# Jacques

Senior Members

562

## Posts posted by Jacques

### Time traveler puzzle

He doesn't see himself traveling into the future because he see himself traveling into the pass.

### Bias in particle collision experiments

Particle collider mostly use electron-electron or nucleus-nucleus for there experiment. There is a conservation law about the electric charge.

Does these experiments are biased by using particle with the same electric charge ?

For example if you collide proton with proton the result should be mostly positive charged particle.

Just a thought...

### Comet deviation

The basic idea is somekind of mass driver, expelling some mass (water vapor) from the comet, but without all the mechanical part. I thaught of using nuclear power because of the higher power density, but it seam that you cannot control a nuclear reactor without some complex feedback mechanic. Maybe it would be possible to have a subcritical mass and have a neutron source turn on when in place.

I was targeting the pole so it can work all the time.

### Comet deviation

Swansont

Does a nuclear reactor is critical or is it subcritical ? Can we used some uranium mixed with some moderator and have it warm enough but not explose ?

Maybe I used a to hight temperature, but the idea is transform the ice into steam to propel the comet.

### Comet deviation

Hi I had an idea that might interest some people here, and I would like to have some comment on that idea.

There is a possibility that someday we will find a comet heading to earth and we will try to deviate it so it miss the earth.

There are many senario's proposed, but mine is so simple:

Take a big mass of nuclear fuel and crash it on one of the pole of the comet.

Make it crash at a speed so the mass will penetrate between 10 and a 100 meter.

The nuclear mass is subcritical so it wont detonate, but massive enough to come to a temperature of around 1000 Celsis.

The interior of the comet is mostly water ice and the water will turn into steam that will exit by the entry hole providing some trust.

Is it a realistic scenario to change the orbit of a comet ?

How much fuel would be needed ?

How long before the hole get to large ?

### The CMB, how is that possible?

The temperature of the era of last scattering was around 3000 kelvin - the cmbr is now 2.7 kelvin. The drop in temperature is due to the red shift caused by expansion and is of the same ratio - this scale factor is about 1100. So what is 46 billion light years across now was about 44 million light years across then.

And re the black body spectrum - that is my understanding as well

So if the universe was 44 million light years across, we should have received that light a little bit more than 44 millions years latter even with the expansion of space. So the CMB is not photon directly received from that era but more echo.

### The CMB, how is that possible?

The universe was ~380,000 years old when the universe became transparent

What was the size of the universe at that time ?

I don't know, but it must be a lot smaller than today, and I can suppose that the CMB had time to pass by us.

May be the CMB we detect now is just the echo of the photon that was absorbed and reemited and reabsorb etc...

### When a photon is released, which way does it head?

Hi

I didn't read all the posts and I don't know how the subject is now the twin paradox, but I have some taught about the original question:

When a photon is released, which way does it head?

Some photon are realesed by excited atoms. Considering the law of conservation of momentum we can imagine a situation where we can predict the direction of the released photon.

Consider an atom at temperature close to 0K so it can be considered stationary.

Shot a photon from the left on that atom. If the atom absorb that photon , the conservation of momentum tell us that the atom will be moving to the left. After a while the atom is de-exited and emit a photon of the same momentum as the incident one, so the photon will continue in the left direction and the atom will stop.

Is it theoriticaly correct ?

Is it pratically correct ? (I guest that we cannot have a stationary atom because of Heiseinberg uncertanity)

Just a thaught

### Low Energy Nuclear Reactions / Cold Fusion (thread split)

If it was real, it would be on the market and the inventor would be rich.

### Matter-antimatter asymetrie

Kramer, you know well it's not "easy question"..

I would run into speculation while trying to answer it.

It is not 2mpc^2 but more, see article here

http://galileo.phys.virginia.edu/classes/252/particle_creation.html

Thanks for the link. But would it be correct if it was a collision between two proton beam , instead of a proton beam hitting stationnary proton ?

I have simple questions for both Sensei and Jacques:

How can happen that “two protons”-- becomes four?

Or how comes that energy 2*(m*C^2) (a very weird concept of how it exist in undefined space, together with many kind of energies that occupy the same undefined space) suddenly shrinks in a very small two portion of space called p and –p.?

