6 ms·

We can create and observe doppler shift by making things move towards/away from us. Thus it is proven that if something is moving away from us, it will produce

We can create and observe doppler shift by making things move towards/away from us. Thus it is proven that if something is moving away from us, it will produce a redshift. In the absence of evidence that something else is causing the redshift, the assumption should be that it is a result of things moving away from us. As an obvious example, doppler shift often needs to be accounted for to communicate with spacecraft.

nilkn 2y ago
X causes Y does not mean that Y implies X. It’s reasonable to suspect X given Y and an absence of other such causal relations, but it’s not necessarily reasonable to spend decades building layers and layers of models that assume X at the most basic level.
- deleted 2y ago
  [deleted]
- ko27 2y ago
  You are not a making insightful point at all. Nothing in the world can guarantee you that "Y implies X", after all, we can be living in a simulation. Does that mean we should shutdown all scientific discussions by repeating what you stated? Of course not.
  - nilkn 2y ago
    Point out where I said we should “shutdown all scientific discussions.” You won’t be able to, and you will then realize how incredibly absurd what you just wrote is.
    - MichaelZuo 2y ago
      The parent is pointing out that the prior comment is literally meaningless, and self defeating too, since the same logic would apply to your own existence, or simulated existence. Including any possible words you could ever write. (As far as any other HN reader could ever perceive)
      - nilkn 2y ago
        Don’t you think jumping to a complete existential crisis over such a simple comment is a little extreme? That alone is a red flag that maybe dogma has taken over. No, nothing I wrote suggests one must shut down all scientific discussion or inquiry. No, it does not mean you cannot investigate X and its implications. No, it does not mean you cannot build speculative models on top of X. Yes, it does mean it’s important to be careful with language and avoid enshrining what is only an assumption as an unassailable fact of reality for generations.
        deleted 2y ago
        [deleted]
        MichaelZuo 2y ago
        Who said it’s a ‘complete existential crisis’? It’s just a fact of reality that no one else on HN can verify with certainty whether or not you are a genuine, bonafide, human being, especially online. Everyone who is engaging with you is just assuming you are.
        nilkn 2y ago
        I said that. If you thought I was wrong in that assertion, then all you had to do was stop questioning your entire existence here. The fact that you continued to do so lends credence to my assertion rather than refuting it.
        MichaelZuo 2y ago
        Who is ‘I’? If you mean ‘nilkn’, the presumably human created HN account ostensibly still operated by that same sole human being, writing their own thoughts down and not on behalf of other entities, then thanks for providing an excellent demonstration.
- treflop 2y ago
  Everyone knows this. But without looking at the direct rules of the system, this is the best you can do. It’s not like you can just open the source code of the universe. You observe and make a theory that explains the observations, then the theory holds at least until a new observation contradicts the theory. Is the current theory wrong? Maybe. But everything can be wrong and the world is always welcome to hear a new theory that completely explains all current observations. But to just say a theory is wrong without providing a completely explained new one adds nothing.
  - nilkn 2y ago
    Everybody knows it, but the principle is selectively applied. For instance, our observations imply both general relativity and quantum field theory are necessary to model various aspects of the world. That’s an example of a Y. The only known X that’s ever been discovered that can encompass all aspects of that Y at all energy levels is string theory. Yet we are rightly careful to assume string theory is correct and enshrine it into the core body of scientific consensus. That does not mean we cannot or should not investigate it or even theory build on top of it, but it does mean we should refrain from assuming it must be true just because nobody can find anything better.
    - bumby 2y ago
      >but it does mean we should refrain from assuming it must be true just because nobody can find anything better. The vast majority of science is not disproving a theory but adding nuance to it. Newtonian physics wasn't disproven by quantum physics, but quantum physics showed that Newtonian physics has limitations as a model. It's not unreasonable to assume our best model is true until there is a reasonable amount of data to the contrary. As others have said, your point adds little to the conversation until you bring good data to the argument.
