I watched a tv documentary recently, among other things it showed the luna videos doubled in speed, these 'double' speed images had the appearance of earthlike gravity. Doesn't that seem odd? Surely the you would have to increase the speed of the video by the square root of 6 in order to get the appearance of earthlike gravity, afterall the Moon's gravity is one sixth that of earth's (9.8/6 m/s), not one quarter.

Available from the NASA website is a video download of Daivd Scott, Apollo 15, dropping a hammer and a feather together to demonstrate the galilean principle. The Hammer is in freefall for at most 1.1 seconds, how far would an object fall from rest under the Moon's gravity?

Distance = 0.5 * gravity * time * time

distance = 0.5 * (9.8/6) * 1.1 * 1.1 = 99cm

99cm the hammer can fall, which is odd as David scott is easily over 6 feet tall, and drops the hammer from shoulder height, a good 150cm?

Suppose that the video was shot on earth, the the speed simply halved, how far does the hammer travel now?

Distance = 0.5 * 9.8 * 0.55 * 0.55 = 148cm

which is interesting, yes?

Mr Freedom.

<font size=-1>[ This Message was edited by: Mr Freedom on 2002-08-22 10:49 ]</font>

I don't know what formula's you're using or would use to figure that out, but how does the maximum distance the hammer could fall be relevant to anything?

Ad hominem deleted by The Bad Astronomer.

<font size=-1>[ This Message was edited by: The Bad Astronomer on 2002-08-20 19:22 ]</font>

The formula is correct, but where did the data come from?

Hey, now, there's a good way to get yourself banned from the BB . . .

Simply changing the time to 1.4 seconds gives you a full 1.6 meters drop. How did you come to the conclusion that the drop only lasted "at most" 1.1 seconds?

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I don't ever recall stating I was a scientist.

"The Hammer is in freefall for at most 1.1 seconds"

Well, I opened my mpg version in a video editing program, and checked the time. I got 1.2 seconds.

I will be using the same formula as you did.

Time: 1.2 s Acceleration: 1.62m/s^2 (from my physics book).

I got the distance to be ~1.17 meters.

And in earth gravity, ~1.76 meters.

"David scott is easily over 6 feet tall, and drops the hammer from shoulder height, a good 150cm?"

Lets assume he is 6 feet. He is bending slightly forward because of the PLSS, and he drops it from below shoulder height (his arms are not held straight forward, but at a slight down angle).

I drew by hand a approximate figure of this, and measured it would be perhaps four feet. I then stood up myself (I am just below 6 feet), and bent flightly forward as I would with a backpack, and held my arm out at a slight down angle. And measured 120 centimeters down to the ground.

CONCLUSION: the footage was shot on the moon.

I don't have any references handy for Dave Scott's height, but the assertion that he must have been over six feet tall is pretty easy to dispute: He flew a Gemini mission which means he can't have been any taller than six feet. That was the requirement for astronauts for that program.

nitefallz, I never said you was a scientist!
But no offence ment, I have been watching too much Bill Hicks recently, anyway, my appaulogies.

The video comes from the NASA site, or one of them I don't know... when the hammer hits the ground, head first, the shaft lurches forwards, at this point it has hit. Please time it yourselves, if anyone has it on VHS or something and some video editing gear then all the better!

I have to dispute your time of 1.2secs, also Armstrong was 5'11", from photographs of he and Scott, Scott is clearly inches taller. His arms look pretty straight out to me. Leaning forward, I don't see that. How much extra height his 'Moon Boots' give I don't know. The drop 120cm... I don't think so. More to the point what about the appearance of earthlike gravity by doubling the speed of the tape, as claimed by the documentary?

I timed the fall several times. It takes from 1.2-1.3s.

best regards,

Dana

Are you all missing the point deliberately? WHY DOES DOUBLING THE SPEED OF THE TAPES GIVE THE APPEARANCE OF EARTHLIKE GRAVITY????

And look I think you people are just timing it wrong..... LOOK FOR THE SHAFT LURCHING if it lurches its already landed.

"His arms look pretty straight out to me"

Because it's not from the side. but since I can see his hands are not level with his shoulders, then either he's leaning forward, or holding his arms down, or both.

"Leaning forward, I don't see that."

Then he would almost be falling backwards because of the weight of the PLSS.

