Here’s the ever-credulous New York Times:
A Big Night Light in the Sky? Start-Up Wants to Launch a Space Mirror.
The company is seeking F.C.C. approval to test an idea to reflect sunlight to Earth at night, possibly powering solar panels. Critics say it could be bad for people and wildlife. . . .
Reflect Orbital’s first prototype, which will be roughly the size of a dorm fridge, is almost complete.
Once in space, about 400 miles up, the test satellite would unfurl a square mirror nearly 60 feet wide. That would bounce sunlight to illuminate a circular patch about three miles wide on the Earth’s surface. Someone looking up would see a dot in the sky about as bright as a full moon. . . .
Two more prototypes could follow within a year. By the end of 2028, Reflect Orbital hopes to launch 1,000 larger satellites, and 5,000 of them by 2030. The largest mirrors are planned to be nearly 180 feet wide, reflecting as much light as 100 full moons.
The company said its goal was to deploy the full constellation of 50,000 satellites by 2035.
How much does it cost to order sunlight at night?
Mr. Nowack said the company would charge about $5,000 an hour for the light of one mirror if a customer signed an annual contract for 1,000 hours or more. . . .
There’s lots in the article about astronomers’ concerns about the night sky, confused animals, etc.
But what about a more basic question: Can this work at all, even on the terms claimed by the promoters?
This is a physics question, so we’ll turn to a physicist: Raghu Parthasarathy at the University of Oregon. In a post entitled, Space mirrors, solar panels, fools, and their money, he writes:
There’s no shortage of holes to poke. Here’s one that I posed to my Physics of Energy and the Environment class (for non-science majors) yesterday, leading into the exercise by reminding them that one of the aims of the course is to produce scientifically literate citizens, capable of critically and quantitatively evaluating claims. I also emphasized that they possess all the tools they need. (It’s week 9 of the 10-week term.)
Raghu continues:
Let’s consider the best-case scenario of a space mirror perfectly focusing light onto terrestrial solar panels. (No, this isn’t possible, but we’ll be optimistic potential investors!) . . .
A one-meter by one-meter square in space, at the Earth-sun distance, intercepts about 1.4 kW of power in the form of sunlight. As a result, at noon on a sunny day, the power per square meter hitting the earth’s surface is about 1.0 kW. It’s less in the morning or evening or on a cloudy day, but again let’s take the best-case scenario and imagine 1 kW / m2 as our solar power density, and the effective output of our space mirror.
“The largest mirrors are planned to be nearly 180 feet wide”. That’s about 60m × 60m, or 3600 m2. A good commercial solar panel has an efficiency of 20% for the conversion of sunlight to electricity. (If you’re wondering: Couldn’t I get an extra factor of 5 with a 100% efficient solar panel? Physical laws constrain the efficiency to at most 34%; the 20% efficiency of current commercial panels is remarkable.)
Electricity presently costs about 10 cents ($0.10) per kilowatt-hour. Given this, what’s the value ($) of electricity generated in one hour by a solar panel powered by one space mirror?
Here’s the answer:
$72. That’s the value of one hour of space-mirror-powered electricity, in the best-case scenario. How much will Reflect Orbital charge? $5000 [see quoted news article above]!
Obviously, $5000 is far larger than $72. For $5000 (per hour!), one could buy a lot of batteries to store power generated in the daytime, or build a lot of electrical transmission infrastructure, or rent a lot of monkeys to crank generators by hand.
Also:
The calculation above highlights just one of many fatal issues with the company’s scheme. To briefly note another: the light will spread out as it travels from the mirror to the earth, covering a large area with quite dim light. In the article, Brown estimates the area as 18 square miles! One would have to install panels over that entire span to capture the (best-case) kilowatt of power.
Asking some more physicists
Raghu’s argument is convincing, and I was able to follow it. Indeed, I’m not much of a physicist anymore, but back in the day I worked in a physics lab, and I actually worked on a problem involving the heat flux from the sun in Earth orbit (it’s in my first published paper).
