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### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 5:44 pm UTC
snowyowl wrote:
rmsgrey wrote:Of course, at sufficiently high speeds (.9c may well not be high enough) the relativistic baseball simply isn't around long enough to dump enough energy to cause a problem - most of the energy ends up carried into deep space rather than forming a mushroom cloud in the stadium. Sure, individual atoms in the way get shredded, but surely there just isn't time for much of the energy to get dumped into the surroundings...

You'd need there to be enough mass in the way to drop the ball's speed down to around the (local) speed of sound for energy to bleed off significantly - an air-atom colliding with a ball-atom will give two atoms still traveling at nearly half the speed of light in the ball's original direction - you need to slow down a lot before any lateral component of motion becomes significant.

Yes, I think the ball will easily escape the Earth's gravity and carry off most of its kinetic energy into deep space. But the X-rays thrown off by the nuclear reactions will still be very impressive, and I'd expect air molecules just close enough to the ball to be pulled along in its slipstream but not close enough to actually hit it would dump most of their energy into the environment. There would definitely be a sizeable explosion.

Taking the conversation in a new direction: Isaac Asimov wrote a short story where a journalist recalls the tale of a man who was killed by his rival using an anti-gravity machine and a trick shot on a pool table. Because the pool ball was free of gravity, ALL gravity, it was able to accelerate to near-c and punched straight through the man's chest (instead of floating from the table gently) before heading out into space (if memory of the story serves me correctly).

I'm guessing the journalist wouldn't be talking to anyone that witnessed was present for the incident.

It also gives us a device that can get the baseball up to speed.

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 6:08 pm UTC
gmalivuk wrote:And note that this is not the right forum, and also I will lock any thread you try to start in Mathematics about your crank notions of coordinate transforms.

So I can start my own thread, but nobody can post to it, as you, gmalivuk, have the power to "lock it"...um, deny my right to post a new topic that you disagree with.

No need to find out which forum, as you will likely lock wherever forum I pick as appropriate.

So, a will not choose the option to start a new topic, to simply be locked out.

I tire of the unique rules and protocol here at xkcd.

i have presented a final proof on the "Pressures"thread, and no mathematical comment yet, other than, the usual "you are wrong". So, seems there is no interest in a drop of what I have to say, except football helmets.

So, there is nothing else to do, but stop posting to all threads at xkcd. So be it. NO need to read what gets posted in the future to that , and sadly, no desire now, to read what I might have not seen/not read missed. I can only imagine it likely just more premised denied logic aimed at me, in the 1500 posts to that thread.

I will not be returning to xkcd threads to post any math or physics stuff or what if? conjecture again. I may only be reached by my site henceforth.

.

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 6:16 pm UTC
steve waterman wrote:I will not be returning to xkcd threads to post any math or physics stuff or what if? conjecture again. I may only be reached by my site henceforth.

I'm conflicted. On the one hand, it's sad to see people withdraw expertise wholesale.

On the other hand: it's a phpBB for a web comic, man.

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 6:23 pm UTC
Do we not have any unmoderated forum for random crankage? Several other forums I read have a policy of, rather than locking threads, moving them into a sort of garbage subforum if they are not appropriate for any other subforum.

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 7:03 pm UTC
Jackpot777 wrote:
steve waterman wrote:I will not be returning to xkcd threads to post any math or physics stuff or what if? conjecture again. I may only be reached by my site henceforth.

I'm conflicted. On the one hand, it's sad to see people withdraw expertise wholesale.
You have no reason to be sad.

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 7:03 pm UTC
Jackpot777 wrote:Taking the conversation in a new direction: Isaac Asimov wrote a short story where a journalist recalls the tale of a man who was killed by his rival using an anti-gravity machine and a trick shot on a pool table. Because the pool ball was free of gravity, ALL gravity, it was able to accelerate to near-c and punched straight through the man's chest (instead of floating from the table gently) before heading out into space (if memory of the story serves me correctly).

I'm guessing the journalist wouldn't be talking to anyone that witnessed was present for the incident.

It also gives us a device that can get the baseball up to speed.

In the story, anything entering the field became a massless particle, so instantly went >spang< at light-speed. Of course, the story conveniently overlooks the point that the ball, being made of multiple particles held together by lowly electromagnetic forces, would, rather than rolling into the field and then vanishing, have disintegrated as it entered the field, forming a beam of high-energy particles, and disintegrating a hole through the victim as he collapsed rather than punching a neat hole through his chest...

