> As particles from the sun hit the atmosphere, they excite the atoms in the air. These excited atoms start to glow, creating brilliant displays of light called auroras.
The process is a bit more nuanced than that. The modern mainstream understanding is that the growing pressure of the solar wind makes the tail of the magnetosphere "contract" (sort of pushing it inwards from the sides), which leads to reconnection of magnetic field lines. Once the reconnection occurs, the magnetic field lines that remain bound to the geomagnetic dipole accelerate the particles on them towards the Earth => they slam into the atmosphere, exciting the atoms and generating the aurora.
This was incredible! Couldn't stop scrolling and reading. For a kid of a certain age and curiosity it'll blow their mind! I'm so grateful the creator made this, shame that his "buy me a coffee" isn't a simple PayPal or Apple Pay but you have to put in credit card or bank details!!
I missed that notice at where its says: Here be a near mars atmosphere in temperature, pressure (40 kms up) but not as hostile composition and with less radiation. Thats five Mt Everests high.
TIL it's estimated that over 48 tons of meteors hit the atmosphere every day.
Regarding actual space elevators though, while they're not sci-fi to the extent of something like FTL travel - ie. they're technically not physically impossible - they're still pretty firmly in the realm of sci-fi. We don't have anything close to a cable that could sustain its own weight, let alone that of whatever is being elevated. Plus, how do you stabilize the cable and lifter in the atmosphere?
A space elevator on the moon is much more feasible: less gravity, slow rotation, no atmosphere, less dangerous debris. But it's also much less useful.
While a space elevator doesn't contradict any fundamental limits of physics, that doesn't mean it's actually possible to build one. There is no reason to be certain that it's actually possible to create a material that has the required characteristics in terms of tensile strength to support it's own weight, plus the weight of the elevator, plus the weight of all the additional cabling. It also has to endure the huge temperature differences that it will experience along its length and from day to night and from season to season.
This is especially true considering that you don't need something that barely holds - you need something that you know will hold up to many times more weight than it needs to, so that it can be safe: the potential energy such a thing would store would be enough to dig into hundreds of meters of rock all around the world, if it ever crashed. So, you have to ensure there is no realistic chance of it ever crashing. It also has to be highly non-fragile in other ways, so that a madman with a bomb or a freak collision with an airplane or a meteor (especially likely in the thin upper layers of the atmosphere) won't bring it all down.
This combination of properties may well be completely impossible to actually achieve in a material. Even if there is no obvious basic law of physics that it would break, that doesn't mean that it wouldn't break other, harder to touch, derived laws.
Well if it's contingent to having massive amounts of unobtainium and subject to unsolvable engineering reality check conundrums then it's just as unlikely as an Alcubierre drive which "only" needs exotic matter that allows negative energy.
The problem with space elevator is not only the lack of material today, but also the fact that such elevator is an ultimate and very fragile weapons platform, you basically get stones up the well and then drop them on the enemy. Meaning that any authoritarian country would destroy it even before it is ever built. And sturdy enough space elevator after it's break at any high point would start falling down on the planes in a loop, eventually flattening everything in its path when higher portions reach supersonic speeds. So unfortunately there is low chance it will be built, unless we sort out stuff on the planet first.
And hypersonic weapons. If you can get one to fly at Mach 20 for at least 10 minutes, you could cover the entire surface of the planet with a dozen launchers.
The bigger problem I think is the elevator itself. Cutting it and letting it fall would be far more destructive than any weapon ever fired or even conceived.
Snipping off just the first few kilometers is not catastrophically destructive yet, and cutting it down further up would require multistage rocket designs, sophisticated steering/targeting and potentially significant yield (you'd need to cut unobtainium, after all...). If you can build a space elevator, you can defend against those.
You better thoroughly inspect what cargo you put on the elevator itself, of course.
> A space elevator on the moon is much more feasible: less gravity, slow rotation
The slow rotation is a minus, it means you've got to string the tether up to L1 instead of "just" up to geo/luna-stationary orbit. A lunar space elevator needs to be at least 56000 km long, more than 20000 km longer than the one to earth.
> But it's also much less useful.
Yeah, especially because all the things that make lunar space elevators a little more attainable also make lunar mass drivers a lot more attainable. Why ride in an elevator for a week if you also can just be fired from a cannon?
