Hi there, physics fans.
How are you doing?
If you’ve watched this series since the beginning, you’ll no doubt remember that
I promised in episode one to cover all of the important topics of particle physics and
cosmology and I’ve done that.
Each episode discussed an individual subject, but now I think it’s time to try to bring
it all together.
The ultimate goal of physics is to connect all scientific knowledge into a single theory
– a theory of everything.
That sounds like a great topic for this week’s episode of Subatomic Stories.
Since time immemorial, curious people have tried to understand the ultimate nature of
matter, hoping to understand if there was a primordial building block of which familiar
matter was composed.
The ancient Greek philosopher Democritus had some primitive thoughts about atoms, but they
were nothing more than thoughts for thousands of years.
It was the early alchemists and then more modern chemists who learned about chemical
compounds and elements and eventually worked our modern understanding of atoms.
In the past century, researchers went on to learn of protons, neutrons, and electrons,
and the last 50 years has brought us the idea that matter was made of quarks and leptons
and that twelve particles – six quarks and six leptons – make up every object that
anyone has ever seen.
Actually, for ordinary matter, it’s really just two quarks and two leptons.
I talked a bunch about this in episodes 2, 3 and 4.
Realizing that all of matter can be made of four or twelve building blocks is quite an
achievement, but it still makes us wonder.
If molecules are made of atoms, and atoms are made of protons, neutrons, and electrons,
and those are made of quarks and leptons, is it possible that quarks and leptons are
built of even smaller things?
Have we found the smallest building block of nature?
Probably not, but hold that thought.
Because we also have to think about forces.
Over the past 500 years, scientists have looked at the world around us, working out the rules
governing how matter is constructed and noticing how these rules are connected.
Phenomena that seem to be very different have turned out to be the same thing when you look
at them in the right way.
For instance, it was in the 1680s that Isaac Newton realized that the force that caused
an apple to fall was the same one that made the phases of the moon change every month.
Those two things seem to be completely unrelated, yet we now know that gravity is the cause
of both.
Two centuries later, another British scientist by the name of James Clerk Maxwell realized
that a flash of lightning and the magnets that attach a child’s art to the refrigerator
were both explained by the laws of electromagnetism.
That scientific success was made even more…well…successful, when subsequent researchers connected electromagnetism
also to the theory of light and chemistry.
And in the 1960s, a bunch of physicists realized that the weak nuclear force and electromagnetism
are the two ways to look at the same thing.
That realization led to Peter Higgs and Francois Englert receiving the 2013 Nobel Prize in
physics.
I talked about this in episode 8.
Newton’s and Maxwell’s and Higgs’ realizations were examples of what physicists call a unification
of forces.
This means that forces and phenomena that seem different are actually part of a more
basic and simpler force.
We now know of three forces that seem to be unrelated, gravity, the strong nuclear force,
and the combined electroweak force.
Current scientists imagine that perhaps that it is possible that these three forces might
be different facets of a deeper and more fundamental force.
Maybe, just maybe, a single force is at the bottom of it all.
Maybe there is even a single building block that is found inside the quarks and leptons,
or maybe there are many more layers of matter below the familiar particles of the Standard
Model.
We don’t actually know if any of that is true, but if there is a single force and a
single building block, the theory that describes them is called a Theory of Everything, or
TOE.
Scientists have even tried to imagine what a TOE might look like.
The most successful…and it’s not all that successful by the way…but most successful
is called superstring theory, which says that everything is made of little super small vibrating
strings, with each vibration pattern being a different particle.
So, you might ask yourself if a TOE is a reasonable idea.
Well, in my opinion, it is.
I don’t know if it’s right, but it’s reasonable.
Now a second question you might ask is just how close we are to figuring it out?
And there, I think it is very unlikely that any currently living person will live to see
it.
Why is that?
Well, it boils down to the fact that our current theoretical thinking says that the energy
at which the final unification would occur is the Planck energy, which is about a quadrillion
times higher than the energies we can study using the highest energy particle accelerator
ever built.
And a quadrillion is a lot.
If we represented the energy we can currently study as being as long as half a football
field, the Planck energy is all the way to Alpha Centauri, the nearest star.
Imagine you knew everything there was to know in a distance within fifty meters of where
you’re standing right now.
Now think about all of the things that are outside that range – say volcanoes, and
glaciers, and koala bears.
Then there are giant rivers and oceans and plantations where they grow cinnamon.
It’s unlikely that your knowledge of the area around you would lead you to predict
any of those things.
Then there are such things as the sun, the moon, and the planets.
There is all of outer space.
In short, projecting from the area around you to everything between here and Alpha Centauri
is quite a feat.
If you tried, you’d have missed a thing or two.
That’s likely to be true as we try to generalize from what we now know to a theory of everything.
And remember that even in this series of videos, I told you about things that we know about,
but don’t know the answer, like the dark matter of episodes 21 and 22, the dark energy
of episode 23, and whether inflation is real, as I mentioned in episode 27.
We have to understand all of those things too, and figure out how they fit in.
Until we do that, a theory of everything is just a pipe dream.
I could talk a lot more about this, but I made an hour-long video that talks about precisely
this subject.
The link is in the description.
And, if you’re really interested in understanding all of this better, at the end of the long
video, there’s a link to hours and hours of information.
The bottom line is, I think that, in spite of everything we’ve learned about in this
series, I think it’s safe to say that we’ve just taken the first baby steps in our journey
towards a theory of everything.
