PDA

View Full Version : Episode 44 - Questions for the Knowledgeable



SciGeek1aB
2008-Feb-05, 04:43 PM
In the Episode Dr. Pamela Gay stated "Mass changes the faster an object travels..." How does the mass change? Does it stretch somehow like a string, grows bigger or smaller? How do we know this and what are examples of something's mass changing as speed increases? At which point or speed does the mass of an object begin to change? How would this affect human's traveling at greater speeds in our solar system?

damian1727
2008-Feb-06, 08:25 AM
as you get quicker you get heavier

the way we travel round the solar system i (slow) i dont think it would make any diff

at the speed of light your mass would as i understand it be infinite...and would need infinite energy to move.....

some one more knowledgeable may be able to give you numbers...

you also get shorter... lol

damian1727
2008-Feb-06, 08:29 AM
what i dont understand is c relative to what??

i am already traveling at c relative to some far away galaxies....?

maybe im fatter than i thought

:)

Steve Limpus
2008-Feb-06, 09:40 PM
maybe im fatter than i thought

:)

In my case, gravity is making me shorter than I deserve. :)

sk8rpinoi32
2008-Feb-13, 08:50 AM
Because everything is relative so is mass. Time becomes relative, and if time is relative as well as distance. And damian was on the ball. Because you need more energy content in order to travel, you mass must give way to provide that. (Such as light. Light is "massless" because all of it's mass is being converted into motion).

And there are ways to test this. In particle colliders, you can approxiamate the mass by an object falling. As objects approach the speed of light, they fall at a more acute angle, meaning that their mass is more. Also, you can hit particles with light and measure their movement. A heavier particle will move a little.

But again, you'd have to be traveling at 99% the speed of light to tell the difference. I believe that an electron traveling at 99.1% and another electron moving at 99.2% will have a 120% difference in weight. (I can't remember the figures)

sillybear7
2008-Feb-17, 02:32 AM
what i dont understand is c relative to what??

i am already traveling at c relative to some far away galaxies....?


We are all traveling well in excess of c relative to something, this is true. There are parts of the universe that are separated by such a large amount that the expansion is pushing them apart faster than the speed of light.

The 'universal speed limit' of C only applies locally, which you can think of as being similar to your car measuring speed relative to the road or a plane measuring speed relative to the air it passes through. You measure your speed with a light clock and hence relative to the space you are traveling through.

damian1727
2008-Feb-24, 08:39 PM
*blink*

aurora_waters
2008-Mar-14, 07:43 AM
If you are having trouble grasping relativity try reading Mr Tomkins in Wonderland by George Gamow. It is the simplest way I can think of explaining relativity and has excellent diagrams, pictures and metaphors to help along the way.

damian1727
2008-Mar-14, 08:09 AM
thanks you for the recommendation i will look it up

:)

tho to stop being coy the blink was in response to

''The 'universal speed limit' of C only applies locally, which you can think of as being similar to your car measuring speed relative to the road or a plane measuring speed relative to the air it passes through. You measure your speed with a light clock and hence relative to the space you are traveling through.

which is incorrect....

i just did not want to mention it as its hard to explain why....

c does not only apply locally..(unless by local you mean our ''bubble'' of the universe..).we do not measure our speed against a fixed background of space...as there is not one..and then i might get a bit confused

but we measure our speed relative to some other object...so its all relative lol

we are not really moving faster than c away from distant galaxys its just alot of space is being formed between us...


?

iNick
2008-Mar-19, 05:14 PM
I have attached a jpeg of what I believe is the equation (since I can't write fraction bars it would be really messy). I''m not 100% sure its correct so you might want to check yourself.

In the equation, m1 is the relativistic mass (mass while its moving), m2 is the mass at rest, v is the velocity of the object whose mass you are measuring, and c is the speed of light. The mass is given in kilograms and the velocities (of the object and light) are given in meters per second.

This equation also helps demonstrate, at least in a mathematical way, why it is impossible for an object with mass to move at the speed of light. If you closely examine the equation, you'll notice that at very slow speeds v^2 over c^2 will equal a very small number. At very high speeds v^2 over c^2 will equal a higher number, but it will never go over one (unless you were going faster than the speed of light, but to go faster than the speed of light you would have to go at the speed of light for at least a very small time while you were acceletrating).

