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How We'll Someday Be Able To See Past the Cosmic Microwave Background
StartsWithABang writes: When it comes to the farthest thing we can see in the Universe, that's the Cosmic Microwave Background, or the leftover glow from the Big Bang, emitted when the Universe was a mere 380,000 years old. But what, exactly, does this mean? Does it mean that we're seeing the "edge" of the Universe? Does it mean that there's nothing to see, farther back beyond it? Does it mean that, as time goes on, we're going to be able to see farther back in time and space? The answers are no, no, and yes, respectively. If we want to see farther than ever before, we've got two options: either wait for more time to pass, or get moving and build that cosmic neutrino background detector.
As soon as somebody replaces the 17 year old microwave in the cafeteria of the observatory, since scientists can't be bothered to wait until the cycle is done.
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Can we lose the daily barrage of pop-sci please.
Gee... I wonder who the linked astronomy-related Slashdotted story will have been written by.
Click...
Yup. Thought so. Is there nobody else writing astronomy blogs these days? Or is Slashdot just in love with Ethan?
It's not like it's going anywhere, right guys?
The neutrino is the trendy particle, now?
Bah! Wake me when the tetryon is discovered.
Wake me an hour before the chroniton is discovered.
It's the limit of what's observable.
It's like how a light beam can have an edge, but it doesn't mean there isn't anything in the shadow.
>> The answers are no, no, and yes, respectively.
If I'm reading this right, you just said:
But what, exactly, does this mean? no
Does it mean that we're seeing the "edge" of the Universe? no
Does it mean that there's nothing to see, farther back beyond it? yes
Does it mean that, as time goes on, we're going to be able to see farther back in time and space? (no response)
So how do they know that the "background" microwaves are from the edge of the universe? I thought that the primordial microwaves are scattered throughout the universe, so what we see when we look in some direction is the sum of all the background microwaves coming from that direction.
If we're actually seeing the edge, doesn't that shoot down the idea that the universe doesn't actually have an edge, and everywhere appears to be at the "center" of the universe? How was this idea disproved? I seem to have missed the discovery of an actual edge, somehow.
The cmb is simply the first light that was able to freely travel through space. There is no actual 'edge' but there is always the apparent virtual edge beyond which you cannot see. It's easiest to think of it as space being infinite in size but finite in age. Light needs to travel to your eye to see so the farthest you can see is simply the age of the universe x the speed of light. As the universe cooled right after the Big Bang, initially light could not directly pass through all the hot plasma, only after it cooled and became transparent to visible light did light spread out in significant amounts. The heavily red shifted version of this light is the cmb we see today. Your own two eyes see a slightly different virtual 'edge' as every point in the universe looks as if it is the center.
It took about 380k years for the universe to become transparent to light neutrinos pass through ionized material easily and the surface of last scattering is nearly as old as the Big Bang. It's a very old concept but has been researched lately as each kind of neutrino would have a slightly different background. The article is just random click bait there is nothing new or interesting about it really.
"It's like how a light beam can have an edge, but it doesn't mean there isn't anything in the shadow."
In this case the shadow is in front of the pulse of light that was the big bang.
We will never be able to see further than that since it is moving away at the speed of light.
Unless we can invent a (much) faster than light drive, and go chase it down.
Amongst all the /. arguments, I would like to say that that is a well written article. It gets a very complex point across in a way that is easily understood. I didn't realize previously that our view of the CMB would change over time. Makes sense, we see the CMB who's light happens to get here now.
When the first stars formed, the energy released re-ionized the entire universe, so that first-last burst of radiation was absorbed by electrons. The second last-burst is what we see now, when the universe cooled to allow the electrons to re-combine. Some of it has been absorbed over time. But, the universe is now transparent. Much of it hasn't met anything that could stop it from the time it was created until it hits one of our antenna. BTW, being absorbed by a microwave radio antenna does destroy the radiation received. It's not the amount that we are measuring, but the wavelength that is critical. When creating the CMB maps, they do have to take into account relatively nearby objects that could stop it, including the plane of our galaxy.
The microwave background radiation is what remains from the red-shifting of a burst of light when electrons became bound to protons and was stretched by the subsequent expansion of space. Wasn't there an earlier burst, of gamma rays, when quarks condensed from the quark-gluon plasma to form baryons? Has that been absorbed/scattered to obscurity by interaction with matter since then?
