Combining All Telescopes On Earth, Cooling Down Venus, Replacing ISS Modules | Q&A 211

Why don't we just combine all telescopes into a single one that will have a crazy resolution? Can we simply replace old ISS modules with new ones? How long will it take to cool down Venus? How much mass can the Earth afford to lose? Why blue shift exists if the Universe is expanding? All this and more in this week's Q&A
00:00 Start
01:04 [Tatooine] How much mass can the Earth lose?
04:23 [Coruscant] Can a Dyson sphere be stable?
08:36 [Hoth] How long till we cool Venus down?
14:34 [Naboo] How many atoms are there in the Universe?
15:46 [Kamino] Can you combine all Earth telescopes into one?
22:47 [Bespin] Will we ever see self-replicating probes?
25:51 [Mustafar] Wen LUVOIR?
28:22 [Alderaan] Can we save Hubble?
30:09 [Dagobah] Why blue shift exists if the Universe is expanding?
32:16 [Yavin] Why not just replace old modules of the ISS?
Terraformed Venus image in the thumbnail, Credit: Ittiz
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[@spidalack]

How to build a magneto-sphere for venus? Well, you have this HUGE solar colector you put up in front of the planet already. It's already in a good spot to collect a lot of power and generate a large magnetic shield in front of the planet, protecting it from the sun.

[@bravo_01]

BESPIN, reminds me of the replicators in Stargate and that tomorrow’s my 30th birthday :)

[@JohnnyWednesday]

We're all replicators who erased our knowledge of being replicators to avoid an existential crisis. Happy birthday :D

[@bravo_01]

@@JohnnyWednesdayThank you :D

[@undertow2142]

If you have a bunch of frozen co2 on Venus then you should build a few a million mass driver / spin launch deals and shoot it all to mars. Then you’d have to put magnetospheres around Mars and Venus but they’d be rapidly becoming livable.

[@kittywampusdrums4963]

he Venusian sun-shade would get pushed out of it's L1 point by the solar wind though probably wouldn't it?

[@HereComesThaBoom]

I was just casualy catching up to the videos. And then i suddenly hear my name 😁 awesome way to start my sunday off. Thanks Fraser!

[@jonathanbrewer3051]

I genuinely appreciate all of your videos. I watch them with my almost 6 year old son regularly. He is intrigued by them, and everything that raises a billion more questions that I try to answer... lol Much love and respect.

[@MaryAnnNytowl]

#ParentingDoneRight Great job, Dad!

[@JohnnyWednesday]

Thank you very much for taking the time to do Q&A!

[@c.i.demann3069]

Q: what's going on with those old Soviet probes on Venus? Have they been crushed by the pressure, melted by the heat, eroded by the acid rain, or none of the above?

[@darknebulae7470]

Did you just watch megaprojects or something? I did about an hour ago, and asked myself the same question. Crushed I'm pretty sure. Prolly melted too by this point.

[@undertow2142]

Any sealed compartments have definitely been unsealed so that’s the extent of it being crushed. But melted and oxidized by the environment? Absolutely and very much.

[@JohnDlugosz]

Eaten by Venarian mud worms. According to classic Heinlein stories, anyway.

[@HarryPalmerOrchestra]

They are now leading the Revolution, Comrade.

[@HarryPalmerOrchestra]

I'm glad we're thinking about cooling down Venus.

[@jimmann8083]

Hoth Q: Since the universe is expanding, what (do you suppose) it is expanding into? A perfect vacuum? Q: How could you not love your podcasts?

[@MaryAnnNytowl]

I vote Alderaan: this is what I've been hoping will happen, some company will save Hubble! If NOTHING else, it needs to be saved as a museum! Let it be a museum in orbit, for people to go visit as part of space tourism! Edited to add: About Hoth, the things (articles, published papers, etc) I'd read about for Venus also included seeding it first with some kind of algae or other plant life that could float in that upper atmosphere and turn that CO2 into O2 and more of themselves. Is that no longer a workable help for the job? Great video, as always, Fraser! ❤️❤️

[@Tyler-sy7jo]

Yavin. Being able to bring Hubble down safely to be repaired would be incredible. If I remember correctly, it still has that faulty (though long since corrected with "telescope glasses") lens and its down to two reaction wheels? I remember there was also that problem where the telescope had to be rebooted through its backup computer. There's probably many other problems with it that are being compensated for groundside by some very ingenious engineers, but it'd be really convenient if they could just pluck Hubble from the sky, fix it up, and send it back up there.

