Dark Curvature, Navigating the Oort Cloud, Future of Space Toilets | Q&A 207

[@realzachfluke1]

*[Coruscant],* without a doubt. Love the idea!!! And thanks as always, Fraser! I eternally appreciate every aspect of your work.

[@Ed-jg3ud]

😂😂 “space, it’s right there in the name” great line 🤣

[@Ronaldo-vs3uh]

"Dark knocking sound" 💀. Coruscant

[@realzachfluke1]

That's got my vote too. Perfect question/answer duo.

[@TheyCallMeNewb]

Fraser's answer to Mandalore at the end was profoundly scientifically versed. I for one neglected the speed of gravity aspect. Excellent stuff. The more one knows, the more one senses they have yet left to learn, fostering among other things, humility.

[@simonmultiverse6349]

31:32 "...we can't detect a planet around the closest star" Disagree! Try ALMA : Atacama Large Milimetre Array - one can see emissions in the milimetre range and see planets forming round stars.

[@laszlomeszaros247]

[Mandalore] Same here, never consciously considered the speed either.

[@glenwaldrop8166]

@@simonmultiverse6349 He's talking about Earth sized planets. The closest we've found yet (I think, correct me if I'm wrong) is roughly twice our planet's mass.

[@glenwaldrop8166]

To put another hitch in everything, we have evidence the speed of light (and as such atomic decay) is not fixed, so is it related to the speed of gravity? Are they independent?

[@glenwaldrop8166]

@Smee Self The first one I've heard of was tonight, .99 Earth mass. That's the closest yet, they can't tell if it has no atmosphere or if it's really dense.

[@Adrian-foto]

Good morning and kudos Fraser from Slovakia, thank You for another great video. Everytime I listen to your in-depth yet well explained answer it prompts even more questions :) Regarding CMB, I was thinking about resolution of the smallest feature within the CMB map and if we could see / detect changes in CMB polarization or amplitude over time to map the "bubbles" in 3D like CT scans of CMB to obtain more info. This would require to "progressively scan" entire sky at regular intervals.

[@JoshKaufmanstuff]

@10:00 What if we sent out a series of chaser relay satellites to follow the long-distance probe? Would that be a viable alternative to having to send a strong enough signal a far distance?

[@bikerfirefarter7280]

Yes, but you'd have to deal with complexity, cost, failures, redundancy issues. How much more complex would the features of the main probes have to be to overcome the costs/mass of the repeaters? Do you send a very capable probe with the ability to communicate directly, or a relatively dumb 'scout' and repeaters (then, dependent on feedback, a more capable probe)? Add to that the costs of sending multiple probes to many systems and the logistics starts to get very complicated. Or do you risk 'generation ships' that are capable of re-fuel/re-build when/if they reach another system? Could those ships build transmitters from local materials at each destination? Are you just going for a look/visit, or intending to stay/colonise?

[@JoshKaufmanstuff]

@@bikerfirefarter7280 Yes, I believe those are all perfectly valid considerations for any probe, however when you consider the power and weight limitations using solar sails or laser propulsion then sending a chain of lower power relays seems to become more of an option in my opinion. I'm curious if it's ever been considered before, but perhaps not for traditional probes because of the reasons you mention.

[@bikerfirefarter7280]

@@JoshKaufmanstuff Solar/laser sails only 'propel' close to stars, and we can already communicate from beyond Pluto, so there will be no solar power for a chain of repeaters (have you calculated how many it would need per chain?). It would need MANY repeaters if low-power, and they'd need constant/regular launches to maintain the line at this end as they drifted out of range. And all that for only a small duration of data returned. Lets face it, the probe itself will probably be a 'fly-by' and not be doing a grand tour of the target system(s). I think a relatively small cluster or one sophisticated probe per star, that has the ability to direct send whatever data it collects is more feasible. And we'll probably send them to at least a dozen of the nearest and most interesting stars first, assuming we design/build/launch any, then re-assess what/if to send as follow-up.. Even with a good percent of light-speed it's going to be a l o n g time undertaking..

[@JoshKaufmanstuff]

​@@bikerfirefarter7280 Thank you for your reply. I was mainly speaking about the notion of laser propelled vs. solar sails. This would give them a high rate of speed but very low mass/ power budget, thus the low powered transmitter. I would need to know the specifics of the mass limit involved to figure out the capabilities of the transmitter onboard. Also the power availability in interstellar space seems low to non-existent. I'm not sure if the plan is to use solar upon arrival?? There may be another non-starter for the chase relays that just occurred to me: As our Star and planet continue to move it could possibly be moving closer to the destination star, but likely away . .