The entire universe was quite opaque then, much like the core of the sun. Those photons didn't ravel far before finding an electron, which of course would emit a new photon (also gamma frequencies at first) soon. The dominant forces in the universe between the first few seconds and 300K years were gravity and light pressure. The photons of the CMBR were still fairly high energy at the point the universe became transparent - there's just been a significant redshift since then.
Why hasn't the microwave background has not similarly been obscured by interaction with matter (exciting rotational energy levels of molecules?)
For the same reason we can see distant stars: matter is quite sparse these days, and hydrogen and helium only absorb light of a specific set of frequencies.
Socialism: a lie told by totalitarians and believed by fools.
IANAP, but from what I read in most models of inflation there should be primordial gravitational waves, which could be indirectly detected based on the polarization of the CMB (b-modes). These waves (if they exist) would go all the way back to the inflationary period itself.
The BICEP2 experiment was designed to look for these, and last year announced detecting b-modes in the CMB. Of course, as we now know thanks to Planck their discovery is probably due to dust polarization. Are there any current or planned experiments that could differentiate between dust polarization and potential gravitationally-caused polarization?
Imagine a hot Universe at an early time (which may be very large, even infinite). Photons are suddenly released and go in all directions.
The Universe expands (meaning the distance between everything increases). The photons are still traveling through the Universe.
At any point in time you can observe photons arriving at your position, and they are as old as their origin is away in light-distance (well, space expanded in the meantime, that makes it a bit harder to imagine).
So, you can observe the background at any time, from all directions. It gives you access to the space where the photons where released, called a "last scattering surface". As time goes by, the photons have to be older and their distance larger, to arrive now.
NB: The message above might reflect my opinion right now, but not necessarily tomorrow or next year.
Oblig. Weird Al.
Wait is that not The Edge you were talking about?
Nothing posted to
There you go again with your xenophobia. The weird thing is that you would let the world know you are scared and ignorant of a great portion of it, and happily so at that. Bizarre.
Does it mean that, as time goes on, we're going to be able to see farther back in time and space?
Obviously the answer is yes because, as time goes on, the period at which the CMB was emitted moves further into the past so obviously we are seeing "further back in time" but only at the rate of one year further per year past (on average). Since the universe is also expanding we are also looking further. This is about as insightful as pointing out that as time goes by I can remember events further back in time.
http://www.merriam-webster.com/dictionary/further
Definition 1) Farther
Heh; I think you've got it. ;-)
This is one of the favorite "language peevery" examples that get discussed often in (English) language forums (or fora if you prefer ;-). The confusion about any purported difference goes back to before there were any actual English dictionaries, and probably 99% of the world's native speakers of English treat them as synonyms. The few that don't can't hardly agree about what their "correct" usages should be. But that doesn't stop such people from harrassing the rest of us about our "misusage". Mostly, it's just a thing they can feel superior about, while the rest of us casually ignore them.
It is a bit curious to see such peevery pop up in a discussion in which General Relativity pretty much rules. Trying to make a strict distinction between distance and time in such discussions is mostly just funny, as well as a signal that the writer lacks understanding of something important to the discussion. But language peevery is rarely based on reality; it's more about some small crowd's attempts to impose strict rules on a language with many dialects and hundreds of millions of speakers.
Now let's all join in singing a round of "Farther along" ... (in which the phrase clearly refers to time. ;-)
Those who do study history are doomed to stand helplessly by while everyone else repeats it.
Allah and God and Jesus and Yaweh are all the same self-hating guy.
Ermm they are not. In all 3 monotheistic religions, 'God' is qualitatively different.
The oldest Hebrew has a monotheistic God with NO recognized prophet.
The Christians have a tripart God as 3 identities, the total of which is a monotheistic god that also predates itself.
The newest - Allah who is further removed from 'man', is based on the Hebrew God (the first 4 books of the Hebrew bible) and comes with a prophet.
(I don't believe any of this btw)
Don't be apathetic. Procrastinate!
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The 'edge' you're talking about is the Cosmic Horizon. The further away you look, the more ancient the light, and if you look further than 13 and a bit billion light years, you're "looking" at a place where the light hasn't had a chance to reach us yet. It's still in transit. So it isn't an 'edge' to anyone other than us. As I understand it, the Universe is consistent with being (at least) a hypersphere; finite in extent but with no boundary - analogous to how the Earth's surface is finite but without a boundary.
I do not want your cheap brainburning drugs. They are useless for work. And I am a working man today.
Does this not involve paradoxes, e.g. why isn't the whole sky as bright as the surface of a star?
I do not want your cheap brainburning drugs. They are useless for work. And I am a working man today.