[@TheyCallMeNewb]

Yavin! We would service humanity of all generations to come by saving the ISS for posterity.

[@ravensrulzaviation]

Great video Fraser. Thank you.

[@pallasiteroid]

8:36 - Why terraform Venus if there might be regular cataclysmic global crust overturns due to lack of plate tectonics? - Why block precious solar energy when you need S-LOADS of energy to terraform Venus, or modify it in more reasonable ways? - Why wait for things to cool down and form an obnoxiously obstructing dry ice crust before binding up the atmospheric carbon? - As a rocky planet similar to Earth there should be more than enough elements to bind all the carbon which dwarfs in abundance relative to silicates, aluminates, iron, and even magnesium and calcium. Some of that present in reduced state. Perhaps even deep metallic iron and nickel becomes reachable eventually (veeery speculative though). From CO2 and SiO2 make structurally useful silicon carbide (which is self quenching when burning forming a glass skin) and with excess oxygen oxidize whatever is not yet oxidized. There should be plenty. Also a bit on the side: - What about the local magnetic shielding induced by the solar wind hitting the atmosphere directly? No one seems to talk about that anymore.

[@aetoski8724]

You make some of the best vidoes I've ever seen. Such a great ability to explain difficult topics for anyone to understand. Truly love your work.

[@deems7584]

I like the question about 3d printing in space. Great show!

[@davidhanna8470]

Let's put Hubble on the dark side of the moon! Yeah, Cheerleader that one .Mr. Fraser Cain!!! Hubble on the moon t-shirts should be made available soon.

[@bassangler73]

Always look forward to this show!!!!

[@FalloutConspiracy]

Love these Q&A's!

[@efanjul5768]

With regard to the sum-of-all-telescopes idea, a more doable project would be perhaps to robotically 3D print a gigantic Arecibo-style dish in a Moon crater.

[@metaqllica1]

Yavin: I would love to see the ISS saved! Maybe even made into a space museum one day. To show the early days of space flight. But again like you said it all come down to cost.

[@frasercain]

Yep, we either save the ISS or build the lunar gateway.

[@tr1hollywood]

Venus. Adding more material to Venus would be a massive undertaking. Wouldn't it be far easier to turn the carbon to dry ice and use a rail gun to shoot it away from Venus?

[@brainbark]

Yavin...yay to another great Q&A episode.

[@thesunexpress]

Year to year, the Earth actually gains more mass on average than what it loses either naturally or by human interference. We get 'hit' by tens of thousands of tons of interplanetary dust/debris/gas every year, offsetting whatever amount of lighter atmospheric gasses we lose and/or rockets & satellites sent into space.

[@TheExplodingGerbil]

Mustafar and tysm! Great question about Luvoir x Shame it won't be made.

[@MrTmm97]

14:34 video games… on computers. Calling it now. Maybe digital immortality?

[@Ittiz]

I see you used my terraformed Venus image. If you need any of my images I have them with an alpha transparent atmosphere that can be overlaid on anything.

[@michaelallen2971]

So he used your image without permission?

[@HarryPalmerOrchestra]

@@michaelallen2971 🍿🍿🍿🍿🍿

[@Ittiz]

@@michaelallen2971 He did, but I released the version he used under CC BY-SA 3.0 on Wikipedia. He's free to use it as long as he credits me. Which I didn't see, but that's not highly important for thumbnail.

[@isaackitone]

I apologize on his behalf.

[@blogsfred3187]

It is credited in …more txt

[@avejst]

Kamino, Great question Great show 😀

[@isaacplaysbass8568]

Fraser Cain makes my life a richer experience than it otherwise would be, because he and his team/friends keep my space obsessed inner child's imagination and thirst for knowledge alive. THANK YOU all.

