17:30
Speaker 1: early on, like the same thing happened to another spacecraft.
17:34
Speaker 1: I see, did it happen for Pioneer one through nine? Uh?
17:38
Speaker 1: Those guys didn't go out into the outer Solar System,
17:41
Speaker 1: so they didn't get a chance to probe that. I see.
17:43
Speaker 1: They weren't true pioneers. Yeah, And the Voyager missions which
17:46
Speaker 1: went out sort of in the same area, they had
17:48
Speaker 1: lots of complicated thrusters and were always doing these adjustments,
17:52
Speaker 1: and so they weren't nearly as precise probes of gravity.
17:55
Speaker 1: They weren't just like pure flying rocks. All right, so
17:57
Speaker 1: that's the Pioneer anomaly, the big mr. What was happening
18:00
Speaker 1: to the spacecraft that was steering them off course. So
18:03
Speaker 1: let's get into what could be possible explanations for this
18:07
Speaker 1: effect and also how it was possibly fixed. But first
18:12
Speaker 1: let's take a quick break. All right, we're talking about
18:27
Speaker 1: the Pioneer anomaly. These are spacecraft we launched in the
18:31
Speaker 1: seventies out towards Tupiter and Saturn, and they sort of
18:34
Speaker 1: got off course for some mysterious reason. Daniel, Um. These
18:39
Speaker 1: are spacecrafts that are still out there, right. They're gonna
18:42
Speaker 1: be out there for a long time. They're gonna be
18:43
Speaker 1: out there forever. They just keep going, right. There's nothing
18:46
Speaker 1: we can do to stop them or pull them back.
18:48
Speaker 1: They're just sort of headed out into the galaxy. They
18:51
Speaker 1: won't run out of batteries. They will run out of
18:53
Speaker 1: batteries eventually, you know, the half life of their plutonium
18:56
Speaker 1: batteries like eighty seven years, So it's gonna go for
18:59
Speaker 1: a while. But yeah, eventually it will run out of battery.
19:01
Speaker 1: But that's not going to stop it, right, It doesn't
19:03
Speaker 1: need battery to go. It just has its velocity and
19:05
Speaker 1: it just keeps flying. Oh wow, like basically too trash
19:09
Speaker 1: out into space. He'll be there forever. But we labeled
19:13
Speaker 1: our trash, right, we put our names on it. We
19:15
Speaker 1: said exactly who we are and what we're like found,
19:18
Speaker 1: come conquer us and us. This is reperiment on us. Yeah,
19:23
Speaker 1: it's commediently pointing towards us, right, yeah, exactly. And we
19:26
Speaker 1: put a plaque on it. We said exactly how to
19:28
Speaker 1: get to Earth. We put like a pulsar map, so
19:31
Speaker 1: if you knew where the pulsars were in the galaxy,
19:33
Speaker 1: you could exactly triangulate where our solar system was. We
19:36
Speaker 1: put a picture of humans on it. We even recorded
19:38
Speaker 1: some sounds from Earth and put it on there, as
19:41
Speaker 1: if like they would know how to play a record
19:43
Speaker 1: and know how to interpret that. So we threw these
19:46
Speaker 1: spacecraft out into the outer Solar system and they started
19:48
Speaker 1: veering off course for some mysterious reason. Now that people
19:53
Speaker 1: freak out or were they just sort of puzzled about
19:55
Speaker 1: this At first, they were just puzzled and they figured, well,
19:57
Speaker 1: we must have made a mistake somewhere, or there's tiny
20:00
Speaker 1: little effect that we hadn't accounted for, because you know,
20:03
Speaker 1: it's not just as simple as you toss a rock
20:06
Speaker 1: out into space and then you do gravitational calculations. There
20:09
Speaker 1: are lots of really small effects. You know. One set
20:12
Speaker 1: of small effects is like, well, there's a lot of
20:14
Speaker 1: different sources of gravity. It's not just the Sun that's
20:18
Speaker 1: pulling on these things, and it's all the planets and
20:20
Speaker 1: all the moons and all the rocks in the asteroid
20:23
Speaker 1: belt and all the tiny little things in the Kuiper Belt,
20:26
Speaker 1: and you know, even other stars provide tugs. So at
20:29
Speaker 1: first people thought, oh, we just haven't been as careful
20:31
Speaker 1: as we needed to to sort of tie up all
20:33
Speaker 1: the loose ends I see, like there could have been
20:35
Speaker 1: like it may be passed by a big asteroid that
20:38
Speaker 1: maybe pulled it off course or something. Yeah, or even
20:41
Speaker 1: simple things like maybe we're analyzing the data wrong, you know,
20:44
Speaker 1: we mismeasured it or misinterpreted this result or something like that. First,
20:49
