pmb

I think that this place would be a much better place if we all respected eveyone else and were as humble as we could be, no matter how smart or how knowledgable we think we are.. There comes A time where someone will be certain of something and we may believe that they are so wrong that the truth its smacking them upside the head. They just might believe that they are right so much that it hurts. Even thought it may be something as simple as "the momentum of a free partical of proper mass m is p = mv/srqt(1 - v^2/c^2)" and they might tell us we're wrong. Well so what? We don't have to convince anybody that we're right. All we have to do is our best.

In the past I used to keep talking until I could get them to acknowledge what is clearly found straight out of a text. I don't know why I felt I had to do that. t I don't work like that anymore.

I think we should be polite and patient and as helpful as we can and not be so stubborn as to think we need to get people to agree with us.

What do you folks think about that?

Best wishes,

Pete

I don't understand. What were the first five items in the list you quoted?

They were about the other things in the thread he got right. He was posting them to say something like "See? I got all these other things right so leave me alone."

I'll PM the URL to you so that you can see the actual conversation so that you can see the context.

I saw that Caps has made ''introductions to calculus'' which I thought was a reasonable introduction but could have been expanded. I feel perhaps these things could be good for people who come here directly asking questions about specific topics and could be redirected to these introductions.

 

Has anyone thought of doing this for physics? If no one has, I'd be willing to write up a few posts and let it be continued by people who have more time.

The purpose of my website was for just that reason. I'd be more than happy to give it to anyone who wants it. http://home.comcast.net/~peter.m.brown/- My hope was that people would find it useful. My dream is to get feed back so I can make it better

You think I should be banned? I will call you on this. After I'm done with this post, I will try to report my own post for banning (which I don't think I can do), or failing that, I will "report" your post with the intent of interesting a moderator in your claim that I should be banned. If I'm guilty as charged, then I'll be banned.

That seems quite silly to me. Nobody could be banned over something so trivial. In fact you shouldn't even bother the moderators with something so silly.

Of course *&( is using ad Hominems.

Aethelwulf - Up until this point no names have been used. I didn't want this to be an attack on a person who isn't here to defend themsleves. That would be bringing a fight from that forum to this forum and that's the furthest thing fro my mind. CAn you do me a favor? Please edit your post and delete that name. Thank you.

Yes. And in each example, there is no other argument provided. Your definition says Whenever we attack a person instead of his or her argument. Your example shows someone attacking you in addition to your argument.

The opponent never addresssed the arguement. Even if he did part of his response was still an ad hominem.

Time to agree to disagree swansont!

It is a personal attack. But it is not the ad hominem fallacy, because the attack was not as a substitute for a response. It was a personal observation in addition to a response. Uncalled for, IMO, because it's likely to only incite and inflame, but still not ad hominem.

I still disagree. The terms personal attack and ad hominem are synonyms. Don't you recall how the text defines these terms? It states

Whenever we attack a person instead of his or her argument, we commit a form of the fallacy known as the personal attack. Historically, this fallacy has been known a argumentum ad hominem, or ad homenim for short.

(Italics are mine) There is nothing in the definition that says that the attack has to be a substitute for the response.

Let's take a look at some examples of ad hominems from Wiki

http://en.wikipedia.org/wiki/Ad_hominem

"Candidate Jane's proposal about zoning is ridiculous. She was caught cheating on her taxes in 2003."

"What makes you so smart and all-knowing to deny God's existence? You haven't even finished school."

See how the attack has absolutely nothing to do with the topic?

@pmb

 

You do know that you're not being helpful, right? You're just telling me I'm wrong. Great, thanks for that.

Dear Gobbleston,

I appologize for not being helpful. It wasn't like I was intentionally paying you short shrift or anything like that. I've been very ill this week and the energy has been saapped from my body. That's why my responses haven't been as good as could have. I've just been too week to give it my best. Please cut me a little slack, okay? Thanks.

I'll try to do better. Let me start from scratch.

I originally had a fairly basic question about the twin paradox but when attempting to look it up, I clicked the Wikipedia article and it was totally chock full of equations relative to speed, and the Doppler effect, and other such things.

 

I was led to believe that the twin paradox has to do more so with the two twins and their relation to one another based on the bending of space time because of their acceleration/mass.