At low speeds since v^2/c^2 is a small number, 1-(v^2/c^2) would equal a number only slightly smaller than one, like 0.999999999999967
The square root of that is even closer to one. 1/the square root of 0.999999999999967 would equal a number only slightly larger than one, and therefore when you multiply the object's mass by that number the mass doesn't change that much.

At high speeds since v^2/c^2 is a number only slightly smaller than one, 1-(v^2/c^2) would equal a very small number, like 0.000000000000067
The square root of that is slightly larger (but still a small number). 1/the square root of 0.000000000000067 would equal a very large number, and therefore when you multiply the object's mass by that number the mass increases a lot.

If you were moving at the speed of light, then v^2/c^2 would equal one (300,000,000,000/300,000,000,000). 1-1 is 0, and the square root of 0 is 0. You would then be dividing 1 by 0 which you can't do in math (you can't divide any number by 0).

As far as the relativistic effects on an object, yes the object would undergo a process called elongation. I don't know the equation for it but you can probably find it if you google it. It is similar to the mass increase in that at small speeds you only elongate slightly (so small you wouldn't even be close to seeing it with your eye or even an electron microscope), but the closer you move to the speed of light the more you would elongate. Every part of you that is moving would elongate including your eyes, so you wouldn't notice it yourself. Only people that are standing still or moving slower than you would notice.

There is a really good howstuffworks article regarding relativistic effects: http://science.howstuffworks.com/relativity.htm

Forgive me if any of the above infomation is incorrect, but I'm only 15 years old.

damian1727
2008-Mar-19, 10:40 PM
welcome to the forum nick

thats quite some 1st post !:p


:clap:


:dance:

dont things shorten under lorentz transformation?:eh:

Steve Limpus
2008-Mar-20, 04:12 AM
Wow Nick!

You look like you're gettin' the hang of this stuff. I think Damian is right, stuff get's shorter at relativistic speeds.
EDIT: appears shorter to an observer might be a bit more correct.

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

Keep at it, and stick around this forum. Check out the guys over at Q&A too - some of those guys are really smart! Damian and me - we're just a little bit smart... ;)

http://www.bautforum.com/questions-answers/

Find something you like, jump in and introduce yourself - tell 'em how old you are, I'm sure they'll be impressed.

How do you like Pamela and Fraser's podcasts?

damian1727
2008-Mar-20, 07:56 AM
microscopically....

Steve Limpus
2008-Mar-20, 08:05 AM
So I'm thinking you checked the math. :whistle:

damian1727
2008-Mar-20, 09:48 AM
rigourously .... seemed pretty sound to me....:p

Steve Limpus
2008-Mar-20, 10:45 AM
Nick,

You might like this website too:

http://www.fourmilab.ch/cship/cship.html

I checked the math. Definitely... sound. :think:

Topvax
2008-Mar-20, 02:18 PM
we are not really moving faster than c away from distant galaxys its just alot of space is being formed between us...
?

Actually, two objects far enough apart in the universe could be separating from each other at greater than the speed of light because the expansion of the universe is not subject to the speed of light limitation. However, objects can not move within the universe at greater than the speed of light. (imagine yourself on an expanding balloon. You're speed of running on the surface is only so fast, but the balloon can expand so rapidly that points on it's surface grow apart faster than your running speed. Now convert this analogy to our living dimensions!)

:dance:

damian1727
2008-Mar-20, 03:55 PM
thats what i said isnt it?

steve.. yup he knows his times tables....

Topvax
2008-Mar-20, 05:44 PM
Sorry, I read your statement ("not really moving faster than c") literally...

damian1727
2008-Mar-20, 07:43 PM
well you cant move faster than C can you? :dance::dance:

At high speeds since v^2/c^2 is a number only slightly smaller than one, 1-(v^2/c^2) would equal a very small number, like 0.000000000000067
The square root of that is slightly larger (but still a small number). 1/the square root of 0.000000000000067 would equal a very large number, and therefore when you multiply the object's mass by that number the mass increases a lot.


you get very heavy man:D

it all makes perfek sense..:wall:

Topvax
2008-Mar-20, 08:41 PM
well you cant move faster than C can you?

