# If there was no earth,

1. Jan 13, 2013

### cdux

If there was no earth, what would be the acceleration of gravity from here from the Sun?

2. Jan 13, 2013

### Staff: Mentor

This is a fairly simple thing to figure out. Is this for a homework assignment?

Get on wikipedia find the the mass of the sun and go from there.

3. Jan 13, 2013

### cdux

It's not but I realize it's easy to find out:D Nevermind.

4. Jan 13, 2013

### Staff: Mentor

5. Jan 13, 2013

### marcus

Two easy things to remember: distance to sun ≈ 150 million km
earth orbital speed ≈ 30 km/second.

v2/R
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of course our distance to sun changes by a few percent during the year. the earth orbit is not perfectly circular. so the acceleration due to sun gravity at this distance is going to change a little.

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I would bet this is not homework, just someone who is curious.

You could use Google calculator too. It knows "mass of sun" and it knowns "G" the newton gravitational constant and it knows "AU" the astronomical unit (mean distance to sun).

So probably you could type into google window "G*mass of sun/(AU^2)" and get it.

Yeah, when I do that it says 0.006 m/s^2
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But if I didn't have google calculator handy I think I would use "v-squared over R"
I wouldn't go looking up the mass of the sun, and newton's G constant.
I would just say v = 3 x 104 m/s
so then v2 = 9 x 108 m2/s2

And then I would divide by R = 1.5 x 1011 meters

Last edited: Jan 13, 2013
6. Jan 13, 2013

### cdux

I'm surprised it's so low compared to earth's. Then again, the earth's diminishes rapidly out of low orbit.

7. Jan 13, 2013

### marcus

Well it's good to be surprised, so that's good. But a propos what you said about earth gravity, and practice using google calculator

what would be the acceleration to the earth at the distance the moon is?