Eastern Railroad Discussion > GRAVITY vs the sun ???

How much effect does the gravitational pull have on trains as the earth rotates around the sun.And is it different in the summer compared to the winter.Also with the earths rotation do east bound trains pull easyer than westbound trains ??? thanks in advance scoob

scoobydoobydoo Wrote:
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> How much effect does the gravitational pull have
> on trains as the earth rotates around the sun.

It's what keeps the trains on the tracks. Without it, they'd be spacecraft.

I'm not a physicist, but I can't imagine that the earth's position relative to the sun has a significant gravitational effect on objects on the earth's surface, be they trains, buildings, or people. While the earth's distance from the sun varies somewhat during the course of the year, this does not even have relevance to the change of seasons, much less gravity. If there were varying gravitational effects from the sun, such effects would not show any differential concerning a train's direction of travel -- the sun is simply too far away to do that.

A more substantial influence on the earth is that of the moon, which as we well know causes ocean tides. As the earth rotates, its shape is slightly distorted by the moon's gravitational pull, and that causes the tides to rise and fall. The moon's orbit is not exactly circular, either, and at times when the moon is closer to the earth, its gravity makes the tides more extreme. In that regard, the moon's gravitational effect would contribute to any flood damage a railroad might incur from an exceedingly high tide. But even then, we don't hear engineers talking about how "That eastbound pull up Beaumont Pass is more difficult tonight because of the full moon."

One scientific clarification: the Earth REVOLVES around the sun, it ROTATES on its axis. The reason for the change of seasons is that the axis is tilted, so that the spin is not "level" in relation to the planet's orientation to the sun, and thus the amount of sunlight per day at a given latitude changes during the course of each revolution around the sun.

And remember it was proved hundreds of years ago that gravity affects ALL things equally. If wind resistance is not a factor (as with a feather) a marble and a cannonball fall and hit the ground at the same time. To quote Robert Heinlein who was quoting yet another; "A pint is a pound the world around."

I would also suggest that it might be shown that there is some tiny effect generated by the direction of travel, provided it is vaguely west or east, but that effect is not greater or less than that effect on all things capable of motion. Beyond that such effect is moot, for we move on the plane we occupy, and the dynamics of such movement are relative to the motion of the plane itself. Consult Einstein's writings for more on this.

The force of attraction bewteen two objects is related to the mass of those objects. The mass of a marble, a bowling ball, or even a Dash 9, is so insignificant compared to the mass of the earth, that it's part in the equation is ignored, and only the attraction caused my the mass of the earth (the force of gravity) is measured.

Where the heck you get this stuff????

The sun's gravitional effect on the earth is noticable (spring

tides are an example) but miniscule.

You may wish to check our astronomy club's website for links

to an explanation.

www.3ap.org

Be Well,

Tim K3HX

ddavies Wrote:
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> The force of attraction bewteen two objects is
> related to the mass of those objects. The mass of
> a marble, a bowling ball, or even a Dash 9, is so
> insignificant compared to the mass of the earth,
> that it's part in the equation is ignored, and
> only the attraction caused my the mass of the
> earth (the force of gravity) is measured.


So thickens the soup...each thing with mass also exerts its own gravitiational force, the amount dependent on how much mass, but as you said, compared to the Earth, (or the estimable force of the moon and sun) any earthbound mass will have such small gravity of its own, as to be neglible. So I think it's safe to answer the original question this way......."no effect worth consideration"

The effect of gravity is the same from the sun and the moon. The distance is the factor. The moon is closer than the sun and the tidal attraction is actually the same.

As to the rolling resistance or lack there of due to the rotation of the earth: The train is moving over the surface and is relative. Here on the 40th N. parallel we are moving eastward about 700 mph relative to the stars when standing still. So moving east at 60 mph over the ground is 760 mph to the stars. You are only overcoming the resistance of the train on the track. Gravity has 0 effect unless we are talking going up a hill. Rotation hase nothing to do with garvity. Gravity is mass based not rotation based. If the earth stopped spinning the gravity would still be the same.

