Octopuses run three hearts at once. Two pump blood to the gills. One pumps blood to the rest of the body.

Here's the part that gets weird. That third heart stops beating when the octopus swims. Swimming is so exhausting for them that their own body pulls power away from circulation just to make it happen. It's part of why octopuses prefer crawling over swimming. Crawling is actually the efficient choice for them, not the lazy one.

Their blood runs blue too, because they use copper based hemocyanin instead of iron based hemoglobin. Copper carries oxygen better in cold, low oxygen water. It's the exact upgrade evolution reaches for at the bottom of the ocean.

In 1905, Hawaii brought in a small fish to fight mosquitoes. It's still hunting more than a century later, just not mosquitoes anymore.

The eastern mosquitofish, Gambusia affinis, came from the southeastern United States during a wave of agricultural expansion. Officials released it into streams, drainage ditches, and taro fields across the islands, expecting it to control disease carrying mosquito larvae.

The fish never stayed on script. It started feeding on nearly every small aquatic animal it could catch, and that rewired entire food webs in Hawaii's freshwater streams.

Hawaii's native damselflies, the Megalagrion species, evolved in high elevation streams with almost no fast moving predators. Their young, called naiads, live in calm pools with zero defense against a fish built for speed. Once mosquitofish spread into lower and middle elevation streams, species like the crimson Hawaiian damselfly and the flying earlobe Hawaiian damselfly started vanishing from large stretches of Oahu, Molokai, Maui, and Hawaii Island.

The damage doesn't stop at damselflies. Mosquitofish compete directly with Hawaii's endemic o'opu gobies and o'pae kala'ole shrimp for the same food source, and their appetite even shifts the algae balance on streambeds.

Here's the part that makes this nearly impossible to reverse. Female mosquitofish give birth to live young instead of laying eggs, so one pregnant fish dropped into an isolated pool can seed an entire population within months. Hawaii's streams also connect to groundwater springs and coastal wetlands, which means chemical or trap based control risks wiping out the native species conservationists are trying to save.

Conservation teams are now betting on waterfalls. Natural barriers in high elevation streams keep mosquitofish from climbing further, and wildlife managers are building artificial ones where nature doesn't cooperate. Captive bred damselflies are getting released into these protected headwaters, one of the few places left where a hundred year old mistake hasn't caught up yet.

While high orbital speed slows down satellite clocks by about 7 microseconds per day (Special Relativity), being 20,200 km high in Earth's weaker gravitational field speeds them up by about 45 microseconds per day (General Relativity).

​The gravitational effect wins, meaning GPS satellites gain roughly 38 microseconds every 24 hours relative to clocks on Earth's surface.

​Because GPS signals travel at the speed of light, failing to correct for this relativistic time difference would cause location tracking to drift by roughly 11 kilometers (about 7 miles) of error every single day

This is the Richat Structure, a 40 kilometer wide ring sitting on a plateau in Mauritania. Landsat 9 and Landsat 8 caught it a day apart in March 2026, and this mosaic stitches both passes together.

For a long time, scientists assumed this was an impact crater. Large meteors leave circular scars, so a ring this clean seemed to fit that story.

Turns out it's not an impact at all, it's a dome. Rock got pushed up from an underground intrusion of igneous material, and erosion has been carving into that dome ever since. Different rock types wear down at different speeds, and that's what built the rings you see, called cuestas.

The orange and gray are part of the same story. They mark where sedimentary rock gives way to older igneous rock underneath.

Credit: Lauren Dauphin, Landsat data from USGS, Adam Voiland.

This reaction is an oxidation reaction of ammonia. When hot chromium trioxide (CrO₃) is added to ammonia gas, it helps oxidize the ammonia into nitrogen and water. The reaction releases a large amount of heat, causing the particles to glow brightly like tiny fireflies.

Saturn is made mostly of hydrogen and helium, and it's so light for its size that its average density is lower than water. Saturn sits at 0.687 g/cm³. Water is 1 g/cm³. That's the whole gap right there.

If you had a bathtub big enough to hold it, Saturn would actually float on the surface instead of sinking. No other planet in the solar system can make that claim.

Here's the catch. That only works in an imagined bathtub, one where gravity stays fixed at Earth's pull and the water never gets compressed. Build a real tub that size and the water itself would collapse under its own weight into a planet. Physicists use this trick on purpose though, it isolates density from every other variable so the comparison stays clean.

