Friday, 28 August 2020

Length Contraction and Time dilation explained - special relativity ch.2

This is another interesting new science video from Science Loop on Youtube. This is the explanation of Special Theory of Relativity with Animation. It is the 2nd video of this Series. This video is about Length Contraction and Time dilation explained with simple animated videos.

This is pretty fascinating. Amazingly, Time Dilation explains why two working clocks will actually report different times after different accelerations. For example, at the ISS time goes slower, lagging approximately 0.01 seconds behind for every 12 earth months passed. For GPS satellites to work, they must certainly adjust for similar bending of spacetime to coordinate properly with systems on Earth.

Time dilation is really a difference in the elapsed time measured by two clocks, either due to them having a velocity relative to each other, or by there being a gravitational potential difference between their locations. After compensating for varying signal delays due to the changing distance between an observer and a moving clock (i.e. Doppler effect), the observer will measure the moving clock as ticking slower than a clock that is at rest in the observer's own reference frame. A clock that is close to a massive body (and which therefore is at lower gravitational potential) will record less elapsed time than a clock situated further from the said massive body (and which is actually at a higher gravitational potential).

Length contraction is the phenomenon that a moving object's length is measured to be shorter than its proper length, which is the length as measured in the object's own rest frame. Sounds illogical, but that's how it is. It is also known as Lorentz contraction or Lorentz-FitzGerald contraction (after Hendrik Lorentz and George Francis FitzGerald) and is usually only noticeable at a substantial fraction of the speed of light. Length contraction is only in the direction in which the body is travelling. For standard objects, this effect is negligible at everyday speeds, and can be ignored for all regular purposes, only becoming significant as the object approaches the speed of light relative to the observer.

The explanations about Length Contraction and Time dilation are interesting. It might seem like something is disobeying the laws of physics, but it's not.

There are interesting implications of special relativity:

That Fast moving object appear shorter
That Fast moving objects appears to have increased mass 
And finally, the most famous equation in science E=MC2
That mass and energy are equivalent.

In order for your car's GPS navigation to function as accurately as it does, satellites have to take relativistic effects into account. This is because even though satellites aren't moving at anything close to the speed of light, they are still going pretty fast. The satellites are also sending signals to ground stations on Earth. These stations (and the GPS unit in your car) are all experiencing higher accelerations due to gravity than the satellites in orbit.

To get that amazing pinpoint accuracy, the satellites use clocks that are accurate to a few billionths of a second (nanoseconds). Since each satellite is 12,600 miles (20,300 kilometers) above Earth and moves at about 6,000 miles per hour (10,000 km/h), there's a relativistic time dilation that tacks on about 4 microseconds each day. Add in the effects of gravity and the figure goes up to about 7 microseconds. That's 7,000 nanoseconds.

The difference is significant: if no relativistic effects were accounted for, a GPS unit that tells you it's a half mile (0.8 km) to the next gas station would be 5 miles (8 km) off after only one day.

Read interesting recent science news:

August 28, 2020 - New Proof Finally Affirms How Stars Get Devoured By Black Holes -

August 27, 2020 - Did a supernova cause the Devonian mass extinction event? -

August 26, 2020 - Researchers develop first controllable "walking" micro-robots -


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    1. The language was detected: Filipino

      Here are some translations: English to Filipino:

      believe - maniwala
      reunite - magsama ulit
      girlfriend - kasintahan
      alone - mag-isa
      stay - manatili
      lucky - masuwerte
      day - araw
      meet - magkita