More on Science

Tomas Pueyo
2 years ago
Soon, a Starship Will Transform Humanity
SpaceX's Starship.
Launched last week.
Four minutes in:
SpaceX will succeed. When it does, its massiveness will matter.
Its payload will revolutionize space economics.
Civilization will shift.
We don't yet understand how this will affect space and Earth culture. Grab it.
The Cost of Space Transportation Has Decreased Exponentially
Space launches have increased dramatically in recent years.
We mostly send items to LEO, the green area below:
SpaceX's reusable rockets can send these things to LEO. Each may launch dozens of payloads into space.
With all these launches, we're sending more than simply things to space. Volume and mass. Since the 1980s, launching a kilogram of payload to LEO has become cheaper:
One kilogram in a large rocket cost over $75,000 in the 1980s. Carrying one astronaut cost nearly $5M! Falcon Heavy's $1,500/kg price is 50 times lower. SpaceX's larger, reusable rockets are amazing.
SpaceX's Starship rocket will continue. It can carry over 100 tons to LEO, 50% more than the current Falcon heavy. Thousands of launches per year. Elon Musk predicts Falcon Heavy's $1,500/kg cost will plummet to $100 in 23 years.
In context:
People underestimate this.
2. The Benefits of Affordable Transportation
Compare Earth's transportation costs:
It's no surprise that the US and Northern Europe are the wealthiest and have the most navigable interior waterways.
So what? since sea transportation is cheaper than land. Inland waterways are even better than sea transportation since weather is less of an issue, currents can be controlled, and rivers serve two banks instead of one for coastal transportation.
In France, because population density follows river systems, rivers are valuable. Cheap transportation brought people and money to rivers, especially their confluences.
How come? Why were humans surrounding rivers?
Imagine selling meat for $10 per kilogram. Transporting one kg one kilometer costs $1. Your margin decreases $1 each kilometer. You can only ship 10 kilometers. For example, you can only trade with four cities:
If instead, your cost of transportation is half, what happens? It costs you $0.5 per km. You now have higher margins with each city you traded with. More importantly, you can reach 20-km markets.
However, 2x distance 4x surface! You can now trade with sixteen cities instead of four! Metcalfe's law states that a network's value increases with its nodes squared. Since now sixteen cities can connect to yours. Each city now has sixteen connections! They get affluent and can afford more meat.
Rivers lower travel costs, connecting many cities, which can trade more, get wealthy, and buy more.
The right network is worth at least an order of magnitude more than the left! The cheaper the transport, the more trade at a lower cost, the more income generated, the more that wealth can be reinvested in better canals, bridges, and roads, and the wealth grows even more.
Throughout history. Rome was established around cheap Mediterranean transit and preoccupied with cutting overland transportation costs with their famous roadways. Communications restricted their empire.
The Egyptians lived around the Nile, the Vikings around the North Sea, early Japan around the Seto Inland Sea, and China started canals in the 5th century BC.
Transportation costs shaped empires.Starship is lowering new-world transit expenses. What's possible?
3. Change Organizations, Change Companies, Change the World
Starship is a conveyor belt to LEO. A new world of opportunity opens up as transportation prices drop 100x in a decade.
Satellite engineers have spent decades shedding milligrams. Weight influenced every decision: pricing structure, volumes to be sent, material selections, power sources, thermal protection, guiding, navigation, and control software. Weight was everything in the mission. To pack as much science into every millimeter, NASA missions had to be miniaturized. Engineers were indoctrinated against mass.
No way.
Starship is not constrained by any space mission, robotic or crewed.
Starship obliterates the mass constraint and every last vestige of cultural baggage it has gouged into the minds of spacecraft designers. A dollar spent on mass optimization no longer buys a dollar saved on launch cost. It buys nothing. It is time to raise the scope of our ambition and think much bigger. — Casey Handmer, Starship is still not understood
A Tesla Roadster in space makes more sense.
It went beyond bad PR. It told the industry: Did you care about every microgram? No more. My rockets are big enough to send a Tesla without noticing. Industry watchers should have noticed.
Most didn’t. Artemis is a global mission to send astronauts to the Moon and build a base. Artemis uses disposable Space Launch System rockets. Instead of sending two or three dinky 10-ton crew habitats over the next decade, Starship might deliver 100x as much cargo and create a base for 1,000 astronauts in a year or two. Why not? Because Artemis remains in a pre-Starship paradigm where each kilogram costs a million dollars and we must aggressively descope our objective.
