Ask a physicist anything. (8)

[Subduction Zone]

All your little test showed was that I have no knowledge of things never once observed in the universe. In other words useless theoretical science.

LOL, gravity have not been observed? Electric fields have not been observed?

I have seen this problem done with a charged nonconducting sphere. It works just as well with one of those and it is conceivable to make such a sphere.

You lost. You can't do a relatively simple problem. Your judgement of even more difficult physics is worthless.

You still have not explained how knowing the gravity of a hollow sphere inside a solid sphere and non-concentric to that solid sphere is going to be any use to anyone in the real world?

Its application was to show that you cannot do the math of physics or electromagnetism. It worked like a charm.

I no more concern myself with nonsense math than I do with nonsense religious ideas.

Except my math was not nonsense math. It was the same math that allowed us to go to the Moon and back. How is that nonsense?

It seems like you are only making excuses for your failure.

[quoteI know you do not expect me to believe that any planet or star has a hollow sphere non-concentric to its body inside it? Or even a hollow sphere at it's core. So I should concern myself with this useless math for what reason?[/quote]

I guess I have to explain again, it was a test of your understanding of physics. You failed. Terribly. Do you need me to quote some of the lines that show how you failed? It also shows why you made terribly wrong statements about the gas around our galaxy. You do not understand either gravity or electromagnetism.

Of course those that believe in Fairie Dust Dark Matter and stuff might think it is useful, since they deal in fantasies anyway. But sorry, we live in the real world, not make-believe. Good strawman though.

But I have already shown that it is you who believes in "Fairie Dust". Since you cannot do the math you are in no position to judge the physicists who can do the math. That makes your beliefs without basis. Since you have no basis for your beliefs you are the one who relies on magic. Not the real physicists.

So one more time my challenge: Find me an actual science article that supports your belief. That means an article where the experts have vetted it. An article published in a peer reviewed journal of the applicable sciences.

Is that such a ridiculous request?

 

[Subduction Zone]

Just for fun I found the same problem listed as a problem in electric fields. You are also told how to get the answer but not what the answer is. In other words this was as far as Michael could get with my test queston:

Electric Field inside a hollow ball, excentred of a homogeneous charged ball - Physics Stack Exchange

 

[Cactus Jack]

Where do the Si-te-ca come from and why can't the scientists get any DNA to test?

 

[Chesterton]

I was reading a copy of a London newspaper (Daily Mirror, I think?) from 1975 (don't ask why). In the sports-related articles, it referred to "football", but I was surprised to see that twice it also matter-of-factly referred to the game as "soccer". I always thought "soccer" was a made up American word that the rest of the world sort of smirked at. Do Englishmen use the word "soccer"?

 

[florida2]

I was reading a copy of a London newspaper (Daily Mirror, I think?) from 1975 (don't ask why). In the sports-related articles, it referred to "football", but I was surprised to see that twice it also matter-of-factly referred to the game as "soccer". I always thought "soccer" was a made up American word that the rest of the world sort of smirked at. Do Englishmen use the word "soccer"?

Well, I suppose the title of the thread is ask a physicist anything

Soccer is very rarely heard. I'd be surprised to see it in a newspaper or even in normal conversation. The only people I've ever heard use it over here are Americans

 

[Wiccan_Child]

I was reading a copy of a London newspaper (Daily Mirror, I think?) from 1975 (don't ask why). In the sports-related articles, it referred to "football", but I was surprised to see that twice it also matter-of-factly referred to the game as "soccer". I always thought "soccer" was a made up American word that the rest of the world sort of smirked at. Do Englishmen use the word "soccer"?

Sometimes. There are TV shows with the word 'soccer' in the title, for instance. It's never used in everyday speech, and I'm surprised it was in a newspaper (especially the Mirror; they're usually ferociously patriotic), but it might have slightly more use in circles where they have an international audience, and so have to differentiate between association football and American football. Or perhaps the stigma against using 'soccer' was less in 1975. Or perhaps the author was American him/herself.

