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Guy uses a Ziploc bag to show why some things look backwards in mirrors while others don't

We get it now!

Photo credit: Canva

Why is text reversed in mirrors?

Have you ever wondered why text shows up backwards in a mirror? It's confusing to our brains because it doesn't seem like anything else is flipped like that. If we turn our head, it doesn't move the opposite direction in a mirror. Or does it? After all, right-handed you is actually left-handed you in the mirror. Right? (Wait, is that right?)

Mirrors can be confusing, despite not being very complicated. A mirror image is simply a reflection of what's before it. But when someone else is looking at us head on, they don't see text in reverse, so why don't we see what other people see when we see ourselves in a mirror?

mirrors, mirror, reflection, mirror image, science, how mirrors work Beyonce Mirror GIF Giphy

(If you think this is a super stupid question with a super obvious answer, congratulations. Pat yourself on the back and scootch along so the folks who don't fully grasp the physics of mirrors can enjoy a demonstration that makes it a little easier to understand.)

"Why do mirrors reverse text?" asks the creator behind @humanteneleven on YouTube. "You might think it's just a property of mirrors—they flip things from left to right—but that's not true." He then picks up a metal arrow to show that it points the same direction in the mirror as it does in real life. So why is the text flipped when the arrow isn't?

- YouTube youtu.be

He then holds up a book to show how the text on the book cover appears backwards, just like the shirt. But when he holds up a Ziploc bag with the word "HELLO" written on it, the word shows up properly.

That's because he had to flip the book over to see the cover text in the mirror. The baggy he could just hold up and see the letters through the transparent plastic, just as we see them in real life. If he flips the baggy over like he did the book, the text shows up backwards in the mirror, just like it does in real life.

"So it's actually not the mirror that's flipping anything from left to right," he says. "It's the human."

People appreciated the simple, straightforward explanation and demonstrations.

"One of the most insightful demonstrations I've seen. It's simple and explains the phenomenon. Well done!"

"While I've heard this explanation many times before, I've only recently seen it demonstrated with text-on-transparency, which is what really makes it click. Great video!"

"Love these sorts of demonstrations. It’s a bit of a complicated one, but I love seeing how different people's minds work when explaining simple things like this. My kid explains it with “left is on the left, right is on the right, things aren’t flipped, they are mirrored” but it’s true that you are the one who flips things and I’ve never thought of it that way before."

"Oh my God, I haven't understood explanations from physics videos about why mirrors flip but this, gosh this helps."

Mirrors have been hilariously befuddling people in other videos as they try to figure out how the mirror knows what's behind a barrier placed in front of objects.

@sarahcoome

this is kinda creepy 👀 #mirror #relatable #creepy

Is this something all of us should probably have learned in high school? Yes. Do all of us remember everything we learned in high school? No. Does the scientific explanation make perfect sense to everyone even if it's explained in detail? Um, no.

Like the reversed text question, having a simplified explanation that doesn't fully get into the nitty gritty physics and geometry of how mirrors work is helpful for some folks.

- YouTube youtu.be

For those who do want a bit more scientific substance to their explanations, this next video does a good job of giving a bit more detail while still keeping the explanation simple. It even uses a visual diagram to explain:

- YouTube youtu.be

And for those who say, "This is so basic! How do people not understand this?" here's a video that really does get into the nitty gritty physics and geometry of how mirrors work, diving into ray and wave optics, photons, wave functions, probability, and quantum mechanics. It's only 12 minutes, and it manages to entertain while explaining, but it certainly blows the notion that understanding mirrors is super simple.

- YouTube youtu.be

As one commenter wrote, "I thought I understood mirrors. I understand mirrors even less now. And that's a compliment."

Isn't science fun?

This article originally appeared in May. It has been updated.

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The 'world's slowest experiment,' going for nearly 100 years, is still endlessly fascinating

It takes nearly a decade for one drop of this liquid to fall.

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John Mainstone was the custodian of the Pitch Drop Experiment for 52 years.

Because we use water all the time, most of us have an intuitive sense of how long it takes a drop of water to form and fall. More viscous liquids, like oil or shampoo or honey, drop more slowly depending on how thick they are, which can vary depending on concentration, temperature and more. If you've ever tried pouring molasses, you know why it's used as a metaphor for something moving very slowly, but we can easily see a drop of any of those liquids form and fall in a matter of seconds.