Space agencies can deliver 100x more payload to space for the same budget with 100x lower costs and 100x higher transportation volumes. How can space economy saturate this new supply?
Before Starship, NASA supplied heavy equipment for Moon base construction. After Starship, Caterpillar and Deere may space-qualify their products with little alterations. Instead than waiting decades for NASA engineers to catch up, we could send people to build a space outpost with John Deere equipment in a few years.
History is littered with the wreckage of former industrial titans that underestimated the impact of new technology and overestimated their ability to adapt: Blockbuster, Motorola, Kodak, Nokia, RIM, Xerox, Yahoo, IBM, Atari, Sears, Hitachi, Polaroid, Toshiba, HP, Palm, Sony, PanAm, Sega, Netscape, Compaq, GM… — Casey Handmer, Starship is still not understood
Everyone saw it coming, but senior management failed to realize that adaption would involve moving beyond their established business practice. Others will if they don't.
4. The Starship Possibilities
It's Starlink.
SpaceX invented affordable cargo space and grasped its implications first. How can we use all this inexpensive cargo nobody knows how to use?
Satellite communications seemed like the best way to capitalize on it. They tried. Starlink, designed by SpaceX, provides fast, dependable Internet worldwide. Beaming information down is often cheaper than cable. Already profitable.
Starlink is one use for all this cheap cargo space. Many more. The longer firms ignore the opportunity, the more SpaceX will acquire.
What are these chances?
Satellite imagery is outdated and lacks detail. We can improve greatly. Synthetic aperture radar can take beautiful shots like this:
Have you ever used Google Maps and thought, "I want to see this in more detail"? What if I could view Earth live? What if we could livestream an infrared image of Earth?
We could launch hundreds of satellites with such mind-blowing visual precision of the Earth that we would dramatically improve the accuracy of our meteorological models; our agriculture; where crime is happening; where poachers are operating in the savannah; climate change; and who is moving military personnel where. Is that useful?
What if we could see Earth in real time? That affects businesses? That changes society?

Laura Sanders
3 years ago
Xenobots, tiny living machines, can duplicate themselves.
Strange and complex behavior of frog cell blobs
A xenobot “parent,” shaped like a hungry Pac-Man (shown in red false color), created an “offspring” xenobot (green sphere) by gathering loose frog cells in its opening.
Tiny “living machines” made of frog cells can make copies of themselves. This newly discovered renewal mechanism may help create self-renewing biological machines.
According to Kirstin Petersen, an electrical and computer engineer at Cornell University who studies groups of robots, “this is an extremely exciting breakthrough.” She says self-replicating robots are a big step toward human-free systems.
Researchers described the behavior of xenobots earlier this year (SN: 3/31/21). Small clumps of skin stem cells from frog embryos knitted themselves into small spheres and started moving. Cilia, or cellular extensions, powered the xenobots around their lab dishes.
The findings are published in the Proceedings of the National Academy of Sciences on Dec. 7. The xenobots can gather loose frog cells into spheres, which then form xenobots.
The researchers call this type of movement-induced reproduction kinematic self-replication. The study's coauthor, Douglas Blackiston of Tufts University in Medford, Massachusetts, and Harvard University, says this is typical. For example, sexual reproduction requires parental sperm and egg cells. Sometimes cells split or budded off from a parent.
“This is unique,” Blackiston says. These xenobots “find loose parts in the environment and cobble them together.” This second generation of xenobots can move like their parents, Blackiston says.
The researchers discovered that spheroid xenobots could only produce one more generation before dying out. The original xenobots' shape was predicted by an artificial intelligence program, allowing for four generations of replication.
A C shape, like an openmouthed Pac-Man, was predicted to be a more efficient progenitor. When improved xenobots were let loose in a dish, they began scooping up loose cells into their gaping “mouths,” forming more sphere-shaped bots (see image below). As many as 50 cells clumped together in the opening of a parent to form a mobile offspring. A xenobot is made up of 4,000–6,000 frog cells.
Petersen likes the Xenobots' small size. “The fact that they were able to do this at such a small scale just makes it even better,” she says. Miniature xenobots could sculpt tissues for implantation or deliver therapeutics inside the body.
