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I'm a Particle Astrophysicist, ask me anything
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Tsadkiel
Aliastra
Gallente Federation
#321 - 2012-03-12 20:56:21 UTC
Terminal Insanity wrote:
Tsadkiel wrote:

this is not true, so far as we understand it. in physics we would say that the universe is non-deterministic, which is a fancy way to say that it is impossible to know the position and momentum of every particle in the universe simultaneously. we have experimental evidence to support this claim in measurements of the consequences to Heisenberg's Uncertainty Principle.

now, locally and specifically, yes, science can make very precise predictions (planetary orbits for example). but these measurements always carry some measure of uncertainty; that some object will be at some location at some time to within +- some number of meters or seconds. but even at the most precise level, quantum mechanics outright forbids perfect certainty in measurements of position and velocity. because of this the very core of quantum mechanics is statistical. when we calculate the "position of a particle" what we are calculating is something called an Expectation Value, which is thought of as an average of the results of completely independent and isolated measurements of identical experiments (a million grad students make identical measurements of position on a million identical experiments simultaneously. the expectation value for the position of a particle would be the average of these measurements.)

the statistical, non-deterministic nature of the universe can be directly seen by examining the decay rates of radioactive isotopes. given a single atom of U-238 it is impossible to predict with perfect certainty precisely when it will decay, because even if we could measure the exact position and momentum of every nucleon and electron in that atom at the same time, to do so would fundamentally change its state, and our measurements would no longer be valid. but we CAN produce predictions that tell us the likelihood that it will decay within some amount of time, and if you give me a very large sample of U-238 i can tell you about how many years it will be until some quantity of it decays.


I think this just speaks to our lack of ability to accurately measure/observe things without changing them. I find it hard to believe everything is only 'statistically' there. It might be IMPOSSIBLE for us to ever know the exact position/momentum of every particle... but there is still some fundamental reason these particles are where they are, and even if we'll never know... there IS a cause/effect reason for it, isnt there?

This would be more of a thought experiment then a real science experiment i guess

But lets assume we aren't measuring or observing anything at all. All of these particles are still bumping into each other in a Cause/Effect system... even if we cant currently measure, observe, or understand why or how they do it. There must be some reason a particle appears in one location rather then the other.

If we could look at the universe through the eyes of a God and freely observe without changing anything, wouldn't we see a predictable chain of events, all springing from that initial 'Big Bang'? Wouldn't the initial conditions of that event basically 'set up' the entire chain of cause/effect events from that moment all the way forward through time?

(I think the new popular theory is string theory branes bumping into eachother? =P)

I believe that science as it is requires Causality. And Free Will directly conflicts with Causality. I don't think the two can co-exist.

BTW i'm not religious at all, i consider myself agnostic. This is just something thats been puzzling me for years. I obviously have no scientific training, but i get lost on wikipedia from time to time =P



the Heisenberg uncertainty principle has absolutely nothing to do with the state of our technological ability to make measurements. it is a result of the fundamental nature of matter in our universe. you can have as much trouble as you like trying to "believe" in the quantum statistical nature of the universe, but the evidence is there for all to see.

now, yes, our universe appears to be bound by the law of causality, but you must understand that there is a distinct difference between observing the consequences to this a priori and a postiriori. yes, we exist the way we do today because of the interactions of particles throughout the lifetime of the universe, and yes, the way we will exist in the future will depend on how said particles interact now. but what i am trying to tell you is that, based on our current knowledge, it is fundamentally impossible to predict these interactions before they happen with absolute certainty at a quantum mechanical level. the farther ahead in time we try to predict the outcome of a series of events, the less certain we become of the results. to our knowledge it is impossible to completely determine the future state of the universe with perfect precision based on its current and past states.

as for your statement about "looking at the universe through the eyes of god" i cannot possibly make a meaningful, scientific comment. by the mere statement that such an observational frame exists you have already assumed your conclusion, that the universe is deterministic, and therefore concluded your assumption...
Terminal Insanity
KarmaFleet
Goonswarm Federation
#322 - 2012-03-12 23:36:49 UTC  |  Edited by: Terminal Insanity
Tsadkiel wrote:

the Heisenberg uncertainty principle has absolutely nothing to do with the state of our technological ability to make measurements. it is a result of the fundamental nature of matter in our universe. you can have as much trouble as you like trying to "believe" in the quantum statistical nature of the universe, but the evidence is there for all to see.