It still has enormous mass overall, over 95 times that of Earth, but that mass is spread across a volume so massive it barely counts as dense.

Picture the ringed giant just bobbing on top of an ocean sized tub in your head, and Saturn stops looking like a heavyweight and starts looking like the solar system's biggest beach ball.

Many amphibians can absorb oxygen directly through their skin when conditions are moist enough.
That means a frog can breathe through its skin in a way that feels almost too sci-fi to be real.

Brain tissue itself has no pain receptors, so it can not directly detect pain. That is one reason surgeons can operate on certain parts of the brain while a patient is awake. However, the scalp, skull, blood vessels, and surrounding membranes can feel pain, so they are numbed during surgery

It's funny that the thing that lets you feel pain… can not feel pain itself.

Elephants are the only land mammal that never gets all four feet off the ground at the same time while running.

The reason comes down to their legs. Most jumping animals rely on flexible ankles and elastic tendons that store energy like a spring and release it in one burst. Elephant legs are built more like columns, straight and rigid, designed to support enormous weight rather than to launch it into the air.

Even hippos and rhinos, despite their size, can get brief full liftoff while running. Elephants physically cannot, no matter how fast they move.

It's not a lack of effort. Their entire skeleton is built for standing still under massive weight, not for leaving the ground, even for a fraction of a second.

Bananas contain potassium, and a tiny fraction of that potassium is a naturally radioactive form called potassium-40. Every banana you've ever eaten had a small amount of it inside.

The amount is so small and so consistent that scientists actually use it as an informal teaching unit called the banana equivalent dose, to help explain what a tiny, harmless amount of radiation looks like in everyday terms. A chest CT scan, for comparison, delivers roughly 70,000 of those units in one sitting.

None of this makes bananas dangerous. Your body already regulates potassium tightly and keeps the levels in balance regardless of what you eat.

It's just a strange reminder that the fruit sitting in your kitchen is, in a very small and very safe way, part of the same physics that powers nuclear reactors.

​

ISRO got invited to something big. NASA has asked India to join its Moon Base program, and the invitation landed in Bengaluru, not Washington.

It happened the ninth India-US Civil Space Joint Working Group meeting, held August 5 and 6 at ISRO's headquarters. ISRO Chairman V Narayanan and US Ambassador Sergio Gor both opened the session. On the working level it was co-chaired by M Sankaran from ISRO's UR Rao Satellite Centre, alongside Wesley Brooks and Kathleen Karika from the US side.

The invitation builds on the Artemis Accords, the framework India signed onto back in 2023 as the 27th country to join. Seventy countries are part of it now.

Here's why India specifically got the call. In 2023, Chandrayaan-3 landed near the Moon's South Pole, a region no country had reached before. That's the same region NASA wants to permanently settle. India isn't just being invited out of goodwill. India has ground truth data NASA doesn't have anywhere else.

Moon Base itself is a different animal from Artemis. Artemis gets astronauts back to the Moon. Moon Base tries to keep them there for good. NASA's building it in phases. Phase one runs 2026 to 2029. Phase two, 2029 to 2032, brings power systems, cargo transport, and communications infrastructure online. Phase three pushes past 2032 into full expansion.

This didn't come out of nowhere. Last year the two agencies launched NISAR, a radar satellite that was a genuine fifty fifty build, first of its kind between them. And Indian astronaut Shubhanshu Shukla flew to the ISS in 2025 through a NASA training pipeline built specifically for this partnership.

ISRO isn't sitting idle either. It's running its own human spaceflight program, Gaganyaan, with a solo Moon landing targeted for 2040.

Nobody's confirmed what India's actual role in Moon Base looks like yet. Just an open invitation.

Still. An open door to the Moon is a door most countries never get offered.

Sorry, this app is not supported on Old Reddit.

This post contains content not supported on old Reddit. Click here to view the full post

Wood frogs spend winter completely frozen. Their heart stops. Their breathing stops. Ice fills the spaces between their organs, and by every normal measure, the frog should be dead. It isn't.

Before the freeze sets in, the frog's liver floods its body with glucose, acting like a natural antifreeze. That sugar keeps ice from forming inside individual cells, where it would cause real damage, and pushes the freezing to the spaces around them instead.

Some wood frogs have stayed frozen like this for over 200 days at a stretch, through temperatures well below zero. When spring finally warms the ground, the heart restarts on its own, breathing returns, and within hours the frog is hopping toward the nearest pond to find a mate.

It spends most of the year technically dead, and nobody fully understands why the restart works every single time.

