dstebbins

...............okay, so a quark isn't really a point, it just has point-like properties, kind of like how light has particle properties even though it's actually a wave. Am I thinking right?

Well, using the find feature, I couldn't find them.

But if what you say about them being invited means that this press conference is invitation only, that could pretty much explain it. They didn't express their ideas because they simply weren't invited, in which case the explanation was a simple injustice.

Yes, do be skeptical. It's not clear why there should be strings to observe at any scale.

the idea has come upon hard times

 

 

 

you seem off in your understanding by a factor of 10^40

 

10,000,000,000,000,000,000,000,000,000,000,000,000,000

 

atomic scale is 10^-10 m

That wasn't the point. I was questioning the article's credibility.

And just because current technology doesn't allow us to study quark-like sizes shouldn't be a reason to discard it completely. In a little while, maybe in our own lifetime, technology might be able to magnify things 10^35 times. In fact, it could happen in just fifty years with the way things are going now.

And since a point has a volume measurement of 0x0x0, that can only suggest that a quark does not exist...wtf?

If you want to know why colliding branes has essentially been dropped---what other models work better---or at least seem more attractive to the KITP people, let us know. I or somebody will try to answer.

Go ahead. Tell me.

string/M theory is in trouble

 

I'd advise you to take string popularization with a grain of salt

(or even a lot of salt )

???

Well, it is supposed that these extra dimensions are wrapped up in the strings themselves. The idea is that on macroscopic and even atomic scales, things only appear to be 4 dimensional because the extra dimensions are so small that they cannot be seen. However, at Plank sizes, these extra dimensions can be observed. An analogy would be that of a strand of hair, in that from a distance it looks like a one dimensional line but close up it is 3 dimensional.

 

As far as I understand, these strings are supposed to be responsible for all of the physical laws that govern our universe, and it is theorized that particles are in reality specific resonant vibrations of these strings.

 

Here is some layman's article on the subject:

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

I checked out that wikipedia article, and I'm a little skeptical because it mentions 10^-35 m as the size for which these strings can be observed, yet I understand that atoms are around 10^-50 m, and you state that these extra dimensions are only visible below atomic levels.

I've heard a lot of string theory and it's descendant, M Theory, but what little I have heard leaves me with more questions than answers.

Where are these strings and membranes located? What is their nature? Are they made of energy or matter?

Also, I hear about eleven dimensions. I'm pretty sure I can understand this if I'm taught it, but I've heard no answers. All I hear is that there are eleven dimensions in the universe; ten spacial dimensions and one time. Where are these seven other spacial dimensions located and what's their nature? What exists in these seven extra dimensions?

I'm confused as hell. Can someone explain this to me?

Well, theoretical physicists are starting to believe that the universe began, not with a giant explosion, but came into being out of nothing by two "membranes" of currently unknown nature rippling and colliding with each other, much like a fault in the earth's crust. Our universe sprang to life, kind of like a sound, only the "sound" is matter.

Understand? Didn't think so.

Anyway, some scientists believe that these "membranes" can be harnessed to actually create a universe of our own. This universe could be made in your back yard, and over billions of years, would expand to light years in radius, but not displace so much as a cubic inch of space in the surrounding universe(s).

It's generally accepted that quarks are the smallest subatomic particles in the universe. Well, suppose you had the technology to handle a quark. Would it be possible to compress it? I don't see any reason why it shouldn't.

Ah, then allow your's truly to explain.

First off, let's get some things straight right off the bat: 1) There is no such thing as 100% accuracy, simply because no matter how many decimal places you round to, there's always more that you can round to. 2) A calculation is only as accurate as its least accurate measurement, just the same as a society is only as successful as its least fortunate members. 3) Significant digits are used to measure accuracy, and because a calculation is only as accurate as its least accurate measurement, your answer must be in the same number of significant digits as the least accurate measurement (aka the measurement with the least number of SDs.)

But that all boils down to the question: What is an SD? Well, here's a list of rules for a number to be an SD. If it meets just ONE of these rules, it's an SD.

1. All nonzero digits.

2. All final zeroes after a decimal point

3. All zeroes between other significant digits.

4. All zeroes with a nonzero to the left of them and a decimal to the right.

So let's put this to the test.

1.0 would have two SDs, since 1 is a nonzero digit and the 0 is a final zero after a decimal point. 10.0 would have three, since the one is nonzero, the second zero is final after a decimal, and the first zero is between two SDs. 10 would have only one since the zero is final, but not after a decimal. 10. (read as "ten point") would have two since rule #4 would apply. .01 would have one SD, since #4 would apply if the 1 and decimal were switched, and finally, .010 would have two, since it's the same as the last one, except there's a final zero after a decimal.

Any questions?

I see. One more thing.

The first answer is 31.709 m /sec.

Second answer is 257.719 km

Your're wrong, not because you came up with the wrong number, but because you didn't express your answer to the proper number of significant digits.

To UKify this a general physics degree with a quantum emphasys. And professor at university, should probably be a research post at a university, which will be mostly research probably with some teaching depending on where you work, and your exact position. Here the top ranks do some teaching, the middle do most of it, and the bottom do mostly labs teaching.

Well, judging by the fact that he used the term "high school," I assume he's in the United States.

Well, keep in mind he said he wanted a CAREER, and I'm exactly like him. I want to research things and try to figure out unexplained phenomina, so I believe I'm in a good position to answer this question.

I'm majoring in physics later this year. My emphasis is on theoretical physics. For you, your emphasis should be quantum mechanics, which is the study of subatomic particles. Then, when you get your Ph.D (this is important. A bachelor's, or even a Master's, just won't do. The job market in science is too competitive to settle for anything less that the very best education), you need to get a job as a professor at a University. That's what most of these "scientists" do for their full-time living. Very rarely will you find a scientist who earsn his entire living from research. Most of them have a day job outside the lab, and for most people, that day job is a college science professor.

