See?
Space (and the night sky) is dark because the bajillions of stars that would light the sky are moving away from us such that the Doppler effect makes their light appear infrared, which we can't see.
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Fri Oct 5, 2012 9:27 PM EDT
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And that boys and girls is one of the reasons the right wing in this country thinks things like PBS need to go. All that inconvienent science stuff called facts.
So, we don't see the light, but can we benefit from the infrared therapy on those dark nights?
"And God said, “Let there be light,” and there was light. 4 God saw that the light was good, and he separated the light from the darkness. 5 God called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day."
Heathen science! Obviously the night sky is dark, and it is dark because God didn't put a sun there!
Seriously, though, Eileen - you don't get an infrared "bath" during the nighttime (you would, by the way, get as much during the daytime) because the Earth's atmosphere is strongly absorptive to infrared light, eliminating almost (* sorry, not scientific) all of it before it reaches your body splayed out in the dark. Which is a good thing, because infrared radiation can be very damaging to our cells.
Hubble can see those infrared stars quite well, because it is in orbit well above the atmosphere. An earth-bound telescope has a much harder time seeing those stars (it is possible to see them, but the light is orders of magnitude dimmer).
And before anyone remarks on the astonishing coincidence that the atmosphere filters out the wavelengths of light we can not see and which are most harmful to us, it is the other way around; we are not resistant to damage from those wavelengths of light because we evolved with no threat from heavy IR or UV light; we are not sensitive to seeing those wavelengths of light because they are relatively scarce where our eyes evolved.
The video on speed of light was just as interesting. I wish they this method of teaching when I was a kid.
They did. It was when your physics teacher dimmed the lights and fired up the soothing "clack clack clack" machine. If it were possible to stay awake in such an environment you would have seen less-slick presentations of many of the same concepts :)
Thank You, waited 45 years to hear this answer, lights out,
Which brings up the question, if we could see infra-red light, would the night sky be lit up just like daytime? I suspect not, given that infra-red images from Hubble also have a darker background.
Comsic Background Radiation is primarily microwave. Not even close to our visible light spectrum.
While the video is correct in the sense that space looks black because we can't see "light" that is there, it also looks black to any limited spectrum detector. Perhaps it wouldn't look black if we could see the entire EM spectrum.
That's called space. There is nothing to see, we can only imagine what may be beyond space, more space. There is a natural reason as to why it gets dark every night, all living creatures need to sleep and it is condusive with darkness. I think we need to clean up our mess first, here on our own planet before we start deciding to mess up another one. One thing we don't need is more chaos.
Uh, no, not quite....
For all that we currently believe is true about the course of Earth's history, 'darkness' predates every living thing on this planet. Every living creature on this planet developed a need for sleep as one part of species' evolution. If there never were any darkness here -- say, in some kind of binary star system -- it is likely that creatures here would have adapted their need for sleep in some different way. (...also presumes the possibility of life-supporting planets orbiting a binary star system somewhere, but that is beside my point.)
Is it really neccessary for us to fill every empty space. We do need to breathe a little.Space needs it's own space too, let's just leave it alone and stop trying to mess with it and name it or look to see what's insde of it, Pandora really doesn't need to open up another jar right now. Let's let them find us this time.
Is this intended to be a joke? It is at the level of ignorance more typical of Creation Science.
Redshifts are the correct explanation for the faintness of the cosmic background radiation, which is red-shifted by a factor of about 1,000 from an effective temperature of about 3000 K to less than 3 K, but not for stars and galaxies. We see them only at redshifts up to about 10, since they formed much later.
The reason that stars do not light up the whole sky to the brilliance of the sun is that the distant galaxies are so far apart within the Hubble volume, the region of the Cosmos that we can see. There are just not that many stars. This is also an effect of the Hubble expansion, but not the same effect.
Back when the Cosmos was supposed to be infinite in extent and static, and the speed of light was not well understood, German astronomer Heinrich Wilhelm Olbers, among others, raised this question, which became known as the Olbers Paradox.
Thanks for that. I had vaguely remembered the red shift was not quite right, but I completely forgot the correct technical explanation
I think this is at least as incorrect (by which I mean imprecise rather than wrong) as the video. As one looks "further away" (that is, in a direction where there are not nearer stars obstructing our view) the density of matter becomes greater - and the proto-galaxies closer together. "Galaxies" get very rare very quickly, and you get to the distance before galaxies formed rather quickly, and then they are indeed ver "far apart" since there are none :) This is because (as the video explains rather well) as we look farther away we are also looking farther back in time, towards a time of the universe when the universe itself was much smaller than it is today.
Olber's Paradox is generally resolved exactly as the video states, although the headline is a bit misleading ("bajillions of stars" might be accurate depending on your interpretation of "bajillions", but what would light up the sky if not for doppler shift would be the background radiation of the Big Bang, or rather pre-star-formation, not bajillions of ever-more-distant-and-less-bright stars).