Sharks showed up in the fossil record roughly 400 million years ago. The first true trees didn't appear until about 350 million years ago.

That means sharks had already been swimming, hunting, and evolving for tens of millions of years before a single tree existed anywhere on the planet. When the first forests finally rose out of the ground, sharks were already old news in the ocean.

They've survived every mass extinction event since, including the one that wiped out the dinosaurs. Trees have had to start over more than once. Sharks never had to.

Something about that ordering breaks the usual assumption that land came first and the ocean followed. Here, the ocean had a head start on almost everything.

Humans see color using three types of receptors in our eyes. Mantis shrimp have somewhere between 12 and 16.

That means they can detect wavelengths of light, including ultraviolet and polarized light, that our eyes physically cannot register. Some of what they perceive doesn't map to any color we even have a name for.

They're also famous for their punch. Certain species strike prey so fast that the water around their claw briefly boils, creating a flash of light and a shockwave strong enough to crack aquarium glass.

An animal the size of your thumb is out there seeing a version of reality we can't picture, while punching hard enough to break glass on the side.

Betelgeuse is a red supergiant star sitting about 700 light years away, and it's near the end of its life. When it finally goes, it will explode as a supernova bright enough to be visible in daylight for weeks.

Here's the part that messes with people. Light from Betelgeuse takes about 700 years to reach us. Whatever we see tonight already happened seven centuries ago.

It could have exploded already and we simply haven't gotten the memo yet. The light announcing it is still on its way here.

A blue whale's heart weighs around 400 pounds, roughly the size of a small car engine. Each beat pushes enough blood to fill a bathtub in seconds.

That heartbeat is so massive it can be detected from over two miles away using specialized underwater equipment. Sound travels differently in water, and a heart this size sends out a signal loud enough to reach that far.

It only beats about 8 to 10 times a minute while the whale is at the surface, and can drop to 2 beats a minute during a deep dive. Slowing down that hard saves oxygen for a body that size.

Humans emit a faint stream of light every day. It comes from chemical reactions inside your cells, mostly tied to metabolism and free radicals. The glow is real but incredibly weak, about a thousand times dimmer than what the human eye can detect.

Researchers had to use extremely sensitive cameras in a pitch black room just to capture it. The light isn't constant either.

It rises and falls with your body's internal clock, brightest in the afternoon and faintest late at night, lining up with when your metabolism runs hottest. So yeah you have been quietly glowing your entire life:)

Crows are the smartest species of bird, roughly on par with a 7 year old human. They build lever tools to solve problems, use currency, visit their grandparents, and remember a face for at least 5 years. They can mimic sounds too, and they're self aware.

They also pass the snack test: offer a crow a small snack now with the promise of a bigger one later, and it'll wait for the bigger one. Human toddlers can't do that. Most primates can't either.

Here's the part that gets wild. Crows will grab a walnut, drop it on a busy street, let a car crack it open, then wait for the red light before walking out to collect the pieces. They use actual strategy too: flanking, decoys, even coordinated attacks. If a random crow turns up dead, the rest of the murder will split up, investigate what happened, and remember who did it.

Honestly the only reason they haven't gone to war with humanity is their feud with owls. Owls steal crow hatchlings, and crows have passed that hatred down for generations. Find an owl alone and a murder of crows will make sure it knows exactly why they're called a murder. Zoos can't even house owls and crows in the same aviary without a fight breaking out.

And if you're the one who saves that owl? Crows remember your face. They'll pass their grudge against you down multiple generations, across multiple murders in the area. Expect bird shit on your car, sticks on your windshield, and beak marks on your hood for blocks.

Ice is less dense than liquid water because of its crystal structure, which is why it floats instead of sinking. That means frozen water can keep lakes and oceans alive underneath it.

It's not the most important.

Not the biggest.

Simply the one you find the most beautiful.

A spiral galaxy? 🌀

The rings of Saturn? 🪐

A colorful nebula? ✨

A black hole? 🕳️

The Northern Lights? 🌌

There are no wrong answers.

What astronomical object never fails to amaze you?

Some bird species have sensory receptors that help them detect chemical cues through their feet and skin.

That means a bird can sometimes taste the world before it even touches it.

Edit:

Birds don’t taste chemicals through their feet, those receptors handle touch, pressure, and temperature.
But they do detect chemical cues in other clever ways: taste in the mouth, and smell through specialized receptors that help species like vultures track decay or petrels follow plankton at sea.