Stuck in a Space Station, Black Holes' Habitable Zones, Human-Rated Starship | Q&A 210

Is there a habitable zone around a black hole? Can you get stuck in the middle of a big space station? How will Starship get human-rated? Why is the Fermi Paradox even a paradox? All this in this week's Q&A!
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00:00 Start
01:03 [Tatooine] Can you get stuck in a space station?
06:07 [Coruscant] How is Fermi Paradox even a paradox?
09:33 [Hoth] Is there a habitable zone around a black hole?
14:46 [Naboo] What are the highest velocities stars have been recorded travelling?
16:55 [Kamino] Will galaxies fall apart?
20:34 [Bespin] Why is there a Crisis in Cosmology?
23:06 [Mustafar] Is Starship good for humans?
26:41 [Alderaan] What will investment in space look like in the future?
30:07 [Dagobah] How to observe dark matter?
32:56 [Yavin] What's the origin of our Solar System?
36:44 [Mandalore] How long till the sports on other planets?
38:52 [Geonosis] Is there oil on Mars?
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[@ravensrulzaviation]

I fly down to the gulf coast of Florida, Sarasota, on Saturday, staying with parents in Venice for 4-6 weeks, will be heading over to the Space Coast for some launches finally!!!!! I am so excited, first one.

[@brick6347]

25:00 There's no escape option for a 747 either. They don't crash often, but when they do: game over man, game over. But statistically speaking, it's unlikely to happen. I think Starship 17.0 is probably going to be the same... but I ain't getting on version 1.0 to 16.0

[@originalmin]

Brick 🧱🗿

[@realzachfluke1]

I love the relaxing music on all of these modern episodes. It's so calming.

[@ProfessorJayTee]

I like the music as long as they DON'T use the ones which rapidly "wobble" the volume on and off. (I don't know what to call that.) The moment that crap begins, my brain simply cannot understand the words of the narrator until it stops. No idea why, but there it is.

[@sulljoh1]

If I was Fraser, I would pull my phone out and start playing this music in everyday life

[@videosbymathew]

The Fermi Paradox is not a paradox imo. It can only be a paradox if there's no apparent reasonable solution (and assumptions on what 'should' be occurring is not enough to fulfill this lack of evidence), thus the paradox part of the name. There are in fact several solutions via the great filter and various other reasonings (together these reasoning can discount the 1%, .1% etc. chances of various scenarios). The most obvious starter answer is "we're alone", the second being "we're the first", and then it gets more intricate and multi-layered from there. It'd be more appropriate to call it the "Fermi Conundrum" if anything, but alas, we have a name :).

[@Boudiccanyc]

This is the truth 100%. Been saying it for years. Proves that physicists may be good at math but they suck at words for the most part lmaoooo

[@frasercain]

I love that term. The Fermi Conundrum. 😀

[@wayando]

It's a paradox because all the possible solutions are just guesses ... But the reality is that there are no apparent aliens, like non, where there should technically be everywhere.

[@videosbymathew]

@@wayando Sorry, but no, that's not what the definition of a paradox means. And no, they shouldn't technically be everywhere when we have solutions to why they wouldn't be... thus not a paradox.

[@Rattus-Norvegicus]

Try telling that to John Michael Godier, he's convinced aliens are among us.

[@runningray]

HOTH. I think the strange stuff that is happening around black holes will continue to blow our minds for a long time to come.

[@michaelmcconnell7302]

TATOOINE this week. Hard to imagine how somebody would end up perfectly still in the middle of a big empty room in space, but I love the image 😄

[@DerInterloper]

An especially grabbing episode. Thank you Fraser!

[@JohnSostrom]

Excellent Q&A. Thank you.

[@alfonsopayra]

man i love your question's show :)

[@steverobbins4872]

There was a great science fiction series by Fredrick Pohl where aliens called the Heechee lived near the event horizon of a black hole. Very popular series that ran from 1977 to 2004. Five novels. RIP Fred.

[@erikwright2693]

I often slow your videos to .75 speed. Makes listening more enjoyable and easier to comprehend.