Any theoretical clue how it, supposed to happens; any trying experimental work in real science laboratory about its possible mechanism?

Very hard to explain how it is happenning, specialy for proton antiproton because they are composed of 3 quarks. I can speculate that there is an intermediate state where the is some gamma ray of hight energy.

We can try to simplify the question with electron-positron creation by a gamma of 1.1Mev.

But we don't know how it is happening to. I can speculate some self-interaction of the magnetic and electric field of the gamma photo to create 2 loops . One for the positive phase of the photon and the other one for the negative phase...

I don"t know if I remember well but I read that a 1.1Mev will not spontanously transform in the electron-positron pair. The photon need to pass by a heavy nucleus...

### Matter-antimatter asymetrie

CP violation is observed in the weak sector, but not as far as we know in the strong sector. My understanding is that there is no fundamental reason why we should have CP conservation in the strong sector, but we have not seen any real evidence of violation.

OK Thanks

Learn about beta decay plus.

In this process unstable nucleus (proton rich) is emitting positron. Antimatter, antiparticle of electron, with all properties the same as electron, except charge.

Are you expanding your idea also to positrons?

Learn how antiprotons are created in particle accelerators:

$p^+ + p^+ \rightarrow p^+ + p^+ + p^- + p^+$

Relativistic accelerated proton is colliding with proton at rest, and 2 new proton-antiproton particles are created in this process.

I know that antimatter is observed.

The complete equation for antiproton creation is:

$p^+ + p^+ + 2(m^pc^2)\rightarrow p^+ + p^+ + p^- + p^+$

where $m^p$ is the mass of the proton

### Matter-antimatter asymetrie

The discrepancy between matter and antimatter is attributed to CP violation in the weak sector of the standard model.

I thought that it still a theory and that there were no observation of that violation.

The idea of antimatter being matter going back in time is untestable, but can explain some particle process with Feynman diagram, and the matter-antimatter asymetrie. Why should we discard that idea ?

Thanks

### Matter-antimatter asymetrie

Hi

Where is the antimatter ?

During the Bigbang the energy 'condensed' into matter and antimatter. If we accept the Feynman–Stueckelberg interpretation of antimatter, that antimatter are particle going back in time, then there was nothing before the 'condensation' so the antimatter never encontered matter. Anti matter that was created in that time are going back in time and will never meet matter.

Is it something that was thaught before ?

Thanks

### Blacks Holes? yes/no?

Thanks for you link.

### Blacks Holes? yes/no?

Hi

I just saw that news and it way over my knowledge. Negative energy, hawkin radiation are for me very abstract.

Is it possible that the autor is right, that black-hole are not able to form ?

Then what is observed at the center of all galaxies ?

Very currious about the opinion of expert here.

http://www.universetoday.com/114802/there-are-no-such-things-as-black-holes/

### Blasts via nuclear fission

The H bomb use dynamite to ignite a fission reaction, that ignite a fussion reaction.

The first explosion compress the fissible material (Uranium or plutonium) over the critical mass where the chain reaction start. That fission explosion compress and heat some hydrogen or deuterium that start fussioning.

### Light Has No Speed + Space-time can disappear!

186000 mi/sec

or 300000 km/sec

### No need for dark energy

The unbolded is what Jacques is getting at. The bolded contradicts what was just stated.

If the natural rate of expansion (assuming there is one) is being retarded by gravity, but that effect is reduced over time from the expansion, then the expansion will increase over time (accelerate) as it approaches that natural rate.

The rate of acceleration will diminish but always be positive.

Edit: not sure if that actually fits the data just that it is based on Jacque's assumptions

That is exactly what I mean.

I read about Einstein equation for general relativity, and I was wondering if Lambda is the samething as the scale factor for what I call 'natural expansion'

### No need for dark energy

As far as our understanding of the laws of physics go, a "natural" expansion that is not driven by some type of energy would expand at a constant rate if you were to remove gravity. Adding gravity will slow the expansion. The fact that gravity falls off with distance just means that its ability to slow the expansion decreases as the universe expands. In other words the rate of slowing would decrease with time (but would never drop to zero). In order to have an expansion that accelerates over time, you have to have something driving it.

