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Moving at light speed


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#35 Buffy

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Posted 25 April 2005 - 07:35 PM

There you did it again. You responded to the whole message and deleted the actual point I was trying to make. There may be rules to this group that state you can do this but you've done this to me twice now. You are not the kind of person I would wish to discuss such a complex issue with. Very reactionary and unscientific. Sorry Tormod I'll get back to your message soon. Busy busy busy....

Huh. So I misunderstood you: you *are* arguing that there *is* an absolute frame of reference in the universe. That's all I can conclude because that was the only thing I edited out of your last post. That proposition I don't agree with as Special Relativity says there isn't one, and I think I said so a few times... but maybe you can explain what it is you mean.

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#36 Damo2600

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Posted 25 April 2005 - 08:42 PM

There is no use arguing with you Buffy.

#37 Buffy

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Posted 25 April 2005 - 09:08 PM

There is no use arguing with you Buffy.

Aww, c'mon don't give up so easy. Even Tormod sez he doesn't really understand what you're saying. I had a friend of mine who teaches physics at Berkeley to read this thread and he wasn't sure what you were trying to say either. Its clear you're a smart guy, we just aren't following what you're saying, and we're all smart folks with lots of letters after our names! Try again! It'll be fun! Honest!

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#38 Damo2600

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Posted 25 April 2005 - 10:13 PM

Hi Tormod,

The universe is expanding. It is also expanding in a uniform manner. So although there is a geographic centre we can't possible know where it is. This is because from where we sit it looks as if everything is expanding away form us. That would make earth the centre of the universe. The universe, as it is, is being pulled from all directions (isotropic gravity or universal gravity). The expansion rate of the universe can be measured and currently is perceived to be accelerating.

So according to us everything outside the hubble limit is moving at the speed of light. According to the unknown geometric centre galaxies are moving at the speed of light as well. IF we say that the geometric point in the middle of the universe is static then the galaxies at the furthest regions of the universe are moving much faster than the closest galaxies. You can try this with a piece of elastic.

Draw equal spaced lines on a peice of elastic and grab one end imagining this to be the centre of the universe. Take up the other end and imagine this to be the outer limit of the universe. When you expand this universe, by stretching the universe on one end, you will see that the outer lines are moving much faster from the centre of the universe than the lines that are closest to the centre. All the lines however are moving apart equally.

You cannot say that the closest galaxies are moving at the same speed as the outer galaxies. According to the centre of the universe we cannot say how fast our galaxy is moving. It's a very unusual optical illusion.

Therefore if I move an object at c - v = W, where v is the velocity of our galaxy, away from the expansion the velocity of the object will be c. According to us it is not but according to the centre of the universe it definately is. Since I don't know the direction of the expansion I can unwittingly do this.

So galaxies can and do move at the speed of light.

Look into cerenkov radiation which I have just been told does move at the speed of light. It actually killed a scientist.

Damien

#39 Damo2600

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Posted 25 April 2005 - 11:54 PM

Hi Buffy,

You just frustrated me by not replying to my posts entirely.

Damien (not letters attached)

#40 Damo2600

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Posted 25 April 2005 - 11:58 PM

Look into cerenkov radiation which I have just been told does move at the speed of light. It actually killed a scientist.


Sorry faster than the speed of light.

#41 Buffy

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Posted 26 April 2005 - 12:25 AM

You just frustrated me by not replying to my posts entirely.

Sorry! It just wasn't clear what you were trying to say.

Also, we don't care about degrees much around here. They're definitely not a prerequisite, just an open mind.

Are you familiar with the Cosmological Principle? (Wikipedia Reference here) What are your views on it? For all: there's an interesting simplified explanation of it here.

Cheers,
Buffy

#42 Damo2600

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Posted 26 April 2005 - 02:59 AM

Hi Buffy

I'm not sure why you would like my opinion. Why exactly are asking me?

Damien

#43 Qfwfq

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Posted 26 April 2005 - 03:28 AM

Sorry folks if I haven't been through this thread, I looked at the initial post.

Is the following statement true. If no why?

When a body with mass m0 moves at light speed his energy is infinity.