[@dontactlikeUdonkno]

Crisis in cosmology follow-up question-we do currently accept that there is a dark energy (or similar force); wouldn't that, in and of itself, alleviate the 'crisis' state? Scientific consensus is that the rate of expansion of the universe has changed/increased over time, so if the values actually *did* line up, with such an extreme difference time, wouldn't that be more of a crisis? Thank you for all of your content. Top shelf 😉

[@ProfessorJayTee]

(Mustafar) I think a Starship orbital flight followed by that amazing landing profile would be an awesome experience. Better than any roller coaster ever built! Beats the hell out of Blue Origins' 11 minute capsule experience.

[@LordZordid]

Great questions and answers. Well done everyone. :)

[@mbj__]

Coruscant. Excellent answer. Clear and informative 👍

[@brantwedel]

HOTH!! (Sorry, I had to vote before finishing the video, the blue shifted cosmic background was awesome!) 🤯

[@DneilB007]

Hey Fraser, I’m just at the Fermi Paradox part of the video (9:13) and I have to ask why the answer to the question of, “where are the self-replicating robots?” can’t be “watching this video on KZbin.” The Great Oxygenation Event has one life form “suddenly” spring up and completely alter the planet such that essentially no life forms that might have existed prior to the event could exist after the event, and then replace the existing life forms with new ones that are compatible with the environment they created. Couldn’t the answer to the Fermi Paradox be, “we’re right here.”

[@topcat56]

(Hoth). Learned so much about what can create a “habitable planet”!

[@iliketrains0pwned]

25:23 Fraser Cain: "Spaceflight is never safe!" Scott Manley: _Sweating nervously_

[@faizanrana2998]

HIW DARE YOU COMPARE FRAZIER TO SCOTT MANLEY

[@FinnishArmy]

your show is so easy to fall asleep to

[@bbbenj]

Tatooine is so fun! I vote for this question, of course 😅

[@tyrred]

Yavin Such a great question... I've always wondered this.

[@bbbl67]

[Hoth] Another hypothetical source of radiation for a planet would be Unruh radiation. This is similar in some respects to Hawking radiation, but instead of coming from the evaporation of the black hole, it comes from getting close to the speed of light. The closer you get to the speed of light, the higher the energy level. So presumably if you're somewhat close to the event horizon, you would need to be orbiting pretty fast to stay in orbit. Unruh radiation comes from the direction of travel which is moving closest to the speed of light. It's radiation that comes from the horizon of the universe itself.

[@frasercain]

Oooh, good one, I totally forgot about that. And I guess there's the photon sphere too, which could warm you up... for the rest of your short life.

[@malsYT]

Bro... question 1, surrounded by air, inhale, exhale (blow), propulsion.

[@TheyCallMeNewb]

Even upon waiting until the end as intimated, Tatooine at the beginning clinches it.

[@wolfynautious7415]

Hoth! Very interesting question.

[@philipkeogan3550]

Don't forget "Rocket Labs" in New Zealand

[@rebellion-starwars]

Hate when I miss live show... Its great live. Actually my notification doesn't showing up idk and ofc I turn on my notifications. Ppl live show have many more questions and answers.

[@simonjennings5458]

cheers for the spider bit i am not gonna sleep for weeks now lol thankyou for another great show

[@PetraKann]

Question 1: Whilst density is an important parameter when examining buoyancy, it is viscosity thar determines the resistance to flow. An example is honey which has a density of 1,400 kg/m3 compared to water which is in the same range 1,000 kg/m3. However the viscosity of honey (~5,000 cps) is at least 3 orders of magnitude greater than the viscosity of water (1 cps). In fact you can have two fluids with almost identical density but vastly different viscosity. Having said that the dimensional quantity Reynolds Number, Includes both density and viscosity as well as flow geometry, and describes the type of flow: it laminar or turbulent flow conditions.

[@Nk36745]

Tatooine - imagine taking a bird to the ISS, fascinating

[@stevenscharmer1765]

Yavin. As for Fermi, my hunch is that intelligent life is so exceedingly rare that other active civilizations would be in other galaxies, and we'd never know of each other.

[@laurachapple6795]

"That spider found you." WHY did you have to phrase it like THAT?!

[@Czeckie]

thank you for Bespin. When I learned about the Hubble tension I was puzzled about why do they even assume that Hubble constant is actually a constant? I haven't appreciated that's in fact potentially the result - expansion is more complicated.

[@bit-tuber8126]

Recall reading, like during the Skylab era, astronauts could just be very still to let the air circulation move them within reach of something to grab on. When something goes missing the air intake grates were the places to look for small lost stuff.