But what about the most viscous substance in the world? How long does it take to form a falling drop? A few minutes? An hour? A day?

How about somewhere between 7 and 13 years?

pitch drop experiment, tar pitch, solid or liquid, physics, world's longest experimentPitch moves so slowly it can't be seen to be moving with the naked eye until it prepares to drop. Battery for size reference.John Mainstone/University of Queensland

The Pitch Drop Experiment began in 1927 with a scientist who had a hunch. Thomas Parnell, a physicist at the University of Queensland in Australia, believed that tar pitch, which appears to be a solid and shatters like glass when hit with a hammer at room temperature, is actually a liquid. So he set up an experiment that would become the longest-running—and the world's slowest—experiment on Earth to test his hypothesis.

Parnell poured molten pitch it into a funnel shaped container, then let it settle and cool for three years. That was just to get the experiment set up so it could begin. Then he opened a hole at the bottom of the funnel to see how long it would take for the pitch to ooze through it, form a droplet, and drop from its source.

It took eight years for the first drop to fall. Nine years for the second. Those were the only two drops Parnell was alive for before he passed away in 1948.

- YouTubewww.youtube.com

In total, there have been nine pitch drops in the University of Queensland experiment. The first seven drops fell between 7 and 9 years apart, but when air conditioning was added to the building after the seventh drop, the amount of time between drops increased significantly. The drops in 2000 and 2014 happened approximately 13 years after the preceding one. (The funnel is set up as a demonstration with no special environmental controls, so the seasons and conditions of the building can easily affect the flow of the pitch.)

The next drop is anticipated to fall sometime in the 2020s.

pitch drop experiment, tar pitch, solid or liquid, physics, world's longest experimentThe first seven drops fell around 8 years apart. Then the building got air conditioning and the intervals changed to around 13 years.RicHard-59

Though Parnell proved his hypothesis well before the first drop even fell, the experiment continued to help scientists study and measure the viscosity of tar pitch. The thickest liquid substance in the world, pitch is estimated to be 2 million times more viscous than honey and 20 billion times the viscosity of water. No wonder it takes so ridiculously long to drop.

One of the most interesting parts of the Pitch Drop Experiment is that in the no one has ever actually witnessed one of the drops falling at the Queensland site. The drops, ironically, happen rather quickly when they do finally happen, and every time there was some odd circumstance that kept anyone from seeing them take place.

The Queensland pitch drop funnel is no longer the only one in existence, however. In 2013, Trinity College in Dublin, Ireland, managed to capture its own pitch drop on camera. You can see how it looks as if nothing is happening right up until the final seconds when it falls.

- YouTubewww.youtube.com

Today, however, with the internet and modern technology, it's likely that many people will be able to witness the next drop when it happens. The University of Queensland has set up a livestream of the Pitch Drop Experiment, which you can access here, though watching the pitch move more slowly than the naked eye can detect is about as exciting as watching paint dry.

But one day, within a matter of seconds, it will drop, hopefully with some amount of predictability as to the approximate day at least. How many people are going to be watching a livestream for years, waiting for it to happen?

PoorJohn Mainstone was the custodian of the experiment for 52 years, from 1961 to 2013. Sadly, he never got to witness any of the five drops that took place during his tenure. Neither did Parnell himself with the two that took place while he was alive.

John Mainstone, pitch drop experiment, university of queensland, physicsJohn Mainstone, the second custodian of the Pitch Drop Experiment, with the funnel in 1990.John Mainstone, University of Queensland

Sometimes science is looks like an explosive chemical reaction and sometimes it's a long game of waiting and observing at the speed of nature. And when it comes to pitch dripping through a funnel, the speed of nature is about as slow as it gets.


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Simulation specialist reveals what would happen if you rode a rollercoaster without a harness

Not that you'd want to try it.

Imagine you’re at a Six Flags theme park, and after waiting an hour in line, you sit down in the front seat of The New Revolution, a looping roller coaster that hits top speeds of up to 55 miles per hour. The ride operator calls, “All clear,” your coaster takes off from the loading station, and you make your way up a lift hill. As the car goes clack clack clack, you realize that the lap bar was never secured and there’s no way back.