[@bikerfirefarter7280]

@@JoshKaufmanstuff Agreed. But in your last point the impact of such monement would be so small as to be irrelevant.

[@quiron139]

Couldn't pick just one! Great Q&As this week! Tatooine Mustafar Dagobah Mandalore

[@jeremyeharris]

Hi Fraser, I was reading an article about the 'Wow' signal and it got me wondering. What would the 1974 Aricebo message look like to a distant alien civilisation if they detected it? Would it seem like the wow signal, a one off never repeated signal with unique specificity?

[@DataSmithy]

Coruscant : I always thought the term dark gravity did the job fairly well.

[@ghmratliff]

Has there been any change in the cosmic microwave background since we first mapped it? Or do we even continue mapping the C.M.B? Thanks!

[@ericsimonetti5876]

A question I'd love for you to address on a Q&A: Is the red-shift of light determined by the speed the object is moving when it's emitted, or is it determined by how much the space it's been traveling through has expanded over time? Do both effect the red-shift? (More below) I want to elaborate on this question a bit more, but I offered a short version you could display on the Q&A video. My confusion comes from the analogy that is made between Doppler shift and red-shift, which seems very different from the phenomenon of light being stretched by spacetime while it's traveling. I have some confusion about both explanations, so I'll separate them below. *Doppler Shift* When a car is moving away from you and makes a sound the sound is Doppler shifted since the source of the pressure waves is moving away as it creates them. I don't understand how such a thing could happen with light, given it is quantized and emits all at once. Another reason this doesn't make sense to me is that more distant objects would have been moving away from us more slowly when they emitted the light we see, yet unintuitively (given this reasoning) they have a greater redshift. *Expansion of space* I've seen animations of light slowly red-shifting over time as it travels, which implies to me that the expansion of spacetime is "stretching" the waveform of the photon and thus changing it's wavelength (tangent; where is the lost energy of this photon going?). If this is how red-shifting works, how do we actually know the speed of an object given this information? Wouldn't it only tell us the total expansion of spacetime between that object and earth, specifically during the travel time of that photon? If the rate of expansion is changing over time, or different depending on the region, how could we possibly tell? The light wouldn't encode how much it was "stretched" at different points in time assumedly, so do our calculations include assumptions to combat this? For example, the rate of expansion being consistent across the cosmos? The entire concept of an expanding infinite spacetime is hard for me to grasp, so I apologize if this line of reasoning isn't sound.

[@dancingwiththedogsdj]

Was gravity much stronger in the early time of the universe because space itself was smaller and therefore the effects were much more pronounced and impacted stars / galaxy formation to be faster than anticipated but it hasn't been accounted for in simulations properly or something? It seems like we're getting close to figuring this out pretty well and then more questions to figure out. Great video! 😊

[@theunknownunknowns256]

Hoth. The other way to get communications over long distances is retransmission (retrans), vastly easier than a receiving antenna the size of a planet. Old tech, easy to do, and exactly what the Mars orbiter does to help the Mars rovers.

[@JediBuddhist]

[Coruscant] Definitey. Might drop a Q in on that one soon too.

[@WolfgangFeist]

25:42... Exactly; we are getting less radio-loud year by year -- mainly, because the efficiency of information/communication is getting better and better. Same process: We are becoming more and more eneryg efficient; so, all this 'Kardashev - Types' are somewhat out of date. 🙂

[@PaulMacias]

[Dagobah] Seems an obvious question to ask, but first time I recall seeing it asked and answered. Thanks.

[@rogertulk8607]

I am always amused by the animations of the early solar system, the asteroid belt, the Kuiper belt and the Oort cloud on how the universe works. I knew they were far apart not quite as far apart as you just explained but in those animations it looks like you could jump from one rock to another! I wish they would explain this once in a while.

[@kylegoldston]

Dagobah...I remember there's a way a fission reactor's excess radiation can shield a spacecraft. I'd be more like a mini heliosphere than a magnetosphere.

[@agentdarkboote]

How would I go about measuring the rotation rate of a galaxy on my own?

[@cltr8011]

Wow so many good questions! I can't choose whether the best is Bespin or Coruscant...

[@DanBennett]

QUESTION: Are comets mostly rubble-pile objects?