The Twin Paradox is defined as follows. Note: What follows occurse in flat spacetime. Two twins are initially at rest at home, i.e. at the spatial location R = (x, y, z). One twin speeds off and later comes back home only to finds that he's aged less than his twin who remained at home. This is a result of time dilation, i.e. time in his moving frame of reference runs more slowly than time as measured at home. That's the Twin Paradox. Spacetime does not curve during all of this. Once spacetime is flat its flat unless you place matter in the space. In the Twin Paradox the mass of the twins is so small as to be neglected for this purpose. Mass is not a factor in all of this.

Einsteins theory of general relativity basically means (as far as I know) that the faster an object moves, the greater its mass increases, and because objects of larger mass create a greater gravitational pull on space time, that would account for the differences in age. Is that wrong?

Yes. It's wrong. The difference in aging of the twins is accounted for by regular time dilation as accounted for in special relativity, not gravitational time dilation as accounted for in general relativity. While its true that each twin has mass that isn't accounted for when we calculate the difference in aging. As a matter of fact we can make the mass of the twin as small as we wish. The twins could simply be a small amount of radioactive material whose mass is so small that it can be neglected and the material being radioactive can act like a clock.

Does that help?

Question - How were you led to believe that the twin paradox has to do more so with the two twins and their relation to one another based on the bending of space time because of their acceleration/mass?

No sense of humor dude? I apologize if my attempt at humor was obtuse... oh and no the - rep didn't cause my panties to get into a knot...

Okay. I get it now.

I had it confused with something else, i.e. at first I thought it was the rude comment "suck it up". Thanks for clearing that up for me.

Unfortunately this forum doesn't have any suitable smileys to represent rolling about laughing' date=' but consider one posted anyway.

[/quote']

Sure it does. Right about the edit window ther is a smiley face. Click that and to the right a panel will appear which has a whole bunch of smiyley faces. Click Show All at the bottom of that panel and you get an even larger selection.

"You're stupid" is not an ad hominem argument. "You're stupid, so your argument is obviously wrong" is clearly an ad hominem, because it uses insult rather than logic to attack an argument.

 

Your textbook may provide examples that make this distinction clear.

I'm already clear on it. I've never confused an insult as being an ad hominem attack. And my text doesn't have an examples like that. However it does have something relavent to say under the section about circumstantial personal attack which pertains to the ad hominem I cited

Further, an individuals motives for asserting an arguement are always logically irrelevant to the arguments cogency.

since in the case I cited it was my motives where were raised.

suck up...

I don't understand this response. What is it supposed to mean?

Now rework the problem with a payload of mass M, and a sail of mass m, where M >> m.

 

I mean, there's no point of discussing a practical propulsion system with no payload.

Yep. I know. What I had in mind was to look at the upper bound of the acceleration and if the upper bound was insufficient then a real sail wouldn't work. The upper bound of acceleration is with no pay load. With the payload you want the sail to be as large as it can.

I'm not a fan of trying to guess what others' motives are and agree that they have no place in a discussion, but I don't see an ad hom fallacy.

From what the logic text tells me an ad hominem is when a person attacks the arguer instead of the arguement. In this case he didn't attempt to address the arguement (I explained that E = mc^ = mv^2 is wrong when the partilce whose speed is v has non-zero rest mass) but instead called my character into question. You disagree with this. right? Which part?

Here is what the text states

Whenever we attack a person instead of his or her argument, we commit a form of the fallacy known as the personal attack. Historically, this fallacy has been known a argumentum ad hominem, or ad homenim for short.

Of course this depends on how

ever since you re-joined this forum you have seemed eager to prove me wrong every time I opened my mouth . If I were a paranoid (I am not) I would say it's something of a mission of yours.

is percieved. I percieve it as a personal attack since I was never eager to prove him wrong. By claiming that I have some sort of hidden motive he's questioning my character.

Except gravitationally, of course .

There is a small interaction between photons. In some cases photons will bounce off each other.

What is going on here? I posted things here and they never appeared when I came back. If the moderators deleted them then please send me a PM to let me know why so I can avoid posting things which might get deleted in the future.

