Thread by @DrPhiltill

Here's a perspective on satellite mega-constellations that nobody has mentioned. (We are ALL tired of this, but I think this is interesting).

The real reason SpaceX is putting up a mega-constellation at this time is because of the laws of nature. It was inevitable.../1

2/ Many metrics of information growth show exponential growth. Examples: Moore's law, computer speeds, agents on the internet of things, sensors. See review here: ourworldindata.org/technological-…

3/ Even before humans existed, we see evidence of exponential growth in information. Consider the sizes of genomes. This plot has a slope of 1 on a log-lot chart, so this is exponential growth in DNA complexity. phys.org/news/2013-04-l…

4/ And the famous plot by Ray Kurzweil showing major paradigm shifts as compiled by Carl Sagan, Encyclopedia Brittanica, etc. This, too, shows information growing exponentially because the time between shifts is exponential decay.

5/ Something feels almost magical about this, too good to be true, so skepticism alert. But it seems plausible from a math perspective because exponential growth is the solution to a simple equation that says information creates information (the rate is proportional to quantity).

6/ Also, from a broad perspective it is saying the obvious that information is growing at an increasing rate. First it was encoded in DNA, then in neural patterns shared orally, then by glyphs, then alphabets, then electronically. It is exciting to be part of this!

7/ The problem is information keeps exceeding its containers. We had to invent alphabets to manage the data that we were passing from one generation to the next. That was good, but it required new technology. Then we invented books, printing presses, computers, satellites...

8/ Dawkins said the phenotype is the product of the selfish gene (the information) working to replicate itself. In exactly the same way, civilization can be seen as the product of information working to replicate itself. It is now "selfishly" exceeding and damaging our planet.

9/ But I really don't think these are bad things. The phenotypes (the wonderful diversity of life!) are amazing. The things humans write and create are amazing. Civilization is amazing. I LOVE the exponential growth of information. But it needs a container bigger than a planet!

10/ Projection show that the current rate of growth in computing predicts that by the mid-2040s computers will need the entire global energy supply. If we can reach optimal efficiency in computing, it will delay only to the mid-2050s. The planet-scale is nigh.

11/ From this perspective, the need to transmit data at ever higher rates was pretty much inevitable, and not a bad thing, but something we need to divorce from the Earth's environment ASAP.

OK, now this argument will switch gears. (First, dinner break; I will return shortly)

12/ (I'm back) The way we transit electronic data was via phone wires, then satellite, then fiber optics. Believe it or not, the growth of data transfer is so high that in just a few years we won't be able to lay fiber optics around the world fast enough.

13/ The Royal Society in 2015 called it "the Capacity Crunch." It's a limit in physics, because Shannon's Law & glass melting temperature set a limit on fiber optic data transfer. We need new ways to transmit data that can scale-up faster than fiber optics.royalsociety.org/science-events…

14/ The reason we had to switch decades ago from satellites to fiber optics is two-fold. 1) satellites all use the same radio frequencies. They can use the same frequencies only by having narrow beam spots that don't overlap each other on the ground. birrraus.com/2016/06/05/wha…

15/ Once you use up all the available frequencies projected onto all the available beam spots on the ground, you don't have a lot of options for sending more data! (There are some options, but this is too technical for a tweet. Basically, the options are limited.)

16/ One option is to make the beam spots smaller so we can re-use the frequencies on more locations, so we can send more data overall. But smaller beam spots require larger antennas. So the limitation is...ROCKETS. The size of a ROCKET sets the size of the antennas we can launch.

17/ This is partially the laws of physics again, and partially an economic problem. Physics determines the size of an antenna for a beam spot, and the size of a rocket to launch that size antenna. Economics tells us if it is economically viable to use rockets of a certain size.

18/ Another way to make the beam spots smaller is to put the antennas closer to the ground, in Low Earth Orbit (LEO) instead of Geosynchronous Orbit. But here is the second reason we had to switch to fiber optics: 2) LEO satellites can't keep their beam spots over one location...

19/...because of the laws of physics. At that altitude, satellites go faster than the Earth turns. So if you want the satellites in LEO, then you need to have a megaconstellation so that as a beam spots slides away from your location there is always a new beam spot to replace it.

20/ But that was never practical (before now), because you can't service a customer if they only have a satellite over their location for, say, about 3 minutes per day. In order to have enough of these tiny beam spots painting the Earth you need an entire megaconstellation, and

21/ ...you can't subscribe customers until you have enough satellites up there in space to give them pretty good coverage throughout the day. So you can't make any money until investing HUGE amounts of money launching HUGE numbers of spacecraft. It was economically not viable...

22/... So a few decades ago we realized laying fiber optics all over the Earth, draping them across the oceans with ships & giant reels, digging along the sides of the roads, was actually a cheaper solution. So we got out our shovels and started digging thefoa.org/tech/ref/OSP/i…

23/ and we built ships with big reels and starting draping cables all the way across the ocean floors. More and more cables. This was cheaper than launching megaconstellations. pri.org/stories/2015-0…

24/ But the problem is that we can't keep up with this any more. Throughout all this time, we weren't really laying the cables faster enough. The only way we kept up with the data demand was because we kept inventing new ways to shove more data through the existing cables.