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 7:10 pm UTC
capefeather wrote:Somehow I doubt that this was *quite* the kind of answer Ellen McManis expected. Perhaps the situation was supposed to be in a vacuum, or the batter was supposed to be "invincible" enough to hit the ball no matter what. Either assumption would probably lead to equally spectacular results, though.
Well, if he swings the bat (in vacuum, suppose), so the part hitting the ball is also moving at .9c, their velocities relative to each other (i.e. each in the other's frame) would be 99.45%c, which makes the kinetic energy of each bit increase to about 8.5 times its rest mass. This is 26.5mt instead of "merely" 4.

Pfhorrest wrote:Do we not have any unmoderated forum for random crankage? Several other forums I read have a policy of, rather than locking threads, moving them into a sort of garbage subforum if they are not appropriate for any other subforum.
There's FaiD. Good luck explaining to Steve how to find it, though, given how much trouble he evidently has with other parts of the forum.

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 8:02 pm UTC
Ugh, I'm not reading 40 pages of back-and-forth to see the context... but I did, I think, see it in the first couple and last couple. Yeah, the thing to worry about here is that he'll continue to take his pretentious attitude claiming to have disproved Galilean relativity (when really he just moved points with coordinate systems when you're not supposed to) elsewhere. And it will always be his audience's fault for dismissing his logic. Also it's pretty clear that he hasn't actually done his homework on how EM works <.<

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 8:23 pm UTC
steve waterman wrote:Instead of a particle or a wave, I wonder if a cluster of spheres might help explain the double-slit experiment.
I wonder, have we ever tried a triangle, a square, a pentagon, or hexagon of holes...what their patterns would be?

Here's a diffraction pattern from having one single hexagonal hole.
http://www1.union.edu/newmanj/Physics10 ... action.JPG

Here's a diffraction pattern from one single square hole.
http://4.bp.blogspot.com/_g3mLW-twYGc/R ... action.jpg

Here is a diffraction pattern from two slits in the shape of a cross.
http://hyperphysics.phy-astr.gsu.edu/hb ... li.html#c1

Another cross-slit pattern.
http://hasylab.desy.de/images/content/e ... hr_ger.jpg

This one is from a diffraction grating. I'm reasonably sure that it was a grating in two dimensions, so it was equivalent to a whole lot of square holes in a square pattern.
http://www.sciencephoto.com/media/2940/enlarge

I doubt you will get very far with this approach. The math for what diffraction patterns to expect seems to be pretty well worked out. Simulations predict the diffraction patterns just fine, with no particular surprises.

What doesn't work as well is the meanings. Diffraction patterns are completely compatible with waves, so people figured that light was made of waves. But it turned out that when light interacts with matter, often the matter absorbs or emits only quantized amounts of light. Since matter often emits quanta of light, and often absorbs quanta of light, it makes sense to suppose that light is always in specific photons. (I don't think this is true for radio waves from a radio antenna. Every electron that moves up and down the antenna can keep moving up and down for any amount of time, producing any desired length of wave itself. Higher voltage can make it move more, lower voltage and it moves less at the same frequency. But put that aside, light is always in photons, and for a given wavelength each photon always has the same energy.)

Light waves work this way -- the wave travels in straight lines in every direction, and the waves add or subtract to give a combined intensity at each point. Light particles work this way -- each particle travels in straight lines in every direction, and the particle coming from different directions adds and subtracts with itself to give a combined probability that it will show up at each point.

There is no guarantee that light travels as waves, it's just that light travel is completely consistent with waves. Anything else that acts exactly like a wave might fit just as well. There is similarly no guarantee that light travels as particles which move exactly like waves. It's just a way to fit together the observed wave-like motion with the observed fact that atoms and molecules usually interact with quanta of light. Whatever is actually going on must fit the math that works, but it's hard to see what could fit that math.

So if you could come up with an idea that made sense and fit the observations, that would be a good thing. It wouldn't directly matter to physics because it would only explain behaviors which are already known and well-measured. But it could be a big relief to physics students, and particularly to people who are required to take physics courses and want it to make sense.

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 8:30 pm UTC
As I noted when I first got here, I went over this with him in great detail 4 years ago on the wbabin boards, as have many others, and no, he will never admit anything besides "they're just trying to censor me for being right about Einstein".

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 10:37 pm UTC
Anyhow, does anyone know how we'd figure out the cross section of the atoms and/or subatomic particles of the baseball at a relative velocity of 0.9c?