Space elevator was the perfect application for carbon nanotubes according my professor few decades ago. I wish humanity could unite for such project and enter space exploration phase. But I feel it will stay sci-fi forever.
Almost all discussions around space elevators focus on the cable itself, how to manufacture and deploy it, and completely forget about the issues that would arise afterwards:
1) How do you attach the climber to the cable without affecting its structural integrity? By squeezing it really hard? A material that's optimized for longitudinal tension strength is probably not very tolerant of lateral compression.
2) How do you provide power to the climber? A regular electric cable can't support its own weight, so either you have to attach it to the climbing cable, or you have to make it from the same material.
3) Is it even worth it? The climber needs to cover a distance of ~36,000 km, so even at 200 km/h it takes 7.5 days from the bottom to geosynchronous orbit. How many climbers and what payload can the cable support at the same time? Refer to issue #1 regarding limits in speed and mass per climber.
The throughput in tonnes/day is absolutely abysmal in relation to the immense upfront infrastructure cost per elevator. Compare this to SpaceX's Starship, which is getting closer and closer to fully reusable 100 tonnes to orbit in minutes. Space elevators will stay science fiction forever, not because they're infeasible, but because they're useless.
If anything, "evolution" filters out disadvantages (eg: can't survive because your neck's too short and that pesky giraffe is eating all the leaves you could reach).
Non-SI legacy units have been grandfathered in and 'accepted for common use', but ICAO recommends that SI units should be used[1] (eventually). China and quite the majority of the ex-USSR, for instance, use metre flight levels[2].
There have been at least two aviation accidents and incidents relating to unit mis-conversions. This is two too many. As an SI absolutist, everyone should switch to SI or units purely derived from SI (so domain-specific stuff like parsecs, electronvolts, and binary prefixes, if appropriately symbolled are OK). It is an internationally-recognised, and nearly universal standard that permeates every aspect of human lives.
Giant Space Bola is much more attractive. It is a 10000 km string with capsules at both ends. It rotates in sync with earth so that the speed at meeting point is the same. You just hop in and end up in space without much effort. Because it is freely floating you can move it around to avoid meteor impacts and other such shit.
Wow, I'm really surprised to see some birds flying that high. Question: How the heck are they able to live normally at such extremely low temperatures?
It is appreciated that you can change the temperature unit by clicking on it, and how surprisingly cold and changeable the temperature is as you travel up through the atomic sphere (down to -84C, -119F).
Its development is really interesting, in that it was more a proof of a scientific paper to start with. Anyway one of their tweets from September 2024 indicates they're working on a sequel, despite their publisher (Annapurna, owned by Megan Ellison, daughter of Larry Ellison) having had some issues around then.
I loved the visuals but space elevators are far more science-fantasy than hard science-fiction. We should move on to sci-fi tech that has more realistic applications.
Only for Earth. We already have materials that can do it on the Moon (Zylon, for example), though not with great tether-to-payload ratios (200:1 or more), and Mars isn't too huge of a stretch (huge like the mass of the tether, which would be in the thousands to one tether-to-payload ratio. Shipping 50,000 tons of Zylon to Mars is a different beast)
What's really interesting is that a space elevator goes to Geostationary orbit by necessity. Getting to 100km vertically doesn't save as much as you might think when it comes to getting into orbit.
To get into a very low earth orbit from an equatorial launch pad at sea level you need about 9.2km/s of Delta-V
To get there from a 100km tall tower, you need about 8km/s of delta-V - about 85%.
Think about how much scrolling there was to get to 100km.
To get to the ISS you'd need to scroll 4 times further. Starlink and Hubble are another 100km beyond that.
You start having radiation problems if you spend too much time above 600km.
Aside from Apollo, the highest a human has been is about 1400km - 14 times more scrolling than this page.
To get to GEO would require scrolling over 25 times further than even that.
I think the idea behind this was less to showcase an actual space elevator and more to showcase what's going on at different altitudes. And above the Kármán line it would have become pretty boring, especially if you want to go up to GEO and beyond where the counterweight of a space elevator would be located - the Kármán line is at only 0.28% of the way to GEO. Using a logarithmic scale would have maybe helped, but not sure...
