8 word question

Classical Mechanics Level 2

How is a meter defined, as of 2015?

Image Credit: Flickr 6.5st .

\frac{1}{149597870700 }

of the distance from the Earth to the Sun The distance light travels in

\frac{1}{299792458}

seconds

\frac{1}{9.806}

of the length of a pendulum with period

2\pi

seconds on Earth The edge length of a cube of water that weighs

1000

kilograms at

4^\circ C

18897261329

times the radius of a hydrogen atom

3 solutions

Michael Mendrin
Jul 1, 2015

Currently. Every few decades, the definition of a meter changes. Originally, it was supposed to be 1/10,000,000 of the distance from the north pole to the equator.

I doubt very much the latest definition is the last word on the meter.

Scientists are probably gonna prove that in certain 'dimensions', the speed of light is variable.

Sharky Kesa - 5 years, 11 months ago

Here's the thing, physicists are already talking about the possibility that the speed of light isn't as constant as it's supposed to be. And then what?

Michael Mendrin - 5 years, 11 months ago

Einstein's wrong?

Sharky Kesa - 5 years, 11 months ago

@Sharky Kesa – You know, physics is not like the bible, where too many think either everything in it is perfect, literal, and inerrant, OR the bible is wrong and a fake. Einstein's theory of relativity showed that Newtonian physics needed an extra twist, and so future theories in physics that say that the speed of light isn't that constant would only be an extra twist on Einstein's works. Indeed, the entire history of theoretical physics is about one extra twist after another. To one used to the staid perfectionism of "pure mathematics", this seems too lawless, but many physicists think that's the whole fun of it.

Come to think of it, that might be why I listed "Physics" as an interest in my Brilliant.org profile.

Michael Mendrin - 5 years, 11 months ago

@Sharky Kesa – Even hawking mentioned in a book that he gets 2 letters every week saying that Einstein was wrong

Satvik Choudhary - 5 years, 11 months ago

the speed of light in vacuum is generally viewed as one of the fundamental constants of the universe, for it never changes under any circumstance.

Christian Prestiger - 5 years, 11 months ago

Here's a typical paper on the possibility of variable speed of light. There already have been many such papers on this subject, it's a lively field of study in physics.

New varying speed of light theories

Michael Mendrin - 5 years, 11 months ago

What does this mean?

Shreyansh Ajmera - 5 years, 10 months ago

@Alex Li It has become a 7 word question now. :3 :P

Nihar Mahajan - 5 years, 11 months ago

8 words.

Sharky Kesa - 5 years, 11 months ago

Yeah , if we include 2015 as a word.

Nihar Mahajan - 5 years, 11 months ago

Sharky, 2015 isn't technically a 'word' :3

Mehul Arora - 5 years, 11 months ago

2015 really represents 2 words, right?

Ashley Martin - 5 years, 10 months ago

Feathery Studio
Jul 7, 2015

Light travels at 299 792 458 m / s, so therefore it must travel a meter in $\frac{1}{299 792 458}$ s.

1 Joule = 1 N-m. You can then define metre as the work distance traveled by a body under 1 N Force when the work done becomes 1 Joule! You can't say justify you're Solution then.

Kishore S. Shenoy - 5 years, 8 months ago

Triga Fool
Jul 2, 2015

the definition will likely stay the same, even in variable light speed conditions. it only appears to move at rates unheardof in certain specific conditions. so we will only redefine how far this is, in what conditions, eg distance light travels in x seconds, in a vacuum in an L2 orbit

I'm 64, but I'm willing to bet that I'll live to see it changed once again. It's already changed THREE TIMES in my lifetime.

Michael Mendrin - 5 years, 11 months ago

What were the previous lengths?

Sharky Kesa - 5 years, 11 months ago

What I recall off the top of my head is that when I was a kid, there was some fantastic bar somewhere that was machined to a precise length that defined the meter. Then in 1960 they went with so many wavelengths of some transition radiation of Krypton. I remember that very well, because I used to read Superman comics, and as we know, Kryptonite radiation was deadly to Superman. Much later, I remember reading in Scientific America that the meter was defined by how fast light travels in a vacuum. I only just now learned about a refinement to this, saying that a meter shall be "a unit of proper length", which means general relativistic effects should be taken into consideration. This is news to me.

The differences between all are very tiny, it was more of a matter of consistency (repeatability) of measure, rather than deciding just how long a meter should be.

Michael Mendrin - 5 years, 11 months ago

8 word question

Image Credit: Flickr 6.5st .

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