# Expanding space?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by kaneda, Nov 7, 2007.

1. ### kanedaActual CynicRegistered Senior Member

Messages:
1,334
The bible and elsewhere told us that demons caused illness. Finally people decided that maybe illnesses may have other causes and found them. You tell me that time dilation exists. I know that time is not a dimension so it is a matter of looking for the right explanation. Have you got a 300 metre plus cloud chamber for me too, to prove time dilation? Or are you just parroting what you have been told and what you have read?

Circular motion at constant speed is not centripetal acceleration. Where do you get this rubbish?

3. ### 2inquisitiveThe Devil is in the detailsRegistered Senior Member

Messages:
3,181
kaneda,
Heh. No, the muons are accelerated to within a hair of the speed of light. At that speed, the muons make several complete circuits of the collider ring, many thousands of meters, without decaying.

I said a particle, or clock, that moves in a circular motion at a constant speed will experience a centripetal acceleration. Drive your car in a circle at any sufficient speed and you can feel the acceleration even if you do not further increase the speed indicated on your speedometer.

5. ### kanedaActual CynicRegistered Senior Member

Messages:
1,334
Evidence that they are the same muons doing the circuit? As I understand particle accelerators, it is only on impact or in cloud chambers that you know what particles you have.

Centripetal acceleration is when something spirals in towards a centre at a faster speed. A bit of a contradiction in terms really since if something spirals in faster, it will then have sufficient energy to move further out.

If you drive your car around a circular race track at (say) 100 mph, then centrifugal force will try to make you move away in a straight line while your car will force you to turn, so keeping the circle. But I still cannot see where acceleration comes in to it.

7. ### 2inquisitiveThe Devil is in the detailsRegistered Senior Member

Messages:
3,181
kaneda,
It has been awhile since I researched the mechanics of the modern particle accelerator/colliders, but I will try to explain the process in as few words as I can. The newest colliders, such as the Large Hadron Collider (LHC) due to begin operation in 2008, are designed with more rings than just the large main ring. Muons are produced in one of the smaller rings to begin with, which some designs have two straight sections with curved sections at each end. Kind of like an oval that is flattened on each side. Protons are accelerated in this smaller ring and collided with a target usually made of carbon to produce pions which very quickly decay into muons. Magnets (muons are charged particles) are used to quickly 'round up' the muons into a compact group of muons in a process called 'cooling'. The compact group, called a 'bunch', is quickly injected into the vacuum of the large, main accelerator ring where they are very quickly accelerated to very near the speed of light, something like .9999c. At that speed and energy, the muon's mean lifetime of 2.2 microseconds is increased to around a millisecond or more, according to their speed. A millisecond is 1/1000 of a second. At .9999c, the muons could travel almost 299,458 meters in one millisecond, making many trips around the ring, however thay are not at that speed their entire lifetimes. They can still make many complete circuits. The muons are tracked around the ring and accelerated each time the bunch passes over an acceleration 'gap'. The 'gap' works to accelerate charged particles by first emitting a current opposite to the charge of the bunch while the bunch approaches the gap (opposites attract), then switching to a like charge when the bunch passes over the gap (the like charge repels the muon bunch). For instance, if the muon bunch that was collected is of negatively charged muons, the 'gap' will first emit a positive charge to attract the muons toward the gap, then a negative charge as the bunch passes over the gap to repel them away. Muons can be either negatively or positively charged when produced, but the magnets used when they are first produced in the smaller ring will separate them into either positively or negatively charged bunches. This whole process is very complicated and requires great precision, I just tried to make it as simple as I could. I, of course, am no expert at collider operation. Someone may wish to correct or enhance this post made from memory. I just know some of the basics. I used find reading about and studying colliders very interesting.

I think you may be thinking of acceleration as it is used in everyday language, such as stepping on the gas and feeling your car accelerate forward while increasing speed. Stepping on the brakes, what most think of as a de-celleration, is actually an acceleration in physics. Standing in one spot on the surface of the Earth, you feel the acceleration of gravity pulling you towards the center of the Earth. Gravity is a centripetal acceleration. The Earth's surface offers resistance to the acceleration and you feel the force against your feet.

8. ### kanedaActual CynicRegistered Senior Member

Messages:
1,334
A muon has a lifetime of 2.2 microseconds. It is said to have a longer lifetime if moving at near light speed, through time dilation.

However, muons are created, rounded up and then accelerated to near light speed. How long does this take out of the muons 2.2 microsecond lifetime, to leave sufficient to reach near light speed and to have dilated time left to travel around the circuit (of 27 kilometres)?

There is the point here that in a normal lifetime, a muon is going to travel just 660 metres. So even allowing for that, the muon has to go from capture to almost light speed within what, 100-200 metres or it will just decay out of existence. I always thought such particle accelerators accelerated particles more each time they went around the circuit but what you are saying is that they are accelerated to full speed almost instantly. Right?

