"Time is an illusion" according to Einstein

[Blub]

TL;DR Summary

One of the most widespread misunderstandings of physics: Is time an "illusion"?

I keep reading things like the following (for me not correct) on different websites like researchgate (coming from supposedly phd.), so I wanted to make sure there is no flaw in my thinking.
One example of a comment I've read was:
"TIME is an ILLUSION according to EINSTEIN - (the space-time continuum)!
Albert Einstein was very clear in his day. Physicists are very clear now. Time is not absolute, despite what common sense tells you and me. Time is relative, and flexible and, according to Einstein, "the dividing line between past, present, and future is an illusion". So reality is ultimately TIMELESS. This sounds pretty bizarre from the view of classical physics, but from the view of consciousness theory and spirituality, it fits in perfectly."Now the last sentence alone hints at a non-physicist, but what bothers me are the quotes from Einstein. Did Einstein really say "time is an illusion" and that "reality is timeless".
According to special relativity for an event b happening outside a light cone of an event a, there is a reference frame in which event a and b happen at the same time, BUT in the light cone of event a there is still past, present and future (which are NOT happening at the same time) and the events in the light cone are causally connected. Did I understand something wrong or are so many people sure of the idea that time is an illusion?

 

[Dale]

Summary:: One of the most widespread misunderstandings of physics: Is time an "illusion"?

Now the last sentence alone hints at a non-physicist, but what bothers me are the quotes from Einstein. Did Einstein really say "time is an illusion" and that "reality is timeless".

Einstein did say "the distinction between past, present, and future is only a stubbornly persistent illusion." However, it is exceptionally important to recognize that he did not say that in any of his professional scientific writings. This was written to the widow of his friend Michele Besso shortly after Besso's death. It was intended to be words of comfort to the grieving widow of a dear friend, not a scientific pronouncement.

 

[PeroK]

Summary:: One of the most widespread misunderstandings of physics: Is time an "illusion"?

I keep reading things like the following (for me not correct) on different websites like researchgate (coming from supposedly phd.), so I wanted to make sure there is no flaw in my thinking.
One example of a comment I've read was:
"TIME is an ILLUSION according to EINSTEIN - (the space-time continuum)!
Albert Einstein was very clear in his day. Physicists are very clear now. Time is not absolute, despite what common sense tells you and me. Time is relative, and flexible and, according to Einstein, "the dividing line between past, present, and future is an illusion". So reality is ultimately TIMELESS. This sounds pretty bizarre from the view of classical physics, but from the view of consciousness theory and spirituality, it fits in perfectly."Now the last sentence alone hints at a non-physicist, but what bothers me are the quotes from Einstein. Did Einstein really say "time is an illusion" and that "reality is timeless".
According to special relativity for an event b happening outside a light cone of an event a, there is a reference frame in which event a and b happen at the same time, BUT in the light cone of event a there is still past, present and future (which are NOT happening at the same time) and the events in the light cone are causally connected. Did I understand something wrong or are so many people sure of the idea that time is an illusion?

Most of this is not physics anyway. A statement like "time is an illusion" has no definite meaning. You cannot set up a experiment to test whether "time is an illusion".

What you can do is use the relativistic model of spacetime to make predictions and/or explain the behaviour of the universe. In that sense you need spacetime as a four dimensional continuum. That's the physics. The rest is noise.

 

[Dale]

What you can do is use the relativistic model of spacetime to make predictions and/or explain the behaviour of the universe. In that sense you need spacetime as a four dimensional continuum. That's the physics. The rest is noise.

Yes, and in that context:

According to special relativity for an event b happening outside a light cone of an event a, there is a reference frame in which event a and b happen at the same time, BUT in the light cone of event a there is still past, present and future (which are NOT happening at the same time) and the events in the light cone are causally connected.

This is correct. In a frame-invariant sense all events in or on the future light cone of A are in the future of A, and all events in or on the past light cone of A are in the past of A. That is frame invariant.

In Newtonian spacetime there is an unambiguous split between the past of A, the present of A, and the future of A. In relativistic physics the splitting is different but you can still unambiguously split into a causal future of A, a causal past of A, and a third region that is neither past nor future. I am not sure that the term "present" is a good plain-language description of that third region, but I am not sure what other plain-language word should be used instead. Regardless, the science and math describes it completely clearly, so this is a problem of language rather than a problem of science.

 

[Blub]

Thank you for your answers. Non-scientific interpretations of physical phenomena are so widespread and often non-consistent with the things I learned, that I keep getting unsure about my understanding, especially about their supposed consequences for the every-day world.

 

[phinds]

Thank you for your answers. Non-scientific interpretations of physical phenomena are so widespread and often non-consistent with the things I learned, that I keep getting unsure about my understanding, especially about their supposed consequences for the every-day world.