Speaker 1: when you see something weird in your data, that's your
20:50
Speaker 1: assumption is that we messed up or we just weren't
20:53
Speaker 1: thorough enough. And the cool thing about pioneers that's very
20:56
Speaker 1: very precise data, and so it allows for really detailed tests,
21:00
Speaker 1: and so you can like go through your whole list
21:02
Speaker 1: of ideas for what could be affecting the flight of
21:04
Speaker 1: this thing, add them all up, and then compare them
21:06
Speaker 1: to the number. It's a really valuable way to check
21:09
Speaker 1: your understanding, right because I imagine you know, like you said,
21:12
Speaker 1: your first wish is that it's aliens. But I imagine
21:15
Speaker 1: you're also sort of afraid a little bit, like, oh
21:17
Speaker 1: my god, what if I made a mistake, Like what
21:19
Speaker 1: if I I am totally doing this where I have
21:23
Speaker 1: a typo in my formula or something. Right now, does
21:25
Speaker 1: that emotion also pass through you? I'm sure it does,
21:28
Speaker 1: you know. For those guys, you remember there was one
21:30
Speaker 1: Martian probe that crashed because somebody typed the number in
21:33
Speaker 1: in the wrong units, Like there was a European group,
21:36
Speaker 1: an American group, and somebody put something in in pounds
21:38
Speaker 1: and somebody else interpreted in kilograms and oops, and then
21:42
Speaker 1: the whole thing crashed and burned. So yeah, mistakes do happen, absolutely, Yeah,
21:47
Speaker 1: just don't work with those Americans and they're non international system.
21:53
Speaker 1: In my personal research, there's very little opportunity for aliens
21:56
Speaker 1: to affect our data. I mean, that would be pretty
21:58
Speaker 1: awesome if aliens change the collisions at the LHC and
22:02
Speaker 1: cause new weird stuff to happen as a way to communicate. Actually,
22:05
Speaker 1: that would be a pretty cool science fiction story, right,
22:08
Speaker 1: discovering aliens through particle collisions. Alien pranksters, alien physics pranksters.
22:15
Speaker 1: Exactly exactly, Aliens, if you're listening, I welcome that. Please
22:19
Speaker 1: mess with our data. It's the large age on coliders.
22:21
Speaker 1: Send us a message. The first physics from camm Alright, so,
22:26
Speaker 1: so what were some of the things that they thought
22:28
Speaker 1: could be happening here with the Pioneer anomaly. Well, the
22:31
Speaker 1: first thing that comes to mind is just the location
22:33
Speaker 1: of everything in the Solar System. So they went back,
22:35
Speaker 1: they did a really detailed check and they thought, for example, like,
22:38
Speaker 1: how well do we actually know the location of all
22:41
Speaker 1: the planets, you know, Earth and Jupiter and Saturn. If
22:45
Speaker 1: those are off by a little bit, could that explain
22:47
Speaker 1: you know, a little gravitational tug. And you know, we
22:50
Speaker 1: know these things really well because we've been watching these
22:53
Speaker 1: planets for a long time and they mostly just obayue gravity.
22:56
Speaker 1: So we have really really detailed models. We know the
22:58
Speaker 1: location these planets down to the meter, and these effects
23:01
Speaker 1: are just too small. So, like we think we know
23:04
Speaker 1: the gravity from all the planets and all the little
23:07
Speaker 1: things in the Solar system, there is uncertainly there, but
23:09
Speaker 1: it can't explain an effect of this size, all right,
23:12
Speaker 1: So it wasn't our measurement of the planets could be
23:16
Speaker 1: the measurement of you know, asteroids, because there is a
23:19
Speaker 1: lot of dark asteroids out there. There were some asteroids
23:21
Speaker 1: out there, but those are all really small. You know. Remember,
23:24
Speaker 1: gravity is really weak, and so to have any sort
23:27
Speaker 1: of effect, you either have to be large or you
23:29
Speaker 1: have to be close. So because the same thing happened
23:32
Speaker 1: to Pioneer eleven, we didn't think it was like a
23:35
Speaker 1: one off event that just like some object happened to
23:37
Speaker 1: get near one of these things. So it seemed like
23:40
Speaker 1: it had to be some sort of more systemic thing.
23:43
Speaker 1: Another thing people thought about is like, well, what about
23:45
Speaker 1: the solar wind? Right, the Sun is pushing on things,
23:48
Speaker 1: It's not just tugging on them with gravity is actually
23:50
Speaker 1: pushing on everything. You know, it's sending out streams of particles.