His body is not completely straigh, I see his legs and torso bent in a > sort of posture.

I have to dispute your time of 1.2 secs

Fine, but you have to give more justification. Johnno described how he arrived at his measurement, so we at least have a basis for estimating how accurate it was. You simply state it's 1.1 seconds, but don't say how you measured it.

Armstrong was 5'11"

No. Neil Armstrong's height is given in the Apollo 11 press kit as 5'9". As I stated, more than six feet would have disqualified Dave Scott from the astronaut program. Estimating heights from photographs is inexact. Dave Scott's measured physical height is (or should be) a matter of record. This is the figure you should use, not just a guess.

His arms look pretty straight out to me.

No. You can clearly see the tops of his arms, which you could only see if they were angled toward the camera. Further, the camera is mounted on the LRV and is only a meter or so above the ground. If you can see the tops of his arms from a point of view one meter above the ground, this clearly shows his arms were not straight out.

Further, the J-mission EMU would not allow reaching straight out. The astronauts' capable reaches in the suits is documented.

Leaning forward, I don't see that.

How would you? If he were leaning he would be leaning toward the camera. The notion that astronauts lean forward comes from reading astronaut descriptions, watching other astronaut videos, and viewing other astronaut photos. If you wish to critique Apollo images it is best to do so with a suitable knowledge of the equipment and procedures.

How much extra height his 'Moon Boots' give I don't know.

I do: about an inch. How much would he have sunk into the lunar regolith? Probably about an inch.

The drop 120cm... I don't think so.

Fine, but Johnno has explained how he arrived at his estimate. It would be polite if you addressed his method and showed wherein it was inaccurate instead of simply dismissing it.

More to the point what about the appearance of earthlike gravity by doubling the speed of the tape, as claimed by the documentary?

The documentary shows only a few seconds of video sped up. It then implies that all of the Apollo footage can be similarly sped up with identical results. In fact, if you speed up any appreciable amount of Apollo footage by a factor of the square root of the ratio in gravitational acceleration, you find that very little of it looks natural or suitable.

Speeding up the film speeds up all the motion, not just the vertical drops. You can speed up, for example, the hammer and feather clip and the drop can be made to look as if it had been done on earth, but the motions of the astronauts just prior and subsequent do not look natural (or even possible) at that speed.

Further, we have many examples of ballistic motion in combination with astronaut motion which means that the film speed cannot have been adjusted selectively. Further, as any physicist can tell you, simply adjusting the time scale does not compensate for differences in gravitational effects on ballistic trajectories.

The argument that adjusting film speed can create a convincing illusion of the lunar environment is simply based on selective evidence which doesn't hold up under more careful scrutiny. Of course the producers of the "documentary" weren't really interested in presenting an accurate, fair, or balanced view, so I doubt they expected their viewers to check up on their research. I did.

"Are you all missing the point deliberately? WHY DOES DOUBLING THE SPEED OF THE TAPES GIVE THE APPEARANCE OF EARTHLIKE GRAVITY??"

Earthlike? the difference between your 99cm and 150cm is not anywhere near compareable.


"And look I think you people are just timing it wrong."

I used a video editing tool that lets me go from frame to frame. I took the time of the frame where you see the first movement downwards of the hammer and feather. And then the frame where the hammer hits the ground, before it starts tipping forward.

I'll take the frame numbers for you if you dont believe me.

start: frame 1165 time 38.833s
end: frame 1201 time 40.033s

Or 30 frames per second, 36/30=1.2

Are you all missing the point deliberately?

No, we've just heard this argument a thousand times before. It may be new to you, but we've dealt with it already at length.

WHY DOES DOUBLING THE SPEED OF THE TAPES GIVE THE APPEARANCE OF EARTHLIKE GRAVITY????

It does in this case because a 2X speedup is very close to the 2.4X speedup that would render vertical accelerations in lunar gravity theoretically equal to vertical accelerations in earth gravity.

But in this case we are interested primarily in vertical acceleration. Not so in other cases, such as Scott's movements directly before and after the experiment. Those contain horizontal components of motion that would not be affected by the difference in gravity.

If the lunar footage is simply earth footage that has been slowed down by a factor of 2, then the astronauts would have had to make all their movements at least twice as fast as normal in order for them to appear natural.

And look I think you people are just timing it wrong.