We launch rockets from Florida to get the boost of about 1000 mph and this is related to effort to getting into orbit. It takes more effort to go to the space station (50+ degrees to the equator) than to the orbit of the Hubble ( about 23 degrees to the equator) telescope. It takes even more to go in a polar orbit (90 degrees to the equator).
Dan, planetarium dir. in my spare time 8+)

Boy, this is turning out to be even more educational than I thought. I did not realize that the sun's gravitational influence on Earth was roughly the same as the moon's. I suppose the reason the moon's would SEEM to be greater is that its position vis Earth changes more rapidly than does the sun's and thus the lunar tidal effects are more obvious. (I had also thought that "spring tide" was a misnomer applicable to all extreme tides occurring when the moon is closest to Earth.)

Certainly what we all agree upon is that extraterrestrial gravity is not strong enough to measurably affect the motion of a train or any other earthbound object.

"If the earth stopped spinning the gravity would still be the same."

Not quite. The centrifugal "force" is appreciable. As you know, "gravity" is a half-percent less at the equator than at the pole, and I think the earth's spin is the main reason for that.

Here comes a theory of relativity question.

Had this one in college just changed car to SD 70 for the sake of this forum.

How fast does an SD 70 have to travel to fit totally within a 10' long tunnel? Meaning if you looked at the tunnel from the side the SD 70 would totally disappear within the tunnel.

My answer on the exam was, "Faster than a CAR will ever travel!"

I understood every reply except for this one...

I think you left some variables out.

Matt

cjvrr Wrote:
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> Here comes a theory of relativity question.
>
> Had this one in college just changed car to SD 70
> for the sake of this forum.
>
> How fast does an SD 70 have to travel to fit
> totally within a 10' long tunnel? Meaning if you
> looked at the tunnel from the side the SD 70 would
> totally disappear within the tunnel.
>
> My answer on the exam was, "Faster than a CAR will
> ever travel!"

A Ford Festiva or Geo Metro might fit. Err, I mean...a GE 44-tonner...yeah! ;-)

--Dan

"Not quite. The centrifugal "force" is appreciable. As you know, "gravity" is a half-percent less at the equator than at the pole, and I think the earth's spin is the main reason for that."

The amount of mass does not change therefore the gravity is the same.

There is a bulge at the equator caused by the rotation of the earth and the gravitational acceleration is slightly lower at the equator as you state. But most folks think that the rotation causes gravity. Just look at some of the answers I get on some of my astronomy tests.


Spring tides are at full and new moon phase and neap tides are at the quarter phases. The astronomical high tides are when the full and new phase coincide with closest approach of the moon. The January alignment would be the most extream when the moon is closest to the earth and the earth is closest to the sun, which occurs in early January. Throw in a storm surge and you have a problem!


Ast. 101 now over.

Pending I can remember my rusty physics and use Google to come up with a few constants correctly...

SD70M - 2.96 x 10^8 meters / sec should get your coupling faces just inside the tunnel portals. Basically a fraction of a percent under the full speed of light.

It would also weigh almost 3 million pounds to a "stationary" observer and the amount of energy it would take to get the SD70M to that speed would be astronomical. (Astronomical being a synonym for Nathan doesn't remember how to do relativistic momentum stuff...)

If we just assume an average mass across the entire acceleration of 1.5 million pounds and ignore all the relativity stuff, (forgive the mixing of SI and imperial units) then it would take roughly 6 x 10^25 joules. To give you some idea, that's the total power output of the unit for 1.6 trillion years. Or, if you just have 224 billion nuclear weapons the size of the large hydrogen device tested on Bikini Atoll in 1954, and could impart all of the released energy as forward momentum on the SD70M, you could also do the job.

Nathan
http://www.drgw.net

Rotation of the earth around it's axis has an effect. The centrifugal force makes a slight difference. A man who weighs 200 pounds at the equator will weigh 201 if he goes to the north pole.
That's the reason NASA launches rockets from southern Florida.
The MASS of your train will be the same, if it goes North - South, but the weight will actually lighten up as the train goes further south.
There is no effect, or difference, east-west, as your question was worded.

I knew someone would answer it. Thanks!

Hi!

> SD70M - 2.96 x 10^8 meters / sec should get your
> coupling faces just inside the tunnel portals.
> Basically a fraction of a percent under the full
> speed of light.


An observer on the ground would note that
a SD70M going at near light speed would
be either red or blue, depending on the
direction of travel either directly toward
or away. At other observation angles the
engine would be one of the other colors.
So, since all engines are either red, blue
or another color, we can therefore prove
that all engines move near the speed of
light...

Tony Burzio
San Diego, CA