Nonetheless, I was concerned that Raghu and I might be missing something, so I passed this along to my physicist collaborator (and occasional blogger) Phil Price, who responded:
When I [Phil] first heard the idea of space mirrors for directing energy to solar panels on the ground, my thought was “this is obviously complete nonsense.” Whatever size mirror you are building, just increase the size of your solar panel by that amount instead. Yeah, sure, with the space mirror you can get light at night too (if you have a high enough orbit) but that can’t be anywhere near worth it, considering the huge cost of launching the mirror, the impossibility of collecting all of its light, and the fact that we can store or produce electricity here on earth to use overnight so we don’t really need nighttime solar generation. It seemed totally stupid.
But . . . OK, sorry, I need a digression first, it’s just the way I roll.
For at least twenty years I had wondered why rockets couldn’t be reusable (at least the first stage): after the second stage separates the first stage is coming down anyway, and it has these big expensive engines on it, why not use parachutes, or fire up the engines again, or something, and catch the rocket down-range; maybe you can’t reuse the whole thing but you can at least recover the engines. So when I heard SpaceX was going to try to do exactly that, land on a platform in the ocean, I thought “see, I was right.” But, I think it wasn’t even very long after that, I heard that they were planning on bringing a booster back to the launch site rather than landing it downrange — and not bringing it back by having it do an orbit, but instead by having it reverse course — and I had the same feeling I did with the space mirror idea: this cannot possibly make sense. You’ve expended huge amounts of fuel getting this thing to haul ass eastward as fast as it can, and now you’re going to burn fuel to kill all of that momentum and get the booster going back the way it came at that same high velocity? Sure, it has burned most of its fuel so it’s a lot lighter by now, but it can’t be _too_ much lighter because it is going to require a fair amount of fuel to get it going back. “You don’t need to do a detailed calculation to know this is a terrible idea”, was more or less my thinking. And yet, here we are ten years later and they are doing this all the time, and not just as a demonstration project but because it’s cheaper and faster than getting the rocket back by landing it on a ship and sailing it back and having to move it back to a launch pad etc. My thinking was wrong for two reasons: 1 it’s not as prohibitively fuel-consuming as I thought instinctively, to have it turn back around, and 2 if you land on an ocean platform instead, you still have to somehow get that booster back to a launch pad, and how are you gonna do that? It’s one thing if it’s a smallish rocket that you can transport by truck or train or something, but for the big ones they have now it is a major undertaking.
So, with that example of my physical intuition failing me, along with a few others over the years, I now try to trust my instincts less and rely on calculations more.
And Raghu has done the calculation and it confirms my intuition. Yay. I don’t see anything wrong with the calculation… and the calculation would have to be spectacularly wrong in order for space-mirrors-for-terrestrial-power to make sense.
Semi-related, Wikipedia tells me the Russians once made a space mirror as a test of… well, it’s not clear really. I think the subtext is that this was a zombie project: they decided to build a mirror to test the idea of a solar sail, but sometime mid-project someone decided not to pursue solar sails after all, but rather than cancel the project they repurposed it as a test of nighttime solar illumination… which, in this case, meant a very brief flash of light if you happened to be in the path. What a waste of everyone’s time. I wonder what they could even claim to have learned.
So, yeah, this is utter nonsense. You heard it here thirtieth.
OK, then.
Problems with the news media coverage
As Raghu notes in his post, the New York Times article “has the usual flaw of wanting to appear fair, presenting ‘both sides’ of a story even if one of the sides is absurd, but it does cite people who are critical of the concept.”
I did some googling to see how this was treated in other media outlets.
The only major news report I could find expressing concern on the physics was this article from New Scientist, headlined “Controversial satellites launching in 2026 will reflect light to Earth Reflect Orbital plans to launch thousands of reflective mirrors to produce ‘sunlight on demand’, but researchers are sceptical about whether the reflected light will be enough to generate electricity”–but even there, it’s just controversy and skepticism, not, “Hey, this can’t work as advertised!”