23:53
Speaker 1: You could use that as a solar sales and navigate
23:55
Speaker 1: the Solar system. So if you're like hunting down for
23:58
Speaker 1: tiny little effects. You might want to consider the effects
24:01
Speaker 1: of the photons and the protons and the electrons that
24:03
Speaker 1: the Sun is streaming out right, but the solar wind
24:06
Speaker 1: is pushing things up. But here something was kind of
24:09
Speaker 1: pulling the spacecraft towards the Sun right exactly, So it's
24:13
Speaker 1: the wrong direction. If anything, you would expect the solar
24:15
Speaker 1: wind to accelerate it, to push it further out into
24:18
Speaker 1: the Solar system, making go faster. So we needed some
24:21
Speaker 1: other effects, something that was tugging it back into the
24:23
Speaker 1: Solar system. And so this long list of basic checks
24:26
Speaker 1: were done, and none of them could explain what was
24:29
Speaker 1: going on. None of them are sort of strong enough
24:31
Speaker 1: to account for the deviations of hundreds of kilometers, So
24:35
Speaker 1: it wasn't the basic stuff. Then that's when people started
24:38
Speaker 1: to get creative. I imagine, Yeah, they started to get creative.
24:40
Speaker 1: They thought, well, what if there's something else on the
24:43
Speaker 1: spacecraft that's basically giving it a little push. You know
24:47
Speaker 1: what if there's like effectively a thruster, Because think about
24:50
Speaker 1: the batteries on these spacecraft. These things generate heat, and
24:53
Speaker 1: things that are hot radiate photons, and when you radiate
24:56
Speaker 1: a photon, you're basically getting pushed. You know, you shoot
25:00
Speaker 1: off a photon to the left, then by conservation momentum,
25:03
Speaker 1: you're going to the right, and everybody, everything that is
25:06
Speaker 1: hot is giving off photons. Like me and you, we
25:09
Speaker 1: glow in the infrared. Right, you put on night vision
25:12
Speaker 1: goggles like the Predator, you can see a human body
25:15
Speaker 1: because it's giving off in for a red photon. I
25:17
Speaker 1: knew you would work in aliens somehow. Wait does that mean?
25:22
Speaker 1: Like if I put a flashlight out into space and
25:25
Speaker 1: turn it on, it would start to go like it
25:28
Speaker 1: would basically act like a rocket. Yes, a flashlight is
25:31
Speaker 1: a rocket, absolutely. It throws particles out the back, and
25:34
Speaker 1: so it has to go the other direction. Now, if
25:37
Speaker 1: you put two flashlights shining in the opposite directions, it
25:39
Speaker 1: won't go anywhere. They'll balance each other. So the pioneer
25:43
Speaker 1: people thought, well, it's got these things on it, but
25:45
Speaker 1: they glow in every direction, right, and so if heat
25:48
Speaker 1: is the same everywhere in the spacecraft, that's not going
25:50
Speaker 1: to effectively give it a push. When did? It depends
25:53
Speaker 1: on the shape, Like a hot sphere would give up
25:55
Speaker 1: photons in all directions, But maybe, like I don't know,
25:58
Speaker 1: like it's something it looks like a dish might not. No,
26:00
Speaker 1: you're right, and it's a really interesting clue. And people
26:02
Speaker 1: thought for a while about this, like maybe the complicated
26:05
Speaker 1: shape of the spacecraft is not giving off heat in
26:07
Speaker 1: the same direction everywhere. But there was another important clue,
26:11
Speaker 1: which was that this effect wasn't dropping as a function
26:14
Speaker 1: of time, like it wasn't fading. And we know the
26:16
Speaker 1: heat from these batteries should be fading, like this is
26:19
Speaker 1: a radioactive thing. It decays over the half life of
26:22
Speaker 1: eighty seven years. These things eventually cool and then just
26:25
Speaker 1: become dead. And so if it's due to the heat
26:28
Speaker 1: of the batteries, you would expect this thing to fade
26:31
Speaker 1: with time. But the data we had showed that it
26:33
Speaker 1: was constant. So people thought, well, can't be the batteries.
26:36
Speaker 1: I see, it wasn't cool enough. It wasn't getting cool alright,
26:40
Speaker 1: So then what else did did they think it could be?
26:42
Speaker 1: So that's when he got exciting. They thought, well, we
26:45
Speaker 1: can't explain this using any sort of known physics, any
26:48
Speaker 1: solar wind or any gravity or any heating of the spacecraft,
26:51
Speaker 1: so let's get creative. And people thought, well, maybe we've
26:55
Speaker 1: accidentally created something which measures like the expansion of the universe,
27:00
Speaker 1: because they thought maybe space is expanding inside the Solar
27:04
Speaker 1: System and it creates this weird gravitational potential. And we
27:08
Speaker 1: know that gravity and time are connected because, for example,
27:12
Speaker 1: if you go near a black hole, time slows down
27:16
Speaker 1: for you. So over vast stretches of space, potentially time
27:21
Speaker 1: is getting slowed down as you move through these like
27:24
Speaker 1: expanded space. Whereas our clocks, the ones that we're using
27:28
Speaker 1: to sort of predict where this thing goes, these really
27:31
Speaker 1: precise atomic clocks basically assume that space is flat. So
27:35
Speaker 1: if we're measuring time differently than something that's flying out
27:39
Speaker 1: into the Solar System, then maybe that could explain it,
27:43
Speaker 1: meaning like maybe the clock on the spacecraft is wrong
27:47
Speaker 1: or do you mean like it's actually in a different time,
27:49
Speaker 1: it's actually in a different time. Yeah, this falls under
27:52
Speaker 1: this whole set of ideas like the non uniformity of time, right,
27:56
Speaker 1: And we've talked a lot in the podcast about how
27:58
Speaker 1: my clock and your clock can disagree but both be
28:01
Speaker 1: correct because there is no universal sense of time. So
28:05
Speaker 1: this is an idea sort of along that direction, like
28:08
Speaker 1: maybe we're measuring the expansion of space and those gravitational
28:11
Speaker 1: effects are distorting the clock on the spacecraft, not that
28:14
Speaker 1: it's wrong, but you know it's different. It's just differently timed.
