Nano

Haha. So funny. I haven't been visiting this site since forever. The only reason I was loggin on again was that I was thinking the exact same question as the thred-starter. Turns out he read my mind. If I understand it right, the answer to the question is: The universe has been, and is expanding with a velocity close\at (faster?) than the speed of light, relative to us. And that is why galaxies that were close to us in the past still uses 10Billion LY to reach us. The light doesn't quite "catch up" to the speed of the universes expansion, which has a direction the oposite way than that of the light. But one thing I don't get about this, is that c is fixed no matter how fast the observer is moving. Right? That means that the light on it's way to us must have had a constant speed at c, not dependent of if space around it is moving in oposite direction. Then how can the expansion of the universe have any influence on the lights' speed?

Great, thanks. Lots of help.

Thanks for answers. Is this right then? If I want to send an object of 1 kg to Mars, when the planet is the closest to the earth as possible: Ug = mgh 1kg x 9.8^2 m\s x 54,6 x 10^9 m = 5,2*10^12 Joules But this formula does not take into account that the gravitational field gets weaker the further away from the earth you go? Do I also have to think about that the sun is pulling this object (If I choose to send it toward Mars AWAY from the sun) What is the corresponding amount of Joules stored in 1 liter of jet-engine-fuel? And how much does 1 liter of fuel weigh?

Hello. Can someone help me with how to calculate how much energy (in joules) it would take to lift an object with a given mass and radius out of the earths gravitational field? I get the answer in m\s (escape velocity), but I need to know what correspond to that in energy. And I also wonder how to calculate how much fuel is needed to make an object escape the earth. Thanks.

Thanks for all the answers. But if the moon has lost it's rotation, isn't it to expect that also the earth will after a great time loose it's rotational speed due to the orbit around sun? Will then the earth's orbit be further away from the sun and it's speed be greater? In that case, another ice-age might occur. Bohr's solar-system model is obviously printed in my head, and I guess it gives not the right impression of an atom. What about these things?

I have been interested in science my whole life, but got no education, and I have therefore lots of questions I don't get to ask anyone. I try here with some of the questions I wonder about the most, and I hope you have the time to help me. First about the gravitational attraction between objects: Will an object in orbit gradually slow down its speed due to gravitation, and eventually hit the object which is pulling on it? For example the moon in its orbit around the earth. Has the moons speed been grater earlier in time? What keeps the electron in its orbit around the nucleus? There must be some kind of force pushing it forward, or else it would get sucked in by the electromagnetic attraction between positively and negatively charged particles. Why does the speed of light have the velocity it has? I know the photon is massless, but what “resistance” is stopping it from going faster in vacuum? I have heard that c is like a cosmological speed-limit, but why is there such a speed limit? Why will light always move at c towards you no matter how fast you are moving? And finally what dose c have to do with e=mc2 ? What is the connection between the rest-energy inside atoms, and the cosmological speed-limit? And why is it squared? Lots of stuff here.. You don't have to answer all