How Do We Know That The Sun Is 93 Millions Miles From Earth.

[nailit]

Apperently, over the years there have been a number of different calculations for the above. How have we now decided that the sun is where it should be and can THAT calculation change again?,

[Buenchico]

Maths!
http://curious.astro.cornell.edu/disclaimer/41-our-solar-system/the-earth/orbit/87-how-do-you-measure-the-distance-between-earth-and-the-sun-intermediate

[jim360]

Tl;dr: proper trigonometry.

[Buenchico]

BTW, while the Earth's orbit around the Sun can now be calculated extremely accurately, it has to remember that the orbit is elliptical, rather than circular. So the distance between the two doesn't remain constant. At its closest the Earth is only 91 million miles from the Sun, while at its furthest it's 94.5 million miles away.

[Buenchico]

PS: Don't forget to add on the extra 15cm every year ;-)

https://www.newscientist.com/article/dn17228-why-is-the-earth-moving-away-from-the-sun/

[Old_Geezer]

Because we counted the number of feet it was away from us and then divided by 5280.

[Canary42]

Some fascinating material in those links, thanks Chris.

[nailit]

Echo canary, thanks for the links Chris. :-)

[douglas9401]

Well I don't know about anywhere else in the world but up here we determine it by the temperature of the rain. :-)

[IJKLM]

Dpends on what you mean by 'distance to the sun'

Is that to the centre of the sun, or the outermost layer, or the 'surface' of the sun?

And at what time of year?

There is no surface of the sun. There is a layer that emits light in the visible spectrum. That's around 432,000 miles away from the centre.

That temperature in that part of the sun is something like 6000°K

Go further out - over 1 million miles out from the centre - and the temperature in the corona rises to over 1,000,000°K.

If the centre is 93 million miles away, the corona is 92 million miles away (on average).

However, the earth's orbit is not circular. It's an ellipse so that at perihelion, or closest approach (in early January) the earth is 91.4 million miles away from the sun. Six months later (July), the earth has moved around in its orbit and at its furthest (aphelion) it is 94.5 million mies away from the sun.

Like much in science, the more subtle the question, the more complex the answer...

Hope it helps