How do we know its not our technology? Even if its impossible to build the technology (because what its built of is the same stuff we're trying to measure?) The Uncertainty principal to me says that because we measure its momentum, we're changing its position. And if we measure its position, we change its momentum. But what if we could measure these without effecting it. Wouldn't that eliminate the Uncertainty principal? Or at least blame it on the inability of technology to properly measure the particle?

What makes us so certain of this uncertainty? =p

Reading about Einstein's Slit experiment...
Quote:
Bohr's response was that the wall is quantum mechanical as well, and that to measure the recoil to accuracy the momentum of the wall must be known to this accuracy before the particle passes through. This introduces an uncertainty in the position of the wall and therefore the position of the slit equal to , and if the wall's momentum is known precisely enough to measure the recoil, the slit's position is uncertain enough to disallow a position measurement.

And Einstein's Box...
Quote:
Bohr spent a day considering this setup, but eventually realized that if the energy of the box is precisely known, the time at which the shutter opens is uncertain.


It seems to me Bohr is still assuming his theory is correct and applying it to the wall+slit or the Shutter+Box+Timer used to measure it. But how can we apply his theory to the experiment like that when we haven't even proved it yet?

Now im sure there's something I, or wikipedia is missing. I'm just not sure =P

If this is indeed a fundamental fact of nature, i guess that does leave some room for the possibility of free will


edit; I think i may have found my answer, but i dont quite understand exactly what its saying yet. I'll have to reread it a few times, and its a big one
http://www.nature.com/ncomms/journal/v2/n8/full/ncomms1416.html
I'm supprised how recent this is, too

"War declarations are never officially considered griefing and are not a bannable offense, and it has been repeatedly stated by the developers that the possibility for non-consensual PvP is an intended feature." - CCP
Sumiragi
Viziam
Amarr Empire
#323 - 2012-03-13 01:09:59 UTC
Tsadkiel wrote:
Sumiragi wrote:
So the other night I needed to grab my keys from my bedroom. It was dark so I switched on the light to find them. Leaving the room, I flipped the switch and left.
My question to you is, when I flipped the switch off where did the light go?


so, you turn on your light, and billions of trillions of photons go screaming away from your light bulb! they bounce off the walls of your room and the objects it contains. as long as the light is on, photons continue to be emitted. a very small percentage of them are absorbed by your eye which you then perceive as sight. the rest bounce around until they are either absorbed by local materials (walls and objects, but also gasses!), or they escape from your room, home, planet, etc... this all happens in less than a blink. as a rule of thumb, light travels at about a foot per nanosecond in a vacuum, so unless your room is astronomically large (in a very literal sense), you will not be able to see any of this with your naked eyes.


A very genuine Thank you...I've actually had this thought for many years and no-one has been able to give me an answer, let alone an answer I can actually follow and understand.

Sir, I take my hat off to you.
Tsadkiel
Aliastra
Gallente Federation
#324 - 2012-03-13 02:19:21 UTC
Terminal Insanity wrote:
Tsadkiel wrote:

the Heisenberg uncertainty principle has absolutely nothing to do with the state of our technological ability to make measurements. it is a result of the fundamental nature of matter in our universe. you can have as much trouble as you like trying to "believe" in the quantum statistical nature of the universe, but the evidence is there for all to see.



How do we know its not our technology? Even if its impossible to build the technology (because what its built of is the same stuff we're trying to measure?) The Uncertainty principal to me says that because we measure its momentum, we're changing its position. And if we measure its position, we change its momentum. But what if we could measure these without effecting it. Wouldn't that eliminate the Uncertainty principal? Or at least blame it on the inability of technology to properly measure the particle?

What makes us so certain of this uncertainty? =p

Reading about Einstein's Slit experiment...
Quote:
Bohr's response was that the wall is quantum mechanical as well, and that to measure the recoil to accuracy the momentum of the wall must be known to this accuracy before the particle passes through. This introduces an uncertainty in the position of the wall and therefore the position of the slit equal to , and if the wall's momentum is known precisely enough to measure the recoil, the slit's position is uncertain enough to disallow a position measurement.

And Einstein's Box...
Quote:
Bohr spent a day considering this setup, but eventually realized that if the energy of the box is precisely known, the time at which the shutter opens is uncertain.


