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Author Topic:   Flat Earth Society
CRR
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Posts: 578
From: Australia
Joined: 10-19-2016


Message 46 of 119 (819087)
09-05-2017 9:50 PM


Re: Neil deGrasse Tyson is a Flat Earther!
My post at Message 38 was somewhat tongue in cheek and has sparked an interesting discussion. I must admit I was surprised myself at the difference the Earth's curvature could make over a few kilometers. I wonder where we could find a flat (i.e. spherical) plain of sufficient extent to confirm this experimentally?

In a similar vein I also say Galileo was wrong in his experiment dropping weights off the leaning tower of Pisa; the heavy one should hit the ground first.


Replies to this message:
 Message 48 by Rrhain, posted 09-06-2017 4:11 AM CRR has responded
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Rrhain
Member
Posts: 6192
From: San Diego, CA, USA
Joined: 05-03-2003
Member Rating: 2.2


Message 47 of 119 (819099)
09-06-2017 3:51 AM
Reply to: Message 38 by CRR
09-04-2017 8:06 PM


CRR writes:

quote:
I was surprised to find that Neil deGrasse Tyson believes in a flat Earth. Here's what he said;
quote:
A bullet fired level from a gun will hit ground at same time as a bullet dropped from the same height. Do the Physics.
Neil deGrasse Tyson (@neiltyson) August 11, 2010 http://twistedsifter.com/.../best-neil-degrasse-tyson-quotes

Do the physics and you will find this is only true on a flat Earth.

Only for extremely fast bullets. Guns don't fire bullets that fast.

It's easy to test: Just get yourself a very long testing ground and rig up a gun and a bullet such that the bullet drops right when the gun goes off. Then, time how long it takes each bullet to hit the ground.

Wait...Mythbusters did that. What do you think they found?


Rrhain

Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

Minds are like parachutes. Just because you've lost yours doesn't mean you can use mine.

This message is a reply to:
 Message 38 by CRR, posted 09-04-2017 8:06 PM CRR has not yet responded

    
Rrhain
Member
Posts: 6192
From: San Diego, CA, USA
Joined: 05-03-2003
Member Rating: 2.2


Message 48 of 119 (819100)
09-06-2017 4:11 AM
Reply to: Message 46 by CRR
09-05-2017 9:50 PM


Re: Neil deGrasse Tyson is a Flat Earther!
CRR writes:

quote:
I must admit I was surprised myself at the difference the Earth's curvature could make over a few kilometers. I wonder where we could find a flat (i.e. spherical) plain of sufficient extent to confirm this experimentally?

It's called a "lake." Any sufficiently large one will do. If the earth were flat, then the surface of the water on the lake would also be flat since water levels itself out.

So get yourself on the dock and set up a sufficiently powered light source (a common laser will do). Put yourself on a boat with a target and note where on the target the laser hits. Then, simply putt on out into the lake, paying attention to where the laser hits the target. If you pay attention to the distance you've traveled, the distance between the two laser targets, and the particular direction you traveled, you'll be able to calculate the precise curvature and thus calculate the size of the earth.

You will notice that as you get further away from the laser, it will rise up the target as the earth curves away.

There was some TV show on either PBS or Discovery that did this.

But even then, that's just a demonstration of just how "small" the earth is. You don't need any fancy equipment. It's how the Ancient Greeks figured out the earth was round: The shadows cast by the sun. At noon on a specific day, calculate the angle of a shadow cast from a plumb at two different locations. You will find that they are different. Again, if you pay attention to the difference in angle, the distance between your two measurements, and the direction in which those two locations are (assuming they aren't on the same parallel), you'll be able to calculate the curvature and thus the size of the earth.

Which is precisely what Eratosthenes did and got an astoundingly accurate estimate for the size of the earth (using a well at Syene and the Pole at Alexandria).

quote:
In a similar vein I also say Galileo was wrong in his experiment dropping weights off the leaning tower of Pisa; the heavy one should hit the ground first.

And you would be wrong. There is no evidence that he actually did so but rather set it up as a thought experiment.

But then again, they did this on the moon with a hammer and a feather.


Rrhain

Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

Minds are like parachutes. Just because you've lost yours doesn't mean you can use mine.

