How does atom looks like?

this was a question that friend of mine asked me on one contest I was this weekend. I was sure with the answer but after I said it I was not able to come up with the reason for it, at least I was not sure enough to say something clear.

So what exactly needs to happen for you to see it? There must be a photon which is reflected off the surface. How does this look like anyway on the atomic level? Well the light hits some electron in its way. There is lot of free space so this is why things that are not transparent can be if they are thin enough. The electron absorbs the photon, jumps to higher level (excitation), then it emits photon. Now on what you see depends upon its wavelength. So different materials will like to absorb different wavelengths making the object to have color. You can only change in what orbital you will have the electron so I guess that this is the fundamental difference between various colors of objects (though I did not check it).

So when electron emits the photon you simply do not know what the electron looked like. The only thing that you can get is just photon of some wavelength and there simply is not any way to look on some kind of surface of electron. Another factor is that the light has too big wavelength and you can not observe surface with that because the photon kind of just flows around and when you get to wavelength of the size of atom or smaller, the energy of the photon is so huge that the electron is anyway blown away.

There is nucleus too of course and normally photons do not get there because of this electron cloud around and nucleus is tiny. Otherwise from what I found it seems that again the proton and nucleus as whole is way too small and you can not actually map the surface.


But I was talking only about electrons and nucleus. You can actually see atom as whole. Not by microscope because visible light is way to huge. There is what is called Abbé difraction limit so you have to look for atoms in different way, using for example electrons (electron microscopes[1]) and then recreate the image using some cool physics, this is for example picture of silicon carbide:

And the one below is picture made by IBM of individual atoms that are shaped like the letters of IBM.

So while you can not see the atom, you can observe, not electron though or even the nucleus at least in ordinary way. You can for example measure energy or calculate the shape but you can not see them as physical objects.


[1]Electron microscopes observe how electrons bounce of the surface just like photons.

Read more: 1) 2) 3)


The shape of Radium-224 nucleus


Taking closer look on, NOTHING!

in this post I want to look on literal nothingness, vacuum, empty space.
And why are neutron stars so freaking dense.

When you put your hands as far away from the other one and imagine that this is the volume of atom the nucleus is going to be thinner than the diameter of human hair.. well yes, that escalated quickly. And I am not even talking about electrons which are much smaller than protons and neutrons.

This simply means that you are, and everything you know, is mostly made up of empty space.

Now for the neutron stars.
Neutron stars are collapsed massive stars. They are extremely small and dense at the same time and the gravity of all the stuff keeps this stable.
Wow, neutron star is pretty scary when you take that their diameter ranges from 10-20 kilometers and at the same time they have 1.35 to 2.1 of Solar mass. The first picture corresponds to this, so if you would compress all humanity to size of sugar cube it would be as dense as neutron star. So in neutron star there is not much of empty space.

That is all for neutron stars but let me return to the empty space and vacuum.

Vacuum is extremely important, while I don’t want to list all technology using it, let me say that for example simple straw is working because of vacuum.
While you are not making the best vacuum ever, when drinking your juice from straw, you are lowering the pressure so the juice runs up. If you would lower the pressure a lot like in space this effect would be much stronger (you would not explode).

There is actually scale on Wikipedia about the levels of vacuum. OK now lets assume that you would be able to suck out all of the air and stuff inside closed box.
Is there going to be something?

Yes, it may sound strange but there is lot of stuff, and this stuff likes to change a lot.

Lets introduce you virtual particles!
OK, they are real kind of, at least it is known that they really exist. They have to do a lot with quantum theories like quantum field theory.. I do not understand any of it but that is not really important right now.

Virtual particles are particles that are popping in and out of existence all the time. In this kind of way they should be in pairs which then both disappear in nearly NO time. I read that since they are so virtual and may not carry any energy or momentum they may even travel faster than light or travel in time (this is questionable, as you will see (source Wikipedia)). Those particles are made in pair, one of them is anti particle so they then collide and annihilate.
For example there are virtual photons that actually do any kind of electromagnetic radiation, so photons are called force carriers of e. m. radiation. I already wrote about this earlier..

OK, I know that there must be something more to it since at the same time SOME virtual particles can travel faster than light as Wikipedia says, while force can not be transferred faster than the speed of light.

So there is all the stuff popping in and out of existence which is constantly annihilating. But when this happens on the edge of black hole when one particle is inside the event horizon and the other one outside, the one outside does not annihilate and it pops into existence and escapes the black holes gravity. Since conversation of mass/energy this must have taken something from the black hole. This really happens in what is called Hawking radiation, when eventually black hole can evaporate!
To watch something more about vacuum, check this video by Veritasium where he is talking about quantum fluctuations.


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