6 ms·

They probably do change, but extremely slowly. It would feel strange if there were something fixed in the universe.

bitmasher9 2y ago
If they changed in a way to have meaningful impacts on how astronomical bodies operate we should be able to observe the change as some of the oldest light we observe is billions of years older than the newest light. In fact, based on this we can tell that the fundamental constant the speed of light has not changed which I agree is very strange.
- vl 2y ago
  It comes down to what time is. I.e. what was before the Big Bang? If time didn’t exist before big bang, then speed of light emerged after big bang, and as such “changed”.
psychoslave 2y ago
Either there is some unversal constants, or everything constantly change.
- hughesjj 2y ago
  Could be both. Some things determined by some mathematical constraints will always be followed. Ex things like group theory and statistics will always be followed by any object subject to them, but how that manifests if the objects those rules act upon changes in form
kimixa 2y ago
Why would it be "strange"? What reference can we possibly use to compare? This sort of thing tends to be so far from "common sense" it probably doesn't make sense to try to reason about it from that perspective.
- gus_massa 2y ago
  It's possible to measure the ratios of the constants, like mass_of_proton/mass_of_electron . Another is the fine structure constant, that is related to the charge of the electron (divided by a lot of other constants to cancel the units). Both of them are related to the spectral lines of the light emitted and absorbed by atoms, so if they changed the "color" of the other galaxies should have changed a little. https://en.wikipedia.org/wiki/Dimensionless_physical_constant#Examples https://en.wikipedia.org/wiki/Dimensionless_physical_constan...
  - freeone3000 2y ago
    I know nothing about this: what if the color did change, to be slightly redder?
    - ForOldHack 2y ago
      Then we ( and Hubble ) may over estimate the speed of the expansion of the universe, an the galaxies that we have measured their red shift and estimated their relitive speed based on less of a red shift. It is certainly possible.
    - gus_massa 2y ago
      I don't remember the details, but I took a look at Wikipedia to remember some details. The redshift of far away galaxies is calculated multiplying the frequencies by 1+z, so you get the same displacement if you draw the spectrum in the correct logarithmic scale https://en.wikipedia.org/wiki/Redshift https://en.wikipedia.org/wiki/Redshift The emission/absorption lines of Hydrogen are calculated using the Rydberg constant https://en.wikipedia.org/wiki/Rydberg_constant https://en.wikipedia.org/wiki/Rydberg_constant that use the mass of the electron. But it's not the actual mass of an isolated electron, you must use the "reduced mass" because the electron moves around the proton but the proton also moves a little [1]. So the reduced mass of the electron is reduced_mass_electron = 1 / ( 1 / actual_mass_electron + 1 / actual_mass_proton ) The proton is much heavier [2], so the difference of the reduced and the actual mass of the electron is only .1%. If you magically change the mass of the electron to be equal to the mass of the proton, then the reduced mass of the electron would be 1/(1/1+1/1)=1/2 of the actual mass of the magical electron, and all the lines in the spectrum of Hydrogen will change. But the spectrum astronomer get includes other elements and isotopes. For example Deuterium that has the same charge but the double of mass. In the real word, the reduced mass of the electron in Deuterium is also almost equal to the actual mass of the electron, the difference is like .05%. In the magical world where the mass of the electron to be equal to the mass of the proton, then the reduced mass of the electron would be 1/(1/1+1/2)=1/3 of the actual mass of the magical electron, and all the lines in the spectrum of Deuterium will change but in a different way. I think it's possible to see all these lines in a spectrum, but to be sure ask an expert. Anyway, a magical change to make the mass of protons and electrons equal will change the spectrum of all the other atoms in different and strange and weird and unexpected ways. [3] So it will be easy to spot. Smaller changes will change thing and be visible too, unless they are too small. [1] If you want to go down the Quantum Mechanics rabbit hole, they don't move and you must use orbitals. But the correction is the same than in the fake/simplified classical calculation. [2] * massive [3] A heavy [2] electron is very similar to a muon, and in Hydrogen molecules with muons both Hydrogen are very close so you get fusion reactions https://en.wikipedia.org/wiki/Muon-catalyzed_fusion https://en.wikipedia.org/wiki/Muon-catalyzed_fusion so the magical would be very strange.
jjeaff 2y ago
this is a bit tangential, but I once had a physics professor describe light waves as standing still and everything else is just moving around it.
- Vecr 2y ago
  It's kind of silly to take the perspective of light, because it doesn't experience time (obviously, but you know what I mean). Maybe there will be new physics on that like there was with neutrinos, but it can't be too much of an effect.
  - bluGill 2y ago
    > it can't be too much of an effect. That is the problem with any argument for some new physics - it might exist, but it can't have much effect or we would detect it. Generally I only see people arguing for new physics because they really want faster than light travel (typically also without all the weird time effects, but a small minority would accept it with time effects)
