11 ms·

Why would distance from earth influence the speed of expansion of a distant galaxy? Does that suggest that our awareness of the galactic bodies itself is someh

Why would distance from earth influence the speed of expansion of a distant galaxy? Does that suggest that our awareness of the galactic bodies itself is somehow influencing them, as in the double-slit experiment?

deleted 3y ago
[deleted]
itronitron 3y ago
It's distance between any two points, however the distance measuring techniques to which we have access can only be performed by astronomers on Earth. Hence, one of those points will be Earth.
- Turing_Machine 3y ago
  Right. A common analogy is the dough for a loaf of raisin bread. Consider the raisins on the surface of the dough. Pick one raisin to be your point of view (analogous to Earth, in this case). If the dough rises and expands from (say) 50 cm to 100 cm in diameter, another raisin adjacent the "Earth" raisin won't move very much, but the distance to a raisin at the diametrically opposed point will increase from about 78 cm to about 157 cm. The distant raisin will thus appear to be moving at a higher velocity than the adjacent raisin.
  - itronitron 3y ago
    I feel like that analogy should be included anytime someone mentions that things further away from us are moving away faster than things not as far away. My intuition of 'things far away moving away faster' causes me to conclude that things far away are therefore accelerating, because the more they move away the faster they move away, but my intuition is probably wrong as it doesn't line up with the raisin bread analogy.
anon25783 3y ago
At any point in space, a celestial object at distance d will tend to appear to move away from you faster than an object at a distance less than d. The only thing special about the Earth here is that it happens to be where we live.
317070 3y ago
> our awareness of the galactic bodies itself is somehow influencing them, as in the double-slit experiment In the double slit experiment, the awareness is not influencing the outcome. The act of measuring is. Pretty sure the act of measuring the galactic bodies has no impact on them in any meaningful way.
- I_Am_Nous 3y ago
  No, but there is a cool blending of the two concepts when light is bent by large gravity wells so that it actually shows the same star multiple times. When we observe which copied star "produced" a certain photon, it technically collapses the quantum possibilities backwards in time as that photon was emitted potentially billions of years ago.
  - rightbyte 3y ago
    > it technically collapses the quantum possibilities backwards in time as that photon was emitted potentially billions of years ago There is no way to verify that. Big parts of quantum physics is more or less pseudoscience.
    - I_Am_Nous 3y ago
      Perhaps it could be verified using time delayed lensing experiments[1]? 1. https://www.nature.com/articles/s41550-021-01450-9 https://www.nature.com/articles/s41550-021-01450-9
      - rightbyte 3y ago
        Seems like measuring "bending" of light, rather? But honestly I am not really qualified to say anything about astronomy.
        I_Am_Nous 3y ago
        In this case it's light bending around a gravity well which produces multiple "copies" of the star, but the light from each copy arrives at different points in time. So they could capture the light and attempt to capture the "same" light again later to try to verify or change the result they received. I did some more reading about it after posting, and the original experiment was intended to test if light "chooses" to be a wave OR a particle in a way they could affect, and that it could only be one or the other at a time. The truth seems to be more that it acts as both at the same time and whatever sensor equipment you use to pick it up is what it acts like.
M2Ys4U 3y ago
> Why would distance from earth influence the speed of expansion of a distant galaxy? It wouldn't - but it may influence how we measure distance. If we're using the wrong distance measurements then we're calculating the speed of expansion incorrectly.
cwmma 3y ago
no it's because space itself is expanding which causes things more distant from each other to be moving away from each other faster, the wikipedia article about hubbles law has a graphic illustrating the priciple with bread https://en.wikipedia.org/wiki/Hubble%27s_law https://en.wikipedia.org/wiki/Hubble%27s_law
- edgyquant 3y ago
  Wikipedia is not a proper source and I’ve no idea why people stopped considering this and now use it as such. The graphic may be fine, but provide a real source when pushing back against another commenter.
  - johndunne 3y ago
    To be fair to Wikipedia, it’s come on a long way since its early days when anyone could make whatever edits they wanted. The most popular entries on the site are very well vetted, though not perfect. Just my 2 cents.
  - zlg_codes 3y ago
    Pages contain other sources, however, which makes WP a good place to begin research on a topic. This place isn't debate club and nobody's getting a prize for winning an Internet argument.
    - edgyquant 3y ago
      No they don’t. Wikipedia pages, according to their own rules, contain secondary sources.
deleted 3y ago
[deleted]
gizmo686 3y ago
This observation is the reason we think the universe is expanding. As an analogy, consider the 2 dimensional surface on the surface of a balloon. As you inflate the balloon, the distance between any 2 points increases, and it increases more the farther away the points are from each other.
Udo 3y ago
> Does that suggest that our awareness of the galactic bodies itself is somehow influencing them, as in the double-slit experiment? "Awareness" is not a thing, not even in the double slit experiment. The term 'measurement' refers to a specific kind of interaction that bridges quantum systems with classical systems, although I believe a good case could be made that these waveforms never actually fully collapse. Likewise, if there is anything special about Earth's position in the greater cosmos, it would be a trick of perspective or perception - unless there are any completely disruptive new discoveries about the nature of reality. However, my money would be on the fact that the universe is simply not as uniform as we thought.
chongli 3y ago
Galaxies themselves aren't expanding, they're gravitationally bound. Galaxies are moving apart from one another, however. The issue is that not all galaxies are moving away from us. The ones that are closer to us have a lot of peculiar velocity [1]. This means they can be moving toward us or moving tangentially to us or any other direction. If we want to characterize the expansion of the universe as a whole, we need to account for this in our models. It turns out to be a lot more complicated than we previously thought. The crisis in cosmology (aka the Hubble tension [2]) is that our two means of characterizing the expansion of the universe, models of the cosmic microwave background (CMB) and measurements on the cosmic distance ladder using standard candles (Cepheid variables [3] for up-close measurements, Type Ia supernovae [4] for more distant measurements) disagree with one another, and that disagreement is getting worse, not converging. [1] https://en.wikipedia.org/wiki/Peculiar_velocity#Cosmology https://en.wikipedia.org/wiki/Peculiar_velocity#Cosmology [2] https://en.wikipedia.org/wiki/Hubble%27s_law#Hubble_tension https://en.wikipedia.org/wiki/Hubble%27s_law#Hubble_tension [3] https://en.wikipedia.org/wiki/Cepheid_variable https://en.wikipedia.org/wiki/Cepheid_variable [4] https://en.wikipedia.org/wiki/Type_Ia_supernova https://en.wikipedia.org/wiki/Type_Ia_supernova
sesm 3y ago
One alternative explanation is that the expansion of the universe is slowing down.