This message is a reply to:
 Message 46 by CRR, posted 09-05-2017 9:50 PM CRR has responded

Replies to this message:
 Message 49 by NoNukes, posted 09-06-2017 9:35 AM Rrhain has not yet responded
 Message 53 by CRR, posted 09-06-2017 5:57 PM Rrhain has responded

    
NoNukes
Member
Posts: 10056
From: Central NC USA
Joined: 08-13-2010
Member Rating: 1.9


Message 49 of 119 (819104)
09-06-2017 9:35 AM
Reply to: Message 48 by Rrhain
09-06-2017 4:11 AM


Re: Neil deGrasse Tyson is a Flat Earther!
So get yourself on the dock and set up a sufficiently powered light source (a common laser will do). Put yourself on a boat with a target and note where on the target the laser hits. Then, simply putt on out into the lake, paying attention to where the laser hits the target.

Be careful with this experiment. After reading a post by Dr. Adequate on the subject, I looked up the details of the experiment and found that it was possible to get a flat earth answer if atmospheric refraction kicks in. Such problems can be aggravated by a temperature inversion. You can avoid this by setting up your sight line a few meters above the surface of the lake.


Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)

I was thinking as long as I have my hands up theyre not going to shoot me. This is what Im thinking theyre not going to shoot me. Wow, was I wrong. -- Charles Kinsey

We got a thousand points of light for the homeless man. We've got a kinder, gentler, machine gun hand. Neil Young, Rockin' in the Free World.

Worrying about the "browning of America" is not racism. -- Faith

I hate you all, you hate me -- Faith


This message is a reply to:
 Message 48 by Rrhain, posted 09-06-2017 4:11 AM Rrhain has not yet responded

    
NoNukes
Member
Posts: 10056
From: Central NC USA
Joined: 08-13-2010
Member Rating: 1.9


Message 50 of 119 (819105)
09-06-2017 9:42 AM
Reply to: Message 44 by ringo
09-05-2017 12:38 PM


As long as gravity is orthogonal to the surface, I don't think it makes any difference whether the surface is flat or convex - gravity will pull the bullet toward the surface. To fit the physics, a flat earth would need "lines of gravity" that were parallel instead of convergent at the center of mass.

Gravity is orthogonal to a finite surface only when the surface is spherical. Also, gravity is not directed towards the center of mass for shapes that are not roughly spherical. See Gauss law for the details.


Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)

I was thinking as long as I have my hands up theyre not going to shoot me. This is what Im thinking theyre not going to shoot me. Wow, was I wrong. -- Charles Kinsey

We got a thousand points of light for the homeless man. We've got a kinder, gentler, machine gun hand. Neil Young, Rockin' in the Free World.

Worrying about the "browning of America" is not racism. -- Faith

I hate you all, you hate me -- Faith


This message is a reply to:
 Message 44 by ringo, posted 09-05-2017 12:38 PM ringo has acknowledged this reply

    
dwise1
Member
Posts: 2994
Joined: 05-02-2006
Member Rating: 3.2


Message 51 of 119 (819122)
09-06-2017 2:39 PM
Reply to: Message 41 by CRR
09-04-2017 11:09 PM


Do the Math!
If you were to review my table in Message 39, you would notice that there's not much correlation between the muzzle velocity and the maximum range. For example, the Sharps with a muzzle velocity of only 1800 fps has a maximum range of 2552, whereas the M19 SPIW with a much greater muzzle velocity (4850 fps) has about the same maximum range or only slightly greater.

I think that that has to do with the mass of the slug that they're throwing (in science fiction that class of weapon is referred to as "slug throwers", though in a German castle I did see some literal slug throwers, medieval hand-held catapults). If you have ever seen actual gun trajectories, you will have noticed that they're not parabolas, but rather they start out as a parabola but then towards the end they quickly drop to the ground foreshortening the end of the trajectory greatly. This is because aerodynamic drag slows the projectile down along its horizontal vector. Based on that, I would assume that the apparent discrepancies between muzzle velocity and maximum range are due to the different masses of the projectiles, a property which I don't recall being given specifically in my reference. As you will recall from when you studied physics (which for me was about 30 years ago), a projectile of greater mass can resist aerodynamic drag longer than a projectile of lesser mass can.

But then Tyson's and Galileo's experiments were not dynamics problems (where mass matters), but rather kinematic problems (where mass does not matter), as you should recall from physics class (even I can recall that).

Also, your calculation can lead us to false assumptions such as that the drop didn't begin until at the end of that maximum range -- I had performed the same calculation. Rather, that projectile had started dropping at the very instant that it left the muzzle and our calculations must take that into account.

Doing my own integrating to obtain the formulae:

quote:

Acceleration: a(t) = g
Velocity: v(t) = gt
Displacement: s(t) = (1/2)gt2


Yes, that should be negative because of the downward direction, but we're concerned here with the magnitude so we can safely take the absolute value.

