Wow I'm shocked and extremely honored to have been mentioned at the end, thank you so much!

VENDIKAR hands down. Whether that question was prepared for in advance or whether Fraser answered it on the spot is completely immaterial, because to my great satisfaction his answer _lands for me._ Talking about Unruh radiation had concepts clicking in my head that I never managed to take away from watching and rewatching the series of PBS Space Time videos that include the Unruh effect in the build up to grasp concepts like Hawking radiation, the black hole information paradox, and ultimately the holographic principle, which I had done multiple times in my life because I've loved Space Time since the start and enjoy watching it, but also because it always stuck out in my head that the Unruh effect and Unruh radiation were such memorable names to me, and yet I never found myself grasping and holding onto the explanations for them. So to put it succinctly my understanding of many ideas covered in PBS Space Time simply suffered because I was missing some foundational, building block concepts that ended up being way more vital than I imagined. I've heard the explanations for Hawking radiation many times before, and for several years I've been able to tell you that a black hole's size is directly proportional to the theoretical Hawking radiation it emits, with the smaller sizes evaporating quicker and appearing "hotter" than larger black holes. But when I heard that answer, it made me stop in my tracks wondering if what I'd heard was right, specifically because I understood it and hadn't in the past. I went back to the PBS videos on horizon radiation and Unruh radiation, and to my enormous gratitude, satisfaction and excitement, Fraser's answer led me to going back and successfully learning so many *wonderful concepts* that didn't stick before. Thank you to both the questioner and Fraser for that answer. I waited til the end of the show too so I'm very sure in my vote for this one.

I love space news, and for me, this was probably the most informative (or at least eye opening) episode you've ever done. From the correction of the common misconception as to how black holes shrink, to the true color of the moon, to what a lunar eclipse on the moon would like you. Loved it!

Such a great presentation with awesome information. At a time when science and space videos are popular, it’s great to find a channel dedicated to current and accurate information without the hype and untruthful headlines/ clickbait crap that is now common among science channels. Thank you!!

I just absolutely love listening to your Q&A. Seeing you answer questions looking straight into the camera it feels like you are talking to me! I know everybody does that but there is definitely something about your angle or something which makes it look so peaceful. The pace of your voice puts me to sleep often and I come back to complete the video!!

Vendikar. Your explanation is very illuminating. I was able to build a picture in my head thus I understand much more than I did previously.

Only want to tell you your amazing enthusiasm comes out of your eyes! 💪🏻😊

With the Lunar Thermal Battery they could install a large array of parabolic mirrors to focus intensified sun light onto it in order to super heat it for the 2 Earth week day cycle before allowing it to release over the 2 week night cycle.

Actually caught the live stream yesterday, thanks for answering my question.

Andoria's my pick! Love seeing this kind of enabling research for lunar exploration.

Thank you so much again Fraser.

Andoria. I always like to hear about super awesome technology, that already exist!

Cheleb. That was a great question!!!

[Cait] I've been wondering about a similar question for some time. We want to colonise the Moon. We are able to assemble spacecraft in space like the ISS. We could build a spacecraft, which could operate between orbits of Earth and Moon, with engines designed to operate in vacuum, not worrying about aerodynamics etc. We could launch rockets to the orbit, like we do constantly, refuel the spacecraft, put cargo inside and send it to the Moon colony. Isn't it better than constantly sending rockets with cargo to the Moon?

Really cool to watch you go through the questions! I get to see questions that I never thought of, and have more knowledge. Really cool!

Cheleb. I’ve also wondered since I was a kid about what an eclipse would look like from the surface of the Moon.

Vendikar. Thanks, Fraser. Unfortunately, many people continue to repeat the virtual particles version of Hawking Radiation. Same with singularities are 'infinitely dense' and of 'zero size'.