deleted 3y ago

[deleted]

itronitron 3y ago

It's distance between any two points, however the distance measuring techniques to which we have access can only be performed by astronomers on Earth. Hence, one of those points will be Earth.

Turing_Machine 3y ago
Right. A common analogy is the dough for a loaf of raisin bread. Consider the raisins on the surface of the dough. Pick one raisin to be your point of view (analogous to Earth, in this case). If the dough rises and expands from (say) 50 cm to 100 cm in diameter, another raisin adjacent the "Earth" raisin won't move very much, but the distance to a raisin at the diametrically opposed point will increase from about 78 cm to about 157 cm. The distant raisin will thus appear to be moving at a higher velocity than the adjacent raisin.
- itronitron 3y ago
  I feel like that analogy should be included anytime someone mentions that things further away from us are moving away faster than things not as far away. My intuition of 'things far away moving away faster' causes me to conclude that things far away are therefore accelerating, because the more they move away the faster they move away, but my intuition is probably wrong as it doesn't line up with the raisin bread analogy.

anon25783 3y ago

At any point in space, a celestial object at distance d will tend to appear to move away from you faster than an object at a distance less than d. The only thing special about the Earth here is that it happens to be where we live.

317070 3y ago

> our awareness of the galactic bodies itself is somehow influencing them, as in the double-slit experiment In the double slit experiment, the awareness is not influencing the outcome. The act of measuring is. Pretty sure the act of measuring the galactic bodies has no impact on them in any meaningful way.