[@oldered5663]

Stuck in the middle of a sphere problem: Hold head over left shoulder take deep breath, turn head forward, Blow the air out, hold head over right shoulder, breathe in deeply, turn head forward BLOW AIR OUT. Repeat..... The net effect will push you backwards

[@moozoowizard]

My first thought too

[@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?

[@marvinmauldin4361]

Years ago I read that it had been spectroscopically determined that the Pleiades cluster is coincidentally moving through a gas cloud that makes it appear that they are still in their birth cloud. Futurama had a competition in a large dome on the Moon where women wore butterfly like wings, and flew around trying to make each other crash in a kind of flying tag team wrestling match.

[@prozacgod]

I for one can't wait until I see a paintball game played in an escher like game dome, in full 3d flight on the moon.

[@duckgoesquack4514]

12:07 just had an epiphany question: black holes blueshift light, would radiation at the event horizon be plonk wave length or very close to it?

[@gigopepo]

Question: Is there a chance that, with enough time and the right conditions, future supernovas can create exotic new elements just like they created Gold and others in the past?

[@JohnDlugosz]

You can find a version of the periodic table that shows which elements come from which processes, including supernovas. This table lists _all_ the elements; there are no gaps.

[@strcat666]

The late belly flop tests were done to see how little fuel is needed to land. Fuel is mass and the less fuel the more payload can be lifted. If a star ship is used as an escape pod from an issue with the buster the star ship will be full of fuel with no reason to do a late transition vertical flight. Thus this escape landing will be more like the falcon booster landing program with so many perfect landings. P.S. The star ship tests last year ended due to the bad public relation issues and the last landing was programmed with the test data gathered to make that perfect landing. Yes there were other issues but I degrees ... That is why testing is done.

[@charjl96]

Tatooine. I've been wondering that too, but more in the sense of wondering if the air would slow you down

[@metroidmania8833]

HOTH is definitely my pick this week. I wrote a song entitled "Spanning the Accretion", very Third Stone From the Sun-esk, that bleeds into the next song "Escape From". It's about an Interstellar crew of astronauts that crash on an inhabited planet in the habitable zone of an Accretion disk of a super massive black hole. I am considering making it a concept album.

[@-OICU812-]

Use a cordless fan for propulsion! I would love to see that! even better, hookup a series of tubes to the fan's output, add a computer-controlled joystick, and make it totally maneuverable! I'd REALLY love to see that! great video! I provide unto thee my personal thumbs up!

[@JohnDlugosz]

Such things have been tried on board the ISS. I think they have a flying tablet working now.

[@xkot6431]

I didn't scrub through all the comments, so I don't know if anyone mentioned this, but Isaac Asimov wrote a short story about the "swimming" problem. It involved future astronauts trying to create wings to fly in a large volume of zero-g. The wings didn't work well. Then someone had the bright idea to design a suit more like a dolphin shape, since moving through a large air-filled zero-g volume is more like swimming than flying.

[@microschandran]

Many good ones today, vote is for Coruscant.

[@everettputerbaugh3996]

As a spiral galaxy with a black hole at the center, aren't we already living in the accretion disk of a black hole?

[@MS-od7je]

It is ( imho) a Hall effect, by which I mean that the two measures are accurate but one measures the rise and the other the run… the staircase feature… a Hall effect jog time/space

[@j7ndominica051]

That's interesting that with time dilation the amount of light that would have fallen in 10 thousand days would now fall in one. I've never thought about it like that. The blue shift in itself wouldn't be that beneficial without an increase in intensity. Except that you'd probably have x and gamma rays that are not good for habitability.

[@cannes76]

In regards to the Naboo question: How about orbital velocities? Isn't there one of the stars observed around Sagitarius A* sped up to 2% the speed of light on closest approach? Edit. Purr morg-gensen XD. Always entertaining when people attempt to pronounce danish names!

[@JohnDlugosz]

At 2% lightspeed you would measure the time dilation using instruments, but it would not be noticeable most of the time. You have to get more like 60% or 80% lightspeed to be considered in the relativistic regime.

[@smeer001]

Here is a question that I have wondered about for a while - If the event horizon of a black hole traps all matter, energy, and information inside it, because nothing can travel faster than the speed of light, since the effect of gravity travels at the speed of light as well, how does a black hole emit the force of gravity?