2. Rudy Krutar 2023 May 13 Sat 23:00 1. The idea that time slows down in some circumstances is ludicrous. 2. Relativity with Fewer Tears becomes less silly when we cast it as clocks slow down in those circumstances. 3. Likewise yardsticks shrink in similar circumstances. 3. Also, the speed of causality is an awkward notion. 1. We should take the Causality Field to be c-squared at each point in space, 2. which is exactly 1 square füt per nsec per nsec in a vacuum, 1. where 1 füt = 29.9792458 cm 2. note 1 füt < 1 foot = 30.48 cm 3. so c = 1 füt/nsec wherever attenuation is negligible 4. in any inertial frame of reference 5. c-squared is constant but füt and nsec are not. 6. so füt shrinks as nsec stretches 3. less in a lens, and 0 square feet per nanosecond per nanosecond in a perfect mirror. 4. Huygens' Principle has all energy entering a tiny region of space quickly emitted in all directions uniformly. 1. Cellular Automata based on this notion show real physics such as evanescent waves at critical angles 2. and inflationary expansion of distances as gravity slows causality.

I remember a song from Seattle called 'Compared to What' that reminded me of the sun.

Lots of good stuff here

Risa, although I was tempted to go with the Enceladus one. Because those moons are so interesting

Very good as always!!?

Thank you

Aeturen. I couldn’t type this fast enough. What a fantastic question.

one of the best shows ever. I like this site so much because this show is honest, it's fun to watch, and that's a rare combination. So a body with life, probably has water that is fluid for x-amount of time, and a gravity close to Mother Earth? In a perfect world, and contact has been made, how many years would it take to get caught up with the universe already used to technology? What would that even look like???

Regarding the cloud of almost-Hubbles, there was Planetary Resources’ old ARKYD project. They had aimed at having thousands of mass produced smallsat telescopes for asteroid prospecting.

Question: Astronomy: The further away objects on Earth are, the smaller they appear to us. What effect does this have on objects at astronomical distances? Do very distant objects appear much smaller to us than objects closer to us? Or are the angular dimensions negligible at such great distances because the angles are very small anyway? Thank you very much for your answers. The last Q&A show was another particularly good one, in my opinion. Thank you very much for your great work and your great channel.

Janus It reminds me of F1 night races where the black track looks like a ribbon of light against the darkness of night. It's all relative.

Hi Fraser a question Could we use a lunastationary orbiting complementary satellite which would beam heat down to a point on the nighttime moon surface which could keep a rover warm during those 14-day evenings?

I really like the moon temperature difference power generation. especially since the temperature differences are so huge. It should work great. andoria

Regarding the first question, Matt Ferrell (Undecided) just did a video on current gen sand energy storage that was an interesting look at the technology. Obviously it's focused on earth based applications, and his recent video is focused on residential stuff, but it's an interesting look at the technology.

Nimbus. I've been planning a KSP RSS Venus sample return for months, but I was away from the live show when this question was asked😭. In the game, it requires ~40 tons into LEO.

Thank you for the acknowledgement (as Muzz)

Hi Fraser, could there be any stars trapped in the Lagrange points between the milky way and Nubecula Major (LMC)?

[Andoria] because I like Shran just as a sidenote on Nimbus: water-moons is great, however, the question for me is; would they be able to hold onto that water? Would you get an atmosphere and can it hold onto it?

A good UKposts channel that really gets into the nitty gritty details of Artemis and current space stuff is Phillip Sloss.

There is only one possibility for a rover on the surface of Venus: we learn how to make the universe's highest temperature superconductor, so that a buoyant balloon-type probe, can sit at a temperature which is cold(ish) in the upper atmosphere. You would lower your rover to the surface using a graphene cable wrapped in superconductor. The rover would stay attached to the cable - with some slack, and the rover's systems would dump all the heat absorbed into the superconducting cable, which would be attached to a gigantic superconducting flag at the probe level. This would allow a nuclear-powered rover's important bits to stay at the ambient temperature of the upper atmosphere, because superconductors are... superconductors! But currently we have no way of joining or producing any room-temperature superconductors at all, and it is certain that when we build them, they will not be tolerant of 470 degrees C. We also have no idea how to produce a 70km long graphene cable with a breaking strain of thousands of tons, because a cable has to support its own weight, as well as the payload, plus a healthy safety margin. This is the sort of thing you might expect a fairly competent Type 1 civilisation to be able to seriously consider - but the expense would still be astronomical - no pun intended.

