# J.C.MacSwell

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## Posts posted by J.C.MacSwell

### Sending Messages To M13 Star Cluster

I totally agree there Ophiolite which is why I think sending our codes to M13 is a pointless excercise; pherhaps aimed at a different location may be more, or likely to be beneficial.... everyones thoughts welcome[/b']...us.2u

There are aliens out there that "eat" gullible intelligent lifeforms. But they don't waste their time looking for them, that would make finding needles in haystacks seem easy. So they just wait for the signals...

### A bit confused with the massless nature of photons

So what exactly is relativistic mass?

I look at it as the "effective" mass if you wanted to accelerate it further and still use F=ma which would be incorrect otherwise at relativistic speeds.

### Collisions

Both? No. There will be an instant where the bug's center-of-mass has zero velocity in the horizontal direction, but not the car. (unless the bug was moving really, really fast[/b']) That will be true of any object that undergoes a change in direction of 180 degrees as the result of a finite acceleration for a measurable amount of time.

Or if the bug was really really massive!

### what if information can be transmitted faster than c

As relativity is not a classical effect, this is technically wrong. Classically, there was no speed limit.

I've seen a lot of references calling "classical" pre-quantum/post relativity (even though they overlap), although I was thinking the same thing.

1) A breakdown truck tows a car of mass 1000kg along a level road' date=' and accelerates 0.5m/s/s. What is the tension in the towline???

Ans: 1000/2 = 500N = the tension

2) A trailer of mass 1000kg is towed by means of a rope attached to a car moving at a steady speed along a level road. The tension in the rope is 400N, [b']why is it not zero????[/b]

Any idea to the question in bold????

thx

Albert

Are you assuming no friction?

### A question to all of you

I was pondering to myself the other day' date=' and it started to make me wonder.

What the heck is the 5th dimension?

I'm assuming it goes from:

Length

Width

Height

Time

???

In that order. [b'] Is it possible to have more than 4 dimensions[/b]? Am I out of my league? What about airline food? What's up with THAT!!!

Is it possible to have only 4 dimensions?

### Kinetic/Potential question.

eh?

it would have the same mass' date=' but less volume surely?[/quote']

Less volume means less buoyant force from the air. So if they weighed the same the larger volume would have more mass.

### Question about infinity and infinite possibilities.

if I choose a whole number between 1 and infinity' date=' and ask you to guess what number it is, am I making it Twice as hard for you by saying it can be a Half number too, like 1.5 for instance?

I don`t think it would be [/quote']

The way I understand the math "twice" would be correct, even though it is infinitesimally small. (and somewhat meaningless on it's own). Combined with other "infinites" it could make sense. So a finite density can be calculated from infite space and infinite mass.

You have to be careful though with infinites. Adding all integers to infinite and multiplying by 2 will give you twice as much. Multiplying every integer by 2 and adding them to infinite will give you half as much, you are effectively skipping every second integer.

### Super String Theory

The will of the universe causes the strings to vibrate... or not. Eh, who knows, i cant really think of how they could vibrate except from some divine source.

Of course I have an incomplete (read wrong) view of the Universe but I don't picture a vibration so much as cycles in extra dimensions. So this "space" combined with the energy/momentum in this closed "space" effects the "vibration".

### Plutonium question.

Are we still refining Uranium? How can we expect to make a bomb at this rate?

### harmonic oscillation problem

Yes' date='

wave speed = sqrt(tension/linear density)

However, isn't the tension 0? I mean it is just the rope hanging. Here is the exact wording of the question.

"A uniform cord of length L and mass m is hung vertically from a support.

A) Show that the speed of transverse waves in this cord is sqrt(gh), where h is the height above the lower end.

B) How long does it take for a pulse to travel upward from one end to the other?[/quote']

The tension would increase linearly from the bottom up.

### Question about infinity and infinite possibilities.

Would an infinite amount of matter not fill an infinite universe completely?

That's correct. It would not.

Actually you can divide infinites and get sensible answers. So assuming infinite universes like ours if you divided the infinite mass by the infinite volume you would get a sensible answer, which would be the same density as our universe.

### Question about infinity and infinite possibilities.

Because' date=' although it sounds contradictory, not all possibilities are possible.

For instance there will not be any planets made exclusively of jam and elephants.[/quote']

Let's say you "investigated" a billion planets the first second and every second you doubled the amount you had investigated the previous second. A year later you would have found no elephant jam planets and would start to feel pretty sure of yourself. 2 years later you would be getting pretty cocky. You would probably think "maybe it wasn't possible after all". But sometime in the third year you will come across a marmalade and beaver planet and your confidence would be shaken. Shortly after that you will engulfed in elephant and jam planets and won't know what to do with them all. Fortunately you have infinite space...

### New Theory?

There's more to it than that. There are strong theorectical reasons for the invarience of the speed of light in a vacuum.

The Maxwell equations' date=' which describe the behavior of all electromagnetic radiation shows that the speed of light in a vaccuum depends on two properties of the vacuum, its permittivity and its permeability. These two properties are constant regardless of whether you are moving or not. (If they weren't, you'd end up violating laws of conservation for one thing.)

At first it was thought that this speed was with respect to an aether, but when experiments failed to detect such, Einstein postulated that it was with respect to what ever frame it was measured from.

Also, the Maxwell equations tell us something else, if the speed of light were not invarient, then the equations do not transform between moving frames properly. The upshot being that an electromagnetic wave in one frame does not exist as such in a frame moving with respect to the first. A practical result of this is that you wouldn't be able to pick up a radio station in your car if you were moving with respect to the broadcast station.