It seems to me Bohr is still assuming his theory is correct and applying it to the wall+slit or the Shutter+Box+Timer used to measure it. But how can we apply his theory to the experiment like that when we haven't even proved it yet?

Now im sure there's something I, or wikipedia is missing. I'm just not sure =P

If this is indeed a fundamental fact of nature, i guess that does leave some room for the possibility of free will



the Uncertainty Principle arises directly from the mathematics of quantum mechanics. it was predicted mathematically and then its effects were measured experimentally. in fact, you can derive an uncertainty relation for two, non commuting quantum mechanical operators. just as there is a position-momentum uncertainty relation, there is an energy-time uncertainty relation, and an uncertainty relation between two orthogonal angular momenta. nothing in the mathematics makes any assumption as to the devices or methods used to do the measuring.

the other thing is that you seem to be mixing two separate principles of quantum mechanics. the act of changing a system by measuring it is called the Copenhagen Interpretation of quantum mechanics. the inability to simultaneously measure a particles position and momentum to perfect certainty is the Heisenberg Uncertainty principle. i may have lent to some of this confusion earlier by using the Copenhagen interpretation in my discussion of the quantum statistical nature of the universe. these are two different things. the uncertainty in Heisenberg's principle is not a result of the Copenhagen interpretation.

the two experiments that you are referencing are thought experiments proposed by Einstein (who was fervently against quantum mechanics). such thought experiments are used in science to attack the weaknesses of a theory or hypothesis, and the idea is that if the theory or hypothesis can defend such arguments in a non ad-hoc manner, then it does so. these are tools used to refine scientific reasoning.
Khellendrose
Perkone
Caldari State
#325 - 2012-03-14 11:22:08 UTC
Define and give examples in no less than 50 words of Xenophobic Expansionism
Tsadkiel
Aliastra
Gallente Federation
#326 - 2012-03-14 15:36:32 UTC
Khellendrose wrote:
Define and give examples in no less than 50 words of Xenophobic Expansionism


i have no real understanding of what that is... the words themselves explain it a bit i think. xeno, "alien?" phobic "fear" expansionism... so maybe it's a country that expands its boarders out of fear of its neighbors? i'm really quite terrible at history so i can't think of any examples off the top of my head. sorry!
Elirel
Alpha.Tech
#327 - 2012-03-14 16:05:16 UTC
Khellendrose wrote:
Define and give examples in no less than 50 words of Xenophobic Expansionism


USA
Professor Alphane
Les Corsaires Diable
#328 - 2012-03-14 18:22:02 UTC
Now this is based on something I saw on QI and may or may not be true.

Speed of light can be slowed by passing the beam through other materials (bromine or bromide sounds familiar).

Given this and given we do not really know the 'consitancy' of space, how do we know what the universe really looks like , AFAIK all our assumptions are based on the speed of light being constant ?

A.

[center]YOU MUST THINK FIRST....[/center] [center]"I sit with the broken angels clutching at straws and nursing our scars.." - Marillion [/center] [center]The wise man watches the rise and fall of fools from afar[/center]
Tsadkiel
Aliastra
Gallente Federation
#329 - 2012-03-14 19:58:15 UTC
Professor Alphane wrote:
Now this is based on something I saw on QI and may or may not be true.

Speed of light can be slowed by passing the beam through other materials (bromine or bromide sounds familiar).

Given this and given we do not really know the 'consitancy' of space, how do we know what the universe really looks like , AFAIK all our assumptions are based on the speed of light being constant ?

A.


this question actually gave me pause. i was going to try and quote empirical evidence for the geometry of the universe that did not rely on our current cosmological models, and therefore the speed of light, but i couldn't (at least not off the top of my head)! if we ever gain the ability to travel astronomical distances easily, the measurement of spacial geometry becomes trivial. simply travel vast distances and make three turns. if you are able to return to your initial location by making only 90 degree turns, then the universe is "closed" (spherical. like drawing a large triangle over the surface of the earth). if you can return to your initial position and the angle of the turns add up to less than 180 degrees, then the universe is "open" (saddle shaped, like trying to draw a triangle inside of a large bowl). if you return to your initial position and the angles of your turn add up to exactly 180 degrees, then the universe is "flat" (like drawing a triangle on a piece of paper).

on another note, the speed of light is different in all mediums when compared to a vacuum =D in water it is approximately 33% slower, and we can get this directly from the refractive index, n. the refractive index is defined as the ratio between the speed of light in a vacuum, c, and the speed of light in a material, V. we can measure n from a simple geometric examination of how light bends in a given material, and yes, this is somewhat of a simplification (there are wavelength effects as well) but the point is

matter slows light down.

the universality of c can be seen directly from classical electrodynamics. i think i wrote about this in an earlier post, which was to answer a similar question.

hope this helps!