      - nilkn 2y ago
        I don’t accept that I owe anyone any kind of additional data on any of this. Just like I don’t have to have a proven solution to the problem of finding a theory of everything to suggest that string theory may not be the truth of the universe while still acknowledging that it can be a worthwhile thread of inquiry and study. Suggesting that we avoid possible dogma has intrinsic value. Let us step back and consider the fact that the combination of general relativity and the Standard Model already cannot explain our most basic cosmological observations. We cannot explain the stability of even our own galaxy based on current models. This situation clearly calls for some basic caution before we enshrine possible unproven explanations into humanity’s view of the universe. There’s a lot of evidence, both long established and newly growing, which shows that our models can’t consistently explain many of the basic things we see around us when we look up at the sky.
- exe34 2y ago
  I think everybody would be happy if you came up with a different explanation! what's happened so far is that we have a known mechanism, and no alternative explanations have worked yet.
- dotnet00 2y ago
  If we can suspect X given Y, but we shouldn't build models on top of the assumption of X, then what are we supposed to do with Y? To me it seems like you're arguing that it was a bad idea to build on the assumption of Newton's theory of gravity because eventually it would be replaced by Einstein's theories of relativity. Which is obviously not sensible, since Einstein's theories were in part the result of trying to explain inaccurate predictions made by building on Newton's theory.
- SkyBelow 2y ago
  >but it’s not necessarily reasonable to spend decades building layers and layers of models that assume X at the most basic level. If the only option for finding out better evidence for or against X is by building those models and watching them either keep matching observations or finding a contradiction that can lead to the downfall of X as the suspect, then it is if you want to progress science any further. Maybe there is another area that will give results faster, but much of the easy and fast science has already been science. And if someone finds a better option we missed, which does happen from time to time, add some rigor to it, verify it with testing, and they'll likely have themselves a Nobel prize.
narfay 2y ago
This is wrong on several levels: 1. As other commenter said, X causes Y does not mean that Y implies X. There can be another cause for the Doppler. And surprisingly, 2. There is at least one known mechanism that cause Doppler WITHOUT moving: when the observer is in a gravity well (ex: earth) and observing a stationary object outside the gravity well (ex: some fixed point in outer space)
- dotnet00 2y ago
  As I've mentioned in another post, that leads to questioning one of the most well tested theories in physics, so you need extraordinary evidence to prove it over something as elementary as doppler shift. Like, if it's Earth's gravity well causing us to see things differently, then things that are further from Earth should observe things differently.
  - narfay 2y ago
    There is already extraordinary evidence that something in physics is behaving differently at larger scales: the behavior of galaxies (spin, gravity pull) doesn't match their mass. Any mass. There is no single mass value that predicts their entire behavior correctly. Thus dark matter, dark energy etc competing theories, which are so far untestable. It wouldn't surprise me if we discover someday another Doppler mechanism that occurs at those same large scales
- pdonis 2y ago
  > There is at least one known mechanism that cause Doppler WITHOUT moving: when the observer is in a gravity well This is gravitational redshift, not Doppler shift. Doppler shift specifically means redshift due to an object moving away--but to really be correct that definition has to be limited to flat spacetime, or to a small enough region in a curved spacetime that the curvature can be ignored.
pdonis 2y ago
> In the absence of evidence that something else is causing the redshift, the assumption should be that it is a result of things moving away from us. But that is not what our best current model of the universe actually says. Our best current model of the universe says that the observed redshift of a distant object tells us by what factor the universe expanded between the time the light was emitted and now (when we see the light). Viewing it as a Doppler shift is an approximation that only works for small redshifts (much less than 1).