More typically are these headlines:
– SpaceX and Reflect Orbital plans would ‘permanently scar’ night sky, researchers warn
= SpaceX and Reflect Orbital plans could “permanently scar” night sky, astronomers warn
= California startup’s plan to sell sunlight at night sparks controversy
– The Dark Side of Putting Mirrors in Space
The common theme here: A tech startup is building space mirrors that are gonna change the world, possibly solving our energy problems, but there are some astronomers whining that it will mess up their telescopes. Ummm, unlimited energy vs. concerns about the night sky . . . I wonder which will win? Even the articles that are clearly opposing the project are framed in a way that takes as given that they can solve technical challenge of delivering the power they claim.
To be fair, I did come across one article that addressed the physical difficulties, but even there you might not catch the problem from the headline: “The true cost of ‘solar power at night’ with Reflect Orbital.” But, yeah, one article, and that’s it.
Mostly, the press is treating this as technology that will work but it might not be dangerous. Not that it can’t work and that it might be a scam.
Here’s Raghu again:
What should one think of Reflect Orbital? There seem to be three possibilities: (1) Reflect Orbital is run by idiots. (2) Reflect Orbital is run by criminals, unethically pitching nonsensical, nonscientific schemes to a gullible audience. (3) The space-mirror solar power idea is just a hook to get money and attention for some other aim, to be announced later. . . . None of these are cheery conclusions. I’d bet on (2), and the likelihood of this being a fraud bothers me more than most frauds because of its faux-ecological costume.
I have no idea what to think. But, no, this doesn’t sound like something that can work as claimed on Earth.
One more physicist
Further googling turned up this post:
Clicking through yields Maguire’s profile: “Partner @sequoia // @caltech physics PhD // Views are my own.”
So here’s one credentialed physicist who does seem to think these space mirrors could work. Raghu’s reasoning was pretty convincing to me, and it was backed up by Phil, but, still, . . . maybe there’s something we’re all missing?
So I sent him an email:
Dear Dr. Maguire:
I came across this post of yours about Reflect Orbital: https://x.com/shaunmmaguire/status/2031846462632640828
But a physicist colleague of mine makes a direct and convincing case that their numbers are off by two orders of magnitude, that they’re proposing to charge $5000/hour for electricity that could be bought in the open market for $72 or, likely, much less.
I see that you have a physics degree so you might have some thoughts on this?
Yours,
Andrew Gelman
No response yet. My guess is that Maguire heard about this space mirror thing, maybe someone he knows sent him the video, and he just assumed it could work as advertised. That is, I conjecture that he did not turn on his physics brain when considering it.
I’m not trying to slam Maguire for not answering my messages–he might feel that it’s a better use of his time to post on social media than to read random emails.
A problem with science and technology reporting
This episode reminds me of himmicanes, marshmallows, or the sleep guy, or various other Epstein and Ted bait.
As I wrote in the context of “Mars One“:
From a scientific or technological standpoint, it wouldn’t be quite right to call Mars One a “failure,” as it was never a serious plan to begin with. If Nasa tries to reach Mars but the rocket blows up, that’s a failure. If I start digging in my basement but I never reach China as planned, that’s not a “failure,” really, as there was nothing there to succeed or fail in the first place. As science or technology, Mars One was not a failure; it was a publicity stunt.
The space mirrors example is particularly clean because the physics calculation is so straightforward, and their claim is off by two orders of magnitude. But it’s part of a larger asymmetry in which it seems there are big incentives to promote ideas that can’t possibly work and not much incentive on the other side to be careful in your claims.
Remember that physicist who made the fatuous claim that that scientific citations are worth $100,000 each? He’s still around! I mean, sure, we laugh at him, but he’s a Distinguished Professor, a member of the National Academy of Sciences. Fine–I’m not saying the guy should be fired or anything, just because he wrote something stupid–; my point is just that there are some asymmetrical incentives for these researchers, and also for the people who write about them. So that’s how you get the pattern that hypey and sometimes ridiculous claims are promoted, and then on the other side there’s just some vague skepticism, which can lead the reader to a vague intermediate position that maybe there’s something there. Sometimes maybe there’s something there, sometimes not.
Citizenship takes work, even for physicists.
