Was Galileo wrong?

[pizzaguy]

<font color="yellow">There are lots of myths about Aristotle, his supposed opposition to <i><b>experiment and observation for example.</b></i> Within the limits of the day he in fact was a strong and good observer and his description of anatomy required dissection of the organisms in question and comments on vipariousness in sharks and air breathing among whales could only have been through direct observation. </font><br /><br />Is that really true? He got so many things WRONG! Didn't he say something like this:<br /><br />"Every object in existance has it's own unique characteristics, and will behave the same in every medium."<br /><br />Which is a big WRONG-O! I throw a stick out into the lake, and it falls thru air, but not thru another medium: water. <div class="Discussion_UserSignature"> <font size="1"><em>Note to Dr. Henry:  The testosterone shots are working!</em></font> </div>

 

[kateexelby]

Roger is right. Galileo was wrong. <br /><br />Schools do indeed teach wrong in this case and of course it's wrong when that happens.<br /><br />There are 2 pages of the science book that completely conflict and disprove each other:<br /><br />1.) Galileo says that 2 falling objects will hit the ground at the same time, regardless of their mass (and therefore weight, since weight is mass relative to a set gravitational pull - and we're talking gravity here). <br /><br />2.) The other is the concept of Terminal Velocity. It states that an object will continue to ACCELERATE as it falls, until it reaches its terminal velocity. After that it will complete its fall at the final speed it reached. What it means is, that drag increases the faster something falls. There comes a point of accelerating when the speed it’s falling is equal to the drag upon it. Thereafter it’s stuck falling at that speed. And this speed will vary, depending on its weight.<br /><br />So, if a brick weighed 1 kg, then earth is inflicting a 1 kg pull on it. The brick is dropped, and accelerates for every metre that it falls, getting faster and faster until... <br /><br />...it is being "pulled down" at it full potential of 1kg. After that it will continue to fall at its final speed. Let's imagine it took the 1 kg brick 10 metres before it hit terminal velocity - Let's pretend that that was 10 miles per hour. Now remember that after 10 metres it stops accelerating and its falling speed is 10m/hour when it hits the ground.<br /><br />Now we drop a 3 kg brick. This one has 3 kg pull on it - this will continue to accelerate past the 1 kg pull point - past the 2 kg point until earth is pulling it for the full 3 kg it weighs. <br /><br />So not after 10 metres of falling but after 30 metres it'll stop accelerating and fall at a constant speed. Let's say that was 30miles/hour when it hit the ground. = faster than the 1 kg brick.<br /><br />---------<br /><br />The 1 kg brick stopped speeding up way earlier than the 3 kg

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>2.) The other is the concept of Terminal Velocity. It states that an object will continue to ACCELERATE as it falls, until it reaches its terminal velocity. After that it will complete its fall at the final speed it reached. What it means is, that drag increases the faster something falls. There comes a point of accelerating when the speed it’s falling is equal to the drag upon it. Thereafter it’s stuck falling at that speed. And this speed will vary, depending on its weight. <p><hr /></p></p></blockquote><br /><br />Actually, terminal velocity is not merely dependent on weight. It's also dependent on density and shape, and potentially also the orientation of the object and whether or not it can hold itself steady. (Aerodynamics, basically. A ten meter wide cubical box weighing ten kilos will have a lower terminal velocity than a bullet-shaped chunk of uranium weighing ten kilos.)<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>Great, but Galileo didn’t mention ANY vacuum in relation to falling canon balls, unless the Italians erected some enormous dome over Pisa that I never knew about... It seems to me his was genuinely mistaken.<p><hr /></p></p></blockquote><br /><br />No, he didn't mention vacuum. But he was describing identically sized and shaped object. Unless they are wildly divergent in density, it's not going to make any difference which one is heavier, and that was his big breakthrough.<br /><br />You are correct that the object being dropped exerts a gravitational force on the Earth, and so if the object is heavier, there will be more gravitational force. However, the difference in mass has to be enormous before this becomes significant. And I do mean enormous. A thousand-ton object will not accelerate significantly faster than a one-gram object. This has important implications for celestial mechanics; you can tell the mass of an object by how rapidly any satellites orbit it -- and generally, thi <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[kateexelby]