Yes, a photon moving at the speed of light is traveling faster than the speed of light relative to it's point of origin in our expanding universe. But this must be what you are thinking. We just have to define the circumstances accurately...

damian1727
2008-Mar-20, 10:19 PM
you cant move faster than the speed of light

nop


:naughty:


photons are not moving faster than the speed of light

space is expanding

it is different

tho god knows how?
:think:

Topvax
2008-Mar-20, 10:25 PM
What you said earlier, "we are not really moving faster than c away from distant galaxys" is just flat wrong. Well, you don't seem to understand what I'm saying so never mind.

From better writers than I (e.g., wikipedia! at http://en.wikipedia.org/wiki/Metric_expansion_of_space):

In the language of Riemannian geometry, expansion is an intrinsic effect: the universe is expanding, as measured intrinsically by distances between points, in contrast to the familiar extrinsic notion of an object expanding within an ambient space—there is no need for an ambient space to define expansion. Because it is the metric defining distance that is changing rather than objects moving in space, this expansion (and the resultant movement apart of objects) is not restricted by the speed of light upper bound that results from special relativity.

damian1727
2008-Mar-20, 11:55 PM
yes but you have only quoted half the sentence ...

we are not moving faster than c

nothing does

but alot of space is being created between us

as i understand it relativity is not violated...

damian1727
2008-Mar-20, 11:56 PM
what does metric defining distance mean?

Topvax
2008-Mar-20, 11:59 PM
Relative to a distant point, we are moving apart faster than the speed of light. Sorry.

damian1727
2008-Mar-21, 12:01 AM
i understand that

but we are not moving faster than C

so how does that work?

Topvax
2008-Mar-21, 12:18 AM
what does metric defining distance mean?

It means the function that defines the distance between two points. In the case of our universe, that function, in relation to time, is not static.

Topvax
2008-Mar-21, 12:30 AM
i understand that

but we are not moving faster than C

so how does that work?

I don't think I'm skilled enough to provide a better analogy than the balloon surface. Or Pamela's treadmill. Perhaps someone is (or presented one somewhere else in the forum)?

damian1727
2008-Mar-21, 07:00 AM
topax i understand the concept

what i am unsure of is why relativity is not violated?

as i said there is no fixed background we measure our speed against

we can only measure it relative to another object

and very distant ones are ''moving'' away faster than c

:eh:

Clegrand
2008-Mar-21, 11:49 PM
One thing that has always eluded my understanding is that isn't the universe an ever expanding sphere with us constantly moving within it. So wouldn't we see different lines of sight from our relative position each time we make an observation or take a distance measurement. What formulas have been constructed for this?

Topvax
2008-Mar-22, 12:36 AM
The universe is not a sphere - it just is an expanding existence. If it were a sphere, that would imply an edge, or boundary, and that doesn't exist, even though it has a size! It also has no center. We are on a planet that rotates, and revolves around the sun in a solar system that revolves around the center of our galaxy, etc., so we really can never quite look at the things quite the same way. The line of sight is never the same. Astronomycast.com has had a number of episodes dealing with how distance is measured, the shape of universe, and so forth.

Steve Limpus
2008-Mar-26, 10:59 AM
One thing that has always eluded my understanding is that isn't the universe an ever expanding sphere with us constantly moving within it. So wouldn't we see different lines of sight from our relative position each time we make an observation or take a distance measurement. What formulas have been constructed for this?


Hi Clegrand

Google 'Hubbles Law' and 'redshift'. There is a ton of good stuff about this. It was just the kind of observation you're talking about that led to the discovery of the expanding universe. Hubble observed in 1929 that distant galaxies in all directions were accelerating away from the Milky Way, showing that contrary to what scientists believed, the universe was expanding. Einstein's own calculations had shown him the universe must expand or contract, but he didn't trust them - until Hubble's observations. So your intuition is bang on!