Beyond the xenobots' potential jobs, the research advances an important science, says study coauthor and Tufts developmental biologist Michael Levin. The science of anticipating and controlling the outcomes of complex systems, he says.
“No one could have predicted this,” Levin says. “They regularly surprise us.” Researchers can use xenobots to test the unexpected. “This is about advancing the science of being less surprised,” Levin says.

Will Lockett
3 years ago
The Unlocking Of The Ultimate Clean Energy
The company seeking 24/7 ultra-powerful solar electricity.
We're rushing to adopt low-carbon energy to prevent a self-made doomsday. We're using solar, wind, and wave energy. These low-carbon sources aren't perfect. They consume large areas of land, causing habitat loss. They don't produce power reliably, necessitating large grid-level batteries, an environmental nightmare. We can and must do better than fossil fuels. Longi, one of the world's top solar panel producers, is creating a low-carbon energy source. Solar-powered spacecraft. But how does it work? Why is it so environmentally harmonious? And how can Longi unlock it?
Space-based solar makes sense. Satellites above Medium Earth Orbit (MEO) enjoy 24/7 daylight. Outer space has no atmosphere or ozone layer to block the Sun's high-energy UV radiation. Solar panels can create more energy in space than on Earth due to these two factors. Solar panels in orbit can create 40 times more power than those on Earth, according to estimates.
How can we utilize this immense power? Launch a geostationary satellite with solar panels, then beam power to Earth. Such a technology could be our most eco-friendly energy source. (Better than fusion power!) How?
Solar panels create more energy in space, as I've said. Solar panel manufacture and grid batteries emit the most carbon. This indicates that a space-solar farm's carbon footprint (which doesn't need a battery because it's a constant power source) might be over 40 times smaller than a terrestrial one. Combine that with carbon-neutral launch vehicles like Starship, and you have a low-carbon power source. Solar power has one of the lowest emissions per kWh at 6g/kWh, so space-based solar could approach net-zero emissions.
Space solar is versatile because it doesn't require enormous infrastructure. A space-solar farm could power New York and Dallas with the same efficiency, without cables. The satellite will transmit power to a nearby terminal. This allows an energy system to evolve and adapt as the society it powers changes. Building and maintaining infrastructure can be carbon-intensive, thus less infrastructure means less emissions.
Space-based solar doesn't destroy habitats, either. Solar and wind power can be engineered to reduce habitat loss, but they still harm ecosystems, which must be restored. Space solar requires almost no land, therefore it's easier on Mother Nature.
Space solar power could be the ultimate energy source. So why haven’t we done it yet?
Well, for two reasons: the cost of launch and the efficiency of wireless energy transmission.
Advances in rocket construction and reusable rocket technology have lowered orbital launch costs. In the early 2000s, the Space Shuttle cost $60,000 per kg launched into LEO, but a SpaceX Falcon 9 costs only $3,205. 95% drop! Even at these low prices, launching a space-based solar farm is commercially questionable.
Energy transmission efficiency is half of its commercial viability. Space-based solar farms must be in geostationary orbit to get 24/7 daylight, 22,300 miles above Earth's surface. It's a long way to wirelessly transmit energy. Most laser and microwave systems are below 20% efficient.
Space-based solar power is uneconomical due to low efficiency and high deployment costs.
Longi wants to create this ultimate power. But how?
They'll send solar panels into space to develop space-based solar power that can be beamed to Earth. This mission will help them design solar panels tough enough for space while remaining efficient.
Longi is a Chinese company, and China's space program and universities are developing space-based solar power and seeking commercial partners. Xidian University has built a 98%-efficient microwave-based wireless energy transmission system for space-based solar power. The Long March 5B is China's super-cheap (but not carbon-offset) launch vehicle.
Longi fills the gap. They have the commercial know-how and ability to build solar satellites and terrestrial terminals at scale. Universities and the Chinese government have transmission technology and low-cost launch vehicles to launch this technology.
It may take a decade to develop and refine this energy solution. This could spark a clean energy revolution. Once operational, Longi and the Chinese government could offer the world a flexible, environmentally friendly, rapidly deployable energy source.
Should the world adopt this technology and let China control its energy? I'm not very political, so you decide. This seems to be the beginning of tapping into this planet-saving energy source. Forget fusion reactors. Carbon-neutral energy is coming soon.