CalliArcale, <br /><br />What, different shapes make a difference too - nah never!! <br /><br />I'm sorry if it's confusing for you! ) <br />I therefore simplify:<br /><br />Galileo was wrong insofar as two same size balls weighing different amounts fall at *different* speeds – AND land at DIFFENT times. YES REALLY! <br /><br />It may not be *a lot*, but it’s really, truly, scientifically different. As proven by Terminal Velocity. <br /><br />See my previous link to the NASA page if you chose not to believe me. Please make sure you understand that heavier items land before lighter items due to Terminal velocity before replying. It’s nothing new. It’s just so many people miss this paradox. You’ll see NASA state that “lighter objects fall slower”, in conflict with Galileo’s teachings.<br /><br />Are you saying “roughly the same time” is the same as “exactly the same time”?! I don’t accept that. Because that seems to be what we disagree about. If so, let’s agree to disagree. <br /><br />I accept that without accurate measuring kit and only the tower of Pisa to chuck stuff down from, his findings were extremely interesting. However, ultimately, he drew somewhat wrong conclusion from a imperfectly controlled experiment. It wouldn’t have made a difference if he was right, but since things don’t ACTUALLY hit the ground at the EXACT same time, it can’t be allowed to be taught as 100% true. <br /><br />Look at all you lot, you all believe it – because you were taught it at school! LOL <br /><br /><br />Here’s a more *accurate* way to tell kiddies about it: (I’m thinking of 5 y.o.’s – since I’m a teacher.)<br /><br />A long, long time ago people used to think that heavy objects would drop to the ground quicker than light ones, but one day a man called Galileo scrambled up a very tall tower to save a princess from a dragon. The dragon saw him and was about to attack him but Galileo was very clever and he knew a secret no one else knew. He tricked the dragon. He asked the dragon which ball wou

 

[CalliArcale]

You missed my point, and followed it up with some rather condescending "explanations" couched in a writing style that leaves me rather concerned that you're teaching kids, while arguing that I don't understand that gravitational attraction is the sum of the forces between two objects. I do understand that, and I made that perfectly clear in my last post.<br /><br />You seem determined to say that Galileo was wrong. I say it's more precise to say he was inaccurate. You follow it up by condescendingly saying I don't understand physics and merely swallow whatever I am told. It appears you are more interested in denigrating somebody who in fact made a very singificant stride forwards in science than you are in presenting anything truthful.<br /><br />Galileo's point was that heavy objects don't fall significantly faster than light ones. People thought they did. But they don't. The difference is negligible. That really was a critical breakthrough, which you seem to want to discard purely out of spite.<br /><br />If you don't think this should be taught in schools, you'd better go after everything else that is only accurately predictive at certain scales, such as Newton's laws of motion.<br /><br />Incidentally, if you want to be really nitpicky, you might want to avoid repeating the common myth that he dropped balls off the top of the belltower in Pisa. He didn't. The experiment was actually conducted using inclined rails. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[Swampcat]

Since I only had one year of college physics I'm not knowledgeable enough to argue the finer points of Galileo's work. I accept that he made enough of a contribution to our understanding of gravity (among other things) to warrant his place in history and his conclusions were revolutionary and profound.<br /><br />I just have one point to make about your post.<br /><br />Making up stories about dragons and princesses and presenting them to impressionable children as the way Galileo went about his discoveries is just plain wrongheaded IMO. It's certainly not "a more *accurate* way to tell kiddies about it..."<br /><br />To the extent that a 5 yo wishes to know anything about Galileo it would far better to simply tell them that Galileo was the first scientist to determine, as Calliarcale said, "that heavy objects don't fall significantly faster than light ones." If they ask why then you can add more of an explanation, but making up a story around a story that is arguably false is not the best way to go about teaching children.<br /><br />For a reference, check out this webpage. <br /><br />Oh, and btw, welcome to SDC <img src="/images/icons/smile.gif" />.<br /> <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[bad_drawing]

For Goodness sake, just tell the kids that objects of different size and weight fall at virtually the same rate towards the earth. You're concerned about telling the truth in school, yet you teach them of Gallileo in some strange Princess tale? If you're teaching kids young enough to have to use stories like that, then i think the ultraminute descrepancies in the rate of attraction are irrelevant. As the kids get older and more curious, the can be taught of the other details. You know...kindof like when we were all kids and they taught us that you can't subtract a bigger number from a smaller number. Then when our brains got a little more advanced a few grades later, they brought us up to speed. Anyways, thats just my two cents.

