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

"Dark knocking sound" 💀. Coruscant

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

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

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

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.

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.

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.

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.

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.

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.

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

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

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.

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.

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.

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! 😊

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

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

QUESTION: Are comets mostly rubble-pile objects?

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

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

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.

Always enjoyable.

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

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

Hoth Very good question. Even better answer.

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.

Love your show

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

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 👍

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?

Hoth. Grreat Q&A!

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

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 !

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.

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!

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.

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

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?

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

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.

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?

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

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.

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

I had no idea the distance between space rocks were so vast.

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?

[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?

Got Naboo on the mind👍🏾

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.

Dagoba A great practical answer

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.)

[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.

[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?

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!

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?

How do we know the universe is expanding, rather than the speed of light changing over time?

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.?

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

It's not just "is there intelligent life in the universe." It's also is there presently intelligent life in the universe. There could have been millions of inhabited worlds, a billion years ago...

mandalore- if you can see it, it's pulling you to where it was.

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.

they are able to map out the location of dark matter through its gravitational lensing effects, and galaxies have been found that do not appear to have dark matter. I wonder what their rotation rates reflect in terms of their mass

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.)

If there was no interstellar dust how much brighter would the night sky be?

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.

I was sitting here putting peanut🥜butter on my crackers and eating them while I was👀watching this episode...🤘🏼💯✔️

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?

I argue dark matter should be renamed 'Placeholder 1'

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

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

Speaking of fusion drives I've seen a video by the Angry Astronaut by a company called helios they are actually working on a fusion drive space ship.

Mandalore 👌🤯

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".

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

Could Dark Matter be a defunct, older universe?

Spaceships made from Ice! Now there's an idea

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?

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?

Tatooine ☀️ ☀️

the ultimate future toilet will be some nanite swarm that hangs out in your colon and bladder 24/7 and turns all matter to something useful or gas that is converted to be sterile and odorless and be able to be controlled so that you can choose the time when its necessary to fart lol

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

[Tatooine] hmmm ... I was duped. 😊

Coruscant!

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?)

It is important to note that the Oort Cloud is a hypothesized region of space that we can not observe with current technology. I personally do not buy the underlying assumptions that lead to assuming an Oort Cloud exists.

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

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

Bespin. If aliens exist that's why they haven't talked to us yet - because they know we're the most ornery species in the universe.

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)?

Hoth: wouldn't it also take way too long. If we imagine our signals travel at the speed of light, itll still take like 4 years to get to alpha centauri

[Coruscant] SPOOKY ENERGY

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?

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?

How do we know red dwarfs are fully convective?

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?

Bespin What a spooky thought, the political unrest that would come from an alien signal with any kind of instructions would be considerable.

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?

[Naboo] for me 👍

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