4 ms·

What I'm not quite sure of exactly is: (1) why infrared? Why doesn't the redshift extend further, into microwave or radio? Is that an instrument limitation (we

by mlsu 4y ago

What I'm not quite sure of exactly is: (1) why infrared? Why doesn't the redshift extend further, into microwave or radio? Is that an instrument limitation (we can't build a radio telescope big enough to look at 14 billion years ago so we settle on an infrared telescope that can look 13 bya? And, (2) is there a limit to this? I understand that the Hubble constant is where the "amount" of redshift comes from (because, the it's the rate of expansion of the universe?) -- but is this linear? If we can see things from 6bya in the visible spectrum, and things from 13bya in the infrared, does that mean that we could see the beginning of the universe itself to 14bya if only we looked just past infrared? Or does it ramp up exponentially and blast through radio because it's a singularity? And -- if we managed to look "in between" every star/galaxy so that we were truly looking at a 0% deep field with no "objects" in the way, would we be looking at the beginning of the universe itself? I know that these are all hypotheticals and we can't actually do this, just wanted to clarify that I'm on the right track about the way this works, since I'm the resident JWST geek of the group.

x86x87 4y ago
It does goes into microwave etc. We sort of can see the "beginning of the universe" See: https://en.m.wikipedia.org/wiki/Cosmic_microwave_background https://en.m.wikipedia.org/wiki/Cosmic_microwave_background The other thing to consider is that since space is expanding, we can only see the observable universe. Given enough time, the only thing that we're going to see is out own local part of the universe (that is not expanding - so there are parts of the universe that are expanding and parts that are somewhat steady state - think bubbles in liquid)
dredmorbius 4y ago
The degree of redshift is determined by the Hubble Constant, which describes how much the expansion of the Universe increases with distance. The maximum distance (time) is ~13.8 billion years. The very earliest period of the Universe cannot be directly observed as matter was too dense for light to be transmitted through it (about 375,000 years after the Big Bang). The first stars are thought to date from 400 million years. Knowing when you want to look to, and how far that is (time is distance at light speed), the red-shift amount is calculable. Peak stellar emission (~3000K for a Class G star such as our Sun) would be redshifted by that amount, and the detection frequency(ies) / wavelength(s) could be chosen correspondingly. Detection in the infrared or below also requires chilling reflector and sensor surfaces, as was the case for the JWST, which raises challenges. My understanding is that, yes, looking back and observing nothing is looking toward the primordeal Big Bang radiation itself. My understanding is that that itself would be emitting at the spectrum of the Cosmic Background Radiation, in the microwave range, at a blackbody temperature of about 3K. That would have a range of wavelengths, though I believe the peak would be about 0.2cm. https://map.gsfc.nasa.gov/universe/bb_tests_cmb.html https://map.gsfc.nasa.gov/universe/bb_tests_cmb.html That's much longer (lower frequency) than the JWST can detect, and it would simply see blackness (no detectable radiation).
News-Dog 4y ago
The Doppler effect or Doppler shift : https://en.m.wikipedia.org/wiki/Doppler_effect https://en.m.wikipedia.org/wiki/Doppler_effect - {play and listen to the audio} is akin to Redshift : https://en.m.wikipedia.org/wiki/Red_shift https://en.m.wikipedia.org/wiki/Red_shift

by mlsu 4y ago

x86x87 4y ago

It does goes into microwave etc. We sort of can see the "beginning of the universe" See: https://en.m.wikipedia.org/wiki/Cosmic_microwave_background https://en.m.wikipedia.org/wiki/Cosmic_microwave_background The other thing to consider is that since space is expanding, we can only see the observable universe. Given enough time, the only thing that we're going to see is out own local part of the universe (that is not expanding - so there are parts of the universe that are expanding and parts that are somewhat steady state - think bubbles in liquid)

dredmorbius 4y ago

The degree of redshift is determined by the Hubble Constant, which describes how much the expansion of the Universe increases with distance. The maximum distance (time) is ~13.8 billion years. The very earliest period of the Universe cannot be directly observed as matter was too dense for light to be transmitted through it (about 375,000 years after the Big Bang). The first stars are thought to date from 400 million years. Knowing when you want to look to, and how far that is (time is distance at light speed), the red-shift amount is calculable. Peak stellar emission (~3000K for a Class G star such as our Sun) would be redshifted by that amount, and the detection frequency(ies) / wavelength(s) could be chosen correspondingly. Detection in the infrared or below also requires chilling reflector and sensor surfaces, as was the case for the JWST, which raises challenges. My understanding is that, yes, looking back and observing nothing is looking toward the primordeal Big Bang radiation itself. My understanding is that that itself would be emitting at the spectrum of the Cosmic Background Radiation, in the microwave range, at a blackbody temperature of about 3K. That would have a range of wavelengths, though I believe the peak would be about 0.2cm. https://map.gsfc.nasa.gov/universe/bb_tests_cmb.html https://map.gsfc.nasa.gov/universe/bb_tests_cmb.html That's much longer (lower frequency) than the JWST can detect, and it would simply see blackness (no detectable radiation).

News-Dog 4y ago

The Doppler effect or Doppler shift : https://en.m.wikipedia.org/wiki/Doppler_effect https://en.m.wikipedia.org/wiki/Doppler_effect - {play and listen to the audio} is akin to Redshift : https://en.m.wikipedia.org/wiki/Red_shift https://en.m.wikipedia.org/wiki/Red_shift