T.
God's Apples
Wilderness
IIIIIIIIIIIIIIIIIIIIIIIII
#330 - 2012-03-15 02:50:52 UTC
Elirel wrote:
Khellendrose wrote:
Define and give examples in no less than 50 words of Xenophobic Expansionism


USA


Beat me to it.

"Hydra Reloaded are just jealous / butthurt on me / us because we can get tons of PVP action in empire while they aren't good enough to get that." - NightmareX
T'san Manaan
Brutor Tribe
Minmatar Republic
#331 - 2012-03-15 16:41:43 UTC
Didn't read everything as it was making my head hurt so if this was covered sorry. I got excited to read the OP as I have a question that has been bothering me for a while.

If the universe is constantly expanding what is it expanding into and why can't we see what it is expanding into?
Tsadkiel
Aliastra
Gallente Federation
#332 - 2012-03-15 20:16:09 UTC  |  Edited by: Tsadkiel
T'san Manaan wrote:
Didn't read everything as it was making my head hurt so if this was covered sorry. I got excited to read the OP as I have a question that has been bothering me for a while.

If the universe is constantly expanding what is it expanding into and why can't we see what it is expanding into?


no worries =D i wrote about this on post #196 on page 10 of this thread. the long and short of it is that the term "expanding" is somewhat misleading. it's more like the universes "unit of measure for distance" is increasing. this IS a good question though. when i took my first cosmology class it gave me no end of headaches heheh.
Kehro Urgus
University of Caille
Gallente Federation
#333 - 2012-03-15 23:56:16 UTC
This is more about geophysics but I was very bored one day reading Wikipedia and stumbled across one article where it stated gravity is slightly stronger when moving east to west (or vice-versa... I can't remember) and it never offered an explanation why. I can't remember the subject of the article. I vaguely remember looking up the Coriolis effect.

I thought it was very strange and I couldn't really figure out why this is true. Only thing I can think of is if one is travelling west the earth's surface rises underfoot ever so slightly due to earth's curvature and rotation but I have my doubts whether it's a valid explanation.

Yeeee! 
Killer Gandry
The Concilium Enterprises
#334 - 2012-03-16 01:22:35 UTC
There is a theory that at the moment a large part of the Universe ( I think it was around 75-60%) consists out of Dark Matter.

This might be a reason as of why our Universal expansion rate keeps increasing instead of the expected decreasing rate which would resolve in the Big Implosion.

However if Dark Matter is the reason the Universe might be keeping on expanding at an increasing rate might this also not hold true on micro level at an linear rate?

Also if Dark Mattr is one of the main reasons the Universe is on an increasing expansion rate, then why doesn't the expansion rate drop anyways since this would involve more Dark Matter comming into existense to keep the expansion rate increasing.
How and why does Dark Matter seem to increase

A: Universal expansion rate
B: Why don't we see a decline in the expansion velocity anyways or does Dark Matter create more Dark matter? Is there a theory about that?
C: If Dark Matter is really around 75-80% of the known Universe, wouldn't that also open up the theory that this matter is also present in solid forms on a very microscopic level. If so what effects would those have.


Appologies for my poor english.
Professor Alphane
Les Corsaires Diable
#335 - 2012-03-16 13:25:35 UTC
Tsadkiel wrote:
Professor Alphane wrote:
Now this is based on something I saw on QI and may or may not be true.

Speed of light can be slowed by passing the beam through other materials (bromine or bromide sounds familiar).

Given this and given we do not really know the 'consitancy' of space, how do we know what the universe really looks like , AFAIK all our assumptions are based on the speed of light being constant ?

