"Straight Line"

It will be "AS THE CROW FLIES"

I'd think in a solution like this: two bent beams in the same way, if opposed and attached one to the other, would give you a straight beam!

Works really well when you're assemblying airplane models at least...

And, of course, a straight line could be straight in a determined direction at a time. Use your equipment to work aligned with the gravitational field. You'll end without gravity effects.

Please give me an example. Do you mean, for example, you cannot build a perfectly straight I-beam anywhere on Earth and not have at least some error due to gravity? I don't quite see the problem from a practical standpoint. Gravity is the weakest of the forces. We overcome it when we pick up a paper clip. In theory though, any unequal forces acting on an object will cause proportional distortion, however minor.

I'm not disputing anything, I'm just curious as to your perspective and I'm not an expert. Is it hypothetical using an infinitely long beam? Or can I use a 1" cube?

I wish you wouldn't ask questions like this because I get hooked every darn time.

Yeah... You may then ponder of Einstein's quote that nothing is ever at rest at any scale around us:

A train is running on it's rails, and an opposing bullet rushes to hit it smack in the front. It would of course, bounce off the train's front BUT, during the impact, as the bullet must reverse it's axial direction, there must be a phase, short as it may be, that it's axial velocity is zero. Can we assume that the bullet was able to stop the train, even for the briefest of moments?

(Not mine, This is the sort questions you could read of, in The New Scientist, during the nineties)

You are correct but, as demonstrated by Zeno's Paradox, it will be close enough to a perfectly straight edge for all practical purposes.

Hi James, you wrote: "If one was to design a perfectly straight edge, I say it would be impossible in a gravitational field."

"Straight edge" is a slippery concept! Once you machined a "straight edge", relative to what do you verify it?

Practically, the only inherently accurate method is to use light. Light also follows a "curved path" in a gravitational field, but for Earth, the radius of that curvature is about one light-year, ~10¹⁶ meters. So on terrestrial scales, the error is utterly negligible.

That is, if it is an "error" at all - maybe that is the definition of a straight line on our Terra Firma!

Regards, Jorrie

Jorrie-you are correct! The very equipment you would use to design a "straight line edge" would be at fault because one would have designed that very machine ina gravitional enviroment! As you have stated, light bends. All attempts would fail in the presence of gravity.

Jorrie-sorry about that! I forgot to login! Thanks for you input! James

Jorrie, I have been reading your responses now for a couple of months and find them very well written but when I add your writing style with your picture I come up with "007 James Bond" for some reason,,,,lol,,,,any relation perhaps?,,,,,just messin with you guy, have a good one,,,,Chuck

Hi sc6chuck9, I had one private mail telling me my avatar looks like his dad; now it also looks like 007 - which one? Looks like I'm well on my way to being famous!

Regards, Jorrie

Jorrie

Maybe you are an older James Bond... somewhat like Sean Connery

Bill

PS Do you know who said "James Bond!! I'd like to kill that son of a bitch!!"

Answer:Sean Connery

if your measureing device gave you a "false input" , How would you know it's false?

If we're looking for a way to confirm that gravity is not affecting the result too much here, doesn't pulling a piece of string tight work. A piece of 1 mm² carbon fibre will support about 200 Kg. : so when there's no practical difference between a line under say 200 N and 1000 N tension: then it's "straight".

Interesting theoretical problem. The best approach is to use gravity to solve it by using a water level. Two sticks pounded into the ground x feet apart from each other with duct tape holding a clear vinyl tube vertically onto the sticks. Then partially fill the tube with red colored water so that the water level is patially up on the sticks. The two water levels become two points on a straight line. To increase accuracy, spread the sticks apart further. Sorry for writing this
"see spot run" thing out but whomever wrote the question needed basic infromation.

Guest: your "The two water levels become two points on a straight line", and "Sorry for writing this "see spot run" thing out but whomever wrote the question needed basic infromation." makes no sense at all!

Can you explain how the equipment that you described can be used to find out if a "straight edge" is indeed straight! That was the question, IMHO...

SL

Why not use gravity in your favor?

In the case of light for example, point the light directly towards the origin of the force (gravity) and your deflection should be reduced at a minimum (if, of course, we dont take into account the rest of the gravitational forces around: sun, other planets, etc...)?

Rick.

why do people only work in 2d. upright (if there is such a thing) and gravity would work along the axis of your straight edge but taken down to atomic level atoms would not lie flat and move around so i surpose it would also have to be at 0 kelvin

Thanks to everyone for your responding to my question. I still believe ANYTHING you do here on earth to make any kind of "straight line" will fail! All measurements, including LASER light, will be "bent". Every thing we reference to has to include light. All matter, even down to the subatomic level, is influenced by gravity.