Even many supposedly scientific presentations (pop-sci presentations, that is) are often wildly inaccurate or at the very least highly misleading. Never think that watching the Science Channel presentations on cosmology, for example, are educational. They are entertainment. Same for pop-sci books.

 

[Dale]

Thank you for your answers. Non-scientific interpretations of physical phenomena are so widespread and often non-consistent with the things I learned, that I keep getting unsure about my understanding, especially about their supposed consequences for the every-day world.

I completely understand. That is one reason that the standard that we use on Physics Forums is that everything we discuss here should be consistent with the professional scientific literature. Even Einstein's own writings outside of that professional setting, are simply not sufficiently rigorous to serve as the basis of a scientific discussion. He was writing a letter of comfort to a non-physicist friend, and we cannot expect an expression of comfort to a lay person to also serve as a statement of scientific fact to the physics community.

 

[PeterDonis]

One example of a comment I've read

Where? Please give a reference.

 

[Ebeb]

Einstein did say "the distinction between past, present, and future is only a stubbornly persistent illusion." However, it is exceptionally important to recognize that he did not say that in any of his professional scientific writings. This was written to the widow of his friend Michele Besso shortly after Besso's death. It was intended to be words of comfort to the grieving widow of a dear friend, not a scientific pronouncement.

He wrote:
<<...for us convinced physicists the distinction between past, present, and future is only an illusion, although a persistent one." >> ( Letter to Michele Besso family, March 21, 1955. Einstein Archives 7-245).

 

[Ebeb]

Two more interesting Einstein quotes to have a look into Einstein's mind:

<< From a "happening" in three-dimensional space, physics becomes, as it were, an "existence" in the four-dimensional "world". >> (Albert Einstein. "Relativity: The Special and the General Theory." 1916. Appendix II Minkowski's Four-Dimensional Space ("World") (supplementary to section 17 - last section of part 1 - Minkowski's Four-Dimensional Space).

<< Since there exists in this four-dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four-dimensional existence, instead of, as hitherto, the evolution of a three-dimensional existence. >> (Albert Einstein, "Relativity", 1952).

Also interesting:
Karl Popper about his encounter with Einstein:
<< The main topic of our conversation was indeterminism. I tried to persuade him to give up his determinism, which amounted to the view that the world was a four-dimensional Parmenidean block universe in which change was a human illusion, or very nearly so. (He agreed that this had been his view, and while discussing it I called him "Parmenides".)... >> (Karl Popper, Unended Quest: An Intellectual Autobiography.Routledge Classics. Routledge. pp.148–150).

 

[Dale]

He wrote:
<<...for us convinced physicists the distinction between past, present, and future is only an illusion, although a persistent one." >> ( Letter to Michele Besso family, March 21, 1955. Einstein Archives 7-245).

That doesn’t matter. The context was still outside of the professional scientific literature and hence is unsuitable for scientific discussion and here on PF.

 

[bhobba]

I have just finished reading the book - The Philosopher and the Physicist which is a very interesting book about the history of relativity and a historically important debate between Einstein and the philosopher Bergson. Nowadays much of what they debated is a non issue because relativity is looked at a bit differently - more along the lines of how Einstein's teacher, Minkowski, viewed it, as simply the geometry of space-time in inertial frames. The debate centred around simultaneity, what time actually is, and what physicists think of time. During the 19th century it was discovered there is a strong connection between symmetries and geometry - the so called Erlangen program:
https://en.wikipedia.org/wiki/Erlangen_program

Now by definition inertial frames are frames where the laws of physics, whatever they are, are the same wherever you are, whatever direction you are, and whatever time it is. We have strong experimental evidence such frames to a very high degree of accuracy exist. Note - there is nothing in that saying anything about what time is - just there is something called time. The Principle of Relativity (POR) says the laws of physics are the same in any inertial frame or frame moving at constant velocity wrt to an inertial frame - but the concept of velocity depends first on pinning down the concept of time. I will take that up a bit later, but let's complete SR first:
http://www2.physics.umd.edu/~yakovenk/teaching/Lorentz.pdf

Basically this shows how the symmetries of the POR implies the geometry of space-time. Exactly as the Erlangen program would assert.

Now getting back to time. It does not matter what you think time is, an illusion, really psychological, philosophical, or anything you can think of. We know from the definition of an inertial frame it doesn't matter when you perform something that takes some time, it will take exactly the same amount of time. So to assign a number to time, which is all that is required in the derivation I linked to, you simply repeat the same process over and over counting the number of times it occurs.

This is why questions like time is an illusion, the debate on what time is that Einstein and Bergson engaged in, and such discussions, really have nothing to do with relativity. It is a non-issue. That is not to say there are not questions remaining on the nature of time - physics simply says - it's irrelevant because you can assign a number to it regardless - and that is all physics requires.

Thanks
Bill