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Earth's acceleration

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Sanirius

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Earth's acceleration
« on: January 05, 2007, 12:33:28 AM »
If the earth is accelerating upwards, shouldnt we be pulled down stronger every second? I dont think the earth can be accelerating. You should say its moving with one speed, cuz the force is staying the same.
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TheEngineer

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Earth's acceleration
« Reply #1 on: January 05, 2007, 12:35:33 AM »
Acceleration is constant, therefore force is constant.  We can't feel velocity.
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Namfuak

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Earth's acceleration
« Reply #2 on: January 05, 2007, 12:42:42 AM »
But if accelleration isn't zero, then the Earth's velocity would increase.  Accelleration is the rate of increrase in an object's velocity, that is 8th grade physics.

Basically, he is pointing out a technicallity.  You need to change accelleration to velocity.  It isn't something to argue about.  This comes from an REer, so it is something that I'm helping you.
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TheEngineer

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Earth's acceleration
« Reply #3 on: January 05, 2007, 12:49:31 AM »
Quote from: "Namfuak"
But if accelleration isn't zero, then the Earth's velocity would increase.  Accelleration is the rate of increrase in an object's velocity, that is 8th grade physics.

When did I say there was a constant velocity?
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Basically, he is pointing out a technicallity. You need to change accelleration to velocity. It isn't something to argue about. This comes from an REer, so it is something that I'm helping you.

Helping me what?
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Namfuak

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Earth's acceleration
« Reply #4 on: January 05, 2007, 01:08:50 AM »
Quote from: "TheEngineer"
Quote from: "Namfuak"
But if accelleration isn't zero, then the Earth's velocity would increase.  Accelleration is the rate of increrase in an object's velocity, that is 8th grade physics.

When did I say there was a constant velocity?


Well, I guess that by "You don't notice the downward force because it is constant" you never said anything about constant velocity

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Basically, he is pointing out a technicallity. You need to change accelleration to velocity. It isn't something to argue about. This comes from an REer, so it is something that I'm helping you.

Helping me what?


The something was saying that it was amazing or some synonym, though that is a commonly used expression and I'm surprised that you don't know it.
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midgard

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Earth's acceleration
« Reply #5 on: January 05, 2007, 04:28:45 AM »
What Engineer is pointing out is that when you're travelling at a constant rate in a car you don't feel anything (except going around corners but that is another topic). When you accelerate and brake you get pushed backwards and forwards respectively (watch the fluffy dice).

If you can't notice it in a car go for a trip on a plane and you'll notice it.

It is Sanirius here and not the Engineer that doesn't understand basic physics. Constant velocity would mean there would be no "gravity", you need constant acceleration for this.
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Sanirius

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Earth's acceleration
« Reply #6 on: January 05, 2007, 06:23:47 AM »
u guys are right, i dont understand basic physics, but i was just wondering... cuz when u "accelerate" ur gaining speed right? so the earth would be going faster...
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TheEngineer

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Earth's acceleration
« Reply #7 on: January 05, 2007, 06:27:35 AM »
Yep, that's what happens when you accelerate.
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midgard

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Earth's acceleration
« Reply #8 on: January 05, 2007, 06:28:35 AM »
The earth would be getting faster and faster and faster. That's correct, that's what acceleration is. Before you ask, no it would not reach the speed of light. The acceleration is only constant from the surface of the earth, if you were to jump off the edge of the earth it would appear that the earth's acceleration was decreasing (acceleration not speed). This is because of the effects of relativity.
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Sanirius

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Earth's acceleration
« Reply #9 on: January 05, 2007, 06:30:23 AM »
oh and btw, i dont know physics cuz im rather young, i dunno how old u guys are, but i am 16 and in highschool... plz dont blame me for not knowing  :(
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TheEngineer

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Earth's acceleration
« Reply #10 on: January 05, 2007, 06:31:20 AM »
Quote from: "Namfuak"

Well, I guess that by "You don't notice the downward force because it is constant" you never said anything about constant velocity

I never said "You don't notice the downward force because it is constant" either.  You notice the force due to the constant acceleration.  If you were traveling at a constant velocity, as Sanirius suggested, you would not feel any force from the earth.
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Namfuak

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Earth's acceleration
« Reply #11 on: January 05, 2007, 10:18:05 AM »
That was somewhere in the FAQ, but anyway.

Acceleration: the act of accelerating; increase of speed or velocity.
Velocity: The speed and direction of motion of a moving body.

If we were accelerating, as you said, it wouldn't stay at 9.8m/s^2.  It would keep adding, so the speed would then be 19.6m/s^2, then 29.4m/s^2, etc.  Eventually, it would either hit the speed of light or it would stop accelerating, but that wouldn't matter because the pressure would have killed us long ago.
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TheEngineer

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Earth's acceleration
« Reply #12 on: January 05, 2007, 10:23:38 AM »
Quote from: "Namfuak"
That was somewhere in the FAQ, but anyway.