E = mc^2 = m0 * c^2 / sqrt ( 1 - c^2 / c^2) = m0 *c^2 / 0 = infinity

I know it's impossible for a body with mass to reach that speed, this is a theoretical question.

The statement is correct. In fact, it's the very reason why it's impossible for a massive body to reach that speed.

Look into cerenkov radiation which I have just been told does move at the speed of light. It actually killed a scientist.

Cherenkov radiation is light. I doubt it killed a scientist.

Way back in the '80s I was at the CERN labs, on a visit organized by the Physics dep't where I was studying. One of the researchers was showing us some stuff along one of the beams and explaining about the key system to garantee runs can't be done while you're inside, you take one key and the beam can't come before you've put the key back. He told us that once one of the Soviet guys didn't take a key at all, he was fully accustomed to looking into the beam to see the Cherenkov light, so seeing where the beam is, when making some adjustments.

The beam itself isn't so healthy, I'd say it's more to watch out for than the Cherenkov light.

#44 Damo2600

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Posted 26 April 2005 - 04:04 AM

'Why exactly are u asking me?' is what I had meant to say.

#45 Tormod

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Posted 26 April 2005 - 05:59 AM

The universe is expanding. It is also expanding in a uniform manner. So although there is a geographic centre we can't possible know where it is. This is because from where we sit it looks as if everything is expanding away form us. That would make earth the centre of the universe.


This is the definition of the *observable* universe, not the universe as a whole. We cannot know that it is expanding in a uniform manner everywhere, we can only assume so. I see no reason why it cannot expand at different rates in different places - we know the speed has changed over time, so it could arguable also change locally.

And we have no idea what is outside the boundaries of the observable universe, except that we can assume that "it is more of the same", or it is not.

The universe, as it is, is being pulled from all directions (isotropic gravity or universal gravity). The expansion rate of the universe can be measured and currently is perceived to be accelerating.


This I agree with. The expansion rate seems to be accelerating, and it has apparently done so for at least several billion years. Prior to that it apparently was slowing down, according to research published by (among others) Paul Davies et al.

IF we say that the geometric point in the middle of the universe is static then the galaxies at the furthest regions of the universe are moving much faster than the closest galaxies. You can try this with a piece of elastic. ... So galaxies can and do move at the speed of light.


But see, I disagree that the universe has a center. So nothing is moving "away". From any point in the universe, everything else will appear to move away from you, and what is at the furthest point away from you will appear to move faster, even if it really isn't.

So IMHO the real illusion here is that something with mass appears to be moving at the speed of light. They are not moving like that - they only have local velocities, the perceived velocity is due to the expansion of spacetime.

This is examplified by drawing dots on the surface of a balloon. Blow some air into the balloon so it expands, and the dots will move away from each other. Yet they are not moving away from a center, and they all stand still compared to their local space.

Like the surface of the balloon, our universe is not a sphere. It only appears to be because we assume the observable universe = the universe.

#46 Tormod

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Posted 26 April 2005 - 06:02 AM

You are not the kind of person I would wish to discuss such a complex issue with. Very reactionary and unscientific.


Please refrain from phrases like this. If you dislike the other person in a discussion, keep it to yourself or stay out of the thread.

#47 Damo2600

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Posted 26 April 2005 - 08:22 AM

Hi buffy, You and I are both right.

I'm sorry. If you consider we travelled to the centre of the universe. From there we would see the centre of the expansion. Right? This point we would have to say is stationary.

Now suppose that red shifiting did not exist and we could se the whole universe. From there we could see all of the galaxies moving at their various speeds right. At the hubble limit we would see the galaxies moving at the speed of light. Beyond this point all the galaxies would be moving faster than the speed of light (Away from the central point). Right? This does not violate the Theory of Relativity because although the galaxies ARE moving faster than the speed of light the affects are not experienced due to the fact that the galaxies aren't moving against the grain so to speak. If an object could be accelerated to the speed of light it would increase in energy. This is because it's inertial mass is causing pressure (by smashing into particles) and You would need EXTRA acceleration to maintain the speed. A galaxy moving at c or faster does not experience such inertial pressure because space is litereally moving with it.

I'm sorry that I argued with you but I WAS sure that the galaxies were moving at the speed of light. So they are travelling at the speed of light however it is merely due to the expansion of the universe (like you said).

