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Would every particle in the universe not have some form of measurement occurring at any given time?
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I know this is probably a common point of confusion, but I have a specific question about measurements in Quantum Mechanics. I read an explanation on this, but still have a point of confusion.
The explanation of why a measurement somehow affects what occurs in a quantum experiment, for example the double slit experiment, seems to be that by measuring, even just by watching, we interact with the system and cause the "wave function to collapse". But it seems to me, with such a broad definition of "measurement", all particles, everywhere in the universe, would in some small way be measured at any given instance.
This answer explains that light is a form of measurement, but light, after all, is not the only way to perform measurements, as we very often measure things purely with gravity, and would all particles in the universe not be subject to (and the source of) some trace amount of gravity? Or have some interaction with some other particle, in some way shape or form? It seems like the answer would be yes. So it seems like we would never be able to observe an experiment without that collapse.
With "measurements" in quantum mechanics, interactions per se, why are they not always occurring?
quantum-mechanics quantum-interpretations measurement-problem wavefunction-collapse decoherence
edited 5 mins ago
Qmechanic♦
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I know this is probably a common point of confusion, but I have a specific question about measurements in Quantum Mechanics. I read an explanation on this, but still have a point of confusion.
The explanation of why a measurement somehow affects what occurs in a quantum experiment, for example the double slit experiment, seems to be that by measuring, even just by watching, we interact with the system and cause the "wave function to collapse". But it seems to me, with such a broad definition of "measurement", all particles, everywhere in the universe, would in some small way be measured at any given instance.
This answer explains that light is a form of measurement, but light, after all, is not the only way to perform measurements, as we very often measure things purely with gravity, and would all particles in the universe not be subject to (and the source of) some trace amount of gravity? Or have some interaction with some other particle, in some way shape or form? It seems like the answer would be yes. So it seems like we would never be able to observe an experiment without that collapse.
With "measurements" in quantum mechanics, interactions per se, why are they not always occurring?
quantum-mechanics quantum-interpretations measurement-problem wavefunction-collapse decoherence
edited 5 mins ago
Qmechanic♦
97.8k121641052
asked 2 hours ago
john doe
1113
New contributor
john doe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Possible duplicate of What is the quantum mechanical definition of a measurement?
– Stéphane Rollandin
28 mins ago
add a comment |Â
up vote
2
down vote
favorite
up vote
2
down vote
favorite
I know this is probably a common point of confusion, but I have a specific question about measurements in Quantum Mechanics. I read an explanation on this, but still have a point of confusion.
The explanation of why a measurement somehow affects what occurs in a quantum experiment, for example the double slit experiment, seems to be that by measuring, even just by watching, we interact with the system and cause the "wave function to collapse". But it seems to me, with such a broad definition of "measurement", all particles, everywhere in the universe, would in some small way be measured at any given instance.
This answer explains that light is a form of measurement, but light, after all, is not the only way to perform measurements, as we very often measure things purely with gravity, and would all particles in the universe not be subject to (and the source of) some trace amount of gravity? Or have some interaction with some other particle, in some way shape or form? It seems like the answer would be yes. So it seems like we would never be able to observe an experiment without that collapse.
With "measurements" in quantum mechanics, interactions per se, why are they not always occurring?
quantum-mechanics quantum-interpretations measurement-problem wavefunction-collapse decoherence
edited 5 mins ago
Qmechanic♦
97.8k121641052
asked 2 hours ago
john doe
1113
New contributor
john doe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I know this is probably a common point of confusion, but I have a specific question about measurements in Quantum Mechanics. I read an explanation on this, but still have a point of confusion.
The explanation of why a measurement somehow affects what occurs in a quantum experiment, for example the double slit experiment, seems to be that by measuring, even just by watching, we interact with the system and cause the "wave function to collapse". But it seems to me, with such a broad definition of "measurement", all particles, everywhere in the universe, would in some small way be measured at any given instance.
This answer explains that light is a form of measurement, but light, after all, is not the only way to perform measurements, as we very often measure things purely with gravity, and would all particles in the universe not be subject to (and the source of) some trace amount of gravity? Or have some interaction with some other particle, in some way shape or form? It seems like the answer would be yes. So it seems like we would never be able to observe an experiment without that collapse.
