Can We Stop an Asteroid? The Physics Behind NASA’s DART Mission (EP. 30)

Hosted by Lester Nare and Krishna Choudhary, this episode is a full deep dive on planetary defense. We break down NASA’s DART mission, why the goal was never to “blow up” an asteroid but to gently nudge it, and why the newest result is even bigger than the original headline: scientists can now directly detect that the Didymos–Dimorphos system changed not just locally, but in its heliocentric path around the Sun. Summary DART actually worked — not just by shortening Dimorphos’s local orbit around Didymos by 33 minutes, but by measurably changing the motion of the whole binary system around the Sun. Planetary defense is a measurement problem — the new result hinges on detecting a velocity shift of just 11 microns per second in an asteroid system moving tens of kilometers per second. Why ejecta matters — the impact transferred more momentum than the spacecraft carried in, thanks to debris blasting off the asteroid and boosting the total deflection. Why this matters for Earth — for the first time in our planet’s history, life on Earth may actually have the tools to alter its own cosmic fate. Support the show Donate: FFPod.com/donate Follow: @FFPod on X / Instagram / TikTok / Facebook Chapters 00:00 New single-story format 01:53 DART mission setup 18:26 Why the binary asteroid system matters 31:36 Measuring the heliocentric deflection 46:28 Planetary defense implications 53:37 Outro Show Notes DART heliocentric deflection result — Science Advances NASA DART mission overview ESA HERA mission

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Lester Nare?

  Hello, Internet. This is your captain speaking, Lester Nare, joined as always by my co-host and our resident PhD, Krishna Choudhary. Today, we have a wonderful episode. We're going to do a story, a research paper on planetary defense, covering one of NASA's most audacious missions, the DART mission. Spoiler alert, it worked. But where it gets interesting is in the how and the why. And we're going to take a quick pause here to talk about a slight change to the programming. For many of you who have been listening to us for quite some time, you know that we do weekly episodes, and the demand has just been insane for us to do more.

• 0:45Lester Nare?

  So what we're going to try out here is actually doing multiple episodes a week, but having our episodes be focused on a single story. So today, we're going to just be focused on the DART mission with planetary defense. But you will see our faces two more times this week with a follow-up story, and we will have the rundown be its own episode type. And I have some ideas about some game show elements to test our resident PhD. As always, we are going to learn about the science from the ground up today, because this is From First Principles.

• 1:35Krishna Choudhary?

  So if there is an asteroid coming to Earth.

• 1:39Lester Nare?

  Yes.

• 1:39Krishna Choudhary?

  I would like to not die.

• 1:42Lester Nare?

  Armageddon, Deep Impact?

• 1:44Krishna Choudhary?

  Yeah, all of these, I would like that not to happen.

• 1:47Lester Nare?

  Yes.

• 1:47Krishna Choudhary?

  Okay. And it turns out the best way to... Have that happen is actually not to like blow it up, but to just gently nudge it out of the way gently because you know it's a giant asteroid. You gotta get a little aggressive because it's a giant asteroid, but at the end of the day, all we have to do is gently nudge it out of the way and maybe it'll avoid Earth. Okay? And the first time that this happened was on September 26th, 2022. This was NASA's double asteroid redirection test. I was watching it live. This was the DART mission. It collided with a moonlit of a two asteroid system.

• 2:26Lester Nare?

  Okay.

• 2:27Krishna Choudhary?

  And I remember watching it live. You could literally see there was a, there was a little satellite that acted like a projectile, like a missile, and it had a camera on it and it was taking a photo of the moon as it was getting closer and closer and closer. And when it finally hit, the other satellite took photos of it. It hit this moon at 14,000 miles per hour, which is about six kilometers per second. And the key result that we got immediately was that the orbit of this moonlit, the name was Dimorphos, orbiting around Didymos. The orbit of that moon around the main big asteroid had reduced by 33 minutes.

• 3:10Lester Nare?

  Okay.

• 3:10Krishna Choudhary?

  So it went from something like 12 hours to 11 and a half hours.

• 3:14Lester Nare?

  So the contact changed the trajectory, the path that this two moonlit system was traveling on.

• 3:22Krishna Choudhary?

  Yeah, but so the contact changed the orbit of the two moonlit system.

• 3:27Lester Nare?

  The orbit.

• 3:28Krishna Choudhary?

  That's what we could confirm.

• 3:29Lester Nare?

  Okay.

• 3:30Krishna Choudhary?

  What you're saying is what this paper is about.

• 3:32Lester Nare?

  I see.

• 3:33Krishna Choudhary?

  Okay, which is I, I, I ran into the moon and now the orbit has changed.

• 3:38Lester Nare?

  Yes.

• 3:39Krishna Choudhary?

  But what does that do for how this moon, this, this two asteroid system goes around Earth?

• 3:44Lester Nare?

  Because the orbit you're talking about is locally.

• 3:47Krishna Choudhary?

  Yes, exactly. And, and getting that signal is super easy. 30 minutes less than 12 hours. That's what something like a little bit less than like 5%, right? That's a change that is doable, like pretty immediately, especially because we've got the DART mission in that asteroid system that's like monitoring

• 4:05Lester Nare?

  Right.

• 4:06Krishna Choudhary?

  the two going around, right? So getting that data is very quick, happened in 2022. We got that confirmation like within, I think like a month.

• 4:14Lester Nare?

  Okay.

• 4:14Krishna Choudhary?

  Okay. This is now, what, four years later?

• 4:17Lester Nare?

  Yes.

• 4:17Krishna Choudhary?

  Three and a half years later. And now we have a paper that's out in Science Advances, and it confirms that there's a measurable change in the very center of that two-moon system going around the sun.

• 4:30Lester Nare?

  Hmm.

• 4:31Krishna Choudhary?

  Meaning, those two asteroids now have a different orbit around the sun itself because of that crash on its moon. Does that make sense?

• 4:39Lester Nare?

  It makes total sense, and I want to briefly talk about why the implications of something like this are so historical.

• 4:46Krishna Choudhary?

  Hmm.

• 4:47Lester Nare?

  You know, Earth has been around for four billion

• 4:50Krishna Choudhary?

  Yep.

• 4:51Lester Nare?

  years. Life on Earth has been around for hundreds of millions of years.

• 4:55Krishna Choudhary?

  Yep.

• 4:55Lester Nare?

  Some simple life, billions of years.

• 4:57Krishna Choudhary?

  Yeah.

• 4:58Lester Nare?

  And in the entirety of that time period, the life on Earth has never had control of its own destiny.

• 5:05Krishna Choudhary?

  Yeah.

• 5:05Lester Nare?

  As it relates to celestial objects and their impact on the planet.

• 5:12Krishna Choudhary?

  Hmm.

• 5:12Lester Nare?

  So what you're suggesting is that humanity, for the first time in the four-plus-billion-year history of Earth.

• 5:19Krishna Choudhary?

  Yeah.

• 5:20Lester Nare?

  Has finally enabled itself to have agency on its cosmic destiny.

• 5:27Krishna Choudhary?

  Yeah.

• 5:29Lester Nare?

  Based on these objects potentially coming in to impact us.

• 5:32Krishna Choudhary?

  Exactly.

• 5:32Lester Nare?

  This is a very interesting story for us to understand.

• 5:34Krishna Choudhary?

  Yes, yes. And I just want to say a quote from the lead author of that paper. He said, "If an asteroid is ever on its way to hitting the Earth, we can more confidently now say that we have the ability to push them around and away from Earth."

• 5:48Lester Nare?

  Hmm.

• 5:49Krishna Choudhary?

  This was by the lead author, Rahila Makadia, from the University of Illinois Urbana-Champaign. And can I just say, the news article where this quote comes from, they quote him as "a planetary defense researcher."

• 6:03Krishna Choudhary?

  Okay, when I was in grad school, on my CV is written graduate student researcher. This guy can write planetary defense researcher on his CV. How sick is that?

• 6:15Lester Nare?

  That's so awesome.

• 6:16Krishna Choudhary?

  Right? Alright, so as you said, let's get into the history and why this is so important. The threat comes from these things called near earth objects. This is an animation showing all of the near earth objects that we've ever seen. The blue circle or the, you know, the blue orbit in the middle, that's the earth.

• 6:34Lester Nare?

  Okay.

• 6:34Krishna Choudhary?

  And look at all of these dots.

• 6:35Lester Nare?

  Yes.

• 6:36Krishna Choudhary?

  All of these dots are threats to us.

• 6:40Lester Nare?

  For those who are listening and not watching the pod currently, there are thousands, hundreds of thousands

• 6:47Krishna Choudhary?

  Yeah.

• 6:48Lester Nare?

  of these objects in near earth orbit. It's, it's actually a very nauseating amount.