[@uuzd4s]

Always thought you'd do better just talking about what you know instead of reading your Resume at the beginning of each broadcast. I find myself listening closer now ! Gr8 Show !

[@agentdarkboote]

Why does interstellar dust collect in lanes in a galaxy like Andromeda? Why is it not a similar distribution to the stars which are producing it?

[@Yezpahr]

Coruscant. My recommendation is to rename Dark Matter to Dark Gravity. 24:10 I think the problem we have with CMB being where it is, is that it is where and when it is. We see it as a shell, but we're used to the fact we see things **where** they are. This leads to the misconception that the universe was this size we see it at now, while that can't be the case. What actually happens is that we see the creation of the universe as it goes on.

[@PhysicsPolice]

Why? Dark Matter is matter. We know this because we've observed it displaced from the Baryonic matter content in a galaxy (the Bullet Cluster).

[@glenwaldrop8166]

I think they're misjudging gravity. Light hits a point where it doesn't get smaller but it gets dimmer, what if gravity has a minimum effect on matter regardless of the distance? At a certain point it just doesn't get any smaller yet it never disappears.

[@Waynesification]

There was a problem with magnetic shielding. They could get the shield down to lower energy, but apparently the baddies can follow the field lines around and through the astronauts. Metal was also put down as shielding, as bombardment would make them spray particles in the direction of the insides of the ship. I used to read news on this stuff.

[@michaelwalsh5048]

Hoth Very good question. Even better answer.

[@fkaMilo]

Dagoba A great practical answer

[@fkaMilo]

Oops forgot the "h"

[@Dextrovix-42]

[Mustafar], I enjoyed the answer by the explanation by Fraser.

[@aarondyer.pianist]

Excellent session.

[@theedspage]

My vote is for Tatooine. Question: Was there ever a point where the constellation Orion crossed the elliptic? If yes, can it happen again? Thank you.

[@richardvanasse9287]

Great video as always. Keep up the good work. 👍🏻

[@roaldjensen3120]

Hi thanks for a great show. Will we ever reach a point where all the light that was set free by recombination finally reaches us from our point of view and the CMB stops "shining" for observers on Earth?

[@AnonymousFreakYT]

[Hoth] - The "send a message back home" is always the part I wondered about. Wouldn't Proxima itself overwhelm any possible signal anything small we could send?

[@charlescalkins7096]

Question: If Jupiter was 1 AU from the Sun and the Earth was a moon of it, could Earth still support life? Would there be much change at all? Or, for example, the repeated eclipses of the Sun by Jupiter as Earth orbits, and Jupiter's strong magnetic field, cause temperature and weather changes, impact on technology, etc.?

[@CarFreeSegnitz]

Along with Jupiter’s strong magnetic field are spectacularly deadly radiation bands, Van Allen belts on steroids. If Earth were orbiting Jupiter at roughly Io-Europa distance that radiation would probably preclude stable biology, getting constantly ripped apart by high-energy nucleons.

[@PhysicsPolice]

4:44 No, Dark Matter cannot be due merely to a misunderstanding of how gravity works at the largest scales. We've used Dark Matter as a telescope. It's a thing. Not a force. It's some kind of stuff that, as seen in the Bullet Cluster, has a position in space separate from the baryonic matter. No MOND can explain this. (Not without losing the ability to explain all the other lines of evidence from CMBR, galactic rotation, gravitational lenses, etc.)

[@StefenTower]

On life elsewhere in the universe, I keep going back to two thoughts: 1) we are already reasonably sure that chemistry works the same throughout the universe; 2) we've really only barely begun to search for life elsewhere, so it's way too early to draw conclusions.

[@xliquidflames]

Question: How come it seems like space objects are always made of one single material instead of everything being a mixture of all materials? Comets are mostly ice. Some astroids are metal, some are rock, but most asteroids are made of mostly one material. Why is that? Why isn't every object in space a mishmash of everything?

[@waerlogauk]

Dark gravity is an effect observed in/around galaxies do we observe this effect at any scale larger than galaxies or around any other objects?

[@918_xDx]

it's amazing that the earth has it's own shield.

[@Spedley_2142]

I know how gravity fields are displayed - like heavy balls on a flexible sheet - but I have no idea how gravity 'propagates' through a gravity well. Recent experiment proves gravity travels in waves. If two distant black holes collide does the gravity go past the sun faster than through it? Does it diffract? Maybe it combines on the other side in diffraction patterns? Could this be the cause of Dark Matter - gravity being 'in phase' and having a larger effect?