Using my Meterstock, I found that my shoulders are at a height of 1.5 meters, so if I were to aim level and fire that Walther WA-2000 (muzzle velocity of 3070 fps (935.736 m/s), max range 4084m) then it would be from that height. Let tdrop be the time for a bullet falling from that height to hit the ground:

quote:
s(tdrop) = (1/2)gtdrop2 = 1.5m
tdrop2 = 2 × 1.5m / g
g = 9.80665 m/sec2
tdrop2 = 2 × 1.5m / (9.80665 m/sec2
tdrop2 = 0.3059 (m s2 / m) = 0.3059 sec2
tdrop = 0.553 sec

In 0.553 sec, a WA-2000 bullet will have traveled 517.462 meters. At that distance, the dip of the earth's surface due to curvature would be 0.021 meters. Plugging that into the time calculation above would yield a travel time of 0.55695 sec, just about 4 milliseconds greater (0.7%). Minimal difference.

Yeah, I just now have realized that myself, that I had chosen the wrong range value. Sorry, my mistake. Maximum range is obtained by firing up at about an angle of 45°, whereas we need the range when firing level. Effective range would be pointing at a target, which should be much closer to firing level. No, actually not, since you have to aim higher to account for distance, so even the effective range would not be indicative of its range if aimed level, but rather the range where the bullet hasn't slowed down so much that it can no longer do damage -- I think that the term for a bullet that travels beyond its effective range is "spent bullet". Sorry, but it looks like the stated ranges have nothing to do with our problem, whereas the muzzle velocity does, so we're back on the right track now.

OK, now let's do the same for the highest muzzle velocity in that list, the M19 SPIW at 4850 fps (1478.28 m/s). In 0.553 sec, the time that it takes a bullet dropped from my shoulder height to hit the ground, an M19 bullet will have traveled 817.48884 meters. At that distance, the dip of the earth's surface due to curvature would be 0.05245 meters. Plugging that into the time calculation above would yield a travel time of 0.5627 sec, just about 10 milliseconds greater (1.8%). Still a minimal difference.

Of course, we are not taking all factors into account, such as aerodynamic drag (which would only serve to shorten the level-flight range and hence the extra time), gravitational effects of the sun and moon and of the truck in the parking lot, relativistic effects however minimal. Obviously, adding all factors would only make the problem far more complex than it needs to be, even too complex to be able to solve the problem, while contributing nothing to the solution. Well, with the possible exception of aerodynamic drag, but then that would turn it into a dynamics problem which would be dependent on factors that could change (eg, mass of the projectile, density and temperature of the air), all of which would detract from the basic questions of acceleration, velocity, and displacement which is what we're actually interested in here.

IOW, in order to determine the effects of one set of factors, it is common practice to either hold all other factors as constant or else simplify them out. That's basically what you do with partial derivatives. Another classic example is an electrical circuit in which we only work with the values of the resistors, capacitors, inductors, and power sources (eg, batteries) we place in that circuit while ignoring all the resistance, capacitance, and induction (referred to as "stray" or "parasitic")inherent in all the components and wiring; that doesn't mean we don't know they're there, but rather we don't know their actual values so we can't work with them analytically (though we do employ practices to try to minimize them). Simplifying out dynamics in a kinematics problem does not mean that we don't believe in dynamics. Nor does simplifying out the curvature of the earth in a basic kinematics problem mean that we believe in a flat earth. {eye-roll}

Of course, if you disagree then you can point out personally to Neil deGrasse Tyson himself that he's really a flat-earther. Be sure to share his response with us. Quoted in its entirety verbatim along with your email to him quoted in its entirety and verbatim (sorry, but we have had far too much real-life experience with creationists).


This message is a reply to:
 Message 41 by CRR, posted 09-04-2017 11:09 PM CRR has responded

Replies to this message:
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ringo
Member
Posts: 13863
From: frozen wasteland
Joined: 03-23-2005
Member Rating: 1.6


Message 52 of 119 (819123)
09-06-2017 3:17 PM
Reply to: Message 46 by CRR
09-05-2017 9:50 PM


Re: Neil deGrasse Tyson is a Flat Earther!
CRR writes:

I must admit I was surprised myself at the difference the Earth's curvature could make over a few kilometers. I wonder where we could find a flat (i.e. spherical) plain of sufficient extent to confirm this experimentally?


