What is Speed? What is Velocity? Are They All the Same Words?

The British use two different words for speed. One is "speed", which is our equivalent of speed, and the other is "velocity", which is what we should call speed. But we commonly call them both speed. 

Although they both mean "speed" as the distance traveled divided by the time elapsed, there is an important difference between them.

Velocity is vectorial. That is, it contains directional information as well as speed information. 

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If you ask how so, let me try to explain with an example:

When we travel on a road at a constant speed, we have a speed, but we also have a direction we are traveling in. If the road is a winding road that curves like a snake and our travel speed is constant, the speed value that the English call "speed" does not change along the way, but the speed value called "velocity" changes.

This is because the direction we are traveling changes according to the bends in the road.

In this case, even if we travel on an uneven road with a constant speed, it means that we have angular momentum because we change angles. 

Angular momentum means angular acceleration. 

Acceleration, as you know, is a multiplier of force. 

When we are traveling at constant speed, in a frictionless environment, we don't feel a force acting on us. On a train or an airplane, we can get up and walk down the aisle as if we were traveling in a straight line.

But if the train changes direction, our direction changes and we feel a sideways acceleration, that is, a force.

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This is the explanation for what is known in physics as the "twins paradox", in which one twin travels to a distant place and back in a rocket at a speed close to the speed of light, and the twin in the rocket stays younger than the twin left on earth.

This paradox states that from the perspective of the twin who stays on Earth, the twin in the rocket has speed, while from the perspective of the twin in the rocket, the twin who stays on Earth is traveling away from the rocket at the same relative speed, thus creating a paradox as to which twin will stay younger than the other.

Speed is ultimately a relative concept. According to whom, according to what do we say we have a speed? According to the beholder, the observer.

So for the one in the rocket, it appears to be moving away at the same speed as the one in the world, and for the world, it appears to be moving away at the same speed as the one in the rocket.

In reality, the twin in the rocket will stay younger, because even if he is traveling at constant speed with the rocket, he will have to turn back at some point to get back together, that is, he will have to change direction with the rocket.

This will have an angular acceleration effect on the twin in the rocket. The twin inside the rocket will feel this effect. 

Inertia There is also an effect on mass that we call inertia.

The earthbound twin does not feel any inertia effect. 

This is the main reason why the twin in the rocket stays younger than the twin on Earth. 

Because of its high speed, the twin in the rocket feels time more slowly. In fact, he doesn't feel anything like that, but time flows more slowly for him than it does on earth. Add acceleration, that is, force, and there is no paradox.

So the so-called paradox of twins is not a paradox at all. There is a difference in the physical conditions experienced by both twins.

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From this point of view, we need to know that in addition to our speed, the force, acceleration, also has an effect on time.

Einstein first developed the theory of special relativity, but since special relativity is only a theory of the relative velocities of objects, he spent many years trying to figure out how to include force in this theory.

The result is the general theory of relativity he came up with years later!

Special relativity is just a special case of general relativity, where the force effect is zero and the velocity is constant.

When acceleration is included in the formulas, you have to include matter, that is, mass. Because force is the product of mass and acceleration. F=m.a

Mass is also energy. E=m.c2

So general relativity is also an energy formula. 

Energy is a conserved value. In the universe we are in, energy does not disappear at all!

(Although this subject keeps puzzling me, is there really no way energy can disappear? Could energy be diminishing due to the entropy effect? But that's not our topic now, so I'll close the parenthesis).

Einstein's general relativity formula is a marvelous formula that explains how mass relates to energy, energy to force, force to acceleration, force to acceleration, and acceleration to velocity and changes of direction in our velocity, and that within this web of relationships, time has a twisted structure, not a linear one, and therefore we live this life by twisting the dimensions of space-time.

A bit complicated, but still marvelous!

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These days, scientists are thinking a lot about the possible errors in this formula and whether it can be interpreted differently.

I have written about these issues before, those who are interested will remember.

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There are some phenomena in the universe that cannot be explained by Einstein's general relativity. Anomalies!

Just as Newton's gravitational formulas once could not explain the deviation of Mercury's orbit, today, famous theoretical physicists are trying very hard to find out whether Einstein's general relativity formulas may be inadequate in some way.

