Has the atom been directly observed?

[Gregori Umbranox]

Okay, because I don't like google, I throw this out in the forums. Has the atom been directly observed or is it still theory? And by diectly observed, I mean have they seen the electron cloud and the nucleus.

[Miss Boom]

I believe the Scanning Tunneling Microscope is the closest anyone's come to 'seeing' the atom.

The rest of it has been directly detected but I don't think it's actually been observed in the visual sense.

[Gregori Umbranox]

Thank you, that is what I was wondering.

[vipr230]

William Umbranox

Okay, because I don't like google, I throw this out in the forums. Has the atom been directly observed or is it still theory? And by diectly observed, I mean have they seen the electron cloud and the nucleus.

You're dealing with a diameter of around 5fm for atomic nuclei... that's 5*10^-15m

Lets look at resolution...

http://ncem.lbl.gov/TEAM-project/files/what.html

The most powerful microscope in development is capable of resolution of .5 angstrom, that's .5*10^-10 m

In other words, the best microscope we are trying to create is still 4 orders of magnitude away from being able to resolve the diameter of an atomic nucleus. We're FAR from being able to see an atomic nucleus.

Not only that, but even if we do "see" it using an electron microscope (which I've got my doubts is even physically possible, the maximum resolution practically conceivable I'm not so sure would be capable of seeing on the fm resolution scale) that still won't "prove" atoms exist.

"Theory" is the highest form of an idea in science, we've directly observed cells but it's still called "cell theory". There's no "proof" for a cell, atom, electron, etc, it's all "theory" but "theory" is given the highest respect in science.

Even if we did have a microscope with fm resolution power, we'd still say "atomic theory".

[Whom]

You still can't make out the electron cloud or nucleus with this, but you can make out individual atoms on a surface using atomic force microscopy. Here's a picture of some individual sodium and chloride ions on an atomic force micrograph of a salt crystal (from the Wiki page):

http://upload.wikimedia.org/wikipedia/commons/e/ed/AFM_view_of_sodium_chloride.gif

[CornBursts]

A few of the people above me seem to have forgotten about things like particle accelerators. That or they are interpreting your question to include only optical wavelengths heheh.

Anyway my point is that atoms, like cells, have such a ridiculously large amount of evidence for their existence that it would be silly to claim either are not proven too exist despite the fact that atoms are typically not resolved in the optical (what humans see) wavelength. (Though cells CAN and have recently been resolved in the optical wavelength).

In particle accelerators we can detect very precisely the presence of electrons, anti-electrons (positrons), protons and neutrons (the particles in the atomic nucleus) and more and distinguish them all from one another. We can even detect particles made up of only 2 quarks emerging from colliding nuclei. Protons and neutrons are made up of 3 quarks. Single quarks are a little more tricky but I believe within the past year we have found them a couple times. I may remember incorrectly but I can find the link to that article if you like.

So not only can we detect atoms, but we can detect many of their constituent parts and have been doing so for decades. =)

I hope this helps!

P.S. A good example of detection of SUBatomic particles, that is, the particles that make up atoms, is in bubble chambers. Feel free to google image bubble chamber. =D

[vipr230]

CornBursts

A few of the people above me seem to have forgotten about things like particle accelerators. That or they are interpreting your question to include only optical wavelengths heheh.

Electron microscopes do not use optical wavelengths, that usually refers to visible light and has a rather low resolution power compared to using things with much smaller wavelengths. However, when referring to "directly observed", that usually refers to our ability to resolve an object, hence we're sticking to ways to "see" atoms, not simply prove/support their existence. The OP was confused as to the importance of "seeing" an atom, but to me, that's unimportant.

Quote:

Anyway my point is that atoms, like cells, have such a ridiculously large amount of evidence for their existence that it would be silly to claim either are not proven too exist despite the fact that atoms are typically not resolved in the optical (what humans see) wavelength. (Though cells CAN and have recently been resolved in the optical wavelength).

Like I said, the most powerful microscope on the planet does not have the resolution capability to resolve an atom, it's not "typically", it's fundamentally impossible to do so with optical light. Why? The diffraction limit... because given that the lowest wavelength you can use is still 450nm, in practice it's damn hard to get an optical microscope that can resolve 200nm or smaller. That's 2x10^-7, to resolve an atom, like I said, you need to be able to resolve on the fm scale, about 8 orders of magnitude away.