[@scottbringloe6408]

Love the podcast, keep sending out the great info. I was reading about direct collapse black holes (DCBH) and I was hoping you could give an overview of the theory. Also now that the JWST has been launched and in service it is my understanding that it would peer out at these distant quasars and shed some light on these very large black holes and how they actually formed in such a short timeframe. Where are we on that issue? Thanks again. Scott Bringloe Halifax, NS

[@adirmugrabi]

Tatooine, even if every atom, will "lose all of it's extra mass" meaning it be separated from any other, it will still be going at the same speed around the sun, so it will miss it exactly the same. That is how rings work

[@vikramkaura6335]

love your qa videos. i learn a lot. i wish you do more of these

[@dropshot1967]

About refurbishing the ISS with Starship. I think It would only be a relatively minor extra cost to build a new version of the ISS that could make use of Starship's extra large size and payload. That would give designers the ability to increase the functionality and habitability of the new ISS. I feel building a rotating station like the gateway foundation proposes would still be a step too far, although it might be possible with enough budget. That would need development of a lot of new technology though.

[@HylanderSB]

NGL, Hubble is working REALLY hard to stay operational these days. Another servicing mission would be a game changer. Note....I'm saying SERVICING MISSION. Simply reboosting HST would be a waste of time and money.

[@zephyr9673]

Kamino We should try it, using the international pulsar timing array to sync observation with Eart and space satelites. Build on the EHT get a Photo series of Eris and Proxima A B And C...

[@lsbmpharmltd]

Hi Fraser, is TON-618 still the largest known black hole in the universe? And will the event horizon telescope take a picture of it?

[@fanOmry]

For Venus... We have *use* for that CO2. Well, the C, Anyway. Hydrogen can be brought from the sun if we don't have Constant Fusion/Expance Rockets to bring it from Jupiter.

[@theadventuresofjerryandnori]

Hey Fraiser love your channel, especially the interviews! I was wondering when you think fusion propulsion will be realized?

[@frasercain]

Thanks! There are a bunch of interesting fusion rocket concepts in development. I'm not sure when they'll actually be used for missions, but I'd guess within a couple of decades.

[@ahaveland]

Kamino: Radio waves can be recorded and timed with great resolution, so that the wavefronts can be reconstructed. We can't do that with light at THz frequencies. I don't think simply adding mirror areas helps much with improving the diffraction limit, unless they are perfectly in phase. IIRC, like the double slit experiment, a photon is received at multiple telescopes simultaneously even if millions of miles apart, as long as they are the exact distance from the source. This allows interferometry to work and would be able to recreate awesome detail.

[@danl6191]

An episode of Startrek got me thinking. If we encounter intelligent life in the galaxy, how would we communicate time? Days, months, & years are Earth centric. Would it be a decay rate of an element?

[@tapewerm6716]

Oh dang! And I've been keeping my poor ferrets in a Faraday Cage. No wonder they're so crazy.

[@ocoro174]

finally. it's been too long without a Fraser video

[@_RedWizard]

{Hoth} good question

[@albert_vds]

The most promising thing about something like Starship and bringing back space station parts is that they can inspect what needs to be improve and what works.

[@frasercain]

Yeah, if they bring back pieces for upgrades and maintenance, that would be a game changer.

[@KGTiberius]

QUESTION: why not recycle some structural assets/parts of the ISS and move them to the lunar station? (e.g. trusses, robotic arms, etc. ) Install a ion thruster for delta v changes, and by de-orbiting components that are not suited to deeper space. Even if it takes a decade to raise the parts to lunar gateway orbit, it is better than wasting the mass already that far out of earths gravity well. Or am I missing something?

[@mariemeneses2117]

tbh, I was thinking the same thing, and I just feel like "Space Janitors" are those serious, joke careers you'll read on Bloomberg 10 years from now. But it makes too much sense to problem solve and recycle the space trash for something else. Nations and companies will pay billions for real-world solutions, especially some weird minecraft space probe.

[@andretokayuk8100]

Instead of burning it up, we should boost it up into much higher orbit and start a space junk yard.. I think recycling makes even more sense in space then on this prison planet..