I just looked at it in the dev console in a chrome based browser and I think it is already pretty optimized. It runs very smooth on my device (Thinkpad T480).
Amazing work! One minor correction:
> As particles from the sun hit the atmosphere, they excite the atoms in the air. These excited atoms start to glow, creating brilliant displays of light called auroras.
The process is a bit more nuanced than that. The modern mainstream understanding is that the growing pressure of the solar wind makes the tail of the magnetosphere "contract" (sort of pushing it inwards from the sides), which leads to reconnection of magnetic field lines. Once the reconnection occurs, the magnetic field lines that remain bound to the geomagnetic dipole accelerate the particles on them towards the Earth => they slam into the atmosphere, exciting the atoms and generating the aurora.
This was incredible! Couldn't stop scrolling and reading. For a kid of a certain age and curiosity it'll blow their mind! I'm so grateful the creator made this, shame that his "buy me a coffee" isn't a simple PayPal or Apple Pay but you have to put in credit card or bank details!!
The other direction:
https://neal.fun/deep-sea/
And "up", but shown sideways, and on a different scale: https://joshworth.com/dev/pixelspace/pixelspace_solarsystem.... "If the Moon were only 1 pixel"
Neal also made one:
https://neal.fun/size-of-space/
I missed that notice at where its says: Here be a near mars atmosphere in temperature, pressure (40 kms up) but not as hostile composition and with less radiation. Thats five Mt Everests high.
TIL it's estimated that over 48 tons of meteors hit the atmosphere every day.
Regarding actual space elevators though, while they're not sci-fi to the extent of something like FTL travel - ie. they're technically not physically impossible - they're still pretty firmly in the realm of sci-fi. We don't have anything close to a cable that could sustain its own weight, let alone that of whatever is being elevated. Plus, how do you stabilize the cable and lifter in the atmosphere?
A space elevator on the moon is much more feasible: less gravity, slow rotation, no atmosphere, less dangerous debris. But it's also much less useful.
While a space elevator doesn't contradict any fundamental limits of physics, that doesn't mean it's actually possible to build one. There is no reason to be certain that it's actually possible to create a material that has the required characteristics in terms of tensile strength to support it's own weight, plus the weight of the elevator, plus the weight of all the additional cabling. It also has to endure the huge temperature differences that it will experience along its length and from day to night and from season to season.
This is especially true considering that you don't need something that barely holds - you need something that you know will hold up to many times more weight than it needs to, so that it can be safe: the potential energy such a thing would store would be enough to dig into hundreds of meters of rock all around the world, if it ever crashed. So, you have to ensure there is no realistic chance of it ever crashing. It also has to be highly non-fragile in other ways, so that a madman with a bomb or a freak collision with an airplane or a meteor (especially likely in the thin upper layers of the atmosphere) won't bring it all down.
This combination of properties may well be completely impossible to actually achieve in a material. Even if there is no obvious basic law of physics that it would break, that doesn't mean that it wouldn't break other, harder to touch, derived laws.
A terrorist attack on a space elevator happens to figure in the first episode of the TV series Foundation.
https://foundation.fandom.com/wiki/Bombing_of_the_Star_Bridg...
It’s about as devastating as you would expect.
Well if it's contingent to having massive amounts of unobtainium and subject to unsolvable engineering reality check conundrums then it's just as unlikely as an Alcubierre drive which "only" needs exotic matter that allows negative energy.
The problem with space elevator is not only the lack of material today, but also the fact that such elevator is an ultimate and very fragile weapons platform, you basically get stones up the well and then drop them on the enemy. Meaning that any authoritarian country would destroy it even before it is ever built. And sturdy enough space elevator after it's break at any high point would start falling down on the planes in a loop, eventually flattening everything in its path when higher portions reach supersonic speeds. So unfortunately there is low chance it will be built, unless we sort out stuff on the planet first.
I don't see it. Why worry about a weaponized space elevator when stealth bombers, cruise missiles and ICBMs exist?
If the power building the space elevator wants to bomb you, you're going to get bombed.
And hypersonic weapons. If you can get one to fly at Mach 20 for at least 10 minutes, you could cover the entire surface of the planet with a dozen launchers.