However you helped me to see the biggest optical illusion of all: Relativity

Now I may be a complete idiot here but in reading Einstien's Theory of Relativity I came under the impression that time is not constant. As everyone else did apparently. However I'm not sure what that means.

This is completely absurd. Now *you* are in a train travelling at 200 000 kms/second in a straight line. *I* am standing at the station. According to Lorentz Transformation I calculate your time to be moving at a slower pace than my time. Right. However you calculate my time to be moving at a slower pace than yours. Right? Would I be right in assuming that *our* clocks are actually equal and that the percieved time difference is merely an illusion. I have been told that the Lorentz Transformation is extremely accurate and it's calculations are empirical. I can accept that. I'm not sure if the understanding of this is that time actually slows down or not. I am having difficulty in seeing that time has actually slowed down.

If your clock is going slower than mine and my clock is going slower than yours can't we therefore assume that they are travelling at the same speed. Is this right? You can place length contraction in the same category right?

Well anyway at the risk of looking like the biggest idiot in the universe I am going to post this message anyway.

I am so confused???????

Damien

#48 Damo2600

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Posted 26 April 2005 - 08:33 AM

I apologise sincerely to Buffy. I was extremely arogant.

My sources on the Cherenkov were incorrect aswell. The actual effect is known as 'blue water' Perhaps someone else can explain it. Apparently the radiation moves faster than the speed of light in the water. It does not travel at the speed of light in vacuo. Apparently it is deadly though in this form due to it's extreme heat.

It's not really relevant to the subject however.

Humble apologies
Damien

#49 Tormod

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Posted 26 April 2005 - 08:47 AM

Now I may be a complete idiot here but in reading Einstien's Theory of Relativity I came under the impression that time is not constant. As everyone else did apparently. However I'm not sure what that means.


I gotta run now but here is some light reading for you:
http://www.garlikov.com/teaching/time

Okay, not so light. Time and relativity is not something one learns in an afternoon...if even in a lifetime. :eek:

#50 Qfwfq

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Posted 26 April 2005 - 09:41 AM

This is completely absurd. Now *you* are in a train travelling at 200 000 kms/second in a straight line. *I* am standing at the station. According to Lorentz Transformation I calculate your time to be moving at a slower pace than my time. Right. However you calculate my time to be moving at a slower pace than yours. Right? Would I be right in assuming that *our* clocks are actually equal and that the percieved time difference is merely an illusion. I have been told that the Lorentz Transformation is extremely accurate and it's calculations are empirical. I can accept that. I'm not sure if the understanding of this is that time actually slows down or not. I am having difficulty in seeing that time has actually slowed down.

Damien, the Lorentz transformations are coordinate transformations appropriate for space-time and they are such that the velocity c is equal for all observers. Observers travelling at different velocities see the interval between two events as having different spatial and time components, somewhat the way two observers looking in different directions see different x, y and z components.

The two clocks issue shows shows that it doesn't make sense to say that "time slows down" or similar things. The time that counts for how things happen in a given object is that object's so-called proper time. Observers at different velocities see that object's events happening more slowly because the spatial and time components between events are different, for these different observers. This is quite unlike saying that it's only and illusion and it can be and has been verified.

#51 Damo2600

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Posted 26 April 2005 - 09:53 AM

Hi Tormod,

I read the link and would like to go through the first example with you. I would implore anyone to go through the example as well to see if we are all getting the same results.

I will call myself completely ignorant in advance so as not to make a fool of myself when the problem is solved.

I have a problem however and seem to see this as a rather bad trickery of math. Now the ratios given of the time differences seem to be off. Now if Brian, who is moving away from alfred, is flashing his radar pulse every 6 mins then alfred will recieve these pulses every 9 mins after 12.00 o'clock. This is O.k. by me.

Charles, on the return trip, flashes his pulses every 6 mins and I calculate that Alfred should recieve them every 3 mins not 4 mins. This is because every 6 mins that Charles travels there is 3 mins less that it takes to reach Alfred. So that would make both Alfred and Charles times equal 2.00 o'clock.

What exactly am I doing wrong here?

Damien