# Which hit first the hammer or the feather?

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• September 5th, 2008, 06:19 AM
KALSTER
Quote:

according to the video clip
That's the problem right there.
• September 5th, 2008, 10:34 AM
Scifor Refugee
Quote:

Originally Posted by GrowlingDog
This must have been mentioned already but i just haven't the energy to go thru 7 pages to see. Did not this exact experiment take place on the moon by one of the astronauts of Apollo 12 or 15? I have seen a video of it as child. Oh, and just in case you haven't seen it, they both landed at the same time, wow what a surprise.

The time difference in this thread's original scenario was somewhere around the order of 10^-21 seconds - not something that could be measured from looking at the video.
• September 5th, 2008, 12:27 PM
John Smith
For a time interval of 10^-21 seconds as mentioned in the previous comment, even the light would travel only 3x10^-13 meters, a distance much smaller than the size of an atom.
With the moon acceleration, the distances traveled by the hammer and the feather for 10^-21 seconds would be within the range of (g_moon x t^2 / 2), or 10^-42 meters, which is immeasurable.
Nobody even knows what happens at such small distances, it is a matter of quantum fluctuations.
One should use common sense and just conclude that both hammer and feather would fall down at the same time.
• September 5th, 2008, 12:38 PM
Scifor Refugee
Quote:

Originally Posted by John Smith
Nobody even knows what happens at such small distances, it is a matter of quantum fluctuations.

One should use common sense and just conclude that both hammer and feather would fall down at the same time.

Yeah, that came up before as well. But the guy who wrote the OP was careful to specify "any time difference no matter how small". The difference is indeed non-zero for the normal newtonian calculations.
• September 5th, 2008, 12:56 PM
John Smith
Indeed, "the normal Newtonian calculations" do not hold strictly anymore for atomic and subatomic distances.
• September 5th, 2008, 03:33 PM
dejawolf
such ado over a hammer and a feather.
i want to ask a question too.
you have a 300m long ship, and a feather. each are placed centerpoint side by side to each others center of gravity.
which means the feather is 150m further away from the moon surface than the ship.
so the ship will strike first.
similarly, it entirely depends on how the hammer is aligned.
it also depends on the size of the hammer. a very tiny hammer and an ostrich feather is a completely different animal, depending on how each are aligned.
• September 6th, 2008, 08:03 PM
William McCormick
Quote:

Originally Posted by Zelos
Hell NO
they will fall at the same speed, im going to prove why by using hte formulas newton used

F=m<sub>2</sub>a
F=Gm<sub>1</sub>m<sub>2</sub>/r²
m1 is the mass of the moon, m2 is the mass of the second object
therefor
a=Gm<sub>1</sub>/r²
we get rid of m2 on both sides
oh well i be damn, it doesnt matter what mass the second object has, it will fall at the same rate. So please dont try this, its elementary knowledge that everything fall at the same rate aslongest not other forces are involved

When you take away the air. They are identical. They are objects both made of balls of electrons. Neither actually has any weight. They only have their ability to repel. As gravity high speed electrons push them towards the moon. The ambient radiation the gravity, just sees balls of electrons. And just repels balls of electrons.

If anything you would think the feather would be carried more easily by gravity then the hammer. Less mass to positively accelerate.

However in actuality there is a light gaseous atmosphere of H2O around the moon, that could allow the hammer to hit first.

Sincerely,

William McCormick
• September 6th, 2008, 10:44 PM
GrowlingDog
Quote:

Originally Posted by John Smith
http://nssdc.gsfc.nasa.gov/planetary...ther_drop.html
Obviously, both hammer and feather landed at the same time.
The question is why they fell down FASTER (according to the video clip) than it should be observed on the moon.
and measure the time while watching the video.

If it makes it any more mysterious, i can easily make that video clip run faster or slower, which would you prefer. Hell, i can probably get the hammer and feather to stop in mid air for a second then fall at great speed, now that would really have you stumped wouldn't it.
Of course, i'm not selling a moon conspiracy book yet so maybe i will wait until then. :D
• January 21st, 2009, 04:16 PM
Megabrain
Nice to see this one still going.....
• January 23rd, 2009, 05:48 AM
Sudhamsu
Quote:

Originally Posted by dejawolf
you have a 300m long ship, and a feather. each are placed centerpoint side by side to each others center of gravity.
which means the feather is 150m further away from the moon surface than the ship.
so the ship will strike first.

If we consider two point masses, one heavier than the other, it would give the result we are expecting. The heavier point mass would surely pull the moon towards it self (the center of mass of the point masses to be exact). If the heavier mass is more more more heavy heavy heavier than the lighter one, then I think the time difference of the collisions would be close to considerable.
• January 30th, 2009, 04:53 AM
Bender
This is a rather amusing thread.

The posed "fun fact" is both right and wrong:
We start of with a simple model to describe reality: F=mg, which is very accurate in the vast majority of applications. Then we want to improve the accuracy of the model to be able to discover a difference between the hammer and the feather. In the proposed model, the hammer will indeed hit the moon first, but it is a strange choice of model and it completely fails to accurately describe reality in this case.