[@alteans]

and the fantasy train is on the roll😁

[@JonahRoyes]

The same sun shades at the Venus Sun L1 point can be magnetic and block solar wind and a magnetic satellite arrays can block cosmic rays

[@YurLord]

A fleet of SpaceX Starship telescopes at the same Lagrange point as James Webb would be amazing.

[@augustwest9727]

Kamino You question was should we use a lot of telescopes to look at one thing or use them to look at many things. The answer is Yes. Sure it may not be the most practical thing to do to use them all at once in a coordinated manner, as opposed to looking at many things all at once. But it does sound...MORE FUN. Sometimes you do things just because it could be fun... Maybe you learn something along the way....like how to coordinate millions of telescopes and adjust for the atmosphere. I like to do stuff sometimes just because that would be Neat. Hoth: If we wanted to terraform Venus I have my own ideas of how to reignite the Magnetosphere, but other thing that we would need to build an artificial day structure to reflect light to the other side of the planet sense it is tidally bound. Yavin: Inflatable Modules have come a long long way, a Test not long ago, they tested them to failure, they withstood (if I remember correct) 3 times what they needed to. W could build a space station in one Launch if they are all inflatable.

[@vidabreve]

Love your channel, amazingly interesting stuff. Please point your camera correctly. Thanks!!!

[@Interstate66]

Alderaan :.:.: Follow-up-question: Because the HST is still that useful and there are so much subscriptions for it, so that it's maybe not possible to ever catch up... Why we not just build another 1 or 2 HubbleSpaceTelesopes to get more observations done and the need satifsfied? Just using the old build to get it done and up into space much faster than to plan a new one?

[@bbbenj]

I vote for Yavin. Thanks for the show.

[@airplayn]

Forget the sunshade and just drop powdered Calcium or Magnesium onto Venus and let the atmospheric heat catalyze the reaction of gaseous CO2 into mineral sequestration. Regarding the cost benefit of waiting until the future to finance a big project, I recommend you should check out the seminal book for 1974, "The Next Ten Thousand Years" with ISBN etc which I mentioned a few comments back.

[@williambaikie5739]

Terraform Venus with lighter than surrounding air greenhouses. Place at 1 Bar atmospheric pressure, which is also low enough temperature to support life. Fill with CH₄ which is lighter than CO₂ for buoyancy. Transparent dome protects from UV and other harmful radiation. Microbes can convert either or both CO₂ and CH₄ into O₂ and H₂O. Human colonies are connected to utilize water and oxygen produced. Eons later, CO₂ is eventually much reduced and O₂ is high enough to support breathing. Perhaps sunshield/Photovoltaic microwave transmission helps reduce insolation. If greenhouses build for long durability, then Venus can be terraformed without human maintenance. Other idea, engineered microbe which fills air sac with CH₄ to float at 1 Bar, and has photosynthesis to convert CO₂ to O₂. Long term, alter Ceres's orbit until captured in Venus's gravity and become it's moon. Moon creates tectonic activity and magma. Perhaps enough to cause a magnetosphere.

[@JohnDlugosz]

First, "become *its* moon". Anyway, years ago I posted a question on the Worldbuilding Stack Exchange about moving Ceres to become a moon of Mars. So, same idea, just a longer distance move. There were posts going into detail about the amount of energy needed, various practical considerations, etc.

[@williambaikie5739]

@@JohnDlugosz After my post I immediately thought about moving Ceres to Mars. Of course either would be inconceivably high amount of energy. Something like a massive nuclear rocket and decades I'd imagine.

[@ThePhantomphan11]

Hoth for sure! Screw all this talk of living on Mars, I want to live on Venus. Cloud City baby!

[@doncarlodivargas5497]

When the Dyson sphere crash into the sun we simply do as in Hollywood movies, run fast and hide behind some cardboard boxes, anyhow, it must be really annoying to finish the colony on Mars just to be told Mars will be used to build a Dyson sphere

[@HylanderSB]

I missed the connection between plate tectonics and a magnetosphere on Venus. Isn't the magnetosphere generated at the core? Is it that plate tectonics are a necessary side effect of the required core conditions?