See the Bedford Level Experiment.
This message is a reply to:
 Message 46 by CRR, posted 09-05-2017 9:50 PM CRR has not yet responded

  
CRR
Member
Posts: 578
From: Australia
Joined: 10-19-2016


Message 53 of 119 (819134)
09-06-2017 5:57 PM
Reply to: Message 48 by Rrhain
09-06-2017 4:11 AM


Re: Galileo was wrong
RrHain writes:

But then again, they did this on the moon with a hammer and a feather.


What's the difference between doing this on the moon compared to the Earth?

The gravity is lower so they fall slow enough to be observed. There is close to a vacuum so air resistance doesn't affect the fall.

Earth however has atmosphere. Two objects of different masses, same material, same shape, will fall at different rates due to air resistance. In the case of cannon balls this would only be detectable with very precise measuring equipment, such as would not have been available to Galileo, but it will make a slight difference and the heavier one will fall faster.


This message is a reply to:
 Message 48 by Rrhain, posted 09-06-2017 4:11 AM Rrhain has responded

Replies to this message:
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CRR
Member
Posts: 578
From: Australia
Joined: 10-19-2016


Message 54 of 119 (819135)
09-06-2017 6:11 PM
Reply to: Message 51 by dwise1
09-06-2017 2:39 PM


Re: Do the Math!
Thank you Dwise1 for your detailed calculations. You have confirmed what I said; do the physics and the fired bullet will hit the ground later than the dropped one. This effect becomes more pronounced with higher muzzle velocities.

There's no reason why you can't stand on a platform to do this experiment so that the initial height could be 9.81 meters if you wanted. That would make the drop time 1 second (neglecting air resistance). The bullet will take a fraction longer to hit the ground.

You could even do this on the moon and almost eliminate air resistance. The smaller radius and lower gravity will enhance the difference in fall time.
The escape velocity of the moon is 2.38km/s which is getting much closer to a rifle muzzle velocity. Potentially you could produce a rifle that could fire a bullet at escape velocity on the moon.


This message is a reply to:
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Replies to this message:
 Message 56 by caffeine, posted 09-07-2017 1:21 PM CRR has responded

  
Rrhain
Member
Posts: 6192
From: San Diego, CA, USA
Joined: 05-03-2003
Member Rating: 2.2


Message 55 of 119 (819137)
09-06-2017 9:15 PM
Reply to: Message 53 by CRR
09-06-2017 5:57 PM


Re: Galileo was wrong
CRR responds to me:

quote:
The gravity is lower so they fall slow enough to be observed.

Irrelevant. That the lower gravity means you can easily see the two masses falling at the same rate without special equipment doesn't mean they aren't falling at the same rate or that a higher gravitation field would change anything about the relationship of their paths with respect to each other. Gravity is gravity.

quote:
There is close to a vacuum so air resistance doesn't affect the fall.

That's kinda the point. You do understand how air resistance would impart a separate force and thus would complicate a measurement of the gravitational field, yes? Not that it can't be done, mind you, but that it complicates a simple experiment. That's why there is such a thing as "terminal velocity" in a fluid.

You do understand how terminal velocity works, yes?

quote:
Earth however has atmosphere. Two objects of different masses, same material, same shape, will fall at different rates due to air resistance.

Again, that's kinda the point. Do you not understand what Galileo was referring to?

And that he actually understood a bit about air resistance?

And thus he never actually carried out the experiment because of his understanding of air resistance but was referring to a thought experiment?

Do you even know what the actual thought experiment was?

Hint: String.

Here's another hint: There is an effect that corresponds to your claim regarding massive objects and their behaviour in gravitational fields. It's part of the reason why there is a retroreflector on the moon: It allows us to measure the distance between the earth and the moon and can be used to detect this effect (the name is for you to look up as homework.)

It has never been detected.

quote:
In the case of cannon balls this would only be detectable with very precise measuring equipment, such as would not have been available to Galileo, but it will make a slight difference and the heavier one will fall faster.

So no, you don't understand air resistance, how gravity works, or anything about Galileo's work.

Do you know how to calculate terminal velocity?


Rrhain

Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

Minds are like parachutes. Just because you've lost yours doesn't mean you can use mine.

This message is a reply to:
 Message 53 by CRR, posted 09-06-2017 5:57 PM CRR has not yet responded

    
caffeine
Member
Posts: 1349
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 2.4


Message 56 of 119 (819171)
09-07-2017 1:21 PM
Reply to: Message 54 by CRR
09-06-2017 6:11 PM


Re: Do the Math!
There's no reason why you can't stand on a platform to do this experiment so that the initial height could be 9.81 meters if you wanted. That would make the drop time 1 second (neglecting air resistance). The bullet will take a fraction longer to hit the ground.