We’ve only begun to ask the tough questions.
And, speaking of questions, what questions do you guys have for me this week?
Questions are always fun.
Let’s jump right into them.
Android on Street asks about dark matter on Earth and in the Solar System and why we don’t
see any effect.
Hi Android.
This one is easy to answer.
The amount of dark matter in the vicinity of the solar system is about six times ten
to the minus twenty eight kilograms per cubic centimeter.
That’s equivalent to about a single proton’s mass for a volume about equal in size to your
thumb.
Of course, we think that dark matter particles are heavier than a single proton, so that
means that there would be about one dark matter particle in a volume the size of your fist,
give or take.
Now compare this to the amount of ordinary matter in your thumb.
That’s about ten to the 24 protons, give or take, thereabouts, kinda-sorta.
So you see that the amount of dark matter we see is just tiny.
And if we add up the amount of dark matter in a sphere the size of the Earth’s orbit,
it works out to be about ten trillion kilograms.
That sounds a lot, but the mass of the Earth is about six trillion trillion kilograms,
or a trillion times bigger.
The mass of the Sun is bigger still – about a hundred quadrillion times the amount of
dark matter in that sphere the size of the Earth’s orbit.
The bottom line is that dark matter is thought to be here on Earth, but it’s negligible.
Professor Beautiful was hoping I would say something about Roger Penrose’s conformal
cyclic cosmology.
Hi Beautiful.
Yeah, I gotta say that I’m not a fan.
In his CCC theory, a universe has a big bang, then the usual expansion, life, and death
of the universe, followed by another cycle, over and over again.
Basically the “conformal” title in his theory is about a mapping of the early uniform
universe onto the uniform late universe.
Then the uniformity of the end of one universe reflects the uniformity of the follow on universe.
Or something like that.
Now there has been a lot written about his ideas, especially since he just won a Nobel
for some earlier work.
But he has made predictions of structures in the cosmic microwave background radiation
that haven’t been observed, so that’s a big strike against his idea.
I mean, he may be a hotshot theorist, but physics is an experimental field and if a
prediction disagrees with a measurement, the theory is wrong.
The bottom line is that I think it’s premature to call the theory dead, but I think it’s
even more premature to think that it’s been validated.
And I think it would be foolish to bet a lot of money on it turning out to be right.
Just my opinion.
Teotite asks if low-lifetime particles can have long lifetimes if they are in extreme
environments.
Hi Teotite.
Well, yeah, they can in principle.
For instance, an isolated neutron is unstable with a half life of about ten minutes.
But, if you put it in an atomic nucleus, it can be stable forever.
The energy binding neutrons to protons suppresses the decay.
And the basic concept can be extended to other particles, although we’ve never seen it
happen.
There is proposed idea of a thing called strangelets, which are particles with strange quarks in
them.
Strange quarks are unstable and decay rather quickly.
However, according to the theory, under the right conditions, not only are strangelets
stable, they are actually more stable than ordinary matter.
If that were the case, strangelets would be like zombies or viruses that affect ordinary
matter and convert it into strangelet matter.
Mind you, there is no evidence that strangelets are real – and we’ve made particles containing
strange quarks, which means we have some experience with them.
But the fact that respected theorists have written papers about them means that the idea
is at least plausible according to current theories and known measurements.
James Monteroso asks why we love Fermilab?
Hi James – that’s easy.
It’s because we’re smart and have good taste.
The tougher question is who >wouldn’t like Fermilab.
Yeah, I can’t answer that question.
Some questions are just too hard for me…
Durin Bane asks weren’t Newton and Einstein both amateur physicists?
Hi Durin.
No.
That’s a common misconception that I wish we could somehow kill.
When Newton left London to escape the plague of 1665, he already had a bachelor’s degree.
And Einstein received his doctorate in 1905, before he did his work on relativity and his
Nobel prize winning work on the photoelectric effect.
Both of them were most emphatically not amateurs.
Several readers asked a very common question, which is if all of the matter of the visible
universe was crunched into a singularity, why didn’t it turn into a black hole or
maybe just stay a black hole?
Hi guys – this is a great and sensible question.
However, the question is based on an incomplete understanding of relativity.
It was in 1916 that Karl Schwarzschild worked out that any concentration of matter would
eventually collapse into a small volume that would form a black hole.
That observation is at the center of these viewers' question.
But it is important to note that the Schwarzschild solution is a static one, one in which the
structure of space doesn’t expand or contract.
However, there are other solutions where space is more dynamic.
For instance, there is de Sitter space, or the solution of Alexsander Friedmann and George
LeMaitre, in which the universe can expand and contract.
And, in such solutions, the creation of a black hole isn’t inevitable.
The bottom line is that in universes in which space is expanding, it is not necessary that
the universe will form a black hole.
Now, we don’t know why the universe began expanding.
It might be inflation, or it might be something that happened earlier in the universe, before
Einstein’s theory of general relativity applied.
We don’t understand this period of the universe at all.
But it’s that expansion that saved the universe from death by black hole.
I put a link in the description of an article by Ethan Siegel that goes into this in a little
more detail.
Good question.
Okay, with that weighty question, and this episode on a theory of everything behind us,
I think that in the next few episodes, we will turn our attention to some speculative
ideas that aren’t accepted by the scientific community.
Sounds like fun.
If you’re enjoying the series, please like, subscribe and share.
And I hope you’re looking forward to these new physics topics.
I certainly am because, even at home, physics is everything.