Recall this line from Raghu’s post:
One of the aims of the course is to produce scientifically literate citizens, capable of critically and quantitatively evaluating claims.
That tech investor and physics Ph.D. quoted above has the capability to critically and quantitatively evaluate the claim from the space mirror people. But he did not exercise that capability. We’re all busy people, and it’s easy to pass along a link and a blurb without engaging.
P.S. I clicked on the bio of the first author of the linked NYT article, where it says, “I studied physics in college — I have an undergraduate degree from Princeton and a master’s from the University of Illinois at Urbana-Champaign.”
So, yeah. Those two physics degrees won’t do you any good if you don’t put on your thinking cap, as they used to say in elementary school.
P.P.S. Update here.
Read up a bit more on Shaun Maguire. Doesn’t exactly have a track record for turning on his brain.
To save people a little work:
https://techcrunch.com/2025/07/11/sequoia-bets-on-silence/
https://techcrunch.com/2025/12/19/sequoia-partner-spreads-debunked-brown-shooting-theory-testing-new-leadership/
Cold fusion? I’m asking because I am terrible at physics and others may be able to comment on the relevance of cold fusion to this post. The 1989 frenzy was repeatedly debunked yet doesn’t ever seem to disappear. Is it an example of how hard it is to week crazy ideas out of the press or is it an example that crazy ideas sometimes contain ideas that may eventually lead to worthwhile discoveries? How does the worthy goal of producing “scientifically literate citizens” treat the case of cold fusion? Raghu? Phil? Anybody?
Dale:
We discussed cold fusion here a few years ago. It’s an interesting story, different than the space mirrors example because the purported mechanism of action is much less well understood. But, yeah, from the outside it looks like it went like this:
1. A sloppy experiment was performed.
2. The results were hyped locally, and the national media swallowed it.
3. The experiment is no longer taken seriously.
4. But, in the meantime, lots of theory was constructed to explain a result that actually never happened, and that theory has motivated a continuing flow of work on the topic.
Which doesn’t seem right, but, hey, you never know, I guess.
The space mirror thing seems different in that its purported justification seems to be off by at least two orders of magnitude. As Raghu says, maybe they have a plan to use the mirrors for a different purpose, or maybe they have a plan to get billions of dollars in government subsidies and make money that way, or maybe they’re planning to raise the money for the space mirrors and spend it on something else, who knows? Cold fusion seems more like a conventional science project, just something that probably has no hope of working.
The argument seems to imply that if electricity was 100x more expensive, the space mirror would be worth it? I’d question that $0.10 per kWh as hiding a lot of variability. E.g., 200x spikes have happened recently:
https://en.wikipedia.org/wiki/2021_Texas_power_crisis
What about remote bases like in Antarctica, during an energy crisis, etc?
Supposedly, electricity is even normally as high as $0.50 per kWh in some countries:
https://www.expatriatehealthcare.com/top-10-countries-with-the-most-expensive-electricity-prices/
Then I get 5000/(72*5) ~14x too expensive. My point is just that the $0.10 per kWh assumption seems quite dubious.
Anon:
Nah, the factor is way more than 14. As Raghu discusses, that $72 is itself a crude overestimate.
I found a price in Antarctica of $4 per kWh:
https://www.thecooldown.com/green-tech/south-pole-antarctica-renewable-energy-diesel/
So its only about 1.7x the normal (not surge/emergency) price at some places on Earth. Just sayin, that $0.10 per kWh assumption appears to be hiding 2-3 orders of magnitude variation.
@Anoneuoid
From your own link, solar power *in Antarctica* is only $0.23/kWh!
My interpretation was that was a proposal, and they don’t currently have (significant) solar power at McMurdo. And if they did, it would be dark half the year thus left unused. The point was more there are remote locations where electricity costs much more than $0.10 per kWh.
Also, I didn’t look into this project at all but who are the expected clients? Is it really solar panels rather than military, festivals, etc who may want 20% daylight at night over a few square miles? How many clients do they need at these rates to fund the space mirrors?
