Answering Your Questions - Episode #2

[@JaapvanderVelde]

"If you are like a 170 kilogrammes..." - is this the result of Scott not using kg for everyday use, or does he have an exceedingly heavy group of friends/family?

[@TheAnoniemo]

He does live in the US...

[@Релёкс84]

@@TheAnoniemo Which is consistent with either explanation

[@Krasnoo]

@@TheAnoniemo You need to remember that the US of A is on the wrong measurement system of the world. Imperial system sucks.

[@dedasdude]

but kerbal uses SI system, which he is used to. He is just taking a dig at the average american :D

[@TheAnoniemo]

@@Релёкс84 I meant to mock the average weight of a US person, but I see now how it could be read both ways.

[@scarletlightning565]

SmarterEveryDay has a video where he gets a tour of ULA by the CEO and they talk a lot about the new isogrid designs for Vulcan

[@ilikeyourname4807]

The new one is an orthogrid

[@JJRicks]

I captioned that video :D

[@emmanotsostrong]

@@JJRicks Thank you for your service. That was a really long video; I can't imagine how long that would take to caption.

[@JJRicks]

@@emmanotsostrong Took two days, lots of research was done into friction stir welding and other stuff they mentioned just so I could get the spelling right but yea it was definitely one heck of a project 👍

[@SpydersByte]

I was going to mention that as well, it looks like that mayve been where he got some of that footage

[@fromagefrizzbizz9377]

Perhaps the best way to explain tidal forces, part of microgravity in one object swinging by another (especially in a stable orbit) is to note that the true zero gravity is at the centre of mass. Anything "below" the centre of mass is travelling a bit too slowly to remain in orbit at that altitude, and anything above the centre of mass, is travelling too fast for orbit at that altitude. Which means that the former is trying to fall down towards the other body, and the latter is trying to fall *up* away from the other body- a gradient of gravitational forces, with zero at the centre of mass.. The consequence is that if you tried to orbit something long and thin like a crowbar or a dumbbell, eventually the object will orient itself so that it's perpendicular to the orbit, rotating exactly in sync with the orbital period. In Larry Niven's Neutron star, the first attempt to perform a close-in pass to a neutron star was done by a pair (a husband and wife), in an indestructable space ship (A General Products #2 hull - long and skinny, sold to humans by Pierson Puppeteers - you have to read the "Known Space" series to learn more). The first attempt resulted in the ship returning with nothing remaining of the pilots but a bloody smear at one end of the ship. The intrepid volunteer to the second attempt started to to see the ship irresistably re-orienting to vertical, and some objects whizziing either direction and smashing into the ends. He abruptly realized what was happening, and managed to wedge himself into the ship at the exact centre of gravity for the closest part of the pass. He was narrating thruout, estimating that the effective gravity at either end was possibly 10000 Gs or more in opposite directions, and practically passed out because *he* was being stretched too by several gravities in either direction. One of Niven's friends was a highly renowned gravitational physicist -Dr. Robert L Forward. Amongst many things that Forward did in his career was build the first attempt to detect gravitational waves - he died in the 1970s, but his work culminated in LIGO. Forward influenced much of Niven's work, and you can damn betcha that all of Niven's work involving orbits had gravitational math behind them that was perfect, not just in concept, but equation-wise too. If you want to understand gravity outside of the equations and understand its implications, there's nothing better than Niven's "Descent of Anansi", and "Smoke Ring". Real mind-benders. But the math *works*. If you understand *those* in your gut, you know gravity. Dr. Forward wrote a number of SciFi books himself. Hard SciFi, where the physics arewas *perfect*. Maybe not in other things - I mean, hell, is it even remotely possible for sentient creatures to live on a Neutron Star? But, hey, they're great stories.

[@danieljensen2626]

Re: Lightningmaps.org It's a homegrown network of VLF sensors ("Very low frequency" 3-30 kHz). Basically whenever you get a lightning strike to ground or a similar discharge in the cloud a significant amount of charge is moved, which changes the electric field. That electric field change will induce a charge on an electrode (basically any bit of metal, flat plates are common), and then you use a circuit called a charge amplifier to convert that to a voltage, and then you digitize that signal. By looking at the relative timing of those recorded pulses at different stations you can work out where the pulse must have come from.

[@herbertkeithmiller]

Regarding zero G and orbits. Another way to think of 0 gravity in the spacecraft in orbit around the Earth is that the gravity of the planet is pulling you down with the same amount of force that the centrical effect is trying to fling you away from the planet (from The reference frame of an object In orbit from the reference frame of an outside observer you are trying to travel in straight line) and the 2 perfectly balance out along the centerline of your orbit. If you had a long spacecraft with one end pointing towards the center of the Earth and the other end directly away from the centre of the planet by moving away from the centre line you would begin to experience a pull towards whichever end of the spacecraft you move towards. This doesn't change when you're on the way to the moon your just in a different orbit. Technically no matter where you go you're under the Gravitational influence of some object no matter how distant. The mathematics work out to always balance the 2 forces out along the centerline of whatever orbit you happen to be in.

[@ritaloy8338]

I had a job where I was a contractor who changed out air filters. One of our facilities that I had to work at was at was the McDonnell Douglas facility in Huntington Beach CA. I would be required to go through the machining area where they were matching the the panels to be made later for the rocket boosters. It was for me very interesting to see the machining process going on at that time.