In general soccer is very rarely used except, as you say, to smirk at yanks .

 

[Wiccan_Child]

Where do the Si-te-ca come from and why can't the scientists get any DNA to test?

What's 'si-te-ca'?

 

[Cactus Jack]

Sorry, mis-spelled- si-te-cah.

 

[Chesterton]

I suck at math. Since childhood, I still don't understand why two negatives make a positive. I Googled around and found a simple explanation which used human language:

1: Eat. (positive)
2. Do not eat. (negative)
3. Do not not eat. (positive)

But I still don't get it. In terms of human language it makes sense, but in terms of numbers, I don't see why a negative quantity multiplied (bearing in mind that multiplication is really just addition) by a negative quantity equals a positive quantity. Can you explain better?

 

[essentialsaltes]

But I still don't get it. In terms of human language it makes sense, but in terms of numbers, I don't see why a negative quantity multiplied (bearing in mind that multiplication is really just addition) by a negative quantity equals a positive quantity. Can you explain better?

Maybe if I mix some numbers and words together...

Can we agree that debt can be represented as a negative quantity?

Suppose a store in a town has a one-day deal where you can buy a $1000 TV with no money down.

If one person takes advantage of this offer, she has a TV, but owes $1000 to the store. We could say that her debt = -$1,000. (From the store's perspective, they stand to gain $1000 when she pays, but let's focus on the people's debt, and we'll count that as negative.)

Suppose we want to calculate the total debt in the town (due to this offer). If 22 people take advantage of this offer by noon, then the total debt in the town is the number of people times the debt per person = 22 * (-$1,000) = -$22,000

Suppose in the afternoon, another 13 people make this deal. Then the additional debt for 13 more people is 13 * -$1,000 = -$13,000, so that the total debt of the town is now -$35,000


But then, just at the last moment, 5 people come back and cancel the deal (which the store very generously agrees to do). Removing 5 people is just like adding -5 people to the total number of debtors. When we add -5 people, how much debt have we added? We use the same rule as when we added 13 people in the afternoon.

(-5) * (-$1,000) = +$5,000

And the total debt of the town is now -$30,000.

Since some people acted to eliminate their debt, we expect the magnitude of the debt to decrease, which only happens if negative * negative = positive.

Another way to consider this is to figure the whole thing out at once. We know that 22 people got TV's in the morning, another 13 in the afternoon, and then 5 of them backed out. So the total debt is

Equation #1: (22 + 13 + -5) * (-$1,000)

= (30) * (-$1,000) = -$30,000

Or if you remember the distributive law, we can break up Equation #1 another way...

Equation #1: (22 + 13 + -5) * (-$1,000)

= 22*(-$1,000) + 13*(-$1,000) + (-5)*(-$1,000)

= -$22,000 + -$13,000 + $5,000

= -$30,000

Don't know if that helped, but I took a (now long and boring) stab at it.

 

[Chesterton]

Can we agree that debt can be represented as a negative quantity?

I don't know. I came across a site which used debt as an example, but to me debt seems like an arbitrary construct of human value, and when I'm in a science forum, I want real answers.

I guess I should have said that I have a problem with negative numbers in general. If one apple exists, I can understand one (1) apple. If no apples exist, I can understand no (zero) apples. But I can't understand what's meant by a negative quantity of apples. It's like trying to discern the meaning of the word "nothing", but even worse, because you're quantifying "nothing".

But I appreciate your effort with the long post.

 

[essentialsaltes]

I guess I should have said that I have a problem with negative numbers in general. If one apple exists, I can understand one (1) apple. If no apples exist, I can understand no (zero) apples. But I can't understand what's meant by a negative quantity of apples.

Well, if you have -1 apples, then if I gave you one, you'd have none.

As flip as that sounds, it's close to the truth. At one point, people looked at equations like

x + 1 = 0

and said to themselves, "I couldn't possibly have a number of apples (x), such that if I add one to it, I'd get zero. The least number of apples I could have is zero, and if you add one to that, you get one. There's just no solution to that equation."