Now it just might be possible that our understanding is incomplete, that over large distances "natural" expansions do tend to accelerate or maybe gravity itself becomes repulsive over great distances.

This is where "dark energy" comes in. It is a placeholder term for whatever we eventually determine causes the universe to behave contrary to our expectations, whether it involves an actual form of energy or an adjustment to our present theories.

Your "explanation" seems to fall into the second category, however it doesn't give any explanation as to "why" an accelerating expansion is "natural", considering that present day physics holds that it isn't.

You almost understood my point. It is natural for space to expand. I will try to put some math.

Space expansion factor is everywhere the same and I will denote it as a scalar S

Gravity is function of masses and distance. Mass is constant so I will represent gravity with g(1/r^2)

Inside a cluster S - g(1/r^2) < 0 then inside cluster there is no space expansion.

Outside a cluster S - g(1/r^2) > 0 then space expand so r increase and become r'

S - g(1/r'^2) > S - g(1/r^2) then space expansion effect is stronger with time.

### No need for dark energy

The point of dark energy is not to explain the expansion itself, but the observation that the expansion is speeding up.

Yes that the point. Space expansion is natural. It is measured and it is happening everywhere where there is not enought mass outside of galaxy cluster. The acceleration of the expansion is also a given observed by distant supernova. The accepted explaination is there exist a dark energy to accelerate this expansion.

My point is that, there no need for dark energy to explain the accelaration of the expansion.

Gravity is a force who is inversly proportionnal to the square of the distance (Newton). The space expansion is proportionnal to the distance (Hubble).

Inside a galaxy cluster gravity win over space expansion. Between galaxy cluster space expansion win so the distance between cluster increase and if the distance increase the influence of gravity diminish. The reduced influence of gravity, leave more place for the expansion.

I hope you understand what I mean.

### No need for dark energy

The expansion of space is accelerating, space is expanding faster than before. From the supernova obsservation that is a fact.

What I don't understand is why do we need dark energy to explain that acceleration, when ther is a simple explaination:

Gravity is opposed to space expansion. Space expansion happen when gravity is not strong enought like between galaxy cluster. Earlier in the cosmos history cluster where closer together and gravity between cluster was bigger because of smaller distance, but not close enought so the space expansion brought these cluster further apart. If the distance between cluster increased, then the gravity between them decreased, so there was less force acting agains the space expansion giving a net increase in space expansion.

I don't know if you understand the idea, it is hard for me to explain that in english, but if you need clarification just ask and I will try to clarify my idea for you.

Maybe it is already in the calculations done by cosmologist, but I cant tell.

### Expansion

Dark energy, the source of expansion, is thought to permeate all of space, including the space within our bodies. Dark energy is weaker than gravity on relatively small scales, such as between planets in our solar system, stars in our galaxy, and even galaxies within our supercluster. These objects are gravitationally bound and the force of dark energy is not powerful enough to overcome that gravity. On a relatively large scale, such as between superclusters of galaxies where gravity has weakened enough due to great distances, dark energy is powerful enough to overcome that weak gravity. Therefore the expansion of the universe takes place between superclusters.

I don't think that dark energy is the source of expansion. I think that dark energy is responsible for the acceleration of the expansion of space.

### Greenhouse effect

hello, jacq:

The input energy must be the major factor in computing energy transfer and reflection. Energy input here is Solar Winds and other magnetic emissions from the sun. All are deflected by the Magnetosphere.

If your computer analysis lacks this and other significant and factors, it isn't useful .

zorro ....

Energy input from the sun:

Solar wind is almost zero because of the magnetosphere deflect these charged particle.

Solar radiation roughly 1.361 kilowatts per square meter (kW/m²) Wiki Solar Constant

### Greenhouse effect

From zorro

magnetosphere controls sun's input

Please explain and please don't resend your image of the magnetosphere.

Solar wind is not part of the equation. Solar radiation is the factor to consider and it is not influenced by the magnetosphere.

×