Hope this helps.

^^^And how would you solve for t in that equation? I'm lost as hell.

as said, the way i read it; the sun does lose mass in a few ways, but the energy emitted or that which we recieve are said to have no mass, at least as understood. in my mind energy has an unknown mass value, however this is argued intensly and well beyond my knowledge.

 

the thread however deals with mass and the total destructioin of matter. if energy does carry or destroy mass entirely, then you would be suggesting that w/o a source, matter will in time disappear. with the trillion upon trillions of solar units, then the universal matter will be gone at some point. another point indirectly could be mass in some amount is being transfered. interesting but, just not the way i read it....

Yes, if all the matter in the universe were in stars, then it would eventually change into energy, leaving the universe matterless.

And btw, there is another way to destroy matter without even turning it into energy. What I'm talking about is crossing its path with antimatter. A negatron (a particle with the mass of a proton but with a negative charge) and a positron (mass of an electron with a positive charge) together make an atom of antihydrogen. If you cross hydrogen with antihydrogen, the matter and antimatter cancel out, leaving you with nothing. It's very difficult to observe this, since antimatter is in such small quantities, but theoretical physics suggests that it is possible.

Thank you to everyone who posted help!! Thanks for taking the time!

no problem. It's what this board is here for.

Besides, it makes me feel smart when I can help people out on their homework.

You can also create mass from other forms of energy. [math]E=mc^2[/math] (actually [math]E^2 = p^2c^2 + m^2c^4[/math])

which just furthers my confusion. If we can make mass from energy and energy from mass, shouldn't they have some kind of connection in the form department? At least a distant one?

our sun, where the largest such conversion can be observed, emits large quantities of energy, loses no mass from this process and the changed matter is absorbed by the cooler crust or thrown out into space as dust or matter. like wise the earths largest supplier of energy, this sun, adds no new mass and all effects of this energy are in the a process to change some elements already on earth.

actually, the Sun DOES loose mass, in a process called nuclear fusion. In fact, a small amount of mass creates large quantities of energy when destroyed, according to Einstein's e=mc^2, where e is energy produced, m is mass, and c is the constant speed of light in a vacuum. The units, which are kg*(m/s)^2, simplifies into kgm^2/s^2, or Joules. That means that a single mole of hydrogen, when fused together, creates 9.00 x 10^13 J, which is enough energy to power all of New York City for a year.

True, that only a small amount of hydrogen is destroyed in the Sun relevant to what is staying, but it does happen.

Hi,

 

I wonder if someone could help me with two motion problems.

 

The first one is:

 

A car can accelerate at 1.9m.s-2. It is initially travelling at 19m.s-1 when it passes through an intersection and it then accelerates for the next 85m. What is the final velocity of the car?

Well, start by using the distance formula, which is d=(at^2)/2. Once you find the time it takes to travel these 85m at a constant acceleration of 1.9m/s/s, then use the acceleration equation, which is a=(v2-v1)/t, and solve for v2.

And the second one is:

 

A car is travelling at 95km/h for 130km, and then slows down to 65km/h. It takes 3 hrs and 20 mins. How far has the car travelled?

 

If someone can help, I would be very grateful!!

 

God bless.

Follow these steps.

1. Convert all those measurements to base units. Convert kilometers to meters and hours and minutes to seconds. It's not mandatory, but it makes it easier (a LOT easier, actually).

2. Find out how long it took the car to travel the first 130km. Subtract that time from 3hrs 20mins. That's how long it takes to travel the remainder.

3. after that, use the velocity formula, which is d=vt.

So let me try and get this straight: The kilograms noted in the unit of energy is talking about the mass that the energy has the potential to act upon; THAT'S why it's in the unit. Is that it?

Okay, can everyone PLEASE slow down?! How can you expect me to read four posts at one time and still be able to comprehend these things as if it were just a single lesson? There's a REASON a college physics class is spread out over an entire semester, you know.

Now, let's start over, and PLEASE speak in laymen's terms: What am I doing wrong in this logic?

Things like light, sound, and electromagnetic radiation are considered pure energy, meaning they have no mass. Well, the unit of energy, the Joule, is expressed in base units as kg*m^2/s^2. Well, kilograms is a unit of mass, right? So by that logic, since there is mass in the unit, shouldn't there be mass in the energy? According to the laws of mathematics, you can't have a unit of something without it being present. If energy has zero mass, then any number times zero is zero, so an object with no mass, such as light, should thus have no energy, yet it does.

I've never been right on this site before, so the chances that I'm right this time are slim, so where am I going wrong?

The conversion of Hydrogen to Helium changes the mass by less than a percent, and the sun won't get past converting to Carbon (with similar scale reduction in mass). After that it just isn't hot enough (which is dependent on the mass) to continue fusing, and the fusion only involves the material in the core of the star. That's why the sun has a predicted lifetime of about 10 billion years, with ~half yet to go.

But shouldn't the mass of the sun be decreasing due to e-mc^2? According to that theory, the energy you get e from mass m is qual to the product of the mass and the square of the speed of light in a vacuum, meaning that a single kilogram of anything fused together creates 9.00 x 10^16 J of energy. Shouldn't you be considering that in your explaination?

On a side note, that brings up another problem. I'll make another thread about it to keep this thread's clutter down.

because the sun will never convert all of its mass to energy. it blows up well before then.

 

oh and swansont, i get where you were coming from there. i had a bit of a brain fart there.

oh, such as when a star turns into a black hole by imploding?