[@BennettBenson]

kamino. If space and time are one thing and space is expanding, does that mean time is also expanding? I love your show. Thank you.

[@frasercain]

It doesn't appear to be expanding, but different parts of the Universe have experienced different amounts of time from each other.

[@boboblio4002]

Yavin, Refurbishment or perhaps even picking up some large space debris sounds exciting.

[@CoreyKearney]

Fraser You thought experiment about combining telescopes got me thinking. About the idea on the books for a starshade, placed some distance out to block the light of the star and enable planets to shine though. My question is, with that kind of technology what's the point of having a structure for the telescope at all? Why not free float the sensors, the mirrors, the reflectors, all of it? Enabling huge mirror sizes and variable focal lengths Like a DLSR in space.

[@androidchannel309]

Here's a topic for an entire video: prove/disprove whether the 'classic' sci-fi posters with more than one moon or planet (large, visible discs) in the sky behind the hero are mathematically possible, given basic orbital dynamics. In other words, if Earth had a second moon, would it be mathematically possible for it to ever be close enough to our original moon such that any amount of zooming with a Nikon/Canon result in anything other than a very large moon with a tiny point-of-light second moon next to it?

[@Garian9]

"Stop trying to make Venus happen. It's never going to happen!" - Mean Girls. Seriously, the moon, Mars, and gas giant moons are much easier to do anything with.

[@peceed]

What we need is multiple copies of telescopes. Most of the cost are R&D, a few next copies should be much cheaper.

[@VunterSlaush1650]

Yavin. It actually made me wonder, could one of our far future milestones be fabricating, launching and docking a module to Gateway built wholly from materials mined and processed on the moon?

[@reddragon7030]

I’d like to challenge your sphere idea All of your mass can be collected from solar emotion in the form is alpha, beta, and gamma emission, and reordered into raw material via fission and fusion. So all you would need is a few satellites labs orbiting the sun(or stars), to produce more satellites, and through exponential growth, you can make your “sphere” Cheers

[@NormReitzel]

Blue shift: Well explained. ☝☝

[@frasercain]

Thanks!

[@Starman_67]

Cheers

[@tonywells6990]

There's about 100 galaxies with a blueshift, but maybe only a dozen or so large galaxies. The local group (about 40 galaxies within 5 million ly mostly comprising of dwarf galaxies that orbit ours and Andromeda, although some have a redshift), of which we are a member, and some galaxies in the close-by Virgo cluster (about 50 million light years away) that are moving towards us as they fall towards the centre of the cluster from a more distant location, as well as a few more in other regions within a few tens of millions of ly.

[@kneelandub]

Hi Fraser, I really enjoy your show, your piece on Venus interested me, could you terraform Venus with very tough microbes that consume CO2 and live in the temperate upper atmosphere, on balloon islands?

[@Tyler-sy7jo]

Theoretical question. If you had a ship that could somehow go faster than light and trained an unimaginably powerful telescope on Earth and took observations as you went, would you see Earth going back in time? If you made it to 4.5 billion lyrs away (somehow in the span of a human lifetime) would you be looking at the early solar nebula? That'd be wild, if true (as impossible as it'd be to do).

[@pbourd]

In “The First Immortal” (Del Rey Books) The First Immortal (1998) is a novel by James L. Halperin proposed the advent of nanobot assemblers, and disassemblers, that could translate repetitive molecular shapes to be replicated by the assembler bots. Assuming that we (earthlings) will ultimately develop this technology; what elements should first be targeted? Microchip device replication-repair, or regolith conversion for moon/mars habitation terraforming? Peter Bourdelle, Allentown PA

[@DarkJK]

I think there was a episode on Kurzgesagt that explained the terraforming Venus thing. Perhaps they used the numbers on how long it would take.

[@alligatorscrublord]

I think the better idea with a dyson sphere is to instead to have rings just a few thousand miles wide, thin enough that the difference in gravity and curvature won't matter at the edges. No sphere means no poles means no loss of gravity and less structural stability required.

[@JWMCMLXXX]

Holy hell Id never seen that image of Pluto before. Thats intense.