The bigger problem I think is the elevator itself. Cutting it and letting it fall would be far more destructive than any weapon ever fired or even conceived.
Probably no easy task.
Snipping off just the first few kilometers is not catastrophically destructive yet, and cutting it down further up would require multistage rocket designs, sophisticated steering/targeting and potentially significant yield (you'd need to cut unobtainium, after all...). If you can build a space elevator, you can defend against those.
You better thoroughly inspect what cargo you put on the elevator itself, of course.
> A space elevator on the moon is much more feasible: less gravity, slow rotation
The slow rotation is a minus, it means you've got to string the tether up to L1 instead of "just" up to geo/luna-stationary orbit. A lunar space elevator needs to be at least 56000 km long, more than 20000 km longer than the one to earth.
> But it's also much less useful.
Yeah, especially because all the things that make lunar space elevators a little more attainable also make lunar mass drivers a lot more attainable. Why ride in an elevator for a week if you also can just be fired from a cannon?
Space elevator was the perfect application for carbon nanotubes according my professor few decades ago. I wish humanity could unite for such project and enter space exploration phase. But I feel it will stay sci-fi forever.
Almost all discussions around space elevators focus on the cable itself, how to manufacture and deploy it, and completely forget about the issues that would arise afterwards:
1) How do you attach the climber to the cable without affecting its structural integrity? By squeezing it really hard? A material that's optimized for longitudinal tension strength is probably not very tolerant of lateral compression.
2) How do you provide power to the climber? A regular electric cable can't support its own weight, so either you have to attach it to the climbing cable, or you have to make it from the same material.
3) Is it even worth it? The climber needs to cover a distance of ~36,000 km, so even at 200 km/h it takes 7.5 days from the bottom to geosynchronous orbit. How many climbers and what payload can the cable support at the same time? Refer to issue #1 regarding limits in speed and mass per climber.
The throughput in tonnes/day is absolutely abysmal in relation to the immense upfront infrastructure cost per elevator. Compare this to SpaceX's Starship, which is getting closer and closer to fully reusable 100 tonnes to orbit in minutes. Space elevators will stay science fiction forever, not because they're infeasible, but because they're useless.
I love this guy.
Re playing this gem https://neal.fun/stimulation-clicker/
Careful folks! This escalates quickly. Do not use xdotool on this.
A beautifully executed project here, I bought Neal a coffee.
What evolutionary advantage, I wonder, is there to Ruppell's griffon vulture flying at 11400 meters?
edit: units
Not every behavior has an evolutionary advantage.
If anything, "evolution" filters out disadvantages (eg: can't survive because your neck's too short and that pesky giraffe is eating all the leaves you could reach).
Evolution kills what doesn't work.
but every behaviour has a cost. In cast of flight altitude its energy and distance to food, water, mating zones.
Darwin started with survival of the "fit". It changed to "fittest" in later editions.
Going up there's currents, going down... gravity. Sure it costs energy, but there's bound to be a tradeoff. Travel distance? Sight range?
Having a cost and being too costly aren't the same thing though.
Feets are actually just fine in anything related to aviation.
> Feets are actually just fine
Non-SI legacy units have been grandfathered in and 'accepted for common use', but ICAO recommends that SI units should be used[1] (eventually). China and quite the majority of the ex-USSR, for instance, use metre flight levels[2].
There have been at least two aviation accidents and incidents relating to unit mis-conversions. This is two too many. As an SI absolutist, everyone should switch to SI or units purely derived from SI (so domain-specific stuff like parsecs, electronvolts, and binary prefixes, if appropriately symbolled are OK). It is an internationally-recognised, and nearly universal standard that permeates every aspect of human lives.
[1]: https://aerosavvy.com/wp-content/uploads/2014/08/an05_cons.p...
[2]: https://en.wikipedia.org/wiki/Flight_level#People's_Republic...
I prefer to call them "footsies" or, sometimes "feet".
I just clicked the temperature thingy in annoyance because I don't use Fahrenheit and to my delight, it just switched to Celcius
Mine was automatically set to Celsius ;)
Neat! It would be amazing to see how the pressure changes with altitude in addition to the temperature.