Then again, even with relatively few collisions, the secondary products will collide a bunch more, which will make that first-order approximation pretty inaccurate.

### Re: What-If 0001: Relativistic Baseball

Posted: Fri Jul 13, 2012 11:00 pm UTC
iamspen wrote:Interestingly, if one reads the rule and determines the pitched ball is a strike (it, IMO), the the batter cannot strike out in this situation if the count is x-2, because some of the superheated baseball junk will presumably make contact with the bat. Thus, unless the catcher manages to catch the baseball particles before being wiped from existence, even if the parts of the pall pass through the strike zone, it would be considered a foul ball.

If the ball somehow misses the bat while first base is unoccupied and/or there are two outs, the batter will become a runner due to the uncaught third strike. Though he probably won't get very far.

### Re: What-If 0001: Relativistic Baseball

Posted: Sat Jul 14, 2012 1:06 am UTC
It is most appropriate to view this collision as between a group of moving nuclei and, in collider lingo, "fixed target" nuclei, of similar composition (nitrogen, oxygen, carbon). The chemical bonds are irrelevant; the electrons have much less energy. For analysis purposes, let us go into the center of mass frame.

In this frame, we have colliding nuclei of roughly equal mass and thus momentum, moving at roughly .48 c each (by the weirdness of relativistic velocity addition). Taking oxygen as representative, we have a center of mass collision energy of about 34 GeV, about 1 GeV per nucleon (compare to the LHC's 574 TeV for lead, a little less than 3 TeV per nucleon). The collisions here are energetically comparable to those of SLAC.

At these energies, the nuclear binding energies, on the MeV scale, are utterly irrelevant. Really, we're colliding protons and neutrons together. Total fission will definitely occur, but at negligible energy cost (at most hundredths of a GeV, in a GeV collision).

Essentially, the protons and neutrons will collide inelastically or just pass right through, producing highly forward (when we transform back into the Earth frame) QCD jets, and radiating enormous amounts of gluons besides. This energy will eventually become heat when the light decay products are stopped by the backstop, producing an explosion on the thermonuclear scale. The ball remnant will escape the Earth, leaving a trail of fire through the atmosphere, since the probability of an atmosphere nucleus being in the ~10^-25 cm^2 cross section for inelastic scattering to occur with any given nucleus in the ball is small (coulomb scattering is not relevant at these speeds; they don't even notice each other).

### Re: What-If 0001: Relativistic Baseball

Posted: Sun Jul 15, 2012 12:06 pm UTC
The really interesting question is if there happened to be an ant on the baseball how much time would pass for him before destruction.

### Re: What-If 0001: Relativistic Baseball

Posted: Sun Jul 15, 2012 6:13 pm UTC
This is a really interesting thought experiment, thus motivating my first post on this forum.

By my calculations, the cross section for nucleus-nucleus interaction is too small for the development of the "fusion zone" Randall describes. I get a mean free path of 10 to 20 cm. Also, the baseball encounters less nuclei on its way through the air than there are nuclei in the baseball. So only a fraction of the nuclei in the baseball will have undergone any change when they reach the batter.

But I think the baseball will have largely disintegrated by then, because an air molecule will deposit energy in the baseball while passing through it. When you think of it in the reference frame of the baseball, then the baseball is the target and gets hit by nitrogen (and other) molecules with an energy of 2.3 GeV per nucleon. I guess that, due to electron-electron interactions, there is a good chance for the molecule to break up on its way and for the nitrogen atoms to get ionized. Now, for bare nitrogen nuclei, I get a stopping power in the range of 100 MeV/cm in something that might be a baseball by the Bethe-Bloch formula.

By a sequence of crude calculations, I guess that most nuclei of the baseball will be ionized and spread out in the range of 1m when they reach the batter. Approximately by the same time, the batter will be reached by a wave of radiation and hadrons from nucleus-nucleus collisions (those particles will be concentrated along the axis of flight because of relativistic effects). Now those nuclei and hadrons will create a major impact when they hit the batter or any other obstacle …

As this is guesswork, I might be wrong on any number of points. Anyhow, the result is the same: a huge crater and a mushroom cloud.

### Re: What-If 0001: Relativistic Baseball

Posted: Mon Jul 16, 2012 2:51 am UTC
Yeah, relativistic beaming needs to be accounted for.

The ravioli as a gas link is the best examination I can find.

Thinking about it, at 0.9 c wouldn't the baseball be contracted by over half it's size in the direction of motion, viewed from the batters frame? Naturally from the ball frame everything else would be contracted.