[@Drakcap]

If you're talking about 17:26, that's not an actual image. It's an artist's depiction of what they thought Pluto might look like before the New Horizons probe flew past.

[@kkgt6591]

Hi Fraser, what are other major areas of research being carried out in astrophysics which are usually not in news. News mostly covers things related to blackholes, expansion of universe etc.

[@alfonsopayra]

Given that things in life follow a cycle, I think that intelligent civilizations that are older than ours must have gone through the same problems and solutions as we have. With this in mind, don't you think that there may be a civilization that is currently solving the problem of global warming? Could it be that they are using something similar to the idea of shading Venus from the Lagrange point L1, which would give us a clue of what to look for if we manage to have a telescope powerful enough to detect not only small rocky planets, but also artificial objects at points of balance between the forces of planets? Could it be possible to use artificial intelligence to analyze Lagrange point locations in databases of observed planetary systems to search for an apparatus or mechanism like the one mentioned above? Is there a clever way to locate objects at points of balance in planetary systems? Just as we cannot see electrons but we can prove their existence, could there be something that tells us "there is something in balance at this Lagrange point that is not natural"? Wouldn't that be great?

[@creamydeath2160]

( Question ) I've seen a lot of videos about a subject called "The Great Attractor". In these videos they explain there is something pulling everything in the universe to it. So my question is, how can everything in the universe be pulled toward some object, while I've seen videos about how mostly everything in the universe is moving away from us? Thank you very much for your time and another great video!

[@smeeself]

Short, non professional answer. The Great Attractor isn't attracting everything in the universe, just in the local supercluster.

[@creamydeath2160]

@@smeeself Oh, I see!. Thank you for the reply!

[@davidmcdonnell2342]

Yavin. Yes, let's hope Starship will can save all that hardware.

[@markmelcon9484]

? The orbits of Phobos and Deimos are inclined one and two degrees to the equator of Mars. Do these orbits follow the equator as Mars itself tilts relative to Sol?

[@ccrose1]

I wish more people would just get to the point ❤

[@kx4532]

Spin that venus

[@WayneMetcalf]

You should check out Astrobiscuit's Big Amateur Telescope. It is possible to combine many amateur telescopes.

[@ericbutler6990]

In the extreme distance of space time, does red shift get stretched into a strait line particle? Could we make a telescope that measures the energy of a particle perhaps in volts instead of the wave length to see further back into time?

[@PainKillerKev]

If voyager 1 and 2 went through a wall of fire before entering interstellar space. Do you think it would be possible for a second goldylocks zone to exhist near the wall of fire?

[@brothberg]

When will we send a telesccope to the focal point of the solar gravitational lense?

[@Threedog1963]

I've read online about amateur astro-photographers recording videos of their targets. Then, they run the video through software and the program deletes frames of videos where the atmosphere at those seconds was acting up. Then the software stacks the remaining frames into one clear image.

[@frasercain]

Yes, but that only works well for really bright objects which take up a large part of the sky. Planets, mostly. For fainter, smaller objects, you need to have the best possible seeing. Ideally out in space.

[@spacefan4ever]

Is it feasible or practical to build and station super, super sized reflective thin mirrow-like surfaces at Mar's L4 and L5 Lagrange points to re-direct sun light onto Mars to warm it up?

[@theOrionsarms]

The L4 or L5 points of the Mars - Sun system is at the same distance from Mars as the Sun(on average 225 million km), so would be almost impossible to keep a spot of solar light from that distances on a body the size of Mars using mirrors (limits of optical technology and non-coherent nature of solar light don't allow that).

[@billrumbley]

Coruscant gets my vote.

[@i-love-space390]

Starship will be a game-changer if SpaceX can make it work and fly it as often and as cheaply as they are planning. That's a lot of "ifs", but Elon the slave driver has a way of dominating and cajoling people to make things work that previously engineers thought was impossible. Falcon 9 boosters have flown many more times than people thought. I have no idea how much refurbishment is required or how fast it can be reflown, but it is still amazing. The ability to lift the huge payload of Starship to LEO at a nominal cost will indeed be a game changer. The capability will inspire new projects previously thought impractical, like solar power satellites and sustainable moonbases.

