Inverse Daily

The refractory period, explained

If you've got a penis, you can't have sex back-to-back. Science is figuring out why.

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After the collapse of the Soviet Union in 1991, there was global concern over what would become of the Soviet space program. Among the many concerns was Mir, the Soviet space station operating in low Earth orbit. Always somewhat cramped, the economic chaos of the USSR's collapse made running the station independently an impossible task. The United States agreed to partner with the Russian government on the program.

Amidst all this political chaos, on this day, Russian cosmonaut Valeri Polyakov began to make history. The cosmonaut had first been inspired by his countryman Yuri Gagarin's historic spaceflight in 1961, got his medical degree in 1965, and soon began specializing in space medicine. He went for his first trip to Mir in 1988, staying for an incredible 240 days. But that was nothing compared to what was coming in 1994.

Starting today in 1994, Valeri Polyakov began his epic 437-day stay on Mir. He volunteered for the mission, hoping to better understand how microgravity would affect the human body over an extended period of time. More specifically, the study looked at blood chemistry and volume, the circulatory system, the central nervous system, bone density, and his mental state. Polyakov worked out for two hours each day and underwent 29 psychological evaluations during his time on Mir.

While he underwent some difficult periods during this intense time, scientists would go on to describe Polyakov as having "an impressive stability of mood and performance during the second to 14th month in space."

As for Polyakov, he came into the mission with one goal in mind: "I had to show that it is possible to preserve your ability to function after being in space for such a long time. But the gravity on Mars is .37. And since I was able to stand up and walk on the Earth wearing a space suit, it shows that [a] human is able, will be able to stand up and walk on Mars."

Our question of the week: Do you have any tech-related resolutions? Maybe you're going to finally download that foreign language app or stop doomscrolling. We'd love to hear what you're trying to do with tech this year! Shoot us an email at and we'll highlight some of our favorites!

As for our last question asking about your 2021 We were overwhelmed with amazing responses. Thank you so much! We've published a few of them below and are going to work up a post soon highlighting others. Although we do have to say, we hope not all of these come true.

This is an adapted version of the Inverse Daily newsletter for January 8, 2021. Subscribe for free and earn rewards for reading every day in your inbox.

Stargazing — SpaceX Starship: Watch the SN9 prototype fire its engines ahead of launch

The Starship, SpaceX's in-development ship designed to send humans to Mars and beyond, is about to take on its biggest challenge yet.

On Wednesday, the "SN9" prototype of the ship successfully completed a static test fire ahead of a planned test launch. These firings, a regular feature of rocket launches, hold the rocket down as it fires its engines to test the on-board systems. reported the firing was completed at 5:07 p.m. Eastern time at the Boca Chica facilities in Texas.

When is SN9 flying for real?

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Cosmic navigation — NASA is updating its "space GPS" system before going to the Moon

The Moon may be Earth's closest natural satellite, but that doesn't mean that it's easy to get to. It takes about three days to make the 238,900-mile journey to the Moon, traveling through the depths of space.

As NASA prepares for its upcoming Artemis mission, which will return humans to the lunar surface for the first time in over 50 years, the space agency needs to upgrade its navigation system to make for a smoother ride in the cosmic void.

How will Artemis aim for the Moon?

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Origin story — Why early human eating habits led to dog domestication

Humans love dogs. We talk to them like babies. We literally spend billions on their Halloween costumes. We smother them with so much love, they get chubby from all the extra treats.

But there was one time when wolves — the ancestors of dogs — and humans were more adversaries than friends. Yet, at some point, wolves became domesticated into pets.

Pet lovers and scientists have wondered: Exactly how did ancient dogs become domesticated?

A new study published in the journal Nature may have the answer to that long-standing question — and it has to do with Arctic humans' eating habits near the end of the last Ice Age, nearly 14,000 to 29,000 years ago.

Inverse author Tara Yarlagadda tells me: "It's a really interesting question to ponder: How on Earth did we manage to domesticate fierce wolves into docile dogs? This study provides an innovative answer to that question by looking at what ancient humans ate, which previous research hasn't really tackled."

The answer could be food

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Coming soon ...

2020 is in the history books. Of course, we remember the year as being defined by the pandemic. But how long will our memories last? Will we slowly return to normal life and forget this ever happened bar the footnote in history it will occupy? It seems hard to imagine until you stop and ask yourself when the last time you thought about the Spanish Flu before 2020 was. Coming soon on Inverse, a look at how Covid-19 could change our cultural consciousness.

Recycle, reduce, reuse, robot — Robot that sorts recycling twice as fast as a human may change the world

You might want to rethink that congratulatory pat-on-the-back you give yourself when choosing to recycle instead of trash your venti Starbucks cup.

Recent studies have found that up to 79 percent of plastic waste created in the US goes to landfills instead of being recycled.

Yes, even the plastic that makes it to recycling centers is not always recycled.

This shocking discrepancy stems in part from the tedious and tiring labor that is typically required to manually sort tons of recycling that centers receive daily. During the pandemic, this volume increased, while the availability of workers decreased due to sickness or safety concerns.

This is a problem that AMP Robotics, a company founded in 2014 by CalTech Ph.D. Matanya Horowitz, plans to solve. Using computer vision and machine learning, AMP Robotics has designed an intelligent three-handed robot that can analyze and sort 80 items of recycling per minute — a rate that is twice as fast as human sorters. The company recently closed a $55 million funding round, bringing its total funding close to $75 million.

Matanya Horowitz, founder and CEO of AMP Robotics, tells Inverse that, "globally, more than $200 billion worth of recyclable materials goes unrecovered annually. A.I.-driven automation enables the efficient recovery of more material, which increases recycling rates and reduces human impact on the environment."

How the three Rs could be adding a fourth

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Private parts — Ejaculation study debunks a long-standing theory about the refractory period

Scientists are still lacking hard data on how long it takes men to recharge after sex. But for years, they thought they at least had an explanation for why the downtime was needed.

Now, it may be time to retire the existing explanation for why back-to-back ejaculations are a biological struggle.

The prevailing explanation for the “post-ejaculation refractory period” (the idea that post-orgasm, men have to wait before becoming aroused again) centered around a hormone called prolactin. Prolactin is perhaps most famous for sparking milk production in females during pregnancy, but it also has deep ties to orgasms (usually accompanied by ejaculation, but not always).

High levels of prolactin have been linked to low sexual desire. Studies have also shown that prolactin spikes during ejaculation and orgasm, suggesting it’s that hormone causing the body to demand a break afterward. One notable exception stems from a case study covering a man who was able to orgasm repeatedly. In one trial, he only needed two minutes between orgasms. He also didn’t have a typical post-release prolactin surge seen in the control group.

But past research may have sent scientists in the wrong direction, explains Susana Lima, the first author of a new study published this week in Communications Biology. Lima is a researcher at the Champalimaud Research Center for the Unknown, a private biomedical research institution.

In a study on two types of mice, she found that messing with prolactin levels showed no effect on the male refractory period.

“This means, it was just correlation," Lima tells Inverse. "Causation was never tested."

What does prolactin have to do with sex?

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Our 2021 predictions of the day:

"Discovery of biological microorganisms (say, microbes) in the near/sub surface of Mars by Perseverance rover!" — Ilan Elavarasan

"2021 will see the mass vaccinations taking longer than expected to reduce the Covid pandemic as idiots still refuse to mask up and distance themselves socially." — Samuel Donovan

"In the year 2021, the world began to exhale." — Karen Florio

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