[@Czeckie]

Thanks for the Mustafar answer, it definitely helped. But I'm still having problems understanding it all. Is the very fact that we can even see some cmb thanks to the inflation that was much faster than speed of light and we got so far from the rest of universe at T=0 that we can still see parts of it even 13B years after? Will cmb stop at some point in time? (due to the expansion of the universe?)

[@The_CGA]

The CMB will eventually redshift (stretch out the waves) until it’s impossible to see. So kinda. > why can we still see it, inflation, etc? There’s always more universe that’s further away, so there’s always somewhere (a sphere around us) that more CMB can arrive from… it’s not necessary for the universe to “warp big” to allow CMB arriving as late as it does. Just “fast.” Say a nerf gun gets shot at a R/C car, but the R/C car is driving away from the Nerf…it’s going to take a lot longer for the dart to arrive as the distance got bigger even though the Car is slower than the Dart.

[@bobinthewest8559]

We have an incredible tendency to “overthink”. If we receive a message saying, “Don’t do X.”, and that message doesn’t include not only a detailed explanation of WHY, but also some form of PROOF of the negative outcome…. More than likely, some of us will assume the motivation for telling us not to do it, is to “hold us back” in our development/advancement.

[@KGTiberius]

Naboo. Expanding sphere of observation to understand if there is life. Copernican principle via expanding (counter)indications.

[@douglaswilkinson5700]

The star R136a1 is fusing hydrogen in its core. It's a main sequence Wolf-Rayet star: WN5hV. A lot of folks are uncomfortable with this. But that's the definition (cf "Oxford Dictionary of Astronomy".) And being a main sequence star it's also a "dwarf" (cf ibid.)

[@bobinthewest8559]

Aren’t all main sequence stars “fusing hydrogen in their cores”?

[@Nowherenear-w1d]

[Hoth, Mustafar, Dagobah, Mandalore] I have a question, not sure have it been asked here, sorry if yes. Question: may it be that supermassive black holes are made of not matter, but antimatter? Could it be that these things explains "missing" antimatter? Could sum of supermassive blackholes weights counterweight all other barion matter in the universe to make it match? Black holes of antimatter couldn't be distnguished from blackholes made of matter, right? Or even: can blackhole be made of both matter and antimatter with mass combined? Thank you for answers, they are always great and it's really pleasure to listen and stay curious

[@agentdarkboote]

What is interstellar dust made of?

[@joethestack3894]

Question: At what distance from a planet or star is an object "free" from the gravitational pull from that body? Of course it depends on the mass of the planet or star. We know from basic physics that the potential energy of an object in a gravity well only comes back up to zero at an infinite distance from the body. But long before we get that far, the force of gravity drops off to the point where it is small compared with other forces acting on the object, e.g. propulsion. In low earth orbit, the force of gravity is only slightly less than that on the surface of the earth. How far away from earth would our spacecraft with a wimpy drive have to be to be able to resist earth's gravity and follow an arbitrary course? I'm looking for a rule of thumb, not an exact quantity.

[@thentil]

Prof David Kipping of Columbia University has an interesting lecture on the Fermi paradox that was expressed in a way I hadn't really considered; he has it on his channel "Cool Worlds Classroom" titled "Why we might be alone" Public lecture by Prof David Kipping if you're interested. Anyways all these topics are so cool, [Bespin] would be my vote.

[@bobinthewest8559]

One of the cool things about Cool Worlds (David Kipping), is that most of the time he examines BOTH points of view. For example, along with the video “Why We Might Be Alone”, the channel also has a juxtaposed video titled (something like) “Why We Might Live In a Crowded Universe”. It’s another wonderful channel which I think would be appreciated by anyone who appreciates this one.

[@lostinfrance9830]

[ Coruscant ] One question i have always wondered and never here any Space channels mention or talk about is the "Dark" its self. I mean it is everywhere Black, as soon as there are no lights on as an example underground it becomes instantly Black/Dark and the whole of space also has dark and black everywhere. Is it something like dark matter that we can not detect yet that allows light to become light/light up as it is amplified/reflected through whatever the Dark/Black is?

[@bobinthewest8559]

The really weird thing is that, it is not “dark” in space. The blackness that you “see”…. Is the absence of matter for the light to reflect off of. In other words…. Where you see blackness…. You are essentially looking between “objects” which can reflect light towards your eyes.