Acceleration: the act of accelerating; increase of speed or velocity.
Velocity: The speed and direction of motion of a moving body.

If we were accelerating, as you said, it wouldn't stay at 9.8m/s^2.

The acceleration is constant.  The velocity would be increasing.
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It would keep adding, so the speed would then be 19.6m/s^2, then 29.4m/s^2, etc.

That is what happens when you accelerate.
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Eventually, it would either hit the speed of light or it would stop accelerating,

You are trying to apply Newtonian mechanics to a Relativistic situation.  The earth would never reach the speed of light.
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but that wouldn't matter because the pressure would have killed us long ago.

If the acceleration is a constant 9.8m/s^2, where will all this pressure come from?
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Namfuak

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Earth's acceleration
« Reply #13 on: January 05, 2007, 10:28:30 AM »
My point still stands.  If we went up at any constant rate of acceleration, we would hit the speed of light or stop accelerating, that is the definition of acceleration, the increase in speed or velocity.  Even if we weren't crushed flat for some reason (I'm a freshman in high school so if there is some obvious physics reason for this I won't mind hearing it, but it doesn't matter anyway), in fact if we aren't, that would mean that when Earth stopped accelerating at the speed of light, we would go weightless, or when it reached and surpassed the speed of light, who knows what would happen? (I think we all just lose our ability to see, but that is just me)
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EnragedPenguin

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Earth's acceleration
« Reply #14 on: January 05, 2007, 10:39:23 AM »
Quote from: "Namfuak"
My point still stands.  If we went up at any constant rate of acceleration, we would hit the speed of light or stop accelerating. In fact if we aren't, that would mean that when Earth stopped accelerating at the speed of light, we would go weightless, or when it reached and surpassed the speed of light, who knows what would happen? (I think we all just lose our ability to see, but that is just me)


Erasmus explains it rather well here.

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Even if we weren't crushed flat for some reason (I'm a freshman in high school so if there is some obvious physics reason for this I won't mind hearing it, but it doesn't matter anyway),


The obvious physics reason for this is that the human body is capable of withstanding an acceleration of 1g.
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NinjaMidgetOwnsU

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Earth's acceleration
« Reply #15 on: January 05, 2007, 10:42:08 AM »
Quote from: TheEngineer
Quote from: "Namfuak"


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Eventually, it would either hit the speed of light or it would stop accelerating,

You are trying to apply Newtonian mechanics to a Relativistic situation.  The earth would never reach the speed of light.


What Mr. Engineer is trying to say is "you're playing in my imaginary little world so you have to go by my rules or I'll give you a really bad indian burn and tell mommy"

Time to get a life, dude
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EnragedPenguin

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Earth's acceleration
« Reply #16 on: January 05, 2007, 10:44:10 AM »
Quote from: "NinjaMidgetOwnsU"


What Mr. Engineer is trying to say is "you're playing in my imaginary little world so you have to go by my rules or I'll give you a really bad indian burn and tell mommy"


No, I think he was trying to say exactly what he said-Newtonian mechanics do not work in relativistic situations (i.e,. when moving at velocities approaching c.)
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TheEngineer

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Earth's acceleration
« Reply #17 on: January 05, 2007, 10:44:20 AM »
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My point still stands. If we went up at any constant rate of acceleration, we would hit the speed of light or stop accelerating, that is the definition of acceleration, the increase in speed or velocity. Even if we weren't crushed flat for some reason (I'm a freshman in high school so if there is some obvious physics reason for this I won't mind hearing it, but it doesn't matter anyway), in fact if we aren't, that would mean that when Earth stopped accelerating at the speed of light, we would go weightless, or when it reached and surpassed the speed of light, who knows what would happen? (I think we all just lose our ability to see, but that is just me)

Since you are only in high school, you have only been taught Newton's laws and the basic kinematics equations.  They are inaccurate.  This inaccuracy only presents itself as speed approaches fractions of the speed of light.  

Look at it this way:  We know that the speed of light is the fastest anything can go right?  So let's say you have a space ship that can travel at c.  You take out your trusty flashlight and shine it ahead of you.  We know the speed of light is c but the ship is already at c.  So does that mean the light is actually going at 2c?  No, that's not possible, but it is what basic kinematics would say is true.

Velocity does not add up linerally as the kinematics would lead you to believe.  It actually adds like this: w=(u+v)/(1+uv/c^2).  At low speeds, the difference is unnoticable.

