This book is about understanding, what we know and how we know.

The first steps of understanding is to make observations. Observations are a description of the reality and are the cornerstone of understanding. The second step is to make links between those observations.

When I was at high school I asked myself the following question: Suppose you are in a rocket travelling which the speed of light. From the opposite side a second rocket is approaching you, also travelling with the speed of light. When the two rockets meet, what will happen, what will we see, what will I see, how do we describe that?

              rocket 1                                   rocket 2
              ---------->              X              <----------
                                 meeting point

I expect (and I hope) that for many people reading this book, that this problem seems far fetched and special. Maybe they never have heart that light has a speed or don't understand what means the speed of light.

On the other hand I hope that all readers of this book, after reading and doing the demonstrations, that they will get a better idea what means: speed, the speed of light and speed of gravity propagation. How gravity influences us and how we describe the reality.

When you try to understand what happens when you travel with the speed of light, one of the first questions to ask yourself is: Is it (physical) possible to travel with the speed of light. Because how will you ever agree with someone who will claim that he or she knows the answer, when there is no way to observe if his or her answer is correct.

The answer on this question is no. You cannot build any device, do any experiment, which allows human beings to travel with the speed of light i.e. this problem is not realistic.

That does not mean that you cannot study what happens when you or something moves at high speed. For example with the speed of sound. To explain this thought experiments are used throughout this book.

For example: Thought experiment 3 is called:

"A duel in the mist".
In this experiment the propagation of sound is studied.


Let us study a slightly different problem, closely related to the first: In stead of two rockets consider two trains.
One train starts from point A and the other from point B The two trains move towards each other on the same track with a speed v.

Five questions:
  1. What will happen when the two trains meet ?
  2. Where on the track will the two trains meet (collide) ?
  3. When will the two trains meet.
  4. What will be the (average) speed v of each train.
  5. What will be the relative speed of each train.

This is a realistic problem. You can place two trains on the same track, see how they move towards each other and observe where and when they meet.

The answer on question 1 is:
When the two train meets there will be a collision. The exact results of this collision depend about the speed of each the two trains i.e. the relative speed. (See question 5)

The answer on question 2 requires three observations:
  1. The position of point A,
  2. The position of point B and
  3. The position of point X some where between A and B.
When the two trains have the same (average) speed and both trains started at the same moment than this point X will be in the middle between A and B.

The answer on question 3 requires three observations with your watch:
  1. The time t0A when the train leaves point A,
  2. The time t0B when the train leaves point B and
  3. The time t1 when the two trains collide at point X.

The answer on question 4 and 5 involve mathematics. In chapter 1 of this book those calculations are discussed in more detail. The actual form of each of those calculations is not so important. What is important that this calculation is done based on the answers (results or observations) of the questions 2 and 3.


In order to prevent an accident you can ask your self the question: what is the quickest way to detect that a rocket or train is approaching. With my eyes, with a laser beam or are there other means? This question addresses the issue what is the fastest way to communicate.

You can also yourself two more difficult questions:
  1. Does your watch when you travel by train behave the same as the watch of someone who stayed in A or (what is the same) in B.
  2. What will be the speed of the combined wreckage after the collission.

The reason of all those questions will become clear in the next chapters of this book.

As mentioned before you can only study something that is physical possible and realistic. The question ofcourse is what is exactly physical possible and what is not. Where do you draw the line.

A question that is physical possible but cannot be simply answered is the following:
Suppose I position myself now at a point in outer space 20 billion light-years away. How does the universe look from that point? Does it look similar or different compared from our position NOW?

The reason of the question will become clear if you know that from our position in the Universe all the galaxies (seem) to move away and you can see galaxies 20 billion light-years away.
The question is: if you place yourself now at a position 20 billion light- years away, will you more or less from that point see the same as from our Earth i.e. that all the galaxies also move away?

You can also repeat that process and position yourself NOW 40 billion light-years away and ask again (and again) the same question.

You can also ask yourself the question: when I do any experiment over there now and at our position here now, is the outcome any different i.e. are the physical laws (which are a description of the reality) the same.

The subject of this book is the reality; our reality. You can ask yourself the question are we, humans, capable of describing the reality. To challenge the concept of our reality there is thought experiment 6: "The world of a fish" In thought experiment 6 we place ourselves in a different environment and perform observations.


A description of the reality has to be clear and unambiguous. In a book review (See Literature 52) the following is written:

He concludes that "in all likelihood, OUR universe contains all that we will ever know; the UNIVERSE of other realms of existence that lies beyond is inaccessible, probably forever. If this is true, then it is not outrageous to believe that we can know 'all there is to know'"

The problem with those sentences (and only with those two) is that if you want to answer the question: Is the first sentence true, than you must fully understand that sentence. That means it must be clear what means 1) OUR universe and 2) the UNIVERSE of other realms i.e. that there is more than one universe. If that is not clear than you can not agree with the conclusion of the second sentence.

It is the "believe" of the author that there is only one Universe and that we humans will never understand or know everything, including our own behaviour.


This book is written for every one. The important concepts are explained using simple language. Almost no mathematics are involved. One of the topics of this book is that the reality can be described to a large extend with simple laws and mathematics.
For example: in order to describe speed three numbers are used: vx, vy and vz. Those three numbers specify the direction of movement of an object. Those three numbers are called: a vector. For acceleration the same concept is followed
Imaginary numbers are not necessary. Simplicity wins. Certain topics are described in more detail using mathematics.
For example: technical information about the demonstrations.
Those sections can be skipped by the general reader.

As such I hope that the reader gets a better feeling what science is.

One of the major topics of this book is the propagation speed of gravity. This question becomes important when we want to study the behaviour of the movement of the planet Mercury around the Sun. A simulation of this movement is described as part of the programs MERCURY and PLANETS.
The results of this simulation show that the speed of with which gravity propagates is not equal to the speed of light but roughly between 10 and 100 times as large. Only by making that assumption it is possible to bring the simulation in agreement with observations.

I hope that the readers of this book are going to send more accurate data in the form of observations, which will either refute or improve the accuracy of my calculation of the speed with which gravity propagates.

One of the most important question that you can ask while reading this book is: is all, what is written, true?

To the best of my knowledge, I think it is. On the other hand I have my doubts. The topic of this book is to describe the reality as accurate as possible. This raises certain questions. Is it possible by humans to describe (in words) the reality accurate? Are equations better or worse?

The basic ideas of this book where original described in three letters. Those letters I sent to many people. I received 4 replies.
In one answer received I was informed that my calculation of the centre of mass of the Sun was wrong. That error is corrected in this book. The other three answers received did not show any sign that what I was doing was wrong. They stimulated me to continue and that is one of the reasons of this book.


I would like to thank every one who responded, after recieving a copy of the book: The Reality, Now and Understanding.
One answer received was negative. Two answers received did not express any opinion.

I also would like to thank everyone who responded and still is corresponding with me by using e-mail and Internet. Those e-mails are very important to me to shape what it is my mind.

Schilde 2970
31 May 1995

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