[@dontactlikeUdonkno]

Do you think that being in a highly metal-rich star system may be crucial for an intelligence to develop technology? This is considering our reliance on heavier metals for technology-for nuclear fission, for semi-conductors, etc. You had mentioned that there must have been a kilonova that enriched our stellar 'nursery' nebula within an extremely short amount of time of the solar system starting to form (only a few million years)-that must have given us a massive advantage in terms of industry and technology, right? Love your content as always

[@dontactlikeUdonkno]

looking at NASA's 'origin of elements' periodic table... if we were missing all of the metals that were caused by merging neutron stars... we wouldn't be anywhere near where we are now. All uranium, plutonium, most silver, almost all of gold, and much more.

[@Cs137matt]

For the question about starship I feel they are going to reconsider having passengers on it while it performs the flip N burn maneuver. Tim Dodd from KZbin channel the everyday astronaut who coincidentally is now going to be a astronaut in the future, believes that they will design a different starship more like a shuttle type of craft that will be able to glide in and land similarly to the shuttle

[@stevenscharmer1765]

Another option would be to have more fuel left such that the ship wouldn't need to flip near the end, and instead can come out of the belly flop much sooner and more gradually. But this would mean your launch payload would be smaller (in pounds).

[@colinrousseau8803]

How do we know for sure that dark matter isn't just black holes without an accretion disk, those would be invisble but still have mass?

[@JohnDlugosz]

Gravitational lensing observations, and models of galaxy formation.

[@OslerWannabe]

The solution to the Fermi Paradox is simple. No intelligent, creative species can survive long enough to do something which will get them noticed. And that includes us. The reason for it has been overlooked by nearly everyone. How do individuals within a species move up the evolutionary ladder? By identifying environmental niches which offer opportunity. Generally speaking, they do not simply drift into that niche; they compete for it with other species, or other individuals of their own species. And once they lay claim to that niche, do they just set up housekeeping and start polishing the silver? No, they continue the process, looking for further opportunities, competing for them. This process is entropy-driven; if it is not thermodynamically forbidden, it is inevitable. If individuals can find a niche which gives the same or greater ΔS for an expenditure of less energy, they will move into competition for that niche. One of the contestants will win, the others will lose. At some level of the evolutionary ladder, the "selection" in natural selection will begin to involve agents which have some level of sentience, and elements of free will, cognition, planning and more will contribute to the selective process. When the species achieves a level of technology which allows the possibility of a single individual terminating civilization, the path of entropy maximization will lie open to him, and possibility will become probability, and then certainty. Someone who knows that he has his god's ear will visit divine retribution for the sins of his species. That inevitability has undoubtedly played out many times in our galaxy, and we are rolling downhill toward the Great Filter, which blocks further progression along our species' narrative. Personally, I believe that we are within 2 generations of it now.

[@forbiddenera]

I never get notifications on time even when bell'd, if I get them at all!

[@duckgoesquack4514]

1:14 Would this work: look up and takea breath, and then look down and blow the air out

[@cacogenicist]

I think crewed ascent in Starship will be clearly very safe long before descent. I can imagine Starship docking to commercial stations where Crew Dragons (or some other highly safe descent vehicles) are docked, with the crew then getting off Starship and descending in capsules. Or, if after some years, SpaceX or whatever regulators are not satisfied with Starship's safety status for crewed descent, perhaps SpaceX will build a more conventional, but large, capsule that can take people up to and down from LEO on top of a Super Heavy booster. Maybe they would consider building something like Stoke's second stage, for the sake of rapid reusability.

[@patrickdaly1088]

Tatooine was a great question and it got me thinking, I actually have a question to expand on it a bit. I know there are tricks you can do with rotation, stick your arms out far to the sides, swing them both in the same direction and then pull them in to reset, where you could build up some rotational velocity. For an astronaut stuck out on a spacewalk, could they build up some rotational velocity, and then switch to only using one arm, to translate some of that rotational speed into movement because the forces are no longer radially symmetrical?

[@ericv738]

If they're able to build rotational velocity, they should be able to build directional velocity using the same propellant.

