Debunking the Existence and Duration of Virtual Particles

[tiny-tim]

hi byron178!

How come some say that virtual particles exist and some say they don't exist?

some people have a strange idea of the meaning of "exist"

here's a more psychological reason from Hrvoje Nikolic, at page 33 of "Quantum mechanics: Myths and facts" (51 pages, 2007, at http://arxiv.org/abs/quant-ph/0609163" ) …

9.3 Virtual particles?
The calculational tool represented by Feynman diagrams suggests an often abused picture according to which “real particles interact by exchanging virtual particles”. Many physicists, especially nonexperts, take this picture literally, as something that really and objectively happens in nature. In fact, I have never seen a popular text on particle physics in which this picture was not presented as something that really happens. Therefore, this picture of quantum interactions as processes in which virtual particles exchange is one of the most abused myths, not only in quantum physics, but in physics in general. Indeed, there is a consensus among experts for foundations of QFT that such a picture should not be taken literally. The fundamental principles of quantum theory do not even contain a notion of a “virtual” state. The notion of a “virtual particle” originates only from a specific mathematical method of calculation, called perturbative expansion. In fact, perturbative expansion represented by Feynman diagrams can be introduced even in classical physics [52, 53], but nobody attempts to verbalize these classical Feynman diagrams in terms of classical “virtual” processes.

So why such a verbalization is tolerated in quantum physics? The main reason is the fact that the standard interpretation of quantum theory does not offer a clear “canonical” ontological picture of the actual processes in nature, but only provides the probabilities for the final results of measurement outcomes.

In the absence of such a “canonical” picture, physicists take the liberty to introduce various auxiliary intuitive pictures that sometimes help them think about otherwise abstract quantum formalism. Such auxiliary pictures, by themselves, are not a sin. However, a potential problem occurs when one forgets why such a picture has been introduced in the first place and starts to think on it too literally.​

 

[danR]

hi byron178! some people have a strange idea of the meaning of "exist"

here's a more psychological reason from Hrvoje Nikolic, at page 33 of "Quantum mechanics: Myths and facts" (51 pages, 2007, at http://arxiv.org/abs/quant-ph/0609163" ) …

9.3 Virtual particles?
The calculational tool represented by Feynman diagrams suggests an often abused picture according to which “real particles interact by exchanging virtual particles”. Many physicists, especially nonexperts, take this picture literally, as something that really and objectively happens in nature. In fact, I have never seen a popular text on particle physics in which this picture was not presented as something that really happens. Therefore, this picture of quantum interactions as processes in which virtual particles exchange is one of the most abused myths, not only in quantum physics, but in physics in general. Indeed, there is a consensus among experts for foundations of QFT that such a picture should not be taken literally. The fundamental principles of quantum theory do not even contain a notion of a “virtual” state. The notion of a “virtual particle” originates only from a specific mathematical method of calculation, called perturbative expansion. In fact, perturbative expansion represented by Feynman diagrams can be introduced even in classical physics [52, 53], but nobody attempts to verbalize these classical Feynman diagrams in terms of classical “virtual” processes.

So why such a verbalization is tolerated in quantum physics? The main reason is the fact that the standard interpretation of quantum theory does not offer a clear “canonical” ontological picture of the actual processes in nature, but only provides the probabilities for the final results of measurement outcomes.

In the absence of such a “canonical” picture, physicists take the liberty to introduce various auxiliary intuitive pictures that sometimes help them think about otherwise abstract quantum formalism. Such auxiliary pictures, by themselves, are not a sin. However, a potential problem occurs when one forgets why such a picture has been introduced in the first place and starts to think on it too literally.​

The problem for laypersons reading is the comparisons of authors' CV, and where they are attacking or defending virtual particles in print.

Physics Forums is strongly associated with Scientific American, wherein a highly qualified expert says (2006) that virtual particles are flat-out real, and he doesn't mince words:

http://www.scientificamerican.com/article.cfm?id=are-virtual-particles-rea
['rea' sic. That's a valid URL]

The layperson has to compare that with Hrvoje Nikolic's credentials. The latter may indeed be right, but only in a debate before peers is any definitive answer going to emerge. If the only outcome among peers is that everyone agrees to disagree, or there are arguments that the other side doesn't understand each other, that they are arguing at cross-purposes, etc. then the layperson will tend to side with the guy with the C.V.