Our 'observable' universe is spherical, but this is simply a function of time and the finite speed of light - we can only see as far as light has been able to travel in all directions over the age of the universe. The actual 'shape' of space is not thought to be spherical, but rather is flat with a margin of error of about 2% I think, over the entire universe that we can see. Space can take the shape of a cube or donut or soccer ball for example, while remaining 'flat' (or Euclidean), finite, and unbounded.

It still could be a sphere as I understand it - just a bloody big one, so big it appears flat on the scale of the observable universe!

Weird huh?

Pamela and Fraser, in the latest podcast talk about how the shape of space exists in multiple dimensions that are impossible for our three dimensional brains to visualise - other than to compare them to familiar three dimensional shapes like spheres and donuts and soccer balls. You have to consider just the 'surface' of the shape, which is two dimensional in our three dimensional space, then extrapolate it to higher dimensions. Then your brain melts. :neutral:

Steve Limpus
2008-Mar-26, 11:34 AM
topax i understand the concept

what i am unsure of is why relativity is not violated?

as i said there is no fixed background we measure our speed against

we can only measure it relative to another object

and very distant ones are ''moving'' away faster than c

:eh:

How about this -

We observe distant galaxies to recede at greater than c.

Photons from distant galaxies are stretched (red-shift).

However, we observe photons always move at c relative to Earth. Therefore relativity is not violated on Earth.

We accept the cosmological principle that Earth does not occupy a special place in the universe, which we observe to be homogenous and isotropic.

Therefore we conclude that photons must also move at c relative to distant galaxies, where relativity is also unviolated.

Hence, the space between distant galaxies has stretched.

General relativity supports that spacetime is elastic, and predicts that the universe must expand or contract except in the special case where the density and distribution of matter in the entire universe is perfect, virtually to the atom (which in any case would be violated the instant a heavenly body moved, thereby triggering a gravitational collapse of the entire universe).

Why?

Because. :lol:

:shhh:

...don't mention dark energy...

:wall:

...and I'm not sure we don't have a global reference frame - what about the CMBR? Don't we share co-moving co-ordinates or something?

:neutral:

damian1727
2008-Mar-26, 09:08 PM
who said cricket?

gaffo
2008-Mar-31, 01:25 AM
We are all traveling well in excess of c relative to something, this is true. There are parts of the universe that are separated by such a large amount that the expansion is pushing them apart faster than the speed of light.

The 'universal speed limit' of C only applies locally, which you can think of as being similar to your car measuring speed relative to the road or a plane measuring speed relative to the air it passes through. You measure your speed with a light clock and hence relative to the space you are traveling through.


Exactly! - where supposedly 3-percent of the universe we can see due to the galaxies traveling less than speed of light.

where does the 3-percent come from????????????? - hw de we know (or thing) that the rest of the 97-percent of the universe is beyond that "C" event horizon? - since we cannot observe galaxies that are receeding at rates greater than light speed.

I assume there could be an empirical "proof" of the assirtion that there is a universe beyond what we can observe (not that 3-percent - which I would welcome an answer to how you get that "assumption" - vs 30 percent or 0.00000003 percent of whatwe see is what is there) would be validated if one of there galaxies we now see decides to "dissapear" (due to the increasing expansion of the universe where the distant galaxy exceeds the speed of light (note the most distant galaxies now are in the ifrared.......................I assume we will find one in a lower radio spectrum - maybe radio.....on the "edge" (not of the universe but of our observable universe))..................and in a few million or billion years that radio source will eventually "end" WRT to us.

I assume one who lives on that galaxy WAY over at that edge of that 97-percent we cannot see.........would see a sky filled with only stars and galaxies over one half of the sky (and the flipped version of one at the other edge of the universe).

...............where we sit in the universe is not difinable from oversation.

in the center? - near one edge or near the other??????????????

....................


my question is WHERE DOES THE ASSUMED "WHAT WE SEE IS 3-PERCENT OF THE UNIVERSE".......................................how do make such a claim when the other 97-percent is theortically unobservable???????????

FriedPhoton
2008-Mar-31, 02:45 AM
In my case, gravity is making me shorter than I deserve. :)

In the immortal words of Garfield, "I'm not overweight, I'm undertall"!