Now, according to relativity, no two observers traveling at different speeds will measure acceleration to be the same.  To us on the earth, accerlation is constant, but to someone not accelerated by the earth, the acceleration will be decreasing, but the earth will still be gaining speed.

The force we feel is dependant on acceleration only.  The acceleration is constant, so the force will be constant also.  We can't feel velocity.
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Namfuak

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Earth's acceleration
« Reply #18 on: January 05, 2007, 10:47:20 AM »
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From Alice's perspective, the Earth moves at an ever increasing rate, but the acceleration is not constant -- it decreases over time in such a way that the Earth never surpasses the speed of light.


So it is not constant acceleration, therefore we would notice it decrease, if not physically ourselves then by the numerous tests everyday to examine the speed of gravity.

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Look at it this way:  We know that the speed of light is the fastest anything can go right?


We don't know this.  Has anyone ever reached that and then either broken it or not been able to accelerate anymore?
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TheEngineer

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Earth's acceleration
« Reply #19 on: January 05, 2007, 10:52:59 AM »
Quote from: "Namfuak"
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From Alice's perspective, the Earth moves at an ever increasing rate, but the acceleration is not constant -- it decreases over time in such a way that the Earth never surpasses the speed of light.


So it is not constant acceleration, therefore we would notice it decrease, if not physically ourselves then by the numerous tests everyday to examine the speed of gravity.

In our frame of reference, the acceleration is constant.  To someone not on the earth, the acceleration is decreasing.
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We don't know this.  Has anyone ever reached that and then either broken it or not been able to accelerate anymore?

Are you discounting your own scientists' findings now?
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Namfuak

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Earth's acceleration
« Reply #20 on: January 05, 2007, 11:09:29 AM »
Quote from: "TheEngineer"

In our frame of reference, the acceleration is constant.  To someone not on the earth, the acceleration is decreasing.


But the acceleration of the Earth can be measured.  It requires a ball, a ruler, and a stopwatch.

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We don't know this.  Has anyone ever reached that and then either broken it or not been able to accelerate anymore?

Are you discounting your own scientists' findings now?


No, I'm using your strategy of saying that nobody has physically proven it, so therefore it is not nessesarilly fact or fiction.
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GeoGuy

Earth's acceleration
« Reply #21 on: January 05, 2007, 11:11:28 AM »
Quote from: "Namfuak"


But the acceleration of the Earth can be measured.  It requires a ball, a ruler, and a stopwatch.

That doesn't mean it will be measured the same by all observers. Acceleration is relative.
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GeoGuy

Earth's acceleration
« Reply #22 on: January 05, 2007, 11:18:12 AM »
This same question was posed a long time ago by one of our members to the folks at "Physics Forums".

Clicky
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Namfuak

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Earth's acceleration
« Reply #23 on: January 05, 2007, 11:29:57 AM »
Thanks for the link.  Disregard all of my previous questions, and answer "Why does gravity decrease as we go higher in the air?"
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GeoGuy

Earth's acceleration
« Reply #24 on: January 05, 2007, 11:58:28 AM »
It doesn't.
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Sanirius

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Earth's acceleration
« Reply #25 on: January 05, 2007, 01:37:20 PM »
Quote from: "Namfuak"
Thanks for the link.  Disregard all of my previous questions, and answer "Why does gravity decrease as we go higher in the air?"


it doesnt decrease when we go higher into the air. it depends on ur location on earth, both the north and south pole have a higher gravitational pull cuz their closer to the core... wait that doesnt sound right does it... ah well ill post anyways
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James

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Earth's acceleration
« Reply #26 on: January 05, 2007, 05:05:25 PM »
Quote from: "midgard"
The acceleration is only constant from the surface of the earth, if you were to jump off the edge of the earth it would appear that the earth's acceleration was decreasing (acceleration not speed). This is because of the effects of relativity.


In my opinion this isn't true. The acceleration is constant for the whole material universe. Yes, it's constantly getting faster, but if you think about it there is no frame of reference outside of the material universe from which the SPEED of the Earth (and matter of the universe) could be measured, hence the speed of the Earth is non-calculable the Earth isn't travelling at "a speed" as we could possibly understand it. The speed of the Earth at any given time is Null, in the sense that it can't be recorded or defined.

The rate of acceleration of the Earth can, however, be measured - it's what Conspiracy dupes call "gravity".

Edit: If you were to jump of the edge of the Earth, you would accelerate at the same rate as the Earth. You'd seem to be just standing on an invisible platform of space (the UA).
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zaudragon

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Earth's acceleration
« Reply #27 on: January 05, 2007, 05:27:21 PM »
That only happens when you use æther.

One “FE” site is hugely misleading. It appears as though FE uses æther, when it really doesn’t :D
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