[@Christopher28fair]

I wanted to add a few comments to the first question, about the effects of gravity when an astronaut is trasversing from the Earth to the moon. I would offer that gravity is always in effect, whether the Earth's, or the moon's, or the sun's, or some distant star, though with different strengths. To get to the moon from Earth, the spacecraft has imparted a force to change it's orbital direction, and from that it also acquires a change of inertia that will stay in force until something else changes it again (like getting very close to the moon, or another engine burn). The ship and the astronauts are still under the force of gravity from all three bodies, but the inertia of the ship has overcome those forces because of the engine burn. At the moment the ship changes its inertia, the astronauts will be pushed in the opposite direction from the force of the engine. (the ship will also be accelerating, here) until they bump into the back of the ship. At engine cut-off, the force imparted by the engine stops, and they're no longer pinned to the ship. They're now traveling in the new direction along with the ship. All the gravitational forces are still in effect, and always have been, but they've been overcome by the force of the engine. Two; I also wanted to add two cents to the flip/descent question. Look at the Starship on its way down from 10 kilometers. It's flying horizontally, using its fins to maintain position, but also to help slow it's descent. It probably has a maximum speed in that configuration, slowed by the air in the atmosphere. If it did the flip maneuver from 10 kilometers up, it would be descending on it's narrowest profile, and would gain a much higher velocity as it descended, as well as becoming more and more difficult to control because of that higher speed. Then, as Scott said, it would need much more fuel to arrest it's descent.

[@Jack-dh2ws]

I’m an aerospace engineering major, and at my school we have 3 aerospace structure classes in addition to normal structure classes like mechanics of materials, statics, etc. it’s a huge part of what aerospace engineers do.

[@ace38karr]

Jack that's a cool field to get in. If you can answer a quick of mine it would be awesome. Wieght and mass how are they different and the same? Sorry if it is silly question just my mind gets confused about it.

[@dsdy1205]

@@ace38karr weight is the force that a gravitational field exerts on an object which has a certain mass. Depending on the strength of the gravitational field, an object with a single mass can have very different weights.

[@ace38karr]

So what is mass? And how is measured?

[@dsdy1205]

@@ace38karr well, I don't know the proper way to explain it, but loosely speaking it's the measure of how much inertia an object has, or how much it resists motion. If you apply a certain force to an object, if it has a higher mass it accelerates less. and so forth. We measure it by measuring the object's weight in a gravitational field of known strength, and then calculating backwards to find the mass. For really really big objects, they generate enough of their own gravitational field that we can just measure the strength of that and calculate directly.

[@ace38karr]

Thank you for helping start to wrap my mind around this concept. It helped

[@danielleriley2796]

8:45. SpaceX flip manoeuvre. The simple answer is it doesn’t really matter for reliability of the manoeuvre working as the current failures can’t be solved with altitude. The real answer is that the entire belly flop and flip manoeuvre is required for Mars and since the drag is proportional to velocity and atmospheric density then to still get drag at lower velocities you need more air so every cm lower in the atmosphere is mor time for more drag to affect the velocity and there is more air available to increase that effect. Remember the proposed landing zones for the initial flight are at the lowest points on Mars squeezing every bit of atmospheric density available out of the planet. It’s a computer controlled manoeuvre. The height it’s initiated at doesn’t effect it’s outcome, well there is a min altitude. So once it’s figured out and the right equipment is set up the right way and all being run by the right computer program, that’s what this test program is figuring out amongst other things, then the StarShip will flip as low as possible to get the most opportunity to use the minimal drag available on Mars.

[@FectacularSpail]

I love your answer to the Fermi Paradox/Great Filter question, because there's a book I like called Restricted Fantasies, by Kevin Kneupper that goes in the same direction. It's maybe a dozen or so short stories, all mostly based around the idea of humans developing basically Matrix level simulation technology. In one story, humans have finally gotten out into the galaxy and explored other star systems, and they've discovered several advanced civilizations, but haven't actually made "contact" with any of them, because what they find is just the abandoned remnants of a technological society, but all of the aliens are just being kept alive by machines inside their individual simulation pods.

[@Alcopop100]

I don't always understand what you are talking about but I'm addicted to your videos. Still learning at 73, so thanks.

[@dsdy1205]

4:11 It's important to note that in those cases, since protons and antiprotons are collections of 3 quarks, what's actually happening is that one of the quarks / antiquarks in each baryon completely annihilates giving only energy, and the remaining 4 quarks pair up and fly off.

[@jonahcovarrubias8132]

How did you learn about subatomic particles?

[@dsdy1205]

@@jonahcovarrubias8132 I read about them

[@replica1052]

the smallest dimension possible are wawes interacting from opposite ends of an infinite universe

[@frankowalker4662]

Aww, how sweet that the last 4 live happily ever after. :)

[@dsdy1205]

@@frankowalker4662 Well they don't really, mesons only last for a short while before they too decay into pure photons. Sorry :(

[@janos71]

I think a good addition to the first answer is this: when you jump, you feel weightless on the way up and down, even if you usually just refer to the second part as falling. edit: a more appropriate way of saying it would probably be something like, "From the moment your feet leave the ground to the moment you land, you are technically free falling."

[@fewwiggle]

I'd change that to "On the way up AFTER you are airborne, i.e., no longer pushing against the ground"

[@janos71]

@@fewwiggle Yes ;D a while after making the comment, I also came to the conclusion that it would probably be better to say tomething like: "From the moment your feet leave the ground to the moment you land You technically free falling. "

[@evanjames575]

Also, at any point that you are en route to the moon, you’re still sitting in a circular orbit around the earth. Even if we tend to imagine a figure 8, with movement towards the moon.

[@fewwiggle]

@@evanjames575 Well "en route" is a bit vague -- won't your path curve more towards the moon (as opposed to a "circular" path about the earth) as you get very near to going into an orbit about the moon? Also, isn't the better term for the path "elliptical" (vs being "circular")? A purely "circular" orbit is quite rare isn't it?

