Is Time Real? Proving Its Existence

[Zac Einstein]

Does time really Exist? Is there a single equation proves the existence of time?
What is time?

 

[rede96]

Does time really Exist? Is there a single equation proves the existence of time?
What is time?

I don't know the answer to that, but it seems a bit like asking is there a single equation that proves the existence of length, height of width.

Also, as equations are basically a way of explaining the real universe mathematically, it seems that asking that sort of question creates a bit of paradox. If we experience it, we know it is real.

Anyway, that is probably a bit too philosophical and not what you were after! :~)

 

[cowmoo32]

There's no definite answer, but there was a great episode of Through The Wormhole on this exact question on the science channel recently and it covered quite a few theories.

 

[Dale]

Does time really Exist?

What do you mean by "really Exist"? Do you have a definition or experimental procedure that allows us to distinguish between things that "really Exist" and things that don't?

 

[Dale]

There's no definite answer

I suspect there is not even a definite question. You need to have a definite question before you can even hope to have a definite answer.

 

[ardie]

for us to prove the existence of time we must first establish the definition of time. as you see described ratherwell by Einstein should you read his papers. However a logician would point out to you that should time not have existed, you wouldn't have been able to finish the sentence you just posted online, therefore there is a passage of some quantity that allowed your motion through space

 

[GrayGhost]

Does time really Exist? Is there a single equation proves the existence of time? What is time?

IMO, "change" proves the existence of time, far as how we define time goes. One such equation ... t=d/v. Time is the natural progression of events perceived by material entity. It's likely that our notion and definition of time is yet incomplete. Time will tell :)

GrayGhost

 

[Zac Einstein]

Time will tell

Yes, sir

What do you mean by "really Exist"? Do you have a definition or experimental procedure that allows us to distinguish between things that "really Exist" and things that don't?

Yes, sir

as you see described ratherwell by Einstein should you read his papers.

Where where where ? where can I read his papers, sir? huh?

 

[bcrowell]

Where where where ? where can I read his papers, sir? huh?

http://www.fourmilab.ch/

But I disagree with ardie's assertion that Einstein somehow defined time. DaleSpam's #4 is right on target, IMO.

 

[GrayGhost]

Where where where ? where can I read his papers, sir? huh?

http://www.fourmilab.ch/etexts/einstein/specrel/www/"

GrayGhost

 

[dan_r]

This is a very philosophical debate indeed - is time simply a means of quantification or is it some kind of ethereal absolute?

I read Jim al-Khalili's book about Quantum Physics some time back, and I'm sure it was in there that he brought up the concept of having an infinite multiverse.

I contemplated an extension of this, that being that if we, as conscious entities, were constantly jumping into a new universe at immeasurably fast rates, were we actually standing still in time while the multiverse moved around us? More like existing as a sequence of multiversal snapshots, kind of like when you make a flip book with a little stick man doing different things.. you flip the pages, and it makes him look as if he's moving.

 

[danR]

This is a very philosophical debate indeed - is time simply a means of quantification or is it some kind of ethereal absolute?

I read Jim al-Khalili's book about Quantum Physics some time back, and I'm sure it was in there that he brought up the concept of having an infinite multiverse.

I contemplated an extension of this, that being that if we, as conscious entities, were constantly jumping into a new universe at immeasurably fast rates, were we actually standing still in time while the multiverse moved around us? More like existing as a sequence of multiversal snapshots, kind of like when you make a flip book with a little stick man doing different things.. you flip the pages, and it makes him look as if he's moving.

You could think of this anyway if time is quantized at the Planck scale. But whether there actually exist pages in your flip-book other than the current one I doubt very much. To paraphrase Gertrude Stein:

'There was no then then.'

 

[Naty1]

Does time really Exist? Is there a single equation proves the existence of time?

We can't "prove" much of anything. I don't think we could even get a definition of time with which most would agree:

Wikipedia provides one view:

Two contrasting viewpoints on time divide many prominent philosophers. One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence. Sir Isaac Newton subscribed to this realist view... The opposing view is that time does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instead part of a fundamental intellectual structure... This second view... holds that time is neither an event nor a thing, and thus is not itself measurable nor can it be travelled.

http://en.wikipedia.org/wiki/Time

You can read a few comments there about an operational definition of time...a convenience so we can proceed to measure things...

