When Schrödinger's Cat meets astronomy

[MirceaKitsune]

A few days ago I read in more depth about Schrödinger's Cat. The thought experiment in which, if you put a cat inside a box and rely a deadly hazard on the quantum state of an atom, there's a 50/50 probability for the cat to be either alive or dead, which is uncertain until someone observes or measures which of the two things has happened.

 

So I thought to myself: How would this concept apply to something even greater... like planets, and life on other worlds? After all, there's countless processes involved in the the formation of planets which could be influenced by the quantum state of various particles. For example, what if a sun reaches a point where it becomes so unstable, the electron spin of one atom might decide whether it and its entire solar system blow up or not? This is an amazing perspective, and it's already changed the way I look at solar systems and alien life. Here's why:

 

First of all, this might fundamentally change the question "how many planets out there harbor life". If we're talking about our observable universe, the most likely answer is that most planets don't but there are exceptions like Earth. To find the answer, we would have to observe the surface of each planet... and this is where the fun part comes in: What if life on the planet was subject to quantum probability at some point? Until someone finds a way to see the planet, it might or might not harbor life simultaneously! We'd only know which of the two is true once we finished exploring the entire planet. At that moment, all probabilities would collapse into one (Copenhagen interpretation) or we position ourselves on a definite time line in relation to the planet (Many-worlds interpretation).

 

The many-worlds version is the most fun part. Because it would imply that, in a parallel time line, every planet we observe to be without life in relationship to us might in fact be full of life in a different dimension... and vice-versa. Mars for example is a dead world... mostly a rock boulder covered in dust. But what if a quantum dependent event millions of years ago removed the reason why it lost its rivers and atmosphere? At this very moment in time, Mars might have rivers plants and animals just like Earth! We here on Earth have unwillingly decided that it doesn't, the moment we observed its surface and the universe "fed" us one of many realities.

 

But what about Earth itself? Obviously the universe has to be full of quantum states where Earth is either a barren world like Mars, was destroyed completely, or was never born at all. We like to think of Earth as being lucky to have the perfect conditions to harbor life, as if it's a miracle that it does; We're just the right distance from the sun, we have a molten core that creates a magnetic field and shield, we have a moon that stabilizes our orbit, etc. But is it really a miracle?

 

In quantum realities where the Earth didn't have all these factors, there wouldn't be any life on Earth. Even if there's just one out of a trillion states where Earth has these conditions, while in all other states Earth is barren or dead / unborn, life automatically exists in that quantum state only. This means that we aren't lucky, because Earth as we know it doesn't exist a zillion times more than it does, and was destroyed much more often / likely than it hasn't. Life evolved only in those states where Earth kept having the right conditions... and since we don't exist to see the others, we think we are lucky.

 

Taking the idea further, it's also likely that there are many quantum states in which Earth was already destroyed by now. Maybe in a parallel timeline, a meteor hit just 10 minutes ago, and now the Earth is flying around in pieces. Or maybe in yet another timeline, the meteor that killed off the dinosaurs missed... meaning humans don't exist and the world might be filled with raptors who now have cars and computers similar to ours. This also means that there are different observers to decide which quantum state is the "truth"... because in states where life took a different turn, you and I aren't here to ask these questions, but another creature might be.

 

So how do you think the concept behind Schrödinger's Cat should change our view of planets and alien life? Does it mean we misunderstand how likely it is for life to exist, considering planets might have states where they both do and don't contain life? How many planets out there, which from our perspective are barren, might harbor life if we consider all quantum probabilities? In how many states is Earth still here, compared to states where it no longer is?

Edited August 2, 2014 by MirceaKitsune

[Strange]

None of those objects are in the sort of isolation from any interaction that the hypothetical cat is. An object like a planet (or even, realistically, a cat) cannot exist in a state of superposition. Some macroscopic (i.e. tiny) objects have been forced, temporarily into a state of superposition but this requires carefully controlled laboratory conditions near absolute zero, to avoid the state being disturbed by any external interaction (aka "observation").

