5 ms·

Grimdark fiction[0] aside, I doubt anything is traveling across intergalactic voids of any size. [0]: https://warhammer40k.fandom.com/wiki/Tyranids https://war

by wffurr 6y ago

Grimdark fiction[0] aside, I doubt anything is traveling across intergalactic voids of any size. [0]: https://warhammer40k.fandom.com/wiki/Tyranids https://warhammer40k.fandom.com/wiki/Tyranids

koheripbal 6y ago
I saw an MIT PhD thesis defense video of a paper that described the calculations of how far/fast probes could spread between galaxies. I really wish I could find it again... but my searches have failed. The conclusion was that self-replicating probes could indeed populate (I forget how many - on the order of hundreds of thousands/millions) nearby galaxies within the last couple billion years. It was pretty compelling. The discussion at the end did see some debate of "well then where are they?". A valid question. Why haven't self-replicating probes infected the entire visible universe by now?
- mellosouls 6y ago
  This is essentially the question raised by the Fermi Paradox. https://www.wikipedia.org/wiki/Fermi_paradox https://www.wikipedia.org/wiki/Fermi_paradox
- trhway 6y ago
  wouldn't it be like we did with plastic bottles to the oceans? only imagine if the bottles could self-replicate. Pollution at intergalactic scale. Probably getting to specific levels of technology requires specific level of consciousness - a corresponding level of awareness about actions and consequences. A technological level increase without corresponding consciousness level increase is probably one of the great filters. Like for example human civilization failure to recognize the human civilization induced global warming. wrt. original post : >For ΛCDM to fit the pattern of fluctuations observed in the CMB by the Planck satellite and other experiments, the Hubble constant must have a particular value of 67.4 ± 0.5 km/s/Mpc. Local measurements are nearly all above this ‘Planck value’, but are consistent with each other. In our paper, we use a local value of 73.8 ± 1.1 km/s/Mpc using a combination of supernovae and gravitationally lensed quasars, two particularly precise yet independent techniques. I think it is not an accident that c divided by the age of the universe (meaning that those stars have been flying away from us with constant speed c) produces 71km/s/Mpc. That also means that there is no acceleration nor deceleration - stars fly away from us with constant speed [Hubble constant x distance] with the distance growing and the Hubble constant decreasing resulting in the same speed for any given star.
- sliken 6y ago
  Sounds pretty close to http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spreading.pdf http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spr... Who is to say there isn't such a probe in the solar system currently? Said probe could be watching earth for promising or dangerous signs and deciding what to do.
  - koheripbal 6y ago
    Because of your comment, I was able to find it... https://www.youtube.com/watch?v=zQTfuI-9jIo https://www.youtube.com/watch?v=zQTfuI-9jIo Seems it was Oxford, not MIT.
    - sliken 6y ago
      Heh, same material, same speaker, just a bit less detail in the presentation, and a bit more discussion.

by wffurr 6y ago

Grimdark fiction[0] aside, I doubt anything is traveling across intergalactic voids of any size. [0]: https://warhammer40k.fandom.com/wiki/Tyranids https://warhammer40k.fandom.com/wiki/Tyranids

koheripbal 6y ago

I saw an MIT PhD thesis defense video of a paper that described the calculations of how far/fast probes could spread between galaxies. I really wish I could find it again... but my searches have failed. The conclusion was that self-replicating probes could indeed populate (I forget how many - on the order of hundreds of thousands/millions) nearby galaxies within the last couple billion years. It was pretty compelling. The discussion at the end did see some debate of "well then where are they?". A valid question. Why haven't self-replicating probes infected the entire visible universe by now?

mellosouls 6y ago
This is essentially the question raised by the Fermi Paradox. https://www.wikipedia.org/wiki/Fermi_paradox https://www.wikipedia.org/wiki/Fermi_paradox
trhway 6y ago
wouldn't it be like we did with plastic bottles to the oceans? only imagine if the bottles could self-replicate. Pollution at intergalactic scale. Probably getting to specific levels of technology requires specific level of consciousness - a corresponding level of awareness about actions and consequences. A technological level increase without corresponding consciousness level increase is probably one of the great filters. Like for example human civilization failure to recognize the human civilization induced global warming. wrt. original post : >For ΛCDM to fit the pattern of fluctuations observed in the CMB by the Planck satellite and other experiments, the Hubble constant must have a particular value of 67.4 ± 0.5 km/s/Mpc. Local measurements are nearly all above this ‘Planck value’, but are consistent with each other. In our paper, we use a local value of 73.8 ± 1.1 km/s/Mpc using a combination of supernovae and gravitationally lensed quasars, two particularly precise yet independent techniques. I think it is not an accident that c divided by the age of the universe (meaning that those stars have been flying away from us with constant speed c) produces 71km/s/Mpc. That also means that there is no acceleration nor deceleration - stars fly away from us with constant speed [Hubble constant x distance] with the distance growing and the Hubble constant decreasing resulting in the same speed for any given star.
sliken 6y ago
Sounds pretty close to http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spreading.pdf http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spr... Who is to say there isn't such a probe in the solar system currently? Said probe could be watching earth for promising or dangerous signs and deciding what to do.
- koheripbal 6y ago
  Because of your comment, I was able to find it... https://www.youtube.com/watch?v=zQTfuI-9jIo https://www.youtube.com/watch?v=zQTfuI-9jIo Seems it was Oxford, not MIT.
  - sliken 6y ago
    Heh, same material, same speaker, just a bit less detail in the presentation, and a bit more discussion.