But we do need to think about such things, else progress will never be made.

 

[danR]

According to Google, this post had a page 2, and I seem to recall it being longer. Whahappened?

 

[Dale]

The moderators determined that some of the content was in violation of the PF rules and so they removed it.

 

[danR]

The moderators determined that some of the content was in violation of the PF rules and so they removed it.

It must have been for one of my best lines; in other words, one of my worst lines.

 

[Goolds]

.I would define time in relation to the change in objects . If an object moves from point X to point Y, the difference in it's state between the two points could be described as a product of the time passed.
For example, a neutron moves from point X to point Y. At point X it has a value of 1 (no specific value). At point Y, it has a value of 10. This means that an increase of 9 has occured.
It is impossible to quantify time, so it is best described as an infinite variable. Meaning it's value depends entirely on the values that have changed.
Going back to the example, the time would be given as the distance divided by the magnitude of the change in the value.
Time need not, however rely on distance to be calculated. It could be any variable that changes. If a value does not change, then it's change is zero, which still is a value.
A millenium is as effective at quantifying time as a picosecond- they are both frames of referance by which a system can be examined, and the states at the start and end point compared.
Time could therefore be seen as not a property of nature, but an effective way for humans to referance the change in a system.
Sorry if i was really bad at explaining this, i will try to clarify in response to questions

 

[Phrak]

Let us for a moment define time. It is/was/will-be something that will extend from the present into the future, and did extend into the past. Any problems with this claim?

Obviously, not all of time exists at the present. Consider what "exist" means. Exist refers to the present. It has other tense to refer past and future. Any disagreement here?

Some of time was in the past and some will be in the future. Does anyone wish to claim that time is presently in the future or that time is presently in the past?

The "presently past" is something I would call an oxymoron. Anyone have a problem with that?

Words have shared meaning. Words are the majority conveyence of information on this forum. Bending them around to fit drawings on paper to razzle-dazzle readers should be left to Brian Greene, in my opinion.

If I claimed the future does not exist, would anyone have a problem with that?

If I claim the past does not exist, would anyone have a problem with this?

 

[DLuckyE]

If I claimed the future does not exist, would anyone have a problem with that?

If I claim the past does not exist, would anyone have a problem with this?

I think it's currently impossible to tell if this is true or not, it could be the future and past actually do exist but are just "invisible" to us since we live at the "now". But it could also be that "now" is all there is, how would you go about proving such a thing?

 

[ZapperZ]

I don't know why this topic keeps popping up like a zit.

What if a phenomenon is characterized by the property of something. Would that qualify for that something to "exist"? Case in point: an object is characterized by its dimension. Does that imply that "space" exist?

If that is so, then look at the numerous phenomena that are characterized via the broken time reversal symmetry (google it. You'd be surprised at what you would find as some of the more "common" things that are described by such symmetry breaking).

So now, ask yourself this. If these things are characterized by the symmetry of something, wouldn't it be rather silly for that "something" to not exist? After all, we depend on it, both qualitatively and quantitatively, as a characteristic in describing such phenomena. Is this a typical description for something that doesn't exist?

Zz.

 

[nitsuj]

I don't know why this topic keeps popping up like a zit.

What if a phenomenon is characterized by the property of something. Would that qualify for that something to "exist"? Case in point: an object is characterized by its dimension. Does that imply that "space" exist?

If that is so, then look at the numerous phenomena that are characterized via the broken time reversal symmetry (google it. You'd be surprised at what you would find as some of the more "common" things that are described by such symmetry breaking).

So now, ask yourself this. If these things are characterized by the symmetry of something, wouldn't it be rather silly for that "something" to not exist? After all, we depend on it, both qualitatively and quantitatively, as a characteristic in describing such phenomena. Is this a typical description for something that doesn't exist?

Zz.

That's a good angle ZapperZ. Perhaps the same as saying "Time exists no more or less then a rising sun or ticking clock.

 

[rhody]

Does time really Exist? Is there a single equation proves the existence of time?
What is time?

I don't know why this topic keeps popping up like a zit.

Zz.

Zz, Zac, (wow three z's in two names, that is unique)

I am not an expert here, and haven't read it yet, but just picked up: "https://www.amazon.com/dp/0195145925/?tag=pfamazon01-20" by Julian Barbour (have read summary reviews, but not the book). Would this (Zz) go a long way in addressing the OP's question ?

