Jacques

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

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...

That is a kind of problem that cost a lot : http://www.wired.com/2010/11/1110mars-climate-observer-report/

Thanks for your answer and interest. 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.

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.

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 ?

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.

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...

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

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

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 ? 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...

OK Thanks I know that antimatter is observed. The complete equation for antiproton creation is: [math]p^+ + p^+ + 2(m^pc^2)\rightarrow p^+ + p^+ + p^- + p^+[/math] where [math]m^p[/math] is the mass of the proton

Thanks for your answers. 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

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

Thanks for you link.

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/

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.

186000 mi/sec or 300000 km/sec

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'

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.

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.

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.

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.

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

From zorro 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.