Giant Space Bola is much more attractive. It is a 10000 km string with capsules at both ends. It rotates in sync with earth so that the speed at meeting point is the same. You just hop in and end up in space without much effort. Because it is freely floating you can move it around to avoid meteor impacts and other such shit.
Did you read Seveneves by Neal Stephenson? In the second part of the book, they use this and related technologies.
I think those technologies are mentioned throughout the book - just at a much larger scale in the second part.
No, thank you. Don't want any existential crisis today!
Was hoping would go to geostationary orbit as an actual space elevator would :)
Ditto, although you'd have to scroll about 357 times further.
I suppose it could be livened up by including the orbits of things, but there would still be lots and lots of empty space.
Such a lost opportunity, was hoping for another "space is massive" experience like already done in similar interactive maps.
Previous discussion on 20-apr-2023 https://news.ycombinator.com/item?id=35629972
I always enjoy Neal's pages. I found planes at high altitude very interesting, didn't know we could fly that high!
Wow, I'm really surprised to see some birds flying that high. Question: How the heck are they able to live normally at such extremely low temperatures?
Amazing work as always. Paired with Wikipedia it makes for a very productive day.
It is appreciated that you can change the temperature unit by clicking on it, and how surprisingly cold and changeable the temperature is as you travel up through the atomic sphere (down to -84C, -119F).
The rockets at higher altitudes were all in wrong orientation. In reality, they don't fly straight up.
It was enjoyable and informative.
Learned that sprites can be 50km long!!
Earlier this year, we were treated to an exceptional photo of one: https://www.smithsonianmag.com/smart-news/mysterious-red-spr...
An actual space elevator would need to be over 357 times longer though right?
Awesome site!
Excellent! My wrist started to hurt 0.01% of the way to the moon.
How on Earth do we know the maximal altitude for a pterodactyl?
The atmosphere of this reminded me of the game Outer Wilds
I was really disappointed not to see a sequel. No new games from the developers since.
Its development is really interesting, in that it was more a proof of a scientific paper to start with. Anyway one of their tweets from September 2024 indicates they're working on a sequel, despite their publisher (Annapurna, owned by Megan Ellison, daughter of Larry Ellison) having had some issues around then.
they are working on a new game. Outer Wilds doesn't need a sequel, leave it be, its perfect as it is ::)
I loved the visuals but space elevators are far more science-fantasy than hard science-fiction. We should move on to sci-fi tech that has more realistic applications.
Only for Earth. We already have materials that can do it on the Moon (Zylon, for example), though not with great tether-to-payload ratios (200:1 or more), and Mars isn't too huge of a stretch (huge like the mass of the tether, which would be in the thousands to one tether-to-payload ratio. Shipping 50,000 tons of Zylon to Mars is a different beast)
Lovely, great transitions!
What's really interesting is that a space elevator goes to Geostationary orbit by necessity. Getting to 100km vertically doesn't save as much as you might think when it comes to getting into orbit.
To get into a very low earth orbit from an equatorial launch pad at sea level you need about 9.2km/s of Delta-V
To get there from a 100km tall tower, you need about 8km/s of delta-V - about 85%.
Think about how much scrolling there was to get to 100km.
To get to the ISS you'd need to scroll 4 times further. Starlink and Hubble are another 100km beyond that.
You start having radiation problems if you spend too much time above 600km.
Aside from Apollo, the highest a human has been is about 1400km - 14 times more scrolling than this page.
To get to GEO would require scrolling over 25 times further than even that.
Incomplete. Where's the LEO, GEO, the counterweight?
I think the idea behind this was less to showcase an actual space elevator and more to showcase what's going on at different altitudes. And above the Kármán line it would have become pretty boring, especially if you want to go up to GEO and beyond where the counterweight of a space elevator would be located - the Kármán line is at only 0.28% of the way to GEO. Using a logarithmic scale would have maybe helped, but not sure...
Some huh! moments...
* Jeez, Everest is tall
* They got a plane to 17km in 1938!
* There was a paper airplane flight at 35km
Where is Elon Musk's Tesla?
Too far away to scroll: https://www.whereisroadster.com/
the website feels heavy, can we optimize this further?? (not a web dev)
I just looked at it in the dev console in a chrome based browser and I think it is already pretty optimized. It runs very smooth on my device (Thinkpad T480).