28:17
Speaker 1: I see. So maybe the idea is that maybe it
28:20
Speaker 1: is it was supposed to be, but our measurement of
28:22
Speaker 1: where it is is wrong because the timing in the
28:26
Speaker 1: clock on board is different than it we think it
28:29
Speaker 1: should be. And that was so the general concept like
28:32
Speaker 1: maybe something in this direction will help us because we
28:34
Speaker 1: know gravity and time are connected. But they couldn't actually
28:37
Speaker 1: make it work. They try to get the map all
28:39
Speaker 1: work out and say, is this consistent with general relativity?
28:42
Speaker 1: What we know about the expansion in the universe? Would
28:44
Speaker 1: that explain that? And it could never be made consistent,
28:47
Speaker 1: and so it would have to be like some weird
28:50
Speaker 1: deviation have to be some special case of how times
28:53
Speaker 1: affected by gravity for some reason only in our solar system.
28:57
Speaker 1: And so you know, when you start to develop like
28:58
Speaker 1: a new idea of for how to explain some weird science,
29:01
Speaker 1: you want as simple a new idea as possible. You
29:04
Speaker 1: don't want to have to like add all sorts of
29:05
Speaker 1: weird bells and whistles and exceptions and stuff. And so
29:08
Speaker 1: this started off sort of promising and then ended up
29:11
Speaker 1: being like, it doesn't really fit. It wasn't just that
29:14
Speaker 1: they it was in the wrong time zone or daylight savings.
29:17
Speaker 1: That couldn't explain it either. No, I mean I make
29:21
Speaker 1: that mistake all the time, and they usually blame it
29:23
Speaker 1: on aliens, which is why I miss a meeting. But no,
29:26
Speaker 1: they couldn't explain this using any sort of general relativistic
29:29
Speaker 1: effects on the clock or even simple modifications to general
29:33
Speaker 1: relativity to allow for effects on the clock of the
29:36
Speaker 1: expanding space in the Solar System. So that didn't work out.
29:39
Speaker 1: You can't blame the engineers, and you can't blame Einstein
29:43
Speaker 1: or general relativity. What else could it have been. Well,
29:47
Speaker 1: people got excited for a while when they thought maybe
29:49
Speaker 1: it was dark matter. Right, we've accounted for the gravitational
29:53
Speaker 1: sources that we know about the planets and the rocks
29:56
Speaker 1: and the Sun, But we also know that most of
29:59
Speaker 1: the gravity in the Unit verse isn't from the stuff
30:01
Speaker 1: that we can see. It's actually from this weird invisible matter.
30:05
Speaker 1: We still won't understand that's everywhere, and we think that
30:08
Speaker 1: it fills the galaxy. In fact extends beyond the galaxy
30:12
Speaker 1: and it's five times as much of it as there
30:14
Speaker 1: is normal matters. So if you're studying details of gravitational effects,
30:18
Speaker 1: you might expect to have to take into account the
30:20
Speaker 1: dark matter. Interesting. Yeah, like our solar system could be
30:24
Speaker 1: or is probably bated in dark matter, right, that could
30:27
Speaker 1: potentially affect the gravity of things we send out into space. Absolutely,
30:31
Speaker 1: dark matter definitely is here. It's everywhere. It's all around us.
30:35
Speaker 1: There's dark matter with us in this room, the dark
30:37
Speaker 1: matter all around the Earth. We can't see it or
30:40
Speaker 1: detective because we think it only has a gravitational interaction.