• 6:52Krishna Choudhary?

  Yeah, yeah, it's actually quite like concerning, right? Because if you look like, let's just linger on this animation for a second. The, the earth's orbit, there's already a bunch that are sharing earth's orbit.

• 7:03Lester Nare?

  Yes.

• 7:04Krishna Choudhary?

  Right? Then you see there's a faint line where Mars's orbit is. That's the, the red line. And then there's this giant belt, almost cloud of orbits.

• 7:12Lester Nare?

  Yes.

• 7:12Krishna Choudhary?

  That's the asteroid belt in between Mars and Jupiter, right? Those are also threats, not just the ones that are near

• 7:19Lester Nare?

  Right.

• 7:20Krishna Choudhary?

  in earth orbit, but like you can imagine like some random gravitational anomaly, like Jupiter pushes one of these asteroids out of the way, or these two asteroids get a little bit together. And then they get nudged into the inner solar system.

• 7:34Lester Nare?

  Exactly. It's like in a car accident. You've, you're changing lanes and you side swipe the car next to you.

• 7:39Krishna Choudhary?

  Yeah.

• 7:39Lester Nare?

  And then they're now side swiping the car next to them.

• 7:41Krishna Choudhary?

  And then there's an 18 wheeler behind, like it's, it can get bad really fast.

• 7:45Lester Nare?

  Really fast.

• 7:45Krishna Choudhary?

  Right?

• 7:46Lester Nare?

  Similar to the Kessler effect, uh, when a satellite

• 7:49Krishna Choudhary?

  That's right.

• 7:49Lester Nare?

  uh, crashes in orbit and then it basically creates catastrophic failure for everything because there's just these little things flying around.

• 7:57Krishna Choudhary?

  Yeah.

• 7:57Lester Nare?

  And it's going to impact everything.

• 7:58Krishna Choudhary?

  Yeah, exactly. And any momentum transfer can be really bad.

• 8:01Lester Nare?

  Yes.

• 8:01Krishna Choudhary?

  Right? And Hollywood is obviously obsessed with this. We've got, as you were mentioning, Armageddon, Deep Impact.

• 8:08Krishna Choudhary?

  I can't think of many more. Oh, Don't Look Up is a big one. That's the most recent one. That was more about like climate change. Yes. But it was still like the metaphor was really funny and at the end of the day, the literal movie is about a comet. That is coming into earth and nobody believes the scientists. So this has actually happened in human recorded history. 1908 was the Tunguska event in Siberia. It was a 50 to 80 meter object and it burst 10 miles above the surface. So it didn't even make contact with the earth. Yep. It exploded because it was heated up by so much. And it flattened 30 million trees over hundreds of kilometers squared. Yes. Fortunately, it was in the middle of nowhere in Siberia, right? But imagine if that happened on a population center.

• 8:53Krishna Choudhary?

  Yeah. It would be way, way worse than Hiroshima Nagasaki. Yes. Right? Yes. Um, in 1980, there was the Alvarez hypothesis, which was linking the Cretaceous Paleogene extinction, which is the extinction of the dinosaurs 66 million years ago. It linked that to a cosmic impact. In 1991, the Chixca Club crater was discovered in the Yucatan Peninsula because a bunch of oil companies were charting the gravity, the specific gravity around the Yucatan Peninsula, looking for oil. Interesting. And so in order to look for oil, what you want to look for is like low density packets under the earth's crust.

• 9:36Krishna Choudhary?

  And one of the best ways to do that is to literally just measure the acceleration due to gravity, the thing that we learn in high school being 9.8 meters per second squared. Well, if you go 9.81, you know, all of the little digits. The little tiny deviations of that acceleration due to gravity. If it's a little less than normal here versus somewhere else, that could mean that there's a low density packet underneath the ground, which is why it's not pulling on whatever object. Right. That you're using to measure that acceleration. So oil companies were doing that. They actually found a ring of high density. Oh. And that ring was the size of the Yucatan Peninsula. And it was this primordial crater from 66 million years ago.

• 10:18Lester Nare?

  I have one clarifying question. When you, when you mentioned like low density pocket, what you're referring to is like a lake of oil under the ground.

• 10:26Krishna Choudhary?

  Exactly. Okay. Yeah. Yeah. Instead of rock.

• 10:28Lester Nare?

  Instead of rock. Cause the, the oil is less dense than rock. And so what they're looking for is an underground lake of oil.

• 10:35Krishna Choudhary?

  Exactly. Yeah. And that underground lake of oil would decrease the effect of gravity in that location. So if you were to measure gravity very, very precisely, you'd be able to chart out where the oil is.

• 10:46Lester Nare?

  That makes sense. This is also why science is so important to capitalism.

• 10:50Krishna Choudhary?

  Yeah.

• 10:50Lester Nare?

  Because the alpha matters.

• 10:52Krishna Choudhary?

  The alpha matters. And like, and like the, you know, the, the closer you get to this precision, the more you can unlock, you know? And then finally in 2013, there was the Chelybinsk meteor, which was a 20 meter object.

• 11:06Lester Nare?

  Yes.

• 11:07Krishna Choudhary?

  Over a thousand injuries. It happened also over Russia.

• 11:09Lester Nare?

  Yes. And this was one that was very, there was video, like, you know, it was very, because we had media and technology and devices. It's probably the most prominent atmospheric, large object atmospheric breakup explosion.

• 11:25Krishna Choudhary?

  Yeah.

• 11:26Lester Nare?

  And, you know, over a thousand. I mean, it was a lot. It was.

• 11:29Krishna Choudhary?

  It was a lot. It was a lot. A lot of broken windows and things like that. Um, one of the reasons why we have so much footage on that is because Russians, the Russians love having dash cams.

• 11:40Lester Nare?

  Yeah, yeah.

• 11:40Krishna Choudhary?

  Because, I don't know. I mean, I don't want to say anything.

• 11:44Lester Nare?

  Yeah. Comment in the, in the, in the thread if you know the reason why that's true.

• 11:47Krishna Choudhary?

  Yeah. Yeah. But anyways, Russians love having dash cams. And so there's so much dash cam footage of the meteor just like coming down, right? It's, it's pretty incredible.

• 11:55Lester Nare?

  I want to just reemphasize that that 2013 meteor was only 20 meters.

• 12:03Krishna Choudhary?

  Yeah.

• 12:03Lester Nare?

  In, in, I guess diameter.

• 12:05Krishna Choudhary?

  Yeah.

• 12:06Lester Nare?

  It's, it's not a super large object.

• 12:08Krishna Choudhary?

  No, no, no.

• 12:09Lester Nare?

  And the.

• 12:09Krishna Choudhary?

  Like the size of a house.

• 12:10Lester Nare?

  The force and the impact, uh, and the thousand, because the devastation is.

• 12:15Krishna Choudhary?

  Was pretty severe. Yeah.

• 12:17Lester Nare?

  Right. So.

• 12:18Krishna Choudhary?

  Yeah.

• 12:18Lester Nare?

  In any event.

• 12:19Krishna Choudhary?

  So our best strategy, our best strategy when it comes to planetary defense is actually to nudge it. We want to give it some momentum and then we want to get out of the way. And hopefully that thing gets out of the way, right? Because we've nudged it and it just avoids Earth. It keeps going around the sun, but now its orbit has changed a little bit. In the same analogy of the car accident like before, imagine you're in a James Bond movie. And James Bond is in a car in the left lane. And the love interest in that movie is handcuffed to the steering wheel in the car in the right lane. And they're both going 90 miles an hour down a road. And the right car is about to hit something. He's like, well, let me just bump it. Yeah. Out of the way. Mm hmm. Cause that'll change how it's driving. Yeah. Out of the way of about to hit this brick wall that's in front of us. Yes.

• 13:03Krishna Choudhary?

  As like a grounded analogy. Yeah, yeah, yeah. Is this one of the dream fantasies of yours?

• 13:11Krishna Choudhary?

  Yeah, he had a lot of, he had a lot of detail in that one, guys. Yeah, but that's exactly right. We want to just nudge it, get it out of the way. Okay? In 2022, that was the DART mission. It was the first intentional deflection. It was actually launched out of Vandenberg in 2013, which is right down the street of Southern California. It went with the Earth to meet up with this double asteroid system. So this double asteroid system, which is Didymos and Dimorphos. So we can look at an animation of their orbits, right? The green is the double asteroid system. Yes. The teal is Earth. Yes. And the pink is what we're seeing of the, our, like, what you call it? The, the DART mission. The DART mission, right?

• 13:56Krishna Choudhary?