It's not just "typically not resolved optically", it's fundamentally impossible, the wavelength of optical light is simply too large.

... Cells, by the way, have been resolved for quite some time... Robert Hooke did so in the 1600s. He only had an optical microscope.

Quote:

In particle accelerators we can detect very precisely the presence of electrons, anti-electrons (positrons), protons and neutrons (the particles in the atomic nucleus) and more and distinguish them all from one another.

Perhaps for our less informed readers you might want to elaborate on the workings of particle colliders. You are aware the mechanisms for detecting fundamental particles in colliders is VASTLY different from the entire process of "viewing" or "seeing" a particle, right? Lemmy give you a hint, on the ATLAS experiment there is a reason they have more than one calorimeter.

Quote:

We can even detect particles made up of only 2 quarks emerging from colliding nuclei.

I think you're talking about Mesons, but I'm gonna be technical and correct you, they're made up of a quark and an antiquark, just in case it isn't obvious to the readers. I don't believe I've ever heard of a plain 2 quark particle, but, this isn't my field of expertise so I'd be happy if morbie or lost correct me ^^;

Quote:

Protons and neutrons are made up of 3 quarks. Single quarks are a little more tricky but I believe within the past year we have found them a couple times. I may remember incorrectly but I can find the link to that article if you like.

It's not difficult to detect quarks either, we've got 6 different "flavors", and we see them a lot more often than a few every year. up, down, top, bottom, strange and charm. The Top quark I believe was the most recently detected, it was found over 10 years ago thanks to the Tevatron. (Lost Iguana can fill in a lot more details on this I'm sure)

Quote:

So not only can we detect atoms, but we can detect many of their constituent parts and have been doing so for decades. =)

I hope this helps!

I hope you now understand there is a difference between "detect" and "see". Just because you can detect a particle does not mean you can see it, we're still well off from being able to resolve things on the fm scale.

[CornBursts]

Re: Vipr320

I won't bother quoting your post since most of your replies come down to a simple misunderstanding between us and perhaps myself and the OP. What I asked in my first sentence was really what he meant by see or detect. While I know of the difference between the two, I'm not sure the OP did in this particular context. As such I wanted to describe other ways we detect these particles.

I could have described particle accelerators more but I am not sure that is really what the OP is asking for heheh.

Also I apologize if you misunderstood by what I meant when I said atoms are not typically resolved optically. I'm familiar with the fact that their wavelengths are longer than the typical atomic diameter and so you wouldn't use them to see individual atoms. I just didn't want to accidentally give the OP the impression that they are useless in atomic research. =)

As for cells being seen in the optical wavelength, I never meant to refer to typical microscopes, and that's why I never mentioned them heheh. Sorry for the misunderstanding again! This is more what I was referring too:

Distinguishing single cells with nothing but light

Oops and I almost forgot. I'm not sure what you thought I meant about single quarks. I'm familiar with the flavors and all that jazz. Anyway the point was that it has been rather difficult to detect a single quark all by itself. Though in recent years it seems we have done so. Here's an article about the top quark being experimentally seen. Cool stuff!

Rare Single Top Quark Discovered In Collider Experiments

Thanks, vipr320! I hope the OP has a better idea of things now. =)

[A Lost Iguana]

CornBursts

Oops and I almost forgot. I'm not sure what you thought I meant about single quarks. I'm familiar with the flavors and all that jazz. Anyway the point was that it has been rather difficult to detect a single quark all by itself. Though in recent years it seems we have done so. Here's an article about the top quark being experimentally seen. Cool stuff!

Rare Single Top Quark Discovered In Collider Experiments

The top has been experimentally seen since 1995. "Single top" is not the same thing as a finding a single quark. "Single top" is hard to see because it is a very very rare process, not because it's hard to detect a single quark. Strictly speaking, it is impossible to detect a quark directly, they break apart into collimated "jets" of colour-neutral hadrons because free coloured particles are forbidden. In any process where you end up with a quark leaving your interaction it will decay into a stream of hadrons that you measure in your detector. Look at the Feynman diagram of the process: a quark emits a W boson that interacts with one of the bottom pair created from the gluon. The two extra bottom quarks also decay into jets along with the top that is produced from the bottom-W interaction. It is a three-jet event, not a one-jet event (this ignores the five spectator quarks that would also hadronise from the proton and antiproton).