Edit: I have noted the comment by neum on the article at the bottom of the page in the link above. This is the sort of comment that commends itself as the beginning of a debate the VP-real defenders must answer to.

 

[Lapidus]

The problem for laypersons reading is the comparisons of authors' CV, and where they are attacking or defending virtual particles in print.

Physics Forums is strongly associated with Scientific American, wherein a highly qualified expert says (2006) that virtual particles are flat-out real, and he doesn't mince words:

http://www.scientificamerican.com/article.cfm?id=are-virtual-particles-rea
['rea' sic. That's a valid URL]

The layperson has to compare that with Hrvoje Nikolic's credentials. The latter may indeed be right, but only in a debate before peers is any definitive answer going to emerge. If the only outcome among peers is that everyone agrees to disagree, or there are arguments that the other side doesn't understand each other, that they are arguing at cross-purposes, etc. then the layperson will tend to side with the guy with the C.V.

Edit: I have noted the comment by neum on the article at the bottom of the page in the link above. This is the sort of comment that commends itself as the beginning of a debate the VP-real defenders must answer to.

After some googling, I hit upon this thread right here at PF
https://www.physicsforums.com/showthread.php?t=75307&highlight=virtual+particles&page=3

Well, I don't know about Hrvoje Nikolic's credentials but I take sides with Wilczek, t'Hooft, Callan, Peskin, Pollitzer and Susskind!

Here is Wilzcek view from https://www.physicsforums.com/showpost.php?p=3016157&postcount=36

It comes down to what you mean by "really there". When we use a concept with great success and precision to describe empirical observations, I'm inclined to include that concept in my inventory of reality. Buy that standard, virtual particles qualify. On the other hand, the very meaning of "virtual" is that they (i.e., virtual particles) don't appear *directly* in experimental apparatus. Of course, they do appear when you allow yourself a very little boldness in interpreting observations. It comes down to a matter of taste how you express the objective situation in ordinary language, since ordinary language was not designed to deal with the surprising discoveries of modern physics.

 

[Lapidus]

Or Lisa Randall, as I pointed out a few weeks ago!

https://www.physicsforums.com/showpost.php?p=3240965&postcount=86

Again, I do not know about credentials of all the pf posters, Hrvoje Nikolic or A. Neumaier , but as a humble layperson I go with the just mentioned.

 

[Polyrhythmic]

Physics Forums is strongly associated with Scientific American, wherein a highly qualified expert says (2006) that virtual particles are flat-out real, and he doesn't mince words:

http://www.scientificamerican.com/article.cfm?id=are-virtual-particles-rea
['rea' sic. That's a valid URL]

This article is flawed, for reasons given for example in comment #10.

 

[Polyrhythmic]

Or Lisa Randall, as I pointed out a few weeks ago!

https://www.physicsforums.com/showpost.php?p=3240965&postcount=86

Again, I do not know about credentials of all the pf posters, Hrvoje Nikolic or A. Neumaier , but as a humble layperson I go with the just mentioned.

As a humble layperson, you should either start studying the theory before arguing false opinions or simply admit that you are not in the position to judge. "xy said it" is no reason for something to be true.

 

[danR]

Or Lisa Randall, as I pointed out a few weeks ago!

https://www.physicsforums.com/showpost.php?p=3240965&postcount=86

Again, I do not know about credentials of all the pf posters, Hrvoje Nikolic or A. Neumaier , but as a humble layperson I go with the just mentioned.

Lisa Randall seems well-qualified to have an expert opinion on the matter, and she knows how to gear it down to popular prose, and she appears to side with the 'real' camp.

Perhaps it's better to draw up a weighted checklist of properties, interactions, states, lifetimes, wavelengths, spaces, taxonomies, etc. for all particles and check off what gets a check, the weight of the check and add it all up for all particles.

A lump of sugar would probably get a high 'real' rating, a gold nucleus would do pretty good, an unmeasured electron OK, a 1 metre photon a passing grade, a virtual electron, nyaah...


Perhaps some particles are more real than others. Perhaps 'realness' is a continuum.

 

[maverick_starstrider]

Lisa Randall seems well-qualified to have an expert opinion on the matter, and she knows how to gear it down to popular prose, and she appears to side with the 'real' camp.

