Interesting Physics

[inocente]

i considered that and it worried me a lot that i have to use somebody else’s measurement of the radius of the earth. assuming they are wrong i can blame them. i will try to correct this uncertainty by measuring the radius of the earth myself, (in my spare time).

I think the way to deal with it is first get measurements made by various teams, discarding any which are wildly different from the others. Then do the calculation using the smallest measurement you have kept, then again using the largest, which will give you the error range. I’d guess also that the radius is bigger at the equator than at the poles due to the Earth spinning.

 

[ProVobis]

btw this kind of calculation should always include ± X to show the uncertainty in the measurements you used, otherwise you could end up with a spurious accuracy.

Indeed. That’s the way we were taught. I usually found I underestimated the uncertainty.

 

[You]

the thing about uncertainties is that you don’t know what they are. theres also a philosophical problem in never being wrong.

 

[Vico]

Are Americans required by federal law to never make up your mind which units to use?
…

Legislation required most federal agencies to use metric system by 1992 but did not mandate metric for private use. Also highway and construction industries are exempted. The USA allows private choice of units.

 

[ProVobis]

Legislation required most federal agencies to use metric system by 1992 but did not mandate metric for private use. Also highway and construction industries are exempted. The USA allows private choice of units.

They tried using it in sports, such as baseball, without much success. I mean who wants to see distances measured in other than feet and with 2 decimal places?

 

[Vico]

They tried using it in sports, such as baseball, without much success. I mean who wants to see distances measured in other than feet and with 2 decimal places?

Plus some people use the earlier metric CGS system rather than MKS system.

 

[thinkandmull]

Since this thread is about interesting physics, I have one in mind. Have you ever seen lights from cars come through the blinds? Well, not only will the lights on the wall from the cars move, but it looks as if the fence outside is moving with the cars as well; that is, the shadow of the fence will move. Why is that?

 

[Vico]

Since this thread is about interesting physics, I have one in mind. Have you ever seen lights from cars come through the blinds? Well, not only will the lights on the wall from the cars move, but it looks as if the fence outside is moving with the cars as well; that is, the shadow of the fence will move. Why is that?

The shadow of the fence is projected onto the blinds and the blinds admit only a portion of the fence shadow adding their own shadow.

 

[You]

that relativity problem, i don’t understand it.
theres a train, two people, and two lightning strikes.
the person on the train sees two strikes at different times. but the person on the ground sees two strikes at the same time.
a problem i see is that the first person sees light at different times so the light from one strike has travelled further (and lit up more ground around it).
but the other person, on the ground, for some reason cannot see this light and the new ground it has lit up, she can only see two strikes at the same time the light from neither strike has traveled as far as the light in the first case.

 

[thinkandmull]

The shadow of the fence is projected onto the blinds and the blinds admit only a portion of the fence shadow adding their own shadow.

The phenomenon I’ve seen is the shadow of the fence moving briskly on the wall, not just the light moving. It’s kinda neat