    - Vecr 2y ago
      Also many people want to find libertarian free will somewhere in new physics.
  - mystified5016 2y ago
    In case anyone else is curious about this fact: it has to do with time dilation. As your velocity through space approaches c, your velocity through time approaches zero. Since photons move at c, they experience zero time between creation and destruction.
    - thehappypm 2y ago
      This implies a paradox: what if a photon is emitted such that it does not ever get destroyed? Fired into a void of deep space?
shagie 2y ago
The fossil reactor at Oklo https://apod.nasa.gov/apod/ap100912.html https://apod.nasa.gov/apod/ap100912.html and https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto... can be used for that question. From Wikipedia: The natural reactor of Oklo has been used to check if the atomic fine-structure constant α might have changed over the past 2 billion years. That is because α influences the rate of various nuclear reactions. For example, ¹⁴⁹Sm captures a neutron to become ¹⁵⁰Sm, and since the rate of neutron capture depends on the value of α, the ratio of the two samarium isotopes in samples from Oklo can be used to calculate the value of α from 2 billion years ago. Several studies have analysed the relative concentrations of radioactive isotopes left behind at Oklo, and most have concluded that nuclear reactions then were much the same as they are today, which implies that α was the same too.
- User23 2y ago
  Is there a good explanation of how that isn’t just measuring the expansion and contraction of a ruler with itself? Don’t we know the reactor is 2 billion years old because of radio dating?
  - Vecr 2y ago
    It would be somewhat hard to tell if there's circularity somewhere, but you should be able to date it somewhat with the quantity of oxygen in the atmosphere at various times and general geological processes.
  - AstralStorm 2y ago
    Well, it's dated against pulsars and stars. But those sources of information have a bit of an error bar on time-space distance. Which is why a synthetic clock is needed here. That will have a known inception date and the changes if any can be compared. The problem with both is they're not exactly fully closed systems anyway so there will be some margin of error ever with the length of the operation. And during the test, we might just find out something completely unaccounted for in current physics... That isn't a universal constant related at all.
  - 2y ago
adrian_b 2y ago
Most so called fundamental constants appear in the relationships between physical quantities only as a consequence of choosing arbitrary units. It is possible to eliminate almost all fundamental constants by choosing so-called natural units for the base physical quantities, for instance the elementary charge as the unit of electric charge. For all fundamental constants that can be eliminated by choosing natural units it makes no sense to discuss about changes of them. Nevertheless, even when a natural system of units is used, there remain 2 fundamental constants (plus a few other fundamental constants that are used only in certain parts of quantum field theory). The 2 important fundamental constants that cannot be eliminated are the Newtonian constant of gravitation, which is a measure of the intensity of the gravitational interaction, and a second fundamental constant that is a measure of the intensity of the electromagnetic interaction, which is frequently expressed as the so-called constant of the fine structure. The meaning of the constant of the fine structure is that it is the ratio between the speed of light in vacuum and the speed of a charged particle with unit charge, like an electron, that rotates around another charged particle with unit charge, which is much heavier, like a nucleus, in the state with the lowest possible energy, i.e. like the ground state of a hydrogen atom, but where the nucleus would have infinite mass. The speed of the rotating particle is a measure of the strength of the electromagnetic interaction between two elementary charges. So the only fundamental constants for which there could be a evolution in time are those that characterize the strengths of the electromagnetic interaction and of the gravitational interaction (and also the fundamental constants that characterize the strengths of the nuclear strong interactions and nuclear weak interactions). The values of these fundamental constants that characterize the strengths of the different kinds of interactions determine the structure of the Universe, where the quarks are bound into nucleons, the nucleons are bound into nuclei, the nuclei are bound into atoms, the atoms are bound into molecules, the molecules are bound into solid or fluid bodies, which are bound by gravitation into big celestial bodies, then into stellar systems, then into galaxies, then into groups of galaxies. Any changes in the strengths of the fundamental interactions would lead to dramatic changes in the structure of matter, which are not seen even in the distant galaxies. So any changes in time of the true fundamental constants are very unlikely, while changes in the constants that appear as a consequence of choosing arbitrary units are not possible (because such fundamental constants are fixed by conventions, e.g. by saying that the speed of light in vacuum is 299,792,458 m/s).
__MatrixMan__ 2y ago
If nothing remains constant then there's no identifying feature to point at and conclude that my experience yesterday and my experience today occurred in the same universe. Surely that feels even weirder than letting there be something that can be used as primary key for universe identification.

