Stellar Oscillations across Spiral Arms

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Larry Burford</i>
<br />[to Jim]: "Relative to the sun a slow moving comet will gain speed and a fast moving comet will gain speed, but the speed gained by the fast moving comet will be less than the speed gained by the slow moving comet."<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Right. And to be quantitative, as in my July 2 message, "zero-initial-velocity comets are traveling at 42 km/s by the time they reach the vicinity of Earth’s orbit, whereas a typical interstellar comet [starting at 25 km/s] would have a speed of 49 km/s near Earth's orbit." -|Tom|-

Jim,

There is a different relative speed measurement that can be used to get closer to your particular wording. "Relative to the slow comet falling in the sun's gravity, the fast comet falling in the sun's gravity will slow down."

Using tvf's data you can see that when the two comets begin falling the difference in speed is about 25 km/sec. But by the time both have fallen to about 1 AU from the sun the speed difference (relative speed) has fallen to 7 km/sec.

But referencing one comet to the other is very different from referencing both comets to the sun.

LB

The example TVF is using(comet speed 25,000m/s or zerom/s) is a huge spred don't you think? In the real world comets would enter the solar gravity field somewhere between those extremes. Are you going to rewrite this in better grammer than I can generate? I want to see how you would say this since you understand me while I don't understand what you are trying to tell me.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Jim</i>
<br />The example TVF is using(comet speed 25,000m/s or zerom/s) is a huge spred don't you think?
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Relative to speeds we encounter in our day-to-day activities: yes, it is enormous.
Relative to speeds that are possible and likely "out there": no, it's actually kind of small.

Overall, I'd have to say the "no"s overpower the "yes"s.
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">
In the real world comets would enter the solar gravity field somewhere between those extremes.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
No. Objects entering the solar gravity field (including comets, if any) do so with an average speed of 25 km/sec.

Many are faster.
Many are slower.
The average is 25 km/sec.
<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">
Are you going to rewrite this in better grammer than I can generate? I want to see how you would say this since you understand me while I don't understand what you are trying to tell me.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
???

I thought I already did. You will have to be more explicit about what you want.

I don't agree at all that average speed of an interstellar comet is 25,000m/s. The average speed of an interstellar particle must be the same as the average speed of stars in the galaxy and relative to the sun that would be zero. If that is wrong then what keeps the sun safe from most of the stuff in interstellar space? If stuff was flying around at an average speed of 25,000m/s relative to the sun there would be a huge number of crashes with all the solar masses.

[Jim] "If that is wrong ... "

(it is)

[Jim] " ... then what keeps the sun safe from most of the stuff in interstellar space?"

Luck. (Probability, to be more technical.)

[Jim] "If stuff was flying around at an average speed of 25,000m/s relative to the sun there would be a huge number of crashes with all the solar masses."

Wow. You have a very strange mental image of how close things are to each other out there.

LB