 

[drwayne]

I realize that this is a bit of a tangent, but when my son was little, at bed time, I would tell him some things about physics - he had no idea what I was saying, but I was talking to him, so he liked it.<br /><br />When he was 4 or 5, another child of similar age was over playing with him in the back yard. My wife was listening and hear the other child ask - "Why is the sky blue?" - she said our son immediately said, "Rayleigh scattering". The other child asked what that was. Our son said to him, in that sweet, angelic, very small voice of his - "I'll tell you when you are older".<br /><br />My wife said she nearly peed her pants.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[bad_drawing]

Thats great! Its amazing what can stick. That reminds me of when I was a little kid, my oldest brother (who was going through college to be a physicist) would help me make projects for the science fair (Do schools still do those?.. I hope so!)...so in a sea of projects like baking soda and vinegar volcanoes, i had an oscillating circuit one year and a handmade / wound alternator another. (Yeah... I'm pretty sure everyone knew I had some guidance lol) There's no way i could have done them without his help but I loved having him explain things to me. (as a tangent of a tangent... he was/is odd. He would build his own tesla coils that he and his friends would use to shock themselves with. His room always smelt of ozone and...something else (joke).) <br /><br />

 

[CalliArcale]

That is incredibly cool, drwayne. <img src="/images/icons/wink.gif" /> You trained your little nerd well!<br /><br />(My two-year old likes dinosaurs. Her favorite is coelophysis, and yes, she can pronounce it. Nerds rock!) <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[flanny]

hey all. I realize being both new and VERRY late to this thread I may not be taken in current context etc. but I felt compelled to post after reading the original post and scanning through some of the responses.<br /><br />We came across this site while I was looking up information on Galileo versus Aristotle for my daughter after one of her science books asserted that heavier objects fall faster than lighter objects, which is a contradiction to to Galileo's claim and an attempt to affirm Aristotle. <br /><br />Her science book had her drop a book and a piece of cardboard as "proof" and didn't discuss the effects of wind resistance, aerodynamics, etc. it's like dropping a feather and a rock. it's comparing apples and oranges.<br /><br />I don't think galileo was trying to say objects of different "weight" fall the same. What he was saying is that a denser object (more compact, not heavier per se) will fall faster than a less dense object. Which has shown true in all my physical experiments with my children after we read the claim in this science book.<br /><br />We took, 2 pieces of cardboard in equal density proportionatly one weight was 8 grams and one weight was 34.5 grams. 100 out of 100 drops of varying heights from 1 meter to 9 meters produced landings at the same time.<br /><br />I took a 1 kilo dense jugging ball and a 5 kilo sheet of aluminum. the jugglig ball hit first every time. I took the same juggling ball and a 4 kilo bowling ball. both hit at the same time.<br /><br />We found that hollow balls/objects tend to drop slower, regardless of weight than solid balls. The inner air must affect the aerodynamics some how. Golf balls dropped faster than smooth balls of the same weight/density. again aerodynamics. We found websites that discussed tests performed in vacuums and actually tied objects together and timed drops and landings. The end result was the same, weight did not affect the drop speed as much as the density of the material (how compact the material

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>I don't think galileo was trying to say objects of different "weight" fall the same. What he was saying is that a denser object (more compact, not heavier per se) will fall faster than a less dense object. Which has shown true in all my physical experiments with my children after we read the claim in this science book. <p><hr /></p></p></blockquote><br /><br />Actually, he was saying that objects of different mass DO fall at the same rate, if you eliminate the factor of wind resistence.<br /><br />Galileo demonstrated this by rolling spheres of the same diameter but different densities down a slope. What he found was that the denser ones took exactly the same amount of time to reach the bottom as the less dense ones. If you could duplicate his experiment, you will see that as long as you eliminate friction as much as possible, the hollow spheres will actually fall at the same rate as the solid ones.<br /><br />It's not easy to eliminate the effects of wind resistence; your experiments in particular were heavily affected by it. Really, the best way is to do your tests in a vacuum, but that's hard to arrange in a household setting. The Apollo 15 astronauts did perform an experiment to test Galileo's claim (largely for the fun of it, since it had already been tested many times). They dropped a rock hammer and a falcon feather, brought along as a sort of mascot, because their LM was named "Falcon". The two fell at exactly the same rate. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>