Astronomy Picture of the Day -- Hammer Versus Feather on the Moon

NASA ^ | November 01, 2011 | (see photo credit)

[SunkenCiv]

Explanation: If you drop a hammer and a feather together, which reaches the ground first? On the Earth, it's the hammer, but is the reason only because of air resistance? Scientists even before Galileo have pondered and tested this simple experiment and felt that without air resistance, all objects would fall the same way. Galileo tested this principle himself and noted that two heavy balls of different masses reached the ground simultaneously, although many historians are skeptical that he did this experiment from Italy's Leaning Tower of Pisa as folklore suggests. A good place free of air resistance to test this equivalence principle is Earth's Moon, and so in 1971, Apollo 15 astronaut David Scott dropped both a hammer and a feather together toward the surface of the Moon. Sure enough, just as scientists including Galileo and Einstein would have predicted, they reached the lunar surface at the same time. The demonstrated equivalence principle states that the acceleration an object feels due to gravity does not depend on its mass, density, composition, color, shape, or anything else. The equivalence principle is so important to modern physics that its depth and reach are still being debated and tested even today.

[SunkenCiv]

[Credit: Apollo 15 Crew, NASA]

[SunkenCiv]

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[cripplecreek]

Watching "The Universe" last night and I think we need an Amy Mainzer rule for space threads.

[VanDeKoik]

We never went to the Moon.

/x-files music

[Paladin2]

This Amy Mainzer?

[Bullish]

So let me get this straight.... If you dropped Obama and Biden’s brain at the same time....

Oh never mind.

[gargoyle]

[stormhill]

So let me get this straight.... If you dropped Obama and Biden’s brain at the same time....

Yes, you got it, they'd both float

[DuncanWaring]

That would be like dropping Santa Claus and the Tooth Fairy at the same time.

[SunkenCiv]

It’s a good idea, because the only way I could get anything out of that show would be to listen and not watch. ;’)

[SunkenCiv]

;’)

[SunkenCiv]

When she was written out, the show passed its peak. Still like it though.

[SunkenCiv]

[SampleMan]

The hammer will fall slightly faster, as every mass has it’s own gravity. The hammers greater mass has greater gravitational pull on moon.

[rawcatslyentist]

>"If you dropped Obama and Biden’s brain at the same time..."

You'd be stoned stupider than Ozzy.

[cripplecreek]

The hammer will fall slightly faster, as every mass has it’s own gravity.

I hadn't thought of it that way but it does make some sense. You would need a very long fall to show the difference to the naked eye.

[RedMDer]

[DuncanWaring]

The hammers greater mass has greater gravitational pull on moon.

That's true, but the "greater gravitational pull" is balanced by that fact that there's a greater mass to be accelerated.

[jmacusa]

“Brain’’? Obama and Biden!?! What makes you think either of those two have a brain?

[cripplecreek]

Also true.

You could move a supermassive black hole with a feather if you could anchor the feather somehow and had a few billion years to do it in.