With "measurements" in quantum mechanics, interactions per se, why are they not always occurring?
quantum-mechanics quantum-interpretations measurement-problem wavefunction-collapse decoherence
quantum-mechanics quantum-interpretations measurement-problem wavefunction-collapse decoherence
edited 5 mins ago
Qmechanic♦
97.8k121641052
asked 2 hours ago
john doe
1113
New contributor
john doe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 5 mins ago
Qmechanic♦
97.8k121641052
asked 2 hours ago
john doe
1113
New contributor
john doe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 5 mins ago
Qmechanic♦
97.8k121641052
edited 5 mins ago
Qmechanic♦
97.8k121641052
edited 5 mins ago
Qmechanic♦
97.8k121641052
97.8k121641052
asked 2 hours ago
john doe
1113
New contributor
john doe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 hours ago
john doe
1113
asked 2 hours ago
john doe
1113
1113
New contributor
john doe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
john doe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
john doe is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Possible duplicate of What is the quantum mechanical definition of a measurement?
– Stéphane Rollandin
28 mins ago
add a comment |Â
Possible duplicate of What is the quantum mechanical definition of a measurement?
– Stéphane Rollandin
28 mins ago
Possible duplicate of What is the quantum mechanical definition of a measurement?
– Stéphane Rollandin
28 mins ago
Possible duplicate of What is the quantum mechanical definition of a measurement?
– Stéphane Rollandin
28 mins ago
add a comment |Â
2 Answers
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Not every interaction is measurement or collapses the wave function. When light reflects off a mirror, the phase information is preserved. As each single photon hits the mirror and scatters on an electron, the photon doesn't hit the mirror in just one point or interacts with just one electron. Instead each single photon hits the entire mirror and interacts with all electrons in the mirror. In other words, due to the uncertainty principle, the interaction is a superposition of interactions with every electron in the mirror. This uncertainty preserves the wave function of the photon from collapsing.
The same concept applies to other collective processes, including the photon's travel through space, whether flat or curved by gravity. If the photon is allowed to take any trajectory, then the photon takes all of them simultaneously with different probabilities and therefore acts like a wave. In this case the photon's trajectory through space is a superposition of all possible trajectories. Therefore gravity does not collapse the photon's wave function (at least while away from black holes).
Furthermore, certain particles have a low probability of interaction, e.g. neutrinos that can fly through the universe as through a virtually empty space. Also, the hypothetical particles of dark matter may not nteract at all other than via gravity while the gravity interactions almost always would be a collective process described above that would not collapse the wave function.
Science is about predicting practical results. Your question however seems rather hypothetical. Whether the answer is yes or no, there seems to be no practical difference either way. Finally, quantum mechanics alone does not describe the universe as a whole. This requires quantum gravity to view spacetime as a function rather than a set of independent variables and effectively make this world a projection. Thus your question cannot be fully answered until quantum gravity has been developed.
answered 1 hour ago
safesphere
6,78611239
Can you clarify "due to the uncertainty principle.." This principle is normal taught within the context of measurement. What meaning are you giving to it here? thanks.
– Bruce Greetham
15 mins ago
add a comment |Â
up vote
1
down vote
What you describe is the process known as decoherence: any interaction of a quantum system with its environment (e.g. with photons or other particles passing by, and, yes, most likely interacting through gravity, although we don't have a theory to fully describe this yet) has the potential to destroy its genuinely quantum nature, turning quantum superpositions into mere classical statistical ones. This process is indeed the first half of a measurement, the second half being the reading out of the result which resolves the remaining statistical superposition into a single result.
But decoherence is not an all or nothing, instantaneous process: it is progressive in time, and the weaker the interaction between a system and its environment, the slower it will decohere. When we actually do a measurement we deliberately arrange for the interaction to be strong enough and we wait long enough for full decoherence to occur, so that a result can be obtained. But in between deliberate measurements, we can arrange for decoherence to be so weak as to be negligible, at least for the duration of the experiment, so that the evolution is (almost) truly quantum. It's relatively easy for, say, single atoms at very low temperature, but it becomes harder and harder the bigger the system is (it is for example a well-known and very real hurdle to design quantum computers with enough qubits). In practice, gravity is not usually the limiting factor here, because it is such a weak interaction.
answered 31 mins ago
Luzanne
1,248417
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
5
down vote
Not every interaction is measurement or collapses the wave function. When light reflects off a mirror, the phase information is preserved. As each single photon hits the mirror and scatters on an electron, the photon doesn't hit the mirror in just one point or interacts with just one electron. Instead each single photon hits the entire mirror and interacts with all electrons in the mirror. In other words, due to the uncertainty principle, the interaction is a superposition of interactions with every electron in the mirror. This uncertainty preserves the wave function of the photon from collapsing.