30:43
Speaker 1: And remember gravity is super duper weak, so usually we're
30:46
Speaker 1: only sensitive to dark matter if there are huge amounts
30:49
Speaker 1: of it, you know, like galaxy sized amounts to affect
30:52
Speaker 1: how the galaxy spins. It's really hard to detect like
30:55
Speaker 1: local blobs of dark matter. So people got excited when
30:58
Speaker 1: they thought maybe Pioneer ten and eleven are like a
31:01
Speaker 1: local prob they're telling us how much dark matter there
31:03
Speaker 1: is here. Interesting, But wouldn't if there was some anomaly
31:06
Speaker 1: in dark matter, wouldn't it affect all the other planets too? Yeah, exactly,
31:10
Speaker 1: it would. And we also don't think that there is
31:13
Speaker 1: that much dark matter. We know that there's five times
31:16
Speaker 1: as much dark matter in general in the universe, but
31:19
Speaker 1: we don't think in our Solar System there's that much
31:22
Speaker 1: because doesn't clump up we think the way normal matter does.
31:25
Speaker 1: Like if you took the normal matter in the galaxy
31:27
Speaker 1: and just spread it out throughout the whole volume of
31:30
Speaker 1: the galaxy, it would be pretty thin. That's the way
31:32
Speaker 1: dark matter is. There's five times as much of it,
31:34
Speaker 1: but it's much more spread out than normal matter is.
31:37
Speaker 1: So sort of in the volume of the Solar System,
31:41
Speaker 1: it's like one million of the mass of the Sun
31:44
Speaker 1: of dark matter, right, see, So it couldn't be that either.
31:47
Speaker 1: So then they couldn't blame it on a technical issue
31:50
Speaker 1: or sort of a theoretical issue, And so it was
31:53
Speaker 1: a big mystery, I mean for decades, right, Like they've
31:56
Speaker 1: seen this anomaly for you know, a thirty almost forty years. Yeah,
32:01
Speaker 1: people really worked on it for a long time, and
32:02
Speaker 1: it was in the nineties of people that is really
32:05
Speaker 1: detailed investigation went through all these possible explanations and couldn't
32:09
Speaker 1: explain it, And then people had a lot of fun
32:11
Speaker 1: coming up with theories of new physics to try to
32:14
Speaker 1: explain it potentially, and it's sort of like a standing
32:17
Speaker 1: question in science for quite a while. People even try
32:20
Speaker 1: to explain it using like weird modified gravity, like maybe
32:24
Speaker 1: gravity doesn't work the way Einstein and Newton thought we did,
32:27
Speaker 1: and somehow gravity changes when you get out into the
32:29
Speaker 1: outer Solar system. But you know, that doesn't really make
32:32
Speaker 1: sense because we understand how Pluto and Neptune and Neurinus operate.
32:36
Speaker 1: So there are a lot of questions about what could
32:39
Speaker 1: explain this on a lot of crazy ideas thought up
32:42
Speaker 1: to explain it, none of which were ever really very
32:44
Speaker 1: compelling or which worked. So it's sort of a question like,
32:47
Speaker 1: are we gonna find some boring explanation for what this is?
32:50
Speaker 1: Or is somebody going to come up with a new
32:52
Speaker 1: idea that actually, you know, makes it all click together
32:54
Speaker 1: and tells us something new and deep about the universe? Right?
32:57
Speaker 1: Are you going to get a try again when you
32:59
Speaker 1: scratch out the start of it? Or are you gonna
33:00
Speaker 1: win a million aliens in the process. All right, Well,
33:04
Speaker 1: let's get into how this mystery was finally resolved, if
33:08
Speaker 1: it was resolved at all. But first let's take a
33:11
Speaker 1: quick break. All right, So the Pioneer anomaly was a
33:28
Speaker 1: big mystery for decades back in the seventies, eighties, and nineties,
33:32
Speaker 1: spacecraft we throughout their into space. We're veering off course, Daniel,
33:36
Speaker 1: How was it all resolved in the end. If it
33:39
Speaker 1: was so, we actually do think we have a pretty
33:42
Speaker 1: good understanding of what happened by now, and it's due
33:44
Speaker 1: to some sort of like data archaeology by some researchers
33:49
Speaker 1: really dedicated, really interested in understanding how this worked. They
33:52
Speaker 1: went and found some old data in the mid two
33:54
Speaker 1: thousand's and did a really detailed study and they think
33:57
Speaker 1: they've cracked it. Oh wow, in the mid to of thousands.