Perhaps it's better to draw up a weighted checklist of properties, interactions, states, lifetimes, wavelengths, spaces, taxonomies, etc. for all particles and check off what gets a check, the weight of the check and add it all up for all particles.

A lump of sugar would probably get a high 'real' rating, a gold nucleus would do pretty good, an unmeasured electron OK, a 1 metre photon a passing grade, a virtual electron, nyaah...


Perhaps some particles are more real than others. Perhaps 'realness' is a continuum.

I don't see how there could be such a "real" following. If tomorrow somebody figured out how to solve functional integrals of non-gaussian functions there'd really be no room for debate, the entire concept would simply go away would it not? The reality of something shouldn't depend on the mathematical approach taken. To put it out there again, if something calculates and experiments as "Q" then how could you say it's actually "Q+A-A+C-C+3D-D-2D"? It's just a meaningless contrivance.

 

[danR]

I don't see how there could be such a "real" following. If tomorrow somebody figured out how to solve functional integrals of non-gaussian functions there'd really be no room for debate, the entire concept would simply go away would it not? The reality of something shouldn't depend on the mathematical approach taken. To put it out there again, if something calculates and experiments as "Q" then how could you say it's actually "Q+A-A+C-C+3D-D-2D"? It's just a meaningless contrivance.

Now it's over my head. The way Randall puts it sounds similar to Asimov's popular description 40 years ago, and ran something like: virtual particles shouldn't exist because they are contrary to the laws of physics, but because of Heisenberg, they can get away with breaking the law because they are so short-lived no one is around soon enough to enforce it.

But that's no evidence they do exist. I find it odd that two physics heavyweights find them parsimonious enough to let them live, though the SA (2006) argument sounds deplorably pop-sciencey, something like: 'Well, the Casimir effect shows they exist.'

Here's another layperson-way of weighting the evidence: do the proponents depend on internally consistent, well accepted, standard theories for VP's 'reality' (loosely defined)? How similar is their definition of 'real' space that virtual particles inhabit to that of educated average people's realist views of space? Or is it a momentum-space that is so familiar to physicists that it seems real enough, like mathematician's imaginary number 'i' is to mathematicians? (This was an educated argument against acceptance, in lay terms, of the 'proof' of Fermat's last theorem.)

Do critics depend on the gratuitousness of VP by cherry-picking theories that specifically invoke alternative mechanisms, which theories contradict each other, or mainstream theories? Or are less parsimonious than the offending VP themselves? That's not something I would be able to figure out.

Naturally, scientists aren't required to satisfy public understanding of esoteric things, however. In my own area, there is something called 'Optimality Theory' that has gained wide acceptance for explaining the abstract representations of sound in the mind, but it is hopelessly hard to explain. Students spend the first few weeks scratching their heads over it.

I have a course starting soon, and can't do much more on PF for a while, regrettably.

 

[maverick_starstrider]

Now it's over my head. The way Randall puts it sounds similar to Asimov's popular description 40 years ago, and ran something like: virtual particles shouldn't exist because they are contrary to the laws of physics, but because of Heisenberg, they can get away with breaking the law because they are so short-lived no one is around soon enough to enforce it.

But that's no evidence they do exist. I find it odd that two physics heavyweights find them parsimonious enough to let them live, though the SA (2006) argument sounds deplorably pop-sciencey, something like: 'Well, the Casimir effect shows they exist.'

Here's another layperson-way of weighting the evidence: do the proponents depend on internally consistent, well accepted, standard theories for VP's 'reality' (loosely defined)? How similar is their definition of 'real' space that virtual particles inhabit to that of educated average people's realist views of space? Or is it a momentum-space that is so familiar to physicists that it seems real enough, like mathematician's imaginary number 'i' is to mathematicians? (This was an educated argument against acceptance, in lay terms, of the 'proof' of Fermat's last theorem.)

Do critics depend on the gratuitousness of VP by cherry-picking theories that specifically invoke alternative mechanisms, which theories contradict each other, or mainstream theories? Or are less parsimonious than the offending VP themselves? That's not something I would be able to figure out.

Naturally, scientists aren't required to satisfy public understanding of esoteric things, however. In my own area, there is something called 'Optimality Theory' that has gained wide acceptance for explaining the abstract representations of sound in the mind, but it is hopelessly hard to explain. Students spend the first few weeks scratching their heads over it.