[@50rri50]

How do we know red dwarfs are fully convective?

[@rustymustard7798]

I suspect that dark matter is a combination of there being more stuff we can't see that makes gravity act in ways we don't understand. If we really want to have fun with the name we'd call it spooky phantom pirate space ghosts and send a probe called the mystery machine to figure it out 👍

[@bobinthewest8559]

Ruh-roh…. Better be sure to bring enough Scooby snacks

[@rustymustard7798]

@@bobinthewest8559 we're gonna find out dark matter was just old man Withers with a mask, flashlight and a whistle playing with giant magnets in that spooky old abandoned amusement park.

[@oberonpanopticon]

It’s obviously space vampires. We just can’t see them because all of the most powerful telescopes use mirrors.

[@wknajafi]

why does dark matter coexist with visible matter only? is there any documented observation of dark matter alone?

[@originalulix]

Regarding detecting planets in Andromeda... how would that work? How many photons even reach us from an individual (sun-like) star in Andromeda? I imagine very few, so if you say have 10 photons per second, how can you measure a reduction of 0,001% (using the transfer method of detecting exoplanets)?

[@caejones2792]

With lots of caveats. There is a candidate planet detection in M51, because there's a powerful xray binary there pointed at us, so we can detect when the planet passes between us and the beam. Said planet is most likely an irradiated hellworld being shredded by its stars, but it's still a stronger candidate than the gravitational microlensing events in Andromeda and the Twin Quasar's lensing galaxy. So maybe we could hypothetically learn more about M51 ULS1b by studying the xrays and how they change when they hit the planet closer to the edge, but that only works because M51ULS1 is a monstrously bright system. So any extragalactic planets we can get any data beyond mass and orbit are most likely to be uninhabitable, just because of how bright the backlight needs to be. (The microlensing candidates are interesting, too, but since they're vanishingly unlikely to repeat, they can't be confirmed. I'm a bit confused about the Lensing Galaxy's candidate, since the estimated mass is 3 Earths. We can detect a microlensing event *that* small, in a galaxy *that* far away? That's some precise measuring.)

[@CyberiusT]

I remember hearing one astrophysicist refer to it as "anomalous mass" rather than "dark matter". I tend to think that implies that there is actually an object of some sort involved, but am not sure whether that's better or worse substituting "gravity" for "mass".

[@oberonpanopticon]

Except that it might not even be mass if it turns out that our theories of gravity are just wrong. Although, it does definitely seem like invisible matter explains the most anomalies.

[@AverageFornaxEnjoyer]

I do have a question in regards of heat build up on future spaceships; I know they need cooling pipes and slow external radiators to cool them and this I feel is rather clunky and sexy in its own sense. The question is: Could you not cool them like we watercool? Have a lot of heatpipes and exchangers through the craft running to the external hull (double layered like a submarine) and use simple network of pumps to passively cool? Use the cold energy poor vacuum of space and have a exchanging fluid (like plentiful water)? You'd have to coat the outer hull in a material akin to the JWSTs sunshield, but it could be done right? Or do I not understand basic physics? It would add a lot of weight and isn't exactly feasible at the moment in the actually getting it to space-wise. Not only that if the hull was to be penetrated, the water would likely rapidly freeze and not instantly doom the entire craft.

[@theOrionsarms]

You don't understand basic physics, in space you can only use radiative cooling, because vacuum is nothing and nothing doesn't make conductive or convective transfer of energy.

[@NullHand]

Radiators on Earth are really poorly named. They radiate very little of the heat energy they dump. What they really are is water to AIR heat exchangers. That is why the ones in your car always have a fan. There is no air to dump heat to in space, so your radiators better be TRUE radiators. Also, you better not let them get sunlight, else they become the opposite of radiators and become solar absorbing heaters. Vacuum insulated no less. That is why you need steerable, non reflective radiators to point at dark areas of space. This probably doesn’t describe the hull of your craft, which will be on average half in sunlight, and probably shiny (shiny is the worst case for radiating. Flat black is best. Just as with absorbing radiation).

[@AverageFornaxEnjoyer]

@@NullHand Fascinating, thank you for the further details. Not like we'll ever be able to leave our Heliosphere, but the future of interplanetary travel do be lookin' good. Long ships with massive rotating wings of black and inflatable pools, bedrooms and Starbucks. Another curiosity I have is how long would it take to get a probe to Alpha Centauri? Obviously powered with a decaying rod of uranium and built like a tank. With our best rockets and gravity assists?

