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As the Ships Come Sailing In...

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EarthTAG

As the Ships Come Sailing In...
« Reply #30 on: November 25, 2006, 11:32:43 PM »
Wait a sec... How can gravity bend the light down so that you can't see all of a ship if gravity doesn't exist? >> << >> I thought we were all just accelerating upwards at 1g.
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skeptical scientist

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As the Ships Come Sailing In...
« Reply #31 on: November 25, 2006, 11:58:33 PM »
Quote from: "EarthTAG"
Wait a sec... How can gravity bend the light down so that you can't see all of a ship if gravity doesn't exist? >> << >> I thought we were all just accelerating upwards at 1g.

Fine, it's not bending down from gravity, it's bending down in our reference frame due to the fact we're accelerating. It's still complete bull.
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EarthTAG

As the Ships Come Sailing In...
« Reply #32 on: November 27, 2006, 09:36:36 PM »
Yeah, but light would bounce between the icewalls some 16 time before it would even get remotely close to the ground if it started off going horizontal from the top of a mast. Let's assume the mast is 7 meters tall and our observer is 2 meters tall. So, light needs to fall roughly 5 meters for it to "disappear."

Pos(final) = Pos(initial) + Vel(Inital)*Time + 1/2*Accel*time^2
5 = 0 + 0*X + 1/2*10*X^2
5 = 5*X^2
1 = X^2
1 = X

So, it would take exactly one second to fall from the top of the mast to below this person's like of sight. Light travels at C, or roughly 8000000 meters a second. Therefore, the ship would have to be roughly 8,000 kilometers away.

The Earth's circumfrence, pole to pole... Or very close to northernhub to ice wall... Is roughly 40000 km. Thus, the ship would need to be 1/5 of the way "across" the world. I have difficulty people can see across the atlantic. ^^;;
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DragonXero

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« Reply #33 on: November 27, 2006, 10:06:00 PM »
Quote from: "skeptical scientist"
Quote from: "EarthTAG"
Wait a sec... How can gravity bend the light down so that you can't see all of a ship if gravity doesn't exist? >> << >> I thought we were all just accelerating upwards at 1g.

Fine, it's not bending down from gravity, it's bending down in our reference frame due to the fact we're accelerating. It's still complete bull.

Again, reaching well beyond my knowledge here, but I would guess that it wouldn't work the same with inertia causing the downward pull as it would with gravit causing it.  Light is affected by gravity.  I don't think the same can be said of inertia.  Maybe I'm wrong, but I can only see two other ways of this going.  The light falls off much more quickly than it could with gravity (since its initial speed, that of the earth when it was created, would be much less than the speed of the constantly accelerating earth), or the light would never fall off because its speed inexplicably keeps increasing with the earth.
Obviously the former theory is closer to what might actually happen, but I have a feeling there's some math that can easily disprove my little idea.
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« Reply #34 on: November 27, 2006, 10:33:35 PM »
Quote from: "DragonXero"
Again, reaching well beyond my knowledge here, but I would guess that it wouldn't work the same with inertia causing the downward pull as it would with gravit causing it.  Light is affected by gravity.  I don't think the same can be said of inertia.  Maybe I'm wrong, but I can only see two other ways of this going.  The light falls off much more quickly than it could with gravity (since its initial speed, that of the earth when it was created, would be much less than the speed of the constantly accelerating earth), or the light would never fall off because its speed inexplicably keeps increasing with the earth.
Obviously the former theory is closer to what might actually happen, but I have a feeling there's some math that can easily disprove my little idea.

I'm not sure what you mean by "inertia" here - the distinction should really be between gravity and accelerating reference frames. However, light behaves the same way in either - this is another result of general relativity (actually it was always thought that light would appear to accelerate in an accelerating reference frame, but Einstein was the first to predict it would also accelerate in a gravitational field.)
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DragonXero

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« Reply #35 on: November 27, 2006, 11:58:53 PM »
I was clumsily attempting to describe the behavior of light's motion in relation to a body like earth.  Are you saying that light would fall off at the same distance on both models (gravity and accelerating body pushing everything at 1g)?  I always thought that light was "bent" by gravity because of the electromagnetic force.  I know that a gun fired on either model would end up with the bullet landing in the same place, but I didn't think light had the same properties.

Aside from the fact that it's moving at the speed of light, I thought it was also different from other particles. I mean, for one thing, it actually goes at the speed of light, continues to move at that speed (why?) and rather than stopping when it meets something of equal mass, deflects and goes in another direction at the same speed, apparently unaffected by friction.

Though I've heard of expierments where light was slowed by a huge factor, so I guess I know jack about light.
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skeptical scientist

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« Reply #36 on: November 28, 2006, 12:31:52 AM »
Quote from: "DragonXero"
Though I've heard of expierments where light was slowed by a huge factor, so I guess I know jack about light.

Light moves at different rates in different media. For example glass slows light more than atmosphere, and atmosphere slows light relative to it's speed in a vacuum. When people refer to the speed of light, they mean its speed in vacuum.

