Recent content by JV

Possibly you mean "solar shock wave"? The sun emits charged particles (electrons, protons ) this is called "solar wind". When this wind hits a magnetic field of a planet, it creates a solar shock wave.

So it is no problem for a satellite to orbit the moon (stable), as long as it is close enough in the "Hill Sphere". Apparently it is just a coincidence that there is no example of a moon orbitting a moon in our solar system. At least the chance of it happening was just small, but it is their...

Making a shuttle in the first place was more a PR thing than a technical wise decision. It is very expensive and it is not a very save. Astronauts have no means of escape. The russian sojuz is a much simpler and saver concept. When something goes wrong during lift off, the top of the rocket...

Are there any moons in our solar system that have moons? Or is this not possible, due to instability?

It seems that planets can not exists around twin-stars or even triple-stars. I mean that the planet orbits both stars, and not just one of the two/three. Why is that? The planet can just circle around the centre of gravity, what is so special about a twin or triple-star system?

Do these finding not demonstrate then that the condensation theory is wrong. As I understood, from previous replies, that due to the heat of the star the light gasses (H, He) escape to space. It seems that this theory is written to fit the current situation is our solar system?

maybe: - the first three minutes - genesis, is already used, i think. - expanding - high density - t=zero

I don't think that's true. Life (as we know it) needs liquid water, light is not needed. In caves and at the bottom of the ocean there are a lot of living creatures, and they don't get any light. So in theory live could exist on a rogue planet. As long as it has a hot core, for pockets of...

In another thread: "When is a planet a planet?" https://www.physicsforums.com/showthread.php?t=46968 Someone mentioned that normally the outer planets in a solar system are gas-gaints and the inner planets are big "rocks". Why is that? Why can the gas-gaints not be the inner planets?

Would it be possible for a planet by collecting gas to become a star. I mean if it were to collect enough hydrogen, the temperature and the pressure at the surface of the planet could get high enough to start fusion ?

This seems a strange statement to me. I would expect that all the objects (both BH and earth) will fall toward the center of gravity. The Earth also has an attractive force on the BH. This would be a way for us to simulate anti-gravity. Take a BH near the Earth and objects will fallup. So will...

Does something like anti-gravity exist, in theory? I mean two masses repeling each other. Or in terms of space-time: an upward curving. And if so, does that result in anti-mass?

There are many more objects in our solar system besides planets. The astroid belt is full of big rocks. Why do we not consider them planets? Or what is the minimum size of a planet. And what is the minimum size of a moon? There are a lot of small rocks around saturnus, how big must they...

yeah, but a photon has energy. And energy is mass (E=mc2). So a photon traveling at c, has mass. And how can a photon have a momentum without mass??

Frankly, i do not understand what the excitement is all about. Although it is very spectacular, it is known a long time that galaxies merge and collide. The difference is that they now see more details, which is very nice. But it is presented like it is the discovery of the century.