Science questions not worth a thread I: I'm a moron!

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By what mechanism would light reflected from Earth be polarized? I would think that the light would be just as scattered as light emanating from the sun.

I don't think that they are looking at scattered light, which should indeed have isotropic polarization. I guess they are looking at directly reflected light. That light is reflected because the atmosphere of the planet has a higher refractive index than the vacuum in space.

If you take a look at the Fresnel formulas that are relevant in that case, you'll see that they depend on polarization if the incident light is not perpendicular to the surface. Especially interesting is the case when the light is shining on the surface at the Brewster angle: In that case the reflection of the polarization parallel to the plane of incidence drops to zero, while the polarization perpendicular to the plane of incidence is still partially reflected. So if you reflect unpolarized light at a surface with a real refractive index at the right angle, the reflected light will have perfect linear polarization.

For the atmosphere of planets you have to generalize these formulas to deal with a gradient change in refractive index, but the principle is the same. So if you collect light that has been reflected from an atmosphere on an angle that is not perpendicular to it, the light will be polarized. If you can measure the angle where the light is maximally polarized, you could then calculate the refractive index of the atmosphere. If you then do that for different colors, you might get some information about the density and composition of the atmosphere.

At least that is what I guess is the basic principle.
 
I was Googling the Venus surface pics from Venera, and I noticed that you can see quite a ways away. How can that be, considering the air there is 100 times thicker than Earth's air at sea level?

I was under the assumption it'd be like pea soup fog or something?
 
I think with fog, you're not seeing water in a gaseous state. Rather, you're seeing a bunch of tiny droplets of water that are diffusing the light.

Carbon dioxide is just a bunch of molecules swimming in the air, so there's not much to absorb light, hence clearer pictures than what you might expect.
 
Also, keep in mind that CO2 doesn't really absorb or scatter much light in the visible. On Earth, the scattering of light is mostly due to the Nitrogen, and to a smaller extent, Oxygen. To get the same effect with Rayleigh scattering with CO2, you're going to need a significantly greater amount to compensate for the effective cross section of CO2 to visible light.
 
Is there any way to even take a stab at calculating which single species has the greatest total biomass? Like, I know that ants probably have a worldwide biomass several orders of magnitude higher than humans, but there are probably thousands of species of ants.

I have read somewhere that the cattle is the animal species with the highest total biomass and that sounds reasonable to me. But pines and spruce together cover huge parts of Canada and Russia so the species with the highest total biomass is propably one of them.
 
I was Googling the Venus surface pics from Venera, and I noticed that you can see quite a ways away. How can that be, considering the air there is 100 times thicker than Earth's air at sea level?

I was under the assumption it'd be like pea soup fog or something?
Besides what contre and Bluemofia said ( none of the gases in the lower venusian atmosphere is a strong absorvent in the visible spectra ), I could point that the higher venusuian atmosphere is actually like you would expect ... but because of the sulfuric acid cloulds , that scatter light in the same way that our water clouds do ;) In fact you can see that direcly in the Venera images, that show the surface iluminated by a diffuse glow and without much of discernible shadows, the same effect you would have in a cloudy day in Earth
 
Google has failed me. Can anyone find a complete list of EVERY celestial event that has happened in the last 30 years or so? (I mean, eclipses, transits, comet sightings, etc. No man-made stuff.)
 
Are we talking just Earth? Even that sounds like a tall order. I'd recommend compiling it yourself.

Keep in mind that there's many comets visible every year, just rarely brilliantly so like Halley's or Hale-Bopp
 
"Celestial event" is kinda vague... What do you define as an event? Does an Io eruption count as an event? What about meteor impact on an object (On the Moon? Jupiter? Earth? etc.)? Does it have to have a minimum size for the meteor impact? Solar flares? CMEs? Gravitational microlensing events? Supernova events? Nova?

Harvard's minor planet center site is actually a good starting place. They publish a lot of IAU catalogs for events and stuff.