I_Am_Nous 3y ago
No, but there is a cool blending of the two concepts when light is bent by large gravity wells so that it actually shows the same star multiple times. When we observe which copied star "produced" a certain photon, it technically collapses the quantum possibilities backwards in time as that photon was emitted potentially billions of years ago.
- rightbyte 3y ago
  > it technically collapses the quantum possibilities backwards in time as that photon was emitted potentially billions of years ago There is no way to verify that. Big parts of quantum physics is more or less pseudoscience.
  - I_Am_Nous 3y ago
    Perhaps it could be verified using time delayed lensing experiments[1]? 1. https://www.nature.com/articles/s41550-021-01450-9 https://www.nature.com/articles/s41550-021-01450-9
    - rightbyte 3y ago
      Seems like measuring "bending" of light, rather? But honestly I am not really qualified to say anything about astronomy.
      - I_Am_Nous 3y ago
        In this case it's light bending around a gravity well which produces multiple "copies" of the star, but the light from each copy arrives at different points in time. So they could capture the light and attempt to capture the "same" light again later to try to verify or change the result they received. I did some more reading about it after posting, and the original experiment was intended to test if light "chooses" to be a wave OR a particle in a way they could affect, and that it could only be one or the other at a time. The truth seems to be more that it acts as both at the same time and whatever sensor equipment you use to pick it up is what it acts like.

M2Ys4U 3y ago

> Why would distance from earth influence the speed of expansion of a distant galaxy? It wouldn't - but it may influence how we measure distance. If we're using the wrong distance measurements then we're calculating the speed of expansion incorrectly.

cwmma 3y ago

no it's because space itself is expanding which causes things more distant from each other to be moving away from each other faster, the wikipedia article about hubbles law has a graphic illustrating the priciple with bread https://en.wikipedia.org/wiki/Hubble%27s_law https://en.wikipedia.org/wiki/Hubble%27s_law

edgyquant 3y ago
Wikipedia is not a proper source and I’ve no idea why people stopped considering this and now use it as such. The graphic may be fine, but provide a real source when pushing back against another commenter.
- johndunne 3y ago
  To be fair to Wikipedia, it’s come on a long way since its early days when anyone could make whatever edits they wanted. The most popular entries on the site are very well vetted, though not perfect. Just my 2 cents.
- zlg_codes 3y ago
  Pages contain other sources, however, which makes WP a good place to begin research on a topic. This place isn't debate club and nobody's getting a prize for winning an Internet argument.
  - edgyquant 3y ago
    No they don’t. Wikipedia pages, according to their own rules, contain secondary sources.

deleted 3y ago

[deleted]

gizmo686 3y ago

This observation is the reason we think the universe is expanding. As an analogy, consider the 2 dimensional surface on the surface of a balloon. As you inflate the balloon, the distance between any 2 points increases, and it increases more the farther away the points are from each other.

Udo 3y ago

> Does that suggest that our awareness of the galactic bodies itself is somehow influencing them, as in the double-slit experiment? "Awareness" is not a thing, not even in the double slit experiment. The term 'measurement' refers to a specific kind of interaction that bridges quantum systems with classical systems, although I believe a good case could be made that these waveforms never actually fully collapse. Likewise, if there is anything special about Earth's position in the greater cosmos, it would be a trick of perspective or perception - unless there are any completely disruptive new discoveries about the nature of reality. However, my money would be on the fact that the universe is simply not as uniform as we thought.

chongli 3y ago

Galaxies themselves aren't expanding, they're gravitationally bound. Galaxies are moving apart from one another, however. The issue is that not all galaxies are moving away from us. The ones that are closer to us have a lot of peculiar velocity [1]. This means they can be moving toward us or moving tangentially to us or any other direction. If we want to characterize the expansion of the universe as a whole, we need to account for this in our models. It turns out to be a lot more complicated than we previously thought. The crisis in cosmology (aka the Hubble tension [2]) is that our two means of characterizing the expansion of the universe, models of the cosmic microwave background (CMB) and measurements on the cosmic distance ladder using standard candles (Cepheid variables [3] for up-close measurements, Type Ia supernovae [4] for more distant measurements) disagree with one another, and that disagreement is getting worse, not converging. [1] https://en.wikipedia.org/wiki/Peculiar_velocity#Cosmology https://en.wikipedia.org/wiki/Peculiar_velocity#Cosmology [2] https://en.wikipedia.org/wiki/Hubble%27s_law#Hubble_tension https://en.wikipedia.org/wiki/Hubble%27s_law#Hubble_tension [3] https://en.wikipedia.org/wiki/Cepheid_variable https://en.wikipedia.org/wiki/Cepheid_variable [4] https://en.wikipedia.org/wiki/Type_Ia_supernova https://en.wikipedia.org/wiki/Type_Ia_supernova

sesm 3y ago

One alternative explanation is that the expansion of the universe is slowing down.