A.


this question actually gave me pause. i was going to try and quote empirical evidence for the geometry of the universe that did not rely on our current cosmological models, and therefore the speed of light, but i couldn't (at least not off the top of my head)! if we ever gain the ability to travel astronomical distances easily, the measurement of spacial geometry becomes trivial. simply travel vast distances and make three turns. if you are able to return to your initial location by making only 90 degree turns, then the universe is "closed" (spherical. like drawing a large triangle over the surface of the earth). if you can return to your initial position and the angle of the turns add up to less than 180 degrees, then the universe is "open" (saddle shaped, like trying to draw a triangle inside of a large bowl). if you return to your initial position and the angles of your turn add up to exactly 180 degrees, then the universe is "flat" (like drawing a triangle on a piece of paper).

on another note, the speed of light is different in all mediums when compared to a vacuum =D in water it is approximately 33% slower, and we can get this directly from the refractive index, n. the refractive index is defined as the ratio between the speed of light in a vacuum, c, and the speed of light in a material, V. we can measure n from a simple geometric examination of how light bends in a given material, and yes, this is somewhat of a simplification (there are wavelength effects as well) but the point is

matter slows light down.

the universality of c can be seen directly from classical electrodynamics. i think i wrote about this in an earlier post, which was to answer a similar question.

hope this helps!

T.


Wow I think I might of actually stumped you with that one. How about we try this little twist on the theory

If matter slows light

taken to it's nth degree matter STOPS light.

Given thats is the edge of the universe as you see it merely the edge of the 'visible' univerese given the length of a beam of light is not infinite.

Beyond the 'edge' you see nothing as no (photon) light reaches you from that space.

This might also explain the fact people seem to believe there is more mass in the univerese than there should be (hence the dark matter theory) .

It's possible that because gravity is an interaction beween 2 objects and not an energy packet you would still see the gravitational effect upon bodies you can see from bodies you cannot because of photonic decay (for want of a better phrase)

What do you reckon?


[center]YOU MUST THINK FIRST....[/center] [center]"I sit with the broken angels clutching at straws and nursing our scars.." - Marillion [/center] [center]The wise man watches the rise and fall of fools from afar[/center]
Professor Alphane
Les Corsaires Diable
#336 - 2012-03-17 10:17:50 UTC
Sorry perhaps I went to far , I hope I haven't offeded you.

It was just a logic game to me but I later realised this does sort of challenge some of the fundamentals in a totally unporavable way , these fundametals are most likely 'proved' in maths ( a form that is beyond my comprehesion currently) and far beyond my rather childish 'If X , why Y?' post.

Thanks for your time and effort in this thread though it has been frankly fascinating.

A.

[center]YOU MUST THINK FIRST....[/center] [center]"I sit with the broken angels clutching at straws and nursing our scars.." - Marillion [/center] [center]The wise man watches the rise and fall of fools from afar[/center]
Amaroq Dricaldari
Ministry of War
Amarr Empire
#337 - 2012-03-18 11:16:29 UTC  |  Edited by: Amaroq Dricaldari
Schrodinger's Cat. Is he dead, alive, or a clone?

This is my signature. There are many like it, but this one is mine.
Tsadkiel
Aliastra
Gallente Federation
#338 - 2012-03-19 15:50:15 UTC
Professor Alphane wrote:
Tsadkiel wrote:
Professor Alphane wrote:
Now this is based on something I saw on QI and may or may not be true.

Speed of light can be slowed by passing the beam through other materials (bromine or bromide sounds familiar).

Given this and given we do not really know the 'consitancy' of space, how do we know what the universe really looks like , AFAIK all our assumptions are based on the speed of light being constant ?

A.


this question actually gave me pause. i was going to try and quote empirical evidence for the geometry of the universe that did not rely on our current cosmological models, and therefore the speed of light, but i couldn't (at least not off the top of my head)! if we ever gain the ability to travel astronomical distances easily, the measurement of spacial geometry becomes trivial. simply travel vast distances and make three turns. if you are able to return to your initial location by making only 90 degree turns, then the universe is "closed" (spherical. like drawing a large triangle over the surface of the earth). if you can return to your initial position and the angle of the turns add up to less than 180 degrees, then the universe is "open" (saddle shaped, like trying to draw a triangle inside of a large bowl). if you return to your initial position and the angles of your turn add up to exactly 180 degrees, then the universe is "flat" (like drawing a triangle on a piece of paper).

on another note, the speed of light is different in all mediums when compared to a vacuum =D in water it is approximately 33% slower, and we can get this directly from the refractive index, n. the refractive index is defined as the ratio between the speed of light in a vacuum, c, and the speed of light in a material, V. we can measure n from a simple geometric examination of how light bends in a given material, and yes, this is somewhat of a simplification (there are wavelength effects as well) but the point is

matter slows light down.

the universality of c can be seen directly from classical electrodynamics. i think i wrote about this in an earlier post, which was to answer a similar question.

hope this helps!