Since it is obvious that we can listen to the radio while driving, it stands to reason that the speed of light is invarient.[/quote']

Invariant in rest frames.

I like your radio/driving reference. I've used "still see stuff after you start moving" kind of thing and noone knows what I'm talking about.

### New Theory?

I think that the energy that the photons were carrying gets absorbed into the glass atoms, so for a moment there is no photon, but an excited atom. Then the energy gets emitted in the form of a new photon. So the delay is caused by the brief disappearance of the photons.

I had always pictured it as a longer route. Like slalom skiing around atoms, still at c but effectively longer. Your view sounds more consistent with QED though.

### Question about infinity and infinite possibilities.

the other day i found myself in a heated debate with two of my friends about infinite possibilities.

their claim was that while adhering to the belief that the universe is infinite' date=' any kind of planet that could possibly exist WILL exist.

they used the example of a planet 100% identical to ours, the only exception being everybody spoke spanish.

taking what i know about infinity and numbers, and how an infinite set of numbers does not necessarily need to contain every number that there is i argued with them, saying that while it is possible that this planet could exist, it does not HAVE to, if there are infinite possiblities of planets that could exist, than there is nothing to say that a planet where everybody speaks spanish needs to exist.

i apologize if i didn't explain this clearly, but if you have some idea of what im trying to say im looking for any outside input anybody is willing to offer.[/quote']

Not sure if a a planet 100% identical to ours, the only exception being everybody spoke spanish, could exist. How could it have evolved?

But, if it could there would be an infinite number of them.

It's probably a silly thing to point out.

(In my defence, I would like to point out that in the vast majority of infite Earth's out there like this one I had something much more intelligent to say)

### Recommened book on String Theory?

Hey guys, I was wondering if there's a good book on the topic of String Theory. Thanks in advance!

The Elegant Universe by Brian Greene gives a good non-technical feel for the subject.

### Kinetic/Potential question.

I was thinking alont the lines of this...

Imagine 2 cubes' date=' one made of a very radioactive element and another of a non-radioactive element.

both weigh exactly 1Kg, and are suspended 1 meter above the floor.

do they both have the same potential energy?[/quote']

I'm going to be a pain and point out that if they "weigh" one kg the denser one will have less mass. Minor point, but it would overwhelm the other factors in significance.

### A few basic questions

Interestingly that is not quite true. You are correct in a general sense' date=' but if one probes an electron at high energies, you can see structure 'inside' the electron. This is because the electron is constantly emitting and reabsorbing photons, and if you look closely enough you can resovle these photons - so what you though before was just an electron, was in fact an electron plus photon(s). Of course, this is a bit semantic, since at what point do you really define an 'electron'. However, this is also true for the photon, and there is quite an industry now measuring the photon structure function in particle colliders.

Also, the point-like nature of particles (in your sense) is only confirmed up to a TeV or so. We cannot definitively say that they are point-like, only that they are smaller than a certain size.[/quote']

Also if there are extra dimensions (Kaluza-Klein theories) then what we consider a "point" may actually have structure.

### Deminishing Returns

']

1) Since this is a theory of yours' date=' you can assume that it is wrong simply because physists with more training/education/intelligance than you have probably already thought about it.

?[/quote']

Maybe his "thanks in advance" was a little prematue for your "insight".

### Deminishing Returns

My primary thought here is that the volume/mass of any part of the universe need not be a constant to be true to our observations so long as the volume/mass is consistent in a relative way.

If the universe were losing volume/mass on all matter' date=' if there were a uniform reduction in mass of every particle, then it would appear on the galactic scale that things were moving away from one another at a rate equal to the loss of mass. On the local scale the observable effects would be negligible as we would all be losing mass and getting smaller at the same rate and everything would appear to be stable in a relative way from our perspective.

.[/quote']

I don't think I know what you mean by volume/mass. Isn't it considered not to be constant? (volume divided by mass is increasing at a rate of the cube of Hubbles "constant")

### The Creation of Energy

There are a few things to consider. One is that the net energy of the universe could be zero' date=' [b']since gravitational potential energy is negative. [/b]

Another is that conservation of energy stems from the symmetry under time translation - that is, the laws of physics don't change in time. If it did, energy would not be conserved, and vice-versa. Since the laws of physics were set at the big bang, we can't say that energy conservation applies before it happened. The answer may be that we don't know, and can't know.

I read somewhere that thought stopped Einstein in his tracks while crossing a street.

Why is it considered negative?

Also when Galaxies are moved apart due to the expansion of the universe where does that energy come from? It cannot "simply" be momentum.

### Harmonics

That would be an absolute probability of 0.

That seems at odds with quantum uncertainty. I would have guessed that the chance of absorbtion would peak at certain wavelengths but not go immediately to zero either side.

### Collisions

Anyway' date=' what about the phases of particles then?

.[/quote']

Allow me to make myself clearer, at least to what I meant (if I can, bearing in mind that I do not have a clear picture in my mind as to what I'm trying to put into words, and as I learn more I can improve it)

(( I would say that the electromagnetic fields of their particles that are sufficiently "in or out of phase" interact after coming "in range".))

let me rewrite it as:

I would say that the electromagnetic fields of their particles, when the fields that make up the particles themselves are sufficiently "in or out of phase", interact after coming "in range".

The italicized part could be what "gives" a particle mass or charge etc.

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