[@Gerard1971]

The first question was really interesting, I didn't completely understand this myself, and your answer helped a lot, but I also felt it was somewhat incomplete, so I did look in to and I think I can explain it better. The 'matching gravity with your forward velocity' in the question is only required to maintain the orbit, it is not what is giving you micro gravity. Also, when the orbit is not circular, the forward velocity is also going to vary in the orbit. If you are below "obitual speed" you are still freefalling, but your altitude will also go down. If gravity is the only force that is applied to both you and the vehicle you're in, then you're in freefall and thus "weightless", even if the vehicle is moving away from the largest gravity source, like in the question a spaceship going to the moon. You could also argue that the spaceship going to the moon is still on orbit around earth, just a very elliptical orbit. Gravity is not giving you weight, gravity will just make you accelerate towards the largest center of mass, it is the floor that you're standing on that is applying a force equal and opposite of gravity on you that is giving you weight. As soon you are not touching the floor, you are weightless. If you stand on a bathroom scale that is glued to your shoes, as soon as you jump up and the scale is no longer touching the floor, it will indicate zero: you are in freefall, initially moving up, and then down again until the scale hits the floor again. How did I do? :-)

[@HylanderSB]

I agree with Scott’s “answer” to the Fermi paradox. I think the most advanced civilizations would also be the most “quiet” as they have developed the most efficient means of energy use for their purposes. What kind of communications is more efficient, for example? Something that radiates in all directions or is focused towards one destination? Which is easier to detect if you aren’t the intended target? Would their communication network even involve energy traveling at distance? Though now that I think of it, shouldn’t there be civilizations like us, in transition? Yeah, it’s not like the only ones we could find are the most advanced. We’re findable if you’re listening in the radio frequencies and we’re just learning what “advanced” could be.

[@louisesmalling]

I love content that sends me out to investigate new questions. Thanks!

[@clavo3352]

Scott; you are a fun guy to listen to. You deserve one of those "Most interesting guy" beer commercials!

[@giantnanomachine]

So the best defense during an alien invasion would be “hey, want to try this oculus rift?”

[@ezequieltellez9082]

Yeah... or minecraft :S

[@lordbaysel3135]

I would try with "Have you heard about Nihilism?"

[@timmurphy5541]

Check out Red Dwarf: Better than Life.

[@moneygrip4464]

@@ezequieltellez9082 error=r⅘is a for that bit

[@timmurphy5541]

@@RobertLutece909 Red dwarf? Better than life?

[@connorhart2793]

Firstly, I love these videos, your answers are super insightful. Secondly, I believe intelligent life is both too curious to turn inward and never explore as well as too smart to explore so obviously that they are noticed by others. That fine line is the same fine line SETI is in search of and they will be searching for slip ups not overt signals saying hello.

[@lotophagi711]

I worked with a mathematician who worked on Bluestreak back in the 50s. Interesting stories but he was tasked with working out changes in resonant patterns as the fuel tanks emptied. He said it was extremely difficult to get the structure light enough and still not oil can as the tanks emptied. He mentioned he need to use gas to keep them inflated.

[@simjans7633]

Yes! Navigating in space independent of the Earth fascinates me and I'd love for you to talk about it!

[@petergerdes1094]

Microgravity is a misleading term (not your fault Scott I know). It leads to people thinking that the reason astronauts experience so little gravity is because gravity is so weak up there not because they are free falling. The only people who understand the distinction the term microgravity is trying to draw aren't in danger of making the mistake it's designed to prevent against (i.e. who realize the gravity field is slightly non-uniform)

[@moritznadler9001]

Exactly my thoughts, too.. I am always a little annoyed when I hear/read this "it is not zero gravity it is microgravity!" nonsense in popular science shows/articles ...

[@petergerdes1094]

@@moritznadler9001 Yes, as if we don't use zero all the time to mean small enough to ignore for the current purposes.

[@yahccs1]

I thought they changed 'zero-g' to microgravity because the net effect between the astronaut and the space station or spacecraft (when you subtract the motion of the craft to get the relative motion of the astronaut in it) is not quite zero because the tiny mass of the station or craft has its own very tiny gravitational effect and the difference in the gravity of Earth (or other planet/moon) from one end to the other is not zero - and there will be a larger apparent gravity when the station boosts it orbit and accelerates slightly. Even with all these it's probably still such a tiny effect it seems like apparent zero-g. Yes of course 'freefall' is the best way to describe it! I suppose they [ISS astronauts and cosmonauts] could feel the true gravity at that point if they were standing on top of a 240 mile tall pole stretching up from the earth if it were possible to make one!! Not much less than the gravity at the surface... and they wouldn't feel much lighter as they'd be wearing quite a heavy space suit!!

[@AndrewBlucher]

Sorry Peter. The entire gravity field is nonuniform. The only place it can be uniform is where it's zero, and it's nonzero throughout the universe.

[@petergerdes1094]

@@AndrewBlucher Yes, I know but that's not the point. The term microgravity suggests the reason that astronauts float is that the gravity field is small. It doesn't help indicate that it's non-uniform.

[@jameskelly1680]

The Larry Niven story mentioned is a really good explanation of tidal forces. Highly recommended.

[@sntslilhlpr6601]

The book has a lot of great stories too. Definitely worth a read.

