What is quantum tunneling?
by David Colarusso - March 25th, 2007
Einstein may have believed God doesn’t play dice, but God need not conform to Einstein’s beliefs. This piece explores the phenomenon of quantum mechanical tunneling whose explanation requires us to accept the reality of quantum mechanics. It’s not a trick; it’s reality.
Update: People have been asking for the math. So here it is. The Sun’s core temp is ~13.6 MK. For hydrogen nuclei the Coulomb barrier is roughly 0.1 MeV. This corresponds to a temperature in excess of 1 GK! Luckily, tunneling and the distribution of speeds among nuclei lower the actual temperature required. So without tunneling even the Sun’s core isn’t hot enough for fusion. To see most of this worked through, check out this link:
http://burro.cwru.edu/Academics/Astr221/StarPhys/coulomb.html
for a less mathematical explanation, try:
http://en.wikipedia.org/wiki/Nuclear_fusion#Requirements
Transcript:
The Tabletop Explainer
Episode Six (6)
What is quantum tunneling?
Some of us were taught in high school that the electron orbits around the nucleus like a planet around the sun. However, this description has been understood as a gross mis-representation for the better part of the last century. As it turns out, there is a characteristic uncertainty related to the very small. No one can tell exactly where something is; the best one can do is figure out where something is most likely to be. We can visualize this with something called a probability cloud. Here we see the probability cloud of a proton at the center of a hydrogen atom. The denser regions are where the proton is more likely to be found. However, this uncertainty is not due to an inability of ours to measure the small in an exact manner; it is a fundamental aspect of the world in which we live, and its implications are extraordinary.
Let us take for example the phenomenon of tunneling. If we can’t tell exactly where something is then it follows that we can’t tell exactly where it’s been or where it will be. The best we can hope for is where it most probably will be. So there’s a small chance that a racket ball thrown repeatedly at a barrier could just tunnel through the barrier, appearing almost magically on the other side. We don’t see this often because a racket ball’s pretty big and its uncertainty pretty small. But if we deal with matter on the subatomic scale it becomes much more likely. Here our projectile approaches the barrier, we see here its probability cloud, although it’s most likely near the center of the cloud we can see that there is a small chance of it being on the other side of the barrier, and so sometimes it is. Tunneling isn’t a mathematical trick or an assumption, it’s an observable fact. It’s made use of commonly in modern electronics and in a real way allows for life on earth. To see why, let us trace the creation of a photon in the sun. The light from the sun that we see reflected off the moon, the light which drives the earth’s weather, that provides the energy for life all originates from the process of nuclear fusion in the sun. Two light atomic nuclei collide, forming a new element, and in the process light is released. But these nuclei are both positively charged and so repel each other. Only if they have enough energy can they overcome this potential barrier and fuse. But if you do the math, the nuclei in the sun don’t have enough energy. The sun’s just not hot enough, non the less, the sun shines, and it does so because of tunneling. Just like our physical barrier, there’s a chance that our particle could be on the other side, and so the sun shines.
[roll credits]
What do you think?
This piece was designed to get you thinking. So find a physicist and get talking, or post a comment and get a discussion going. The main point is that quantum mechanics is real because it properly describes nature. Einstein may have believed that God doesn’t play dice, but God need not conform to Einstein’s beliefs.
Entry Filed under: Quantum Mechanics
21 Comments Add your own
1. adam | March 3rd, 2008 at 11:41 am
I loved this piece. You really have a gift for explaining this topic. I have a test tomorrow and this video really solidified the topic of tunneling and the uncertainty principle.
2. kevin | April 8th, 2008 at 6:05 am
Great video. I found it very helpful. Thanks!
3. Karen Niedzwiecki | April 19th, 2008 at 9:36 am
Please, please do one of these about non-locality and phase entanglement. Please
4. dominique colonna | April 23rd, 2008 at 2:08 am
thank you so much for such a great video.
5. Great Video | May 8th, 2008 at 4:10 pm
Great video and the transcript was very helpful for non english fluent people.