I have a course starting soon, and can't do much more on PF for a while, regrettably.

Well first of all Isaac Asimov certainly was not a "heavy-weight" of physics, he wasn't even a physicist. He was a bio-chemist and a science fiction writer. Also, virtual particles are not needed to explain the Casimir effect. Essentially the issue is something like this. Imagine the function

e^x

the exponential of x, it'll be on any scientific calculator you can just pick various values of x to see what its value is. Now what if I told you that for any value of x the following will give exactly the same answer:

1 + x + \frac{x^2}{2} + \frac{x^3}{6} + \frac{x^4}{24} + \ldots

where the ellipsis means you keep adding terms, to make things easier only consider values of x that are less than 1, then a number less than 1 raised to some power becomes an even smaller number. Thus we see that each of these terms (the next would be

\frac{x^5}{120}

then

\frac{x^6}{720}

and so on) is going to be a smaller number (try it on a calculator if you like, try something like 0.3 so you'd type in exp(0.3) and get the answer and then you try the infinite sum and you'd get

1 + 0.3 + \frac{0.3^2}{2} + \frac{0.3^3}{6} + \ldots

and you'll see as you add more and more terms you'll get closer and closer to the answer exp(0.3) gave. This is called a TAYLOR SERIES or TAYLOR APPROXIMATION. If you actually include and infinite number of terms (i.e. x^5,x^6,x^7,x^8,\ldots) it is EXACTLY e^x. However, if you only care about, say only the first 5 decimal points, then you can get away with only having to calculate a dozen or so terms, the terms after that are so small they only effect decimal positions further away.

This is basically the situation, no dumbing down, we have an equation like

e^x

and we want to do something to it (what's called a functional integral) but we can't. We don't know how. However, we CAN do it to each of the terms in the series form:

1 + x + \frac{x^2}{2} + \ldots

and the more terms we do it to the more accurate we are (obviously we could never ACTUALLY sum all the infinite terms). Now, imagine the math of x looked kinda but not really like the math of a particle moving in a vacuum and the math of \frac{x^2}{2} looked kinda but not really like that of two particles moving with opposite momentum or some such and so it goes for the next term and the next term.

Now, saying that virtual particcles are "real" is basically saying that these terms represent real-life goings on of magical new particles. The thing is, if we could just integrate e^x in the first place then there'd be nothing to debate and we'd never have even heard of the concept of virtual particles much less insist that they're part of reality. However, since we CAN'T write down the answer to that guy and have to move to an approximation scheme than, allegedly, the very nature of reality magically changes. Now, let me ask you Does it make sense to say that reality changes because your math skills aren't good enough to get the direct answer you want so you're forced to move to approximations? I would say no. Virtual particles are a calculational tool, not reality, they're a way we can mathematically get the answer we want to arbitrary accuracy, they're not new physics.

 

[byron178]

Don't virtual particles time travel backwards?

 

[haushofer]

Don't virtual particles time travel backwards?

Why would they?

 

[Lapidus]

Well first of all Isaac Asimov certainly was not a "heavy-weight" of physics, he wasn't even a physicist.

Wilczek, t'Hooft, Randall, Kane certainly are.

Virtual particles are a calculational tool, not reality, they're a way we can mathematically get the answer we want to arbitrary accuracy, they're not new physics.

How are we to explain static electric and magnetic fields if virtual photons are just a mathematical artifact?

 

[tiny-tim]

hi byron178!

Don't virtual particles time travel backwards?

i think you're thinking of anti-matter …

eg an electron going forward in time behaves exactly the same as a positron going backward in time, both in Feynman diagrams and in the equations

(and a creation operator for an electron behaves like an annihilation operator for a positron, and vice versa)

 

[danR]

Well first of all Isaac Asimov certainly was not a "heavy-weight" of physics, he wasn't even a physicist. He was a bio-chemist and a science fiction writer. Also, virtual particles are not needed to explain the Casimir effect. Essentially the issue is something like this. ...

...Virtual particles are a calculational tool, not reality, they're a way we can mathematically get the answer we want to arbitrary accuracy, they're not new physics.