Rhody...

 

[Zac Einstein]

Ahm...ahm
Excuse me, I see everyone has his own opinion
How about this, I think time exists but in a relative way

 

[nitsuj]

Ahm...ahm
Excuse me, I see everyone has his own opinion
How about this, I think time exists but in a relative way

How about this these are perspectives on time, not opinions.

 

[Dale]

I am not an expert here, and haven't read it yet, but just picked up: "https://www.amazon.com/dp/0195145925/?tag=pfamazon01-20" by Julian Barbour (have read summary reviews, but not the book).

That remains one of the most disappointing books that I have ever had the misfortune of reading.

 

[rhody]

That remains one of the most disappointing books that I have ever had the misfortune of reading.

Care to elaborate ? Lee Smolin thought it was pretty good.

Rhody...

 

[Dale]

Care to elaborate ? Lee Smolin thought it was pretty good.

I was expecting a book that would explain how all of the physics formulas could be re-written to eliminate time. Instead the book devolved into a very lengthy monologue on Mach's principle. Since the universe appears to be non-Machian that was disappointing to me. The book really missed the mark of presenting physics without time.

 

[Zac Einstein]

How about this these are perspectives on time, not opinions.

Actually perspectives and opinions are the same thing, aren't they?

 

[bobc2]

Does time really Exist? Is there a single equation proves the existence of time?
What is time?

In a conversation with the philosopher Rudolph Carnap, Einstein remarked that the problem of Now worried him seriously. He explained that the experience of the Now means something special for man, something essentially different from the past and the future, but that this important difference does not and cannot occur within physics.

 

[atomthick]

Time can be thought of as beeing a measure of periodic processes. If we didn't have periodic processes in nature we probably didn't care or wouldn't be able to measure time.

The first time measurements were using the periodicity of the sun trajectory on the sky, later using timeglasses etc.

A nice thought experiment would be if someone can detach the notion of periodicity from the above definition of time and still get something meaningful.

 

[ZirkMan]

Time can be thought of as beeing a measure of periodic processes. If we didn't have periodic processes in nature we probably didn't care or wouldn't be able to measure time.

The first time measurements were using the periodicity of the sun trajectory on the sky, later using timeglasses etc.

A nice thought experiment would be if someone can detach the notion of periodicity from the above definition of time and still get something meaningful.

Think of an exposed cliff with all its geological layers on top of each other. No periodic process necessary to explain it, just one way direction of gravity demonstrating the existence of time.

 

[bobc2]

Does time really Exist?

It seems like you would not want to characterize time as something that exists. Space and objects exist. It seems that time is required for the existence of things. And it seems that time would be required for consciousness.

I don't recall an adequate accounting for time in any literature.

 

[bobc2]

I was expecting a book that would explain how all of the physics formulas could be re-written to eliminate time. Instead the book devolved into a very lengthy monologue on Mach's principle. Since the universe appears to be non-Machian that was disappointing to me. The book really missed the mark of presenting physics without time.

Like DaleSpam I found Julian Barbour's "The End of Time" to be a letdown. Maybe because it promised far too much. He made a reasonable case that the psychological impression of time as specifically linked to the sequence of 3-D events observed by a conscious being could be an illusion. That idea comes out of the block universe concept and is of course not at all an original Barbour idea.

Even accepting the block universe concept, he falls far short of making the case that there is no time. The block universe still needs time to exist. And the consciousness that observes the Special Relativity evidence of a block universe needs time.

He deals with consciousness trivially and never makes it clear how you have conciousness without time.

One of his major concepts, referred to as "Platonia", draws on the extension of the familiar configuration space of physics to four dimensions. Not a bad idea to think about, but again, I don't see how that fundamentally eliminates time. Richard Feynman's work with 4-D QM of course preceded this idea.

Barbour and Lee Smolin are evidently good friends and are quite complimentary of each other's idea.

 

[mathal]

Like DaleSpam I found Julian Barbour's "The End of Time" to be a letdown. Maybe because it promised far too much. He made a reasonable case that the psychological impression of time as specifically linked to the sequence of 3-D events observed by a conscious being could be an illusion. That idea comes out of the block universe concept and is of course not at all an original Barbour idea.