 

You appear to think that "observe" means someone looks at it. It doesn't.

[MirceaKitsune]

None of those objects are in the sort of isolation from any interaction that the hypothetical cat is. An object like a planet (or even, realistically, a cat) cannot exist in a state of superposition. Some macroscopic (i.e. tiny) objects have been forced, temporarily into a state of superposition but this requires carefully controlled laboratory conditions near absolute zero, to avoid the state being disturbed by any external interaction (aka "observation").

 

You appear to think that "observe" means someone looks at it. It doesn't.

 

But if the quantum state of one atom in a sun has a 50/50 chance of deciding whether that sun explodes or continues to go on, isn't that the same thing?

 

As for observing, I thought of it as the act of a person being aware what the result is, through any means and measurements. We do see stars at night on the sky for instance, but not what planets orbit them or if these planets contain life. So I assumed this means a planet might or might not be there or in a certain state until we see clearly that it is or isn't.

[Strange]

But if the quantum state of one atom in a sun has a 50/50 chance of deciding whether that sun explodes or continues to go on, isn't that the same thing?

 

Is that some sort of chaos theory idea? I don't see how a single atom can have a significant effect on the sun.

 

And, anyway, in terms of quantum mechanics, that atom will not be in a state of quantum superposition between those states because it is continually interacting with (being observed by) all the other atoms around it.

 

 

As for observing, I thought of it as the act of a person being aware what the result is, through any means and measurements. We do see stars at night on the sky for instance, but not what planets orbit them or if these planets contain life. So I assumed this means a planet might or might not be there or in a certain state until we see clearly that it is or isn't.

 

That might be a nice philosophical game (along the lines of "if a tree falls in a forest...") but it doesn't appear to have any basis in reality.

[Nicholas Kang]

 

But if the quantum state of one atom in a sun has a 50/50 chance of deciding whether that sun explodes or continues to go on, isn't that the same thing?

 

As for observing, I thought of it as the act of a person being aware what the result is, through any means and measurements. We do see stars at night on the sky for instance, but not what planets orbit them or if these planets contain life. So I assumed this means a planet might or might not be there or in a certain state until we see clearly that it is or isn't.

 

The Sun has no atom. The immense temperature and pressure force atoms to blow and form plasma, the fourth state of matter. It is done by heating gas. Electrons do not orbit around the nucleus of the atom, but simply move in a indefinite random way. Even if one atom(assume that you are right) has a 50% chance to decide the Sun will explode, others might have a 50% chance to decide the Sun to continue shining. This will cancel out each other and approach a balance state.

 

For observing, I think I shall learn more from Strange, currently no idea of what Strange meant.

[Strange]

 

The Sun has no atom.

 

Good point!

 

For observing, I think I shall learn more from Strange, currently no idea of what Strange meant.

 

 

My understanding is that this is any "measurement" or interaction that determines the state of an object. That might be a person making a measurement in the lab, or it might be the object interacting with something else. At which point its state becomes definite, rather than being potentially in a superposition of different states.

 

The fact that this happens spontaneously (without a human observer) is one of the challenges of quantum computing, which relies on trying to keep "qbits" in a state of superposition for an extended period. But that means trying to keep them isolated from the material around them, which is not easy.

[Nicholas Kang]

So, basically, observing does not only mean seeing through out the whole experiment by your eyes but it also means interaction between the subject and you, the observer?

If I say I observe a television show, does this means I am not only observing the videos and pictures but the music and audio must also be taken into account?

[Strange]

So, basically, observing does not only mean seeing through out the whole experiment by your eyes but it also means interaction between the subject and you, the observer?

 

Or an interaction between the subject and ... well, anything really.

 

If I say I observe a television show, does this means I am not only observing the videos and pictures but the music and audio must also be taken into account?

 

 

We were only talking about quantum effects.