What about asteroid sightings/discoveries? Start searching. This will take a while. You've got comets in this list too.
http://www.minorplanetcenter.net/ (General page)
http://www.minorplanetcenter.net/iau/lists/CometLists.html (More specific comet list)

If you just want bright comets:
http://www.icq.eps.harvard.edu/brightest.html

Transits are actually quite easy, because they only occur for Mercury and Venus:
http://eclipse.gsfc.nasa.gov/transit/transit.html

Eclipses there's a database for them because they're easy to predict, and spectacular enough for people to want to see/plan ahead to see (I planned to go to China in 2009 to see the eclipse in 2006; pity it rained on that day):
http://eclipse.gsfc.nasa.gov/SEsearch/SEsearch.php

Supernova list:
http://www.cbat.eps.harvard.edu/lists/Supernovae.html

Nova list:
http://www.cbat.eps.harvard.edu/nova_list.html
 
Actually, I was aiming for solar and lunar eclipses (the ones here on Earth, that is; cuz I know they happen elsewhere in the Solar system too :p ), major comet sightings, and objects transiting the sun (not just Venus. ;) ). :)

Because I want to check the dates those happened and compare them with weather records so I can see for myself if my perception of "always missing out on these events as a result of clouds and other inclement weather" is accurate or not. :)
 
As in the passenger-size mirror? I believe it's slightly concave (as opposed to the driver's side which is flat) and as such, it makes objects appear smaller. So in your driver's-side mirror an object 25 feet away looks X size, but in the passenger-side mirror, the same object at the same distance looks smaller. Your brain interprets that as further distance.
 
For all you java programmers out there, I have a question.

I've recently written a class involving a while(true) loop involving Thread.sleep. My emulator issued a heads-up to me, stating that I've used a Thread.sleep in a loop. Some googling has informed me that it may cause performance issues if I use a Thread.sleep during a loop. The program compiles and all; the emulator is merely introducing a tip to me that doesn't influence whether the program can run or not.

My question is: is it truly a problem if I use a Thread.sleep in a loop? Or can I reasonably ignore this warning?
 
For all you java programmers out there, I have a question.

I've recently written a class involving a while(true) loop involving Thread.sleep. My emulator issued a heads-up to me, stating that I've used a Thread.sleep in a loop. Some googling has informed me that it may cause performance issues if I use a Thread.sleep during a loop. The program compiles and all; the emulator is merely introducing a tip to me that doesn't influence whether the program can run or not.

My question is: is it truly a problem if I use a Thread.sleep in a loop? Or can I reasonably ignore this warning?
I'm not sure, but I think that question might be better off put in the "Computer Questions" thread, here http://forums.civfanatics.com/showthread.php?t=337877 . :)
 
New question:

Let's say we have an asteroid in the main asteroid belt. It is rocky, and a diameter of 68.1162 kilometers. Now, a foreign object comes in. It is icy, and has a diameter of 46.84 kilometers. The icy object collides with the asteroid, coming in from the side, at an angle of 80 degrees. The distance between the two shrinks by 28.57 kilometers per second.

The collision occurs 3.5893 AU from Earth. Would we be able to detect the collision?
 
New question:

Let's say we have an asteroid in the main asteroid belt. It is rocky, and a diameter of 68.1162 kilometers. Now, a foreign object comes in. It is icy, and has a diameter of 46.84 kilometers. The icy object collides with the asteroid, coming in from the side, at an angle of 80 degrees. The distance between the two shrinks by 28.57 kilometers per second.

The collision occurs 3.5893 AU from Earth. Would we be able to detect the collision?

If we had a sufficiently powerful telescope pointed at the collision site and there was no other object in the way, we should be able to watch it.
 
I'm curious why there are 6 significant figures in this question :dubious:

Surely a rocky asteroid of that magnitude will not be spherical down to a meter in elevation!
 
I'm curious why there are 6 significant figures in this question :dubious:

Surely a rocky asteroid of that magnitude will not be spherical down to a meter in elevation!

If it's an alien mothership....
 
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