The following might appear as if I'm whining here. I'm human so I'd have to admit that there is some of that in it. But I'm posting it to show how complaints against ad hominems are met in other forums and how we should consider ourselves lucky here and how much we should appreciate the moderators here.

In response to that ad hominem I posted the following

Note: Your resonses are ad hominems. I'd like to request that you cease using them since ad hominems don't belong in a science discussion forum.

The following is the moderators response

OK, pmb, enough is enough - what *** does is not an ad hominem, and if you applied your wiki definition you should know that. An ad hominem is when someone reject your arguments because of who you are and not because of the validity of the argument. Just disagreeing is quite normal for a forum and does not amount to an ad hominem.

 

In short, cut the cr*p.

Another moderator responded with

i just thought that pmb was far too thin-skinned and should stop thinking that any disagreement is an attack on him as a person

 

besides, it's clear from Guitarist's tone that he doesn't mean any offence + anyone who under those circumstances insists on such an apology is clearly taking offence where none was intended

At least our moderators are rational people. Enjoy this forum. The moderators are pure gold compared to the terrble excuses of forums out there. My applause to the moderators. Hip hip hurray!

But isn't acceleration directly linked to mass and mass's effect on space/time?

Not that I'm aware of, no.

So the twin's mass from their acceleration should have at least some relation there, shouldn't it?

No.

The faster you go, the more mass you accumulate, the more mass you accumulate, the more gravity you generate, the more gravity you generate, the more space/time is bent.

Yes. In the twin paradox that very small field generated by the moving twin is small enough to ignore. In any case, relative to the twin, there is no mass increase of himself or the ship he's in.

Is the way I’m understanding this just a different angle than how it is usually viewed?

Yes. But keep in mind that its the wrong way.

In light of the text of the full post, I would say, yes, that was an ad hominem attack, since he clearly listed that as one of the reasons he was refuting your post. The context makes the difference.

 

Edit - grammar.

Thank you or your opinion. It was greatly appreciated.

.. (unless there was more to the message than you quoted here). ...

Yes. There was more. I didn't think it was neccesary to post more than that. Let me post the entire response

Then my friend we are seriously at cross-purpose.

 

1. I wanted to shoow why the "standard substituion" in QM [tex]\hat{p} \to -i \habar \partial_\mu[/tex] might be valid

 

2. The approach I took was historical - prospective in a certain sense

 

3. The fact that a retrospective view - what you call "modern physics" - now disagrees with historical assumptions, in no way diminishes the debt that "modern physics" owes to the founding fathers of QM. Recall that Bohr thought that electrons orbited the nucleaus and it can scarecly be denied that QM is what it is today largely thanks to him

 

4. I was able to use what you call de Broglie's "wrong assumptions" to sow why the "standard QM substitution" [tex]\hat{p} \to -i \hbar \partial_\mu[/tex] makes sense was in the spirit of (3) above

 

5. Can you give an argument, using no unnecessary assumptions, and not de Broglie's, that is as nice as mine?

 

6. Last, and by ALL MEANS least - ever since you re-joined this forum you have seemed eager to prove me wrong every time I opened my mouth . If I were a paranoid (I am not) I would say it's something of a mission of yours.

 

Have a nice day

Quite clearly the opponent attacked the arguer and not the arguement. That's the essense of an ad hominem attack in my opinion. I'd say that at this point we can agree to disagree. In this case he used the "He's out to get me." excuse.

Would you also advocate going back to the meanings of several hundred years ago for a great many words in the English language, some of which have greatly altered or even reversed at least in the last 25 years?

That would be contrary to his purpose, i.e."a meaning which has been agreed and understood for many centuries". The one you refer to doesn't fall under that criteria.

I hope I didn't give the impression that I was using puffery when I used the term "ad hominem". I wasn't. As imatfaal said, it represents a complicated idea using just two words. I like it because I can use it and leave out the word "attack" so as not to rile the natives.

I was led to believe that the twin paradox has to do more so with the two twins and their relation to one another based on the bending of space time because of their acceleration/mass.

The twin paradox is about two identical twins, one who stays on Earth while the other one accelerates off to a distant place. Comes to a stop and then returns. The one that remained behind will have aged more than the twin that went away and came back. It has nothing to do with the bending of space time or their mass. It has only to do with on of the twins acceleration.