Yet it seems that general relativity has succeeded in all the experiments. In practice, it has already entered our lives. 

I guess you are familiar with the famous topic of GPS satellites sending information to us by taking into account the general relativity effect caused by their orbital velocity, so that our navigators in our vehicles work properly with the right timing.

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But let's not forget that Newton's formulas at the time also showed that there was a solution to Mercury's orbital deviation if the hypothetical planet Vulcan could be found.

For years, the planet Vulcan was searched for in the sky. But it was not found. Because there was no such planet!

Similarly today, if "dark matter" exists, Einstein's general relativity formulas can be used to explain the anomalies in the rotation speeds of stars in distant galaxies around the galactic center.

Dark matter, on the other hand, like the once hypothetical planet Vulcan, has yet to be found scientifically despite all the investigations and research.

Maybe there really is no such thing as dark matter! Maybe there really is a problem with Einstein's formulas!

Isn't it possible?

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Yes, there are physicists who think that Einstein's formulas are incomplete.

Some physicists are looking for new perspectives.

One of these new perspectives is the MOND theory, Modified Newtonian Dynamics. I won't go into details, you can find detailed information on the internet by typing MOND.

This theory is an improved version of Newtonian gravitational theory, a theory that seeks a solution to galaxy anomalies in space. 

It is a theory that tries to find a solution to the orbital motion of stars in distant galaxies, without including hypothetical matter such as dark matter, which has not yet been found despite all the searches.

There has been a lot of research on this theory. Einstein's formulas on the one hand and the MOND theory on the other, both theories have been analyzed on thousands of done experiments on stellar motions obtained with telescopes, and the results have shown that Einstein has developed a more consistent formula.

So the MOND proponents seem to have been frustrated for now.

Although investigations are still ongoing, it is likely that the MOND theory will go down in history as an erroneous theory.

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Another attempt is to revise Einstein's formulas. 

This is called quantum gravity, or quantized gravity. 

So far, though, there is not enough progress in this area either. 

Gravitational effects are not based on particles like other forces in nature. 

What we call gravity is an effect that involves a continuum, a bending in dimensions, a bending in time!

According to Einstein's formulas, gravity is not even a force. 

It's space-time bending! The shortest path in the motion of mass, but a twisted path!

But if it can be formulated in terms of particles like other forces, then we will have a "formula for everything" that will include other formulas in nature.

Einstein himself tried very hard on this subject, but unfortunately he didn't have enough time.

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The development of such a formula also means that the subatomic quantum world and the movements of matter in the galaxies we observe in the universe can be explained by a single formula.

This is what some theoretical physicists have been working on.

The late Hawking spent most of his life on this subject. But he could not reach a conclusion either.

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Of course, I'm talking about theoretical physicists, but there are also a lot of people working in experimental physics who are studying all these theories and doing experiments.

I don't know, one day will it be possible to prove the existence of dark matter?

At Cern, they are accelerating and accelerating and splitting atoms, maybe one day they will find real dark matter.

If they can prove the existence of dark matter, it will be said that Einstein was really right. 

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Or a scientist like Einstein could come along and come up with a completely different formula from a completely new perspective. Thus, a solution to the anomalies observed in the universe can be found without hypothetical dark matter.

For all these studies to reach a conclusion, we need scientists who will think about these issues. Someone at least as smart as Einstein, as smart as Newton!

Theoretical physicists are very few even in the world, but I wish there was someone among us who could find solutions to these problems!

We have so many universities and many of them have physics engineering departments.

Will there be someone from our ranks one day?

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Although I can't help but wonder how that will work when we don't even have a second word for speed in our language.

Can anyone suggest a word for speed that also includes directional information?

What should we say to distinguish between the two?

Do you think it would be okay to say "directional speed"? Should we say vector speed?

I can hear some people saying "speed". Let speed be without directional information, but speed should include directional information!

Yes, yes, one is Persian and the other is Arabic!

Is there no Turkish for this?

Stay with science! But first, let's find a cure for our language.

Love and respect to everyone from Moscow