The same concept applies to other collective processes, including the photon's travel through space, whether flat or curved by gravity. If the photon is allowed to take any trajectory, then the photon takes all of them simultaneously with different probabilities and therefore acts like a wave. In this case the photon's trajectory through space is a superposition of all possible trajectories. Therefore gravity does not collapse the photon's wave function (at least while away from black holes).
Furthermore, certain particles have a low probability of interaction, e.g. neutrinos that can fly through the universe as through a virtually empty space. Also, the hypothetical particles of dark matter may not nteract at all other than via gravity while the gravity interactions almost always would be a collective process described above that would not collapse the wave function.
Science is about predicting practical results. Your question however seems rather hypothetical. Whether the answer is yes or no, there seems to be no practical difference either way. Finally, quantum mechanics alone does not describe the universe as a whole. This requires quantum gravity to view spacetime as a function rather than a set of independent variables and effectively make this world a projection. Thus your question cannot be fully answered until quantum gravity has been developed.
answered 1 hour ago
safesphere
6,78611239
Can you clarify "due to the uncertainty principle.." This principle is normal taught within the context of measurement. What meaning are you giving to it here? thanks.
– Bruce Greetham
15 mins ago
add a comment |Â
up vote
5
down vote
Not every interaction is measurement or collapses the wave function. When light reflects off a mirror, the phase information is preserved. As each single photon hits the mirror and scatters on an electron, the photon doesn't hit the mirror in just one point or interacts with just one electron. Instead each single photon hits the entire mirror and interacts with all electrons in the mirror. In other words, due to the uncertainty principle, the interaction is a superposition of interactions with every electron in the mirror. This uncertainty preserves the wave function of the photon from collapsing.
The same concept applies to other collective processes, including the photon's travel through space, whether flat or curved by gravity. If the photon is allowed to take any trajectory, then the photon takes all of them simultaneously with different probabilities and therefore acts like a wave. In this case the photon's trajectory through space is a superposition of all possible trajectories. Therefore gravity does not collapse the photon's wave function (at least while away from black holes).
Furthermore, certain particles have a low probability of interaction, e.g. neutrinos that can fly through the universe as through a virtually empty space. Also, the hypothetical particles of dark matter may not nteract at all other than via gravity while the gravity interactions almost always would be a collective process described above that would not collapse the wave function.
Science is about predicting practical results. Your question however seems rather hypothetical. Whether the answer is yes or no, there seems to be no practical difference either way. Finally, quantum mechanics alone does not describe the universe as a whole. This requires quantum gravity to view spacetime as a function rather than a set of independent variables and effectively make this world a projection. Thus your question cannot be fully answered until quantum gravity has been developed.
answered 1 hour ago
safesphere
6,78611239
Can you clarify "due to the uncertainty principle.." This principle is normal taught within the context of measurement. What meaning are you giving to it here? thanks.
– Bruce Greetham
15 mins ago
add a comment |Â
up vote
5
down vote
up vote
5
down vote
Not every interaction is measurement or collapses the wave function. When light reflects off a mirror, the phase information is preserved. As each single photon hits the mirror and scatters on an electron, the photon doesn't hit the mirror in just one point or interacts with just one electron. Instead each single photon hits the entire mirror and interacts with all electrons in the mirror. In other words, due to the uncertainty principle, the interaction is a superposition of interactions with every electron in the mirror. This uncertainty preserves the wave function of the photon from collapsing.
The same concept applies to other collective processes, including the photon's travel through space, whether flat or curved by gravity. If the photon is allowed to take any trajectory, then the photon takes all of them simultaneously with different probabilities and therefore acts like a wave. In this case the photon's trajectory through space is a superposition of all possible trajectories. Therefore gravity does not collapse the photon's wave function (at least while away from black holes).
