How scientists measured DART’s effect on an asteroid’s solar orbit

31:36>> I see. >> Which means that I I need to figure out a beta for the entire system, not just what I had figured out before, which is just the little moon, >> right? >> Around this. >> Yes, that makes sense. Because because ultimately from a planetary defense perspective, >> that's what matters. You care about the whole system. >> Yeah. Yeah. Yeah. That's what >> And being able to change the whole system. >> The whole system. >> But in order to do so, you need to understand the component parts component parts necessary to be able to impart that level of change on the whole system. >> Exactly. >> Yeah. And to tell you just how hard that is to do, >> right? >> Um the heliocentric velocity, this is something that I covered a little bit earlier. The system moves at 23 km/s

32:18>> and I'm trying to detect I'm trying to detect a change that is less than 1 millimeter per second. >> This thing is moving at 26 km/s and I need >> 23 20 >> sorry yeah 23 km/s. This thing is moving at 23 km/s. >> Yes. >> And that velocity is going to change by a millimeter per second. actually less >> this to that extent that's several orders of magnitude. A millimeter is a a thousandth of a meter which is a thousandth of a kilometer. So this is >> about 10 millionth. >> Yeah. >> One part in 10 million. >> Yeah. >> Is what I'm trying to sense for an asteroid that is millions of miles away.

32:59>> Uh we like to say this is non-trivial. >> This is this is extremely non-trivial. Right. >> Yeah. >> Like to make that measurement. This is another lesson in again some of our favorite topics on the podcast. Precision measurement, >> right? That's such a key. It's We have a toolbox in science with hammer, screwdriver. Some tools are more useful than others. Yeah. >> Some tools you use all the time, like a hammer. There's a lot of things you can do with a hammer. >> Laser is the thing in physics. You >> see, put a laser in. Yeah. Whatever. But but I 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

33:41able to do so >> in a robust enough way. Yeah. >> Um and this is a measurement challenge. Speaking of measurement challenges, in our uh first nine minutes of our appearance on the Dave Chang uh show, which is on Netflix, check it out, was spent on the double slit experiment, which is a measurement problem. >> Yeah, that is a measurement problem. That that completely caught me off guard cuz like we just got there and he was like, >> "What about the 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 here >> and he he's also quite quite sharp. I was >> Yeah, dude. He he remembered so much. >> He's quite sharp on you. >> Yeah, that was that was really cool.

34:22>> But the measurement problem is >> measurement problem. And this is where this particular paper comes in. It's measuring this unmeasurable 1 mm/s actually a lot less >> change in a 23 km/s object >> that is millions of miles away. 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. >> Jesus. >> Okay. Out of 26 km/s. >> Okay. And what this means to just give you a sense of scale. >> Yes. >> So that asteroid system goes around the earth every 770 days. So that's about 2

35:04years. Mhm. >> And this tiny change in velocity means that the 2 years of orbit has been shortened by 0.15 seconds. >> Oh my goodness. >> 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. >> That's incred and so there's there's 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 >> and and that's what we're going to get into next. >> And then the second piece is now we then have a reference point to be able to say

35:44how much do we need to scale up the because we just sent a small little thing. >> We didn't send a big old cuz also getting payloads into space is expensive and costs money and we don't like to spend too much money now on fundamental science stuff. Um, but now you could go to the the joint chiefs and say we're going to need a 100,000 megat ton X in order to get the level of momentum. But we just have a baseline now. >> Yeah, we have we have the numbers now. Right. >> Right. So in order to in order to make that detection, right? So 11 microns per second. >> Mhm. >> Is the difference between before and after before the explos before the impact and after the impact. Before the impact, it was going at about 26 23 km/s, right? And after the impact, it's

36:27still going at 23 km. >> This is like in the hypersonic velocity like area. >> No, this is not even hypersonic. This is way >> way way. Yeah. Like uh the speed of sound is 343 m/s. So.3 m/s. Okay. >> Okay. This thing has 23. So that's what um 3 >> * 20 60 times about 60 times the speed of sound. Okay. Hypersonic is five. So five and we're happy. >> So we're in UAP land right now. >> 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

37:08after. >> Mhm. >> Before we get into the after. >> Mhm. >> 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/s and then I say oh he decreased his he decreased his um speed by003 km/s. Well I'd need to know what the initial thing was right otherwise like how do you I could just be going like 71. 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

37:49to make that subtraction. That's a really good point. >> We don't have like the tools in physics where I can like do destructive 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. >> So, so the point being we need to measure it before this. We need to measure before we do anything. >> Yeah. >> And in that measurement needs to be very very good in >> very very precise down to the micrometer level precise. Yes. >> And the way they did that was so this system Dimus and Dorphus 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

38:30>> with uh 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 because we have this historical data that has captured pictures over time.