If they changed in a way to have meaningful impacts on how astronomical bodies operate we should be able to observe the change as some of the oldest light we observe is billions of years older than the newest light. In fact, based on this we can tell that the fundamental constant the speed of light has not changed which I agree is very strange.

vl 2y ago
It comes down to what time is. I.e. what was before the Big Bang? If time didn’t exist before big bang, then speed of light emerged after big bang, and as such “changed”.

psychoslave 2y ago

Either there is some unversal constants, or everything constantly change.

hughesjj 2y ago
Could be both. Some things determined by some mathematical constraints will always be followed. Ex things like group theory and statistics will always be followed by any object subject to them, but how that manifests if the objects those rules act upon changes in form

kimixa 2y ago

Why would it be "strange"? What reference can we possibly use to compare? This sort of thing tends to be so far from "common sense" it probably doesn't make sense to try to reason about it from that perspective.

gus_massa 2y ago
It's possible to measure the ratios of the constants, like mass_of_proton/mass_of_electron . Another is the fine structure constant, that is related to the charge of the electron (divided by a lot of other constants to cancel the units). Both of them are related to the spectral lines of the light emitted and absorbed by atoms, so if they changed the "color" of the other galaxies should have changed a little. https://en.wikipedia.org/wiki/Dimensionless_physical_constant#Examples https://en.wikipedia.org/wiki/Dimensionless_physical_constan...
- freeone3000 2y ago
  I know nothing about this: what if the color did change, to be slightly redder?
  - ForOldHack 2y ago
    Then we ( and Hubble ) may over estimate the speed of the expansion of the universe, an the galaxies that we have measured their red shift and estimated their relitive speed based on less of a red shift. It is certainly possible.
  - gus_massa 2y ago
    I don't remember the details, but I took a look at Wikipedia to remember some details. The redshift of far away galaxies is calculated multiplying the frequencies by 1+z, so you get the same displacement if you draw the spectrum in the correct logarithmic scale https://en.wikipedia.org/wiki/Redshift https://en.wikipedia.org/wiki/Redshift The emission/absorption lines of Hydrogen are calculated using the Rydberg constant https://en.wikipedia.org/wiki/Rydberg_constant https://en.wikipedia.org/wiki/Rydberg_constant that use the mass of the electron. But it's not the actual mass of an isolated electron, you must use the "reduced mass" because the electron moves around the proton but the proton also moves a little [1]. So the reduced mass of the electron is reduced_mass_electron = 1 / ( 1 / actual_mass_electron + 1 / actual_mass_proton ) The proton is much heavier [2], so the difference of the reduced and the actual mass of the electron is only .1%. If you magically change the mass of the electron to be equal to the mass of the proton, then the reduced mass of the electron would be 1/(1/1+1/1)=1/2 of the actual mass of the magical electron, and all the lines in the spectrum of Hydrogen will change. But the spectrum astronomer get includes other elements and isotopes. For example Deuterium that has the same charge but the double of mass. In the real word, the reduced mass of the electron in Deuterium is also almost equal to the actual mass of the electron, the difference is like .05%. In the magical world where the mass of the electron to be equal to the mass of the proton, then the reduced mass of the electron would be 1/(1/1+1/2)=1/3 of the actual mass of the magical electron, and all the lines in the spectrum of Deuterium will change but in a different way. I think it's possible to see all these lines in a spectrum, but to be sure ask an expert. Anyway, a magical change to make the mass of protons and electrons equal will change the spectrum of all the other atoms in different and strange and weird and unexpected ways. [3] So it will be easy to spot. Smaller changes will change thing and be visible too, unless they are too small. [1] If you want to go down the Quantum Mechanics rabbit hole, they don't move and you must use orbitals. But the correction is the same than in the fake/simplified classical calculation. [2] * massive [3] A heavy [2] electron is very similar to a muon, and in Hydrogen molecules with muons both Hydrogen are very close so you get fusion reactions https://en.wikipedia.org/wiki/Muon-catalyzed_fusion https://en.wikipedia.org/wiki/Muon-catalyzed_fusion so the magical would be very strange.

jjeaff 2y ago

this is a bit tangential, but I once had a physics professor describe light waves as standing still and everything else is just moving around it.