### Re: What-If 0001: Relativistic Baseball

Posted: Mon Jul 16, 2012 4:31 am UTC
rmsgrey wrote:
Jackpot777 wrote:Taking the conversation in a new direction: Isaac Asimov wrote a short story where a journalist recalls the tale of a man who was killed by his rival using an anti-gravity machine and a trick shot on a pool table. Because the pool ball was free of gravity, ALL gravity, it was able to accelerate to near-c and punched straight through the man's chest (instead of floating from the table gently) before heading out into space (if memory of the story serves me correctly).

I'm guessing the journalist wouldn't be talking to anyone that witnessed was present for the incident.

It also gives us a device that can get the baseball up to speed.

In the story, anything entering the field became a massless particle, so instantly went >spang< at light-speed. Of course, the story conveniently overlooks the point that the ball, being made of multiple particles held together by lowly electromagnetic forces, would, rather than rolling into the field and then vanishing, have disintegrated as it entered the field, forming a beam of high-energy particles, and disintegrating a hole through the victim as he collapsed rather than punching a neat hole through his chest...

I always thought that the physicist who created the machine misunderstood what it actually did. I think he expected the ball to simply defy the obvious presence of Earth gravity, and that once the ball went into the machine, it would linger in the air and not fall down. But, as I understood it, the machine actually removed all of the ball's momentum so that it was "at rest," and the other physicist somehow calculated the rotation of the Earth around the Sun around the Milky Way and timed his shot perfectly so that the ball was right in the middle of the inventor's cosmic trajectory.

When I first read the story, that's what I thought happened. But in hindsight, the idea of relativity and a lack of rigid cosmic background destroy any idea of "at rest." So unless Asimov wasn't up to date on his modern physics, I think I need to reread the story.

### Re: What-If 0001: Relativistic Baseball

Posted: Mon Jul 16, 2012 4:39 am UTC
He most definitely lined it up based on the idea that it would continue on the same trajectory at relativistic velocities.

He (Priss) asked if it was a coincidence that the planet might have been lined up or something notes that there can be no absolute rest state, that the earth/sun/galaxy are all in motion, but thinking about it later the narrator points out that from what he can tell it should have been obvious that the ball would do what it did, and when he watched the video he noticed that Priss lined the shot up dead center with Bloom's heart.

Asimov wrote:I keep thinking. Photons smash out from a light source in all directions because they are created at the moment and there is no reason for them to move in one direction more than in another. Air molecules come out of a zero-gravity field in all directions because they enter it in all directions.

But what about a single billiard ball, entering a zero-gravity field from one particular direction? Does it come out in the same direction or in any direction?

I've inquired delicately, but theoretical physicists don't seem to be sure, and I can find no record that

Bloom Enterprises. which is the only organization working with zero-gravity fields, has ever experimented in the matter. Someone at the organization once told me that the uncertainty principle guarantees the random emersion of an object entering in any direction But then why don't they try the experiment?

Could it be, then…

Could it be that for once Priss's mind had been working quickly? Could it be that, under the pressure of what Bloom was trying to do to him, Priss had suddenly seen everything? He had been studying the radiation surrounding the zero-gravity volume. He might have realized its cause and been certain of the speed-of-light motion of anything entering the volume. Why, then, had he said nothing?

One thing is certain. Nothing Priss would do at the billiard table could be accidental. He was an expert and the billiard ball did exactly what he wanted it to. I was standing right there. I saw him look at Bloom and then at the table as though he were judging angles.

I watched him hit that ball. I watched it bounce off the side of the table and move into the zero-gravity volume, heading in one particular direction.

For when Priss sent that ball toward the zero-gravity volume-and the tri-di films bear me out-it was already aimed directly at Bloom's heart! Accident? Coincidence?

…Murder?

### Re: What-If 0001: Relativistic Baseball

Posted: Mon Jul 16, 2012 5:52 am UTC
Jackpot777 wrote:Taking the conversation in a new direction: Isaac Asimov wrote a short story where a journalist recalls the tale of a man who was killed by his rival using an anti-gravity machine and a trick shot on a pool table. Because the pool ball was free of gravity, ALL gravity, it was able to accelerate to near-c and punched straight through the man's chest (instead of floating from the table gently) before heading out into space (if memory of the story serves me correctly).

I guess he's exploiting Mach's theory of inertia: that the inertia of a body is caused by its gravitational interaction with all other mass in the universe. So if you make the pool ball free of ALL gravity, it will have zero inertial mass, and thus any non-zero force applied to it will give it unlimited acceleration.

