Velocity as a fundamental quantity.

In summary, time is a fundamental quantity that is measured by the change in position of objects. For example, a year is measured by one orbit of Earth and a day is measured by one rotation. Additionally, one second is defined as a certain number of cycles of radiation from a caesium atom. However, the concept of time being based on motion is not always convenient. Time is actually based on the change of state of a system, not just motion. This is evident in the measurement of a year, where the rate and direction of Earth's motion is not important, but rather the separation between two similar states. The debate on the fundamental nature of time often leads to a standstill, as there is no universal agreement on how to rank
  • #1
siddhukrish
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Time is a fundamental quantity. but we actually measure time with change in the position of objects. for example one orbit which Earth completes is a year. one rotation of Earth is a day, one second is defined as 9192631770 cycles of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium atom. so time is based upon on motion. why do have time as the fundamental quantity is it a convention or is there a reason for having time as a fundamental quantity?
 
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  • #2
The fact is that if an object doesn't change its position, the time continues go on because is a primitive concept. So this way of measuring time is not always very convenient...
 
  • #3
siddhukrish said:
we actually measure time with change in the position of objects.
siddhukrish said:
so time is based upon on motion.
No it's not. It's based on change of state of a system.

For example, in measuring a year you don't care about the rate of change and direction of velocity of Earth, which is anything but constant, but define it as a separation between two sufficiently similar states (e.g. when Earth is back to the 'same' position w/r to background stars).
Similarly, when talking about hyperfine transitions, the notion of motion doesn't even have much sense (there's nothing there with a measurable position or velocity). All that counts is that there exists a state the system periodically returns to.
 
  • #4
These threads never go anywhere, because there is no universal way to agree on how fundamental a quantity is. If we could say "Voltage is 5, but Velocity is 7", then maybe we could make some progress.
 
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1. What is velocity?

Velocity is defined as the rate of change of an object's position with respect to time. In simpler terms, it is the speed and direction at which an object is moving.

2. How is velocity different from speed?

Velocity and speed are often used interchangeably, but they are actually two different concepts. While speed only describes how fast an object is moving, velocity also takes into account the direction of motion.

3. Is velocity a fundamental quantity?

Yes, velocity is considered a fundamental quantity in physics. This means that it is a basic physical quantity that cannot be defined in terms of other quantities.

4. How is velocity measured?

Velocity is typically measured in units of distance per time, such as meters per second or kilometers per hour. It can be measured using various tools and techniques, such as radar guns or motion sensors.

5. What factors affect an object's velocity?

An object's velocity can be affected by several factors, including its mass, the force acting upon it, and any external forces such as friction or air resistance. Changes in these factors can cause an object's velocity to increase, decrease, or change direction.

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