[@ArdaKaraduman]

I AM FINALLY IN THE BACKER MENTIONS ! YAAAAAAY ! Good attempt on pronouncing my surname Fraser, gave me a chuckle haha :) Also, for the occasion, I have a question. Though I am not sure if it is something you would be interested. Cause it is more Physics than Space I guess. We know black holes create time dilation effects for objects around them. Actually its not the black hole, every object with mass creates this, even earth, but it is more severe in the case for black holes, because they tend to be super massive. My question is, can this effect have something to do with Dark Energy ? AFAIK, we came up with the dark energy explanation because we observe some galaxies spinning faster than they should with the mass they include. Could it be time has a different speed in those galaxies ? Little bit crazy but it is something that has been nugging me for a while.

[@frasercain]

Thanks, I tried. :-) The time dilation will come from being close to a gravity well, but it'll only be severe once you're directly close to a black hole. The time dilation from a galaxy cluster won't be anything like that. I've actually got an interview on Monday with new research about how black holes could explain dark energy, so that might help fill in some holes for you.

[@serg3y]

Hello Fraser, Question: When galaxies collide most of their masses merges into a new larger galaxy. This implies there is some friction to slow down the individual masses. Yet we expect few if any actual collisions of stars. Which implies interactions will be gravitational and thus elastic (no friction). If interactions are elastic i expect the stars to maintain their initial velocity and come out the other side with the same velocity. Thus the galaxies would pass through each other without merging, maybe just get messed up... What am i missing? Is it because most of the mass is not in the stars and it does indeed 'collide'? Are the collisions direct or long range magnetic field interactions? where does the initial kinetic energy go and is there enough to measure a change.. eg will the new galaxy 'heat up' in some significant way?

[@amallee3361]

Yavin. Yes, while the ISS, at $100 billion, may be the single most expensive "machine" that we've built, that was done over decades. Contrast that with the US DOD: they lose $2100 billion like one would lose change behind sofa cushions. "Uhhh... I dunno?" 🤷‍♂️ So, it's not a question of money. It's a question of priorities, of political will. Ultimately it's a question of vision. As John F Kennedy said: "Things don't happen. They are made to happen."

[@Henrik.Yngvesson]

3:00 It's not about mass but speed, so when we gravity assist and slingshot around planets we rob them of tiny amounts of speed which would change their orbit.

[@frasercain]

Yeah, when you do gravitational slingshots, you lower their orbits by a tiny little bit.

[@larscarter7406]

Venus? Throw a few comets at it, that should cool it down. Lol.

[@shabbysnubtide3339]

Could you use the comet impacts to spin up the Venus rotation rate if you aim them right?

[@JohnDlugosz]

You would melt the surface from repeated impacts, but the effect on spin would be insignificant.

[@stevenewtube]

Now there’s a phrase; “ the accelerating effect of dark energy”. I’m sure you’ve covered it. Love your work.

[@qarljohnson4971]

Hoth If humans continued to increase their energy consumption exponentially, to the point of building dyson sphere(s?), we'd probably be building and sending out thousands or millions of interstellar crafts.

[@marcusaurelius8453]

How far in the future before a giant space interferometer could conceivably be built using Earth Moon L3, L4 & L5 to extend the Event Horizon Telescopes resolution for radio observations? What are the theoretical limitations of using the same arrangement for observing shorter wavelengths, might optical frequencies ever be possible for such a large system? How about using this arrangement for gravitational wave observations like a Giga LIGO? If any of these worked out, how about scaling the system up to using the Earth Sun L3, L4 & L5 to get an effective resolution of 2 AU? Beyond that how about using Jupiters orbit? Is there a theoretical limitation on how far such an arrangement could be pushed? Thank you for putting out such awesome content!

[@bozoerectus3207]

You've spoken before about the universe's heat death, when the only things left will be certain exotic objects that can last for a trillion years. My question is, what will Time be like in that end-state period? Will it progress at the same rate it does now, or be very different? Will Time eventually begin slowly sputtering out, or just switch off like a light switch?