34:00
Speaker 1: So all this time, since the seventies, these space crafts
34:03
Speaker 1: were out there off course and people just sort of
34:06
Speaker 1: shrugged it off for a while, or that they just
34:08
Speaker 1: gave up, or or what. Well, you know, when there
34:10
Speaker 1: are these puzzles in science, it's not always easy to
34:13
Speaker 1: know how to crack them, and so sometimes they'll be
34:15
Speaker 1: out there for a long time, decades even people like,
34:18
Speaker 1: well that's not understood, but nobody really knows what to
34:21
Speaker 1: do about it. So finally somebody said, well, I'm gonna
34:24
Speaker 1: try to go back and find some more data, dig
34:27
Speaker 1: out some mold data nobody's ever seen before, and make
34:29
Speaker 1: a more detailed study than anybody's ever done before, and
34:32
Speaker 1: maybe we'll figure it out. Wow, that's wild to me, Like,
34:35
Speaker 1: how do you sleep at night? Like, let's say you're
34:37
Speaker 1: the scientists or the engineer who worked on this, Like,
34:39
Speaker 1: how do you ever be at peace? You know, It's
34:41
Speaker 1: like if somebody told you, hey, I know it's your
34:44
Speaker 1: car mysteriously moves an inch every night, and you're like, well,
34:48
Speaker 1: I don't know, how could you get to sleep? I
34:51
Speaker 1: think that's why smart scientists have great ideas in the
34:53
Speaker 1: middle of the night, because their brains are always working
34:56
Speaker 1: on these things, are always chewing away on these puzzles
34:59
Speaker 1: and these questions. All right. So then in the two thousands, UM,
35:03
Speaker 1: a group of people said, hey, we want to figure
35:05
Speaker 1: this out. So they say, sort of dug through all
35:08
Speaker 1: the old data. But that was kind of hard, right,
35:10
Speaker 1: because this is data from the seventies. Yeah, they literally
35:13
Speaker 1: dug through old data and they were specifically focused on
35:16
Speaker 1: this question of the heat from the batteries and whether
35:19
Speaker 1: or not it really was decaying over time. And what
35:22
Speaker 1: they discovered is that we didn't actually have all the data.
35:25
Speaker 1: Some of the earliest data from the spacecraft was like
35:28
Speaker 1: stored on magnetic tapes and not really included in most
35:32
Speaker 1: later analyzes because it was kind of a pain to
35:33
Speaker 1: go and find it and recover it and process it
35:36
Speaker 1: and stuff. So they did a bit of like archaeology,
35:39
Speaker 1: and they found more than a dozen boxes of magnetic
35:42
Speaker 1: tapes stored under a staircase at JPL in Pasadena, and
35:46
Speaker 1: they worked with like an old school programmer to create
35:49
Speaker 1: software that could read these tapes and clean it up.
35:52
Speaker 1: So they got sort of a longer time series on
35:55
Speaker 1: the data than anybody else had, like data on what
35:58
Speaker 1: the position of it, or like the signals we were
36:00
Speaker 1: getting from it, or what on the position of it is,
36:03
Speaker 1: specifically the earlier positions. Remember we talked about how we
36:07
Speaker 1: didn't think it was just heat coming off the spacecraft
36:09
Speaker 1: unevenly because it would have faded with time, and it
36:13
Speaker 1: didn't look like it was fading with time. So to
36:15
Speaker 1: trying to answer that question in more detail, they said, well,
36:17
Speaker 1: let's look at earlier data data when it had just
36:20
Speaker 1: left the Earth to see if we can spot this
36:22
Speaker 1: effect earlier on. I see, you're looking for a weird
36:26
Speaker 1: effect on where you think it should be different from
36:28
Speaker 1: when then we're where it is, right, yeah, exactly. So
36:32
Speaker 1: you're you're basically comparing curves. Right, you have the curve
36:35
Speaker 1: of what you expect and the curve of where it
36:36
Speaker 1: actually was. And now you're trying to come up with
36:39
Speaker 1: a new expectation, like can we tweak how we understand
36:42
Speaker 1: this thing flies so that what we expect matches what
36:45
Speaker 1: we observe. And you also have to sort of look
36:47
Speaker 1: back in time in the Solar system, right, like in
36:49
Speaker 1: this back then, what where were all the planets and
36:52
Speaker 1: asteroids and all that in order to think about where
36:55
Speaker 1: it should have been exactly. It's a complicated calculation, and
36:58
Speaker 1: to do this right you need to know not just
37:01
Speaker 1: where it was, but you also need to know, as
37:02
Speaker 1: you were saying, where it's giving off heat. Like the
37:05
Speaker 1: shape of this thing really affects how it glows, because,
37:09
Speaker 1: as we're talking about before, it's not just a sphere, right.
