Erwin Schrödinger was a Nobel prize-winning physicist. Schrödinger proposed a paradox in 1935 to illustrate a point in quantum mechanics about the nature of wave particles.
At the center of quantum theory is the idea of a wave function. A wave-function describes all the possible states subatomic particles can have, including energy, momentum, and position. A wave-function for a particle reveals there is some probability that it can be in any allowed position. However, you can only know the position by observing it. Without observation, you have to say that it can be doing any of the things, even if the probability is small.

Erwin Schrödinger proposed a paradox

A cat is placed in a steel box along with a Geiger counter, a vial of poison, a hammer, and a radioactive substance. When the radioactive substance decays (it decays as a random process), the Geiger detects it, triggers the hammer, and release the poison, which kills the cat.
Until the box is opened, the cat's state is entirely unknown. Therefore, the cat can be treated as both alive and dead simultaneously until it is observed. If you try to make predictions about the cat's status, you're possibly going to be wrong. But if you assume it's a combination of all of the possible states, you'll be correct.
Really minute things don't obey Newton's Laws. The rule that we use to govern the motion of a ball or car can't be used to explain how an electron or atom works.

The feline paradox: Schrodinger's cat

<figure><picture><source srcset="https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.133.1.jpg 133w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.152.1.jpg 152w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.162.1.jpg 162w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.210.1.jpg 210w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.224.1.jpg 224w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.225.1.jpg 225w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.280.1.jpg 280w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.352.1.jpg 352w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.470.1.jpg 470w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.536.1.jpg 536w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.590.1.jpg 590w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.676.1.jpg 676w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.710.1.jpg 710w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.768.1.jpg 768w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.885.1.jpg 885w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.945.1.jpg 945w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.1190.1.jpg 1190w, https://www.nationalgeographic.com/content/dam/news/photos/000/702/70284.adapt.1900.1.jpg 1900w" sizes="785px"><img width="785" height="956"></picture></figure><h2>Google honors the physicist today with a Doodle. We explain the science behind his famous paradox.</h2><div dir="ltr">2 Minute Read</div><div itemprop="creator" itemscope="" itemtype="http://schema.org/Person" dir="ltr">By Melody Kramer, <a href="http://news.nationalgeographic.com/" dir="ltr">National Geographic</a></div>PUBLISHED <time itemprop="datePublished" dateposition="top" datetime="2013-08-14T07:12:00-0400" dir="ltr">August 14, 2013</time>His feline paradox thought experiment has become <a href="http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat_in_popular_culture" dir="ltr">a pop culture staple</a>, but it was Erwin Schrödinger's work in quantum mechanics that cemented his status within the world of physics.<div>Today’s</div><div>Popular Stories</div><div>Blood plasma touted as COVID-19 breakthrough. But does it work?</div>The Nobel prize-winning physicist would have turned 126 years old on Monday and to celebrate, Google honored his birth with a <a href="http://www.youtube.com/watch?v=Wjftk0AVPKI" dir="ltr">cat-themed Doodle</a>, which pays tribute to the paradox Schrödinger proposed in 1935 in the following theoretical experiment.A cat is placed in a steel box along with a Geiger counter, a vial of poison, a hammer, and a radioactive substance. When the radioactive substance decays, the Geiger detects it and triggers the hammer to release the poison, which subsequently kills the cat. The radioactive decay is a random process, and there is no way to predict when it will happen. Physicists say the atom exists in a state known as a superposition—both decayed and not decayed at the same time.Until the box is opened, an observer doesn't know whether the cat is alive or dead—because the cat's fate is intrinsically tied to whether or not the atom has decayed and the cat would, as Schrödinger put it, be "living and dead ... in equal parts" until it is observed. (More physics: <a href="http://news.nationalgeographic.com/news/2013/07/130704-water-slide-water-park-theme-design-engineering-physics/" dir="ltr">The Physics of Waterslides</a>.)In other words, until the box was opened, the cat's state is completely unknown and therefore, the cat is considered to be both alive and dead at the same time until it is observed."If you put the cat in the box, and if there's no way of saying what the cat is doing, you have to treat it as if it's doing all of the possible things—being living and dead—at the same time," explains <a href="http://www.millikin.edu/academics/cas/physicsastronomy/Pages/Faculty.aspx" dir="ltr">Eric Martell</a>, an associate professor of physics and astronomy at Millikin University. "If you try to make predictions and you assume you know the status of the cat, you're [probably] going to be wrong. If, on the other hand, you assume it's in a combination of all of the possible states that it can be, you'll be correct."Immediately upon looking at the cat, an observer would immediately know if the cat was alive or dead and the "superposition" of the cat—the idea that it was in both states—would collapse into either the knowledge that "the cat is alive" or "the cat is dead," but not both.Schrödinger developed the paradox, says Martell, to illustrate a point in quantum mechanics about the nature of wave particles."What we discovered in the late 1800s and early 1900s is that really, really tiny things didn't obey Newton's Laws," he says. "So the rules that we used to govern the motion of a ball or person or car couldn't be used to explain how an electron or atom works."At the very heart of quantum theory—which is used to describe how subatomic particles like electrons and protons behave—is the idea of a wave function. A wave function describes all of the possible states that such particles can have, including properties like energy, momentum, and position."The wave function is a combination of all of the possible wave functions that exist," says Martell. "A wave function for a particle says there's some probability that it can be in any allowed position. But you can't necessarily say you know that it's in a particular position without observing it. If you put an electron around the nucleus, it can have any of the allowed states or positions, unless we look at it and know where it is."That's what Schrödinger was illustrating with the cat paradox, he says."In any physical system, without observation, you cannot say what something is doing," says Martell. "You have to say it can be any of these things it can be doing—even if the probability is small."