In general, I don’t think this analysis addressed the use cases which could make the project economically viable.
“Who are the clients?” is a good question. I would think that they are probably data centers who want the produced electricity. The idea is not to light up a place, the idea is to feed solar panels.
Elin:
Sure, but given the cost, it doesn’t make sense. Why should a company pay $5000/hour to feed their solar panels if they can buy the same amount of electricity off the grid for much less than $72/hour?
Yes, it’s true that electricity might cost more than $0.10 / kWh, but keep in mind that:
(i) in general, my estimates are severely skewed in favor of the space mirrors, and they still look awful. For example: 1000 W/m^2 is the incident power at noon on a sunny day; the mirrors + panels aren’t going to be achieving this.
(ii) related to (i), I didn’t even include the other fatal flaw that the sunlight will be spread over a few miles, at best. (As a commenter notes below.)
(iii) it’s true that one can imagine situations or places where electricity costs much more than $0.10/kWh, but note that the space mirror scheme requires that one can build and run a solar panel array. I find it very hard to imagine a situation in which one has an array of panels that one can run in the daytime and still find that $10/kWh space-mirror-energy makes sense.
Anon:
I have no idea if this company has a business plan beyond burning through VC money and hoping for a government subsidy. My problem is with the credulous news reporting. I’d be fine had the news articles quoted a physicist explaining that the company’s stated plan was off by at least two orders of magnitude. And then if they wanted, they could’ve said that some speculate that there could be a niche market in Antarctica or whatever. That’s not what the company was talking about, but, sure, whatever.
Ah, I didn’t think I would be able to read the NYT article due to the paywall, but it showed up and I saw this:
If that is what they are promising then it does not make sense unless oil/coal/nuclear become much more expensive. I doubt that is the actual plan though.
Hmm. $28 million seems pretty cheap.
The last I checked there were _at least_ 13 companies each with over $1.0 billion in vulture capital putting shovels in the ground to build fusion power stations. Every company has a different tech, and none of those techs have ever demonstrated fusion…
Also, weirdly, this is a really old idea. The last time I heard it, I think they were talking about beaming microwaves or the like down.
“If that is what they are promising then it does not make sense unless oil/coal/nuclear become much more expensive.”
Nonsense. It doesn’t make sense because we already have sunshine on half the planet at every moment, and we have a cheap means of harvesting that energy and also means of storing it (not quite as cheap but certainly cheaper than these satellites).
These mirrors, if they exist, would at best add a fraction of a millionth of the amount of sunshine that we get for free all the time (btw they would also add to the earth’s energy balance – which you might be aware is already overheating).
It makes no sense whatseoever, except very very hypothetically in the most unlikely of edge cases. But “we are trying to solve some unlikely edge cases” is the opposite of “we will power everything”. Anybody with haldf a brain would immediately have understood this.
It’s worth noting a few things.
1) These sort of spikes are rare, short-term, and reflect only spot markets when most electricity is purchased via longer term contracts that don’t vary in the same fashion. So numbers like .1$ a kWh incorporate these spikes and their relative infrequency and small portion of the market.
2) To use these sorts of higher prices to justify the large up front capital spending, you need to find customers constantly using the mirrors as most of your cost is in launching/building the mirrors not operating the mirrors. So using it as peak load system is bad since it would only be some of the time. A good peak load system is one that can sit idle at low cost and only costs money to use. Launching satelite is the opposite of low idle cost.
3) Night time power demand is relatively low and power cheapest then. Nuclear, hydro, conventional gas, and coal plants are typically run 24/7 due to moderate to extreme turn on/off costs so they provide plenty of power cheaply (wind is often productive at night as well). So nightime solar would likely be low value. (Late afternoon solar would be higher value as thats when net demand is highest. However, batteries+daytime solar have solved that issue more or less anyway.)
So to put it all together, the average price of power is what should be used to justify this sort of high fixed cost, low marginal cost power investment, and not rarely observed peaks.
I don’t know how rare the spikes are. Eg, is there always somewhere in the world were prices are surging 10-100x? Is this happening somewhere weekly/monthly/yearly?