37:12
Speaker 1: Physicists always like to assume everything is a spear at
37:14
Speaker 1: first order, but the details matter when you're making really
37:18
Speaker 1: really precise measurements. And this thing has two big hot
37:22
Speaker 1: batteries on one side, and then like a cool dish
37:25
Speaker 1: on the other side. But it also has a bunch
37:27
Speaker 1: of instruments that use that electricity, and so as they
37:30
Speaker 1: draw current, they get hot, and as the heat up,
37:32
Speaker 1: they glow, and these kind of effects. Is just the
37:35
Speaker 1: glowing heat from these things is big enough to explain
37:37
Speaker 1: the effect that we're seeing. Yeah, and I think you know,
37:40
Speaker 1: you say batteries and that makes me think of, you know,
37:42
Speaker 1: like as a battery or a car battery. But really
37:46
Speaker 1: these are like nuclear reactors right there their generators, Yeah, exactly,
37:50
Speaker 1: they're not fission or fusion. They're just sort of like
37:53
Speaker 1: slow rolling radioactive to k that generates the electricity. But yeah,
37:57
Speaker 1: they are nuclear reactors. But also everything on the space
38:00
Speaker 1: scrapt that he uses that electricity eventually leaks some of
38:03
Speaker 1: that energy. Nothing is perfect, right, and it leaks that
38:05
Speaker 1: energy into heat, just the same way everything that you
38:08
Speaker 1: use as electronics in it will eventually heat up. Your
38:10
Speaker 1: computer heats up as you use it. Right, there's no
38:13
Speaker 1: like fire burning inside your computer. It's just inefficiency from
38:17
Speaker 1: the use of electricity. So if you have an object
38:19
Speaker 1: on a spacecraft that's drawing electricity, not even just the batteries,
38:23
Speaker 1: but the equipment on the spacecraft gets hot as it
38:26
Speaker 1: uses the electricity. To understand the effect of all this stuff,
38:29
Speaker 1: you need to know like exactly where everything was on
38:32
Speaker 1: the spacecraft and how hot it got. These days, we
38:35
Speaker 1: can do that pretty well. We have like really fancy
38:37
Speaker 1: software to model this kind of stuff, but you know,
38:40
Speaker 1: we don't have the records that match that software from
38:43
Speaker 1: a really really old instrument, Like this thing was built
38:46
Speaker 1: forty years ago. You know, we have like blue plants
38:50
Speaker 1: drawn by hand by the original designers. So these researchers
38:54
Speaker 1: had to go in and build a model of the
38:56
Speaker 1: sort of heat flow of Pioneer spacecraft by hand like later.
39:01
Speaker 1: And it's involved like fifteen thousand individual pieces like exactly
39:06
Speaker 1: where this cable goes and exactly how thick that piece
39:09
Speaker 1: of aluminum it was, and like this is a huge effort. Wow.
39:12
Speaker 1: So yeah, they had to basically create a virtual model
39:15
Speaker 1: of the spacecraft and then put it out into space
39:18
Speaker 1: with the heat source and see if it would deviate
39:21
Speaker 1: the way that we they were seeing in the data.
39:24
Speaker 1: It's really incredible precision. You know. Think about like when
39:26
Speaker 1: you drive your car, do you expect your car to
39:28
Speaker 1: slow down when you turn the headlights on right. You
39:31
Speaker 1: don't expect it to, but actually it does. Right. Turning
39:34
Speaker 1: on the headlights slows down your car because you're basically
39:37
Speaker 1: shooting photons away from your car. So this is the
39:40
Speaker 1: kind of effect that we're looking for. It's amazing that
39:43
Speaker 1: it actually happens and they were able to figure it out.
39:46
Speaker 1: So now they're calculations, which include more time information and
39:50
Speaker 1: a much more detailed model of the spacecraft actually match
39:54
Speaker 1: really well what we see. So they think they solved
39:57
Speaker 1: the mystery. They think they've solved the mystery. Turns out
40:00
Speaker 1: it was the plutonium in the power source next to
40:03
Speaker 1: Saturn exactly. It's just uneven heating right eventually over many years.
40:08
Speaker 1: The fact that one side of this thing is hotter
40:10
Speaker 1: than the other means that it gave off more photons,
40:13
Speaker 1: which gave it a little bit of a push. It's
40:15
Speaker 1: like if you had two flashlights out in space and
40:17
Speaker 1: one of them was a teensy bit brighter than the
40:19
Speaker 1: other one, you would get pushed away from that flashlight,
40:23
Speaker 1: tiny little bit. And that explains why it was being
40:27
Speaker 1: pulled towards the Sun. Because you know that the way
40:31
Speaker 1: this basecraft is designed, you know you always want to
40:33
Speaker 1: point the dish back towards Earth kind of right, And
40:36
Speaker 1: so that means that the hot stuff is sort of
40:39
Speaker 1: in front of you, which was slowing it down. M Yeah,
40:42
Speaker 1: we're pointing the hot bits of this thing out towards
40:45
Speaker 1: the Aliens and the cold side back towards Earth. So yeah,
40:48
Speaker 1: that effectively slows it down a tiny little bit. I
40:50
Speaker 1: guess the lesson is, you know, it's always better to
40:52
Speaker 1: have a hot back end. I'm not going to touch
40:55
Speaker 1: that at all, but Pioneer eleven apparently had the same
40:58
Speaker 1: hot back end, and that's why the same thing happened
41:01
Speaker 1: to Pioneer eleven. The story all sort of fits together
41:04
Speaker 1: and makes sense. And I love these sort of science
41:06
Speaker 1: stories when it all this clicks together and the explanation
41:10
Speaker 1: matches the data and it all just sort of works.