  Okay, sorry. So let me just recap. The blue is Earth. Yes. The DART mission comes out in pink from Earth. It's following Earth, as you can see. It's just leading it a little bit. Yes, yes. And the green double asteroid system that we're trying to hit is going to come meet up with us. Yes. The double asteroid system is actually a near Earth orbit. And there you go. Yep. That's when the impact happens. You can tell that the impact is happening pretty close to Earth. Yeah, yeah, yeah. Both are moving together and then the impact happens here. But Earth is pretty close. Yes. That is by design, because what we want to do is we want to have all of the observatories on Earth looking at this thing to get as much data as possible. The, the impact was like 6 million miles, which. In the grand scheme of things, it's not that far away.

• 14:41Lester Nare?

  I want to just pull this back up really quick, this animation. Because I think what's so interesting is when you look at where it launches from.

• 14:49Krishna Choudhary?

  Yeah.

• 14:50Lester Nare?

  The launch of DART happened on the opposite side, like it first left Earth.

• 14:55Krishna Choudhary?

  Yeah.

• 14:56Lester Nare?

  On the opposite side of the sun from where the asteroid was coming in. And it did almost a three quarters orbit.

• 15:04Krishna Choudhary?

  Yeah.

• 15:05Lester Nare?

  Prior to contact. And I just want to, the distance. Look, if I'm trying to throw a paper ball, a paper towel ball into the trash can from my desk. I'm maybe gonna hit it six times out of ten. We're trying to send this thing in an orbit.

• 15:24Krishna Choudhary?

  Around the sun.

• 15:25Lester Nare?

  Around the sun.

• 15:25Krishna Choudhary?

  With the earth.

• 15:26Lester Nare?

  With the earth, millions of miles.

• 15:28Krishna Choudhary?

  Yeah.

• 15:29Lester Nare?

  And it made direct contact. I just want to really emphasize the level of precision that is required. Because that's not the point of this story per se, it's the second piece.

• 15:41Krishna Choudhary?

  Yeah.

• 15:41Lester Nare?

  But that initial part in and of itself.

• 15:43Krishna Choudhary?

  Yeah.

• 15:44Lester Nare?

  Is an exceptional piece of just both the engineering, the math, and the operational planning to execute on.

• 15:50Krishna Choudhary?

  Yeah, I mean, NASA is just incredible at doing this kind of stuff. And as you mentioned, right, like the thing gets released. It makes almost full circle. So it's almost like if it got launched in, I wish I knew the exact date that it got launched, right? But if it got launched somewhere, it's gonna almost do a full year.

• 16:10Lester Nare?

  Yes.

• 16:10Krishna Choudhary?

  Around, right?

• 16:11Lester Nare?

  Yes.

• 16:11Krishna Choudhary?

  Before actually getting there. Pretty incredible. So, that's what we want to do, right? We want to have it, we want to have it impact very close. And then we want to have all of the observatories watch this impact happen.

• 16:25Lester Nare?

  Yes.

• 16:25Krishna Choudhary?

  Right?

• 16:26Lester Nare?

  Yes.

• 16:26Krishna Choudhary?

  Yeah.

• 16:27Lester Nare?

  Because we don't have a lot of instruments deeper in space. And so, the best way we can capture data is when it's as close to our instruments as possible.

• 16:35Krishna Choudhary?

  That's right, yeah, that's right. And before we move on.

• 16:39Lester Nare?

  Yes.

• 16:39Krishna Choudhary?

  Let's do some housekeeping.

• 16:40Lester Nare?

  Yes, so housekeeping notes. Again, we are testing our new format, two to three episodes a week. Each episode, when it's a research paper or a deep dive, is going to be fully focused just on that topic matter. We are also going to do the rundown as its own standalone episode. One, so we can have a little bit of fun. Talk about a variety of things, a little grab bag. Think about it like the weekend update on SNL. And I am determined to make a science game show out of this with Krishna as our recurring contestant, which you can't see from the current angle. He's getting a little bit of indigestion at the thought of that.

• 17:19Lester Nare?

  But if you are intrigued by the concept or you're a longtime listener, as you know, we are a victim like we all are to the billionaire algorithm. So a like, follow, share, subscribe is super valuable for us to help get the show to more people. And if you are really passionate about what we're doing, it really fills your cup every day and you want to find a way to support us, we do have our donation portal at ffpod.com/donate. If you want to catch us on socials, so you see us casually as you're scrolling the TikToks in between cat dancing videos and whatever the next trending voiceover topic is,

• 18:03Lester Nare?

  we are at FFP pod across all of the socials. And I believe that is the conclusion of our show notes this week.

• 18:13Krishna Choudhary?

  Yeah, one more thing, just from me on a personal end. So for those listening, if anyone is going to APS, the global summit meeting in Denver, that's the American Physical Society Global Summit in Denver this coming week. So the week of this podcast release, on Thursday, I'm giving a talk. So, you know, if you're going, just look me up on the schedule and come check out my talk on Thursday. I'm still, you know, doing, doing stuff and talking to people about all the research that I'm doing.

• 18:44Lester Nare?

  And if you want to know about the research that he's doing, which is very interesting, make sure if you're at APS, you go see it and embarrass Krishna by asking for an autograph in front of all the scientists and academics.

• 18:56Krishna Choudhary?

  Okay, let's get back to the story, please. All right, the target of the DART mission was the Didymos Dimorphos binary system. Just to show how the two asteroids compare, the moon, the moonlit that we were trying to target is a bit bigger. It's in between the Statue of Liberty and the Eiffel Tower in terms of how big it is. Didymos is like Burj Khalifa type in terms of how big it is, like the diameter. And what we're trying to kamikaze is the moonlit.

• 19:26Lester Nare?

  Yes.

• 19:27Krishna Choudhary?

  The little, the, the, the little, small one.

• 19:29Lester Nare?

  Yep.

• 19:29Krishna Choudhary?

  Okay, so in, during the mission, actually, the main DART, like asteroid, or sorry, the main DART probe, the satellite.

• 19:39Lester Nare?

  Yes.

• 19:40Krishna Choudhary?

  Actually stood behind to watch this unfold and it let out a little like,

• 19:46Krishna Choudhary?

  kamikaze satellite drone.

• 19:48Lester Nare?

  Fox One, go.

• 19:49Krishna Choudhary?

  Yeah, exactly. And, and so this guy's, this guy's job was to go and

• 19:55Krishna Choudhary?

  bomb.

• 19:56Lester Nare?

  Yes.

• 19:57Krishna Choudhary?

  Di- Dimorphos.

• 19:58Lester Nare?

  Let's say, let's say make contact.

• 20:00Krishna Choudhary?

  Make contact, sorry, I, I shouldn't, yeah, in today's world, let's, let's rephrase that. We're, we're trying to make contact with Dimorphos.

• 20:07Lester Nare?

  Yes.

• 20:07Krishna Choudhary?

  And the other, the, the main ship, the mothership is watching this all in action. Because it wants to see what is the effect.

• 20:13Lester Nare?

  Yes.

• 20:14Krishna Choudhary?

  Of that contact on the system. Why binary? It's because we want rapid measurement of deflection, right? We want it, the orbit is going one way, we want to see if it's slowed down or sped up. Okay, whatever.

• 20:26Lester Nare?

  And with a, with a dual orbit system, it is easier to ascertain the answer to that than a single object.

• 20:34Krishna Choudhary?

  Yes, yes, exactly. And here's why.

• 20:37Lester Nare?

  Okay.

• 20:37Krishna Choudhary?

  The mutual orbit velocity of Dimorphos and Didymos is about 17 centimeters per second.

• 20:43Lester Nare?

  Okay.

• 20:43Krishna Choudhary?

  Okay, which means that if we were to impact some momentum, 17 centimeters per second, even for something as large as, you know, a rock, a mountain, let's say, I can reasonably try and. Discern some change because I'm going at it at six kilometers per second. So reasonably some of my momentum is going to get transferred and then I'm going to be able to see a change. And they were able to see a change. They saw that the mutual orbit period of was altered by 33 meters. And this is something that we can rapidly measure. The orbit got smaller, it got shorter by 33 meters. And the DART system, which is monitoring this, can calculate that, measure it, no problem.

• 21:26Lester Nare?

  Makes total sense. We set up an observer and a probe to make contact. The the initial data point that was going to be captured is, is the local orbit going to change from 17 centimeters per second to something else? Because by making contact, going back to our car analogy, if you're into two lane highway and you're one car and you swerve to the right and make contact with the other car, your momentum in part will be transferred to that other car.

• 21:55Krishna Choudhary?

  Exactly.

• 21:56Lester Nare?

  Which is why then you have to see the driving scenes where they're like, oh.

• 21:59Krishna Choudhary?

  Yeah, exactly.

• 22:00Lester Nare?

  To counteract the transfer of momentum.

• 22:02Krishna Choudhary?

