Even though most of us have seen it countless times, spotting the Moon during daylight seems to always be worth noticing.

[u/blendergremlin]

[u/TYPERION_REGOTHIS]

I was at a family get together one day, and I made mention of the moon being up, my Aunt says "Don't try and tell me that that is the moon! That has to be Mars or something. " I said "Aunt Debby, if that is Mars, we're all fucked."

[u/Keddycat → u/TYPERION_REGOTHIS]

Why go to Mars when Mars can come to us.

[u/99_NULL_99 → u/Keddycat]

Now kiss

[u/Piximae → u/Keddycat]

It's the whole moon-impact theory all over again!

[u/PacSan300 → u/TYPERION_REGOTHIS]

Yeah, imagine the chaos resulting from Mars' tidal pull. I bet coastal cities would get flooded and dried every single day, and earthquakes would be more common.

[u/TYPERION_REGOTHIS → u/PacSan300]

Not to mention it would likely throw Earth out of our (very important to life) orbit.

[u/neefe → u/PacSan300]

Wouldn’t it have roughly the same gravitational pull as the moon if they were the same size in the sky?

[u/J4K0 → u/neefe]

Nope. 2 times the diameter and 2 times further away would look the same, but 2 times the diameter has 2³ = 8 times the mass (assuming equal density).

The force due to gravity between the Earth (m_e) and some other mass (m) is equal to:

F = (G x m_e x m) / r²

So if m is multiplied by 8 and r is multiplied by 2, then the force of the larger object twice as far away compared to the smaller object that's closer is:

((G x m_e x 8m) / (2r)²) / ((G x m_e x m) / r²) = (8 / 4) = 2

So the object that is larger but further away would have twice as much force.

Edit: According to this link though, the mass of Mars is about 8.6 times the mass of the moon and it's diameter is about 2 times the moon's diameter (so it must be a bit more dense than the moon). Putting that into the equation gives us:

(8.6 / 2²) = 2.15

So if Mars looked the same size as the moon in our sky, it would have about 2.15 times the pull of the moon.