[@dontactlikeUdonkno]

I was thinking a similar sort of thing. But then I was thinking that *maybe* the friction we have here on earth may allow that sort of induced movement. Like in an office chair, I can get it to spin without touching anything by swinging my arms, but if there were no friction to allow me to reset my position, it probably isn't possible (since there's no friction/resistance to work against the "equal and opposite reaction"). Interested in hearing your thoughts :)

[@patrickdaly1088]

@@dontactlikeUdonkno If you can build up speed over multiple swings, IE have some rotational velocity at the end of one entire cycle of arm movements, I think it works out. The trick to resetting your position and not losing your work, is to not take the same path back to the start; I'm thinking to take advantage of different moments of rotational inertia. When your arms are out, if they both move in the same direction, your body spins the other way. Then if you retract them, I think near the end of the swing or right at the end, you can move them back to the original position with them closer to your body. Might take some practice, and I'm no expert on the subject, but I think if you can build up some rotational speed on an office chair, that's proof of concept. The office chair friction only hurts, and air is negligible here.

[@TeeTekTrab]

What if you could take a significant portion Earth's mass like dirt and rock and gather it in one place(like the north or south pole)? Would that change the Earth's orbit, rotation or tilt?

[@Bow-to-the-absurd]

Also, a capsule is a pressurised, sealed environment, it also experiences micro gravity, as opposed to zero g.

[@nochance3914]

Hello Fraser I have a question. There is one Giant Meterwave Radio Telescope near Pune India. I want to ask how many miles or kilometers of Isolation type environment is needed for the proper functioning of such Radio Telescope? There is one proposal of High speed Railway going from same area and now some people want to stop the progress of that HSR. Do we need harsh isolation requirements like Ligo observatory even in case of radio telescopes?

[@jblob5764]

Very good question

[@grahamhill676]

Hypervelocity stars: the stars around Sag A* like S2 travel a significant amount of C. I think the highest was like 0.4C at one of the star's perihelion to Sag A*.

[@czerskip]

Hoth. Let's see the future!

[@NikolaCvetkovic78]

Question -How it is possible ? : Imagine today is Friday and ask people - What day is tomorrow ? All will say - Tomorrow is Saturday! Saturday didnt happen and we all know that tomorrow is Saturday ! BUT when you ask people what is beyond the edge of universe ? They dont know answer. So maybe Universe beyond end of universe didnt happen like Saturday. As time passing every second Universe is bigger and bigger and only problem is that we dont know how to measure Universe expansion like time.

[@carlfollmer1767]

Lagrange points! Now that I have your attention, is there any indication that our solar system has a comparatively greater amount of heavy elements than others? Or does every star system need a neutron star collision to provide enough material for a star and planets? Yavin for this week's question vote.

[@disinclinedto-state9485]

Hey, Fraser. I've often wondered where all the material "goes" that falls into a black hole. Does time dilation make the "experience" of some particle falling in that the universe outside gets faster and faster for a few seconds and then it finds itself radiating out of the black hole a few seconds later while the universe outside is so old it has nearly achieved heat death?

[@ericv738]

Fantastic question.

[@ashleyobrien4937]

most of the matter that is falling into a black hole never actually passes the event horizon, usually it is accelerated to the point that it emits radiation and then itself is ejected prior to getting close to the event horizon because the matter density is so high , combined with the rotational energy it is ejected as jets.

[@wayando]

Technically inside the event horizon time would seem to stop, so entering the leaving would seem like no time at all ... Even if trillions of years would have passed outside. The problem, though, is how to escape and tell the story ... And to whom would the story be told.

[@user-pf5xq3lq8i]

Maybe all intelligent life goes into the hole to live. Where time doesn't matter.

[@jaredtbrush]

With the recent success of DART and the information we obtained about deflecting an astroid. If we discovered a devastating asteroid about to hit earth in 1 week, are we surviving it, is that enough time to react??? Love the channel keep it up 👍

[@scooterdon8365]

Gradual drag decelerating ISS should slowly send indoors naut to fwd wall… also might expelling air induce small thrust (point feet at fwd wall,look at aft wall and blow, look at feet and inhale, blow…) There is a business in FR offering chance to SWIM hanging from small neutral buoyant aerostats (balloons)

[@ravensrulzaviation]

By the way, a friend of mine lives over in Vancouver, he is a plane spotter, at their airport. Beautiful background.