[@NullHand]

@@AverageFornaxEnjoyer You are not gonna like the answer if you expect to do it with rockets... The most efficient rocket engine we have ever actually built and tested was the final nuclear powered, Hydrogen propellant NERVA design. It has never flown in space, but managed a specific impulse in desert firings of about 850 sec. About double what chemical rockets manage. This corresponds to a max delta V (attainable velocity) of about 37 km/sec. This is assuming 99% of the mass of your craft is the Hydrogen propellant. Since solar escape velocity from the vicinity of Earth's orbit is about 42km/sec, launch from here is a non-starter. I will assume instead we can send the ship components/fuel out to Saturn orbit distance with the usual various gravity assists, and launch from there, where solar escape velocity has fallen to about 14km/sec. That should leave us 37km/sec minus 14km/sec, or about 23km/sec cruise speed once we clear the suns gravity well. But then we have 40.2 trillion kilometers to go. At 23km/sec my math puts the travel time at about 55,400 years. And all this leaves no energy/mass budget for slowing down at the destination.

[@AverageFornaxEnjoyer]

@@NullHand Wow. That's rough. Why make a universe so big and full of wonders and never able to touch it?

[@SilverCreekStretch]

I've read that the voyager space crafts have entered interstellar space. How can this be if they have yet to enter the oort cloud? What is the definition of interstellar space?

[@mrEofPlanetEarth]

I can explain. You see, the Oort cloud is under the sun's gravitational influence. The material there orbits our sun 🌝 . That is the Oort cloud, its huge, it takes thousands of years to go through at the speeds the Voyagers are going. Apart from that, the sun emits radiation, also known as the Solar Wind 🌞🌬. This wind weakens the farther from the sun it gets. When it can no longer push outwards, it meets with Interstellar space. Interstellar space is the stuff between stars, different radiation, gases, dust, etc. Think of solar wind meeting Interstellar wind. The sun's solar wind doesn't go out as far as the sun's gravitational strength. So there is a bunch of Interstellar space inside the solar system, inside the Oort cloud. So, since the solar wind doesn't blow as far out as the Oort cloud, the material there and the Voyager spacecrafts are actually flying through Interstellar space while also being inside the solar system.

[@vinnyc7613]

question. if we know when the big bang happened, 13.8B years ago, and we sort of know the rate of expansion of the universe how come we cant know the size of the universe, or as to say that the universe is infinite, which seems all physicists had infinity's

[@w0rmblood323]

Question; Can or will the JWST be used to find planet 9? If so, what could we expect regarding its contribution to the investigation?

[@trebell885]

ONE thing bout space is? There's a lot of it out there.

[@RafaelDominiquini]

Question about the twin paradox: If Alice remains on Earth, always experiencing the same acceleration (10 m/s²), and Bob goes on a trip, but his ship always maintain the same acceleration (10 m/s²) for the entire trip, holding a speed close to the speed of light for the majority of the time, when Bobs meets Alice again, will be any time dilation between the two?

[@justfellover]

We will change the name of dark matter. Hopefully, the new name reflects what we learn about what it is rather than a more correct description of what it isn't.

[@carlfollmer1767]

[Kamino]: loved your interview with Logan Smith (and all your content really). I never bought into NASA saying Orion would take crew to Mars for the reason that the astronauts would go crazy locked in a capsule for months. Is that still NASA's plan or do you think they'll use a much roomier Starship assuming it becomes human rated?

[@max-ripi]

I kept expecting the dark forest theory to come up in this episode.

[@simonlindley2950]

Hoth. Grreat Q&A!

[@JonBurgin]

You said that the rules of the universe where, well...universal. But I thought there was some debate about the Hubble constant not being, well constant. Can you discuss the implications of that?

[@chipblood]

[Coruscant], this s one fascinates me. Is it possible that the entire universe and all it's combined mass could be un unconsidered variable? Like the universe should be calculated like any other hunk of mass in the universe? I'm not knowledgeable on how scientists even begin to calculate this stuff but if there is another series of universes maybe our universe is sort of like a galaxy in a space comprised of many universes . I hope this make sense. Many of these big questions put me at a loss for words because they really make your mind work.

