Tardigrades are microscopic eight-legged animals that have been to outer space and would likely survive the apocalypse(the end of the world). Bonus: They look like adorable (lovable) miniature bears.
Around 1,300 species of tardigrades are found worldwide. Considered aquatic because they require a thin layer of water around their bodies to prevent dehydration, they’ve also been observed in all kinds of environments, from the deep sea to sand dunes. Freshwater mosses and lichens are their preferred habitat (place they live), therefore their nickname, moss piglet.
Despite looking squishy(very soft), tardigrades are covered in a tough cuticle, similar to the exoskeletons of grasshoppers, praying mantises, and other insects to which they are related. Like those insects, tardigrades have to shed their cuticles in order to grow. They have four to six claws on each foot, which helps them cling to plant matter, and a specialized mouthpart called a bucco pharyngeal apparatus, which allows them to suck nutrients from plants and microorganisms.
Tiny and tough
Tardigrades belong to an elite category of animals known as extremophiles, or critters (animals) that can survive environments that most others can't. For instance, tardigrades can go up to 30 years without food or water. They can also live at temperatures as cold as absolute zero (-273.15 degrees Celsius) or above boiling (100 degrees Celsius), at pressures six times that of the ocean’s deepest trenches, and in the vacuum of space.
Another amazing survival trick is cryptobiosis, a state of inactivity triggered by a dry environment. The micro-animals squeeze all the water out of their bodies, retract (pull in)their heads and limbs(legs), roll up into a little ball, and become dormant(having normal physical functions suspended or slowed down for a period of time; as if in a deep sleep). When conditions improve, they unfurl (unroll) themselves and go about their business(live normally).
Mating and reproduction
Naturally, tardigrades have unusual mating habits, too. Depending on the species, the animals may reproduce asexually (without having sex) or sexually. In some species, males deposit sperm inside the cuticle of a molting, egg-carrying female during an hour-long mating process. Some females shed their cuticle and then lay their eggs inside to be fertilized later by males.
Eggs take around 40 days to hatch, or as long as 90 days if they’ve been in a desiccated (very dry) state.
DID YOU KNOW
Tardigrades have been on earth about 600 million years, preceding the dinosaurs by about 400 million years.
The Israeli spacecraft Beresheet was carrying thousands of tardigrades when it crash-landed on the moon in April 2019. Later experiments show the animals likely died on impact.
swindler - a criminal who tricks people and takes their money
weaver - someone who makes cloth
loom - a machine for making cloth
fabric - cloth
invisible - if something is invisible, you can't see it
This is a fairy story written about 200 years ago by the famous author Hans Christian Anderson. Anderson was from Denmark. His most well-known story is the Little Mermaid, which has been made into a movie.
Many years ago, there was an Emperor who loved new clothes so much that he spent all his money on being well dressed. He didn't care about ordering his soldiers to get into lines so that he could walk around and look at them, or going to the theatre, or going for a ride in his carriage, except to show off his new clothes.
He had a coat for every hour of the day, and instead of saying, as people might, about any other emperor, "The Emperor is having a meeting about important matters," here they always said, "The Emperor's in his dressing room, looking at himself in the mirror."
In the great city where he lived, life was always bright and happy. Every day many strangers came to town, and among them one day came two swindlers, criminals who liked to trick people into giving them money. They lied to get money.
The swindlers laughing about fooling the Emperor
These swindlers told people that they were weavers, makers of beautiful clothes, and they said they could weave the best fabrics imaginable. They told the Emperor that not only were their colors and patterns very nice, but clothes made of this cloth had a wonderful way of becoming invisible to anyone who could not do his job, or who was unusually stupid. These people would not be able to see the weavers' cloth.
A loom used to make cloth
They set up two looms and pretended to weave, though there was nothing on the looms. All the finest silk and the purest gold thread which they demanded from the Emperor they kept for themselves. They put the silk and gold thread into their traveling bags so that they could make money with it later, while they worked the empty looms far into the night.
"I'd like to know what those weavers are doing with the cloth," the Emperor thought, but he felt slightly uncomfortable when he remembered that those who were not good enough to do their jobs would not be able to see the cloth. It couldn't have been that he doubted himself, but he thought he'd rather send someone else to see how things were going. The whole town believed that the cloth had a strange power, and everybody wanted to find out how stupid their neighbors were.
"I'll send my honest old minister to the weavers," the Emperor decided. "He'll be the best one to tell me if the cloth is good, for he's a smart man who is the best at his job." So the honest old minister went to the room where the two swindlers sat working away at their empty looms.
"Oh no!" he thought as his eyes opened very wide, "I can't see anything at all". But he did not say so.