Steve Limpus
2008-Mar-31, 03:31 AM
Hey FriedPhoton,

It wasn't always this way. I'm working on an ATM that gravity is increasing.

FriedPhoton
2008-Mar-31, 05:18 AM
Hey FriedPhoton,

It wasn't always this way. I'm working on an ATM that gravity is increasing.

:) Yea, yea... that's the ticket, gravity's increasing.

Vanamonde
2008-Apr-01, 08:19 AM
Mmm, okay, so for example...

Say, 10 billion years ago, a supergiant star went supernova in the halo of a young galaxy and sends photons that the Hubble Space Telescope focuses and images today.

But in 10 billion years, the universe has expanded so that star is actually, I don't know, about 50 billion light years away now. In the beginning, the star and photon are leaving each other at C but as the distance increases the space between them expands. and THAT makes them separate at a distance greater than C. But the image we see is a 10 billion year old image and we have no idea what that star is like in our time, today, at a distance of 50 billion light years.

We know that C is the limit in our accelerators, we push particles to that limit everyday and they will not go faster, just get heavier.

The photons are limited to C but spacetime is not. Spacetime is the medium that photon travels through.

Does that make sense?

And for my sake, please do not increase gravity. I have an hard enough time as it is! Now, if you could lessen gravity without losing the oxygen, I could support that!

Steve Limpus
2008-Apr-01, 10:13 AM
I can give you some rough figures for that:

The CMBR was emitted 13.7 billion years ago.
The particles that emitted the radiation were 40 million light years away.
The photons travelled 13.7 billion light years to get here.
The particles are now 46 billion light years away.
The CMBR was emitted at 380,000 years, redshift z=1100 (some one can probably tell us the recessional velocity for z=1100).
Expansion exceeds c at high enough redshift. (I don't know the figure.)

I think if you travel close to c your mass appears to increase to an observer (thats true at least for time and length, which seem normal to you but shorter and slower to an observer).

When my wife flies on the Enterprise I'm always careful when she texts "does my bum look big in this?"

Clegrand
2008-Apr-01, 10:26 AM
Steve, a friendly hint for you and any other male,

A woman does not need to be on the Enterprise for you to be careful when answering the "bum" question.

:lol:

Steve Limpus
2008-Apr-01, 11:29 AM
:doh:

Noted.

Thanks Clegrand.

gaffo
2008-Apr-02, 02:35 AM
Mmm, okay, so for example...

Say, 10 billion years ago, a supergiant star went supernova in the halo of a young galaxy and sends photons that the Hubble Space Telescope focuses and images today.

But in 10 billion years, the universe has expanded so that star is actually, I don't know, about 50 billion light years away now. In the beginning, the star and photon are leaving each other at C but as the distance increases the space between them expands. and THAT makes them separate at a distance greater than C. But the image we see is a 10 billion year old image and we have no idea what that star is like in our time, today, at a distance of 50 billion light years.

We know that C is the limit in our accelerators, we push particles to that limit everyday and they will not go faster, just get heavier.

The photons are limited to C but spacetime is not. Spacetime is the medium that photon travels through.

Does that make sense?

And for my sake, please do not increase gravity. I have an hard enough time as it is! Now, if you could lessen gravity without losing the oxygen, I could support that!



its more that that:

take what you said and re-write it a little:

"Say, 10 billion years ago, a supergiant star went supernova in the halo of a young galaxy and sends photons TOWARD that the Hubble Space Telescope WHICH ARE STILL BILLIONS OF LIGHT YEARS AWAY AND TRAVELING TOWARD US AT A SLOWER RATE THAN THE EXPANSION OF THE UNIVERSE so no focusing and no images today, tomorrow or ever."

"But in 10 billion years, the universe has expanded so that star is actually, I don't know, about 50 billion light years away now (or more like 500 billion light years) and not one photon as been able to rech us - not 10 billion years ago nor today nor tomorrow."

mtaylor
2008-Apr-02, 03:53 AM
I enjoyed the back and forth. Can I try an experiment to see if I understand this?