[@larnotlars1717]

I bet that astronomy will get a lot more attention with several articles about the universal "Dark Attractor"

[@airplayn]

NABOO? Speaking of statistics, how about definitive knowledge about the galactic neighborhood within twenty years instead of hundreds? This topic reminded me of a lecture given by Dr. Davies I attended about almost twenty years ago at the Beyond Institute down here at ASU, Tempe. FYI - This was around the same time frame Dr Lawrence Krauss founded the Origins Project @TheOriginsPodcast which eventually led to the ASU Interplanetary Initiative @asuinterplanetaryinitiative. At the time of this lecture Dr. Davies worked closely with SETI and he claimed the modern multi-spectral radio telescope technology being used by SETI had become so efficient at scanning multiple frequencies simultaneously they calculated the probability was near unity that within the next twenty years any search being conducted would have detected all radio broadcasts from any technological civilization that was transmitting radio signal at levels similar to Earth -- if they are at all common out there! The scientists concluded that if SETI didn't hear anything after twenty years of constant listening we might as well turn off our receivers and rethink the entire problem. Either no one is out there or they aren't using old fashioned radio any more. Any thoughts? Start looking for lasers, or even entire stars blinking out signals in galactic Morse Code? Neutrinos anyone?

[@olorin4317]

Tatooine The density of material that people think exists in asteroid belts would actually be present in very thick nebula where stars and planets are forming, right? Do you think astronomers should create a "thickness scale" for debris fields in space? Heck, with a name like "thickness scale" it should get some press too.

[@Mosern1977]

In the Dark Matter / Curvature discussion. You correctly point out that calling it Dark Matter might not be the best idea, since it might not be matter, and it could be a wrong theory for gravity instead. There is also another possibility, that our way of measuring speeds of stars is not working as we think it is.

[@bobinthewest8559]

I think it’s commonly admitted/acknowledged that our understanding of gravity is incomplete. Also, I’m sure that those humble enough, will admit the possibility that our measurements could be off to some degree…. Potentially influenced by as yet undiscovered/unrecognized phenomena/phenomenon, just as our view is skewed when looking into water.

[@Mosern1977]

​@@bobinthewest8559 - yes, but I never hear anyone mention that possibility.

[@jamescarruthers1967]

No matter how far we look without finding life, let's say 100 light years, that's not 0 living planets / 100 LYs, it's 1 living planet / 100 LYs. The numerator never drops to zero, so the probability never drops to zero. No matter how unlikely life is, we know it's possible, therefore it must be possible elsewhere.

[@zs9652]

There is a possibility that this universe can host life but not generate it. If we ever found precursor like ancient civilization tech, we could assume that they started our planets life artificially. The precursors themselves would have been from another universe where life arises naturally very easily. So if we look out and see that there is no life across many galaxies and our simulations never get life to fully arise, then we could say life cannot arise naturally.

[@jamescarruthers1967]

@@zs9652 I'm pretty sure if we found evidence of a long passed advanced alien civilisation, it would be seen as evidence of the ubiquity of life, not the absence / impossibility of it.

[@tribaltalker1608]

Speed reading the blurb above (the video description) I saw "Do aliens block their space toilets?" I'll get my coat.

[@nzuckman]

My biggest gripe with the galaxy rotation curve problem is that we assume there must either be missing matter or a misunderstanding of gravity. But what if it's an entirely different force at play? Why isn't electromagnetic force more seriously considered as the invisible glue holding galaxies together? 99% of matter in space is plasma, plasma at different electrical potentials don't mix (i.e. they could form bubbles or cells), and electromagnetism is many orders of magnitude stronger than gravity. Stars would only need a small electrical charge in order for their orbits to be dramatically affected by ambient electric and magnetic fields. We can see huge coherent magnetic fields throughout the spiral arms of galaxies, but as far as I understand, we don't have a way of directly observing electric fields from a distance, so they're just as invisible as any dark matter candidate!

[@faker-scambait]

Love your show

[@uncletrashero]

there should be no problem getting enough solar energy for interstellar transmission from a target star any probe is sent to. just have to make sure the probes brings some solar panels

[@mrxmry3264]

21:13 instructions to build a machine? now what does that remind me of? :-) 22:25 bingo! 26:39 but it is already too late to avoid detection. if there is a hostile civilisation out there, it is only a matter of time before they detect us and show up on our doorstep. or send instructions to build a machine :-) 28:07 don't panic! the answer is 42. 31:35 hm, 6 support struts for the secondary mirror. that means the stars in those images will have 6 diffraction spikes.