Even accepting the block universe concept, he falls far short of making the case that there is no time. The block universe still needs time to exist. And the consciousness that observes the Special Relativity evidence of a block universe needs time.

He deals with consciousness trivially and never makes it clear how you have conciousness without time.

It is necessarily true that we 'experience' 'time'. Whether the block universe model is 'true' or not is purely a philosophical point since there will never be a way to measure its existence. The closest that I have come across are the delayed choice experiments proposed by John Wheeler and succesfully performed by others. In these experiments photons are emited into an experimental set up and then in 'flight' the apparatus is altered in a random way which
produces results identical to what are produced if the apparatus was originally in the new configuration. John Wheeler's interpretation is that the experimenter altered the history of the photons by his actions. Clearly no one likes the idea that every action we perform is just part of some proscribed diorama.

The block universe, if that is what 'this' is, does not 'need' consciousness.

mathal

 

[atomthick]

We have the notion of time because we can mentaly order events by their appearance.

Probably the only thing that creates the notion of time is causality, therefore a theory that doesn't involve time might be also non-causal. Anyway, if time didn't existed wouldn't all just happen at once?

 

[bobc2]

We have the notion of time because we can mentaly order events by their appearance.

Probably the only thing that creates the notion of time is causality, therefore a theory that doesn't involve time might be also non-causal. Anyway, if time didn't existed wouldn't all just happen at once?

With the block universe it does all happen at once. That's why Barbour sees no need for time.

 

[mathal]

We have the notion of time because we can mentaly order events by their appearance.

Probably the only thing that creates the notion of time is causality, therefore a theory that doesn't involve time might be also non-causal. Anyway, if time didn't existed wouldn't all just happen at once?

The concept of a block universe puts time into a purely dimensional form. From the 'beginning' of 'time' on the universe is one object. We are part of the object. We go through our space time path seeing ourselves as the mover and shaker of our life but equally we are just the moved and shaken. No matter what you do, it is what you are doing and equally what you were always going to do. (If this is a block universe)
The delayed choice experiments of John Wheeler demonstrate that causality is not as neat and tidy as we always thought it was. Actions in the 'future' can 'alter' actions in the 'past' (WRT photons in the experiments). From a block universe perspective (an overview if you like) the potential paths of photons involves each entire path including where everything 'will' be 'when' the photon gets there (if it follows this particular path). It is where things 'will' be that governs the photon's probabilistic weight for each path.
mathal

 

[atomthick]

With the block universe it does all happen at once. That's why Barbour sees no need for time.

I understand but unfortunately this is not important to us, it would be important to a 4 dimensional being. We are 3 dimensional beings an therefore all is not just happening at once otherwise I would have responded at the same time you have posted your answer :)

 

[Naty1]

Was it Richard Feynman who said

"Time is what keeps everything from happening at once"..

??

 

[nitsuj]

The concept of a block universe puts time into a purely dimensional form. From the 'beginning' of 'time' on the universe is one object. We are part of the object. We go through our space time path seeing ourselves as the mover and shaker of our life but equally we are just the moved and shaken. No matter what you do, it is what you are doing and equally what you were always going to do. (If this is a block universe)
The delayed choice experiments of John Wheeler demonstrate that causality is not as neat and tidy as we always thought it was. Actions in the 'future' can 'alter' actions in the 'past' (WRT photons in the experiments). From a block universe perspective (an overview if you like) the potential paths of photons involves each entire path including where everything 'will' be 'when' the photon gets there (if it follows this particular path). It is where things 'will' be that governs the photon's probabilistic weight for each path.
mathal

Good comment,
however I disagree that a block universe and freewill of biology are mutualy exclusive. I like the perspective that knits time into distance.

electro-magnetic energy hardly seems to share the constraints of matter.

 

[bobc2]

I understand but unfortunately this is not important to us, it would be important to a 4 dimensional being. We are 3 dimensional beings an therefore all is not just happening at once otherwise I would have responded at the same time you have posted your answer :)

It is not clear that we are strictly 3D beings. In the block universe model our structure is 4D. The 3D experience could be related to some aspect of consciousness that includes an apparent advancing along the world line at light speed. You can compute the expected length of the world line by multiplying the life expectancy by the speed of light.

Many physicists are interested in developing an objective world view--not constrained by subjective aspects of experience.