You might also like

Tim Denning
2 years ago
In this recession, according to Mark Cuban, you need to outwork everyone
Here’s why that’s baloney
Mark Cuban popularized entrepreneurship.
Shark Tank (which made Mark famous) made starting a business glamorous to attract more entrepreneurs. First off
This isn't an anti-billionaire rant.
Mark Cuban has done excellent. He's a smart, principled businessman. I enjoy his Web3 work. But Mark's work and productivity theories are absurd.
You don't need to outwork everyone in this recession to live well.
You won't be able to outwork me.
Yuck! Mark's words made me gag.
Why do boys think working is a football game where the winner wins a Super Bowl trophy? To outwork you.
Hard work doesn't equal intelligence.
Highly clever professionals spend 4 hours a day in a flow state, then go home to relax with family.
If you don't put forth the effort, someone else will.
- Mark.
He'll burn out. He's delusional and doesn't understand productivity. Boredom or disconnection spark our best thoughts.
TikTok outlaws boredom.
In a spare minute, we check our phones because we can't stand stillness.
All this work p*rn makes things worse. When is it okay to feel again? Because I can’t feel anything when I’m drowning in work and haven’t had a holiday in 2 years.
Your rivals are actively attempting to undermine you.
Ohhh please Mark…seriously.
This isn't a Tom Hanks war film. Relax. Not everyone is a rival. Only yourself is your competitor. To survive the recession, be better than a year ago.
If you get rich, great. If not, there's more to life than Lambos and angel investments.
Some want to relax and enjoy life. No competition. We witness people with lives trying to endure the recession and record-high prices.
This fictitious rival worsens life and work.
If you are truly talented, you will motivate others to work more diligently and effectively.
No Mark. Soz.
If you're a good leader, you won't brag about working hard and treating others like cogs. Treat them like humans. You'll have EQ.
Silly statements like this are caused by an out-of-control ego. No longer watch Shark Tank.
Ego over humanity.
Good leaders will urge people to keep together during the recession. Good leaders support those who are laid off and need a reference.
Not harder, quicker, better. That created my mental health problems 10 years ago.
Truth: we want to work less.
The promotion of entrepreneurship is ludicrous.
Marvel superheroes. Seriously, relax Max.
I used to write about entrepreneurship, then I quit. Many WeWork Adam Neumanns. Carelessness.
I now utilize the side hustle title when writing about online company or entrepreneurship. Humanizes.
Stop glorifying. Thinking we'll all be Elon Musks who send rockets to Mars is delusional. Most of us won't create companies employing hundreds.
OK.
The true epidemic is glorification. fewer selfies Little birdy needs less bank account screenshots. Less Uber talk.
We're exhausted.
Fun, ego-free business can transform the world. Take a relax pill.
Work as if someone were attempting to take everything from you.
I've seen people lose everything.
Myself included. My 20s startup failed. I was almost bankrupt. I thought I'd never recover. Nope.
Best thing ever.
Losing everything reveals your true self. Unintelligent entrepreneur egos perish instantly. Regaining humility revitalizes relationships.
Money's significance shifts. Stop chasing it like a puppy with a bone.
Fearing loss is unfounded.
Here is a more effective approach than outworking nobody.
(You'll thrive in the recession and become wealthy.)
Smarter work
Overworking is donkey work.
You don't want to be a career-long overworker. Instead than wasting time, write down what you do. List tasks and processes.
Keep doing/outsource the list. Step-by-step each task. Continuously systematize.
Then recruit a digital employee like Zapier or a virtual assistant in the same country.
Intelligent, not difficult.
If your big break could burn in hell, diversify like it will.
People err by focusing on one chance.
Chances can vanish. All-in risky. Instead of working like a Mark Cuban groupie, diversify your income.
If you're employed, your customer is your employer.
Sell the same abilities twice and add 2-3 contract clients. Reduce your hours at your main job and take on more clients.
Leave brand loyalty behind
Mark desires his employees' worship.
That's stupid. When times are bad, layoffs multiply. The problem is the false belief that companies care. No. A business maximizes profit and pays you the least.
To care or overpay is anti-capitalist (that run the world). Be honest.
I was a banker. Then the bat virus hit and jobs disappeared faster than I urinate after a night of drinking.