41:12
Speaker 1: It's like, man, math is correct, physics works, the universe
41:16
Speaker 1: actually makes sense. It's incredible. I guess you're simultaneously impressed
41:21
Speaker 1: by yourselves but also disappointed that you're so good at
41:24
Speaker 1: figuring out the universe. Kind of yeah, it's not as
41:27
Speaker 1: exciting an explanation is like we discovered a new way
41:30
Speaker 1: that time flows, or gravity is broken, or something like that,
41:34
Speaker 1: or we have a clump of hidden dark matter in
41:36
Speaker 1: the Solar System that would be more exciting, but you
41:39
Speaker 1: never know, Like science is about exploration, which means you
41:43
Speaker 1: never know what you're gonna find. Usually it's boring dust
41:46
Speaker 1: and rubble, but sometimes sometimes it's a real diamond, it's
41:49
Speaker 1: a gem, something that gives you a clue about the
41:52
Speaker 1: nature of reality, and you never know, which is why
41:54
Speaker 1: you just gotta keep scratching, all right. So then this
41:56
Speaker 1: is sort of in the community, this is the most
41:59
Speaker 1: accepted explain aation of what happened. Like everyone feels like,
42:01
Speaker 1: all right, these researchers totally nailed it, they totally explains it,
42:05
Speaker 1: or is there still some sort of uncertainty about it both.
42:08
Speaker 1: I think people accept this as an explanation for what
42:12
Speaker 1: happened to Pioneer ten and Pioneer eleven, So that sort
42:14
Speaker 1: of anomaly has been solved, but there are still plenty
42:18
Speaker 1: of anomalies and how spacecraft moved, not just Pioneer ten
42:21
Speaker 1: and Pioneer eleven, but every spacecraft that does one of
42:24
Speaker 1: these sort of gravitational slingshots ends up going off in
42:27
Speaker 1: the direction that we don't quite understand. This is called
42:31
Speaker 1: the fly by anomally. Basically, every time one of these
42:34
Speaker 1: things happens, it doesn't quite work out the way we
42:37
Speaker 1: expect and nobody really understands it. So there's a long
42:40
Speaker 1: list of things we don't understand about how things move
42:43
Speaker 1: into Solar system. Even though as basic as just like
42:46
Speaker 1: gravitational mechanics about things moving in the Solar System, still
42:49
Speaker 1: have questions that need to be answered, right, which is
42:52
Speaker 1: all the more impressive that they can. I'm gonna say
42:55
Speaker 1: we because this is a good thing, So I'm gonna
42:57
Speaker 1: play the royal we here. We can like land spacecraft
43:01
Speaker 1: in Mars right and like know exactly where it's going
43:03
Speaker 1: to land on the planet. That's that's so amazing. It's
43:05
Speaker 1: really incredible what we the scientists and engineers have accomplished.
43:09
Speaker 1: It's too bad what they messed up on. All right, Well,
43:14
Speaker 1: that's the pioneer anomaly, and I guess we can reclassify
43:17
Speaker 1: it now, Daniel as a pioneer nomally, or the pioneer
43:22
Speaker 1: story or the high precision test of science, that is
43:27
Speaker 1: the pioneer spacecraft. That's not as catchy, but maybe more accurate. Again,
43:33
Speaker 1: another reminder of how you know vast space is I mean,
43:37
Speaker 1: this thing is still within our backyard, just the solar SYSM.
43:40
Speaker 1: And even even then, these distances are huge and there's
43:43
Speaker 1: a lot that can happen out there when you go
43:45
Speaker 1: out into deep space. Yeah, Pioneer ten is more than
43:48
Speaker 1: twelve billion kilometers from Earth. It's tens of light hours
43:53
Speaker 1: from Earth and moving away really really fast. It's destined
43:56
Speaker 1: to reach another star system in about two million years.
43:59
Speaker 1: That's sixty seven light years from here. So maybe in
44:03
Speaker 1: two million and sixty seven years we'll get a message
44:06
Speaker 1: back from the aliens saying thanks for your garbage, Thanks
44:09
Speaker 1: for your garbage. With the hot front end, back end,
44:15
Speaker 1: it's a hot back end. Let leave, we turn it
44:18
Speaker 1: around and let's see if we can turn this around,
44:20
Speaker 1: and we'll back into this cultural misunderstanding with the aliens.
44:23
Speaker 1: All right, Well, we hope you enjoyed that. Thanks for
44:26
Speaker 1: joining us, see you next time. Thanks for listening, and
44:36
Speaker 1: remember that Daniel and Jorge explained. The Universe is a
44:39
Speaker 1: production of I Heart Radio or more podcast from my
44:42
Speaker 1: Heart Radio, visit the I heart Radio app, Apple Podcasts,
44:46
Speaker 1: or wherever you listen to your favorite shows. Yeah,