[@sharpfang]

I think you're only adding confusion to the question with the moon transfer. You're in freefall not only in circular orbit - you're in microgravity in any orbit, including elliptical or even so degenerate elliptical it's a hyperbolic fly-by with escape at the end - or one that is a blend of two elliptical orbits around two bodies, e.g. getting captured by the moon from an elliptical orbit around Earth. At every single point the acceleration/deceleration of the craft and everything on it matches the local sum of gravities (because it's their direct result) so the astronauts are in freefall. Only during propulsive maneuvers one feels the acceleration. You could say freefall is the natural state, and the fact you experience gravity on Earth is because of your propulsive maneuver of lithobraking against Earth surface with your feet. Yep, in orbital mechanics terms you're a statite using lithobraking for station-keeping on Earth surface.

[@GargantuanMonster]

I was thinking the same. I would also emphasize the fact that the reason you're not feeling the acceleration of the craft due to gravity, is because you're experiencing the exact same acceleration, so nothing is pushing on your body inside the spacecraft. When you fire your rockets, the rockets push on the craft, and eventually the craft will push on you, at which point you'll feel pushed. If you stand up and jump, as soon as your feet leave the ground you're in "freefall" even though you're still moving upwards. There is no change at the crest of the jump, you only feel a force again when your feet touch the ground. Jump high enough, and you can freefall to the moon.

[@toweri_li]

@@GargantuanMonster to Jump to the moon, you'd need to jump so fast that you'll reach the 2nd Cosmic Velocity, the Earth Escape Velocity, 11.2 km/sec. Do that, and you can enjoy the free fall for the rest of your life. ;)

[@gunslinger434]

I sincerely enjoy these Q & A sessions! Thanks Scott!

[@jimmyryan5880]

Thank you for "trilaterate" I had a small argument with my thesis superviser over this. He never heard of the word and kept trying to correct it to triangulate.

[@danieljensen2626]

Lol, I literally work with lightning location systems and we totally all call it triangulation, I never knew there was another word depending on what measurement you use!

[@travcollier]

@@danieljensen2626 Totally believable. I made an acoustic localization system using time-difference-of-arrival (TDOA) and went through a lot of the literature because the math is similar. Terminology is very inconsistent. I'm not even sure TDOA is technically multilateration. Each pair of receivers locate the source to a hyperbolic surface. Anyways, I was guessing lightning detection works by TDOA too... Do the different sites need well synchronized clocks? Another option is each site having multiple receivers synchronized with each other so they can compute the direction to the strike, then you use triangulation.

[@naidanac1]

The fascinating closing question/answer delves deep into things like philosophy and outlook - I'm all for these types of discussions, and hope Scott can get into that stuff more!

[@remicaron3191]

Your Fermi solution is the best I've heard yet. I'm sure everyone will hate it because it doesn't involve us conquering the universe but from the information we have at the moment it's by far the most plausible considering we are wasting resources on all sorts of things while our planet is dying and most of us haven't even noticed yet. Great stuff

[@JaapvanderVelde]

8:32 isn't the simple answer that they need to light the engines for the flip and for the landing? So, if you flip sooner, you're running the engines for longer. I think it's a fair question to ask why not add a few hundred more meters, to allow for a bit more correction - but I'd say the answer is that SpaceX is confident they get it right at the short distance. The problem has been engines not lighting or not running correctly, and no amount of extra height would have fixed that problem.

[@zacm.2342]

If anything flipping sooner would make the consequences of an engine relight failure and such worse wouldn't it

[@Dappdude]

On the starship question: the flaps have been designed to provide control while belly flopping, and they don't work in vertical orientation. If it were to flip vertical at altitude, you'd need another means of control like grid fins or vectoring engines.

[@brynclarke1746]

They already have vectoring engines, it is controllable vertically - though going tail-first at high speeds may cause aerodynamic stability problems

[@Dappdude]

@@brynclarke1746 and running engines from high up would take a lot of propellant

[@Nivola1953]

Maybe the solution to the Fermi paradox is just distance and therefore also volume dilution of signals. The closest star is > 4 LY away and there are only 63 stars with 5 parsecs (> 16 LY) within a volume of about 500 pc^3. LGM will have to point a powerful radio beam in the right place at the right time, to communicate. Why aren’t we trying to communicate with “them”? This is in the SETI article in Wikipedia “A significant problem is the vastness of space. Despite piggybacking on the world's most sensitive radio telescope, Charles Stuart Bowyer said, the instrument could not detect random radio noise emanating from a civilization like ours, which has been leaking radio and TV signals for less than 100 years.” That also implies that LGM outside 100 LY haven’t received our signals yet.

[@Tim_88524]

8:17 Another thing besides what you already mentioned is that the flaps on Starship can only provide control in the horizontal fall because they aren't lifting surfaces and can only move up and down. So the only way to control Starship when it's vertical after the flip is though engine gimballing which means that (one of) the engines has to be on for the entire time, which would be very inefficient. Contrast this to Falcon 9, where the grid fins provide most of the control on descent and one engine is only lighted at the very end to cancel out the remaining velocity before it hits the landing area. This would also render the sloshing and no header tank needed argument of the questioner useless (it doesn't make sense anyways because the engines are needed for the initial flip).

[@chrisglen-smith7662]

Lightning "indicator" : If you can find a working old fashioned Neon indicator bulb, ground one side of it and connect a lets say 6ft length of wire to the other side up to the ceiling indoors then it will flash when lightning strikes within a certain range. Generally the range is sort and you can see the flash of the lightning directly but I think it's an interesting indication of the strength of the EMP from lightning. PS probably NOT a good idea to go outside and string a longer wire up a tree to increase you detection range!!!

[@TheBackyardChemist]

lol, I am sure it would make detection events much more noticable

[@ChecedRodgers]

Hi Scott, +1 to the idea of navigating in space by star tracking.