Start being disloyal now since your company will cheerfully replace you with a better applicant. Meet recruiters and hiring managers on LinkedIn. Whenever something goes wrong at work, act.
Loyalty to self and family. Nobody.
Outwork this instead
Mark doesn't suggest outworking inflation instead of people.
Inflation erodes your time on earth. If you ignore inflation, you'll work harder for less pay every minute.
Financial literacy beats inflation.
Get a side job and earn money online
So you can stop outworking everyone.
Internet leverages time. Same effort today yields exponential results later. There are still whole places not online.
Instead of working forever, generate money online.
Final Words
Overworking is stupid. Don't listen to wealthy football jocks.
Work isn't everything. Prioritize diversification, internet income streams, boredom, and financial knowledge throughout the recession.
That’s how to get wealthy rather than burnout-rich.

Jari Roomer
2 years ago
Three Simple Daily Practices That Will Immediately Double Your Output
Most productive people are habitual.
Early in the day, do important tasks.
In his best-selling book Eat That Frog, Brian Tracy advised starting the day with your hardest, most important activity.
Most individuals work best in the morning. Energy and willpower peak then.
Mornings are also ideal for memory, focus, and problem-solving.
Thus, the morning is ideal for your hardest chores.
It makes sense to do these things during your peak performance hours.
Additionally, your morning sets the tone for the day. According to Brian Tracy, the first hour of the workday steers the remainder.
After doing your most critical chores, you may feel accomplished, confident, and motivated for the remainder of the day, which boosts productivity.
Develop Your Essentialism
In Essentialism, Greg McKeown claims that trying to be everything to everyone leads to mediocrity and tiredness.
You'll either burn out, be spread too thin, or compromise your ideals.
Greg McKeown advises Essentialism:
Clarify what’s truly important in your life and eliminate the rest.
Eliminating non-essential duties, activities, and commitments frees up time and energy for what matters most.
According to Greg McKeown, Essentialists live by design, not default.
You'll be happier and more productive if you follow your essentials.
Follow these three steps to live more essentialist.
Prioritize Your Tasks First
What matters most clarifies what matters less. List your most significant aims and values.
The clearer your priorities, the more you can focus on them.
On Essentialism, McKeown wrote, The ultimate form of effectiveness is the ability to deliberately invest our time and energy in the few things that matter most.
#2: Set Your Priorities in Order
Prioritize your priorities, not simply know them.
“If you don’t prioritize your life, someone else will.” — Greg McKeown
Planning each day and allocating enough time for your priorities is the best method to become more purposeful.
#3: Practice saying "no"
If a request or demand conflicts with your aims or principles, you must learn to say no.
Saying no frees up space for our priorities.
Place Sleep Above All Else
Many believe they must forego sleep to be more productive. This is false.
A productive day starts with a good night's sleep.
Matthew Walker (Why We Sleep) says:
“Getting a good night’s sleep can improve cognitive performance, creativity, and overall productivity.”
Sleep helps us learn, remember, and repair.
Unfortunately, 35% of people don't receive the recommended 79 hours of sleep per night.
Sleep deprivation can cause:
increased risk of diabetes, heart disease, stroke, and obesity
Depression, stress, and anxiety risk are all on the rise.
decrease in general contentment
decline in cognitive function
To live an ideal, productive, and healthy life, you must prioritize sleep.
Follow these six sleep optimization strategies to obtain enough sleep:
Establish a nightly ritual to relax and prepare for sleep.
Avoid using screens an hour before bed because the blue light they emit disrupts the generation of melatonin, a necessary hormone for sleep.
Maintain a regular sleep schedule to control your body's biological clock (and optimizes melatonin production)
Create a peaceful, dark, and cool sleeping environment.
Limit your intake of sweets and caffeine (especially in the hours leading up to bedtime)
Regular exercise (but not right before you go to bed, because your body temperature will be too high)
Sleep is one of the best ways to boost productivity.
Sleep is crucial, says Matthew Walker. It's the key to good health and longevity.

Clive Thompson
2 years ago
Small Pieces of Code That Revolutionized the World
Few sentences can have global significance.
Ethan Zuckerman invented the pop-up commercial in 1997.
He was working for Tripod.com, an online service that let people make little web pages for free. Tripod offered advertising to make money. Advertisers didn't enjoy seeing their advertising next to filthy content, like a user's anal sex website.