  Yeah, and that's why that's why the double the double system matters, right? Because like this is a small enough system where like I can, I can make that, I can make that change discernible. 33 minutes out of 12 hours, something I can easily measure now, right? When it comes to the big thing, now let's think about the big thing. There's a, there's the big system that's moving around the sun.

• 22:23Lester Nare?

  Yes.

• 22:23Krishna Choudhary?

  That thing is moving at 23 kilometers per second. Okay? The change that my momentum is going to cause is going to be less than a millimeter per second. That's way harder to measure.

• 22:36Lester Nare?

  Yeah.

• 22:36Krishna Choudhary?

  And that is what this paper is doing.

• 22:38Lester Nare?

  I see.

• 22:39Krishna Choudhary?

  This paper is measuring the big one. So let's get into some of the physics that we were talking about, right?

• 22:43Lester Nare?

  Okay.

• 22:44Krishna Choudhary?

  We've got the kinetic impactor, which is this idea of a sort of satellite drone going in, making contact and its momentum getting transferred. Now, it's not that simple because it's not a simple momentum conservation undergrad problem. Okay? It turns out that. When I go and make this contact at high velocity at 6 kilometers per second to this little moon, that's gonna generate shock waves, so the asteroid is gonna ring a little bit.

• 23:13Lester Nare?

  Yep.

• 23:14Krishna Choudhary?

  There's gonna be an impact crater, and there's also gonna be massive ejecta that is flying the opposite direction. So imagine my hand is the moon, I make contact, there's gonna be ejecta flying this way.

• 23:25Lester Nare?

  Yes.

• 23:25Krishna Choudhary?

  It's almost like another little rocket impulse that's going the opposite direction. So what I'm gonna get is something called momentum enhancement. The amount of momentum that gets transferred is not just how much I went in with, but also how much that it threw out.

• 23:41Lester Nare?

  Yes.

• 23:41Krishna Choudhary?

  Right?

• 23:42Lester Nare?

  Yes.

• 23:42Krishna Choudhary?

  And so there's this beta factor called momentum enhancement factor, and that's the ratio of the total momentum that was transferred to the target, divided by the total momentum that I had. If beta is greater than 1, that means that I've actually impacted more momentum than I originally had, because the original object has pushed out a bunch of debris in the opposite direction. Does that make sense?

• 24:06Lester Nare?

  Yeah, so what we're saying is, we have an object, our object's coming in to make contact with something. This actually dovetails with the panspermia story we talked about in our last episode about impacts.

• 24:17Krishna Choudhary?

  Yeah.

• 24:18Lester Nare?

  That there's ejecta, and the velocity by which you hit something can shoot that stuff very, very far.

• 24:23Krishna Choudhary?

  Very, very fast.

• 24:24Lester Nare?

  And can potentially spread life. But what we're saying here is, the amount of stuff that gets ejected out almost creates this additional push in the direction you were already going.

• 24:34Krishna Choudhary?

  Yes.

• 24:35Lester Nare?

  In addition to the amount of push that you individually as the object was giving.

• 24:38Krishna Choudhary?

  Yes, and that's that enhancement.

• 24:40Lester Nare?

  And that's the enhancement, right?

• 24:41Krishna Choudhary?

  Yes. And so it's really important for us to calculate what this enhancement is. Because if, God forbid, there's an asteroid coming for us.

• 24:48Lester Nare?

  Yes.

• 24:49Krishna Choudhary?

  Knowing this value of beta is gonna be instrumental for figuring out how fast do I need to nudge it, right?

• 24:55Lester Nare?

  Yes.

• 24:56Krishna Choudhary?

  How big of the drone does the satellite need to be in order to make contact? How much momentum am I trying to put in there? Because the momentum transfer is not just what I'm putting in initially, but it's this beta factor multiplied by the initial momentum.

• 25:10Lester Nare?

  So the idea here is when Morgan Freeman is in the classified room talking, and someone says, "We have an Ellie, an extinction level event, because this rock is coming." And they're saying, "Okay, what options do we have?" NASA would be able to come into the room and say, because we had our DART mission, where we were able to get real-world data about what the momentum enhancement factor is, we know that because this trajectory is X, Y, or Z, we're going to need to send this amount of payload at this speed.

• 25:47Krishna Choudhary?

  Yep.

• 25:48Lester Nare?

  Because the math is mathing.

• 25:49Krishna Choudhary?

  Exactly. And now we have all the parameters to make that math math.

• 25:52Lester Nare?

  Right.

• 25:53Krishna Choudhary?

  Right?

• 25:53Lester Nare?

  Okay.

• 25:54Krishna Choudhary?

  Okay.

• 25:56Krishna Choudhary?

  With the DART mission, we got a local version of beta, right?

• 26:00Lester Nare?

  Yes.

• 26:01Krishna Choudhary?

  But let's do a little lesson in undergrad physics.

• 26:03Lester Nare?

  Okay.

• 26:04Krishna Choudhary?

  We're going to talk about systems and what are their components.

• 26:08Lester Nare?

  Okay.

• 26:09Krishna Choudhary?

  Whenever we do undergrad physics, we always try to think of what is the system that is isolated from the environment that we're trying to work with? For example, the Earth-Sun-Moon system.

• 26:20Lester Nare?

  Yes.

• 26:21Krishna Choudhary?

  There's three bodies, right? When we think about like,

• 26:26Krishna Choudhary?

  you know, shooting something off Earth, or we think about just tides, for example. Actually, tides is a bad idea because we need both the sun and the moon.

• 26:33Lester Nare?

  Sure.

• 26:34Krishna Choudhary?

  But if there's stuff that's local to the Earth and the moon, we don't really need to worry about the sun too much.

• 26:40Lester Nare?

  Okay.

• 26:41Krishna Choudhary?

  Okay? We can have momentum transfer in between the Earth and the moon, and we'll be fine.

• 26:45Lester Nare?

  Would satellite stuff be an example?

• 26:48Krishna Choudhary?

  Yeah, satellite stuff would kind of be an example of that, because like the sun is kind of far away. It's like really big, but it's still like, it doesn't, it doesn't like come into the equation, or it comes into the equation in another way. The idea is that like, there's, there's granular levels of how we want to describe a physics problem, right? And my point here is, when the local measurement was made, when we figured out, oh, the orbit decreased by 30

• 27:19Lester Nare?

  Between the two of them.

• 27:20Krishna Choudhary?

  Minutes, between the two of them. What we, what we really did was figure out a local beta. We figured out a local momentum transfer that happened because of the moon.

• 27:33Krishna Choudhary?

  And how much, how much escaped the little moon's gravity, right? To create a nudge between the moon in relation to the big Didymos.

• 27:44Lester Nare?

  Yes.

• 27:45Krishna Choudhary?

  So dimorphosis now speeding up.

• 27:48Lester Nare?

  In relation.

• 27:49Krishna Choudhary?

  In relation to Didymos.

• 27:50Lester Nare?

  Right.

• 27:51Krishna Choudhary?

  What we really care about when it comes to planetary defense is the sun binary system. What we care about is the heliocentric momentum enhancement factor, not the center of mass frame momentum enhancement factor. Here, what we're looking at is from Earth, the impact on Didymos.

• 28:12Lester Nare?

  Okay.

• 28:13Krishna Choudhary?

  Okay. And what you can see is you don't even resolve the binary system. It looks like a single dot.

• 28:19Lester Nare?

  Yes.

• 28:20Krishna Choudhary?

  But we didn't hit the main dot. We hit the moon. And yet there's all this ejecta that came out.

• 28:26Lester Nare?

  Yes.

• 28:27Krishna Choudhary?

  All of that ejecta that came out has escaped the binary system. That ejecta not only escaped the moon, the main Didymos, big asteroid couldn't even keep it together.

• 28:39Lester Nare?

  Together, right?

• 28:40Krishna Choudhary?

  Right. So all of that ejecta escaped the moon.

• 28:42Lester Nare?

  Yes.

• 28:43Krishna Choudhary?

  And the big asteroid.

• 28:44Lester Nare?

  Yes.

• 28:45Krishna Choudhary?

  And has gone out into outer space.

• 28:46Lester Nare?

  Yes.

• 28:47Krishna Choudhary?

  Which means that there isn't a momentum enhancement factor on the entire system as a whole. It's a really nice, like, sort of little undergrad problem on conservation of energy, right? Which is this idea that like, even though I only hit the moon, I'm actually changing the trajectory of the entire moon planet or moon asteroid system. I didn't touch the asteroid.

• 29:08Lester Nare?

  Yes.

• 29:09Krishna Choudhary?

  But the asteroid's orbit has been changed because I hit its moon.

• 29:12Lester Nare?

  So, so as a maybe a pop culture reference point, let me know if this actually tracks with what you're saying. There's a famous, not a famous, there's a movie that came out maybe in the last two, three years called Moonfall.