I know all about Asimov: he was a popularizer; my point was that Asimov's popular explanation differs little from the Harvard heavyweight's one. It seems to be a good-enough defense for real-particle status. Both the Harvard woman, and the SA writer are experts in the field, and the latter specifically addresses the 'are they just a mathematical bookkeeping device?' He says resoundingly NO! They are real particles. I'm just not happy with his casual Casimir defense, but I'm confident that he is sufficiently familiar with the literature to know whether or not the mathematical-artifact arguments are sufficient to the evidence. If anyone presumes to speak ex cathedra on the non-real existence of VP, I'm sure they will be happy to debate the weighty proponents publicly.

Don't lose my real point. It's not whether you are right or wrong, it's the credentials of experts in the field who appear to be comfortable with VP-real. I have to pay attention to their weight, and compare it with that of the critics.

Someone in a post stated they did actually poll the experts in an email, but whether the responses should be published here seemed to be an issue.

But from what I see of expert opinions, VP-real seems to be an OK position

 

[danR]

Wilczek, t'Hooft, Randall, Kane certainly are.

Yes, my point was that Randall hardly differed from Asimov in the surface form of her popularized argument. I know very well Asimov was a popularizer. In his day most would not have called him a scientist, even a biochemical scientist.

I have the feeling that the above experts would know a thing or two about the 'math-artifact' arguments, and would be able to counter them. If they have countered them in print, then some research is in order by critics to pull some of that print into physics forums and disassemble them.

 

[Polyrhythmic]

Yes, my point was that Randall hardly differed from Asimov in the surface form of her popularized argument. I know very well Asimov was a popularizer. In his day most would not have called him a scientist, even a biochemical scientist.

I have the feeling that the above experts would know a thing or two about the 'math-artifact' arguments, and would be able to counter them. If they have countered them in print, then some research is in order by critics to pull some of that print into physics forums and disassemble them.

I honestly have no idea why those experts would advocate the reality of virtual particles, other than maybe just because it seems like a beautiful explanation. Particles buzzing back and forth. Neat.
But still, the concept of logical reasoning is clearly against the concept of virtual particles, as shown by countless arguments in this thread.

 

[Lapidus]

virtual particles are talked about only in perturbation theory

"a particle that does not obey E² - p².c² = m².c⁴ for a time allowed by the energy-time uncertainty relation" is just science fiction writing, much like "a spaceship that goes faster than light", or "Heisenberg compensators" … you can't just string words together, you need to be able to insert the idea into a theory

Check out science fiction by Leonard Susskind, starting around min 43 till around min 74.

http://www.youtube.com/watch?v=5rytN74EOi0&feature=player_embedded#at=3359

I think, he is very clear that it is an interpretational issue.

 

[byron178]

hi byron178!


i think you're thinking of anti-matter …

eg an electron going forward in time behaves exactly the same as a positron going backward in time, both in Feynman diagrams and in the equations

(and a creation operator for an electron behaves like an annihilation operator for a positron, and vice versa)

Does that mean they really travel backwards?i was asking if they can travel backwards in time because they can travel faster than light,they become space-like.

 

[Polyrhythmic]

Does that mean they really travel backwards?i was asking if they can travel backwards in time because they can travel faster than light,they become space-like.

That's a matter of interpretation, but I'd rather stick with the forward-in-time one. They don't travel faster than light.

 

[maverick_starstrider]

Does that mean they really travel backwards?i was asking if they can travel backwards in time because they can travel faster than light,they become space-like.

It's ultimately an issue of an extra minus sign floating around. You can tuck it into the velocity and say it's moving backwards or you can tuck it into the charge and say it behaves like an electron in every way except it has the opposite charge. It's conceptually much simpler to just tuck it in with the charge.

 

[tiny-tim]

Does that mean they really travel backwards?i was asking if they can travel backwards in time because they can travel faster than light,they become space-like.

no, anti-matter travels slower than light, just like matter (but, as i said, it behaves like matter at the same speed but going backwards in time)

also, motion faster than light (in other words, space-like motion) would not involve going backward in time …

this is a science fiction error, caused by saying that since time dilation of √(1 - (v/c)²) goes from 1 to 0 as v approaches c, that means it must become negative if v > c … and that obviously isn't true! ​

 

[maverick_starstrider]

no, anti-matter travels slower than light, just like matter (but, as i said, it behaves like matter at the same speed but going backwards in time)

also, motion faster than light (in other words, space-like motion) would not involve going backward in time …

this is a science fiction error, caused by saying that since time dilation of √(1 - (v/c)²) goes from 1 to 0 as v approaches c, that means it must become negative if v > c … and that obviously isn't true! ​

Yes, the energy of a particle going faster than the speed of light is actually complex (i.e. has an imaginary component, i.e. a+bi). What could a complex energy possibly mean? Well luckily there's no evidence for the existence of such particles so we don't really have to attempt to make any sense out of such a mind bogglingly out there concept.