Vecr 2y ago
It's kind of silly to take the perspective of light, because it doesn't experience time (obviously, but you know what I mean). Maybe there will be new physics on that like there was with neutrinos, but it can't be too much of an effect.
- bluGill 2y ago
  > it can't be too much of an effect. That is the problem with any argument for some new physics - it might exist, but it can't have much effect or we would detect it. Generally I only see people arguing for new physics because they really want faster than light travel (typically also without all the weird time effects, but a small minority would accept it with time effects)
  - Vecr 2y ago
    Also many people want to find libertarian free will somewhere in new physics.
- mystified5016 2y ago
  In case anyone else is curious about this fact: it has to do with time dilation. As your velocity through space approaches c, your velocity through time approaches zero. Since photons move at c, they experience zero time between creation and destruction.
  - thehappypm 2y ago
    This implies a paradox: what if a photon is emitted such that it does not ever get destroyed? Fired into a void of deep space?

shagie 2y ago

The fossil reactor at Oklo https://apod.nasa.gov/apod/ap100912.html https://apod.nasa.gov/apod/ap100912.html and https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto... can be used for that question. From Wikipedia: The natural reactor of Oklo has been used to check if the atomic fine-structure constant α might have changed over the past 2 billion years. That is because α influences the rate of various nuclear reactions. For example, ¹⁴⁹Sm captures a neutron to become ¹⁵⁰Sm, and since the rate of neutron capture depends on the value of α, the ratio of the two samarium isotopes in samples from Oklo can be used to calculate the value of α from 2 billion years ago. Several studies have analysed the relative concentrations of radioactive isotopes left behind at Oklo, and most have concluded that nuclear reactions then were much the same as they are today, which implies that α was the same too.

User23 2y ago
Is there a good explanation of how that isn’t just measuring the expansion and contraction of a ruler with itself? Don’t we know the reactor is 2 billion years old because of radio dating?
- Vecr 2y ago
  It would be somewhat hard to tell if there's circularity somewhere, but you should be able to date it somewhat with the quantity of oxygen in the atmosphere at various times and general geological processes.
- AstralStorm 2y ago
  Well, it's dated against pulsars and stars. But those sources of information have a bit of an error bar on time-space distance. Which is why a synthetic clock is needed here. That will have a known inception date and the changes if any can be compared. The problem with both is they're not exactly fully closed systems anyway so there will be some margin of error ever with the length of the operation. And during the test, we might just find out something completely unaccounted for in current physics... That isn't a universal constant related at all.
- 2y ago

adrian_b 2y ago

Most so called fundamental constants appear in the relationships between physical quantities only as a consequence of choosing arbitrary units. It is possible to eliminate almost all fundamental constants by choosing so-called natural units for the base physical quantities, for instance the elementary charge as the unit of electric charge. For all fundamental constants that can be eliminated by choosing natural units it makes no sense to discuss about changes of them. Nevertheless, even when a natural system of units is used, there remain 2 fundamental constants (plus a few other fundamental constants that are used only in certain parts of quantum field theory). The 2 important fundamental constants that cannot be eliminated are the Newtonian constant of gravitation, which is a measure of the intensity of the gravitational interaction, and a second fundamental constant that is a measure of the intensity of the electromagnetic interaction, which is frequently expressed as the so-called constant of the fine structure. The meaning of the constant of the fine structure is that it is the ratio between the speed of light in vacuum and the speed of a charged particle with unit charge, like an electron, that rotates around another charged particle with unit charge, which is much heavier, like a nucleus, in the state with the lowest possible energy, i.e. like the ground state of a hydrogen atom, but where the nucleus would have infinite mass. The speed of the rotating particle is a measure of the strength of the electromagnetic interaction between two elementary charges. So the only fundamental constants for which there could be a evolution in time are those that characterize the strengths of the electromagnetic interaction and of the gravitational interaction (and also the fundamental constants that characterize the strengths of the nuclear strong interactions and nuclear weak interactions). The values of these fundamental constants that characterize the strengths of the different kinds of interactions determine the structure of the Universe, where the quarks are bound into nucleons, the nucleons are bound into nuclei, the nuclei are bound into atoms, the atoms are bound into molecules, the molecules are bound into solid or fluid bodies, which are bound by gravitation into big celestial bodies, then into stellar systems, then into galaxies, then into groups of galaxies. Any changes in the strengths of the fundamental interactions would lead to dramatic changes in the structure of matter, which are not seen even in the distant galaxies. So any changes in time of the true fundamental constants are very unlikely, while changes in the constants that appear as a consequence of choosing arbitrary units are not possible (because such fundamental constants are fixed by conventions, e.g. by saying that the speed of light in vacuum is 299,792,458 m/s).

__MatrixMan__ 2y ago

If nothing remains constant then there's no identifying feature to point at and conclude that my experience yesterday and my experience today occurred in the same universe. Surely that feels even weirder than letting there be something that can be used as primary key for universe identification.