I’ve always wondered how astronomers can actually observe galaxies that are millions or even billions of light-years away. What exactly are we seeing when we look at them?

And when scientists say there are hundreds of billions, or possibly trillions, of galaxies in the observable universe, how do they know that if we obviously haven’t seen and counted every single one?

  • lime!@feddit.nu
    40·
    2 days ago

    have you seen the Hubble Deep Field image?

    it’s a picture of a section of the sky “about the size of a tennis ball at a hundred meters” taken by pointing the telescope at a point that appeared completely dark over a period of 10 days. there are over 3000 galaxies in that image.

    • queerlilhayseed@piefed.blahaj.zoneEnglish
      13·
      2 days ago

      I remember the first time I saw that image. The dazzling scope of it. The feeling that Carl Sagan described about the Pale Blue Dot photograph is the closest thing I’ve seen to describing the incredible sense of smallness the Deep Field image gives me. I still get a shadow of it, especially with the JWST images, but that was the first time I really felt how huge the universe is. It’s… words fail me. It’s so big, and there’s so much stuff in it. It boggles the mind.

      I can’t fucking wait for the Roman data to start rolling in. We’re going to find so many cool things we’ve never seen before.

      • Mantzy81@aussie.zoneEnglish
        4·
        2 days ago

        As a geologist we talk in millions and billions of years regularly and it’s part of our thing to realise how small and insignificant our lives and humanity is in general.

        But as an amateur astronomer, the vastness and time of space is just another level.

        • Alex@lemmy.ml
          3·
          2 days ago

          The age of the Earth is a significant fraction of the age of the universe so we are not totally divorced from the timescale.

          • queerlilhayseed@piefed.blahaj.zoneEnglish
            4·
            2 days ago

            Age of Universe: ~13.8B years
            Age of Earth: ~4.5B years
            Life on Earth: ~3.7B years

            Assuming those estimates are correct, there has been life on earth for about a quarter of the time since the Big Bang. The solution to the Fermi Paradox could well be that we’re simply among the first species able to look out into the stars. Maybe the Universe is just getting started.

            • Alex@lemmy.ml
              1·
              2 days ago

              Or we could be about to add a data point to the great filter theory, take your pick 😉

              • queerlilhayseed@piefed.blahaj.zoneEnglish
                2·
                1 day ago

                If by we you mean humans, IDK it’s looking pretty dicey at the moment. We as in Earth? I think will be just fine a million or so years after we’re gone, and in that time other intelligences may rise. Maybe octopi start forming complex social groups, or chimpanzees fill the niche we leave, or the fungal network finally reaches critical mass and becomes a planet-spanning superconsciousness and catapults itself into the space age by interpreting ancient human artifacts. I think Earth is gonna be a galactic contender. Whether humans are around when that happens is another question.