[@nicolatesla9429]

4:45 Scott basically descided the guy who asked the question was to be morbidly obese. 🤣

[@henrikoldcorn]

Eh, he probably misspoke, or doubled the mass to account for the matter+antimatter and then forgot he did it. It happens.

[@scottmanley]

Confused pounds and kilos in my head

[@d.t.4523]

@@scottmanley Most of the NFL players that line up in front of the quarterback are over 100 kilos. I was about 145 kilos, and kinda small for the position I played in school. Fly safe!

[@Automatic-Diaphragm]

@@d.t.4523 doesn't mean it's healthy

[@fcgHenden]

@@d.t.4523 Holy! You're more than two of me at 60!

[@ZPositive]

Holy moly this video is crammed full of knowledge. Please turn this into a habit, Scott!

[@jeromethiel4323]

Structural strength in rocketry is no trivial matter. For example, the V2 rocket kept blowing up on launch. And they had no cameras capable of filming fast enough or accurately enough to see why. So (as the story goes) Werner Von Braun and a colleague actually were close enough to visually see the outer skin rippling and buckling on a launch, and were able from those visual clues, make some structural changes to make the rocket actually fly. Nowadays, you have computers and things like finite element analysis to do that figuring out for you. Plus the ability to manufacture extremely well made objects, which means you can pare the weight down to the absolute minimum and still maintain the strength you need. Hell, without computers 3/4 of the things we take for granted in space flight nowadays would not be possible. And 3/4 is just a number i pulled out of my nether regions. It's probably higher than that. Even the Apollo program in the mid 60's used more computers than i knew about, till i started looking into it. And man, were those primitive number crunchers.

[@andrewcharlton4053]

Just to add to that part of structural integrity, the best way to visualise what's going on is to take a sheet of paper and hold it up. It'll flop and collapse. If you take another piece and sellotape it on the middle of the flat surface so it looks like a T then it'll not flop. This is what you do in engineering all the time. It's to do with second moment of area but that's the best visual trick for it.

[@Biomirth]

Aw, I loved the way you answered the last question on the Fermi Paradox. I mean, not only is it a good answer, but it is generously realistic and reflective.

[@australien6611]

What a likeable man 🤗 I couldn't talk "off the top of my head" for 10 minutes about anything

[@rogerstone3068]

Oh I could do that, easy. I was a teacher for 40 years. The trick is to manage to talk interesting stuff which is worth listening to, and Scott does that remarkably well.

[@rogerstone3068]

The Fermi Paradox question: nobody seems to consider WHY intelligent technological space-travelling beings would want to go exploring unknown worlds. It might look like you'd want to, because of the stage we're at just now; but look at what we actually DO. Imagine there's an ant-nest in the Russian tundra somewhere which achieves enlightened intelligence and asks itself the same question. "Is there other intelligent life on Earth? If there is, why hasn't it already arrived here and discovered us?" Well, there is, but it's too busy living in cities, having economic crises, fighting wars and stuff like that. Who is going to go out checking ants' nests 500 miles from anywhere, to see if they've become intelligent? Take a ride along any orbit on Google Earth, just cruising in a straight line, starting anywhere, going any direction, cruising about 250 metres up, and sit and watch for an hour. See how much human infrastructure you pass over, compared to open land where the nest of intelligent ants would simply go unnoticed. Even on farmland, would they be noticed? - and most of the planet is just wilderness. At some random point, 'ping', there's your ant nest. They make signals to the outside world in every way they can think of. Big radiating scent-trails, reaching out for huge distances, maybe 20 or even 30 yards from the nest. Nothing. They hold mass rallies when a million ants all get together and wave antennae in a coordinated pattern. Result? No reaction. They would, I'm sure, conclude that they are alone as the only intelligent colony on Earth. And yet we consider the Earth to be really densely infested with humans. The universe could be many orders of magnitude less densely populated with aliens, than our Earth is with humans, and they could be engaged in all manner of different-priority activities we can't imagine. Our weakly-radiating radio signals are of no more interest to them than the ants' scent patterns are to us.

[@serge00storms]

General Products takes no responsibility for any unusual gravitational effects.

[@GG-yr5ix]

We must remind you that further discussion regarding any purported incident regarding a General Products hull is covered in the non-disclosure section of the settlement agreement. Further discussion may incur substantial penalties. P. Pak, Attorney for General Products

[@robertmiller9735]

Or broadcast shutoff codes, or activation of a hyperdrive inside part of your starship. For antimatter, though, they'll pay up.

[@amichaelson]

Wonderful as always. Thanks Scott.

[@daar1113]

As for astronomical pictures taken from the ISS, from what I understand there are very few windows on the dorsal side of the station facing space. Most of the windows face Earth. There are plans to put another cupola on the space facing side but who knows if it will make it up there before decommissioning?

[@MegaKopfschmerzen]

Thanks for teaching me the word 'trilaterate'. I had been using 'triangulate' for both methods.

[@danuttall]

I am so looking forward to Scott's series on this channel on the structural engineering of rockets. Let the course begin!

[@ArifRWinandar]

"If you were like 170 kilograms..."

[@TheMonthlyJack]

American audience.

[@Schnurpsful]

my first thought was he included the extra mass needed to convert you into energy but then he added it back in... for those not knowing how heavy a typical human is in kg, 170 kg is roughly equal to 375 lbs.

[@australien6611]

@@TheMonthlyJack they only understand pounds for weight and football pitches for length

[@czerskip]

… then you definitely have a lot of mass to convert to energy.

[@jojolafrite90]

@@czerskip That's why, when someone obese jumps from a tower, he often will explode on impact with the ground, especially if the ground is hard. That was dark... Well anyway.