Einstein’s theory of general relativity basically means (as far as I know) that the faster an object moves, the greater its mass increases, ...

You can look at it that way, yes.

and because objects of larger mass create a greater gravitational pull on space time, that would account for the differences in age. Is that wrong?

The faster the body the greater the mass. The greater the mass the greater the gravitational pull. There are two factors at play here. One is the increase in mass of the moving body. The second is the increase in gravitational force as a function of speed.

The rest is not not quite right. It is true that time passes slowed for those near gravitating body than those far away though.

PMB, I don't always agree with you but in this case I do.

 

Stick to plain English then you won't have a problem with those who like to feel superior by hiding their true meaning in another (dead) language.

 

As such Ad Hominem means what I (or you or Uncle Tom Cobbly) want it to mean, within the translation. It literally translates as towards the man.

 

Some might adopt a particular meaning convention, but if the greater majority from the great unwashed understand something different who is to say who is right and who is wrong?

In cases like this I prefer to use textbooks as the source of definitions. The one I have now is Practical Logic: An Antidote for Uncritical Thinking - 5th Ed. by Soccios and Barry, Harcourt Brace College Publishers, (1998). It's a wonderful text. The description is five pages long so I can't post it.

Why?

If you increase the area of the sail by a factor R then the mass will increase by the same factor. This means that the acceleration remains unaffected.

Think of placing a solar panel of area 1 cm^2 in space with its surface normal being parallel to the light hitting it. The panel will have a force F exerted on it and will accelerate at the rate g. Now place another identical solar panel right next to it. They willl accelerate at the same rate. That won't change if they're fused together to make one solar panel but now you have a solar panel twice the area of the original sail.

To me it doesn't feel like an ad hominem, since they really didn't argue any particular point. It feels more like an expression of frustration to me.

Thank you very much for your opinion.

As I understand it, an ad hominem is simply an attack on character of the person whom they disagree with. When the attack switches from the subject matter to the character of the arguer its called an ad hominem. An ad hominem doesn't argue a point.

I'd like a second opinion on something I was faced with elsewhere. It's not my intentioin to bring a discussion from another forum here, but to get an unbiased opinion about something that happened elsewhere.

A while back I presented an arguement whereby I proved another member's assumption to be wrong. After I posted the correction to the error I got the following reply, in part

--------------------

ever since you re-joined this forum you have seemed eager to prove me wrong every time I opened my mouth .

--------------------

Would you say that this is an ad hominem?

I looked up the term ad hominem in Webster's Online Dictionary at

From Webster

http://www.merriam-w...ry/ad%20hominem

------------------------

1 : appealing to feelings or prejudices rather than intellect

2 : marked by or being an attack on an opponent's character rather than by an answer to the contentions made

------------------------

I also looked this up in a book on logic that I have and it says that an ad hominem is defined, simply, as when the arguer is attacked rather than the arguement itself.

What do hyou do when you get an ad hominem reply? Do you ignore it? PM the person and ask them not to do it again or respond in the thread asking them not to use ad hominems?

Thank you for your opinion.

Next question - Is it inappropriate for me to ask a question likke this in this forum? I couldn't do it in the original forum because I'd be unable to get an unbiased opinion. I believe I can get an unbiase opinion here.

Solar sails use a phenomenon that has a proven, measured effect on spacecraft. Solar pressure affects all spacecraft, whether in interplanetary space or in orbit around a planet or small body. A typical spacecraft going to Mars, for example, will be displaced by more than 1,000 km by solar pressure, so the effects must be accounted for in trajectory planning, which has been done since the time of the earliest interplanetary spacecraft of the 1960s. Solar pressure also affects the attitude of a craft, a factor that must be included in spacecraft design.

http://en.wikipedia.org/wiki/Solar_sail

I never quite grasped the solar sail thing. The acceleration is so small that it would take forever to get even to Mars. The amount of acceleration is independant of the area of the sail so 1 cm² will accelerate at the same rate as a sale of area 10²⁰ cm². The size of the sail is only to allow for the acceleration of a ship. The larger the sail the greater the force it can exert. But the acceration won't increase past the acceleration of a no load 1 cm² sail.