I fire photon A toward anywhere, then a second later I fire photon B in the same direction. Over time, the time-interval between A and B actually is greater than one second, because the "space" between them is growing? That is, if A stopped, it would actually take more than a second for B to hit it. Relative to me, A is still travelling at the speed of light and so is B, neither is travelling faster than c.

Vanamonde
2008-Apr-06, 05:55 AM
From better writers than I (e.g., wikipedia! at http://en.wikipedia.org/wiki/Metric_expansion_of_space):

Wow! That *is* some nice writing! Introducting the term metric and providing some background on that, really helps to understand the expansion of space better. I want to memorize this statement:

Superluminal space expansion

Because it is the actual metric that defines distance itself that is changing, rather than objects moving apart within space, this expansion (and the resultant movement apart of objects) is not restricted by the speed of light upper bound that results from special relativity.

EvilEye
2008-Apr-15, 03:22 AM
Then your brain melts. :neutral:

Mine doesn't.

For some reason I have no problem visualizing it. It's just a fat version of the surface of a balloon, turned in on itself. (like a 4d doughnut)

damian1727
2008-Apr-16, 05:56 AM
its the drugs...

Steve Limpus
2008-Apr-16, 06:25 AM
:lol:

dcl
2008-Apr-20, 02:58 AM
I've decided to get into this thread. Hopefully, my contribution will clear up the mystery regarding the apparent increase in mass of an object to an observer the faster it moves relative to the observer, apparently approaching infinite mass as it approaches the speed of light relative to the observer.

The thread started with a question based on a statement attributed to Dr. Gay: "Mass changes the faster an object travels" and asked, "How does the mass change? Does it stretch somehow like a string, grows bigger or smaller? How do we know this and what are examples of something's mass changing as speed increases? At which point or speed does the mass of an object begin to change? How would this affect human's traveling at greater speeds in our solar system?

The discussion must begin with our understanding clearly the distinction between what we mean by "mass" and "weight". Their meanings are vastly different. When we know the mass of an object, we know how hard it is to start it moving if at rest or to change its speed when it is moving. When we know the weight of an object, we know only how hard it presses against a stationary surface when resting on that surface. The latter is differs from one location to another. For example, you would weigh much less on the moon than on earth but much more on Jupiter. Your mass would be the same wherever you were as long as your speed relative to the observer was the same in both places. A child's coaster wagon and a locomotive, both at rest, on the earth are examples of objects with vastly different masses. A slight pull on the wagon's handle suffices to start it moving, but you must pull very hard and long before the locomotive is moving fast enough for you can detect any motion at all. The mass of the locomotive is much greater than that of the wagon.

The special theory of relativity says that the apparent mass of a body appears to increase as its speed relative to an observer approaches that of light. That doesn't mean that its mass actually increases. The theory says only that it appears to the observer measuring its speed to increase. However, this is not an illusion. The stationary observer would find that the speed of an object moving at a speed very close to the speed of light would show increrasingly great resistance to attempts to change its speed as it approaches the speed of light. An observer could not change the speed of an object moving at the speed of light at all no much force he expended in trying to do so.

The effect is highly nonlinear: It is negligible except at speeds very close to the speed of lighit. Then it builds up extremely rapidly, becoming infinite at the speed of light.

Another observer following the object at the same speed would see no change in its mass at all.

As they say, it's all relative!

Vanamonde
2008-Apr-21, 11:03 AM
Hey, I found these animations from the Relativistic Heavy Ion Collider (http://www.phenix.bnl.gov/WWW/software/luxor/ani/) site at

Search on "Head-on 200 GeV Gold+Gold"

At near light speed, the gold nuclei flatten into a "gluon wall" and then bang together.

I like to call these guys the Long Island Gold Bangers.

This is an animation, derived from the measurement of showers of pions that result and careful math to backtrack to figure out what happened. But the relativistic mass increase is actually measured - they have to adjust the timing and strength of the magnets to accelerate the nuclei.

dcl
2008-Apr-21, 03:19 PM
Vanamonde:

I tried the first of the animations to which you referred us. I had a terrible time with it. I found the background music so jarring that I could take it for only about three minutes. I utterly fail to understand why program developers feel that they have to provide a background of loud music to accompany spoken dialog.