[@tezer2d]

even though I'm not a patreon and thus didn't ask any questions, it was still interesting to watch and I learned a lot

[@Die-CastMetal]

Never disappointed!

[@uptake2]

Very interesting... thanks for making time to make this video and all the other ones too... . Thank you, David

[@iamzid]

ya, I think that there will always be people that prefer to do things in real life. I used to be a heavy gamer but now pushing into my late 30's I'm finding more and more that I'd rather be outside.

[@brandonthesteele]

I first heard the notion that sufficiently advanced civs will just vanish into their own heads via technological dream worlds from ze frank in 2012. It puzzled me then and it puzzled me now. I'm not into video games like Scott is, but I can appreciate his different perspective. Stepping onto an alien world in the Large Magellanic cloud in a super immersive VR would be ultra tight, but on some level you would be conscious of this being a simulation. How would that be "just as good" as traveling to and stepping on that planet, if you have any concept of what you're experiencing being a sim?

[@sparkyprojects]

To Ryan, about lighningmaps If you go to Blitzortung. dot org and go to 'cover your area' (top menu) you can read about the radios and even buy a kit. The radios are VLF (very low frequency), to understand the basics, get an am radio and tune to a dead spot on the dial during a storm you'll hear the crackling, The data is sent to a server that triangulates the detectors.

[@triskeldeian4989]

@Scott Manley as a particle physicist, I would tell you that your explanation is a bit confusing. It's not just that the quantum number should cancel out. The easiest answer is that each particle has a matching antiparticle and that pair can interact through the electromagnetic interaction transforming that pair in a pair of gamma photons which doesn't have mass so it carries all the mass-energy of the particle-antiparticle pair has energy of the photons. When you have baryons, which interacts through the strong force, you may end up with more complex final states but, as you said, that's a much more complicated issue to explain in half a minute

[@necromancytools]

Great Q & A. 👍👍😎 Always learn something new with each of your shows. Keep up the good work.

[@johiahdoesstuff1614]

100% agree with that fermi paradox answer. If there was a full dive game with mental based magic in a way such that it felt like a law of the universe and not glued on top, I'd probably never leave

[@arctic_haze]

When matter and antimatter collide, everything cancels except mass which is energy. This is the most effective explosion possible.

[@sundayridetexas416]

I've never personally considered the virtual exploration option. That, if sentiments are anything like us, could be incredibly plausible. Awesome alternative view!!

[@obrienct]

you dont completely annihilate, not right away. the first bit of antimatter to touch matter will blow the rest off in another direction, until it hits more matter, or keeps on going if it doesnt.

[@stuartbrown1677]

Brilliant Scott I really enjoyed that Thank you Stuart in Ireland

[@DagaraLP]

If anyone is interested to hear more about the rocket skins then head over to SmarterEveryDay. He recently toured ULA's production facility. They explain the whole process of machining and treating the plates. It's really interesting.

[@frankgulla2335]

Good job! Thanks for the brutal honesty.

[@CalvinMaclure]

"playing video games when I'm supposed to be making videos for you guys" aayyy! Ain't that the truth! I know that struggle!

[@williamhastie5056]

I loved seeing Scott working out the math in his head. He was getting quite animated! Brilliant Scott. 👍🚀

[@senorelroboto2]

Antimatter interactions can get very complicated when dealing with composite particles. A proton antineutron interaction can undergo annihilation when the one antiup quark of the antineutron interacts with one of the up quarks of the proton.

[@DrDeuteron]

Does QCD really care about flavor?

[@Inspired_Mindz]

Amazing informative videos as always Scott. Keep up the Amazing work

[@MrEtmedic]

Lightning maps; ground based radio receivers with two ferro coils at 90 degrees with n/s and e/w orientation. They send the signals via internet and are triangulate. Just run the map with lines visible.

[@rwboa22]

A Ritchey-Chrétien telescope (or RCT) utilizes the "Classical" Cassegrain-type telescope design, however will replace the parabolic primary and secondary mirrors with hyperbolic primary and secondary mirrors, allowing the cancelling of "edge coma" (when stars on the edge of a telescope's field of view take on a comet-like appearance). Large observatories like Keck I & II and HST utilizes the RCT design, although in some applications, Schmidt-Cassegrain telescopes (SCTs) can be used as they allow long focal lengths (usually f/10; f/11 in telescopes larger than 12 inches) while allowing for a compact tube design.

[@jamesmorton139]

Great video! For those who want a deep dive into the flip manoeuvre, I believe the everyday astronaut has a video in the works that should be out soon.

[@nielsdaemen]

*Gravity is not a force, the force you are feeling is the normal force of the ground below you, pushing you up!*

[@benmol_]

In fact, you can build your own lightning radio receptor and share the data with the whole community

[@Misack8]

How!? I'm trying to hack a HT to hear lighting on the low AM band.

[@dreamyrhodes]

Oh and to calculate matter-antimatter explosion, just use E=mc2. So it's 170000 grams * 299792458^2 m/s which is quite a huge number.

[@anthoneyking6572]

Awesome Vlog Scott loved it Thank you

[@s.s.85]

Scott, thank you for your channel! It's my #1 source for all news space related and I can always expect a thorough analysis of all the latest happenings from your videos! I have a suggestion for a video. Rockets are cool but supporting facilities are quite interesting too; we all heard of Apollo Guidance Computer but what I'm curious about is, what kind of computers did the Mission Control for the Moon landing use? There's all these consoles and blinkenlights in the documentals, surely there must've been quite a mainframe in the background! Also, what kind of communications equipment did they use for all the telemetry? Was the Deep Space Network a thing back then?