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I was clumsily attempting to describe the behavior of light's motion in relation to a body like earth.  Are you saying that light would fall off at the same distance on both models (gravity and accelerating body pushing everything at 1g)?

Yes, it would. Part of Einstein's Theory of General Relativity is that a uniformly accelerating reference frame is indistinguishable from a uniform gravitational field. No experiment can ever detect the difference between the two.

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I always thought that light was "bent" by gravity because of the electromagnetic force.

No, gravity and the electromagnetic force are two very different things. Light is bent by gravity for the same reason that any other object is affected by gravity, more or less.

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I know that a gun fired on either model would end up with the bullet landing in the same place, but I didn't think light had the same properties.

It does.

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Aside from the fact that it's moving at the speed of light, I thought it was also different from other particles.
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Oh, it certainly is!
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I mean, for one thing, it actually goes at the speed of light, continues to move at that speed (why?)

(I'm going to assume we're in a vacuum to simplify matters for this explanation.) The classical explanation of why light always moves at the same velocity is a consequence of Maxwell's Equations. Light is really just vibrations in the electromagnetic field, and such vibrations propagate according to differential equations derived from Maxwell's equations, with the result that they always move at the same velocity (at least in vacuum - maxwell's equations become more complicated in different media). I'm not really sure about the quantum-mechanical explanation (it's possible that it's essentially the same, or quite different) and I don't really have a better explanation than this one.

Essentially it's always observed as moving at the same velocity, and it fits in with a consistent theory of physics, so it is so. We don't really know why it is beyond those facts.

That said, light does behave differently in a gravitational field/accelerating reference frame than ordinary matter does, because it does always move at the same speed. It bends, but does not change speed. So as the light is accelerated, it keeps moving at the speed of light, but in a slightly different direction due to the acceleration.

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and rather than stopping when it meets something of equal mass, deflects and goes in another direction at the same speed, apparently unaffected by friction.

Or else is absorbed. There's no reason that it should be effected by friction. Other single particles are not affected by friction either. Friction is a large-scale phenomenon caused by the interactions of billions of atoms. Any single particle cannot by affected by friction - only large objects such as shoes or bacteria or DNA molecules* can.

*You have no idea how much of a kick I just got out of referring to 'large objects such as DNA molecules'.
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DragonXero

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« Reply #37 on: December 04, 2006, 11:37:54 PM »
Thinking more clearly, I had already learned a lot of that stuff.  Though I still wonder about certain aspects of light.  I know waves and particles act differently, but it seems to me that the same effect we use on long-range satellites (slingshotting, basically) should work on ilght.  In that case, I would expect any measurment of distance gained from light that's been bent by gravity should need to be slightly adjusted for this alteration of speed...  
And forgive me if I'm wrong, but hasn't light been observed to have the properties of both waves and particles?

Also, to explain my notions of electromagnetic fields and such, I was under the impression that it was thought that gravity was electromagnetic like light, gamma radiation and satellite signals (which apparently don't exist. Tee hee.)

Of course, I'm pretty sure that all has to do with attempts to create a unified field theory.  I say we should stick with curing AIDS and VR similar to the Matrix, without the dying etc.
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Erasmus

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As the Ships Come Sailing In...
« Reply #38 on: December 04, 2006, 11:50:54 PM »
Quote from: "DragonXero"
it seems to me that the same effect we use on long-range satellites (slingshotting, basically) should work on ilght.  In that case, I would expect any measurment of distance gained from light that's been bent by gravity should need to be slightly adjusted for this alteration of speed...


The speed of light is always the same, regardless of the relative speed of source and emitter.  If we bounce a light signal off an object, the distance to that object is half the total transit time, scaled by the speed of light.  You will get the same value for distance if you use a really long meter stick to measure it.

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Also, to explain my notions of electromagnetic fields and such, I was under the impression that it was thought that gravity was electromagnetic like light, gamma radiation and satellite signals (which apparently don't exist. Tee hee.)


While there are attempts to unify gravity with electromagnetism, no testable solution has been proposed.  At this point in time, the only similarity between gravity and electromagnetic fields is that changes in those fields propagate through space at the speed of light.
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Fezmonkey

As the Ships Come Sailing In...
« Reply #39 on: December 04, 2006, 11:51:29 PM »
See http://theflatearthsociety.org/forums/viewtopic.php?t=6680 for another explanation of the ship example.
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Seriously

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As the Ships Come Sailing In...
« Reply #40 on: December 05, 2006, 08:07:12 AM »
Quote from: "Jie"
Here's an interesting view...
http://www.duck.org/flatearth/ships.asp


That, my friend, is HORSESHIT.

The mass of the Earth is NOT ENOUGH to bend light in ANY measurable way. Even the sun can only bend light by a FRACTION of a degree. Only large galaxies / black holes can bend light in a directly observable fashion.