See http://en.wikipedia.org/wiki/Mach%27s_principle.

### Re: What-If 0001: Relativistic Baseball

Posted: Mon Jul 16, 2012 7:12 am UTC
Nah, he explained that "any body with zero mass is constrained to move as all massless bodies do, at light speed" in the story.

I brought that up in reference to a superpower in a pen and paper rpg, pointed out that if I could really generate a region where objects had zero mass, you just gave a relativistic machinegun to ME... bad idea!

### Re: What-If 0001: Relativistic Baseball

Posted: Mon Jul 16, 2012 11:52 am UTC
steve waterman wrote:I will not be returning to xkcd threads to post any math or physics stuff or what if? conjecture again. I may only be reached by my site henceforth.

I'm going to miss the photographs of models to explain concepts. I have no idea if Mr Waterman made them.

I fell in the love with the idea Mr Waterman was at home, sat on the floor covered in glue and cellotape, making models to photograph to put forward his ideas.

If more arguments were carried out through the use of modelmaking, the world might be a better place. There's more time to think things through, and we'd have lots of models to play with.

### Re: What-If 0001: Relativistic Baseball

Posted: Mon Jul 16, 2012 1:07 pm UTC
The Moomin wrote:
steve waterman wrote:I will not be returning to xkcd threads to post any math or physics stuff or what if? conjecture again. I may only be reached by my site henceforth.

I'm going to miss the photographs of models to explain concepts. I have no idea if Mr Waterman made them.

I fell in the love with the idea Mr Waterman was at home, sat on the floor covered in glue and cellotape, making models to photograph to put forward his ideas.

If more arguments were carried out through the use of modelmaking, the world might be a better place. There's more time to think things through, and we'd have lots of models to play with.

Oh the rofls I just had at that image, and yes, I'm pretty sure Steve is making them on the fly.

### Re: What-If 0001: Relativistic Baseball

Posted: Mon Jul 16, 2012 2:23 pm UTC
Max™ wrote:
The Moomin wrote:
steve waterman wrote:I will not be returning to xkcd threads to post any math or physics stuff or what if? conjecture again. I may only be reached by my site henceforth.

I'm going to miss the photographs of models to explain concepts. I have no idea if Mr Waterman made them.

I fell in the love with the idea Mr Waterman was at home, sat on the floor covered in glue and cellotape, making models to photograph to put forward his ideas.

If more arguments were carried out through the use of modelmaking, the world might be a better place. There's more time to think things through, and we'd have lots of models to play with.

Oh the rofls I just had at that image, and yes, I'm pretty sure Steve is making them on the fly.

The dude image is quite real and was as i said it was. It as not doctored, nor was the text, nor did a lie about my Nephew Scott not being aware of the xkcd thread, if that was what was being implied.

The red and blue grids are pieces of Zome Tool, and I had taken some pictures of years ago. I modified those, in Photoshop to apply to the discussion.

I was saying, that my "Appeals to" observation was from my point of view. Let the record and xkcd picture posting speak for themselves

As requested before, my name is Steve and I find those people that instead elect to call me Mr. Waterman, to be placing me at arm's length.

i no longer wish to present material via a comic thread. Ii have a place for my silliness now.
I have a chance through xkcd via the new What If ANSWER on Tuesdays.

What if Randall never uses a single one of yours ?

So be it. I trust in Randall's brain power and comic sense. He may elect to indeed find others what if ? more pertinent. I wanted a way to reach Randall, and now it has appeared, virtually out of thin air. It makes no sense now, to lurk on a few threads simply defending myself with more pages of the same.

I will say this again. While it was a tad rough at times, I had quite anticipated that. I saw this as a collaboration, you saw this as a lynching, which was also 100 percent anticipated. With your kind but not always respectful help, I/we whittled down; no depictions, no waterman terms or concepts, only given the Galilean given. i would not have done this on my own, many thanks for the great help.

Randall and I are now locked into our seats on the roller coaster ride, I do so hope. I have personally glued all the pieces to the board. I hope we take a ride together.

I have waited twenty years. I hope to see a related what if? at xkcd in the next year or so, it would be yet another life treasures to treasure.

I hold no one any ill will or any crap like that here at xkcd, rather the opposte. I am glad that I was locked out and felt it was class to not delete my two messages.