• 29:24Krishna Choudhary?

  Okay.

• 29:24Lester Nare?

  And the moon.

• 29:26Krishna Choudhary?

  Fell.

• 29:27Lester Nare?

  Oh dude.

• 29:28Krishna Choudhary?

  Yeah, I know, I know this.

• 29:29Lester Nare?

  And so the point, even though the moon had yet to make contact with Earth, the simple fact that it moved from its existing orbital position around the Earth to being getting to getting closer, totally disrupted a variety of things in Earth because of the tides change and the proximity and it's so it's like it's like a local move. It's like local, but it it had this larger impact, even though it's maybe not the right analogy.

• 29:57Krishna Choudhary?

  It's okay. So I want to, I want to take that a step further because in that one, what you're talking about is local changes again.

• 30:03Lester Nare?

  Oh, so I'm still talking.

• 30:04Krishna Choudhary?

  What I'm saying, what I'm saying here is like, suppose something hit the moon, which caused it to fall.

• 30:08Lester Nare?

  Yes.

• 30:08Krishna Choudhary?

  Right. There would be an energy transfer into the moon.

• 30:12Lester Nare?

  Yes.

• 30:13Krishna Choudhary?

  Right. So looking from Earth's perspective, the moon would gain some energy, let's say. Now, looking from an alien perspective that looks at the Earth and Moon system as a single system.

• 30:22Lester Nare?

  Yes.

• 30:23Krishna Choudhary?

  There would be a change in energy in that entire system. Both the Earth and the Moon would gain some energy. So both that's that system as a whole would change its trajectory around the Sun.

• 30:32Lester Nare?

  I, I.

• 30:33Krishna Choudhary?

  That's the idea.

• 30:34Lester Nare?

  That's the idea.

• 30:34Krishna Choudhary?

  Does that what I'm, is it depending on how granular you make your system, at the end of the day, conservation of energy and conservation of momentum.

• 30:41Lester Nare?

  Yes.

• 30:42Krishna Choudhary?

  Are paramount.

• 30:43Lester Nare?

  Yes.

• 30:43Krishna Choudhary?

  So if the momentum was transferred to the Moon, it'll also be transferred to the Earth-Moon system.

• 30:48Lester Nare?

  Yes.

• 30:49Krishna Choudhary?

  Which means that the Earth-Moon system moving around the Sun is going to change. That's what's happening here.

• 30:53Lester Nare?

  I, that makes sense.

• 30:54Krishna Choudhary?

  That's the key that I need, that I need everyone to try to like sort of internalize.

• 30:58Lester Nare?

  Yes.

• 30:59Krishna Choudhary?

  Which is conservation of energy and momentum is true regardless of the size of your system.

• 31:04Lester Nare?

  Yeah, right. Whatever level or layer you're observing the system, a change of momentum in one of those layers. Yeah. Will then, will, will transcend across all of the, either downstream or upstream. I don't know which direction.

• 31:20Krishna Choudhary?

  Yeah, I don't know which direction it is either, but I think.

• 31:22Lester Nare?

  One of those two.

• 31:22Krishna Choudhary?

  Yeah, you, you, you get, you get, you get exactly what I'm saying, right?

• 31:25Lester Nare?

  Yes.

• 31:26Krishna Choudhary?

  And so. If that ejecta is escaping the combined gravity of Didymos and Dimorphos.

• 31:32Lester Nare?

  Yes.

• 31:32Krishna Choudhary?

  Then it's gonna change the trajectory of the entire system.

• 31:36Lester Nare?

  I see now.

• 31:37Krishna Choudhary?

  Which means that I need to figure out a beta for the entire system.

• 31:41Lester Nare?

  Yes.

• 31:41Krishna Choudhary?

  Not just what I had figured out before, which is just the little moon.

• 31:44Lester Nare?

  Right.

• 31:45Krishna Choudhary?

  Around this.

• 31:47Lester Nare?

  Yes, that makes sense. Okay. Because ultimately, from a planetary defense perspective.

• 31:52Krishna Choudhary?

  That's what matters.

• 31:52Lester Nare?

  You care about the whole system.

• 31:53Krishna Choudhary?

  Yeah, yeah, yeah, that's what matters.

• 31:55Lester Nare?

  And being able to change the whole system.

• 31:57Krishna Choudhary?

  The whole system.

• 31:57Lester Nare?

  But in order to do so, you need to understand the component parts, component parts necessary.

• 32:02Krishna Choudhary?

  Yeah.

• 32:03Lester Nare?

  To be able to impart that level of change on the whole system.

• 32:06Krishna Choudhary?

  Exactly, yeah. And to tell you just how hard that is to do.

• 32:10Lester Nare?

  Right.

• 32:11Krishna Choudhary?

  Um, the heliocentric velocity, this is something that I covered a little bit earlier. The system moves at 23 kilometers per second. And I'm trying to detect, I'm trying to detect a change that is less than one millimeter per second. This thing is moving at 26 kilometers per second. And I need a.

• 32:30Lester Nare?

  23, 20.

• 32:31Krishna Choudhary?

  Sorry, yeah, 23 kilometers per second. This thing is moving at 23 kilometers per second.

• 32:36Lester Nare?

  Yes.

• 32:36Krishna Choudhary?

  And that velocity is going to change by a millimeter per second, actually less. Does that make sense? That's several orders of magnitude. A millimeter is a thousandth of a meter, which is a thousandth of a kilometer. So this is about 10 millionth.

• 32:51Lester Nare?

  Yeah.

• 32:51Krishna Choudhary?

  One part in 10 million.

• 32:53Lester Nare?

  Yeah.

• 32:53Krishna Choudhary?

  Is what I'm trying to sense.

• 32:54Lester Nare?

  Yeah.

• 32:55Krishna Choudhary?

  For an asteroid that is millions of miles away.

• 32:59Lester Nare?

  Uh, we like to say this is non-trivial.

• 33:01Krishna Choudhary?

  This is, this is extremely non-trivial, right?

• 33:04Lester Nare?

  Yeah.

• 33:04Krishna Choudhary?

  Like, to make that measurement, this is another lesson in, again, some of our favorite topics on the podcast, precision measurement.

• 33:11Lester Nare?

  Right, that's such a key, it's, we have a toolbox in science with Hammer, Food Driver. Some tools are more useful than others.

• 33:19Krishna Choudhary?

  Yeah.

• 33:19Lester Nare?

  Some tools you use all the time, like a hammer, there's a lot of things you can do with a hammer.

• 33:22Krishna Choudhary?

  Yeah, lasers is the thing in physics.

• 33:25Lester Nare?

  You see something, oh, put a laser at it.

• 33:26Krishna Choudhary?

  Put a laser at it.

• 33:28Lester Nare?

  But, but I think, again, measurement, it's not, measurement is a whole craft in and of itself. With a level of density of complexity and expertise necessary to be able to do so. In a robust enough way.

• 33:44Krishna Choudhary?

  Yeah.

• 33:45Lester Nare?

  And this is a measurement challenge. Speaking of measurement challenges, in our first nine minutes of our appearance on the Dave Chang show, which is on Netflix, check it out.

• 33:57Krishna Choudhary?

  Oh, yeah.

• 33:58Lester Nare?

  Was spent on the double slit experiment, which is a measurement problem.

• 34:00Krishna Choudhary?

  Yeah, that is a measurement problem. That that completely caught me off guard. Cause like, we just got there and he's like.

• 34:06Lester Nare?

  Came in with a hard landing.

• 34:07Krishna Choudhary?

  What about that MIT paper? I'm like, that was like months ago. What, what is going on? I can't believe he like, watched that one. Like that, that's, he's, he's an OG fan, dude.

• 34:16Lester Nare?

  And he's also quite, quite sharp.

• 34:18Krishna Choudhary?

  Yeah, dude, he, he remembered so much.

• 34:20Lester Nare?

  He's quite sharp on that.

• 34:21Krishna Choudhary?

  That was, that was really cool.

• 34:22Lester Nare?

  But the measurement problem is.

• 34:23Krishna Choudhary?

  Measurement problem. And this is where this particular paper comes in. It's measuring this unmeasurable one millimeter per second, actually a lot less.

• 34:32Lester Nare?

  Change.

• 34:32Krishna Choudhary?

  Change in a 23 kilometer per second object.

• 34:35Lester Nare?

  That is millions of miles away.

• 34:37Krishna Choudhary?

  And this was a, a paper that came out in Science Advances, Direct Detection of an Asteroid's Heliocentric Deflection. Okay? The target change that they measured was 11 microns per second.

• 34:50Lester Nare?

  Jesus.

• 34:50Krishna Choudhary?

  Okay? Out of 26 kilometers per second. Okay? And what this means, to just give you a sense of scale.