With the narration turned off, the pictures tell me nothing, so I gave up on the animations. With the sound left on, the alleged music tended to drown out the narration so that I couldn't get enough of what was being said to make it worthwhile to continue listening. The fact that the narrator spoke so fast didn't help.

But thanks anyway for citing it. It's at least interesting to see that Brookhaven is trying to let the people paying for their work get a glimpse at what they're trying to do.

Anyway, I found your own remarks at least as informative as what I was able to make out of what the narrator was saying.

Some may not have fully understood the implications of what you said. I hope I'm not being too presumptive in adding the following: Pions are like protons and neutrons in that they're particles composed of quarks held together by gluons. Whereas each proton and neutron is made up of three quarks, a pion is made up of only two quarks. The gold ions are compressed in the accelerator along their directions of travel by the Lorentz contraction described by the Lorentz transformation associated with the special theory of relativity. Gluons are hypothetical particles that hold protons and neutrons together to form atomic nuclei. The collisions in the RHIC (Relativistic Heavy Ion Collider) are so energetic that the gold ions that are smashed together as they travel at relatistic speeds in opposite directions in the evacuated tube that protons and neutrons comprising the gold nuclei are torn apart into separate quarks that then instantly recombine into new protons, neutrons, and mesons.

Hey, I've just become a Member instead of a Junior Member, and in less than a month after returning to the Forum!

Vanamonde
2008-Apr-26, 04:59 AM
Eep - I discovered the animations at work where we have no audio - I did not realize it was so bad, sorry. And, dcl, I appreciate your expansion/addition. The words like "Lorentz transformation" are very, very new to me.

The main thing I got was at the speeds that RHIC reach, gold ions flatten into a disc that seems to one single subatomic particle deep! I read a couple of papers that refer to a "gluon wall" that forms. Something really weird that I really don't pretend to understand is going, even before the collusion.

Reality check time: The RHIC was reported to attempt to create a "quark-gluon plasma". And as I understand it, no quark or gluon has actually been obseved and QCD says that a single quark or gluon *can never* exist in isolation, so by definition they can only be observed by their effect. This almost sounds like "a circular delusion" but with much better math (that I cannot begin to understand), but these days, it seems that in the science media quarks and gluons are pretty much accepted. dcl, how hypothetical are they today?

And now, as I try to read what has happen that RHIC, it seems to be much stranger they ever expected.

I am assuming that by hypothetical, these particle have (and probably never will) leave a trail in a cloud chamber or be measured in a detector. Is the W and Z boson the same way? And will the Higgs boson have the same issue?

And dcl, you are just 40 more posts from seniority!

dcl
2008-Apr-26, 10:38 PM
Vanamonde: As an interesting sidelight on the Lorentz transformation, it was discovered that they were applicable to the Maxwell equations for electromagnetic theory before Einstein discovered their applicability to the special theory of relativity. As for the RHIC seeming to flatten a disk to one atomic particle deep, there's no limit to how thin a disk a piece of matter can appear to be compressed to under the special theory of relativity. It's not actually compressed at all if you look at it from a frame of reference moving along with it. It's all a matter of frames of reference, and no frame is any better than another, although one may be more appropriate to use as a reference frame.

I'm not familiar with the term "gluon wall". In particle theory, gluons are seen as the "glue" that holds protons and neutrons together to form atomic nuclei, hence the name "gluon". Particle physicists have been playful in naming particles, hence, "quarks", "gluons", and the names "up", "down", "top", "bottom", "charm", and "strange" for the six types of quarks.

The explanation for why quarks are never seen alone is interesting: They necessarily appear in pairs tied together as if by rubber bands. Pull a pair of quarks far enough apart and the rubber band breaks, leaving a pair of quarks at each end.

When introduced by Gell-Mann, quarks were regarded as convenient hypothetical particles useful in explaining the behaviors of protons and neutrons. It didn't take long until physicists decided that they weren't hypothetical but actual particles.

Quarks are not expected to ever be actually observed because of the fact that individual quarks cannot be isolated.