If you improve the accuracy of a model, the first thing you add is the larger neglected influences. This model only adds one of the smaller ones.

First of all, I think it is strange that part of Newtonian mechanics is added, but another, more important, part is neglected: the attraction force between moon and object changes with distance.
Either the distance between the centre of gravity is equal for both hammer and feather, and the hammer wins easily because it has less distance to travel. Or the distance to the closest extremity of hammer/feather is taken equal, and the feather wins, because its centre of gravity is closer to the moon.

Now, on a more or less realistic moon, the surface consists of dust. Even if you spread it out as best as possible, the best homogeneity you can get is roughly the size of a dust particle, which is probably between a nm and a mm, much larger than then any calculated effect. This effect could play in favour of both the hammer and the feather, but on average, the hammer will have the advantage, since it has a larger surface to catch a higher dust particle.

The model also neglects any magnetic field, deviations of the gravitational field, remanent electrical charge of the moon, hammer and feather. The photons bombarding the hammer and feather from all directions (mostly from the sun) will also have a considerable effect.

Lastly: atmospheric drag: I don't know what the moon atmosphere consists of, but suppose it's hydrogen. One hydrogen molecule weighs roughly kg, only less than the feather. The feather only has to hit a few of those to completely screw the calculation. IIRC, there are also charged dust particles floating around the moon. One of those would be a lot heavier than the hydrogen molecules.

In conclusion: nice mathematical trick, but the proposed mathematical model completely fails to properly describe the problem. Until someone takes all these variables into account, we'll just have to assume they both hit at roughly the same time.

(I can't calculate even the known variables, since I don't have a calculator on this computer that can handle more than 16 decimals)
• January 30th, 2009, 06:08 AM
Harold14370
Quote:

Originally Posted by Sudhamsu
If we consider two point masses, one heavier than the other, it would give the result we are expecting. The heavier point mass would surely pull the moon towards it self (the center of mass of the point masses to be exact). If the heavier mass is more more more heavy heavy heavier than the lighter one, then I think the time difference of the collisions would be close to considerable.

But the hammer and feather are falling side by side, so the feather also gets the benefit of the hammer's influence on the moon, no?
• January 30th, 2009, 06:35 AM
Sudhamsu
Quote:

Originally Posted by Harold14370
Quote:

Originally Posted by Sudhamsu
If we consider two point masses, one heavier than the other, it would give the result we are expecting. The heavier point mass would surely pull the moon towards it self (the center of mass of the point masses to be exact). If the heavier mass is more more more heavy heavy heavier than the lighter one, then I think the time difference of the collisions would be close to considerable.

But the hammer and feather are falling side by side, so the feather also gets the benefit of the hammer's influence on the moon, no?

Yes, it will. But we do not know their alignment, right? We can have every freedom to think that the feather is from a large bird, and the hammer is a baby's tool. This will of course complicate things. I think what the thread-starter wanted to show was concerned with two masses, one heavier than the other. So, considering point masses would make it easier for us to understand the concept.
• January 30th, 2009, 06:41 AM
Pong
Quote:

Originally Posted by Harold14370
Quote:

Originally Posted by Sudhamsu
If we consider two point masses, one heavier than the other, it would give the result we are expecting. The heavier point mass would surely pull the moon towards it self (the center of mass of the point masses to be exact). If the heavier mass is more more more heavy heavy heavier than the lighter one, then I think the time difference of the collisions would be close to considerable.

But the hammer and feather are falling side by side, so the feather also gets the benefit of the hammer's influence on the moon, no?

Like say the hammer handle is a feather, pointed away from a symmetrically positioned free feather?
• January 30th, 2009, 06:56 AM
KALSTER
Quote:

Originally Posted by Harold14370
Quote:

Originally Posted by Sudhamsu
If we consider two point masses, one heavier than the other, it would give the result we are expecting. The heavier point mass would surely pull the moon towards it self (the center of mass of the point masses to be exact). If the heavier mass is more more more heavy heavy heavier than the lighter one, then I think the time difference of the collisions would be close to considerable.

But the hammer and feather are falling side by side, so the feather also gets the benefit of the hammer's influence on the moon, no?

From the OP:
Quote:

I long ago concluded if the hammer and feather were dropped at different times the hammer would take the least time to contact the moon's surface, since the moon would also be attracted to the hammer, and the mass of the hammer is larger than the mass of feather ergo the combined acceleration would be greater when the hammer was released.
The hammer will hit first.
• January 30th, 2009, 07:09 AM
Bender
Quote:

Originally Posted by KALSTER
The hammer will hit first.

In an impractical model of reality.
• January 30th, 2009, 07:11 AM
KALSTER
Quote:

Originally Posted by Bender
Quote:

Originally Posted by KALSTER
The hammer will hit first.

In an impractical model of reality.

Agreed.
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