Introduction for publication 5

This is the third part of modern physics – Time, Gravity, spacetime concept etc.

In case you have missed Publication 4, please review.

Publication 5

As I have said before, understanding modern physics requires complex mathematical equations. However, our understanding will be limited to a concept, philosophy, and postulates in this article.

Galileo and Newton both discovered important laws about gravity. Scientist started using mathematics to quantify the natural phenomenon.  Also, scientist verified experimentally the results from the mathematics.

The concept of time is old. Our elder said, “once the time is gone you will lose the time forever”. So you must do everything timely. The concept is, time-flow cannot vary. It is the classical time concept as defined by Sir Isaac Newton. Newton formulated this insight into a mathematical equation, known today as the law of universal gravitation. But do you know he did not know why gravity works like that way?

Sir Isaac Newton said “Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent is material or immaterial, I have left to the consideration of my readers. “

Several hundreds of years after the Principia (by Newton) were published, the world was still without an understanding of gravity’s mechanism.

In 1905 Albert Einstein published his Special Theory of Relativity. This work considered – time not as a single constantly flowing entity.  Special relativity says that any moving clock slows down relative to a stationary observer. This is true for all types of clock, such as digital watches, atomic clocks, and even our own biological clock.

This is time dilation as used by the theory of relativity. This is the difference in the elapsed time measured by two observers for an event.  When two observers moving at different velocity away from the event light will reach at the observers at the different time. This difference is time dilation.

This phenomenon is easy to comprehend.

But if two observers are situated at different gravitational force, not moving and at the same distance from the source of the event, still the time dilation happens. The speed of time flow is inversely proportional to the gravitational force.

This phenomenon is hard to comprehend.

The only way it can happen if time is affected by gravity.  This is a new concept. Time runs slower wherever gravity is strongest, and this is because of gravity curves space. WOW!

For higher gravitational potential that means the clock is further from the gravitational source, the faster time passes.  Atomic clocks, when placed at differing altitudes from the earth surface (and thus different gravitational potential), will eventually show different times.

A non–inertial reference frame is a frame of reference that is undergoing acceleration with respect to an inertial frame.  In a curved spacetime, all frames are non–inertial.

Einstein’s Two Postulates

a. Physical laws are the same in all frames of reference.

b. The speed of light is constant regardless of the speed of someone observing it.

If the speed of light stays the same then something else has to change. That “something” is time.

That is time dilation.

Maxwell’s equations predict a speed for electromagnetic waves. It doesn’t seem to depend on anything. Experiments were done (Michelson–Morley experiment) that showed that the speed of light is in fact NOT relative.

Other experimental prove:

Some of the experiments are done in atomic accelerators.

For example, the half-life of a free neutron is about 10 minutes once unbound from other particles. However, if accelerated to about 90% of the speed of light then the half-life of the neutrons increases to about 15 minutes, i.e. just as relativity dictates it should (their clocks are running slow).

The scientists watching and measuring this are stationary, relative to the accelerated neutrons, and so they do not experience dilation.

THE FOUR DIMENSIONS OF SPACETIME

Consider spacetime as four dimensions. The faster you travel through space, the slower you travel through time, and vice versa.

MOVING OBJECTS CONTRACT IN SPACE

Special relativity says that fast-moving objects appear to contract in size, in the direction of their motion. Those moving faster than you appear to contract in size (in the direction of their motion).

Effects of acceleration and gravity are indistinguishable.

In an object spinning at a constant rate, you still feel the accelerated motion pinning you to the outer edge.

Spacetime grips mass, telling mass how to move… mass grips spacetime, telling spacetime how to curve

GRAVITY IS THE CURVATURE OF SPACETIME

We see that accelerated motion can warp space and time. It is here that Einstein connected the dots to suggest that gravity is the warping of space and time. Gravity is the curvature of the universe, caused by massive bodies, which determines the path that objects travel. That curvature is dynamical, moving as those objects move.

What are the consequences of time dilation: –

Distances shrink in the direction of motion, although this only really becomes apparent at high percentages of the speed of light. For example, let’s say we set off for a star 100 light years from Earth and our speed is 99% of the speed of light. Common sense tells us that we will reach the star in just over 100 years, but this doesn’t take dilation into account. Instead, because the distance has been dilated we will reach the star in only 14.1 years. As we go ever faster the dilation becomes ever more dramatic, so that at 99.9% of the speed of light we would reach it in just 4.5 years and at 99.99% around 1.4 years.

Understanding Space-time

Again, slowing down of clocks due to high speeds is called time dilation. The equation for time dilation is:

But as I say early, please ignore the mathematical equation for now. We will be back later for more study.

If we try to move an object at 0% of the speed of light we will find that it has the mass we expect it to have. However, the mass of the object will appear to increase in ever-increasing proportion to our speed. For example, at 99.5% of the speed of light, the object will “weigh” around 10 times what it did when it was stationary.

Mass increases due to high speed.

Special theory of relativity says that:

a. Distance shrink in the direction of motion

b. Mass appears to increase with speed

c. Nothing can travel faster than light

Einstein said gravity is the curvature of space-time, rather than just the curvature of space.