Both the swindlers asked him to come near to approve the excellent pattern and the beautiful colors. They pointed to the empty looms, and the poor old minister stared as hard as he could. He couldn't see anything, because there was nothing to see. H thought, "Can it be that I'm a fool? I'd have never guessed it, and nobody must know. If I can't see the cloth, does that mean that I am no good at my government job? It would be bad to say that I can't see the cloth."
"Please tell us what you think of the cloth," said one of the swindlers.
"Oh, it's beautiful - it's enchanting." The old minister peered through his spectacles. "Such a pattern, what colors!" I'll be sure to tell the Emperor how very happy I am with it."
"We're pleased to hear that," the swindlers said. They proceeded to name all the colors and to explain the pattern. The old minister paid the closest attention, so that he could tell it all to the Emperor. And so he did.
The swindlers at once asked for more money, more silk and gold thread, to continue with the weaving. But they kept it all for themselves and did not make any cloth. Not a thread went into the looms, though they worked at their weaving as hard as ever.
The Emperor soon sent another trustworthy official to see how the work was going and how soon it would be ready. The same thing happened to him that had happened to the minister. He looked and he looked, but as there was no cloth to see in the looms, he couldn't see anything.
"Isn't it a beautiful piece of cloth?" the swindlers asked him, as they displayed and described their imaginary pattern.
"I know I'm not stupid," the man thought, "so it must be that I'm unworthy of my good office. That's strange. I mustn't let anyone find it out, though." So he praised the material he did not see. He declared he was delighted (very happy) with the beautiful colors and the lovely pattern. To the Emperor he said, "I liked the cloth so much, I looked at it a long time."
All the town was talking of this really nice cloth, and the Emperor wanted to see it for himself while it was still in the looms. Attended by a group of his men, among whom were his two old trusted officials -- the ones who had been to the weavers --he set out to see the two swindlers. He found them busy weaving, but without a thread in their looms.
"Great!" said the two officials. "Just look, Your Majesty, what colors! What a design!", they said to the Emperor. They pointed to the empty looms, each thinking that the others could see the stuff.
"What's this?" thought the Emperor. "I can't see anything. This is terrible! Am I a fool? Am I not good enough to be the Emperor? What a thing to happen to me!"
"Oh! It's very pretty," he said. "It has my highest approval." And he nodded approval at the empty loom. Nothing could make him say that he couldn't see anything.
His officials stared and stared. None of them saw any cloth, but they all joined the Emperor in loudly saying, "Oh! It's very pretty," and they advised him to wear clothes made of this wonderful cloth especially for the great parade he was soon to lead. "Magnificent! Excellent! Unsurpassed!" all the people said, and everyone did their best to seem well pleased. The Emperor gave each of the swindlers an award.
Before the procession, the swindlers sat up all night pretending to finish the Emperor's new clothes. They acted as if they were taking the cloth off the loom. They made cuts in the air with huge scissors. And at last they said, "Now the Emperor's new clothes are ready for him."
Then the Emperor himself came with his noblest noblemen, and the swindlers each raised an arm as if they were holding something. They said, "These are the trousers, here's the coat, and this is the long cape," naming each piece of clothing. "All of them are as light as a spider web. One would almost think he had nothing on, but that's what makes them so fine."
"Exactly," all the noblemen agreed, though they could see nothing, for there was nothing to see.
"If Your Imperial Majesty will be nice enough to take your clothes off," said the swindlers, "we will help you on with your new ones here in front of the long mirror."
The Emperor undressed, and the swindlers pretended to put his new clothes on him, one garment after another. They took him around the waist and seemed to be fastening something as the Emperor turned round and round before the looking glass.
"How well Your Majesty's new clothes look." He heard all the people saying, "That pattern, so perfect! Those colors, so suitable! It is a magnificent outfit."
Then the minister of parades announced: "Your Majesty's canopy is waiting outside."
"Well, I'm supposed to be ready," the Emperor said, and turned again for one last look in the mirror. "It is a remarkable fit, isn't it?" He seemed to look at his costume with the greatest interest.
The noblemen bent low and reached for the floor as if they were picking up his long cape. Then they pretended to lift and hold it high. They didn't dare admit they had nothing to hold.
So off went the Emperor in procession under his splendid canopy. Everyone in the streets and the windows said, "Oh, how fine are the Emperor's new clothes! Don't they fit him to perfection? And see his long cape!"
Nobody would confess that he couldn't see any clothes on the Emperor, for that would prove him either unfit for his position, or a fool. No costume the Emperor had worn before was ever such a complete success.
"But he hasn't got anything on," a little child said.
And one person whispered to another what the child had said, "The Emperor isn't wearing clothes. A child says he hasn't anything on."
"But he isn't wearing anything!" all the people town said loudly at last.