As a source of solar power, space mirrors seem more like something for remote bases or to be used as insurance. $5k per hour means ~$44 million per year. The Texas crisis apparently cost 400x more than that:
https://en.wikipedia.org/wiki/2021_Texas_power_crisis
I’m not defending this project as I know nothing about it. Just that even a back of the napkin quantitative analysis needs to be more sophisticated for me to take it seriously. Going bankrupt or freezing to death only needs to happen once, so smoothing all this variance away with a average seems wholly inappropriate to me,
The claim in the NYT about replacing all fossil fuels is dumb though. I also like how beaming extra sunlight at the earth apparently isn’t expected to warm it.
Spikes of that type are once in a decade type event. There is lots of within day volatility within deregulated electricity markets but its a lot like penny stocks, lots of bouncing prices on small quantities. Not the sort of situation where you could say get a couple day contract at scale.
The reason an average price is appropriate is because of the economics of this sort of project. The costs are almost all up front and ongoing costs are independent of if the infrastructure in use. So the optimal use of such a system is for it to always be on and producing (Basically how solar panels and wind power work today). So it doesn’t matter if its profitable 2 hours a week as no one would run it two hours a week, they would run it every hour and hope that the two hours of profit are enough to justify a week’s operations and the upfront cost. A long run average will do a good job of incorporating that information and would be a pretty dang good estimation of the hourly average profit which can be combined with lifespan to compare to launch costs. It also fits with the business model pitched in the quoted article which suggests 1000s of hour contracts signed at a fixed price in advance which would reflect long-run costs, not hourly market prices.
TLDR: Hourly cost fits the industry and proposed business model so its the correct metric for a basic viability calculation.
It doesn’t matter how expensive electricity gets, this will never make sense as a way to provide it. Instead of spending huge amount to send mirrors into space, you can build a solar array on earth with battery storage for cheap. Save 99.9% of your money and get 10x the power. Or save 99% of you money and get 100x the power.
Anoneuoid —
You say: “I also like how beaming extra sunlight at the earth apparently isn’t expected to warm it.”
I assume that’s a joke? I’m no physicist but my guess is that the “extra sunlight” that would have missed the Earth otherwise is just a tiny, tiny fraction of the sunlight that does reach the Earth. An llm tells me that even their wildest plan with 50,000 largest mirrors would redirect only ~206 GW total — roughly 0.00012% (1.2 parts per million) of the ~174 million GW Earth already receives.
The purported benefit could be from concentrating that small fraction, not from harnessing “extra sunlight” which couldn’t conceivably, measurably warm the climate.
Andrew, it’s very difficult to understand at a gut-level the vast gulf between STEM people and the overwhelming majority of journalists and similar. Yes, there’s the occasional rare exception. But almost all of them regard even the simplest probability calculation to be deep dark magic, and somewhat disreputable. An energy flux estimate like the above is just way beyond their comprehension. Thus they cover it like they cover all stories – controversy, sides say, etc. I have no idea what to do about this.
Seth:
Yes, and even quantitatively-trained people don’t always think quantitatively, as can be seen by the example of the physics PhD and tech investor above.
Seth:
You write of “the vast gulf between STEM people and the overwhelming majority of journalists and similar.”
But I clicked on the bio of the first author of the linked NYT article, where it says, “I studied physics in college — I have an undergraduate degree from Princeton and a master’s from the University of Illinois at Urbana-Champaign.”
Ulp.
The second author has a degree in international relations, so, sure.
To be fair, you can find people with degrees in a field demonstrating gross incompetence in that field when convenient. In economics for example you can find prominent figures saying things like how unemployment is low because everyone has two jobs. You can even find Harvard econ PhDs saying that reducing imports increases GDP because GDP = C + I + G – IM + EX. I guess having a credential doesn’t seem to mean much if there’s a story to be told.
Will,
Sure, we see experts bullshitting all the time, trading on their professional authority to make stupid and unjustified statements. I’m still annoyed at the yahoos who criticized our 2024 election forecast for not predicting a landslide. (Narrator voice: The election was not a landslide.)
