6 ms·

Can someone explain to me what would be behind the galaxies if we could see it, to the point of 0 seconds after the big bang? Black, white, is it even possible?

• ajross 4y ago
  The very early universe can't be observed with visible light. It was filled with ionized hydrogen and thus opaque over long distances. The oldest light is from the era of "recombination", when things had cooled enough (c. 370k years after the big bang by consensus models) to permit light to travel. This is just the thermal glow of the universe, redshifted (way, way) down into the radio spectrum. And we can see it just fine; it's the cosmic background radiation and has been very well studied. It's the region between recombination and the currently-visible-to-telescopes galaxies that Webb is particularly well-suited to study.
• rjrodger 4y ago
  Visible light was scattering off densely packed electrons up to about 300k years after the Big Bang - so I guess - white.
  • ben_w 4y ago
    White, redshifted so hard it's the blackest black we ever experience. (I want to add a H2G2 joke here, but I can't figure the right way to reference making God disappear in a puff of logic related to the Babelfish…)
• shadedtriangle 4y ago
  We can see it and it’s called the Cosmic Microwave Background https://en.m.wikipedia.org/wiki/Cosmic_microwave_background https://en.m.wikipedia.org/wiki/Cosmic_microwave_background. It’s not t=0.0000001 though as the time before the cosmic microwave background the universe was opaque to photons, you wouldn’t be able to see anything.
• klodolph 4y ago
  Correct me if I'm wrong. Cosmic microwave background is behind the galaxies, and we can see it. The universe is mostly transparent these days, so light can travel across the universe from a distant galaxy to our eyes or telescopes. Long ago, the universe was full of ions-free electrons and protons-and these are very effective at scattering light, so the universe was effectively opaque at that point. The universe became more transparent as the universe shifted towards hydrogen atoms instead of free electrons and protons. Whatever the universe happened to look like during that transition period, from opaque to transparent, is still what we see. It's the cosmic microwave background. Anything from before that time got absorbed.
  • jfengel 4y ago
    Yep. That is all correct. It's conceivable that we could observe gravitational waves during that period before the CMB, because they're not blocked by the un-recombined electrons and protons. If we ever get there, it could help explain the small variations in CMB from place to place. But that's a long way off.
• feoren 4y ago
  Not an expert here but it sounds like you might be describing the Cosmic Microwave Background. This is basically the remnant of the early opaque plasma cloud that filled the entire universe. As we look far away/back in time, the photons reaching us have redshifted due to the expansion of the universe. That's why these originally extremely high-energy photons are now just low-energy microwaves. The "background", 0 seconds after the Big Bang, is in all directions, and presents as the Cosmic Microwave Background. Or so I understand. https://en.wikipedia.org/wiki/Cosmic_microwave_background https://en.wikipedia.org/wiki/Cosmic_microwave_background
  • Pxtl 4y ago
    There's always a relevant xkcd for every science question, and in this case it's one of the first ones: https://xkcd.com/54/ https://xkcd.com/54/
    • limbicsystem 4y ago
      But oddly the most recent one as well https://xkcd.com/2723 https://xkcd.com/2723
      • yreg 4y ago
        It's incredible how Randall seems to be able to come up with an endless number of fun ideas even after all these years.
• soiler 4y ago
  We can actually already see that time period, in its present form. It's called the Cosmic Microwave Background. It is the (now extremely cold) energy which permeated the entire universe in that very early time period. The entire universe was opaque and extremely hot... then as it expanded, it began to cool enough for particles and then atoms to form. Only then were stars possible, and later galaxies. How/why can we see the CMB? Well, it was everywhere. Literally every point in the universe was a nearly uniform sea of blazing energy. So if you look far enough in any direction, you will see the cold echoes of that time period. edit: Beat to the punch! I hope among our many answers you've found something enlightening edit 2: Important to note that the CMB is not synonymous with the beginning of spacetime. It is more like a wall, beyond which we can't see anything, and it came down very early in time.
  • drexlspivey 4y ago
    Kinda relevant xkcd that was published today https://xkcd.com/2723/ https://xkcd.com/2723/
  • bpye 4y ago
    > and it came down very early in time. Is this just because we’ve used it to define the start?
    • soiler 4y ago
      No, models predict that an extremely short amount of time elapsed before this. Like orders of magnitude less than 1 second. However, we know our models are not perfectly accurate, so it is possible there is something else very weird going on.
• Tuna-Fish 4y ago
  We can't see down to 0 seconds, because very soon after the big bang, the universe was filled with dense, extremely hot, opaque plasma. The closest we can get is the "recombination epoch" [0], which is roughly 370 000 years after the big bang, when, because of universal expansion, the plasma got cold enough for neutral hydrogen to start forming, at which point the universe became transparent. As protons gain electrons in high temperatures, they don't form in the ground state. Instead, the newly minted hydrogen atoms are in a highly exited state. As they fall back to their ground states, they emit infrared photons at ~3000K color temperature. These photons, redshifted by the expansion of the universe to ~2.7K, are the Cosmic Microwave Background, the uniform ultimate backdrop we have when looking in any direction. [0]: Which has it's slightly incorrect name (should not have re-) because it was named before the big bang became a widely accepted or known theory.
  • seanw444 4y ago
    So if we can see CMB in all directions, why do we really even say "the observable universe" as though there could be more matter and more galaxies beyond what we can see? If the maximum of what we can see is implied to be before all galaxies, then shouldn't it be implied that all galaxies that exist can be seen?
    • deleted 4y ago
      [deleted]
    • sebzim4500 4y ago
      No, because galaxies almost certainly exist which are further than the CMB. It's just that the light travelling from them has not been able to reach us in the time since it was emitted.
      • dwaltrip 4y ago
        And never will reach us, as the space in between us and that distant light is expanding to quickly.
    • jfengel 4y ago
• mandevil 4y ago
  As everyone has already pointed out, the Cosmic Microwave Background Radiation is as close as you can get to the Big Bang. But to the larger point, these galaxies were suspected before, based on Hubble work. You see, the COBE satellite from 1989 to 1993 mapped the microwave background radiation very precisely (two of the Principal Investigators on COBE won the 2006 Nobel Prize in Physics for this work). And they found that while there are minute fluctuations in the radiation, those fluctuations are measured at the parts-per-million level of difference. But the Hubble has found that the farthest back galaxies it could see were some of the largest and most massive things ever witnessed. So we had this gap between 'everything everywhere is the same to parts per million' and 'there are some supermassive galaxies' and so the Webb telescope was specifically designed to find the things that were redshifted so far they were out of the visible spectrum (so Hubble couldn't see them) but not so far that COBE could see them in microwave: in the infrared spectrum that lies between those two, that's where Webb is supposed to focus and help us understand how these galaxies form. Because this question of what happened between the CMBR and the visible light range is the biggest question left over from Hubble, so it is what drove the design of the Webb. This is how astronomy has worked for centuries: you build a new telescope to answer some questions, but that leaves you with more questions, so you need to build new telescopes to answer those questions, GOTO 1. That's what's been happening ever since Galileo looked through that telescope at Jupiter all the way back in 1610.
• b800h 4y ago
  There is a wonderful sequence in the (2nd?) Book of Enoch (~150AD?), where the viewer is transported up through the heavens, past the planets, and finally beyond the stars, and eventually sees the incomprehensible face of God lying behind it all, visible all across the far end of space. So perhaps that? :-)
  • moloch-hai 4y ago
    Great flaming letters spelling out "We apologize for the inconvenience".
    • b800h 4y ago
      Haha, Douglas Adams was nothing if not well-read.