T.


Wow I think I might of actually stumped you with that one. How about we try this little twist on the theory

If matter slows light

taken to it's nth degree matter STOPS light.

Given thats is the edge of the universe as you see it merely the edge of the 'visible' univerese given the length of a beam of light is not infinite.

Beyond the 'edge' you see nothing as no (photon) light reaches you from that space.

This might also explain the fact people seem to believe there is more mass in the univerese than there should be (hence the dark matter theory) .

It's possible that because gravity is an interaction beween 2 objects and not an energy packet you would still see the gravitational effect upon bodies you can see from bodies you cannot because of photonic decay (for want of a better phrase)

What do you reckon?





no no! you didn't offend me at all! i just got side tracked, that's all. i'm not entirely sure i understand your question though... the idea of stopped light is somewhat nonsensical. light exists as a self propagating wave-particle, it MUST have a velocity. stopped light would just be a static electromagnetic field. stopped light in matter would then simply be a configuration of charges and currents that holds the energy carried by the initial photon.

as for dark matter being the result of matter out beyond our field of view (this is the "surface" of the cosmic microwave background), i can certainly say this isn't the case. we can directly observe the changed trajectories of objects in the universe in the presence of dark matter, and the effect is definitely local (circular and elliptical orbits, not hyperbolic).
Tsadkiel
Aliastra
Gallente Federation
#339 - 2012-03-19 15:56:39 UTC
Killer Gandry wrote:
There is a theory that at the moment a large part of the Universe ( I think it was around 75-60%) consists out of Dark Matter.

This might be a reason as of why our Universal expansion rate keeps increasing instead of the expected decreasing rate which would resolve in the Big Implosion.

However if Dark Matter is the reason the Universe might be keeping on expanding at an increasing rate might this also not hold true on micro level at an linear rate?

Also if Dark Mattr is one of the main reasons the Universe is on an increasing expansion rate, then why doesn't the expansion rate drop anyways since this would involve more Dark Matter comming into existense to keep the expansion rate increasing.
How and why does Dark Matter seem to increase

A: Universal expansion rate
B: Why don't we see a decline in the expansion velocity anyways or does Dark Matter create more Dark matter? Is there a theory about that?
C: If Dark Matter is really around 75-80% of the known Universe, wouldn't that also open up the theory that this matter is also present in solid forms on a very microscopic level. If so what effects would those have.


Appologies for my poor english.


no worries about your english, it's fine =D again, i wrote about the expansion of the universe on post #196 on page 10 of this thread. the rate of expansion of the universe has the same value on all scales. the reason why we don't "experience" it is because that rate carries an inverse factor of distance measured in megaparsecs! the energy that fuels this expansion is tentatively called Dark Energy and questions like "where do dark matter and dark energy come from?" are some of the biggest questions in modern cosmology. i am sorry to say that i cannot give any concrete answer to this because the scientific community is still trying to figure it out =D
Tsadkiel
Aliastra
Gallente Federation
#340 - 2012-03-19 16:19:12 UTC
Kehro Urgus wrote:
This is more about geophysics but I was very bored one day reading Wikipedia and stumbled across one article where it stated gravity is slightly stronger when moving east to west (or vice-versa... I can't remember) and it never offered an explanation why. I can't remember the subject of the article. I vaguely remember looking up the Coriolis effect.

I thought it was very strange and I couldn't really figure out why this is true. Only thing I can think of is if one is travelling west the earth's surface rises underfoot ever so slightly due to earth's curvature and rotation but I have my doubts whether it's a valid explanation.


an excellent question! what we experience on the surface of the earth as gravitational acceleration is actually the combined effect of multiple accelerations, the two greatest contributors of which are pure gravitational acceleration and centripetal acceleration. the total acceleration towards the center of the earth that an object feels is often referred to as the apparent or effective gravity. if you move with or against the rotation of the earth (east-west or west-east) you change your angular velocity and therefore your centripetal acceleration. this then also affects the effective gravity you experience. this change would only occur while you are moving.