21:30 some bactérias use sulfor instead of oxygen. Other s use iron to produces energy

FYI: Roy Kerr does not accept that Black Holes evaporate. I learned this during a Q&A with him after a Royal Society presentation.

Dark Forest Hypothesis regarding alien life ;)

Hi Fraser, you talked about the large telescopes being built like the ELT and the GMT and it struck me that I don't have a timeline feed of milestones around the development of these. Who is building them? Who are the associated companies and industries? What is the current step of development? Is this info out there and I'm unaware of it or is there simply not the appetite for constant updates such as you'd see around SpaceX development?

We don't know the layout of the Starship HLS interior, but isn't the pressurized, livable space in the same spot where the header tank currently sits? Can they move it to another part of the ship?

Aeturen Another interesting program.

Hi Fraser In relation to that first question, are you familiar with Sterling Engines? They are powered by a heat differential. As long as one end is hot and the other is cold, those things will keep on turning. Would they be a good power source for a moon base? I mean, if you have a base, where people are living, you're going to need to keep it heated/ cooled. So there should be about a 200 degree kelvin temperature difference between the inside and outside of the base and this should be a permanent state of affairs (unless you don't like your astronauts). But as long as your heating/ cooling the inside of the base ANYWAY, then wouldn't it make sense to use a Sterling Engine to use that differential to generate power? I think you might have mentioned something many years ago now, about NASA looking into potential uses for Sterling Engines on the ISS. Do you know if they ever did? Cheers, mate.

Janus. The Moon being secretly black seems like such a basic, obvious fact I should have known, but I've somehow gone 35 years as a very casual astronomy nerd without knowing that, actually. Very weird. Totally logical, but mildly mind-blowing all the same.

39:46 like Pandora from the James Cameron Movies for Avatar

I think there's more to the question about mini Hubble telescopes. With the constellation of Starlink satellites interfering with research already and other companies following their steps with their own constellations, time for on earth observatories is coming to an end. And when it comes to the money and resources, space telescopes could be built instead of those on earth. As you said, there's plenty of telescopes, so the parties which funded the telescopes could spend the same money on space telescopes instead.

What are some of the possible fixes do we have to address Lunar dust basically destroying everything it gets into?

Question: Are there any plans for an electromagnetic acceleration system in space? Would make more sense than starshot in my mind. You can add rings and make the probe accelerate meters or thousands of km just by adding rings in your system, you can make them smaller or bigger etc. Is there a limit in terms of speed for such a system?

Thermal heat storage would be very in efficient and take up volumes of space. Seems a bit archaic to me. We need something efficient, like fusion.

If your assumption about moon's gravel ture then moon's temperature must be balanced and not plummet to subzero temperatures in the luner night?

Question. Could a rocket engine be built with a vacuum sized nozzle but filled with something (heat tiles or similar) so that it starts as a sea level engine that insides slowly burn away qs it rises and becomes a vacuum engime, or woud it be the same a an areo spile engine and not worth the effort?

Great video 😊 #SaveChandra

Can we have a dive into the heat storage technology? I don't understand how the120 degrees Centigrade temperatre of the Lunar day can be stored in such a way that the regolith gets hot enough to melt, that seems counter to the laws of thermodynamics.

Temperature on the Moon is like clockwork; Seems like a heating element of the right size, driven to the right depth of the natural ground should be able to maintain a constant temperature in a properly insulated habitat built over it with no special equipment

Very interesting to hear you explain the Unruh effect 👀 So, would that mean that everything with mass creates Unruh radiation around it? Would an immortal being ultimately evaporate just like a black hole?

Cheleb 33:09 Earth’s apparent diameter (2˚) is four times that of the Moon’s and as the moon is tidally locked I’d assume an eclipse would last for a couple of days(?) at the point of the eclipse. I’d love if you would expand your answer to this.

Would a concept of an igloo work for a habit on the moon? The regulith could be formed into an igloo with the walls being thick enough to store and heat the interior? The walls could be thick enough to provide heat even during shade times as well as provide protection from radiation.