• 34:58Lester Nare?

  Yes.

• 34:59Krishna Choudhary?

  So that asteroid system goes around the earth every 770 days. So that's about two years. And this tiny change in velocity means that the two years of orbit has been shortened by 0.15 seconds.

• 35:16Lester Nare?

  Oh, my goodness.

• 35:17Krishna Choudhary?

  Okay? So the sec, so a year on that, on that asteroid is now shorter than, shorter by 0.15 seconds because we crashed into the moon.

• 35:26Lester Nare?

  That's, and so there's just sort of two things about this, which is interesting. One is what an exceptional job we've done to be able to measure such a small scale change.

• 35:37Krishna Choudhary?

  And, and that's what we're going to get into next.

• 35:39Lester Nare?

  And then the second piece is now we then have a reference point to be able to say. How much do we need to scale up? You know, because we just sent a small little thing.

• 35:47Krishna Choudhary?

  Yeah.

• 35:48Lester Nare?

  We didn't send a big old, because also getting payloads into space is expensive.

• 35:51Krishna Choudhary?

  Yeah, yeah.

• 35:51Lester Nare?

  And cost money. And we don't like to spend too much money now on fundamental science stuff. But now you could go to the Joint Chiefs and say, we're going to need a hundred thousand megaton X.

• 36:03Krishna Choudhary?

  Yeah.

• 36:03Lester Nare?

  In order to get the level of momentum.

• 36:05Krishna Choudhary?

  Yeah.

• 36:05Lester Nare?

  But we just have a baseline now.

• 36:07Krishna Choudhary?

  Yeah, we have, we have the numbers now.

• 36:09Lester Nare?

  Right.

• 36:09Krishna Choudhary?

  Right? So in order to, in order to make that detection, right? So 11 microns per second is the difference between before and after, before the explosion, before the impact and after the impact. Before the impact, it was going at about 26, 23 kilometers per second, right? And after the impact, it's still going at 23 kilometers.

• 36:28Lester Nare?

  This is like in the hypersonic velocity or like.

• 36:31Krishna Choudhary?

  No, this is not even hypersonic. This is like way.

• 36:34Lester Nare?

  Way.

• 36:34Krishna Choudhary?

  Way.

• 36:35Lester Nare?

  Okay, way.

• 36:36Krishna Choudhary?

  Yeah, like the speed of sound is 343 meters per second.

• 36:39Lester Nare?

  Okay.

• 36:39Krishna Choudhary?

  So point three meters per second.

• 36:42Lester Nare?

  Okay.

• 36:42Krishna Choudhary?

  Okay? Yeah. This thing is 23, so that's what? Three times, 60 times, about 60 times the speed of sound. Okay, hypersonic is five.

• 36:52Lester Nare?

  Yeah, so we're.

• 36:52Krishna Choudhary?

  Five and we're happy.

• 36:53Lester Nare?

  So we're in UAP land right now.

• 36:54Krishna Choudhary?

  Yeah, yeah, we're, we're most likely in UAP land. Here's the idea, right? In order to measure that change of 11 microns per second, what I need to do is have that precision on the before and after. Before we get into the after, right? Like if I were to say, if I were to measure something like, oh, the speed of the car, like imagine I'm a cop on the, on the, on the highway, and the, the guy is going at 70 kilometers per second, and then I say, oh, he decreased his, he decreased his, um, speed by point 0003 kilometers per second. Well, I'd need to know what the initial thing was, right? Otherwise, like, how do you, I could just be going like 71.

• 37:38Krishna Choudhary?

  If you said 70, that's only one significant figure for those students in science. That means it could be 71 or 69 or 68, right? So we need to know the before and after equally well in order to make that subtraction.

• 37:50Lester Nare?

  That's a really good point.

• 37:51Krishna Choudhary?

  We don't have like the tools in physics where I could like do. Effective interference where I don't actually need to know the answer because the answer cancels out. No, we're not doing any fancy. We just need to know what the number is and then do subtraction.

• 38:04Lester Nare?

  So the point being, we need to measure it before this. We need to measure before we do anything.

• 38:08Krishna Choudhary?

  Yeah.

• 38:09Lester Nare?

  And in that measurement needs to be very, very good.

• 38:11Krishna Choudhary?

  Very, very precise, down to the micrometer level, right?

• 38:14Lester Nare?

  Yes.

• 38:15Krishna Choudhary?

  And the way they did that was, so this system, Didymos and Dimorphos, has approached Earth over the past 29 years. And we have massive radio telescopes that have bounced microwave signals off this thing. And we can now fit the orbit with a simulator, like a small body simulator and JPL's Comet and Asteroid Orbit Determination Program. And from that, we can figure out what was the before velocity.

• 38:41Lester Nare?

  Because we have this historical data that has captured pictures over time.

• 38:46Krishna Choudhary?

  Yeah, over 29 years.

• 38:48Lester Nare?

  So you're capturing the movement even though the picture is static.

• 38:52Krishna Choudhary?

  Exactly. And it's not just pictures, it's also radar.

• 38:54Lester Nare?

  Okay.

• 38:54Krishna Choudhary?

  Right? Because we can beam it and it'll come back. So it'll give us a distance at least from Earth.

• 38:59Lester Nare?

  Yes.

• 38:59Krishna Choudhary?

  And then the beam will also get blue shifted.

• 39:03Lester Nare?

  Yes.

• 39:03Krishna Choudhary?

  Because the guy is either coming away from us or like, if it's, if it's moving away, then it'll be red shifted. If it's moving towards us, the beam that bounces back will be blue shifted. And we can measure that difference in frequency to figure out the velocity. You do this over multiple years, 29 years, and you get a really nice.

• 39:20Lester Nare?

  Right.

• 39:22Krishna Choudhary?

  Number.

• 39:22Lester Nare?

  And it.

• 39:23Krishna Choudhary?

  And that's the before.

• 39:24Lester Nare?

  And this is like, we basically have a, it's like when you go on a run on an app, like whatever, Strava or whatever. And you get the little trail and it shows like where you've run before. It's like we have that very precise.

• 39:36Krishna Choudhary?

  Very precisely.

• 39:37Lester Nare?

  Of the movement of this.

• 39:38Krishna Choudhary?

  Yeah.

• 39:38Lester Nare?

  Over time.

• 39:39Krishna Choudhary?

  Over 29 years, it's been doing the same thing, right? Over and over again. Okay. So now, how do we get after? Because it's only been three years. We've only got three years, not 29, in order to gather this data. So there's two ways to do it. One is through radio astronomy, astrometry, which is the same thing that I was saying earlier. So radio astrometry is simply you use radar to bounce a microwave signal there and back. They actually use the Goldstone Solar System Radar, which is part of JPL's Deep Space Network. This is actually, whenever we go to Mammoth.

• 40:10Lester Nare?

  Yeah.

• 40:11Krishna Choudhary?

  You know, next time when we go, I, we should like just pull over.

• 40:14Lester Nare?

  Yeah.

• 40:14Krishna Choudhary?

  And I don't think we can get in because it's like security or whatever, but.

• 40:17Lester Nare?

  Hey, let us in.

• 40:18Krishna Choudhary?

  It's still like, next time we go, I'll, I'll point out the radio dishes to you. So we use that and from that we can we can get the time delay. So that'll tell us within tens of meters what the position is. We get multiple positions, then we can calculate the momenta. And also the fact that the signal is red shifted or blue shifted. That Doppler shift is going to give us some idea about velocity. But over three years, it's not going to give us enough of that error bar going down. It's going to be part of it, but we need something else. And this is where something very cool comes in. It's called stellar occultations. Okay, the idea is the asteroid is going to pass in front of stars in the night sky.

• 40:55Lester Nare?

  No way.

• 40:55Krishna Choudhary?

  And it's going to eclipse stars.

• 40:57Lester Nare?

  No way.

• 40:58Krishna Choudhary?

  And so we can measure whenever it eclipses stars, the star is going to blink. And we know the star doesn't actually blink, right? We the star has a constant brightness. So when it like goes down and up and we know where it's going to be. So we're like, dude, this thing is gonna this thing is gonna move in front of that star.

• 41:15Lester Nare?

  Yeah.

• 41:16Krishna Choudhary?

  Like around this time.

• 41:17Lester Nare?

  Yeah.

• 41:18Krishna Choudhary?

  So we can have volunteer astronomers. And that's what I found very cool about the story. There were volunteer astronomers that went out.

• 41:25Lester Nare?

  Yes.

• 41:27Krishna Choudhary?

  And tried to capture these stellar occultations. We're effectively trying to capture the shadow of this asteroid.

• 41:34Lester Nare?

  Passing in front.

• 41:34Krishna Choudhary?