[@pbourd]

Yavin, solar sister stars & nebula event rollback

[@nagoh04]

Coruscant Thanks Fraser

[@AvyScottandFlower]

Regarding my question on the show, I was referring to the possibility of landing the upper stage of Starship as a glider (maybe on regular, commercial airports around the world), not propulsively. Tim Dodd alluded to it on his interview with Lex Friedman, I thought it was quite an interesting possibility, not even Elon has ever talked about it. Throwing some quick numbers, the upper stage is about 50-55m long, vs about 64 to 74m for a 777. Wingspan should be inferior or at most similar, and its dry weight (so far) is only 85 tons, vs about 371,600 lb or 168.6 tons, for a 777. Plus the control surfaces of Starship can obviously be modified for it, on a point-to-point variation.

[@themeach011]

Just guessing here but that would slow down the rapidly reusable design. The idea is u don't need a runway. U land it on the chopsticks restack it on the booster and away u go. Also there's no runways on Mars or the moon. I would also assume that adding landing gear and wings would add a lot of weight and complexity that u don't need if u just land it the way they are. Once u glide it in there then what do you do with it? How do u transport it back to a launch tower? Makes more sense for reusability if u can land it back at the launch platform

[@AvyScottandFlower]

@@themeach011 I was referring specifically to the Earth-only, point-to-point future variant of Starship, which Tim was talking about on that interview. But you're right, transporting the upper stage back from an airport to a launch tower would be a problem. Who knows, maybe that type of upper stage could also take off horizontally, like an aircraft. I imagine the ultra-cooled fuel mix would still pose a challenge, then.

[@Slikx666]

In response to the hoth question. If we say that there's a planet that's in a stable orbit and humans colonized it, we would probably try to have bases all around it but there would be an issue. Mr Smith decides to call Mr Jones on the other side of the planet, would they be able to talk to each other? If the planet is tidally locked then there would be a difference in the speed of time between the different sides and it could mean that someone sounds like a mouse and the other sounds like a foghorn. If the planet is turning then the best time to talk with the other person would be around holeset / holerise. I'd probably just send an email as long as there's a communication cable connecting them. There's also the weird thing that could happen on a planet the revolves, is the day and night time the same length? Would nighttime be quicker? Would there be night? How about the thought that in the day you could be quite a bit taller than at night. Would it cause you to have a bad back? But in the end it a case of the bigger the planet and the closer to the black hole the worse it'll be. I think if life were native to the planet then it would be a short being that lives a simple life and there would be no coffee!

[@gryph01]

Courscant. I think the sheer size of the galaxy and the distances involved means that we just haven't seen any evidence of life elsewhere. Question: How is quantum physics changing astronomy?

[@KenMathis1]

[Coruscant] The problem with the Fermi Paradox is the assumption that intelligent life would spread out. Space is so large, and habitable systems are so spread out that there is no reason to travel any significant distance from your home system. It's also highly unlikely that you'd get a significantly sized starship to stay functional for the long time needed to make an interstellar trip. The amount of redundancy you'd have to include would be prohibitively heavy for anything more than a small probe. Instead it makes a lot more sense to passively explore the galaxy by building ever larger and more sophisticated telescopes. Oh and if you spot another system with intelligent life, you send a communication signal directly to that system. You wouldn't send a general broadcast because that's far less efficient. That'd be the way civilizations explored the galaxy, and it would be largely undetectable to us now. There could be a galactic civilization network out there directly communicating with one another. There'd never be a need for a civilization to send probes across the galaxy. They would just tap into that galactic network when their tech is high enough to spot intelligent life from a distance and send a "hello" message. The other side says "hi" back, sends all the tech and space exploring info they've gathered from the network, and tells the young civilization of any other nearby civilizations they should connect to in order to expand the network. Oh, and if there is something interesting near the young civilization that's worth exploring, they'll ask them to do so and broadcast on the network what they've found. So at most you'd only send small probes to nearby systems. Why do more when you've just gained access to millions of years of exploration data from other civilizations for the rest of the galaxy? In short, once a civilization spots signs of other intelligent life, communication, not physical travel, becomes the primary means of exploration. That and the extreme difficulty is why the galaxy isn't filled with probes.

[@ChristSimd]

You can already play Ender's game sports in VR! It is called Echo Arena

[@7heHorror]

Coruscant. Technically it's not a paradox. There *is* a solution, we just don't know what it is. Thanks Fraser!