40:00 Júpiter can get mass from the red sun, and transforms to a brown Júpiter Star?

I'm not sure what kind of spaceship Tuesday Statzer had in mind when asking the question. I guess the spaceship in fiction that is closest to our current level of technology is something like the Hermes spacecraft from The Martian. I don't think it has any technology that we do not have currently at least in experimental phase so the only challenge is the actual manufacturing and the cost. On the other hand, without a ship of at least comparable level I don't think we should even attempt a manned Mars mission.

Photons seem to be everywhere in space. Even when JWST or Hubble look at a patch of sky that looks empty they still find a myriad of galaxies whose photons are picked up by the Telescope. Since the photons have energy, albeit a teeny-tiny amount, could those photons be used as an energy source by a spacecraft while traveling through interstellar space?

Fraser, possible Fermi Paradox / SciFi story idea (original, but unlikely to be the first time it's been floated), what if life always finds a way to balance itself out to keep ecosystems functioning, and humans are the first to suffer a mutation that makes them wildly successful and move out of the food chain and dominate a planet. A particular cosmic ray hit the foetus of mitochondrial eve (or some earlier equivalent) and turned us into exploration/domination/exploitation machines the like of which is not yet seen in the visible universe. Also, I am tired and need coffee. Love your work. 😅

Question: How much usabel ice is expected to be found in the moons shadowed craters? How long could it possibly last when used for propellant production? I guess It needs to be done in order to expand into the solar system. I just find it funny how it's called "sustainable" when they talk about ISRU, yet all propellant will inevitably be thrown out into space until its all used up. Lets hope we'll have set up propellant farms elsewhere by then, right?

Greetings from the BIG SKY

08:41 The Sun spots aren't actually black, only _relatively_ dim _in comparison to_ the rest of Sun's photoshere which would blind you unless you dim it down so much that the Sun spots _appear_ black.

I believe what [Cait] was trying to ask was, why can't we just slap enough shielding on a spacecraft that the radiation load is comparable to flying in an airliner?

Cheleb. I want to see that someday!

I've seen the proposed design for the next iteration of the Mars helicopter. Its much bigger than Ingenuity. Wouldn't it be better to have a fleet of small helicopters, instead?

16:21 - Quick correction: unruh radiation has not been observed, or at least not unambiguously.

How far do we need to put a telescope to use the sun as a solar lens?

Andoria

Finding another source of independently evolved life in our own solar system would subscribe me to the Dark Forest theory so fast...

Nimbus. Fraser thanks for all the hard work put in by the team and yourself.

Do we know how long the transition from hydrogen burning to helium burning takes for a sun like star? Like if a nearby star switched to helium tomorrow would we be able to watch it expand into a red giant, or would it be longer than a human lifetime?

Here's a question: Are there any plans to put a radio telescope in space? Would this provide any major advantage over ground-based radio observatories?

You mentioned you’d wanna go to the moon to experience a Lunar Eclipse…..but no realistically you wouldn’t, because temperatures on the moon in the dark can drop low enough to cause frostbite or death “Allegedly,” now with that said if you could get a sufficiently safe way to heat a space suit for that temperature you could maybe make the trip. It’s not a 2 weeks of night thing, but still takes a few minutes longer than you’d wanna be in those cold temperatures.

Question: instead of de-orbiting the ISS, could it be sent to orbit the moon and used as an emergency habitat for future moon missions?

Vulcan

I think dismissing Tuesday Statzer's question as "science fiction", on a par with fantasy about dragons and elves is unfair. A "space station in Earth orbit which is humungous and has radiation [shielding]" is a fair description of a O'Neil Cylinder. Which is something that can be built. In time, as our technology and space infrastructure matures. And much smaller versions, just with the aim of providing radiation shielding for astronauts will be that much easier to produce. As for the admittedly vague "... sorta like travelling" that speaks to me of an Aldrin Cycler. One of the smaller versions mentioned above, put in an orbit that intersects both Earth and Mars. Again something that is viable science, not requiring any magic or imaginary technology. Buzz Aldrin originally proposed it and it has been confirmed as viable. So why can't we? We can. In due course. Given sufficient funding, willpower, infrastructure and technological development.

