The Perseids

Philosophy Forums Science, Technology, and Math
1

The Perseids are a meteor shower/ shooting star thing, set to peak in activity in a few days (aug 11-12, 2013)

It has been described as tiny bits of space debris left over from Swift-Tuttle comet.

The description of the event is that when earth passes into the debris, the tiny bits light up from the friction of the earths atmosphere.

My question is this: when we see a shooting star, specifically in the Perseids, what is the relative motion of the debris/earth. IOW is the spin of the earth moving faster than the particle, or is the particle moving faster? To what degree is the movement of the fragment really a function of our shifting perspective?

Secondly how does earth get closer to the orbiting debris every year so as to cause entry?

Thanks

2

Those seem to be odd questions to be asking. For the last 100 years or so, Science has disavowed the existence of absolutes; absolute positions or absolute speeds (even zero). For some reason they didn’t bother to ask me or I would have explained differently, but as it is, your question isn’t making sense.

Movement in physics today is defined merely as relative motion. How fast each of two objects is moving is a non-sense question. The question (now) must be “how fast is each object moving relative to the other?” By ontological and political decree, there is no absolute measure to be asking about.

So to discover the only speed allowed to exist, one merely stands by the particle and measures how fast it passes by. I imagine those particles would be going several 10’s of thousands of miles per hour and very quickly decelerating.

The second question is a little puzzling as well. How does anything get closer to something else? I don’t understand what it is that you wouldn’t already instinctively know.

3

First of all, thanks for attempting to answer.

But wow, I did clearly say “relative motion” so I’m not sure what it is you are so stymied by. I find it odd that you are stymied, and odder still how enjoyable it is to use the word stymied. Stymied. Stymied. Stymied.

So anyway, I googled it and the answer is roughly 133,200 mph (60 kilometers per second) relative to the planet.

Secondly, what I understand is that a comet leaves a dust trail which sort of hangs out in the comets orbit…and in this case our Earth eventually migrates near this trail, and that’s how the particle, roughly the size of a grain of sand, leads to the “shooting star” appearance. I’m not sure if this dust trail just sits there unmoving, or if the particles drifts, and if so, at what speed; but it’s interesting that when it collides with our atmosphere (or more accurately, the atmosphere collides with it) the friction is the result of a 133,200 mph difference between the meteor and the atmosphere.

My question is/was, is the dust particle from the comet trail moving before it enters Earth’s atmosphere (sort of like we’d imagine an asteroid on a collision course) OR is the thing static and the resulting motion/speed really a function of the Earth’s fast rotation and revolving relative to the inert dust trail. I think for Earth we’re looking at 1,000 mph rotation and 10,000 mph revolving speed around sun.

If I can tell my kids (and be accurate) that it’s not the shooting star that’s moving, but rather, it is us that’s moving relative to the speck of dust happening to be in the path of our Earth. This would carry a great message about relative motion…and is just something kind of cool to point out, but I wanted to confirm here first with a science geek.

Some science geeks are nice like Neil Tyson, and some are finicky and surly when they collide with STYMIED (yee-haw!) amateurs wrestling with questions that might seem foolish. I find that the high level data collectors/technicians are the snarky impatient jerks. James, are you by any chance a data collector?

4

True, that 2nd question was pretty lame. But I’m curious about our orbital path compared to the comet trail’s, or if there was anything notable or interesting about it. If you don’t know, no biggie.

I definitely wasn’t asking how two objects get closer to each other in the event that they get closer to each other, I’d never ask something so absurd. Or if I did, I’d at least have the decency to ask it in the philosophy section.

5

:laughing:

Okay. Sorry for the confusion.

And the dust doesn’t slow down much until it hits the atmosphere. The space within the solar system is hardly empty, but even anything the size of a grain of sand traveling at 100k mph, would still have a hell of a lot of momentum. And I imagine that a lot of it isn’t that small. I doubt that the 10k additional Earth speed is the larger effect.

…snark… snark… snark. :stuck_out_tongue:

6

I’m thinking the earth speed might be the larger effect and here’s why. Earth revolves around the sun at some 66,000 miles per hour. Earth rotates at some 1,000 miles per hour. These are estimates. So if it lines up right, it’s possible that the combined speed of these two could exceed half of 132,000, so does it follow that the small majority of the velocity we see in the shooting star event from Perseid theoretically in some cases due to Earth speed? (Assuming the data is more or less accurate?) to know for sure I’d need to calculate the combined speeds of rotation and revolution at point of entry, and either add or subtract depending on speed and angle of debris relative to angle of earth velocities.

My point is that the speed of entry is variable and in part determined by earth speeds as earth collides into the debris spray. It’s possible that the speed of earth could be the bigger player in causing the friction in at least some cases.

7

Obviously to resolve it you are going to have to know the precise situation at the moment. Both the Earth’s orbit and spin might be either adding or subtracting from the effect. And remember that the Sun isn’t exactly standing still in space, so the initial claimed speeds have to be examined for reference and angle.