[@mrpicky1868]

"if you are like 170 kg" now you know what he thinks of his viewers)))

[@johndododoe1411]

You mean buff musclemen?

[@whuzzzup]

American thinking in metric units :>

[@zapfanzapfan]

Yes, we are all Worlds Strongest Men contestants ;-)

[@MushookieMan]

170 lb-m, 170 kg, it is all the same planet killer explosion. A cosmologist would be ecstatic about a mere factor of 2 error.

[@Frellnikky]

LOL in his defense he's just winging the answers to these questions.

[@nicejungle]

Private virtual paradises are also my fav explanation for Fermi paradox. Not so glamourous I agree but that's the most plausible IMHO.

[@jfischer507]

0:08 You can say potato, I can say potato. You can say tomato, I can say tomato. 🤣 But I feel like you can't say Patreon and Patron like that.

[@ryanhebron4287]

I would love to see a video about the history of navigation by stars, how to navigate by stars on land, and how that navigation works in space.

[@jonslg240]

Interesting fact: during launch a rockets entire weight (and then some) is indeed supported fully by their nozzles. =)

[@charleslivingston2256]

But not by the bottom edge of the nozzle

[@Pathogenai]

Hi, Scott! What do you think about However Channel?

[@TomLeg]

If you are 170 kg ... you are 374 pounds. If you are a common male of 170 lbs, then you are 77 kg, which is somewhat less explosive.

[@martinslaba7249]

but in reality... it doesnt matter. Or anitimatter?

[@FireStormOOO_]

Energy wise yes, though at those kind of yields most of the energy (on the margin) is getting directed up into space so the destruction radius on the ground would be similar.

[@Huudzalo]

I'm still here for the kerbal. Been subbed for years and years. All the luv Scott

[@rosedruid]

Things KSP doesn’t teach you - nozzles aren’t made of unobtanium.

[@catfish552]

See also: Apollo 15 Lunar Module

[@Mike-oz4cv]

The nozzles are not and don’t have to be, but for a booster stage the engine has to support more than the weight of the rocket. Think about all that thrust force.

[@fiveoneecho]

In regards to the first question: something a lot of people don't understand is that you don't "feel" gravity. Gravity is accelerating every part of you- every atom in your body- at the same time in the same direction. You don't feel a force squishing you because of this. What you DO feel is the ground pushing up on you. The ground is accelerating you against the gravitational acceleration, resulting in a net zero acceleration. If you are flying around the "side" of the planet before you can hit the ground, you will be falling forever with everything around, being accelerated the same as that stuff around you. You don't feel the ground or the lift-force of an aircraft pushing up on you. You are in freefall. Edit: TL:DR- when you feel "the force of gravity" you are actually feeling the ground or whatever you are resting on HOLDING you in place with an equal and opposite force AGAINST gravity. Edit Edit: Obvious Scott knows this, but I wanted to explain it from yet another perspective.

[@HankMeyer]

I think the most plausible answer to the fermi paradox is that ET's maintain a presence on earth, but they keep their presence hidden, for reasons similar to the Star Trek prime directive, and/or a desire to study human civilization as much as possible without interfering with it. We do the same thing with wild animals, after all. Also, if I try to imagine what kinds of evidence we could expect to find if this was the case, the answer I keep coming up with is exactly the kinds of anecdotal eyewitness accounts that UFO and alien abduction researchers have been collecting and cataloguing for decades.

[@JoelleTheAbsurdist]

I don't really like Scott's answer regarding gravity. The fact is, on the way to the moon, you ARE experiencing gravity, but so is the craft, you are both decelerating, or accelerating, at the same rate, because gravity is affecting both you and the craft at the same time, and almost at the same strength. Take a cup of water, and throw it straight up in the air, it'd help if a GoPro was attached. You will notice that the cup slows in relation to the ground, and once it reaches it's peak height of the throw, if you let go of the cup smoothly smoothly, you will notice the water begins to fall at the same time as the cup, because it wasn't being held in the glass by acceleration, it was moving with the glass do to momentum. Both the cup and the water lose the energy imparted to them by your throw, at the same time...both "drifted" up together, and both "drift" down together.

[@juzores1]

Ok ,this is a better explanation, but the craft with the astronauts are falling free in the orbit too ? and how they correct their position in the orbit ?or they are floating because they are caught between two forces gravity and centrifuge expulsion velocity .(everytime someone answer question about this topic confuses me more ).

[@JoelleTheAbsurdist]

@@juzores1 No, centrifuge forces never enters the equation when dealing with obits. The most basic explanation is that the craft, and everything inside it, or near it, are moving at the same velocity... Gravity is not gone, it's still acting on all the objects, but acting equally on every atom of every object involved simultaneously. In the case of the international space station, every atom is moving in roughly the same direction in a prograde obit at about 7.6km/s, gravity is pulling on all those atoms roughly equally. Now this IS over simplified, and at an atomic level, other forces are involved, but at a very basic level, that's it, everything has the same momentum(at least on the atomic scale) in the same direction, so an observer will perceive weightlessness, but they're only weightless relative to the space station... Here's an experiment, take a pencil and throw it as straight as you can, at the same time, drop another pencil from the same high, you'll notice that both pencils hit the ground at about the same time. This is because the forward momentum you impart on the throw will be insignificant compared to the downward acceleration being applied by gravity. In space, there is almost nothing to decelerate an object, so it maintains it's momentum, anything inside that object, is traveling at the same velocity, but it's momentum is not coupled to the first object, in relation to each other, they are floating with respect to each other... but lets say you were at the same altitude of the space station, except with no momentum, dead still and not in orbit, and you threw a pencil, you and the pencil would burn up in the earth's atmosphere at about the same time, again, because you could not throw the pencil hard enough to send it into orbit, and the few meters per second you could impart to the pencil, would be insignificant compared to the acceleration gravity would apply to both of you.

