Skyline

[Julie]

Where does the sky begin in relationship to the earth? Does it begin immediately above the ground at our feet, or does it begin higher in the atmosphere? If it is higher, how high is its beginning? Also, if it is higher, how wide does that make the "skyline" or "horizon"?

What is technically, according to astronomers, the earth's border?

[Josh]

Hi Julie and welcome to the forum ...

There are a number of layers to the Earth's atmosphere. Basically the "sky" starts right above the ground. If you're not on the ground (or attached to something that is) then you're either in the ground or in the sky. The first part of the atmosphere is called the Troposphere where temperature decreases proportionaly with altitude (for that reason it's also called the gradient layer). This is up to between 8 and 16 (ish) kilometers depending where you are. Next is the Stratosphere. This is about 30 kilometers thick. These two are also called the lower atmosphere. Next is the Mesosphere which is the middle atmosphere and terminates at about 80km above the Earth. Above this is the upper atmosphere with the Thermosphere, Exosphere and Ionosphere.

As to where space begins is a bit of a tenuous ask. The atmosphere thins as you increase in altitude and because of that it's difficult to say exactly where space begins. Even at over 150km above the Earth there are still traces of breathable gases but this area is definitely considered space. NASA, for eg, awards astronaut status to anyone who has flown at or over 80kms above the Earth. So basically Space depends on what you are trying to do. For a better answer you can go here.

Hope this helped...

Josh

[rahuldandekar]

In fact there is no "Sky". It is just that the colour blue in sunlight spreads more than the others and whenever we look upwards, we see blue only. That is what we call as the "sky".

[Julie]

It has been awhile since I have been able to visit this forum again. I appreciate your responses.

Josh, your explanation is very helpful & detailed. Thank you.

Rahuldandekar, thank you for your response. From your explanation, it sounds as if there is no sky at night. When it is dark at night and the sky is no longer blue, I still refer to the sky above us.

[rahuldandekar]

Yes, but then yuo see no colour, you see through the atmosphere, into the dark little universe beyond it. Thats why the 'sky' is dark at night.

[Julie]

So then reference to the sky does not include the rest of the universe? Why is it that the general public and songwriters refer to the "stars in the sky"? I'll have to change the words to a song I am writing too. That is very interesting! Thank you.

[rahuldandekar]

Yes the sky is only a thing we imagine to be in the sky. In fact ,in the day, the blue colour prevents us from seeing the stars. But as there is no such obstruction in the night, we see stars.

Anyway, don't change the poem. Poems are based on imagination and atrs and hard science should remain seperate.

[Julie]

Thank you Rahuldandekar. I'm glad to hear I don't have to be scientifically correct with my art.

Sorry for my delayed response. It has been an unbelievably long time since I have been back to this website. Your posting was in December and it is February already. I'm surprised the posting is still on the site.

[DippyHippy]

Hey Julie

Just in case you decide to come back a little sooner next time (and we sincerely hope you do ), all topics and postings remain active, no matter how long it's been since anyone's replied.

Having said that, if Fraser starts running out of space (no pun intended&#33 we might have to clear out some of the older topics...

[Phillips]

I might be able to add two things to this topic.

First: I've recently read that the `sky is rising' - that is the various atmoshere levels are moving up several thousand feet each (mixing more). Raising the `perception' of the sky.

Second: I once saw answered in an astromony magazine `If I saw a meteorite streak thru the sky above my head - how `far away' would the `same sky' be visible. The answer (if I remember correctly) was based on the `heighth' of the shooting star (overhead would be seen furthest away) and that value in relation to the curvature of the earth. (Just like `how far can you see out to sea&#39. If I remember right, a `shooting star' directly overhead (entering earths atmosphere 100,000's ft up visibly) would be visible for up to about 200 miles in all directions from the observer.

[Faulkner]

Watch out, Julie, the sky is falling on your head!!!!!