nilkn 2y ago

X causes Y does not mean that Y implies X. It’s reasonable to suspect X given Y and an absence of other such causal relations, but it’s not necessarily reasonable to spend decades building layers and layers of models that assume X at the most basic level.

deleted 2y ago
[deleted]
ko27 2y ago
You are not a making insightful point at all. Nothing in the world can guarantee you that "Y implies X", after all, we can be living in a simulation. Does that mean we should shutdown all scientific discussions by repeating what you stated? Of course not.
- nilkn 2y ago
  Point out where I said we should “shutdown all scientific discussions.” You won’t be able to, and you will then realize how incredibly absurd what you just wrote is.
  - MichaelZuo 2y ago
    The parent is pointing out that the prior comment is literally meaningless, and self defeating too, since the same logic would apply to your own existence, or simulated existence. Including any possible words you could ever write. (As far as any other HN reader could ever perceive)
    - nilkn 2y ago
      Don’t you think jumping to a complete existential crisis over such a simple comment is a little extreme? That alone is a red flag that maybe dogma has taken over. No, nothing I wrote suggests one must shut down all scientific discussion or inquiry. No, it does not mean you cannot investigate X and its implications. No, it does not mean you cannot build speculative models on top of X. Yes, it does mean it’s important to be careful with language and avoid enshrining what is only an assumption as an unassailable fact of reality for generations.
      - deleted 2y ago
        [deleted]
      - MichaelZuo 2y ago
        Who said it’s a ‘complete existential crisis’? It’s just a fact of reality that no one else on HN can verify with certainty whether or not you are a genuine, bonafide, human being, especially online. Everyone who is engaging with you is just assuming you are.
        nilkn 2y ago
        I said that. If you thought I was wrong in that assertion, then all you had to do was stop questioning your entire existence here. The fact that you continued to do so lends credence to my assertion rather than refuting it.
        MichaelZuo 2y ago
        Who is ‘I’? If you mean ‘nilkn’, the presumably human created HN account ostensibly still operated by that same sole human being, writing their own thoughts down and not on behalf of other entities, then thanks for providing an excellent demonstration.
treflop 2y ago
Everyone knows this. But without looking at the direct rules of the system, this is the best you can do. It’s not like you can just open the source code of the universe. You observe and make a theory that explains the observations, then the theory holds at least until a new observation contradicts the theory. Is the current theory wrong? Maybe. But everything can be wrong and the world is always welcome to hear a new theory that completely explains all current observations. But to just say a theory is wrong without providing a completely explained new one adds nothing.
- nilkn 2y ago
  Everybody knows it, but the principle is selectively applied. For instance, our observations imply both general relativity and quantum field theory are necessary to model various aspects of the world. That’s an example of a Y. The only known X that’s ever been discovered that can encompass all aspects of that Y at all energy levels is string theory. Yet we are rightly careful to assume string theory is correct and enshrine it into the core body of scientific consensus. That does not mean we cannot or should not investigate it or even theory build on top of it, but it does mean we should refrain from assuming it must be true just because nobody can find anything better.
  - bumby 2y ago
    >but it does mean we should refrain from assuming it must be true just because nobody can find anything better. The vast majority of science is not disproving a theory but adding nuance to it. Newtonian physics wasn't disproven by quantum physics, but quantum physics showed that Newtonian physics has limitations as a model. It's not unreasonable to assume our best model is true until there is a reasonable amount of data to the contrary. As others have said, your point adds little to the conversation until you bring good data to the argument.
    - nilkn 2y ago
      I don’t accept that I owe anyone any kind of additional data on any of this. Just like I don’t have to have a proven solution to the problem of finding a theory of everything to suggest that string theory may not be the truth of the universe while still acknowledging that it can be a worthwhile thread of inquiry and study. Suggesting that we avoid possible dogma has intrinsic value. Let us step back and consider the fact that the combination of general relativity and the Standard Model already cannot explain our most basic cosmological observations. We cannot explain the stability of even our own galaxy based on current models. This situation clearly calls for some basic caution before we enshrine possible unproven explanations into humanity’s view of the universe. There’s a lot of evidence, both long established and newly growing, which shows that our models can’t consistently explain many of the basic things we see around us when we look up at the sky.
exe34 2y ago
I think everybody would be happy if you came up with a different explanation! what's happened so far is that we have a known mechanism, and no alternative explanations have worked yet.
dotnet00 2y ago
If we can suspect X given Y, but we shouldn't build models on top of the assumption of X, then what are we supposed to do with Y? To me it seems like you're arguing that it was a bad idea to build on the assumption of Newton's theory of gravity because eventually it would be replaced by Einstein's theories of relativity. Which is obviously not sensible, since Einstein's theories were in part the result of trying to explain inaccurate predictions made by building on Newton's theory.
SkyBelow 2y ago
>but it’s not necessarily reasonable to spend decades building layers and layers of models that assume X at the most basic level. If the only option for finding out better evidence for or against X is by building those models and watching them either keep matching observations or finding a contradiction that can lead to the downfall of X as the suspect, then it is if you want to progress science any further. Maybe there is another area that will give results faster, but much of the easy and fast science has already been science. And if someone finds a better option we missed, which does happen from time to time, add some rigor to it, verify it with testing, and they'll likely have themselves a Nobel prize.

narfay 2y ago

This is wrong on several levels: 1. As other commenter said, X causes Y does not mean that Y implies X. There can be another cause for the Doppler. And surprisingly, 2. There is at least one known mechanism that cause Doppler WITHOUT moving: when the observer is in a gravity well (ex: earth) and observing a stationary object outside the gravity well (ex: some fixed point in outer space)

dotnet00 2y ago
As I've mentioned in another post, that leads to questioning one of the most well tested theories in physics, so you need extraordinary evidence to prove it over something as elementary as doppler shift. Like, if it's Earth's gravity well causing us to see things differently, then things that are further from Earth should observe things differently.
- narfay 2y ago
  There is already extraordinary evidence that something in physics is behaving differently at larger scales: the behavior of galaxies (spin, gravity pull) doesn't match their mass. Any mass. There is no single mass value that predicts their entire behavior correctly. Thus dark matter, dark energy etc competing theories, which are so far untestable. It wouldn't surprise me if we discover someday another Doppler mechanism that occurs at those same large scales
pdonis 2y ago
> There is at least one known mechanism that cause Doppler WITHOUT moving: when the observer is in a gravity well This is gravitational redshift, not Doppler shift. Doppler shift specifically means redshift due to an object moving away--but to really be correct that definition has to be limited to flat spacetime, or to a small enough region in a curved spacetime that the curvature can be ignored.

pdonis 2y ago

> In the absence of evidence that something else is causing the redshift, the assumption should be that it is a result of things moving away from us. But that is not what our best current model of the universe actually says. Our best current model of the universe says that the observed redshift of a distant object tells us by what factor the universe expanded between the time the light was emitted and now (when we see the light). Viewing it as a Doppler shift is an approximation that only works for small redshifts (much less than 1).