The Emperor shook, for he thought they were right. But he thought, "This parade has got to go on." So he walked more proudly than ever, as his noblemen held high the long cape that wasn't there at all.
Elephants Were Used in Wars for Thousands of Years!
For thousands of years, animals have been used in war. As recently as World War Two (1939 to 1945), some countries such as Germany and Russia used hundreds of thousands of horses in addition to tanks, planes and trucks! Even dogs and birds have been used in war.
A German cannon being pulled by horses in World War Two.
Later, German horses would suffer greatly during the terrible Russian winter.
A war elephant is an elephant that is trained and guided by humans for fighting enemy armies. A wild elephant would be captured and training it would usually involved hurting it as well as rewarding it until it obeyed its rider's commands.
Elephants started to be used in battles about 2,500 years ago. The war elephant's main use was to charge (run towards) the enemy and make fear among enemy soldiers. Soldiers would ride on the elephant's back and shoot arrows and spears at the enemy. Elephants would also scare the horses in enemy armies which had never seen elephants. They were used in wars for a long time in some parts of the world. They could be important in winning battles, although most battles in the ancient world did not have elephants.
There were problems, though: war elephants could be hurt or scared by fire, arrows, and the blood and noise of a battle - that noise included thousands of men and horses screaming in pain, fear, and anger, and the clash of swords. Sometimes when the elephants got scared and angry, their riders lost control of them and the elephants would run wildly around the battlefield.
When this happened (today it is called "running amok"), some elephants would trample (step on and crush) and kill anyone in their way, not just enemy soldiers but soldiers in their own army. The elephant's rider would then have to kill the elephant by hammering a big spike into the elephant's neck so that the animal would not kill soldiers in its own army.
Another problem is that elephants eat lots of food -- up to 150 kg of grass and other plants a day -- and this food had to be brought along with the army. They also need people to look after them and could get sick or hurt in battle. Also, elephants do not do well in cold weather. Finally, elephants cost a lot of money.
In some parts of the world, they were used on the battlefield throughout the Medieval era(about AD 600 to AD 1400). However, after that, they were not used much because of the invention of firearms(guns) and other gunpowder weaponry(cannons etc.) in early modern warfare. After this, war elephants were only used in non-combat engineering and labor roles, as well as being used for minor ceremonial uses (parades and other events).
Some Examples of the Use of War Elephants
A carving from India made sometime between 600 BC to 400 BC showing war elephants
Chandragupta Maurya (321–297 BC), formed the Maurya Empire in India, the largest empire to exist in South Asia. When his empire was very large, Chandragupta is said to have had an army of 600,000 infantry, 30,000 cavalry (soldiers who fought on horses), 8,000 chariots and 9,000 war elephants, although we do not know if these numbers are right.
A depiction of war elephants from an Indian army attacking a Greek army led by Alexander the Great at the Battle of the Hydaspes River, located in what is now Pakistan (326 BC), (painting by Andre Castaigne)
The most famous use of war elephants was by Hannibal, a general who was from the empire of Carthage, which included parts of North Africa and southern and eastern Spain (see the map of the Mediterranean area in 218 BC above). He lived about 2,200 years ago, and he brought 37 war elephants with his army from what is now Spain when he went to war against the Romans in Italy.
War elephants depicted in Hannibal crossing the Rhône River, a river in what is now southern France, 218 BC. Paintingby Henri Motte (1878)
A modern painting of Hannibal's army in the snow crossing the Alps on its way to Italy to fight the Romans in 218 BC.
The journey that Hannibal and his army took from Cartagena in Spain to the River Trebia in northern Italy was about 1,600 km and might have taken 4 months or more. When the Roman soldiers saw the elephants, they and their horses were so scared that Hannibal won a great victory.
However, just after the battle near the River Trebia in December, almost all of the elephants had died from the long, hard trip, and so Hannibal continued the war in Italy for many years without any elephants. Battles, sickness, and cold and snow in the Alps killed them.
War elephants were also used in Southeast Asia (Myanmar, Thailand, Cambodia, Vietnam). A Thai war elephant as it might have looked around 1750 (from a modern movie)
Armor for a war elephant from India. It was made sometime between the years 1600 to 1700. This armor is composed of 5,840 plates of metal and weighs 118 kg, some plates are missing and originally the total number would be 8,439 and weigh 159 kg! The tusk swords that accompany this armor (not on display) weigh in at 10 kg.
The Danger to Elephants Today
There are no elephants in North Africa today. They are extinct there, mainly because they were killed for their ivory tusks. The ivory trade is illegal in most countries, but poachers still kill elephants for their tusks, which are illegally sold for a lot of money.
