5 ms·

For a second I thought we'd seen a lot of the universe, the HDF being 1/5th the radius away and on googling Earandel is 2/3rds the radius... of the known univer

by ralegh 2y ago

For a second I thought we'd seen a lot of the universe, the HDF being 1/5th the radius away and on googling Earandel is 2/3rds the radius... of the known universe. "According to the theory of cosmic inflation initially introduced by Alan Guth and D. Kazanas, if it is assumed that inflation began about 10−37 seconds after the Big Bang and that the pre-inflation size of the universe was approximately equal to the speed of light times its age, that would suggest that at present the entire universe's size is at least 1.5×1034 light-years—at least 3×10^23 times the radius of the observable universe." So, if true, all those metrics of atoms, stars, planets in the known universe are multiplied by 10^23. Even if intelligent life were rare enough to only appear once per knowable universe, there could be 10^23 different intelligent species - single planet to galaxy spanning empires - that would probably never meet another intelligent species (except those with the same ancestors).

mariusor 2y ago
> if true, all those metrics ... are multiplied by 10^23 Considering the relation of radius to volume, shouldn't we add a meager 3 to make the exponent a total of 26? (Assuming of course that the universe is just a three dimensional volume. :D)
- ralegh 2y ago
  Wow totally forgot that… but wouldn’t it be (10^23)^3 = 10^69!?
  - mariusor 2y ago
    You're right, I forgot my exponentiation rules: https://mathinsight.org/exponentiation_basic_rules#power_power https://mathinsight.org/exponentiation_basic_rules#power_pow...
  - ta1243 2y ago
    nice...
deepsun 2y ago
The problem is in words "at present". There's no some global timeline to say "present". The time in far away places just didn't happen yet. UPDATE: minor consideration -- time can flow at different speeds (e.g. gravitational wells). That's probably doesn't matter to our discussion, but just another argument against "at present".
- rspoerri 2y ago
  Just because you dont see it, doesnt mean it didnt happen. The light the sun emits will only be seen by us ~8min later, but it's still being emitted right now.
  - deepsun 2y ago
    No, there's a mistake in the statement. Counter-example -- what's happening _right now_ at a distance of 20 billion light-years from us? Or another question -- what happened 1 hour _before_ the Big Bang? Both questions are already invalid by themselves. UPDATE: I should've tried to answer my questions to show what I mean: 1. At 20B ly from us there's no space nor time to talk about. Physicists talk in formulas, and I suspect if I knew how, I just wouldn't be able to come up with a formula to formulate my question. 2. "before" the Big Bang there was no time itself to say "before". In other words, we can only reason about, or imagine, reason about things, within our light cones. Outside light cone questions become invalid to ask.
    - foobarian 2y ago
      Can't we imagine a bag of clocks at the Big Bang origin that were synchronized and allowed to travel in all directions along with various sections of the ejecta, including one on Earth? One could imagine events that happen at the same clock reading as ours in all the different parts of the visible and non-visible universe.
      - riotnrrd 2y ago
        The effects of relativity cause that thought experiment to fall apart quickly. I build two clocks, and send one to alpha centauri and back in a spaceship. When the travelling clock gets back to Earth it will be showing a different time (because of time dilation during acceleration). What does "the same clock reading" mean then?
deleted 2y ago
[deleted]
layer8 2y ago
> the pre-inflation size of the universe was approximately equal to the speed of light times its age What is the basis of this assumption? Why should the universe be (initially) expanding at the speed of light?
marcosdumay 2y ago
> Even if intelligent life were rare enough to only appear once per knowable universe, there could be 10^23 different intelligent species The search space of complex organic molecules grows exponentially with size. All that difference creates is some marginal space between molecules with hundreds of monomers and hundreds of monomers + some 4 or 8 where life could fit that. Your revision of 10^70 makes it a little bit more believable. But I wouldn't expect at all that to happen.
xqcgrek2 2y ago
Interesting, I thought it was only Guth that introduced inflation.

by ralegh 2y ago

mariusor 2y ago

> if true, all those metrics ... are multiplied by 10^23 Considering the relation of radius to volume, shouldn't we add a meager 3 to make the exponent a total of 26? (Assuming of course that the universe is just a three dimensional volume. :D)

ralegh 2y ago
Wow totally forgot that… but wouldn’t it be (10^23)^3 = 10^69!?
- mariusor 2y ago
  You're right, I forgot my exponentiation rules: https://mathinsight.org/exponentiation_basic_rules#power_power https://mathinsight.org/exponentiation_basic_rules#power_pow...
- ta1243 2y ago
  nice...

deepsun 2y ago

The problem is in words "at present". There's no some global timeline to say "present". The time in far away places just didn't happen yet. UPDATE: minor consideration -- time can flow at different speeds (e.g. gravitational wells). That's probably doesn't matter to our discussion, but just another argument against "at present".

rspoerri 2y ago
Just because you dont see it, doesnt mean it didnt happen. The light the sun emits will only be seen by us ~8min later, but it's still being emitted right now.
- deepsun 2y ago
  No, there's a mistake in the statement. Counter-example -- what's happening _right now_ at a distance of 20 billion light-years from us? Or another question -- what happened 1 hour _before_ the Big Bang? Both questions are already invalid by themselves. UPDATE: I should've tried to answer my questions to show what I mean: 1. At 20B ly from us there's no space nor time to talk about. Physicists talk in formulas, and I suspect if I knew how, I just wouldn't be able to come up with a formula to formulate my question. 2. "before" the Big Bang there was no time itself to say "before". In other words, we can only reason about, or imagine, reason about things, within our light cones. Outside light cone questions become invalid to ask.
  - foobarian 2y ago
    Can't we imagine a bag of clocks at the Big Bang origin that were synchronized and allowed to travel in all directions along with various sections of the ejecta, including one on Earth? One could imagine events that happen at the same clock reading as ours in all the different parts of the visible and non-visible universe.
    - riotnrrd 2y ago
      The effects of relativity cause that thought experiment to fall apart quickly. I build two clocks, and send one to alpha centauri and back in a spaceship. When the travelling clock gets back to Earth it will be showing a different time (because of time dilation during acceleration). What does "the same clock reading" mean then?

deleted 2y ago

[deleted]

layer8 2y ago

> the pre-inflation size of the universe was approximately equal to the speed of light times its age What is the basis of this assumption? Why should the universe be (initially) expanding at the speed of light?

marcosdumay 2y ago

> Even if intelligent life were rare enough to only appear once per knowable universe, there could be 10^23 different intelligent species The search space of complex organic molecules grows exponentially with size. All that difference creates is some marginal space between molecules with hundreds of monomers and hundreds of monomers + some 4 or 8 where life could fit that. Your revision of 10^70 makes it a little bit more believable. But I wouldn't expect at all that to happen.

xqcgrek2 2y ago

Interesting, I thought it was only Guth that introduced inflation.