[@kaarlimakela3413]

So these are perfect spots for the Restaurant at the End of the Universe to develop franchises!

[@JohnDlugosz]

[Hoth] See also a Greg Egan novel concerning a self-engineered life form that lives in the accretion disk of a black hole.

[@PetraKann]

The Density of oil can be lower than that of water and yet its viscosity is much higher. It is much more difficult to swim through a viscous oil than water. Density relates to buoyancy effects rather than viscosity

[@nerufer]

(Hoth). If you would orbit a massive black hole and you would enter the event horizon (point of no return). But you would somehow have a very long rope that you would hold as you go over the event horizon. Could u still send a signal with said rope to a person holding the end of the rope who is outside of the event horizon? For example, if i would pull the rope a little bit, would that person feel my pull? (if yes, i could in theory send a code and tell this person what i'm seeing).

[@JohnDlugosz]

Nope. In fact Greg Egan did calculations concerning "black hole fishing" in one of the math forums (I think it was Math StackExchange but I'm not sure). Short answer: if you pull the rope, it will break.

[@ericvulgate]

I understood that recent discoveries indicate that Andromeda and the milky way may already be touching.

[@emptyfield5250]

Since things tend to either fall into black holes or get ejected, is that why a closed universe leads to a big crunch? If the universe eventually wraps back around, inevitably everything will find its way into a black hole, and eventually all those black holes will merge into one universe mass black hole?

[@kenmccarty6229]

The assumption of the Fermi paradox is that over extended periods of time travel between star systems would be relatively easy for a sufficiently advanced civilization, especially for one using self-replicating robotic probes. Let's assume instead that it is exceedingly difficult (not impossible). We don't know how difficult creating such probes would be because in our experience no such thing has ever been done before. We just assume in the paradox that it is inevitable. That may not be the case, even if civilizations can eventually spread to an additional star system. Exceedingly difficult is more in line with what we currently know. In other words although we currently seem to be on a exponential curve for the increase in technology, that situation is transitory. For most periods of civilization, technology tends to remain the same. We are just in an extraordinary growth period of humanity's technological existence, which will eventually become stable again---basically it will eventually flat line. What do we actually know instead of assumptions? We know that a technological civilization is possible because we have become one. But we have little idea of how likely that occurrence is because we only know one example of it happening. But let's ask a simple question which we potentially could answer with more research. How many species with sufficient intelligence could eventually develop technology to do so? We need a ratio to add to the Drake equation. We know for a fact that humans are not the only species on earth currently that can solve problems. But currently we are the only species that comes together as a community to do so with a memory system to pass that knowledge onto the next generation. Maybe that is the key. Maybe passing on knowledge to future generations is exceedingly difficult, even though we have become pretty good at it. Elephants, whales, dolphins, some species of birds, octopus are a few examples of high intelligence species in nature with problem solving abilities. Also, do we count sister human species of the past that potentially could have done the same thing as us but didn't? This technological moment in our existence may be what is exceedingly rare and maybe so improbable that it could explain the Fermi paradox.

[@TheRolemodel1337]

5:14 you could also use solar radiation to move around and use your body as a solar sail 11:33 for a feeding small black hole the habitable zone might be inside its innermost stable orbit at times 13:33 the temperature is dependent of energy influx are you sure the CMB would translate into useable warmth instead of a dim infrared glow? it wouldnt be nice to be cold while being roasted by x rays

[@JohnDlugosz]

[Tatoonie] If you built something like a jet-ski with a huge funnel intake that let you propel yourself in the thin fluid of the exosphere, or any other form of "swimming", the velocity would build up over time as you continue to thrust. The terminal velocity would be so much higher as to not apply on these time scales. So, it would not take you X times longer to cross a span with 1/X density; it would be a quadratic relationship. For a long distance, you would build up a high velocity and cross it quicker.

[@werkstattkreuzberg4234]

"Is there a habitable zone around a black hole?" My first answer was LOL. My second answer is yes. Because we live there ;-)

[@Eddyfamily]

Question: the current definition of planet includes “has cleared the neighbourhood around its orbit”. Pluto is not a planet by this definition. However Pluto crosses the orbit of Neptune. As Neptune has not “cleared” it’s orbit does that mean Neptune is not a planet? Bonus question. What objects has Pluto not cleared that prevents it from being a planet (that has never been clear to me)?