All good, dudes and dudesses. Not angry, not frustrated, not impatient, not worried, happy, pleased, thankful. I commend you all, as the is such a hard thing to discuss. !500 posts and mostly all math feedback. Right or wrong, the slimmed down proof is now mathematically judge-able. I would not have done this critical trimming without the collective voice here.

### Re: What-If 0001: Relativistic Baseball

Posted: Mon Jul 16, 2012 5:02 pm UTC
I wish steve waterman where still about. That guy was funny, while he was here, before he left the board. To never come back. Those where the days, the water days (sort of like salad days, but less crunchy unless the temperature drops below 0), the good old days.

But now steve waterman is gone, never to come back, and we will never see or hear of him again. Especially in this thread, talking about things almost completely utterly unrelated to relativistic baseball.

### Re: What-If 0001: Relativistic Baseball

Posted: Tue Jul 17, 2012 7:02 am UTC
gmalivuk wrote:Well, if he swings the bat (in vacuum, suppose), so the part hitting the ball is also moving at .9c, their velocities relative to each other (i.e. each in the other's frame) would be 99.45%c, which makes the kinetic energy of each bit increase to about 8.5 times its rest mass. This is 26.5mt instead of "merely" 4.

But what if the bat (and the ball, I suppose) were made of some kind of indestructivium such that the ball actually bounced off? How fast would it be going? Would the explosion be survivable?

Probably not, I suppose. Unless you were some kind of higher-dimensional god...

I guess we finally found out what makes Brockian Ultra-Cricket so much worse than the regular sort.

### Re: What-If 0001: Relativistic Baseball

Posted: Tue Jul 17, 2012 1:55 pm UTC
Quilbert wrote:But I think the baseball will have largely disintegrated by then, because an air molecule will deposit energy in the baseball while passing through it.

How much energy? The baseball doesn't have much time to evolve between the pitcher's mound and the batter.
When you think of it in the reference frame of the baseball, then the baseball is the target and gets hit by nitrogen (and other) molecules with an energy of 2.3 GeV per nucleon. I guess that, due to electron-electron interactions, there is a good chance for the molecule to break up on its way and for the nitrogen atoms to get ionized. Now, for bare nitrogen nuclei, I get a stopping power in the range of 100 MeV/cm in something that might be a baseball by the Bethe-Bloch formula.

Ah. So you figure that the electron will be stripped (being high-charge and low-mass) through electron-electron interactions even at relativistic velocities pretty damn quickly, and then if we model the bare nitrogen in the air going at .9 c hitting a baseball like substance it bleeds on the order of 100 MeV/cm via EM, nevermind nuclear forces?

I was completely neglecting EM, but I suppose it is the longest range force with enough impact to matter, so it might matter a bunch!
By a sequence of crude calculations, I guess that most nuclei of the baseball will be ionized and spread out in the range of 1m when they reach the batter.

That is without taking nuclei-nuclei collisions into account at all, right?
Approximately by the same time, the batter will be reached by a wave of radiation and hadrons from nucleus-nucleus collisions (those particles will be concentrated along the axis of flight because of relativistic effects). Now those nuclei and hadrons will create a major impact when they hit the batter or any other obstacle …

As this is guesswork, I might be wrong on any number of points. Anyhow, the result is the same: a huge crater and a mushroom cloud.
So, my really crappy uneducated estimates showed that the baseball could exit the Earth's atmosphere at escape velocity speeds, but I only accounted for direct nuclei-nuclei collisions (and I used the almost certainly inaccurate for this purpose "nuclei radius" from wikipedia). Would the EM interactions cause the ball to bleed energy into the atmosphere way faster than that?

### Re: What-If 0001: Relativistic Baseball

Posted: Tue Jul 17, 2012 5:22 pm UTC
Jamaican Castle wrote:
gmalivuk wrote:Well, if he swings the bat (in vacuum, suppose), so the part hitting the ball is also moving at .9c, their velocities relative to each other (i.e. each in the other's frame) would be 99.45%c, which makes the kinetic energy of each bit increase to about 8.5 times its rest mass. This is 26.5mt instead of "merely" 4.
But what if the bat (and the ball, I suppose) were made of some kind of indestructivium such that the ball actually bounced off? How fast would it be going? Would the explosion be survivable?
What explosion? If we're magicking indestructivium into the situation, then there's nothing left to explode.

Supposing, however, that this magical material doesn't violate conservation of momentum, then the resulting speed is calculated the same way it would be for much (much much) slower collisions between a ball and bat. (You'd also have to determine how elastic the collision is, of course.)