Later, mathematicians discovered that you could 'pretend' that there was a thing called '-1' that solved that equation. And they discovered that you could make a consistent mathematics based on these 'negative' numbers.

Similarly, at one time, people looked at equations like x^2 = -1 and said to themselves "No number solves that equation. Anything when you square it becomes positive, not negative. There just no solution to that equation."

Later, mathematicians discovered that you could 'pretend' that there was a thing called 'i' that solved that equation, and you could make a consistent mathematics based on these 'imaginary' numbers.

Mathematics is really the study of consistent rules. You can make Euclidean geometry based on these rules, and non-Euclidean geometry based on other rules. You can have consistent rules for positive integers, or positive and negative integers, or fractions, or real numbers, or imaginary numbers, or complex numbers...

Depending on the problem you're solving, one or another set of rules will help you out. If you only have to deal with whole apples, then the positive integers and zero are all you need. If you need to make an apple pie, you may want to use some fractions, or your pie will be very lumpy.

Anyway, the history of negative numbers is kind of interesting. As late as the 18th century, "it was common practice to ignore any negative results derived from equations, on the assumption that they were meaningless."

 

[Elendur]

I don't know. I came across a site which used debt as an example, but to me debt seems like an arbitrary construct of human value, and when I'm in a science forum, I want real answers.

Funnily enough, negative numbers are a subset of the real numbers

Well, jokes aside... To try to demonstrate a concept is hard, especially when it comes to mathematical concepts. It requires that one takes a step from concrete examples.

Examples:
_____________________________________________________________
If you think of a circle, you can probably envision wheels or similar things.
They're not circles.
A circle has no representation in this universe (that I know of). We have approximations, but no real circle.
_____________________________________________________________
Can you point at pi?
_____________________________________________________________
Can you show the square root of 2?
_____________________________________________________________
An interval is a 1-dimensional sphere/circle.
A circle is a 2-dimensional sphere/circle.
A sphere is a 3-dimensional sphere/circle.
How does a 4-dimensional sphere/circle look?
_____________________________________________________________

Debt is an excellent way to approximate a negative number. I think something that also could be used is a walking distance.

You're standing at 0. If you walk forward, you get a positive number, if you walk backward, you get a negative number.

It's easy to visualize the additive properties:
If you walk a longer distance backwards than forwards, you have a negative number. Example, you walk 5 steps backward and 3 steps forward:
-5 + 3 = -2
To visualize how multiplication works is harder though... I'd say that the debt example is best at that, but hey, small steps.

I guess I should have said that I have a problem with negative numbers in general. If one apple exists, I can understand one (1) apple. If no apples exist, I can understand no (zero) apples. But I can't understand what's meant by a negative quantity of apples. It's like trying to discern the meaning of the word "nothing", but even worse, because you're quantifying "nothing".

But I appreciate your effort with the long post.

I can't pass up an opportunity to advertise this awesome website:
https://www.khanacademy.org/math/cc-sixth-grade-math/cc-6th-negative-number-topic

Sometimes, to understand a concept in math, you need to work with it beforehand. Try it.

I'll return to this thread later, I'll see if I can come up with a better way to approach negative numbers. Cheers!

 

[Wiccan_Child]

I suck at math. Since childhood, I still don't understand why two negatives make a positive. I Googled around and found a simple explanation which used human language:

1: Eat. (positive)
2. Do not eat. (negative)
3. Do not not eat. (positive)

But I still don't get it. In terms of human language it makes sense, but in terms of numbers, I don't see why a negative quantity multiplied (bearing in mind that multiplication is really just addition) by a negative quantity equals a positive quantity. Can you explain better?

Because the symbol for a negative is the hyphen, -, and two of them together make the plus symbol, +

If you prefer a more technical explanation, try the following. For every real number there is an inverse under addition, and an inverse under multiplication. These inverses will exactly undo their counterpart - the additive inverse of 3 is -3 because adding 3 and then adding -3 leaves you back where you started. Likewise, the multiplicative inverse of 3 is 1/3, because multiplying by 3 and then 1/3 leaves you back where you started. In general, the inverse of N under addition is -N, and under multiplication is 1/N, and N is the inverse of both of those in turn. Finally, note that you can create the additive inverse of N by multiplying it by -1.

