Not a lot of water?

[Cody]

Universe Today

[Gimi]

Cool comparison.
Idea: do the same with the atmosphere, and be surprised how thin the Earth's atmosphere actually is.

[Cody]

Cool comparison.
Idea: do the same with the atmosphere, and be surprised how thin the Earth's atmosphere actually is.

I've no real idea, but I suspect that the atmosphere would be a much larger sphere than the water... anyone know the numbers?

[Disembodied]

The atmosphere image (alongside another water one) is available here. Although much would depend on what pressure the atmosphere sphere is under ... I think here it's supposed to be at 1 bar.

[Cody]

<nods>

[Gimi]

I find the atmosphere image more surprising. All the gas around the entire world in that little ball.
Good find El Viejo (and Disembodied).

[Smivs]

<Smivs takes a deep breath...goes for a drink>

[SandJ]

I was surprised the first time I saw a high-res photo of the earth in profile that mountains simply do not register. Doing the sums:

Diameter of the Earth: 12,800 km

Display it on a screen of 1280 x 1024 and give 90% of the height to the Earth means the diameter is spread across 920 pixels = 14 km per pixel.

Everest is 8.8km high so barely warrants a pixel to itself.

But at the top of Everest, you need bottled air to breathe.

So the usable atmosphere will not be visible on a picture of the Earth this big.

The highest clouds that are normally visible are at 18km - two pixels from the surface. (The very highest clouds that can occur are at up to 85 km, which would be 6 pixels, but you've probably never seen them.)

This has made me wonder for some years: just how often are Earth photos photoshopped to make the atmosphere visible because we expect it to be visible?

Edit: On this large NASA 'blue marble' photo of the earth, the breathable atmosphere is about 1 pixel thick. The blue band is 18 pixels thick, being about 125 km.

[Disembodied]

This has made me wonder for some years: just how often are Earth photos photoshopped to make the atmosphere visible because we expect it to be visible?

I think the NASA "blue marble" image is still the only image of the whole Earth ever taken by a human being: the others are either composites, or taken by unmanned spacecraft (like the photo that Voyager 1 took in 1990, where the whole Earth is 0.12 pixels across. ). But shots from space which show the atmosphere are usually taken from low orbit, where the atmosphere line would be visible: I can't think of any full-planet photographs that show an atmospheric ring, although there are quote a few illustrations/mockups which do. You're probably right, people think it makes the image look more "real".

[Cody]

This is the original (I think) Apollo Blue Marble image - still the best.

[Cody]

Whereas Europa has plenty of water for its size!