[Nicholas Kang]

Ah?! What about macroscopic objects? Then if there is an interaction between both, wouldn`t the condition be interupted because you are disturbing the subject and thus affecting the results?

[Strange]

Ah?! What about macroscopic objects? Then if there is an interaction between both, wouldn`t the condition be interupted because you are disturbing the subject and thus affecting the results?

 

Well, there are measurement effects that sometimes have to be taken into account. For example, if you are using light to observe something small, the light might heat it up or make it move. But these are rarely serious problems.

 

A lot of good experiment design is about taking those effects into account and finding ways to eliminate them or cancel them out.

Edited August 2, 2014 by Strange

[Nicholas Kang]

Sorry Strange, my sentences seemed to let you misunderstood my meaning. I don`t mean combining both questions. It should be:

 

1. Ah?! What about macroscopic objects?- I mean more detailed explanation, not only quantum effects as stated below.

 

We were only talking about quantum effects.

 

2. Then if there is an interaction between both, wouldn`t the condition be interupted because you are disturbing the subject and thus affecting the results?- I mean if we, the observer, have interaction while observing or it is part of the observing process, then would we disturb the experiment process?

 

Or an interaction between the subject and ... well, anything really.

[Strange]

2. Then if there is an interaction between both, wouldn`t the condition be interupted because you are disturbing the subject and thus affecting the results?- I mean if we, the observer, have interaction while observing or it is part of the observing process, then would we disturb the experiment process?

 

Yes, that's the whole point. If, for example, you have a photon in a superposition of two states (spin of +1 and -1 is the usual example) and you measure it, then it will be in a single state because you measured it. But it could also "collapse" into a single state because it interacts with something else.

 

More generally, if you want to detect a photon the only way of doing that is by destroying the photon.

[Delta1212]

Any interaction collapses the superposition, and we only detect something when it interacts with something else. So the only way for us to observe or measure something is by causing it to interact and seeing the result. So any observation we make collapses the wave function, but it isn't the fact that we observed it that is responsible, it is the interaction.

 

"Observation collapses the wavefunction" is sort of a shorthand that can be misleading because the definition of 'observation' is slightly different than we'd typically use and doesn't require an agent to do the observing.

[MirceaKitsune]

I understand. I think I misunderstood what observation / measurement meant in that case, and went by the idea that it's the moment when the mind perceives the entity through any means. I'm still a little confused when a real interaction between the observer and object / particle takes place however, and how one is prevented.

 

Do multiple states collapse if the object reflects any photons of light onto the person's body for example? And when is the object "sealed" away from observation?

[Delta1212]

Alright, think of it like this: If you're playing pool and you hit the cue ball into the 8 ball, the 8 ball "measures or observes" the position and momentum of the cue ball at the time of the interaction, because those properties matter to how they interact and how the 8 ball moves (how fast and in what direction) after getting hit. The 8 ball does not measure the color of the cue ball because it has absolutely no bearing on the interaction.

 

A property of an object is observed if the object interacts with something in such a way that the state that that property is in matters to the interaction. An object is "sealed away from observation" if it isn't in a position to interact with anything else (in a way that whatever property you are attempting to keep in a superposition has an effect on the interaction). This is generally very difficult to do with any large object over any length of time, which is why Schrödinger's Cat is purely a thought experiment, because there is no way to fully isolate a cat in a box from the rest of the universe such that it is completely impossible to detect anything whatsoever from inside the box.

 

For smaller particles that you can keep at temperatures around absolute zero in a near vacuum, it's a bit easier to isolate them from everything else for extended periods of time to keep any interactions from happening.

[MirceaKitsune]

...

 

Thank you, that explains it a lot better and I think I understand now. And yeah, isolating anything this well in practice would probably be very difficult or impossible.

 

There might however be one thing: Objects so far away that no particle from one managed to reach the other. Earth and objects on it might have not interacted with planets so far away that no photon reflected by said planet reached us yes. Then again, we don't know whether there are things such as dark matter which travels faster than light, so such couldn't be known for sure either.