what color would the umbra of a sunspot be if we could see it alone?
136356
Use the Wien law:\n\nlambda(angstrom)= 3x10^7 / T(ºK)\n\nIf for sunspot T= 4600ºK, then\n\nLambda= 6520 angstrom , so color umbra is red.
332281
If you could find a gas that had a semi-stable quasistate that when excited would release a photon with a wavelength corresponding to "black", then yes.  However, I don't know exactly what band that would be.  The closest you'd be able to get to black would be a dark ultraviolet, or if you could overlap in phase multiple color lasers which could possibly (but unlikely) add together to make the appearance of black.  Most likely, you're out of luck.
281307
When the Sun has Sunspots you can see that they revolve around the Sun.\n\nIt basically rotates similar to how the planets rotate.\n\nRotate not orbit.
268285
u can only see white when u look at the stars because u are seeing the combination of all the visible radiation. U can clearly make the colors through a telescope with a spectroscope attached. That is how they can tell the chemical composition of stars. However there are a few stars in the sky whose colors are plainly visible. (Betelgeuse in Orion the hunter.) but this has to do with the stars temperature. red for cool stars and blue for very hot stars.
483327
This solution probably has fluorescence at UV (ultra violet) wave length. try looking at it in a room with red light, if there is no light using the lenses then it's confirmed. but you can't simply identify it this way. you have to know the exact wave length that it has fluorescence at. even then you might not be able to identify it. try using UV-visible spectroscopy and when you have its spectra, you can identify it. for more information see: principles of instrumental analysis by Skoog
76134
A sunspot is a region on the Sun's surface (photosphere) that is marked by a lower temperature than its surroundings and intense magnetic activity, which inhibits convection, forming areas of low surface temperature. Although they are blindingly bright, at temperatures of roughly 4000-4500 K, the contrast with the surrounding material at some 5700 K leaves them clearly visible as dark spots. Next year is expected to be a cyclical peak in the sunspot cycle
563619
What sort of features are you hoping to see? An 80mm would be enough to see the red spot on Jupiter and the rings of Saturn. It probably won't make out the Cassini division in the rings, though.  You should also be able to see cloud bands on Jupiter. When looking at Mars, you might be ble to see some dark splotches during excellent seeing conditions, but Mars is a hard object for everyone. The most you will ever see on Venus is the phase because the clouds obscure everything else. Mercury is a hard object and is way too small to see anything. Uranus will be a blue dot as will Neptune. You won't see Pluto.\n\nI hope this helps!
14674
ah, i actually remember thinking that once... i always had a lot of questions like that, always so curious about stuff... that's why im a physics major, it explains so much... actually, while we may not be tasting or smelling the same thing, we are all seeing the same colors.  this is because each color has corrosponding wavelengths and frequencies of light on the electromagnetic spectrum.  Only a very small portion of this spectrum is even visible light, and we all agree on that.  the colors you see from objects are just the wavelenghts of light that are not absorbed by that object, so therefore are reflected. so we are definately all seeing the same frequencies of light... its easier to understand with sound, if you pick different frequencies, it's a higher or lower pitch.  we can all definately agree on the pitches of sound because we can agree on whether or not the pith is higher than another pitch. if you pick a frequency on the electromagnetic spectrum in the visible light range, that frequency will correspond to a certain color. violet is the color with the wavelength of the highest frequency, meaning it has the highest energy(E=hf where h is planck's constant so energy is directly proportional to frequency.) red has the lowest frequency, and therefore energy. the colors go in order of lowest to highest energy as follows: red, orange, yellow, green, blue, violet. it is is definate that what everyone views as violet is what has the highest energy, and what everyone views as red has the lowest.  and the colors as we know them, kind of blend into each other as you go up in energy, like starting with red you can have red orange and keep adding orange till you get to orange, then add some yellow and so on.. the colors blend nicely. if someone viewed lets say green instead of orange... well then red and green wouldnt mix so well now would they? if you think about it, the colors go "up" in energy steadily just as sound goes up in pitch steadily, so we do all view colors the same.  i hope i conveyed my thoughts properly and that made sense :)
366407
I think white+creme or sky blue. purple light yellow
110220
It will be from way out on a plane based on our orbital track. I think the intensity of the sun will block out the view of whether or not it goes behind or in front of the sun. The center of the universe, even though it is a non-existent place, for arguments sake, would be moving as everything in the universe is dynamic. (There is no end to infinite, therefore the center cannot be defined.)
288413
the Sun and another point where there is no object
153895
Well it's impossible to see stars when the sun is up, and Venus is the only planet visible during the day, so there is no way all those bodies could have been visible at the same time. There might have been some sort of alignment, but it would only have been calculated, not observed.
647943
A "sundial" casts a single shadow from its gnomon (the point that comes out of the top). \n\nAn "armillary sphere" however is a different device altogether. It helped in the understanding of the earth and stars. Many armillary sheres were created with the sun in the middle, therefore casting numerous shadows depending on which point in space you were.\n\nWhile on earth at 1:38pm a sundial will cast one shadow.\n\nCheck out these links for more information:
138047
As there is no source of light in the sky apart from the Sun, then everything we see is reflected light. ; Thus the sky can only look black if all reflective matter is removed.
234041
The same reason that your carpet isn't or your tee shirt isn't. The only light we see anything by is sunlight, but the light of the sun is reflected back in different colours according to the material reflecting it; in the case of the moon, grey dust.
454594
I think the rings of Uranus are too tenuous to occlude starlight to a detectable degree. I don't believe those rings were actually discovered until we sent out probes to a point where they were directly visible. \n\n30 NOV 06, 1953 hrs, GMT.
178998
Most likely Venus, as those above me have stated, but Jupiter is also a possibility.  \n\nStarmaps are readily available on the internet, and that would tell you for sure. \n\nHowever, a more fun way to find out would be to take a telescope outside and look at the planet.  Even a very low-end model telescope will have the resolution to see the moons of Jupiter.  Watch it for a week, if you don't see any moons or the giant red spot, it's Venus.