Thanks and congratulations on an awesome work.
6. TERRY FRASER | May 9th, 2008 at 2:42 pm
Hi, nice video. I am confused about what is quantum mechanics to classical mechanics, by not saying tunneling is the only factor for justifying quantum mechanics? There seems to me there is a fine line between both systems.
7. admin | May 9th, 2008 at 2:50 pm
Terry, Quantum mechanics considers the consequences that result when energy is taken to come in discreet packets (quanta). Classical mechanics, however, does not. That may sound like a small difference, but the consequences are profound and paint a picture of a world where we must speak only in probabilities. This is not to say it removes the predictive power of science only that it places a limit on how well we can know certain things, hence the uncertainty principle.
8. Mike | June 22nd, 2008 at 3:59 pm
I found the whole piece to be boring, misleading and frustrating.
1. Consider getting a script writer and narrator who’s proffesional at delivering words.
2. More importantly, do what you say you are going to do. The title of the piece is “what is quantuum tunneling”. Not “some reasons and proofs for the existence of quantuum tunneling” which is how it went. If I was new to all of this I would have walked away thinking, well I now know a little about quantuum tunneling, at least enough to consider that it might be real, and in reality I would know hardly nil about what the actual process is.
9. hamilcar intengan | November 2nd, 2008 at 2:15 am
is the planck constant figure used in some of these equations an integral part of observed nature or a conveniently derived number to allow for these equations to work?
10. hamilcar intengan | November 2nd, 2008 at 2:17 am
is it possible that one day vastly more sensitive tools can be discovered that will resolve the past and future locations of these quantum particles and subsequently negate the probability theory then?
11. michael sobowale | December 22nd, 2008 at 3:40 pm
can a magnetic fluid or a metallic fluid when applied with electricity, generate a magnetic wave or a magnetic field?
12. michael sobowale | December 22nd, 2008 at 3:42 pm
can a magnetic fluid generate a magnetic field or wave when electricity is applied?
13. Tyler | January 9th, 2009 at 7:16 am
Thanks, very informative, the text allowed me to cite you too ^_^ great job!
14. Tony | January 19th, 2009 at 3:20 am
There are things in the universe that science does not yet know, but with the permission of The Lord, they will discover. God will permit scientists to discover the impenetrable barrier of the universe. The day will come when human. wisdom will be lost. …
———-
Warning:
The big Comet will come and cause great destruction.
The earth is in danger because the creature wants to be greater than The Creator
Humanity will carry a heavy cross. The earth will incline when the great object comes nearer. Time will be lost.
Please read the messages from Virgin Mary at
http://www.apelosurgentes.com.br/english
15. PETER SMITT | September 2nd, 2009 at 5:39 pm
They say gravity is weak because some of the force leaks into another dimension. Well, why can’t the other forces (like electromagnetism) also leak?
16. tesfahun | December 24th, 2009 at 1:06 pm
i want to the best defintion of tunneling with mathmatical proofs
17. Alakazam of pizza express | February 1st, 2010 at 10:18 pm
If I had a quantum super tasty pizza, could this mean than if i ate only one gorgeous slice i would still feel full or if i eat the whole thing then it could potentially still all be there to eat again tomorrow depending on the way i think about eating it?
If observation influences the way subatomic particles behave does the processes of observation allow us to control them?
For the more knowledgable people out there please excuse my ignorance, I know very little about this subject but I’m still very interested in ordering a pizza and getting it delivered at the speed of light
18. Alakazam of pizza express | February 1st, 2010 at 10:23 pm
Wow that was quick……….pepperoni with extra cheese my favourite.
19. Brian | March 26th, 2010 at 9:21 pm
I think this was very well done. I don’t like how people say it wasn’t detailed enough or whatever, because the truth is: we don’t really know much beyond what was presented in this video. It’s a fasciniating topic, but we cannot accurately predict the momentum of quantum molecules. As a result, we have idiots posting things that are probably better left unsaid. I don’t think anyone here is qualified to give one judgement or another, so lets just enjoy the video…
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