### Re: What-If 0001: Relativistic Baseball

Posted: Tue Jul 17, 2012 5:40 pm UTC
And indestructible baseball kit isn't much more implausible than one that accelerates to .9c in the first place.

If I'm remembering correctly, the energy of the collision isn't totally transferred to the bouncing object, and since it's not allowed to destroy the bat, it has to go somewhere.

It doesn't really matter, of course; imagine the reflexes you'd need to hit a ball traveling that fast in the first place?

### Re: What-If 0001: Relativistic Baseball

Posted: Tue Jul 17, 2012 5:55 pm UTC
Jamaican Castle wrote:If I'm remembering correctly, the energy of the collision isn't totally transferred to the bouncing object, and since it's not allowed to destroy the bat, it has to go somewhere.
In real baseball, that energy goes back up the bat and into the player as a sort of shockwave.

### Re: What-If 0001: Relativistic Baseball

Posted: Tue Jul 17, 2012 8:58 pm UTC
gmalivuk wrote:
Jamaican Castle wrote:If I'm remembering correctly, the energy of the collision isn't totally transferred to the bouncing object, and since it's not allowed to destroy the bat, it has to go somewhere.
In real baseball, that energy goes back up the bat and into the player as a sort of shockwave.

Yup, you'd explode if you were holding said bat unless you were Superman or something.

I remember trying to work out what would happen if you had an indestructible beating stick of some sort and could reach relativistic velocities and/or throw it at such velocities (magic in something so it teleports back to you or something so you don't gotta go chase it down afterwards) and pegged a planet with it.

Once you start getting into indestructible materials though you run into the elastic collision issue, where if it doesn't deform then it effectively transmits influences infinitely fast between it's ends, which seems like the whole thing should just conjure up an event horizon and fall out of the universe at that point.

### Re: What-If 0001: Relativistic Baseball

Posted: Tue Jul 17, 2012 9:53 pm UTC
Yakk wrote:
Baseball stadiums usually have stuff behind the catcher.

And 0.9 c / (11,190 km/s) =~ 24, so it wouldn't take much solid matter (24 times the mass of the baseball) to soak up the momentum of that baseball to below escape velocity. Roughly 24 ball-widths worth of baseball-density matter, or 1.8 meters. So a concrete pillar would get in the way, but the wall of a house wouldn't be noticed.

I didn't see anyone point out that Yakk lives on quite a planet with an escape velocity about 3600 times that of earth.

### Re: What-If 0001: Relativistic Baseball

Posted: Tue Jul 17, 2012 10:40 pm UTC
I'm pretty sure that deformation isn't necessary to prevent infinitely fast signal transmission. The material could still be perfectly elastic, and you would just get a compression wave traveling down it at ≤c.

So here's an interesting thought experiment. Lets presume Superman is literally invincible unless kryptonite is involved (and let us presume that it is not). Now Superman is holding this bat of indestructium hitting a baseball of indestructium which is traveling at 0.9c. And lets presume he's doing this in a vacuum (which is no problem for Superman) to eliminate the air-collision problem, and that his super reflexes allow him to actually track and hit a ball moving that fast.

So the ball and bat make contact, all the energy of that ball is transferred into the bat, a compression wave travels down the bat into Superman and then through Superman and then... what? Into the dirt which promptly explodes, or into random thrashing motion of Superman's limbs knocking him on his ass, or into the earth kinetically launching Superman into the air in an equal but opposite reaction? How much of that energy absorbed by the bat and Superman actually bounces back to the ball, and how fast is the ball going after it bounces back off the bat? Obviously the speed of Superman's swing matters there too, and I'm not sure what value to put there.

### Re: What-If 0001: Relativistic Baseball

Posted: Tue Jul 17, 2012 10:42 pm UTC
I know what would happen!

See, 13.7 billion years ago...

### Re: What-If 0001: Relativistic Baseball

Posted: Wed Jul 18, 2012 12:37 am UTC
Yakk wrote:
Quilbert wrote:But I think the baseball will have largely disintegrated by then, because an air molecule will deposit energy in the baseball while passing through it.

How much energy? The baseball doesn't have much time to evolve between the pitcher's mound and the batter.

See below. It should be enough energy at least to accelerate the particles to non-negligible fractions of c.
Yakk wrote:
When you think of it in the reference frame of the baseball, then the baseball is the target and gets hit by nitrogen (and other) molecules with an energy of 2.3 GeV per nucleon. I guess that, due to electron-electron interactions, there is a good chance for the molecule to break up on its way and for the nitrogen atoms to get ionized. Now, for bare nitrogen nuclei, I get a stopping power in the range of 100 MeV/cm in something that might be a baseball by the Bethe-Bloch formula.