 

[maverick_starstrider]

BTW, If you want to talk about heavy-hitters and there opinions here's a lecture I was just watching by Anthony Zee (of "Quantum Field Theory in a Nutshell" fame)

http://v.youku.com/v_show/id_XMTE0OTI4Nzg0.html

Check around the 45 minute mark. He goes on to talk about how the concept of Feynman Diagrams (i.e. virtual particles) "shackled" the study of QFT for quite some time. it wasn't until people like t'Hooft pointed out that there exist phenomena (such as magnetic monopoles) that CANNOT be described through the perturbative framework that virtual particles represent, that QFT began to free itself from the "shackles of Feynman Diagrams". Putting words in his mouth a bit he's basically saying that not only are these perturbation not real things but for a 30 year stretch or so they were blinding people to the real physics by taking these things too seriously.

 

[byron178]

no, anti-matter travels slower than light, just like matter (but, as i said, it behaves like matter at the same speed but going backwards in time)

also, motion faster than light (in other words, space-like motion) would not involve going backward in time …

this is a science fiction error, caused by saying that since time dilation of √(1 - (v/c)²) goes from 1 to 0 as v approaches c, that means it must become negative if v > c … and that obviously isn't true! ​

there is this article i found that say's they do time travel backwards in time. http://www.desy.de/user/projects/Physics/Quantum/virtual_particles.html

 

[maverick_starstrider]

there is this article i found that say's they do time travel backwards in time. http://www.desy.de/user/projects/Physics/Quantum/virtual_particles.html

That's what he said. Going backwards in time and going faster than light are entirely different things. Whether you're going backwards down a one way street in a car or whether your car is going over 100 miles per hour have nothing to do with each other. Mathematically there is no difference between saying that anti-particles are particles with the same charge moving backwards in time or particles with opposite charge moving forward in time. In neither case is it being suggested that they are moving FASTER than the speed of light.

 

[tiny-tim]

there is this article i found that say's they do time travel backwards in time. http://www.desy.de/user/projects/Physics/Quantum/virtual_particles.html

but that has nothing to do with moving faster than light …

it's just the example i mentioned earlier, of an anti-particle behaving like a particle going backward in time (in this case, a photon, which of course is its own anti-particle)

 

[tiny-tim]

Lapidus, i claim that Susskind suppports me! … Susskind specifically says that virtual particles are mathematical constructs, that virtual particles popping into existence are a "picture", and gives an example of an electron containing a hydrogen atom that seems clearly intended to rubbish the idea …

Check out science fiction by Leonard Susskind, starting around min 43 till around min 74.

(that's Lecture 6 (February 15, 2010) of Susskind's Stanford University course "New Revolutions in Particle Physics: The Standard Model")

at 0:55 he is asked "exactly what is the difference between a real and a virtual particle?", and he says

"virtual particles are mathematical constructs which are the internal particles in a Feynman diagram"​

(he then goes on to describe how if they existed we wouldn't be able to detect them, but i hope you're not claiming that proving that they're undetectable somehow proves that they exist?! )

later, he mentions the picture of a proton continually oscillating into a W plus a neutron and back again, so that an energetic enough photon can knock the W out, leaving the neutron, and someone asks him (around 1:03) whether that means the W was already there, and he replies

"your mental picture that whatever comes out of a system was in there beforehand is a little bit defective!"​

I think, he is very clear that it is an interpretational issue.

what does that mean?

Susskind says that the existence of a virtual W is a "picture", and he then goes on to show how absurd the picture is

the only unequivocal thing he says is (at the very start) that "virtual particles are mathematical constructs"

 

[byron178]

but that has nothing to do with moving faster than light …

it's just the example i mentioned earlier, of an anti-particle behaving like a particle going backward in time (in this case, a photon, which of course is its own anti-particle)

but they don't really travel backwards in time,right?

 

[tiny-tim]

but they don't really travel backwards in time,right?

right!