# Static Earth and Time

1. Dec 20, 2012

### hauk2008

Question that's been boggling my mind all day lol.. If the Earth was completely static (Not spinning around its poles, the sun, the galactic center, or moving away from the center of the universe) would time still be measurable?

2. Dec 20, 2012

### Staff: Mentor

What does one have to do with the other?

3. Dec 20, 2012

Staff Emeritus
Sure. Mickey's big hand would still be on the twelve and his little hand would still be on the three. The operation of a mechanical watch doesn't depend on any of this.

4. Dec 20, 2012

### Staff: Mentor

Yes, through any number of means. Pendulums will still swing, radioactive materials will still decay at a predictable rate, sand will still flow through hourglasses, ....

5. Dec 20, 2012

### hauk2008

Hmm... fair enough. I guess I was thinking about the passage of time in the wrong way. I'm still confused about how the concept of time would be realized if there was no set pattern to observe. Like if I didn't have a watch, or some other repeatable event that could be tested. I feel like I'm not using the correct words for this lol...

Anyone have a basic example of how time can be explained? I'm no physicist, but have a pretty good understanding on the general stuff.

6. Dec 21, 2012

### manojr

From wikipedia: Some simple, relatively uncontroversial definitions of time include "time is what clocks measure" and "time is what keeps everything from happening at once.

I think you are asking whether time is absolute/eternal i.e. it existed forever, regardless of existence of matter (earth/galaxies/observer). No, it is not. Space and time were born around 13.5 billions years ago at event called as big bang. Clocks run (time flows) slowly near gravity well or if clock is in motion w.r.t. observer.

7. Dec 21, 2012

### Staff: Mentor

There is no center of the universe. And there is no absolute velocity.

If you magically stop everything on earth, all clocks on earth will fail (as they are stopped). You could still measure time somewhere else.

8. Dec 21, 2012

### rashi

Clock is not the only mean to measure time, we could measurethe time by the motion of sun. Time is the interval between two events, we could measure time by the length of suration between two events.

9. Dec 21, 2012

### jbriggs444

That just begs the question doesn't it? How do you measure the length of the duration between two events?

10. Dec 21, 2012

### rashi

By the size of the moon, by the positon of the sun etc...

11. Dec 21, 2012

### xAxis

There wouldn't be measurable motion of the sun. Concept of time would probably be tied to a moon motion.

12. Dec 21, 2012

### jbriggs444

Even if the moons did not move, time would still be reckoned.

For instance:

http://chestofbooks.com/travel/holland/John-Stoddard-Lectures/Holland-Part-3.html

"Water Barges.

The Hollanders are inveterate smokers. The boatmen, it is said, measure distances by smoke and reckon, not so many miles from place to place, but so many pipes."

13. Dec 21, 2012

### rashi

Believe me in some culture people still using position of shadow caused by Sun. This is the most common practice t predcit the paryer time. you may be aware of the fasting month, there is sun can be used as time clock.

14. Dec 21, 2012

### phinds

Absolutely true but utterly irrelevant to the original question, under the conditions of which the sun could NOT be used as a clock, nor could any such movements because they are specifically stated in the question as being static. THEN how do you measure time? The question has been answered, but I think you have misunderstood it.

Last edited: Dec 21, 2012
15. Dec 21, 2012

### Staff: Mentor

If you're looking for a "nothing that moves anywhere" clock.... Start with equal-sized samples of two different radioactive materials with different half-lives. The ratio of their amounts will change in a predictable way as time passes.

16. Dec 22, 2012

### rashi

Ok, Guys I recieved two warning messages becuase I posted my own Opinion. I shall respect the rules of the forum and will not put my personal opinion any more!

17. Jan 19, 2013

### rashi

Figure 1 shows a type of apparatus for investigating the speed distribution f (v) of molecules in a gas. Molecules emerge into a vacuum chamber from an oven held at a constant temperature T, and are collimated by slits into a parallel beam directed towards a pair of discs rotating at a common angular speed ?, which may be varied. The discs are a fixed distance L apart (L = 262 mm) and contain narrow notches, with the second notch offset from the first by a fixed angle ? = 30° as shown. If a molecule is moving at the correct speed v, it will pass through the notches in both discs to be collected at the detector, which records the rate of arrival of molecules. detector .

(a) The oven contains aluminium at 9.00 × 102 °C, which emerges as a monatomic beam. Calculate the speed vmp and the corresponding rotation speed ? at which the largest rate of arrival for aluminium atoms is observed. (The molar mass of aluminium is 0.0270 kg mol?1.)

I want to post this question in My PF but can not find the option.

Steps I follwed to sole is these thwo formula
1) Square V= 3 RT/2M, can you please tell em if i am using the right formula and how this can be derived?

18. Jan 19, 2013

### Buckleymanor

There would be allways something that moves otherwise you could not observe.

19. Jan 20, 2013