This blatant mutilation of scientific theories is the reason Flat-Earthers will NEVER be accepted. Get your act together, all of you.
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haseshifter was right when he said Watttttttup was right when he said joseph bloom is right, The Engineer is a douchebag.

PS This is what part of the alphabet would look like if Q and R were eliminated.
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Seriously

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« Reply #41 on: December 05, 2006, 09:42:27 AM »
Light is NOT bent directly by gravity.

The force of gravity = GMm/r^2

G = Constant of Gravitation
M = mass of object 1 (planet or whatever)
m = mass of object 2 (in this case, a photon)
r = distance between objects
it requires two masses, and since light has no mass, gravity cannot exert a force on light.

Einstein's Theory of General Relativity states that "Matter bends spacetime" much like a bowling ball on a rubber sheet. The light is bent by the distortions in spacetime caused by a sufficiently large mass, i.e. a galaxy. Gravity does NOT exert a force on light.
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haseshifter was right when he said Watttttttup was right when he said joseph bloom is right, The Engineer is a douchebag.

PS This is what part of the alphabet would look like if Q and R were eliminated.
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Insaneman

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As the Ships Come Sailing In...
« Reply #42 on: December 05, 2006, 09:51:56 AM »
Quote from: "Seriously"
Only large galaxies / black holes can bend light in a directly observable fashion.

Not really, a brown dwarf is enough for microlensing.
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TheEngineer

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« Reply #43 on: December 05, 2006, 11:53:13 AM »
Quote from: "Seriously"
Light is NOT bent directly by gravity.

The force of gravity = GMm/r^2

G = Constant of Gravitation
M = mass of object 1 (planet or whatever)
m = mass of object 2 (in this case, a photon)
r = distance between objects
it requires two masses, and since light has no mass, gravity cannot exert a force on light.

Einstein's Theory of General Relativity states that "Matter bends spacetime" much like a bowling ball on a rubber sheet. The light is bent by the distortions in spacetime caused by a sufficiently large mass, i.e. a galaxy. Gravity does NOT exert a force on light.

I like your selective, patch-work explanation.
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Seriously

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« Reply #44 on: December 05, 2006, 01:26:22 PM »
Explain it then!

Since you obviously know something that I don't, maybe you could share it with the class. Instead of posting sarcastic comments, enlighten us!
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haseshifter was right when he said Watttttttup was right when he said joseph bloom is right, The Engineer is a douchebag.

PS This is what part of the alphabet would look like if Q and R were eliminated.
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TheEngineer

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As the Ships Come Sailing In...
« Reply #45 on: December 05, 2006, 01:31:14 PM »
Pick a theory.  What is gravity?  Is it a force that only acts on objects with mass, or is it the acceleration of objects due to the curvature of space?
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Erasmus

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« Reply #46 on: December 05, 2006, 01:38:18 PM »
Quote from: "Seriously"
Explain it then!


Sorry, I'm losing track of the conversation.  Which bit do you need explained?
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Seriously

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« Reply #47 on: December 05, 2006, 02:31:27 PM »
I thought you were an engineer? Shouldn't you know that?

Gravity is a force exerted on an object with mass. Mass is believed to curve spacetime, according to General Relativity. This curving effect would produce a gravitational attraction towards a large body.
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haseshifter was right when he said Watttttttup was right when he said joseph bloom is right, The Engineer is a douchebag.

PS This is what part of the alphabet would look like if Q and R were eliminated.
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TheEngineer

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As the Ships Come Sailing In...
« Reply #48 on: December 05, 2006, 03:39:15 PM »
Quote from: "TheEngineer"
Quote from: "Seriously"
Light is NOT bent directly by gravity.

The force of gravity = GMm/r^2

G = Constant of Gravitation
M = mass of object 1 (planet or whatever)
m = mass of object 2 (in this case, a photon)
r = distance between objects
it requires two masses, and since light has no mass, gravity cannot exert a force on light.

Einstein's Theory of General Relativity states that "Matter bends spacetime" much like a bowling ball on a rubber sheet. The light is bent by the distortions in spacetime caused by a sufficiently large mass, i.e. a galaxy. Gravity does NOT exert a force on light.

I like your selective, patch-work explanation.

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Explain it then!

Since you obviously know something that I don't, maybe you could share it with the class. Instead of posting sarcastic comments, enlighten us!

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Pick a theory. What is gravity? Is it a force that only acts on objects with mass, or is it the acceleration of objects due to the curvature of space?
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Jake

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« Reply #49 on: December 05, 2006, 04:09:58 PM »
Gravity has no effect on light.
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semperround

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« Reply #50 on: December 05, 2006, 04:31:12 PM »
Quote from: "Jake"
Gravity has no effect on light.


bullshit! gravity bends light around objects. this is particulary evedent around massive objects. check out this article from wikipedia.

http://en.wikipedia.org/wiki/Gravitational_lensing
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Jake

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« Reply #51 on: December 05, 2006, 04:36:23 PM »
I stand corrected.
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