[@JoelleTheAbsurdist]

@@juzores1 When an object in within a gravity well, the well pulls them toward the center at a specific strength in relation to the distance from the center of the well. If the object is also traveling at a 90 degree angle to that well, and if the velocity is equal to the strength gravity pulls, the object will circle the well like ball shucked around the rim of a roulette table. Because space has almost no friction, this balance of moving forward while being pulled down, can be maintained almost forever. To adjust orbit, the object needs to apply a force to itself, like firing a thruster... the thrust level however is usually so weak, that a person onboard that object, will barely notice that the ship is moving around them... until they bump into the wall, at which time, the craft imparts momentum to the passenger accelerating or decelerating them into the new orbit with the craft. Because of the relative size and density difference, only a slight nudge from any of the interior surfaces is required to get the passenger up to speed. If the craft applies a lot of force, and the passenger is not strapped down, the movement of the walls around them could become enough to splat them like a bug. Being balanced perfectly between two gravity wells, is about as impossible as balancing a ball on a sharp spiked point... rather, it's a balance of "flying away from" gravity, as gravity pulls you down. I put flying away from in quotes, because you don't need to apply more thrust, in a sense you're gliding.

[@Mandelbrot_Set]

This rocket science is all fine and good, but is there a way to measure the difference between beer that has been shaken and beer that hasn't without opening it?

[@wretlaw1203]

yes, quite easily. by shaking the beer before opening it, you can be 100% certain that the beer inside is thoroughly shaken. no need for fancy gamma ray spectroscopy.

[@deanerhar]

According to the Heisenbeer Uncertainty Principle, the beer can be considered both shaken and unshaken until you open it to find out.

[@CheshireTomcat68]

Use a cambelt tension gauge, like an optikrik, on the side of the can to test the pressure?

[@Mandelbrot_Set]

Does pressure increase in a shaken beer? The temperature and the volume were not changed.

[@CheshireTomcat68]

@@Mandelbrot_Set I will leave it to younger enquiring minds to squeeze a beer can, give it a good shake then squeeze it again to feel if it is tauter. I am personally just going to drink mine.

[@ivaylot9452]

You are funny and very smart! Enjoyed this video a lot.

[@marcusthegoat8259]

i think the main reason for belly flop is actually to protect engines in reentry and also doing it late because of spped

[@tpseeker3367]

Belly flopping gives more surface area to help slow down. Think of people parachuting. Head or feet first go faster & slow down as soon as they flatten out.

[@zuvermieten]

14:20 Wow - I never thought about this kind of filter. But I guess it makes sense since humans might get lazy if at some point every necessary labor to bring us food and maintain our livestyle is done by machines. Interstellar travel is going to be pretty tough to figure out. So why struggle with it when you could as well spend your time in an evironment that gives you everything you wish without you doing anything?

[@humbleguy9908]

Scott, are you saying that antimatter has negative energy? I always assumed that you need 2*mc2 for producing matter since you also produce the same amount of antimatter. Am I wrong?

[@passemoilesfraises]

Negative energy doesn't have any sense in physics (it's even one of the core difference between math and physics), so yeah basically I would say that you need twice the energy of the matter particle that you create. Maybe look at virtual particles and vacuum energy it's all about matter anti-matter creation and destruction. The meaning of E=mc2 is that the energy is conserved anyway in any circumstances, before it, mass was not energy and so photons where "massless".

[@humbleguy9908]

@@passemoilesfraises We seem to agree that there is no negative energy and therefore, that the hypothetical transformation from matter to antimatter would be energetically neutral. And yes, there would be an analogy to the vacuum fluctuation. Since the fission/fusion step would give you matter and antimatter in equal amounts, if you do not separate these, they will annihilate producing energy, which will produce matter/antimatter and so on.

[@patrickradcliffe3837]

They also use a process called chem milling to make panels lighter without reducing strength.

[@IrreversibleExtents]

I did the math on this. You can survive for roughly 464.5 Million years on a single raisin if you gradually convert all it's matter into energy. (I also took into account the amount of joules you consume each day.) Thank you, Einstein.

[@IrreversibleExtents]

@asdrubale bisanzio Yeah, in retrospect, I realized this. Maybe it would be more practical if you were to power your Tesla on a raisin.

[@andrefagerlid5352]

Cant wait for the 3 iteration and hopefully a guide to books worth to read, I love your content. If you look to winward and study the surface detail of the bookshelf, the use of weapons, a state of the art piece of work seems to have met a feersum endjin against a dark background. Coincidence or an excession of the player of games? Oh, and first but not least, consider Phlebas.

[@Jens.Krabbe]

I spend time watching your videos instead of working on my boat, exercising, cleaning, and so on 😂

[@Fondage]

Great questions and Awesome answers ...thank you guys ML❤✌

[@gcujustreadtheinstructions3227]

The Pandora's box of the Q&A has been opened, how will the wise sage of all things manage, where others have failed?

[@MidnighterClub]

Star navigation would be a cool couple of videos. One video (at least) on terrestrial navigation here on Earth would be a great addition.

[@Björn_Schnabel]

I really like your style on these kind of videos. I think, you should continue this format.

[@Ayelmar]

At 14:18 -- The scenario you're describing reminds me a LOT of the setup to E.M. Forster's 1909 short story, "The Machine Stops."

[@bArnEyBoss]

Hey Scott, your last comment is probably my favorite :D makes us all feel less guilty when playing video games instead of doing all the other more important stuff :) thx for that!