[@susancaleca4796]

What if you put radio receivers on several planets or moons to receive far away messages?

[@bikerfirefarter7280]

You are confussing acuracy for amount. More receivers would only increase detectability equal to their collective area, spreading them out gives better resolution not 'gain'. You may as well just put the cost/effort/material into making bigger/more 'dishes'/receivers; distance apart gains you little/nothing in that case..

[@DominikJaniec]

5:55 I would have to make the same calculation too, to be fair and not lie, as how I can be sure, if that is true

[@samson1200]

{Coruscant} Would installing a couple of Kilometer wide focused beam Dishes on the moon enhance the communication between Earth and Mars?

[@monolalia]

Maybe Oort "cloud" or Kuiper "belt" and all those illustrations showing them as dense floating gravel fields are a tad misleading too :)

[@petevenuti7355]

Tatooine, another but the many I am sure are not very big, and you'd probably be moving by so fast, would you even know you had a close call of some of the smaller ones?

[@terryharding4185]

Got Naboo on the mind👍🏾

[@zrebbesh]

Just a note, but I was really hoping to hear a discussion of actual navigation. You know, like what do you sight on, and how small a fraction of an arc second you have to distinguish, and how you use doppler shift in pulsar timing for clues about your vector, and so on. Another turn about the irrealis of movie asteroid fields was kind of a letdown.

[@jolierouge1215]

How can we see Mustafar?

[@jaredweaver6889]

Are we detecting changes in the cosmic background radiation pattern through time?

[@Tordogor]

'La Nube de Oort está tan lejos que queda en la Nube del Orto.' (Argentine Astrophysicists dixit 🇦🇷)

[@fisheye42]

Coruscant - Car analogy? Yeah, I ran my Universe on my mechanic’s engine dyno. It turns out I literally have ALL the horsepower! Vroom vroom!

[@mrEofPlanetEarth]

Why do people keep referring to Coruscant? What does that mean in the context of this video?

[@cobwaldosblepot4247]

19:20 If you haven't already watched "The Expanse" what are you doing here?

[@frasercain]

I've watched the Expanse

[@Mike-iv3hy]

To the person who asked about space toilets. I have tried a new diet plan, where I eat for 3 days and fast for 3 days. My body has developed to a point where it uses almost 100% of everything I take in ! There is almost 0 waste ! I am NEVER hungry and I am not weak ! Perhaps if astronauts could perfect this type of technology , space toilets would become practically obsolete I believe that waste comes from over consuming! DML

[@vieleanimations]

follow up to mandalore: If gravity moves at the speed of light, does gravity also move slower through different materials? And does that mean gravitational waves bend around objects?

[@bikerfirefarter7280]

I've always wondered about that, but it appears the analogy breaks down. If it was as you think then gravitational detectors wouldn't work because the gravitational wave would also distort the detector by the same amount as the wave itself as it passed through. Gravity is a perturbation in space, not a thing itself like a photon is a thing, as far as I know there isn't a 'graviton' to be perturbed. But I could be wrong.

[@vieleanimations]

@@bikerfirefarter7280 hey thanks for that insight. that topic is just mind bending

[@moondog6004]

Hi Fraser Speed of light is relative Is speed of gravity also relative since it is also the speed of light

[@kadourimdou43]

Do you think there will be a mission to Europa or Enceladus in the next 20yrs. Would we have the tech to look for life in the oceans there?

[@Emdee5632]

Tatooine. Well, Arrakis/Dune too. What do we know or think how life can surive and evolve on a world that was once lush with vegetation and water and seas, but has been a dry desert for eons? Where is the oxygen in the atmosphere coming from? Not Venuslike worlds, just your average scifi desert world where human might live on.

[@StudlyMcDude]

Mustafar. Understanding what you said, shouldn't a rainbow look like glitter rather than the different bands ?

[@xdsone]

Why not deploy relay stations in orbt to amplify signals from our long range drones and satellites?

[@peterpalumbo1963]

I had no idea distances between asteroids, etc. Were so far!

[@NRRenggli]

Tatooine ☀️ ☀️

[@galaxia4709]

I think Invisible Entity would be a better name? Or Unknown Entity better yet?

[@sirlordofderp]

16:02 im pretty sure if we got the magical legislative body that was all very pro science we could do it in a few dozen years.