Furthermore, certain particles have a low probability of interaction, e.g. neutrinos that can fly through the universe as through a virtually empty space. Also, the hypothetical particles of dark matter may not nteract at all other than via gravity while the gravity interactions almost always would be a collective process described above that would not collapse the wave function.
Science is about predicting practical results. Your question however seems rather hypothetical. Whether the answer is yes or no, there seems to be no practical difference either way. Finally, quantum mechanics alone does not describe the universe as a whole. This requires quantum gravity to view spacetime as a function rather than a set of independent variables and effectively make this world a projection. Thus your question cannot be fully answered until quantum gravity has been developed.
answered 1 hour ago
safesphere
6,78611239
Not every interaction is measurement or collapses the wave function. When light reflects off a mirror, the phase information is preserved. As each single photon hits the mirror and scatters on an electron, the photon doesn't hit the mirror in just one point or interacts with just one electron. Instead each single photon hits the entire mirror and interacts with all electrons in the mirror. In other words, due to the uncertainty principle, the interaction is a superposition of interactions with every electron in the mirror. This uncertainty preserves the wave function of the photon from collapsing.
The same concept applies to other collective processes, including the photon's travel through space, whether flat or curved by gravity. If the photon is allowed to take any trajectory, then the photon takes all of them simultaneously with different probabilities and therefore acts like a wave. In this case the photon's trajectory through space is a superposition of all possible trajectories. Therefore gravity does not collapse the photon's wave function (at least while away from black holes).
Furthermore, certain particles have a low probability of interaction, e.g. neutrinos that can fly through the universe as through a virtually empty space. Also, the hypothetical particles of dark matter may not nteract at all other than via gravity while the gravity interactions almost always would be a collective process described above that would not collapse the wave function.
Science is about predicting practical results. Your question however seems rather hypothetical. Whether the answer is yes or no, there seems to be no practical difference either way. Finally, quantum mechanics alone does not describe the universe as a whole. This requires quantum gravity to view spacetime as a function rather than a set of independent variables and effectively make this world a projection. Thus your question cannot be fully answered until quantum gravity has been developed.
answered 1 hour ago
safesphere
6,78611239
answered 1 hour ago
safesphere
6,78611239
answered 1 hour ago
safesphere
6,78611239
answered 1 hour ago
safesphere
6,78611239
6,78611239
Can you clarify "due to the uncertainty principle.." This principle is normal taught within the context of measurement. What meaning are you giving to it here? thanks.
– Bruce Greetham
15 mins ago
add a comment |Â
Can you clarify "due to the uncertainty principle.." This principle is normal taught within the context of measurement. What meaning are you giving to it here? thanks.
– Bruce Greetham
15 mins ago
Can you clarify "due to the uncertainty principle.." This principle is normal taught within the context of measurement. What meaning are you giving to it here? thanks.
– Bruce Greetham
15 mins ago
Can you clarify "due to the uncertainty principle.." This principle is normal taught within the context of measurement. What meaning are you giving to it here? thanks.
– Bruce Greetham
15 mins ago
add a comment |Â
up vote
1
down vote
What you describe is the process known as decoherence: any interaction of a quantum system with its environment (e.g. with photons or other particles passing by, and, yes, most likely interacting through gravity, although we don't have a theory to fully describe this yet) has the potential to destroy its genuinely quantum nature, turning quantum superpositions into mere classical statistical ones. This process is indeed the first half of a measurement, the second half being the reading out of the result which resolves the remaining statistical superposition into a single result.