Vigorous protest is not a substitute for an exposition of method. Please tell us exactly how you are timing it.

I said his arms look pretty straight because they do, they may not be perfectly parallel to the ground but they are 'pretty' straight, as someone said there is a SLIGHT angle.

Armstrongs height, I got it from a page that does not appear available right now, a searth gave me this,

Biographical Information
... description: Blond hair; blue eyes; height ... feet 11 inches (1.8 m); weight ... Professional
Background. Armstrong became interested ... He joined NASA's Lewis Research ...
http://www.lennox.k12.ca.us/.../soci...20Home%20Page/ Neil%20Armstrong/biographical_information.htm - 36k - Cached - Similar pages

but like I say the link don't seem to be working.

I know David Scotts height is required... but I cannot find it, I know that using photographic evidence is not exact, but that does not make it 'just a guess'....


He may be leading forwards, but only slightly, just as his arms are only sligtly below the shoulder height.

If a 6' man holds out an arm parallel to the ground it is approx 150, depending on the build of the man if you like... it is pretty clear to me at least, that scott is easily 6'. given any slight leaning or what have you together with the head of the hammer being below the hand. I think the fall is at least 140cm then.

The timimg? Like I said you know when the hammer has hit, when it lurches. I've clocked it, I don't agree with any of your times, we'll have to agree to disagree. I said at most 1.1sec because thats what I found it to be.

As for the 2X and 2.4X speed of the film, you guys don't even seem to agree with each other,

"Further, we have many examples of ballistic motion in combination with astronaut motion which means that the film speed cannot have been adjusted selectively. Further, as any physicist can tell you, simply adjusting the time scale does not compensate for differences in gravitational effects on ballistic trajectories."

"It does in this case because a 2X speedup is very close to the 2.4X speedup that would render vertical accelerations in lunar gravity theoretically equal to vertical accelerations in earth gravity"

Anyway, I think I'll call it a day with you guys. I am not a conspiracy theorist, this is my first! But you guys seem kinda closed minded to me.... but then you are americans..

I'm not American. I haven't seen anything written on this page to indicate that the people here are closed minded. Why would you say a thing like that?

"I've clocked it, I don't agree with any of your times, we'll have to agree to disagree."

Youve CLOCKED it, Ive actually gone into the movie with a video editing tool and checked up the frame numbers. But fine, if you want to go with your stop watch, go ahead. Im just curious as to how your clocking can be more accurate than a video editing tool.


"But you guys seem kinda closed minded to me"

Well, you're the one who refuses to actually download a video editing tool to check up the start and end frames.

"but then you are americans"

Im not american. It doesnt really make a difference, does it? Im think you're the one who's close minded, with that sort of prejudice.

As far as I know, Jay is the only American in this particular debate, aside from the BA himself, who seems strangely quiet at the moment. Is he eagle I wonder? Hmmm (strokes chin).

...but they are 'pretty' straight, as someone said there is a SLIGHT angle.

... as seen from a meter off the ground.

Armstrongs height, I got it from a page that does not appear available right now, a searth gave me this

I apologize: you are correct, Armstrong is 5'11". I was quoting from memory earlier. I'm now where I can access my extensive print library and I've verified both Armstrong's and Scott's heights.

Dave Scott's NASA biography lists his height at 6 feet, the maximum allowed for an astronaut in Gemini-Apollo.

He may be leading forwards, but only slightly

How far would you say? How would you arrive at that estimate?

just as his arms are only sligtly below the shoulder height.

Again, as seen from the LRV camera only a meter off the surface. If something appears to be drooping when seen from a low angle, then it's really drooping.

If a 6' man holds out an arm parallel to the ground it is approx 150

How did you arrive at this number?

How do you plan to deal with the fact that a man wearing a pressurized J-mission type space suit cannot lift his arms parallel to the ground?

I think the fall is at least 140cm then.

How did you arrive at this number?

I've clocked it

Using what equipment and procedure? Johnno's method will ensure a very accurate measurement with a precision of 1/30 second. More importantly, he has explained his procedure in enough detail that I can get an idea of how accurate it would be. Despite repeated requests, you have not described how you are timing the drop, so I have no way of knowing how accurate or reliable your measurement is.

I don't agree with any of your times

I know that, but you haven't given us any rea