In this case, though, I don’t see the tech investor or the news reporter as claiming any authority based on their physics degrees; indeed I don’t see them as making any arguments at all. They’re not making bad arguments about the physics, they’re not making good arguments about the physics; they’re just not turning on their physics brains at all.
And, yeah, sure, I understand: News reporters are working on a zillion stories at once and don’t have time to check everything. And tech investors may have time to post on social media but that doesn’t mean they have the quiet time to think quantitatively. It’s hard to have your brain on all day long. But . . . yeah, it’s annoying!
A great post!
Leaving aside the ecological damage (and damage to human health) of persistent nighttime illumination), these mirrors are not going to stay in one place in the sky. At an altitude of 400 miles, they are going to be orbiting the Earth in about an hour and a half. No mirror or group of mirrors could remain pointed at any particular place on Earth for a useful time.
Tom:
All this makes sense, but what bugs me is that the news articles were not mentioning the most basic thing, which is that even under unrealistic ideal conditions, the system could not deliver power at a reasonable price. All the stuff about ecological damage seemed to miss the point. It reminds me of those news articles talking about the ethical quandaries of Mars One without recognizing that it was ridiculous from a scientific and engineering standpoint.
Yes indeed. I was just looking at yet another dimension where the scheme just doesn’t make sense.
As the NY Times itself recently noted, the NY Times has a track record of getting physics wrong. In 1920, it ridiculed Robert Goddard for his early rocketry experiments, claiming that rockets could not work in space, since in a vacuum there’s nothing for the rocket to push against. The Times’ eventual correction came in 1969, during the mission of Apollo 11:
“Further investigation and experimentation have confirmed the findings of Isaac Newton in the 17th century and it is now definitely established that a rocket can function in a vacuum as well as in an atmosphere. The Times regrets the error.”
Recent story here: https://www.nytimes.com/2026/03/16/science/robert-goddard-rocket-100th-anniversary.html?searchResultPosition=1
One of my favorite posts. Thanks to all of you, especially Raghu.
OK, maybe providing electricity via panels orbiting earth is not efficient, but have you considered the complimentary uses. Large panels in orbit could provide shade! We are seeing record high temperatures all over earth including the southwestern US. Shading the sun might be very helpful. I will be accepting interested investors to help fund research into shadow panel wire as soon as a few legal hurdles are overcome.
Large panels on Earth can provide shade, much cheaper.
Shadow panel wire:
https://en.wikipedia.org/wiki/Ringworld
” Night is provided by an inner ring of shadow squares which are connected to each other by thin, ultra-strong wire. “
I have seen proposals for that too.
https://en.wikipedia.org/wiki/Space_sunshade
“Realistic sunshade system at L1 for global temperature control” https://ui.adsabs.harvard.edu/abs/2021AcAau.186..269F/abstract
another thought
diam(sun)/dist(sun) = (864000/93000000) ~ .01
so diam of suns reflection in a point mirror on earth from 400 Mi ~ 4 mi
that’s a lot of solar panels to catch reflection form 60 m square
(subject to someone finding the errors in my back of the envelope guess)
Yes, this is also an excellent point and another (independent) fatal problem of the space mirrors. (Others have noted the spread of the sunlight also.) I intended to make a follow-up post about this, but I haven’t gotten around to it…
There is also solar radiation pressure, after all, these are like solar sails, not like regular satellites, some of which have to pay attention to this already.
Also, glad to seequotes from Michael Brown, Monash U (Australia) astrophysicist I’ve corresponded with, sensible guy.
This is a wonderful post and ought to embarrass the gullible journalists you cite. Just one more thing to add: the space mirror thing was not just a random absurdity, it had the characteristics of “tech will save the world”, which is something being pushed on us regularly. No need to fret about energy shortages or climate change; we’ll launch some rockets and solar power will be unlimited 24/7. And it won’t be done by some do-gooder, blundering government but brilliant entrepreneurs who will make a ton of money by delivering abundance. Don’t worry about the math — it’s the meme, baby!