25/ Until we are now shoving so much data through the cables, that the light is so bright (to get a higher signal to noise ratio) that the glass is responding non-linearly to the light, and soon we will reach the melting point of the glass. That is the capacity crunch. #physics

26/ And here is the third part of this 3-part story. At the same time this has been going on, we have been having revolutionary advances in space technology. Spacecraft are becoming smaller and lighter, and rockets are becoming cheaper. Suddenly, megaconstellations are viable.

27/ I am NOT a fan of megaconstellations, because I am a fan of the technology that come NEXT, after megaconstellations have reached their capacity limit: giant antennas in geosynchronous orbit, phased array multi-beamforming technology, 100,000 beams per antenna.

28/ Because then you take advantage of another trick to re-use the same frequencies to send more data. Not only do you use each frequency on millions of beam spots, but each beam spot can point the same frequencies in 100,000 directions. (I had a role in advancing this concept.)

29/ The trick is that this concept uses the 3D nature of space instead of merely the 2D surface of Earth to get vastly higher re-use of the same frequencies. Using this method will enable the growth of data to the end of the century. But for that to work...

30/ ...you have to put antennas in geosynchronous orbit that are about 400 meters in diameter, way too large to launch. So you need to build them in space. In fact, I calculated that to keep up with data you can't even launch the raw materials from Earth fast enough. But...

31/...if you mine the Moon & asteroids you can build the antennas in space using materials from space. This is the ONLY thing that allows data rates to keep up the historic trend that has existed since way before humans even existed, resulting in the flowering of civilization.

32/ But even more important than building large antennas, we need to get the computers themselves off the Earth. And we need to get the supply chain that builds the computers off the Earth. And the energy sector, and its supply chain. Let's get that industry OFF THE EARTH.

33/ When we get this all off the Earth, it will unburden the environment from a HUGE industrial footprint equal to all of today's industry sometime later this century. We can do this. To get there, we need business revenues to fund all the tech development. And this is why...

34/...why I'm not a fan of megaconstellations. Because megaconstellations are still made on Earth and launched from Earth. They aren't necessarily a step toward getting all the industry off the planet. I see them as the competition to what we need to do. But on the other hand...

35/...the good news is that the architects of two of the early megaconstellations (SpaceX's nascent one and Amazon's proposed one) are both major fans of putting robotics and industry in space, and they plan to use the megaconstellations to fund space industry. So there's that!

36/ But I digressed. What I wanted to say is this: it seems almost like a law of nature that information wants to grow until it exceeds every container, including an entire planet, and this leads seemingly inevitably to megaconstellations as a step along the path. I would bet...

37/ I would bet that if we find alien civilizations somewhere else in the galaxy, or in a galaxy far, far away, we will discover that they ALL developed megaconstellations right before they got industry off their planets & divorced their information systems from their biosphere.

38/ So I was tweeting that, yes, megaconstellations are bad for astronomy, but there won't be any political will to prevent it, and it is going to get a lot worse before it gets better. I don't blame billionaires for this; they are as small as we are in the face of these trends.

39/ There are companies like Boeing (not owned by a billionaire) also planning megaconstellations, and there will be ones from China and India and many, many actors. Elon was just the first because he was on the cutting edge of making the rockets cheaper, a necessary step.

40/ So personally my hope is not in getting politicians to ban megaconstellations. That would require many different political systems around the world to agree together to NOT take advantage of the laws of physics to get advantage over each other geopolitically. It won't happen.

41/ Instead, my hope is that we can develop political will to create reasonable regulations that minimize the impact they have on the sky, until the day comes (really just a few decades) when we can start moving the source of all the vast data off the planet into space.

42/ So I am extremely grateful that the person who got to megaconstellations first is also a fan of space resources and robots in space. (He wants to support humans living on Mars, and the tech that does that is the same tech that can save Earth by putting info systems in space.)

43/ And I'm grateful that many other of the billionaires like Jeff are working to advance the technologies that will put industry and information systems off Earth. Jeff in particular has targeted solving global challenges by putting industry in space -- spot on!

44/ Also, @esa has identified lunar resources and a Moon Village (see @MoonVillageAssn for example) as their chosen strategies -- also spot on! And we have a NASA administrator @JimBridenstine who identifies space resources as the necessary revolution going forward. Awesome!

45/ If you think about how many things are lining up the right way -- long last! -- then you may agree we are living in an amazing, exciting time. There WILL be BAD problems with space industry as we go forward. Polluting the sky for astronomy turns out to be one of the first.

46/ I don't even want to talk about the really bad things that I am sure will come from space industry in the next few decades. (Hint: it's not pollution in space.) I have shared these ideas with only a few people, but there are groups already working proactively to address them.

47/ (Well, here it is: I am convinced democracy will fail in this or the next century unless we diversify equity in off-Earth industry. That's a story for another day.) Back to megaconstellations: I don't see them as the end of the world or something to get super angry about, but

48/48 they are something we can manage and a step along the path toward better things (but also more dangerous things), so they don't deserve to take our attention away from the bigger issues. Within a decade or two there will be regulations. I hope this philosophical view helps.