 

[mathal]

Good comment,
however I disagree that a block universe and freewill of biology are mutualy exclusive. I like the perspective that knits time into distance.

electro-magnetic energy hardly seems to share the constraints of matter.

My opinion is that we have free will, in that we can never have the block universe overview of how things will turn out.
As with all information of a quantum nature we can never get a 3-d full color picture of what is happening. We can only elicit one bit of information from each photon and then put this together with other bits from other photons that are proscribed to the particular scenario of an experiment to get a range of results that tell us something about this very restricted set of circumstances.
IOW, as I said in my first post, the block universe may be an accurate picture of the universe but it is a picture we can never fully see.

"Keep on keepin' on" -Richard Farina I think. a good song


mathal

 

[bobc2]

My opinion is that we have free will, in that we can never have the block universe overview of how things will turn out.

You seem to be implying that free will just depends on whether you know the future rather than whether the future is already fixed.

As with all information of a quantum nature we can never get a 3-d full color picture of what is happening. We can only elicit one bit of information from each photon and then put this together with other bits from other photons that are proscribed to the particular scenario of an experiment to get a range of results that tell us something about this very restricted set of circumstances.

Most of our observations involve millions or billions of photons and other particles interacting in a more global fashion presenting classical phenomena leading to models that predict results in most everyday situations. Heisenberg's uncertainty principle, Schroedinger's probability waves, E = hf, and other quantum physics concepts refine the models for the microscopic domain. All of these models seem to be consistent with a block universe model, although most block universe literature do not specifically address QM or Quantum Field Theory issues.

IOW, as I said in my first post, the block universe may be an accurate picture of the universe but it is a picture we can never fully see.

In the block universe model we observe a continuous sequence of 3-D cross-sections of the 4-D universe. Observers having different velocities relative to each other experience different 3-D cross-section views of the same 4-D universe. If a long rope was snaked along a path extending 20 miles, you could walk along it for 20 miles and then feel like you have observed the rope sufficiently to provide an accurate description to anyone interested. Perhaps you could do something similar for a bundle of filaments that extend along a world line for 10^13 miles or so (you have the advantage of moving along the bundle--headed in the 4th dimension--at the speed of light).

The special relativity result in which different observers experience a time sequence of different cross-sections of the 4-D universe of course motivates the block universe model. No one seems to have presented an alternative that provides a logical explanation for this special relativity result.

You can introduce multiple universes (or parallel universes, etc.), but that seems to make the model quite a bit more complicated, introducing a host of mind boggling issues, and it is not obvious that you've really ridden yourself of block universe. And such models are often very contrived.

By the way, I personally don't like the block universe model for subjective reasons, but see the implications of multiple 3-D cross-sections as one of the great mysteries of physics (on a par with the double slit experiment).

 

[GrayGhost]

Like DaleSpam I found Julian Barbour's "The End of Time" to be a letdown ...

One of his major concepts, referred to as "Platonia", draws on the extension of the familiar configuration space of physics to four dimensions. Not a bad idea to think about, but again, I don't see how that fundamentally eliminates time. Richard Feynman's work with 4-D QM of course preceded this idea.

I would be very surprised of J Barbour was attempting to eliminate time w/o replacing it with something more fundamental, something which would have no impact on our perception of time but rather only its meaning.

J Barbour must replace time with the transitioning thru his landscape of Platonia. So I agree with you, that our notion of time must remain no matter how he attempts to define its mechanism. He may eliminate time as we define it, but it must be replaced with something that serves the same purpose. My assumption is that he believes a redefinition of TIME is required to unify the all of physics. I've read up on Julian before, but I haven't read his book. Sounds like you would not recommend it. He's a rather reputable physicist from what I've heard, yes?

GrayGhost

 

[Phrak]

A lot of people here are having problems with a derivate of the word "is". Bill Clinton went to great lengths to explain what is is. So why is it that is, is so difficult? ...Or, ahem, why exists it that exists, exists so difficult? Ahem.

 

[bobc2]

I would be very surprised of J Barbour was attempting to eliminate time w/o replacing it with something more fundamental, something which would have no impact on our perception of time but rather only its meaning.