I don't see what gravity has to do with this. If something is moving at a constant speed, then it is not experiencing acceleration. You could say there is forces X, Y and Z acting on it but acceleration as far as I know is when one of these forces is sufficient to overcome the others, which they are not here.

Messages:
10,296
It's a brand-new year and I'll break my silence toward you in an attempt to explain something.

Evidently you are unaware that gravity and acceleration are indistinguishable. One good example of a smooth (unchanging speed) circular motion producing a constant acceleration (gravitational effect) is the ordinary centrifuge.

It's done in hundreds of labs all across the world everyday to speed up the normally slow process of gravitational settling of material contained in a liquid. (Blood fractions, DNA material, and thousands of similar applications. Perhaps THE most common of all is separating cream from milk.)

Messages:
10,876
11. ### superluminalI am MalcomRValued Senior Member

Messages:
10,876
Maybe what he meant to say was, something in uniform motion? Which would clearly convey that he was talking about an inertial frame of refernce(i.e. a constant velocity (vector) ).

What do you think?

Messages:
10,296
Between you and me, I don't believe he even accepts that there are frames of reference! Nothing he's said that I can recall ever indicated he did. Plus, NO expanding space, NO Doppler effect and a dozen or so other huge gaps in his meager understanding. It's worse than pitiful, it's pathetic.

I cannot recall ever having felt such a strange combination of pity and nausea. (Unless it's also because of that other fraud guy.)

13. ### kanedaActual CynicRegistered Senior Member

Messages:
1,334
Don't you ever do anything but snipe and whine?

Of course you don't recall for example where I gave (a few times) the case of a torch being used in the direction of travel in a spaceship travelling at C/2. Stop lying to get your hate across.

14. ### kanedaActual CynicRegistered Senior Member

Messages:
1,334
January 1st and you've already won the "Creep of the Year 2008" award. Way to go!

15. ### kanedaActual CynicRegistered Senior Member

Messages:
1,334
Read-Only. Less than seven hours into the new year and you have already broken your resolution. Not very strong willed, are you?

Saying gravity and acceleration is the same is like saying infra-red and microwaves are the same because they can both heat things. Gravity is a pull towards a centre of mass whereas acceleration is a pull in one given direction, often having nothing to do with mass.

In a centrifuge, the object wants to go in a straight line but the container pulls it sideways, so giving the idea of a circular motion. It is not gravity causing blood cells to settle from plasma but the container which stops the material from moving in a straight line, as in when you drive around a corner too fast and find yourself leaning away from the corner. As far as I know, no one has said that centrifuges work by gravitons. You are playing with words.

Messages:
10,296
Like others have said before, you really don't have a clue about actual physics. Hopeless and helpless.:shrug:

17. ### losfomoTUnregistered UserRegistered Senior Member

Messages:
125
Gravity and acceleration are not the same thing. They both exhibit the same effect (force), but from different causes. I challenge you to dispute this: You are knocked unconscious and wake up in a 10 x 10 x 10 foot enclosed room. You can have any measuring device you desire, but you cannot leave the room or see outside the room... How can you tell if it is gravity holding you down, and not acceleration? IOW, How can you make the distinction between being on Earth, or being in a spaceship accelerating at 9.8 m/s/s? Answer: You can't, because the two forces are equivalent.

You are the one who most definitely likes to play with words. Nobody said acceleration is gravity. Acceleration and gravity exhibit equivalent forces.

18. ### kanedaActual CynicRegistered Senior Member

Messages:
1,334
I'll have a small cloud chamber to detect whether I am in space or on a planet, using cosmic ray hits. Or just a standard compass.

On a small enough scale, all of the Earth attracts us whereas acceleration works solely opposite to the direction of travel.

You have a dinner served up. How do you tell if it was cooked in a microwave or in a conventional gas oven?

19. ### kanedaActual CynicRegistered Senior Member

Messages:
1,334

Another empty quote from an empty head. As much science as the average creationist uses. How is God today?

20. ### superluminalI am MalcomRValued Senior Member

Messages:
10,876
Ok. I want to play.

You're in a 10x10x10 box and you are either:

accelerating at 1m/s/s or

on a small planet with no atmosphere or magnetic field.

(not that this has nothing to do with the intent of the equivalence principle, that kaneda has no understanding of. It's just a game)

cmon! Play!

Messages:
10,296
A good example - there's absolutely NO way to deterimine which of those is your external environment.

Without a window, you could have ANY and EVERY type of scientific device at your disposal and not be able to tell the difference.

22. ### superluminalI am MalcomRValued Senior Member

Messages:
10,876
Hi RO,

There is one way, but it has no effect on the equivalence principle. It's a geometric way.