Assuming no air resistance, the drop time would be closer to 1 1/2 seconds (sqrt of 2). You're mixing up the downward speed and the downward acceleration.


This message is a reply to:
 Message 54 by CRR, posted 09-06-2017 6:11 PM CRR has responded

Replies to this message:
 Message 57 by NoNukes, posted 09-07-2017 4:12 PM caffeine has responded
 Message 60 by CRR, posted 09-07-2017 5:43 PM caffeine has not yet responded

  
NoNukes
Member
Posts: 10056
From: Central NC USA
Joined: 08-13-2010
Member Rating: 1.9


Message 57 of 119 (819178)
09-07-2017 4:12 PM
Reply to: Message 56 by caffeine
09-07-2017 1:21 PM


Re: Do the Math!
Assuming no air resistance, the drop time would be closer to 1 1/2 seconds (sqrt of 2). You're mixing up the downward speed and the downward acceleration.

More to the point. He is making silly ridiculous errors in computation while complaining about an approximation by Galileo. His own answer is about 40% too low.

By the way, heavy "objects hit the ground first due to air resistance" requires a lot of qualifiers. Example, what hits the ground first, a three pound package of nearly folded cotton shirts or a one pound steel ball?

Or a man with an opened heavy parachute versus a man with no chute?

Or a fat man versus a lighter, skinny man?

Edited by NoNukes, : No reason given.


Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)

I was thinking as long as I have my hands up theyre not going to shoot me. This is what Im thinking theyre not going to shoot me. Wow, was I wrong. -- Charles Kinsey

We got a thousand points of light for the homeless man. We've got a kinder, gentler, machine gun hand. Neil Young, Rockin' in the Free World.

Worrying about the "browning of America" is not racism. -- Faith

I hate you all, you hate me -- Faith


This message is a reply to:
 Message 56 by caffeine, posted 09-07-2017 1:21 PM caffeine has responded

Replies to this message:
 Message 58 by caffeine, posted 09-07-2017 4:34 PM NoNukes has responded
 Message 61 by CRR, posted 09-07-2017 6:08 PM NoNukes has responded

    
caffeine
Member
Posts: 1349
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 2.4


Message 58 of 119 (819181)
09-07-2017 4:34 PM
Reply to: Message 57 by NoNukes
09-07-2017 4:12 PM


Re: Do the Math!
Or a fat man versus a lighter, skinny man?

This one actually intrigues me. Can a fat man actually fall slower by presenting a bigger surface area? My Physics 101 knowledge never got as far as dealing with air resistance.


This message is a reply to:
 Message 57 by NoNukes, posted 09-07-2017 4:12 PM NoNukes has responded

Replies to this message:
 Message 59 by NoNukes, posted 09-07-2017 4:49 PM caffeine has not yet responded

  
NoNukes
Member
Posts: 10056
From: Central NC USA
Joined: 08-13-2010
Member Rating: 1.9


Message 59 of 119 (819182)
09-07-2017 4:49 PM
Reply to: Message 58 by caffeine
09-07-2017 4:34 PM


Re: Do the Math!
Can a fat man actually fall slower by presenting a bigger surface area?

Yes, he can. In fact, a skinny man can alter his terminal velocity considerably by reorienting himself. (Laying out flat vs. a headfirst dive)


Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)

I was thinking as long as I have my hands up theyre not going to shoot me. This is what Im thinking theyre not going to shoot me. Wow, was I wrong. -- Charles Kinsey

We got a thousand points of light for the homeless man. We've got a kinder, gentler, machine gun hand. Neil Young, Rockin' in the Free World.

Worrying about the "browning of America" is not racism. -- Faith

I hate you all, you hate me -- Faith


This message is a reply to:
 Message 58 by caffeine, posted 09-07-2017 4:34 PM caffeine has not yet responded

    
CRR
Member
Posts: 578
From: Australia
Joined: 10-19-2016


Message 60 of 119 (819184)
09-07-2017 5:43 PM
Reply to: Message 56 by caffeine
09-07-2017 1:21 PM


Re: Do the Math!
caffeine writes:

Assuming no air resistance, the drop time would be closer to 1 1/2 seconds


You're right! Turns out I can make mistakes too.
s=(1/2)at^2; so the platform should be high enough to give an initial height of 4.9m. Or you can start with an initial height of 19.6m to get a 2 second drop time.

Edited by CRR, : No reason given.


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