11 Jun '08 19:59>
how fast are we travelling given our speed of rotation around the sun + the movement through space of the solar system + the big bang effect etc etc ?
Originally posted by MattPSounds to me like your over-analyzing this. Since we are approximately 93 million miles away from the sun (a radius), can't we use that to figure out our orbit's length (I know it's elliptical, not circular; I'm just saying we CAN approximate fairly easily) using 2 pi r squared? Then divide that by 365.25 x 24 (the number of hours in a year) and voila! We have the (very approximated) speed of the earth through space!
Relative to what? All motion is relative, however, in our normal day to day life we measure all speeds relative to a common frame of reference (the Earth's surface / in the rotating frame of the Earth , or however you care to describe it).
Anyway, my point is you need to specify the relative motion between two frames, there is no such thing as an absolute speed.
Originally posted by eamon oHow fast we're going through the universe, does that mean speed? We should use velocity.
how fast are we travelling given our speed of rotation around the sun + the movement through space of the solar system + the big bang effect etc etc ?
Originally posted by FabianFnasI agree with your analysis, though it might not infact be true that the velocity of our super cluster relative to other super clusters is greater than that of the local cluster relative to the super cluster.
But you will also notice that the speed will increase from (1) to (5) so what happens here on Earth is miniscule compared to what happen in galactic space. So the velocity of the velocity of our galactic super cluster through the universe is prominent. If you don't know this value, you actually don't know anything.
Originally posted by FabianFnasThanks, I take your point about velocity, but I dont agree that to calculate how fast we are travelling is pointless. It is about getting at the truth. I find the concept that we are travelling fast through space very interesting and it would be good to have a number for it. I heard a british female scientist on the radio some months ago giving an approximation of it but I didnt write it down. I guess that many of these vectors need to be factored-in when we plan the trajectory for a space craft on an interplanetary trip. The concept of multiple motion and speed is interesting partly because much of what is really going on is undetectible to our senses, that is why for me the truth of it becomes more intriguing.
How fast we're going through the universe, does that mean speed? We should use velocity.
Velocity is a vector, both speed and direction should be accounted for. We can't add speed together because certain speeds cancel out each other if the go in opposite direction.
Think of what will happen if you go through a slow train. If you go 10 km/h back in tr ...[text shortened]... nything.
So to calculate "how fast we're travelling" is more or less pointless.
Originally posted by eamon oBecause it is all relative, for an interplanetary trip we only need to know our velocity relative to the solar system (sun) and the relative veolcities of whichever planets we are aiming for. The velocity of the solar system through the galaxy is irrelevant.
Thanks, I take your point about velocity, but I dont agree that to calculate how fast we are travelling is pointless. It is about getting at the truth. I find the concept that we are travelling fast through space very interesting and it would be good to have a number for it. I heard a british female scientist on the radio some months ago giving an approxi ...[text shortened]... ng on is undetectible to our senses, that is why for me the truth of it becomes more intriguing.
Originally posted by twhiteheadi think thats ok provided the velocities we are factoring are in 3d and take account of rotation, orbit and expansion etc.
Because it is all relative, for an interplanetary trip we only need to know our velocity relative to the solar system (sun) and the relative veolcities of whichever planets we are aiming for. The velocity of the solar system through the galaxy is irrelevant.
We could even ignore our velocity relative to the solar system and just deal with our velocity re ...[text shortened]... ty relative to us and the velocity of the galaxy relative to other galaxies would be irrelevant.
Originally posted by eamon oI don't think the expansion of the entire universe has to do with local velocities. There is no center in the universe that you can see as some kind of a zero point. Or you can see any point of the universe as being the center, even our own position.
i think thats ok provided the velocities we are factoring are in 3d and take account of rotation, orbit and expansion etc.
if you had to pre programme a journey with 100% accuracy you would need to take into account tiny influences like the interplay of minute gravitational effects, the big bang expansion, solar rain etc
Originally posted by FabianFnasdepends on the degree of accuracy you are aiming at. i reckon you need to take a hypothetical fixed point to calculate everything accurately
I don't think the expansion of the entire universe has to do with local velocities. There is no center in the universe that you can see as some kind of a zero point. Or you can see any point of the universe as being the center, even our own position.
Originally posted by eamon oDepending on what universe center point you chose, you get different velocity due to universe expansion. So the center of universe is not a good idea.
depends on the degree of accuracy you are aiming at. i reckon you need to take a hypothetical fixed point to calculate everything accurately
Originally posted by dizzyfingersThat may compute the velocity of the Earth around the sun, but that does not take into account of 1) the velocity of the solar system around the Milky Way, which you can compute easily enough, we are about 30,000 LY from the center of the galaxy, and one rev takes about 100,000,000 years. Then there is the velocity of Andromeda and the Milky Way collision and then there is the general velocity of both Andromeda and the Milky Way towards the Virgo Cluster (I think thats the cluster we are crashing into). Around the Milky Way, roughly 100,000 Ly journey in 100,000,000 years= about 1000 years per ly which would be about 186 miles per second or so.
Sounds to me like your over-analyzing this. Since we are approximately 93 million miles away from the sun (a radius), can't we use that to figure out our orbit's length (I know it's elliptical, not circular; I'm just saying we CAN approximate fairly easily) using 2 pi r squared? Then divide that by 365.25 x 24 (the number of hours in a year) and voila! We have the (very approximated) speed of the earth through space!