Does the Earth orbit around where the Sun was 8.5 mins ago?

[sheeny (Al)]

Originally Posted by xelasnave

I cant find the times but I think Neptune is about 4 light hours from the Sun. On my initial approach it should orbit a point where the Sun was 4 hours ago. How far does the Sun travel along (or move along its orbital path therein) the spiral arm in 4 hours? There should be that lag but then I gather there is the effect of whatever the Sun is being influenced by also acting to pull/push the planets to it, which would negate the forming of a cone shape. But whatever is acting on the Sun will act less on the planets by reason of mass differences and how that plays a part in gravitation so from that point there may be a flater cone???. I think I will go back to drinking it all seemed so much clearer then .
alex

Ah! Alex...

Remember when Galileo proved that bodies of different mass fall at exactly the same rate of acceleration? He did that by dropping things off the leaning tower of Piza. Also Newton's law of gravitation: the force is proportional to the mass, and so is the acceleration... so all objects regardless of mass accelerate at the same rate in a uniform graviational field (which we can assume because the distance to the galaxy centre is so large).

Secondly the acceleration is towards the centre of the galaxy, which is a rightangles to the direction of motion of the solar system around the galaxy. (assuming uniform circular motion). So there is no force pulling the sun in the direction of motion - it is all purely momentum. No forces involved in that direction...

and no smoke and mirrors either!

Any clearer?

Al.

[xelasnave]

Thanks Al indeed it is. I have just been to a site which asked in what direction one would have to pull the string attached to a ball if one wished to have the ball orbit .. so your advice is timely and has been well received. Thank you.
alex

[xelasnave]

Here is a diagram of the Solar System moving from right to left of page I gather. Given our discussion and conclusion I thought it strange "they" see a bow wave how can we interpret this.. it seems that there would not be a shock wave as one would think all the surrounding space makes up the ball at the end of the string, everything should be travelling at similar speed as you observed.
I wonder if the shock wave has been detected or is it an expectation? Sorry I find it fascinating.
alex

[sheeny (Al)]

G'Day Alex,

That's all to do with the solar wind... the stream of particles emitted from the sun along with light. At the heliopause, the outward pressure of the solar wind is matched by the pressure of gas in the neighbouring space, so the solar wind basically stops.

The heliopause is egg shaped because of the motion of the sun - less distance to the heliopause looking out "the front" due to "velocity pressure". Not sure if velocity pressure is a scientific term or not, but it's a term we use in engineering to measure the velocity of a gas or air using a pitot tube. The total pressure = static pressure + velocity pressure. So in front of the solar system the total pressure is high (equals static pressure of space + velocity pressure of solar system), to the side it is moderate (total pressure = static pressure of space = static pressure of solar wind i.e. velocity pressure has not effect) and behind the solar system the total pressure is less (equals static pressure of space minus velocity pressure of solar wind - because velocity is a vector! ).

I wasn't aware the heliopause was egg shaped!

Al.

[xelasnave]

I dont understand space time that well yet but I think its approach demands an egg shape for something moving. I dont know how many frames to say that as I dont understand how to bring time into it yet.. no worries. My point with the space craft leaving this "bubble" I made elsewhere in these forums was that they would in effect get stuck in the "stickyness" of space time... not very scientific.. when they left the bubble (on the presumption there would also be a sort of cut off point where the gravity of space would over take over the gravity of the solar system)...but after the ball on the string thinking I am not sure.
I believe gravity "pushes" and is a form of pressure somehow deriving from "star light" and all we find in it, not sure what bit yet,.. so morosophically I tend to try and see if that approach fits things I see. Runing into gases in space implies there is more there than even I thought. As you probably gathered by now law was not a good choice of careers... or maybe it was Thanks for taking the time maybe you should have been a teacher on second thoughts..I am not a good student.
alex