Andoria some of the more energy intensive activities on a moon colony are going to be thermal in nature. Smelting, metal forging, keeping humans and equipment warm during 14 day long lunar nights.

I probably have about 30 years left at the most so i really want a mission to the ice moons that samples to see if there are microbes on those moons. so if the mission doesn’t launch in the next 10 years the logistics are not going to work out. so aeturon also.

Andorra - Made me wonder why space suits didn't melt if the temps are so hot in the sunlight

Hey Fraser, which is worse for a rover, the heat of Venus or the cold of Mars. Is the dust on Venus as bad as the dust on Mars for a rover? Thanks, Jason

Aeturen

The problem with Einsteins equivalency is time. At 1g acceleration an object would reach the speed of light in about 1 year, as objects cannot travel faster than light, if you are experiencing acceleration after one year you are in a gravitational field.

Andoria. Also, let’s say earth microbes hitch a ride on our landers and actually survive and propagate on another plantet or moon. How exactly will they effect it? Could bacteria change the atmosphere (or make an atmosphere) on one of these worlds?

26:33 - I think a better answer to the Grey Moon question is this: "Even very dark surfaces reflect some light, and a smooth surface reflects more than a jagged one. Sunlight is white (6500k) in colour, and when it reflects from a very dark surface, you see that white light. The sun's white light, reflected from the moon, looks mostly-white because there is so much of it, and it is reflecting from a colourless surface. If you look at a deep black piano, it looks black, but when a spotlight is pointed at it such that the spotlight is visible on the black surface, it looks white, and very bright. That is the exact same effect you are seeing when you see the sun reflected from the moon. It also helps to remember that the moon has no light of its own, and so it can only reflect light."

Nimbus The escape from venus to orbit is extremely hard. The gravity is nearly the same as earth. The rotation is extremely slow (little or no velocity boost). A floating launch pad may not be high enough to see even 1 bar. It could be 5x or 10x (guessing here) for all we know. It's like lauching from underwater. The wind would be crazy even with "light" breezes. I think you over estimated our abilities.

Fraser. From another Frazer, thank you for your work. (same sept). Despite your excitement and great presentaion; would you consider doing more but shorter videos? I literally cannot do 41 or more minutes at a time. Just a thought from an old enquirer.

The ISS is in fact a large spacecraft assembled in orbit, just not a spacecraft that can travel to other planets.

Vendikar. 🤯

Blackholes have to eventually shrink, imagine the temperature surrounding them is close to zero k, obviously there's equalisation constantly happening,

When Webb or whatever telescope is looking "back in time", say at some of the earliest galaxies, are they looking in a specific direction? Wouldn't that make sense if the universe came from one point (big bang)? I can't wrap my head around the 3D layout of the universe and time...

Even if it was possible to get a rock sample from Venus would it be worth it? From what I understand Venus is very similar to Earth's chemical, so what new information could we gain?

28:35 Your AnthroFuturism guy cites a study that estimates a kg into low earth orbit will cost $100, not $5000. To the moon he estimates $500, not "a few million dollars".

Thanks for another great show. In due respect: you say that the issue with human spaceflight is radiation. Astronauts say it's toilets. :)

Q - If air density on Venus is estimated at around 50x that of Earth, does that alone negate the opportunity for a return to Earth from the surface due to an insane max Q?

Don’t know about feasibility, but couldn’t we run a pipe from always-dark craters to lunar day lit areas? I think it’s called a Stirling engine, invented in 19th century.

Q: At a few moments after the big bang, once the fundamental forces split, and gravity became a thing, why wasn't everything pulled back into something like a black hole? Did the expansion of spacetime simply overcome the total effects of gravity that existed as matter started to form?

Hey Fraser, why aren’t there cameras on the moon pointed at the Earth? Wouldn’t there be some scientific value for watching the weather, auroras, or anything else from lunar orbit?