What would happen if you were stuck on a looping roller coaster and the harness stopped working? Could you hold on to the person securely seated next to you and make it through the loop, or would you be thrown out of the car for what would be a tragic ending? Popular YouTuber Zach D. Films, who specializes in digital recreations, showed what would happen if you rode a looping roller coaster without a harness, and the good news is that there’s a decent chance you will survive. (Not that you'd want to try, though.)

What would happen if I rode a rollercoaster without a harness?

“If the bar came loose while you were riding a roller coaster, you'd probably expect to immediately fall out, but that probably wouldn't happen,” Zach D. begins his video.

- YouTubeyoutu.be

According to Zach D., the competing forces of gravity and the speed at which you’re moving counteract each other, most likely keeping you safely in your seat. “You see, as you're being pulled into the loop, gravity tries to pull you down towards the ground, but because of the speed you're going and the direction of the tracks, a special force actually pushes you further down, outweighing the pull of gravity and keeping you in your seat,” Zach D. says in his video.

Another example of these forces is filling a bucket with a few inches of water, attaching a rope, and swinging it around your head. If you forcefully spin the bucket, the water will remain inside, even without anything to restrain it from falling out.


Even though science shows that it is possible to ride a looping rollercoaster without restraints, there aren't many people out there who want to try it. In November 2024, a passenger on the Desert Storm coaster at Castles and Coasters in Phonix, Arizona, claimed that his restraint released while he was on the ride. The restraint failure happened as the coaster climbed its first lift hill so he could exit quickly and make it to the emergency stairs near the coaster's peak.

"We started going up, everything seems to be OK. And then, when we get closer to the top, I hear a click. Different from the click of the roller coaster going up on the chain," he said. "So I check my bar, and when I pushed it, it released. It opened." The incident was caught on camera, and the footage is chilling.

- YouTubewww.youtube.com

While the idea of riding a roller coaster without a lap bar is horrifying, Zach D. proves that physics may be your unexpected friend in case of a lap bar failure. That being said, let’s keep those restraints locked and double-checked. Roller coasters are meant to be fun, not a test of your centrifugal force knowledge.

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Physicist demonstrates how to break a ruler with a newspaper and it's utterly delightful

Her enthusiasm is everything.

Photo by Roman Kraft on Unsplash

A simple sheet of newspaper can produce an enormous amount of force.

Have you ever had a teacher whose enthusiasm for their subject piqued your interest more than the subject itself? I had a biology professor in college who would talk in a low almost-whisper most of the time, but when she got excited about mitochondria or cellular respiration or the stages of mitosis, her voice would rise into a loud, high-pitched shriek. While her exuberance didn't make me fall in love with cellular biology, it did capture my attention and provide some chuckle-worthy entertainment while I was learning.

For people who don't have a natural inclination toward certain subjects, a passionate teacher can make all the difference. That's one reason a video of Texas A&M University (TAMU) physicist Dr. Tatiana Erukhimova explaining how atmospheric pressure works is so delightful.

Dr. Erukhimova has been teaching at TAMU for more than 20 years and is the co-author of an undergraduate textbook, "Atmospheric Thermodynamics: Elementary Physics and Chemistry." She is an award-winning educator, and when you see her physics demonstrations shared on TAMU Physics & Astronomy's YouTube channel, it's not hard to see why.

When most of us think of atmospheric pressure, we think about the weather. But Erukhimova demonstrates how atmospheric pressure can give a newspaper the power to break a ruler. (Sort of—the person actually breaks the ruler, but the newspaper is the key to enabling it to happen.) This demonstration would be cool on its own, but Erukhimova's energy is what truly makes the lesson.

Watch and enjoy:

(I may or may not be adding "Did I impress you? NO!" to my regular sayings.)

"Dr. Tatiana" has many similar videos, all of which have the same passion and enthusiasm. Watch her delight in making balloons shrink in liquid nitrogen and then come back to life.

And watch how she describes the "confidence and courage" you need to do a tablecloth inertia demonstration:

So much fun. Three cheers for teachers who make learning fun simply by enthusiastically sharing their wonder at how things work.

And if you want to see more from Dr. Erukhimova, check out her TEDx talk on Physics as a Street Art:

This article originally appeared two years ago.

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