Ah. So you figure that the electron will be stripped (being high-charge and low-mass) through electron-electron interactions even at relativistic velocities pretty damn quickly, and then if we model the bare nitrogen in the air going at .9 c hitting a baseball like substance it bleeds on the order of 100 MeV/cm via EM, nevermind nuclear forces?

I’m having a hard time predicting how long it takes for the difference between nucleus and atom to no longer matter. But as fast ions always drag along electrons, I think the electron cloud around the nucleus has an equilibrium state, which I figure is reached pretty quickly, so it doesn’t make much of a difference if you shoot bare nuclei or entire atoms or molecules at the target.
Yakk wrote:I was completely neglecting EM, but I suppose it is the longest range force with enough impact to matter, so it might matter a bunch!
By a sequence of crude calculations, I guess that most nuclei of the baseball will be ionized and spread out in the range of 1m when they reach the batter.

That is without taking nuclei-nuclei collisions into account at all, right?

Yes, that is about those nuclei that reach the batter unharmed by direct collisions.
Yakk wrote:
Approximately by the same time, the batter will be reached by a wave of radiation and hadrons from nucleus-nucleus collisions (those particles will be concentrated along the axis of flight because of relativistic effects). Now those nuclei and hadrons will create a major impact when they hit the batter or any other obstacle …

As this is guesswork, I might be wrong on any number of points. Anyhow, the result is the same: a huge crater and a mushroom cloud.
So, my really crappy uneducated estimates showed that the baseball could exit the Earth's atmosphere at escape velocity speeds, but I only accounted for direct nuclei-nuclei collisions (and I used the almost certainly inaccurate for this purpose "nuclei radius" from wikipedia). Would the EM interactions cause the ball to bleed energy into the atmosphere way faster than that?

Well, that’s what I used as well. But the residual strong force is really short-range. You might add 1fm to the radii as well, but then we account for “grazing shots” as well, which probably won’t destroy the nuclei.
Actually, if you threw that baseball straight up, I think both EM and strong force by themselves would prevent most of the baseball from leaving the atmosphere. For EM, I think the “bragg peak” would still be inside the atmosphere, but I can’t be sure without more careful calculations. For strong force, it is clear that only a small fraction of the nuclei will survive, because most of them will collide eventually. Anyway, that would probably make quite an impression in a night sky.

### Re: What-If 0001: Relativistic Baseball

Posted: Wed Jul 18, 2012 3:37 pm UTC
In my readingt, rule 6.08(b) awards a base to the batter only for a pitch that the batter does not attempt to hit. Yet the problem clearly states that the batter is trying to hit the ball. I'm not sure how a base can therefore be awarded, citing 6.08(b). Am I missing something?

### Re: What-If 0001: Relativistic Baseball

Posted: Wed Jul 18, 2012 6:37 pm UTC
The batter has no possible way to actually try to hit the ball, only intention can be attributed.

"Unsuspecting batter" being a key phrase.

### Re: What-If 0001: Relativistic Baseball

Posted: Wed Jul 18, 2012 11:35 pm UTC
I think that all current discussions regarding the current application of rule 608(b) are putting the cart before the horse. Any call, whether it be ball, strike, foul ball, or HBP would be the dominion of the home plate umpire, who would have no time to make such a call before being torn asunder by a expanding front of plasma. Seeing as that replay calls are not allowed for matters of balls and strikes in baseball, it would rightly be ruled a no-pitch, and play would resume at the discretion of the league.

### Re: What-If 0001: Relativistic Baseball

Posted: Thu Jul 19, 2012 4:17 am UTC
gmalivuk wrote:
Jamaican Castle wrote:If I'm remembering correctly, the energy of the collision isn't totally transferred to the bouncing object, and since it's not allowed to destroy the bat, it has to go somewhere.
In real baseball, that energy goes back up the bat and into the player as a sort of shockwave.

And some of the energy of that shockwave is released by the bat into the air, i.e., it is emitted as sound. I expect that the sound of an indestructium ball hitting an indestructium bat at .9c would be rather loud. OTOH, this percussive noise will probably be unnoticeable due to the other sounds being produced by air plasmafication and fusion.

### Re: What-If 0001: Relativistic Baseball

Posted: Thu Jul 19, 2012 4:26 am UTC