kerbiloid

Cars, elevators, trains and arcologies. 200 years ago: It's really mad to believe that a horse-driven carriage can be replaced by a lifeless iron thing running (just imagine this nonsense) under the ground along the iron bars. Do you really think anybody will use it? How do you think to tranport a million people per day through the narrow tonnels?

According to sounds like behind "flyby" author means "without landing" rather than "approach and immediately fly away".

One of numerous products of different reactions between hydrocarbons and carbon oxides. Link contains some info, but this doesn't matter. Main idea is: "there are hydrocarbonoxide-like substances which are more or less green and definitely can exist in a gas giant atmosphere, maybe even in great concentrations. No chlorine, no fluorine")

Btw if first create planetary intrascopes (opposite to telescopes), this would be much more useful than a starflight and would provide the starflight with much greater reasons.

In "Expanse" this happened when they were captured by a Mars battleship.

Removing "wow"s, a dwarf radiogalaxy smaller than Magellanic Clouds (as ).

Old star → old planets → geologically dead planets and either dissipating or overheated (greenhouse gases) atmosphere, i.e. a crashed balance of a matter circulation. So, the older the planet → the more primitive lifefroms we can meet.

Originally (and in further use) Energy was meant as a reusable rocket. That's why its boosters have parachute containers (filled with a measurement equipment during both flights). https://translate.google.ru/translate?sl=ru&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fwww.buran.ru%2Fhtm%2Fgud%252021.htm%23rocket&edit-text=&act=url

In this case you need no programming for every motion of the Mars rover. You need a pack of geologists onboard and a pack of drider-like wheeled avatars on the surface. Once a geologist meets an interesting sample, he doesn't report and wait for several days while his mission is being debugged. He just makes a selfie with this stone, pries it out with an axehammer and puts into a bucket. You don't need to code a script and test it on the Earth geologist's twin before use on Mars. You can just tell him: "Look, Jebediah. Do you remember than stone looking like a frog near the right side of that rock? Please, return back to there and try to take a sample from a 1 meter depth." He (i.e. his drider-avatar) takes a shovel, a bucket and an axehammer and just does all what he is wanted to. So, this way is a combination of humans' abilities and robots' expendability. With no headache about Mars life support and about launch from Mars. All you need to launch is a barrel with stones.

Earth vs Mars. Earth continuously and unsuccessfully tries to convince Mars to build greenhouses for food and declare its independency. Mars grins and declines that again and again. Earth keeps sending supports to Mars - as has no choice. If calculate with ISP= lightspeed (i.e. with antimatter propellant), millions tonnes of antimatter looks even more ridiculous.

Why that rack? It can just spray them into orbit through a tube. Spore-sat.

Any city with such population and production capacities would require much more water than it displaces with its weight. → It anyway requires huge pumps to upload this water and energy to power these pumps. → No additional gain if place it in water rather than near it. → It can be a district of a near-sea but on-ground mega-city.

Super-tiny sats can inherit a common name: "Kesslersat". Launch a million of them at once and gain the right to give a name for a new Earth particle ring. Of course. Then even can be equipped with a re-entry crewed module for two cockroaches.

Diacetyl seems to be green colored. Also it's simple, not aggressive, consists of extremely common elements.

The strict way to add something: to double its bud. So you can get two pairs of arms, two pairs of eyes, etc. If this increases the species' ability to survive, it has chances to stay in future.

Most satellites are less hardened than military equipment.

You already are moving all these millions every day. But currently you move them by cars, buses, etc - and just don't see them at once. Currently you are moving them for 100 km, in arcology - 1-2 km. From POV of the system in whole, the total amount of moving objects will stay the same, while the distance decreases for dozens of times. And nothing prohibits to take down a section of the arcology, previously disconnecting it from the pattern. But then it's much easier to rise its replace if you have a ready building scaffolds aside - its neighbor sections. Already with energy, water and transport.

Oort cloud is yet presumed to be, afaik. Nobody yet have seen this directly, it's a statistical generalization of observed trajectories. Maybe its a cloud, maybe it's just a cutoff. We've probably already seen 99% of surface, but if gather all those scientific crafts together, whether there's enough sense to send them in such expedition while we can just presume: if there arer under-ice oceans, what are Titan lakes below the first several meters, what is Jupiter under its upper clouds and its Red Spot and so on.

The ideas of air flight had been around for millenia. Abilities were poor. Just look at any nowadays capital city. A pyramide-like bunch of skyscrapers (the wannabe arcology) surrounded by endless fields of cottages with hundreds of thousands kilometers of roads, pipes and cables per city. The only conceptual change: replace the roads between the skyscrapers and connect them into a bound structure.

Instead of 2 hours and 30-100 kilometers of car driving you need to cross a square and take a lift or an escalator. Up - several hundred meters, which is already not a great problem. Power density of radiant energy ~ 1/distance2. To create the same power density on the receiving antenna you would apply in transmitter (1000/10)2 = 10000 less power when you are in 10 m from the receiving antenna, rather than when you are in 1 kilometer. So, as transmitting devices power decreases many times, the total energy lost decreases in turn. It's much easier to keep warm a ton of cow, than a ton of mice.

Smartphones themselves - yes. But smartphones are just hand-held terminals of the content distribution in total. They have appeared ~10 years ago - when the data traffic (TV, internet, etc) achieved the level when a handheld phone+TV+computer pack became economically reasonable. So, with old data infrastucture the smartphones would be mostly used as mobile phones, rather than portable media&game center. OK, maybe not pagers, but Siemens S60.

Transport problems inside an arcology just disappear, because distances are, say, 2 km horizontally and several hundred meters vertically. So, a car transport just has no place to be. So, no roads are required inside the city, no parking places, no fuel stations. All you need - electric elevators, electric rail carriages. Like in "Aeon Flux" movie or so. Ventilation is also not a big problem, as currently you anyway have to use an artificial air conditioning in any large building. In arcology instead of millions tiny pipes you use thousands of large pipes. Energetically this is even more efficient. The same with cable and mobile phones infrastructure. Instead of billions tiny cables you put thousands of thick ones. While now your smartphone tries to connect to a base station in a kilometer away, there it just connects to the closest wall antenna. Or more, you don't need a smartphone at all, just touch the closest on-wall display. Modifying/repairing is much easier in such city as: you always can provide your building efforts with a ready industrial infrastructure in one step from you. And you can put cranes on the closest "sub-buildings", rather that to mount it from ground or use crane helicopters. Also you can replace just selected parts of the whole city structural pattern, leaving others intact. Of course, such city will by default loose less energy for "square/cube" law, and emit much less radio waves. So, ET spaceship would discover a wildly looking planet with packs of of voiceless pyramides connected with railway tubes.

Also one objects being dropped, fall down (with different speed), while others are moving upwards. For example, apples are moving up.

Old buildings made of bricks - yes. But large so-called "buildings" are bunches of concrete cells pitched around giant spatial loadbearing frameworks. Look at a gothic cathedral as a minusculus sample. It's a large spatial carcass filled with (relatively) lightweight inner and wall elements.

Of course as "struts" I mean not "metal ropes", but horizontal constructions similar to the vertical buildings themselves. Tetrahedron is the simplest and best example. An artificial crystal lattice.