Doppler shift moves a number of stars and galaxies (etc) out of the visible range, although you are correct that even without doppler shifting of stars we wouldn't be seeing stars in every direction.
You are technically correct. The best kind of correct.--Futurama
I am also correct, using a different coordinate system. I am describing the present appearance of distant galaxies, not their locations when they emitted the light. They were indeed much closer together then than they appear now. That's one of the difficulties about space-time, specifying which view you are taking.
Another correct perspective is to note that there are nowhere near enough galaxies in the Hubble volume to fill up the sky. But when you look at the Hubble Extreme Deep Field image in today's Astronomy Picture of the Day, there are an awful lot of them, filling a significant fraction of the sky in the image. But then you have to take account of the spaces between the stars in those galaxies, so that each galaxy image we see is extremely faint, being mostly the view straight through the galaxy, and only a tiny fraction star surface.
Every day I learn more. And every day I realize I know less that I thought I did.
Some people say that is the beginning of wisdom. Others say it is the beginning of Alzheimer's.
I think the hourlong version is as short as you really want to go.
http://www.youtube.com/watch?v=NfBT6Sg-4KQ
Massively cool!
This mass exodus away from our own solar system is not without cause. In fact it seems the spread has accelerated in a time-line that coincides with the rise of the tea party. Research has also determined a similar rise in this spread occurred as we entered the nuclear age and before that when the Inquisitions was the norm.
Head Scientist S.S. Lollipop stated "It is obvious that we live in a very uppity universe."
Maybe they are moving away because they see the Earth as a contagion. We need to contain the diseases and start healing the Human race, that would also include the ground on which we walk on. With all the drilling going on, we are hollowing out the Earth. We are consuming it, it is disappearing and so will we.
The video is correct (though some of its wording might be misleading). The headline on the post is unambiguously dead wrong. As Edward Mokurai Cherlin's comment points out, Doppler redshift is responsible for the fact we can't see the cosmic microwave background that would otherwise fill the sky with light, but the shift from visible to infrared of remote galaxies is relatively minor in determining what we can see. Incidentally, something the video neglects to mention is that almost all the universe will be forever invisible to us because thanks to the expansion of space it's moving away from us faster than the speed of light (and no, that doesn't contradict special relativity).
The stars are disappearing because - in the name of progress -- they gave us electricity and took the stars away. Typical of most gifts from corporations, government etc. They give us new prescriptions for new illnesses created by them -- the pharma's I mean.
And, further to this, we are given permission - in fact - encouraged to destroy ourselves and our planet with their 'freebies' that get us hooked into habits which become uncontrollable.
saw an ad this morning.
The Evil EPA and the restrictions on using cheap coal. Vote for Romney.
Problem is people forget the pre EPA world, non smoking city dwellers hacking up crud, the stench of the city getting into clothes and following you out to the rural home, deforestation downwind from coal fired industries, industry injecting waste into water tables and simply dropping barrels of waste in a field and being able to say the waste was disposed of.
Those who weren't alive to forget the pre EPA world won't hear about that world from sources they trust.
I just learned sumpin' new. Bajillions is a scientific figure. Now please give me the rest of the story. It seems obvious to me that Bajillions would exceed mere billions but then again it would be less than a zillion or a googlplex. Am I guessing correct? Is it ,as one might assume, less than a trillion?
Ask Carl Sagan.
Bajillion is a totally unscientific term. There are a hundred billion (1e11) stars in a single ordinary-sized galaxy, and something like 170 billion (1.7e11) galaxies in the Hubble volume. That gives us, very approximately, two grillion stars. ^_^
Oh, all right, 1e11 x 2e11 = 2e22, or twenty sextillion.
This isn't rocket science, you know, just arithmetic. Archimedes explained how to work with much, much bigger numbers in The Sand Reckoner.
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Kids, The Cons wanting to end PBS has nothing to do with Big Bird.
Cons want to end PBS because their trying to kill true journalism. ie: Frontline & Moyers.
True Journalism is inherently Liberal.
In the Cons "journalism" ideology and dogma give the Cons the answer before the question is asked and the Con "Journalist" digs up what supports the preordained answer and discards that which doesn't. If there is nothing there to support the preordained answer the Con fabricates their own "facts".
In true journalism a Journalist is asked a question which they attempt to answer by following the Facts wherever those Facts take them. The Liberal part is being able to change the direction of the investigation when the evidence points in a different direction.
Thats dangerous.
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Even more than journalism, the Religious Right considers PBS to be one of its worst Secular Humanist enemies in the Culture Wars over racism, bigotry, pseudo-science, and so on. Which, to be fair, PBS covers regularly. So it does come back to journalism again.