J Barbour must replace time with the transitioning thru his landscape of Platonia. So I agree with you, that our notion of time must remain no matter how he attempts to define its mechanism. He may eliminate time as we define it, but it must be replaced with something that serves the same purpose. My assumption is that he believes a redefinition of TIME is required to unify the all of physics. I've read up on Julian before, but I haven't read his book. Sounds like you would not recommend it. He's a rather reputable physicist from what I've heard, yes?

GrayGhost

You make a really good point, GrayGhost. I think you may have it right on the money here. Excellent analysis -- particularly for a guy who hasn't had the chance to read the book. I first started reading it a little at a time sitting in a chair at Border's before buying the book.

Julian Barbour is of course a first rate physicist (as his buddy Lee Smolin). I certainly have a lot of respect for him. Although I was let down, much of the book was very interesting and I would recommend it. I guess I had so much expectation, thinking that finally we have a book that will clarify all essential aspects of time--and I agree with DaleSpam that it falls short of those expectations.

But, I'd love to sit down and talk about time with him and Paul Davies for a few hours.

 

[Dale]

He may eliminate time as we define it, but it must be replaced with something that serves the same purpose.

This is correct also for his technical papers which I have read. It is a "rose by any other name" approach, IMO. He makes great efforts to verbally emphasize the difference of his concept, but then he sticks it in the same places in all of the equations which eliminates the differences mathematically.

 

[mathal]

You seem to be implying that free will just depends on whether you know the future rather than whether the future is already fixed.



Most of our observations involve millions or billions of photons and other particles interacting in a more global fashion presenting classical phenomena leading to models that predict results in most everyday situations. Heisenberg's uncertainty principle, Schroedinger's probability waves, E = hf, and other quantum physics concepts refine the models for the microscopic domain. All of these models seem to be consistent with a block universe model, although most block universe literature do not specifically address QM or Quantum Field Theory issues.



In the block universe model we observe a continuous sequence of 3-D cross-sections of the 4-D universe. Observers having different velocities relative to each other experience different 3-D cross-section views of the same 4-D universe. If a long rope was snaked along a path extending 20 miles, you could walk along it for 20 miles and then feel like you have observed the rope sufficiently to provide an accurate description to anyone interested. Perhaps you could do something similar for a bundle of filaments that extend along a world line for 10^13 miles or so (you have the advantage of moving along the bundle--headed in the 4th dimension--at the speed of light).

The special relativity result in which different observers experience a time sequence of different cross-sections of the 4-D universe of course motivates the block universe model. No one seems to have presented an alternative that provides a logical explanation for this special relativity result.

You can introduce multiple universes (or parallel universes, etc.), but that seems to make the model quite a bit more complicated, introducing a host of mind boggling issues, and it is not obvious that you've really ridden yourself of block universe. And such models are often very contrived.

By the way, I personally don't like the block universe model for subjective reasons, but see the implications of multiple 3-D cross-sections as one of the great mysteries of physics (on a par with the double slit experiment).

I interpret 'know the future' and 'future is already fixed' as the same concept. If you 'know' the future that future would necessarily be fixed unless you feel that 'knowing' the future allows you to change it to a different 'future'.

Adding to what nitsuj said in his previous post it seems unlikely a delayed choice experiment involving electrons (or any other massive particle) could be performed measurably altering the future paths of the electrons as was done with photons in the original experiments.

mathal

 

[bobc2]

This is correct also for his technical papers which I have read. It is a "rose by any other name" approach, IMO.

Good way to put it.

He makes great efforts to verbally emphasize the difference of his concept, but then he sticks it in the same places in all of the equations which eliminates the differences mathematically.

DaleSpam, I haven't seen his technical papers. Do you have any references? Thanks.

 

[bobc2]

I interpret 'know the future' and 'future is already fixed' as the same concept. If you 'know' the future that future would necessarily be fixed unless you feel that 'knowing' the future allows you to change it to a different 'future'.

What if no one is there to know the future (say, for the first 3 to 4 billion years after the big bang)? The block universe model would of course have it all fixed without anyone to know it. God knew it, so maybe that satisfies your concept (sorry, I always try to leave theology out of my posts).

Adding to what nitsuj said in his previous post it seems unlikely a delayed choice experiment involving electrons (or any other massive particle) could be performed measurably altering the future paths of the electrons as was done with photons in the original experiments.

mathal

My memory is not always trustworthy, but I think the experiment has been performed with massive particles.