Google honors the physicist's birthday today with a Doodle. We explain the science behind his famous paradox.

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Google honors the physicist today with a Doodle. We explain the science behind his famous paradox.

His feline paradox thought experiment has become <a href="http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat_in_popular_culture">a pop culture staple </a>, but it was Erwin Schrödinger's work in quantum mechanics that cemented his status within the world of physics.

The Nobel prize-winning physicist would have turned 126 years old on Monday and to celebrate, Google honored his birth with a <a href="http://www.youtube.com/watch?v=Wjftk0AVPKI">cat-themed Doodle </a>, which pays tribute to the paradox Schrödinger proposed in 1935 in the following theoretical experiment.

A cat is placed in a steel box along with a Geiger counter, a vial of poison, a hammer, and a radioactive substance. When the radioactive substance decays, the Geiger detects it and triggers the hammer to release the poison, which subsequently kills the cat. The radioactive decay is a random process, and there is no way to predict when it will happen. Physicists say the atom exists in a state known as a superposition—both decayed and not decayed at the same time.

Until the box is opened, an observer doesn't know whether the cat is alive or dead—because the cat's fate is intrinsically tied to whether or not the atom has decayed and the cat would, as Schrödinger put it, be "living and dead ... in equal parts" until it is observed. (More physics: <a href="http://news.nationalgeographic.com/news/2013/07/130704-water-slide-water-park-theme-design-engineering-physics/">The Physics of Waterslides </a>.)

In other words, until the box was opened, the cat's state is completely unknown and therefore, the cat is considered to be both alive and dead at the same time until it is observed.

"If you put the cat in the box, and if there's no way of saying what the cat is doing, you have to treat it as if it's doing all of the possible things—being living and dead—at the same time," explains <a href="http://www.millikin.edu/academics/cas/physicsastronomy/Pages/Faculty.aspx">Eric Martell </a>, an associate professor of physics and astronomy at Millikin University. "If you try to make predictions and you assume you know the status of the cat, you're [probably] going to be wrong. If, on the other hand, you assume it's in a combination of all of the possible states that it can be, you'll be correct."

Immediately upon looking at the cat, an observer would immediately know if the cat was alive or dead and the "superposition" of the cat—the idea that it was in both states—would collapse into either the knowledge that "the cat is alive" or "the cat is dead," but not both.

Schrödinger developed the paradox, says Martell, to illustrate a point in quantum mechanics about the nature of wave particles.

"What we discovered in the late 1800s and early 1900s is that really, really tiny things didn't obey Newton's Laws," he says. "So the rules that we used to govern the motion of a ball or person or car couldn't be used to explain how an electron or atom works."

At the very heart of quantum theory—which is used to describe how subatomic particles like electrons and protons behave—is the idea of a wave function. A wave function describes all of the possible states that such particles can have, including properties like energy, momentum, and position.

"The wave function is a combination of all of the possible wave functions that exist," says Martell. "A wave function for a particle says there's some probability that it can be in any allowed position. But you can't necessarily say you know that it's in a particular position without observing it. If you put an electron around the nucleus, it can have any of the allowed states or positions, unless we look at it and know where it is."

That's what Schrödinger was illustrating with the cat paradox, he says.

"In any physical system, without observation, you cannot say what something is doing," says Martell. "You have to say it can be any of these things it can be doing—even if the probability is small."

The Physics Behind Schrödinger's Cat Paradox

Erwin Schrödinger proposed a paradox

The feline paradox: Schrodinger's cat

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