African elephant populations have fallen from an estimated 12 million a century ago to some 400,000. In recent years, at least 20,000 elephants have been killed in Africa each year for their tusks. African forest elephants have been the worst hit. Their populations declined by 62% between 2002-2011 and they have lost 30% of their geographical range, with African savanna elephants declining by 30% between 2007-2014.
This dramatic decline has continued and even accelerated with cumulative losses of up to 90% in some landscapes between 2011 and 2015. Today, the greatest threat to African elephants is wildlife crime, primarily poaching for the illegal ivory trade, while the greatest threat to Asian elephants is habitat loss, which results in human-elephant conflict. (Link to more World Wildlife Fund elephant information)
NASA, the National Aeronautics and Space Administration is an independent agency of the U.S. federal government responsible for the civil (non-military) space program, aeronautics research, and space research.
We all travel in time! We travel one year in time between birthdays, for example. And we are all traveling in time -- into the future -- at about the same speed: 1 second per second.
We usually experience time at one second per second. Credit: NASA/JPL-Caltech
NASA's space telescopes also give us a way to look back in time. Telescopes help us see stars and galaxies that are very far away. It takes a long time for the light from faraway galaxies to reach us. So, when we look into the sky with a telescope, we are seeing what those stars and galaxies looked like a very long time ago.
This image from the Hubble Space Telescope shows galaxies that are very far away as they existed a very long time ago. Credit: NASA, ESA and R. Thompson (Univ. Arizona)
A galaxy has been found that is 13.3 billion light-years away. What is seen by telescopes is from light that left the galaxy, named HD1, 13.3 billion (13,300,000,000) years ago! This year, 2024, the James Webb Telescope found an even older galaxy, called JADES-GS-z14-0. The collection of stars was detected as it appeared only 290 million years after the Big Bang (the beginning of the Universe). So that means that if the Universe is 13.8 billion years old, it means we're seeing galaxy JADES-GS-z14-0 as it was when the Universe was only 2% of its current age!
However, when we think of the phrase "time travel," we are usually thinking of traveling faster than 1 second per second. That kind of time travel sounds like something you'd only see in movies or science fiction books. Could it be real? Science says yes!
How do we know that time travel is possible?
More than 100 years ago, a famous scientist named Albert Einstein came up with an idea about how time works. He called it relativity. This theory says that time and space are linked together. Einstein also said our universe has a speed limit: nothing can travel faster than the speed of light (300,000 kilometers per second ).
What does this mean for time travel? Well, according to this theory, the faster you travel, the slower you experience time. Scientists have done some experiments to show that this is true.
Although humans can't jump into a time machine and go back in time, we do know that clocks on airplanes and satellites travel at a different speed than those on Earth.
For example, there was an experiment that used two clocks set to the exact same time. One clock stayed on Earth, while the other flew in an airplane (going in the same direction Earth rotates).
After the airplane flew around the world, scientists compared the two clocks. The clock on the fast-moving airplane was slightly behind the clock on the ground. So, the clock on the airplane was traveling slightly slower in time than 1 second per second.
Can we use time travel in everyday life?
We can't use a time machine to travel hundreds of years into the past or future. That kind of time travel only happens in books and movies. But the math of time travel does affect the things we use every day.
For example, we use GPS satellites to help us figure out how to get to new places. (Check out our video about how GPS satellites work.) NASA scientists also use a high-accuracy version of GPS to keep track of where satellites are in space. But did you know that GPS relies on time-travel calculations to help you get around town?
GPS satellites orbit around Earth very quickly at about 8,700 miles (14,000 kilometers) per hour. This slows down GPS satellite clocks by a small fraction of a second (similar to the airplane example above).
GPS satellites orbit around Earth at about 8,700 miles (14,000 kilometers) per hour. Credit: GPS.gov
However, the satellites are also orbiting Earth about 20,200 km above the surface. This actually speeds up GPS satellite clocks by a slighter larger fraction of a second.
Here's how: Einstein's theory also says that gravity curves space and time, causing the passage of time to slow down. High up where the satellites orbit, Earth's gravity is much weaker. This causes the clocks on GPS satellites to run faster than clocks on the ground.
The combined result is that the clocks on GPS satellites experience time at a rate slightly faster than 1 second per second. Luckily, scientists can use math to correct these differences in time.
If scientists didn't correct the GPS clocks, there would be big problems. GPS satellites wouldn't be able to correctly calculate their position or yours. The errors would add up to a few miles each day, which is a big deal. GPS maps might think your home is nowhere near where it actually is!
In Summary:
Yes, time travel is indeed a real thing. But it's not the same as what you've probably seen in the movies. Under certain conditions, it is possible to experience time passing at a different rate than 1 second per second. And there are important reasons why we need to understand this real-world form of time travel.
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