We are being inundated by this slop, and since it represents one of the major political ideologies of our day, the one currently holding power, journalists feel they have to treat it with respect. This side says this, but the other side says that.
For anyone with a modicum of quantitative skills and a normally skeptical mind, this simulacrum of techie-ness is infuriating. An ideology can be well-funded, politically and culturally dominant and still be a hoax.
Did you see Elon Musk’s Terafab announcement? He says he is to make millions of chips, 1-10 billion humanoid robots per year, launch gigawatt and maybe terawatt data centers into space, and colonize the Moon. It all seems like science fiction to me, except that he does have a record of accomplishments.
He also has a long record of claiming he’ll achieve accomplishments that he never achieved.
The obvious business plan here is to get a constellation of these up then beam down daylight onto rich cities at night and get them to pay you millions per day to stop doing it so people can sleep.
FWIW, in addition to being a total crank Shaun McGuire is a partner at Sequoia Capital, which is one of Reflect’s major investors: https://sequoiacap.com/companies/reflect-orbital/
Chris:
Interesting. Then it makes sense that McGuire would want to hype the project. But it makes it even more puzzling that they’d invest in it in the first place.
As David pointed out earlier, this was discussed in the 1970s but using photocells in orbit and microwaves on the downlink. See https://www.osti.gov/servlets/purl/1650318 or, for more recent examination of the concept, https://www.esa.int/esearch?q=power.
The European Space Agency item (from September, 2022) I linked to describes the successful transmission of power over a distance of 36 meters. So, it is only a matter of routine engineering to scale that up to the 36 million meters from earth to geostationary orbit.
Look up “EEVblog 1637: Solar Freakin’ Space Mirrors! – Reflect Orbital Debunked”on YouTube
Thanks. That was informative. If anyone is interested, start watching at about 14:00 into the video; this is when the calculations start. Here’s the calculation that’s not presented in this post (on any of the links): one mirror, reflecting to Earth, will generate 5 milliwatts per square meter per 30 minutes. I had to Google what this could power. The only thing that I could find was a bluetooth receiver.
“5 milliwatts per square meter per 30 minutes”. That can’t be right. power / time isn’t any useful quantity. It presumably is *energy* / 30 min = power. Maybe the intent was this?
“enough energy per square meter every 30 minutes to provide 5 mw”.
The scientific and indeed numerical illiteracy of many journalists is exasperating. But maybe we shouldn’t expect them to do the work of scientists. After all there are enough actual experts around who could be asked to evaluate a scientiifc claim. *What I do expect them is to do the work of journalists.* And they clearly haven’t.
Journalists are supposed to approach the subject with a dose of healthy skepticism and ask tough questions, such as “What is this good for? Who needs it? What problem does it solve that isn’t already solved? Why would anybody want to pay for this? Is this project a good use of money and resources?”
And apparently, almost no journalist did ask any of these questions. They credulously repeat the promoters’ claim that their mirrors could “replace fossil fuels and really power everything”, which should activate the scam alert in every functioning brain. Are they really this gullible? I find this hard to believe. They are professional journalists after all. I wonder, therefore, whether maybe they understand full well that this is implausible but their editorial guidelines require them to cover it as if it were legit. I think this is a real possibility.
After all, that’s how they also cover the bullshit coming out of Trump and his minions: always cover it as if it were legit, as if they weren’t lying, as if it weren’t grossly illegal, as if they weren’t the most corrupt administration in history, as if their dumb-fuckery actually had benign and rational motives.
This is what has become of mainstream journalism.
Piglet:
Try reading Noam Chomsky’s book “Manufacturing Consent”. He explains at great length that mainstream journalism has always essentially been government propaganda, and he also explains why.
In a nutshell: mainstream media is made by large corporations, whose interests are closely tied to those of the government, and media coverage reflects those interests. Journalists who are too outspoken in the “wrong way” are culled (e.g. Phil Donahue at MSNBC for speaking out against the 2003 Iraq War.) Even if they are not culled, they are denied access, which is necessary for mainstream journalism. The other ones learn pretty quickly what is acceptable and what is not.