Single top involves a gluon-quark interaction like you would get at the LHC — it collides protons into protons so you would get quark-gluon and gluon-gluon — so it is interesting as qg -> bb-bar + X is the sort of process that would make a Higgs boson. I would think that single top is a background process to LHC Higgs studies so understanding it is important (remember that the top is about 175 GeV which is at little heavier than you'd think a Higgs would be).

[vipr230]

CornBursts

Re: Vipr320

I won't bother quoting your post since most of your replies come down to a simple misunderstanding between us and perhaps myself and the OP. What I asked in my first sentence was really what he meant by see or detect. While I know of the difference between the two, I'm not sure the OP did in this particular context. As such I wanted to describe other ways we detect these particles.

I could have described particle accelerators more but I am not sure that is really what the OP is asking for heheh.

Also I apologize if you misunderstood by what I meant when I said atoms are not typically resolved optically. I'm familiar with the fact that their wavelengths are longer than the typical atomic diameter and so you wouldn't use them to see individual atoms. I just didn't want to accidentally give the OP the impression that they are useless in atomic research. =)

As for cells being seen in the optical wavelength, I never meant to refer to typical microscopes, and that's why I never mentioned them heheh. Sorry for the misunderstanding again! This is more what I was referring too:

Distinguishing single cells with nothing but light

Oops and I almost forgot. I'm not sure what you thought I meant about single quarks. I'm familiar with the flavors and all that jazz. Anyway the point was that it has been rather difficult to detect a single quark all by itself. Though in recent years it seems we have done so. Here's an article about the top quark being experimentally seen. Cool stuff!

Rare Single Top Quark Discovered In Collider Experiments

Thanks, vipr320! I hope the OP has a better idea of things now. =)

As far as I'm concerned, spectroscopy is vastly different from "seeing" a cell, which is concerning angular resolution. With spectroscopy you're looking to see how the light bounces off to get an idea of the different molecules in play, you're getting a more complete picture than simply "seeing" the cell. So don't get me wrong, I consider spectroscopy to be more interesting than merely "seeing" an image, but you used the wrong terminology, you said the cell had recently been resolved optically, that is incorrect, it had been resolved optically by Hooke, being able to preform Raman spectroscopy on a cell just gives us extra information.

I don't mean to be nit picky, but terminology is important.

And Lost, if the Higgs is indeed lighter than the top, does that mean the top is the most massive elementary particle? (You said the Tevatron recently ruled out high mass Higgs right?)

[A Lost Iguana]

The top is huge. It's so large is decays before can form a bound state with another quark. It is possible that you have a larger Higgs in some supersymmetric extensions of the standard model. Anyway, yes, it is the largest elementary particle we know about or have predicted (ignoring supersymmetric particles we have not been able to make or Kaluza-Klein resonances).

[vipr230]

A Lost Iguana

The top is huge. It's so large is decays before can form a bound state with another quark. It is possible that you have a larger Higgs in some supersymmetric extensions of the standard model. Anyway, yes, it is the largest elementary particle we know about or have predicted (ignoring supersymmetric particles we have not been able to make or Kaluza-Klein resonances).

I see, and yet it's still easier to detect than the higgs, I assume it's not just the higgs being a heavy particle that makes it more elusive than the top.

[A Lost Iguana]

vipr230

I see, and yet it's still easier to detect than the higgs, I assume it's not just the higgs being a heavy particle that makes it more elusive than the top.

Mass sets a kind of hard limit on what you can produce. If you don't have the energy to produce particles you will not see them (short of highly virtual variants with lower mass than the real kind). In this case it's not the mass that's the issue, it's the low number of interactions that would occur and then being able to separate them out from the similar looking processes. Remember that you need to identify objects just from the energy they dump into calorimetry devices and the paths they leave in tracking chambers, then try to work out what they came from.

[vipr230]

Which is why the top seems so hard to detect, as you said, it's a rare interaction. I would ask why the higgs is such a rare interaction, but I'd venture my QM background is far from sufficient to be able to understand the answer sweatdrop

Hopefully that will change ^_^

[The Xzr Xza of Conor Olaf]

According to what the buzz has been, it's a matter of the detectors being able to detect at the energy scales needed to see if this hypothetical bugger is there.
Then they should be seeing quite a bit of them, or I would suppose they would, if it is partially responsible for helping to give mass to the rest of the particles- including the Higgs itself.


But I could be wrong. It could just not be there. That would make it really hard to see.