Zuckerman's boss wanted a solution. Wasn't there a way to move the ads away from user-generated content?
When you visited a Tripod page, a pop-up ad page appeared. So, the ad isn't officially tied to any user page. It'd float onscreen.
Here’s the thing, though: Zuckerman’s bit of Javascript, that created the popup ad? It was incredibly short — a single line of code:
window.open('http://tripod.com/navbar.html'
"width=200, height=400, toolbar=no, scrollbars=no, resizable=no, target=_top");Javascript tells the browser to open a 200-by-400-pixel window on top of any other open web pages, without a scrollbar or toolbar.
Simple yet harmful! Soon, commercial websites mimicked Zuckerman's concept, infesting the Internet with pop-up advertising. In the early 2000s, a coder for a download site told me that most of their revenue came from porn pop-up ads.
Pop-up advertising are everywhere. You despise them. Hopefully, your browser blocks them.
Zuckerman wrote a single line of code that made the world worse.
I read Zuckerman's story in How 26 Lines of Code Changed the World. Torie Bosch compiled a humorous anthology of short writings about code that tipped the world.
Most of these samples are quite short. Pop-cultural preconceptions about coding say that important code is vast and expansive. Hollywood depicts programmers as blurs spouting out Niagaras of code. Google's success was formerly attributed to its 2 billion lines of code.
It's usually not true. Google's original breakthrough, the piece of code that propelled Google above its search-engine counterparts, was its PageRank algorithm, which determined a web page's value based on how many other pages connected to it and the quality of those connecting pages. People have written their own Python versions; it's only a few dozen lines.
Google's operations, like any large tech company's, comprise thousands of procedures. So their code base grows. The most impactful code can be brief.
The examples are fascinating and wide-ranging, so read the whole book (or give it to nerds as a present). Charlton McIlwain wrote a chapter on the police beat algorithm developed in the late 1960s to anticipate crime hotspots so law enforcement could dispatch more officers there. It created a racial feedback loop. Since poor Black neighborhoods were already overpoliced compared to white ones, the algorithm directed more policing there, resulting in more arrests, which convinced it to send more police; rinse and repeat.
Kelly Chudler's You Are Not Expected To Understand This depicts the police-beat algorithm.
Even shorter code changed the world: the tracking pixel.
Lily Hay Newman's chapter on monitoring pixels says you probably interact with this code every day. It's a snippet of HTML that embeds a single tiny pixel in an email. Getting an email with a tracking code spies on me. As follows: My browser requests the single-pixel image as soon as I open the mail. My email sender checks to see if Clives browser has requested that pixel. My email sender can tell when I open it.
Adding a tracking pixel to an email is easy:
<img src="URL LINKING TO THE PIXEL ONLINE" width="0" height="0">An older example: Ellen R. Stofan and Nick Partridge wrote a chapter on Apollo 11's lunar module bailout code. This bailout code operated on the lunar module's tiny on-board computer and was designed to prioritize: If the computer grew overloaded, it would discard all but the most vital work.
When the lunar module approached the moon, the computer became overloaded. The bailout code shut down anything non-essential to landing the module. It shut down certain lunar module display systems, scaring the astronauts. Module landed safely.
22-line code
POODOO INHINT
CA Q
TS ALMCADR
TC BANKCALL
CADR VAC5STOR # STORE ERASABLES FOR DEBUGGING PURPOSES.
INDEX ALMCADR
CAF 0
ABORT2 TC BORTENT
OCT77770 OCT 77770 # DONT MOVE
CA V37FLBIT # IS AVERAGE G ON
MASK FLAGWRD7
CCS A
TC WHIMPER -1 # YES. DONT DO POODOO. DO BAILOUT.
TC DOWNFLAG
ADRES STATEFLG
TC DOWNFLAG
ADRES REINTFLG
TC DOWNFLAG
ADRES NODOFLAG
TC BANKCALL
CADR MR.KLEAN
TC WHIMPERThis fun book is worth reading.
I'm a contributor to the New York Times Magazine, Wired, and Mother Jones. I've also written Coders: The Making of a New Tribe and the Remaking of the World and Smarter Than You Think: How Technology is Changing Our Minds. Twitter and Instagram: @pomeranian99; Mastodon: @clive@saturation.social.