But decoherence is not an all or nothing, instantaneous process: it is progressive in time, and the weaker the interaction between a system and its environment, the slower it will decohere. When we actually do a measurement we deliberately arrange for the interaction to be strong enough and we wait long enough for full decoherence to occur, so that a result can be obtained. But in between deliberate measurements, we can arrange for decoherence to be so weak as to be negligible, at least for the duration of the experiment, so that the evolution is (almost) truly quantum. It's relatively easy for, say, single atoms at very low temperature, but it becomes harder and harder the bigger the system is (it is for example a well-known and very real hurdle to design quantum computers with enough qubits). In practice, gravity is not usually the limiting factor here, because it is such a weak interaction.
answered 31 mins ago
Luzanne
1,248417
add a comment |Â
up vote
1
down vote
What you describe is the process known as decoherence: any interaction of a quantum system with its environment (e.g. with photons or other particles passing by, and, yes, most likely interacting through gravity, although we don't have a theory to fully describe this yet) has the potential to destroy its genuinely quantum nature, turning quantum superpositions into mere classical statistical ones. This process is indeed the first half of a measurement, the second half being the reading out of the result which resolves the remaining statistical superposition into a single result.
But decoherence is not an all or nothing, instantaneous process: it is progressive in time, and the weaker the interaction between a system and its environment, the slower it will decohere. When we actually do a measurement we deliberately arrange for the interaction to be strong enough and we wait long enough for full decoherence to occur, so that a result can be obtained. But in between deliberate measurements, we can arrange for decoherence to be so weak as to be negligible, at least for the duration of the experiment, so that the evolution is (almost) truly quantum. It's relatively easy for, say, single atoms at very low temperature, but it becomes harder and harder the bigger the system is (it is for example a well-known and very real hurdle to design quantum computers with enough qubits). In practice, gravity is not usually the limiting factor here, because it is such a weak interaction.
answered 31 mins ago
Luzanne
1,248417
add a comment |Â
up vote
1
down vote
up vote
1
down vote
What you describe is the process known as decoherence: any interaction of a quantum system with its environment (e.g. with photons or other particles passing by, and, yes, most likely interacting through gravity, although we don't have a theory to fully describe this yet) has the potential to destroy its genuinely quantum nature, turning quantum superpositions into mere classical statistical ones. This process is indeed the first half of a measurement, the second half being the reading out of the result which resolves the remaining statistical superposition into a single result.
But decoherence is not an all or nothing, instantaneous process: it is progressive in time, and the weaker the interaction between a system and its environment, the slower it will decohere. When we actually do a measurement we deliberately arrange for the interaction to be strong enough and we wait long enough for full decoherence to occur, so that a result can be obtained. But in between deliberate measurements, we can arrange for decoherence to be so weak as to be negligible, at least for the duration of the experiment, so that the evolution is (almost) truly quantum. It's relatively easy for, say, single atoms at very low temperature, but it becomes harder and harder the bigger the system is (it is for example a well-known and very real hurdle to design quantum computers with enough qubits). In practice, gravity is not usually the limiting factor here, because it is such a weak interaction.
answered 31 mins ago
Luzanne
1,248417
What you describe is the process known as decoherence: any interaction of a quantum system with its environment (e.g. with photons or other particles passing by, and, yes, most likely interacting through gravity, although we don't have a theory to fully describe this yet) has the potential to destroy its genuinely quantum nature, turning quantum superpositions into mere classical statistical ones. This process is indeed the first half of a measurement, the second half being the reading out of the result which resolves the remaining statistical superposition into a single result.
But decoherence is not an all or nothing, instantaneous process: it is progressive in time, and the weaker the interaction between a system and its environment, the slower it will decohere. When we actually do a measurement we deliberately arrange for the interaction to be strong enough and we wait long enough for full decoherence to occur, so that a result can be obtained. But in between deliberate measurements, we can arrange for decoherence to be so weak as to be negligible, at least for the duration of the experiment, so that the evolution is (almost) truly quantum. It's relatively easy for, say, single atoms at very low temperature, but it becomes harder and harder the bigger the system is (it is for example a well-known and very real hurdle to design quantum computers with enough qubits). In practice, gravity is not usually the limiting factor here, because it is such a weak interaction.
answered 31 mins ago
Luzanne
1,248417
answered 31 mins ago
Luzanne
1,248417
answered 31 mins ago
Luzanne
1,248417
answered 31 mins ago
Luzanne
1,248417
1,248417
add a comment |Â
add a comment |Â
john doe is a new contributor. Be nice, and check out our Code of Conduct.
john doe is a new contributor. Be nice, and check out our Code of Conduct.
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Possible duplicate of What is the quantum mechanical definition of a measurement?
– Stéphane Rollandin
28 mins ago