So where am I going with this? Well, when we multiply two numbers together, P and Q, we can 'extract' any negative they might contain. For example, if I multiply 3 by -2, I can write that as (3)x(-2), and rewrite it as (-1)x(3)x(2) - I've 'pulled out' the negative. But since 'times by minus 1' is the same as 'take the additive inverse', then multiplying by a negative can be thought of as 'multiply the two numbers as if they were positive, and then invert'. So I do 3x2=6, then invert to get -6.

Now, if I have two negative numbers, what happens? (-3)x(-2) = (-1)x(-1)x(3)x(2), as before. But this time, I'm taking the inverse twice, and inverting an inverse gets you back to where you started - the inverse of 3 is -3, and the inverse of -3 is 3, so the inverse of an inverse is the original number.

So the reason multiplying two negative numbers creates a positive is because multiplying by a negative number can be thought of as 'multiply the numbers as if they were positive, then invert'. Since we have two negative numbers, we invert twice, which leaves us right back where we started - positive.

 

[Chesterton]

Well, if you have -1 apples, then if I gave you one, you'd have none.

Funnily enough, negative numbers are a subset of the real numbers

Can you point at pi?

So the reason multiplying two negative numbers creates a positive is because multiplying by a negative number can be thought of as 'multiply the numbers as if they were positive, then invert'. Since we have two negative numbers, we invert twice, which leaves us right back where we started - positive.

"...as if they were positive..." Do you guys realize how insane you sound? Poetry is a much better way of explaining reality than math.

 

[Elendur]

"...as if they were positive..." Do you guys realize how insane you sound? Poetry is a much better way of explaining reality than math.

I don't mind sounding insane if my point got across. Did you understand what I was trying to convey?

But I would protest to your last claim, poetry and math aren't really made for reality.
Poetry is word play and math is extended logic.
No need for the reality (with the exception of language and logic of course, if you'd include those in your definition of reality).

How well they explain reality is all within the application.

Edit:
To clarify further, math and poetry are tools, and were not designed to explain reality.

 

[Cactus Jack]

Explain, in both simple and technical terms, the reaction of water and calcium carbide.

 

[paul becke]

Ask a scientist anything? That's a strange invitation! Very off-putting, indeed. You seem to be suggesting that scientists, because of their work, are funds of knowledge on all kinds of subjects - when the reverse is the case.

Their professional establishment is utterly totalitarian, clamping down ruthlessly on people who don't toe the line of know-nothing, atheist materialism. Working scientists are in the thrall of atheist scientism, scorned by most of the higher-level scientists, who however, have to keep their own council or lose their job.

All the great paradigms changes were initiated and pioneered by at the very least, deist believers in Intelligent Design. Surely, it's you who need to be the one asking questions.

 

[essentialsaltes]

Ask a scientist anything? That's a strange invitation! Very off-putting, indeed. You seem to be suggesting that scientists, because of their work, are funds of knowledge on all kinds of subjects

i dunno if the original post narrowed the scope of the question, but anyway, the answer to your question is...

Yes, be my guest.

 

[Cactus Jack]

Ask a scientist anything? That's a strange invitation! Very off-putting, indeed. You seem to be suggesting that scientists, because of their work, are funds of knowledge on all kinds of subjects - when the reverse is the case.

Their professional establishment is utterly totalitarian, clamping down ruthlessly on people who don't toe the line of know-nothing, atheist materialism. Working scientists are in the thrall of atheist scientism, scorned by most of the higher-level scientists, who however, have to keep their own council or lose their job.

All the great paradigms changes were initiated and pioneered by at the very least, deist believers in Intelligent Design. Surely, it's you who need to be the one asking questions.

Paul if you don't like this thread, why do you bother coming here?