  Passing in front of a star in the night sky.

• 41:36Lester Nare?

  And then the star.

• 41:37Krishna Choudhary?

  Yeah, the shadow is only about a kilometer wide.

• 41:41Lester Nare?

  Oh, my God.

• 41:42Krishna Choudhary?

  Okay, so you need very precise like timing of like where you need to be in order to capture it. And also space. And one thing that I found really cool was there was a guy, volunteer again. He observed two of these occultations. He drove two days each way in the Australian outback.

• 42:01Lester Nare?

  Together.

• 42:01Krishna Choudhary?

  In order to get this data.

• 42:03Lester Nare?

  That's we.

• 42:04Krishna Choudhary?

  Like shout out to this Kangaroo Jack guy, dude, like.

• 42:07Lester Nare?

  The Aussies, Aussie, Aussie, Aussie.

• 42:09Krishna Choudhary?

  Yeah.

• 42:09Lester Nare?

  Oi, oi, oi.

• 42:10Krishna Choudhary?

  That's it's pretty awesome.

• 42:12Lester Nare?

  But this is this is so interesting again, because sometimes, you know, there's a lot of astro photographers, I guess, that are very popular now on socials and stuff like that. And it's a real craft in and of itself.

• 42:25Krishna Choudhary?

  Yeah, yeah, yeah, this guy had to know where to point.

• 42:27Lester Nare?

  Exactly.

• 42:28Krishna Choudhary?

  Like how to get the data.

• 42:29Lester Nare?

  Exactly.

• 42:30Krishna Choudhary?

  Exactly where to be, because you've got a one kilometer radius that you need to you need to get this thing.

• 42:34Lester Nare?

  And you can not only do it for the joys of being curious about the universe around us, but also be a participant and a contributor into sort of institutional.

• 42:45Krishna Choudhary?

  Yeah, dude, I think he should put planetary defense.

• 42:48Lester Nare?

  Yeah, researcher.

• 42:49Krishna Choudhary?

  Researcher on his CV, right? Whatever he's doing in the Australian outback, that should be, that should be part of his CV. So with this international network, they captured 22 distinct occultations between October 2022 and March 2025.

• 43:03Lester Nare?

  Okay.

• 43:04Krishna Choudhary?

  And that is where they got all of their data to where they can say 11 micrometers per second is the change in the velocity of this asteroid.

• 43:12Lester Nare?

  Because now we have like another reference point, another reference frame by which to like understand, because we have the historical data set from the 29 years.

• 43:20Krishna Choudhary?

  And that's the before and we need an after.

• 43:21Lester Nare?

  And we need an after. And so basically, the, the, the stars that are behind, in between, the stars that are behind this passing in between us, create a, a, a reference point for us to measure against.

• 43:34Krishna Choudhary?

  Yes.

• 43:35Lester Nare?

  And that allows us to get the after because we have such a precise understanding of the stars and their positions.

• 43:41Krishna Choudhary?

  And their positions.

• 43:42Lester Nare?

  So it's almost like they're a ruler.

• 43:43Krishna Choudhary?

  Yeah.

• 43:43Lester Nare?

  The stars become a ruler by which we're measuring.

• 43:45Krishna Choudhary?

  And, and it's extremely precise. And that's how you get that precision in such a short time.

• 43:49Lester Nare?

  Yeah.

• 43:50Krishna Choudhary?

  If we just waited for Goldstone radar to keep going, we'd have to wait for it to come back. And then like, you know, that's just going to take forever.

• 43:57Lester Nare?

  That makes so much sense.

• 43:58Krishna Choudhary?

  If we supplement that with this really tight astronomical data, right? And then we run the models on it, then we can get the error rate down to where we can really say, yep, 11 micrometers per second is how much we took away from that asteroid, which means that its year, which is about two years, is going to be shorter by 0.15 seconds. And that's how we get that data.

• 44:19Lester Nare?

  That's so fascinating.

• 44:20Krishna Choudhary?

  That's how we, that's how we conclude that number.

• 44:22Lester Nare?

  Right.

• 44:22Krishna Choudhary?

  But it's hard work.

• 44:23Lester Nare?

  It's real, and it's a really creative solution to the time problem. Because you, you, it's like you have a little, you know, what is it? A necessity breeds invention? And they're like, okay, we don't got time.

• 44:33Krishna Choudhary?

  We don't, yeah.

• 44:34Lester Nare?

  What are we going to do?

• 44:34Krishna Choudhary?

  Yeah.

• 44:35Lester Nare?

  Well, what if?

• 44:36Krishna Choudhary?

  Yeah.

• 44:37Lester Nare?

  And it worked.

• 44:37Krishna Choudhary?

  Very good.

• 44:38Lester Nare?

  Very good.

• 44:38Krishna Choudhary?

  And, and so now from there, we can actually calculate the momentum enhancement along the heliocentric path, not just the local path.

• 44:45Lester Nare?

  Yes.

• 44:45Krishna Choudhary?

  But how much boost did both of them get?

• 44:47Lester Nare?

  Yes.

• 44:48Krishna Choudhary?

  On their way around the, the sun.

• 44:50Lester Nare?

  Yeah.

• 44:51Krishna Choudhary?

  Given that. My, you know, kamikaze drone satellite had a certain momentum. How much momentum boost did they get? And the beta that we get is about two, a little bit more than two. So twice as much momentum was transferred to that system than what we put in because of all the

• 45:07Lester Nare?

  ejected that came out. The back. So basically, the amount of momentum we put in, that same amount was ejected out.

• 45:12Krishna Choudhary?

  Mm hmm. Yeah, yeah, I thought it was pretty cool.

• 45:15Lester Nare?

  That's very, that's very nice.

• 45:16Krishna Choudhary?

  It also confirms like the density of this moonlit. Yeah, it's about, it's significantly lower than solid silicate rock, which means that it's like highly porous. It's actually not like, just like normal rock. It's like a very light rock.

• 45:30Lester Nare?

  It's like the rock you are supposed to wash your feet with. What do they call it? Pum like?

• 45:33Krishna Choudhary?

  Yeah, yeah, pumice stone, exactly. Yeah, yeah, it's 1630 kilograms per meter cubed.

• 45:39Lester Nare?

  Okay.

• 45:39Krishna Choudhary?

  Which is, so it's still gonna, um, it's still gonna sink in water. Water is a thousand kilograms per meter cubed. But you know, it's not that much more dense than water.

• 45:48Lester Nare?

  I just want to note, we just implemented a latex notation in our script notes.

• 45:53Krishna Choudhary?

  Yeah, it's pretty great.

• 45:54Lester Nare?

  Uh, which.

• 45:55Krishna Choudhary?

  Look at that plus and minus sign.

• 45:56Lester Nare?

  Displays a real formula.

• 45:57Krishna Choudhary?

  Yeah.

• 45:58Lester Nare?

  And I'm looking at this and you just riffed that off the cuff so quick.

• 46:01Krishna Choudhary?

  Yeah, because I can actually read it. Also, the, the beta with the under, like, there's a subscript, you know? Beta H along, because that's the beta heliospheric along the path. Before I had to like read the latex where it would go slash B E T A underscore. Parenthesis, squiggly parentheses, H, oh my God.

• 46:24Lester Nare?

  It's now it's in English.

• 46:25Krishna Choudhary?

  Yeah, now it's in actual English, very good. So broader implications.

• 46:30Lester Nare?

  Yes.

• 46:30Krishna Choudhary?

  We've got a valid measurement of beta.

• 46:32Lester Nare?

  Yes.

• 46:33Krishna Choudhary?

  Now that validates this kinetic impactor. That means that like in the future, we're not blowing things up.

• 46:37Lester Nare?

  Right.

• 46:38Krishna Choudhary?

  Like if we're gonna get twice the momentum enhancement.

• 46:40Lester Nare?

  Yeah.

• 46:41Krishna Choudhary?

  That means like, you know, all we need to really toggle is how big is the payload?

• 46:44Lester Nare?

  Yep.

• 46:44Krishna Choudhary?

  Which we can. We can toggle as much as we want, right? We can do multiple hits if we need to.

• 46:50Lester Nare?

  Yeah.

• 46:50Krishna Choudhary?

  And, and then, um, like, how fast are we moving? How big is the payload? How fast are we moving? And then multiple if we need it.

• 46:58Lester Nare?

  Right.

• 46:58Krishna Choudhary?

  Right? So this is now like a strategic advantage for us. It confirms that we can actually do this.

• 47:03Lester Nare?

  All the things we've seen in all these asteroid movies, some of which they just tried to send to put a drill. I think Armageddon, they tried to drill.

• 47:10Krishna Choudhary?

  Yeah.

• 47:10Lester Nare?

  And then blow it up.

• 47:11Krishna Choudhary?

