Gozzer101

I agree with your equation: [math] \frac{2x}{c-\frac{v^2}{c}}[/math] But if we consider the journey in the opposite direction then the equation is the same (if its both ways): we get to the moon: [math]T1 = \frac{x}{c-v}[/math] and back: [math]T2 = \frac{x}{c+v}[/math] Which solves to exactly the same equation that you posted: [math] \frac{2x}{c-\frac{v^2}{c}}[/math] If we consider only one way though then as your equations show they are different values: One way to the moon in direction X: [math]T1 = \frac{x}{c+v}[/math] One way to the moon opposite to X: [math]T2 = \frac{x}{c-v}[/math] So as I'm looking at it a round trip in either direction is the same, as the equations are opposite and solve to the same, but a single trip then the equations are different. So have tests been done like this in one direction only, and so not using mirrors/reflectors, just using a beam and a detector. Do we have any links to this? Or any extra info I could read up on to fully understand the concept. Thanks

I always under the impression we couldn't find out, we could only judge it in relation to another point, say we are moving at speed A to Galaxy 1 but at speed B to Galaxy 2 Consider a light beam (or a photon) being sent from Earth to a detector on the Moon. Our galaxy has to be moving and in some direction through the universe (or extremely likely to be) as others are coming towards us (andromeda) and others are moving away (not including the expansion of the universe where all distance galaxies appear to be moving away) I was thinking if we sent two light beams to a detector on the moon at opposite points on the earth then the time it would take to get their would change. Why? Because if we are moving in relation to the universe in the direction of X then if we sent the beam while the moon was parallel to Earth and directiom X then the distance the photon has to travel has increased: for example: the photon travels 100 m (for arguments sake we will say it takes 1 second to do this) towards the moon yet in relation to the universe the moon has travelled 5m further away (distance it travels in 1 second) from the original destination the photon was sent (not earth as this will be moving in the same direction and speed, so a point in space) If we sent the beam from the opposite side of the earth then the distance it has to travel to the detector will decrease and so it should arrive quicker, even though light hasn't travelled any quicker it just appears to (for every 100m the photon travels, the moon gets 5m closer) My question: Using many points to send a beam and using calculations could we then determine what direction and speed we are travelling through the universe? Please don't confuse the beam being sent to the moon and us measuring the time it takes for it to appear on the moon (or for it to be reflected back to us) as this would cancel out the affect. Why? Because on the return journey, say use are moving in direction X then on the return journey (moon to earth) it would be quicker as the distance it has to travel has decreased. If my reckoning is wrong then please tell me why?

Don't they use a method of finding planets outside our solar system using this method? They detect stars with a tell tale "wobble" which are in fact orbiting the solar systems centre if mass.

As I have learnt it's very difficult to be a stationary observer in space. However we often talk about speeds of certain objects. For example: The Earth rotates at 1600 km/hour The Earth rotates the Sun at around 107000 km/h The Sun/Solar system moves in a patch of stars at around 70000km/h We orbit the Centre of the milkyway at around 792000 km/h We are moving as part of a cluster of galaxies at around 2000000 km/h Although all these speeds are in different directions it still has to be a "speed" We measure light to be a speed of 670000000 km/h As the law of physics if something speeds up, time slows down. That is why light is the speed limit of our universe. Does this mean then there are other galaxies who's time is different to ours? As some will be moving slower and some faster. Another question: if we are moving then in certain directions, shouldn't light appear quicker in one direction than others? Say we are moving to point x (1 mil light years away) at 2000000 km/h then the light would have to travel a lesser distance and ultimately in a quicker time to that in the opposite direction? Finally knowing all these different speeds. If we set off at a high speed in one direction relative to us would we not need to achieve light speed to actually get light speed: as we are already moving in that way anyway, say 5000000 km /h, then we would only need to achieve 670000000 minus 5000000?

I once read that the expansion of the universe is the only thing that is faster than light (although it's not technically a speed?). It was in a BBC focus magazine. By my reckoning because of this, distance objects light will never reach Earth. Yet stories come up in the news of far fethced galaxies seen from earth and some quasars too? If this is true then does anyone know what point we can see back too before light will no longer reach us, and at this point what would we see if say a galaxy was at this exact distance from earth. Would the light from it stay the same? Or would the apparent galaxy time perspective from earth speed up?

Good answers thanks

Okay. So as a stationary observer in Space. If we were to launch a Rocket off Mercury it would be travelling at around 50km/sec (plus the extra negligible speed of the rocket to exit the surface of Mercury). At around 50km/sec that works out to 180000km/hour or 4320000km/day. Assuming that to reach orbital path of the furtherest planet in the solar system, Neptune (4.45billion km away from Mecury?), it would take 1028 days. I know that is far too quick of a rocket (e.g. Voyager). I take into account that the rocket wont follow the direct path from Mercury to Neptune, but it wont be too much of a change? Is that correct? EDIT: Voyager 1 travels at around 13km/sec far slower than the orbital speed of the Earth (29km/sec). I assume it has used the gravity sling shot method of planets to propel it further out and to gain speed. But 13km.sec is still slower than the Earth rotation speed around the sun... The only thing I can think of is when exiting Earth, the gravity of Earth will slow it down? As once free from the gravity of Earth it will never lose speed (assuming no other things collide or any other gravity forces act on it)

Hi Might sound a silly question, but I've asked a couple of people who are unsure: I read that Mecury races around the sun at around 50km a second. I also know Mercury has very long days (time it takes to spin on its axis). Knowing this I thought what would happen if a rocket was launched off the surface of Mecury (theoretically) on the side of the planet of the direction of it's orbit around the sun (Side A) against that to a rocket lifting off on the side opposite to it's suns orbital direction (Side B). To me it comes to the conclusion that to exit Mercury on side A then the rocket, when free from Mecruys gravity, had to be travelling at over 50km/sec. Else Mercury would "catch up" with the rocket bearing in mind it's on a similar sort of path as Mercury. I was thinking it would be a similar situation to that off throwing a ball off a train (to person on train ball doesn't appear to go any faster than a throw while still, but to an outside observer they can see the ball travels faster). If someone could explain this to me it would be brilliant. And say where I have gone wrong in my assumptions etc. Also hope my question makes sense! If not I'll try to rephrase it in more detail. Thanks