[@peterwoitalla5265]

The reason of two different numbers that don’t line up could be because of the differences in flex of it’s waves due to the density of what you are measuring?

[@Niohimself]

If KSP taught me anything, then being just outside the space station, you are actually on an ever-so-slightly different orbit - and therefore going at a different speed, meaning you might get pretty far from the space station in just half an orbit. Time's against you if you want to get back!

[@ainekosmanfred]

One of the strangest astronomical objects I've ever come across is Przybylski's Star. It seems to contain some very short half-life elements. How could this be? What are the best current theories so far that could explain this?

[@ashleyobrien4937]

that's easily explained, not all stars are like ours, a low metallicity yellow dwarf, many stars are composed of the nebulae from exploded stars, thus they contain higher amounts of many other elements , not just hydrogen, so, in the core there can be all kinds of nuclear reactions going on, not just the usual fusion of hydrogen...

[@jackesioto]

Will the individual galaxies fall apart? It depends on whether the Big Rip will pan out or not. The idea is that the exponential acceleration of the universe's expansion may get such that eventually, this expansion would overcome any forces binding atoms together

[@gajnjaca]

Hi Fraser, excellent video as usual 🙂 I have a question. Is there such a thing as galactic equivalent to solar “goldilocks zone”? Looking at our location in the Milky Way made me think about living in a quiet suburb. So would there be a negative consequence being located too close to galactic center, where too much activity could have negative effects on development of life, equivalent to too much heat too close to the Sun. And on the other hand, being too far on the edge of the galaxy spiral could expose life to intergalactic radiation (if there is such a thing 😊) assuming there is galactic equivalent to the Heliosphere.

[@user-pf5xq3lq8i]

Yes, same thing, he explained it in a video. Too close to the centre is to much destruction/radiation going on, too far out there is nothing going on. Our sun is in the galactic Goldilocks zone, we are on the outer side of the goldilocks zone, plenty more to explore safely inwards. It is a much wider zone relative to the galaxy, than a star system Goldilocks which is actually quite small. Maybe less than 2% at a guess is Goldilocks zone in a star system, whereas more than 30% of a galaxy is in the Goldilocks zone.

[@Raz.C]

Re - Coruscant Maybe they won't be self-assembling in that they make more of themselves, but rather, once they get to (for example) Altair, they start building a portal/ gate or some such, so that we can instantly travel from the Sol gate- in earth orbit- to the Altair gate (ideally in orbit of a goldilocks planet orbiting the star). Maybe once they build this gate, the robot then builds two copies of itself, sends one to Tau Ceti and the other one to Barnard's Star. One THEY arrive, each one starts to build portals/ gates in those systems and then we have 4 systems that we can instantly travel between... A lot of 4-X type space games have a similar theme, where you have to send a SLOW-arse construction unit to a new star system to build a gate, which you can then use for instant travel between other functional gates. This whole pipe-dream depends, of course, on being able to actually build such wormhole type gates in the first place...

[@trolly4233]

If we don’t make a centrifugal space station, just a really big air tube, it would be awesome to see people literally flying using little flippers on their hand, or a backpack fan, or a tiny atmospheric rig that would just pump air in and push it out in different directions at high pressure

[@Raz.C]

Re - Hoth "Another possibility is that you have neutrino flux..." Yeah!! I went to this new Indian restaurant and though it was a wonderful experience, once I got home, I ended up suffering from some really bad neutrino flux!! Had to put up a sign in front of the toilet, reading: "Lasciate Ogni Speranza Void Entrate!"

[@davidmcsween]

Do hyper stars leave a wake we could detect, closer to light speed could the have a damaging bow wave?

[@m4ilm4n]

Geologist here. You need no plate tectonics for oil and coal. You need appropriate organic matter that gets deposited in a basin where no other life can eat it (e.g. no oxygen there) and then covered with additional sediments. The burial depth needs to be large enough so that a) pressure is high enough and b) temperature also is, which is dependent on the geothermal gradient. If your organic deposits get subducted, they will be under different kinds of pressure and temperature that shouldn't allow for oil/coal formation, but I'm not entirely sure. Minor error: Oil is made from algae, not bacteria.

[@frasercain]

Thanks a lot. I'll do a little more digging based on this and see if these conditions were present on Mars for long enough.