  Yeah.

• 47:11Lester Nare?

  But then it just created thousands of pieces that still came.

• 47:14Krishna Choudhary?

  We're not doing that.

• 47:15Lester Nare?

  We're not doing that.

• 47:15Krishna Choudhary?

  Armageddon was incorrect.

• 47:16Lester Nare?

  Right?

• 47:17Krishna Choudhary?

  It's less, okay, it's less Hollywood-esque.

• 47:19Lester Nare?

  Yeah.

• 47:19Krishna Choudhary?

  There's no big nuclear explosions in space, but I just want to live.

• 47:23Lester Nare?

  Yeah, right.

• 47:24Krishna Choudhary?

  Right?

• 47:24Lester Nare?

  And we just need to nudge it. We just need to hit it.

• 47:26Krishna Choudhary?

  Yeah.

• 47:27Lester Nare?

  Side swipe it a little.

• 47:27Krishna Choudhary?

  Yeah, yeah, exactly.

• 47:29Lester Nare?

  Go in the other direction.

• 47:30Krishna Choudhary?

  Yeah, it's like a hockey puck, right? Just like, you know, just move it out of the way. Um, the near earth orbiter surveyor.

• 47:36Lester Nare?

  Yes.

• 47:36Krishna Choudhary?

  So this thing is NASA's next generation space-based infrared telescope. It's going to launch in 2027 in September, and it's designed to detect dark asteroids that are not visible by ground-based optical telescopes. For whatever reason, sometimes they're coming right at us from the sun. They're like in our orbit, things like that. So that's what this surveyor is going to do. That's going to give us more and more, you know, just in case some, some random crap happens.

• 47:59Lester Nare?

  I want to note that the 2013 Russia example that we talked about, because some of the question might be like, oh, planetary defense, we already know where all this stuff is, so we'll be fine anyway. That 2013 one came.

• 48:12Krishna Choudhary?

  Came out of nowhere.

• 48:12Lester Nare?

  It came out of nowhere and no one saw it.

• 48:14Krishna Choudhary?

  Yeah, and it was super alarming because I was like, I thought you guys had this together.

• 48:18Lester Nare?

  Right. And, and so planetary defense is not, we are a single point of failure.

• 48:22Krishna Choudhary?

  Yeah, like, like.

• 48:23Lester Nare?

  Species.

• 48:24Krishna Choudhary?

  I think, I think we have, I think NASA says that we've got all of the, um, all of the like really bad ones, like the dinosaur impact type ones, probably under control, but still like, like the one, the one on Russia, right? If, if that had not exploded out in.

• 48:41Lester Nare?

  Right.

• 48:43Krishna Choudhary?

  Ten, you know, whatever the altitude, like, that could have been really bad.

• 48:47Lester Nare?

  That could have been really bad.

• 48:48Krishna Choudhary?

  That could have taken out a small city.

• 48:49Lester Nare?

  Yeah.

• 48:50Krishna Choudhary?

  I don't want that either.

• 48:51Lester Nare?

  Right, right. Because the other flip side of this, which is just sort of an interesting dynamic in the world we live in today, which is relevant, is, I think this is actually the, um, this is the plot to Paradise, the Hulu show.

• 49:07Krishna Choudhary?

  Yeah.

• 49:08Lester Nare?

  Where it was an external object that was coming in, um, like a comet or an asteroid, and it triggered nuclear war because of its, like, as extensible context. So like, if something has impact and then there's misinformation, like, there's not good information sharing about what the thingy.

• 49:26Krishna Choudhary?

  Yeah, I mean, we're going to war for a lot less.

• 49:29Lester Nare?

  Right, so it just creates, you know, planetary defense is really important. We, you know, we are not well-equipped to survive a massive impact.

• 49:39Krishna Choudhary?

  No, so I'd rather not have it.

• 49:41Lester Nare?

  And we now have at least a baseline to be able to provide the defense industry the answer when they all get around that round table and they have an extinction level event from a celestial or cosmic object had its earth. The NASA scientists have the math now.

• 49:56Krishna Choudhary?

  Exactly, yeah. And one last thing that I want to highlight is that this is an international effort, right? Planetary defense, we're on the same planet, the ESA has HIRA, which is arriving at Didymos and Dimorphos. It's actually going to map out the DART impact crater. And it's going to directly measure Dimorphos' mass via radio tracking and really refine those values of delta V and then beta subsequently and so on and so forth. So it's, it's really an international effort that we've just sort of created a lab test bed in space.

• 50:32Lester Nare?

  Right.

• 50:33Krishna Choudhary?

  Of Didius and Dimorphos, this binary asteroid system.

• 50:37Krishna Choudhary?

  It's very cool.

• 50:38Lester Nare?

  Look, any space story you know I'm in on, I had, I owned both Armageddon and Deep Impact on VHS when they both came out in whatever it was, 1997. I still think it's hilarious to think that Bruce Willis and Ben Affleck, who were a bunch of guys who worked on an oil rig,

• 50:54Krishna Choudhary?

  Yeah.

• 50:54Lester Nare?

  were the only people who could save Earth and had to learn how to become astronauts.

• 50:58Krishna Choudhary?

  Right.

• 50:58Lester Nare?

  And apparently it was easier to train people who worked in an oil rig to be astronauts than it was to train

• 51:02Krishna Choudhary?

  Yeah.

• 51:03Lester Nare?

  astronauts how to drill on this thing.

• 51:05Krishna Choudhary?

  Yeah.

• 51:05Lester Nare?

  Ben Affleck did, and if you, the, one of the, if you're a movie buff, I think in the, the extra scenes, whatever, the, when, we used to have the DVDs with the extra stuff. Oh, the director, like the director's cut where they would voice over while it was playing. He was just taking the piss about how ridiculous the plot was to the movie. The whole time.

• 51:24Krishna Choudhary?

  That makes sense.

• 51:25Lester Nare?

  Very, very cool story. DART, our planetary defense story today. And the key piece to this was the ability to calculate the heliocentric momentum change.

• 51:36Krishna Choudhary?

  It's really, it's, it's really a precision physics and precision astronomy story. More than anything else.

• 51:43Lester Nare?

  Right.

• 51:43Krishna Choudhary?

  You know?

• 51:44Lester Nare?

  But in the media, we like to say planetary defense.

• 51:46Krishna Choudhary?

  Yeah, yeah.

• 51:47Lester Nare?

  It's, what is the, how do we make this militarized?

• 51:49Krishna Choudhary?

  Yeah. But I just, I just love the, like, you know, for, for astronomers, like, this kind of precision is, like, unprecedented, right? They're like plus or minus 10,000 kilometers, you know?

• 52:01Lester Nare?

  Right.

• 52:01Krishna Choudhary?

  Type of guys.

• 52:02Lester Nare?

  Right.

• 52:02Krishna Choudhary?

  So.

• 52:04Lester Nare?

  And, and this, and just to recap, this was in Science Advances. Came out, uh, March 5th, March 6th. Uh, University of Illinois Urbana-Champaign, which has been a, a key institution we've talked about quite a bit on the pod. Also, NASA JPL, uh, Johns Hopkins Applied Physics Lab, uh, and a few European universities, uh, in collaboration, as you were just mentioning, from the ESA side. Really fantastic story. We're gonna wrap up on the episode for the day. However, we have one, uh, we have two things. One, we need our comment, which we did not write out in our script notes.

• 52:44Krishna Choudhary?

  Oh, no, why do you, no, we did, it was, um,

• 52:46Lester Nare?

  Oh, yes.

• 52:46Krishna Choudhary?

  Why do you think the Russians have so many dash cams?

• 52:49Lester Nare?

  Oh, yes, yes, yes. So if you're still listening, an hour in, because we are now not doing two and a half hour episodes, we're doing multiple, more bite sized, more digestible episodes that are focused about what's to talk about. So, why do you think they have so many dash cams? And we do want to do one correction from episode 29, which was from the rundown related to the research study about the Neanderthal human mating bias. We really appreciate all of the comments from folks on a variety of platforms on that story. Part of the challenges with the rundown, it is not a main focus, so we don't necessarily get into the weeds as much. We used some imprecise language in that segment, and the study itself was really just focused on mating bias.

• 53:34Lester Nare?

  There was a conversation about the difference between consensual and non-consensual. That was not in the purview of the study itself, and so we appreciate that feedback. We will keep that in mind in terms of making sure we are much more attuned and accurate as we cover things, even if it's in the rundown and not a main story. So we really appreciate that feedback from you guys. I am your host, Lester Nare, joined as always by my co-host and our resident PhD, who is not a planetary defense researcher.

• 54:06Krishna Choudhary?

  No, just a measly grad student.

• 54:10Lester Nare?

  We'll catch you guys for the next episode this week.