One of the big questions within astrophysics is the question of anti-matter, that mysterious
substance used so often in science fiction stories, powering the warp drives of Star
Trek.
The idea of antimatter was first proposed by Paul Dirac in 1928, but no one had ever
seen it.
It was a prediction rather than a discovery.
And it just seemed to some like flipping mathematical signs on numbers, but then it was subsequently
experimentally proven.
Dirac should be a household name up there with Einstein, but due to a rather shy nature
and an avoidance of attention he’s mostly just remembered in science.
The idea of antimatter is really simple, elegantly so, the particles that make up atoms have
a charge.
If you flip that charge, you get an antiparticle with the same properties.
One is plus, the other minus, but that’s the only difference.
But what you can’t do is get two particles of opposite values together, or they annihilate
in a one hundred percent conversion of matter to energy, the highest expression of Einstein’s
famous E=MC squared, the most famous and recognized equation in physics, and it does it far more
powerfully than that equation’s applications in nuclear energy and bombs to the tune of
143 times more than anything we can do in nuclear reactions.
And, we can make antimatter.
It would be one of the most useful substances on earth, but only if it was easy to make,
we’d never again face any energy production problems.
Fusion would pale in comparison and go obsolete, and we’d never need a dyson swarm and aliens
with that knowledge of the universe wouldn’t either.
Maybe that’s why we never see them, their energy production is discreet in the form
of antimatter reactors.
But antimatter is one of, if not the most, expensive materials to synthesize on earth,
depending on the particle.
But we can do it, there are tricks, and we can flip charges and watch the interaction
on a small scale.
This is particularly evident with anti-electrons, better known as positrons, that can annihilate
on contact with normal matter so energetically that we can detect it easily.
Indeed, we make use of this already in medicine, yes, we have antimatter technology that already
saves lives.
The P in PET scan stands for positron.
PET stands for Positron Emission Tomography, where you inject a radioactive substance into
someone, it decays in the body and produces positrons, they annihilate and produce gamma
rays and from that you can make a map that shows cancer, blood flow problems, coronary
artery disease etc.
And it happens in nature at large scales as well.
Positrons are a part of our universe right now.
And there are mysteries regarding them.
Near the heart of the Milky Way Galaxy there exists a mysterious positron antimatter fountain.
And we don’t know why.
This is strange, but before we get into it, it’s worth noting here that given that anti-matter
behaves identically to normal matter, there actually isn’t a basic way to tell the difference
between a regular star and an anti-star if it’s not interacting with anything and producing
gamma rays.
It’s been suggested that some of the galaxies we see could, in principle, actually be anti-galaxies
that simply have no normal matter within them to annihilate with.
The reason this was advanced is that the big bang should have produced just as much anti-matter
as it did matter.
And all of it should have been annihilated and no matter should exist.
There’s simply no reason for the process to to have had a preference that we can see,
but it apparently did, so the modern consensus is that there was an unexplained asymmetry
of some sort and that there was just slightly more matter produced as opposed to anti-matter,
and the result after the great annihilation was the small amount of leftover matter that
we have today, and indeed are made out of.
Carl Sagan once famously said we are made of star stuff, the product of nuclear reactions
in stars and supernovae, but the story of what makes us up, the particles themselves
goes back to the very beginning.
We are big bang stuff, and those protons in your body, 10 to the 28th power of them, started
being created just 3 minutes after the big bang in the nucleosynthesis period.
This generation of what would become matter would not have happened without an asymmetry
of matter and antimatter production.
But where that gets more complicated is that nature still produces antimatter.
Near the center of the milky way, the antimatter fountain spews out enormous amounts of positrons
which then go out to annihilate in the interstellar medium to the tune of stretching 3500 light
years.
And there have been several more such fountains detected since because the matter and antimatter
annihilation emits a very distinctive gamma ray signature at the energy of 511,000 electron
volts.
This is one of the reasons why scientists think that anti-matter is fairly rare, though
existent in the universe, because that signature isn’t much more prevalent especially if
anti-galaxies exist.
But there’s no current way to tell for sure.
One oddity about anti-matter fountains is that they are really productive.
They aren’t just pouring out positrons, but on an unbelievably massive scale.
Beyond trillions per second.
And here’s the kicker, we have no idea what causes antimatter fountains.
You can look for sources for them, and you see nothing.
So the first place to wonder is if situations can happen with black hole accretion disks
or colliding neutron stars but nothing quite fits.
It’s one of those things scientists just don’t have a good answer for.
Even an alien technosignature wouldn’t really fit well because the positrons would be a
byproduct of whatever they’re doing, so why wouldn’t you use all the free energy
from them?
Whatever they might be doing, also seems profoundly wasteful.
But there are always things we don’t know.
For example, we have no idea what dark matter is, thus we don’t know what it can do other
than interact gravitationally with normal matter.
Perhaps there is some mechanism in the situational position dark matter might sit in that can
create an antimatter fountain.
But the other interpretation of antimatter, being that it might exist, and whole galaxies
might be made of it, is interesting at least.
It opens up the possibility of not only anti-planets, but anti-life where life could arise on such
a world that we could never interact with without total annihilation.
Don’t shake hands, and god forbid, don’t hug an antimatter alien or boom.
But all of this does offer a far future energy supply, harvesting massive amounts of positrons
in deep space for energy production is on the table.
Or weapons, a directed positron fountain weapon would certainly have an effect to the point
that you probably wouldn’t want to be on a planet in the beam of a nearby positron
fountain.
And with no known source, what happens if they just turn on, and the gamma rays created
from them are extinction events?
But antimatter still has another unsolved mystery.
It’s actually never been experimentally shown what its interaction with gravity is.
It’s overwhelmingly likely based on what we know that it should be expected to have
the same interaction as normal matter.
It should be attracted at the same rate, it would fall, and when it encounters normal
matter it goes boom.
We could call it an anti feather, you drop one, it falls just like normal matter until
it hits the atmosphere and annihilates.
But we don’t actually know that from experimentation and there are some hypotheses, very old ones
in fact, that it might be anti-gravity in which case might be subject to a repulsive
force.
This is unlikely, but hasn’t yet been ruled out.
But there is another form of matter that’s in a completely different boat and would very
likely be antigravity and may be able to exist.
It’s negative mass, and it would be among the most important game changing materials
we could ever come across.
In a 1957 paper by Hermann Bondi, links to all papers in the description below, he details
that something with negative mass should be antigravity.
This is different from negative charge, think of it as flipping a positive to a negative
in a number.
So mass, and antimass.
As we know from antimatter the universe lets you do this sometimes, so it’s more than
just a mathematical exercise of exchanging opposite symbols in front of numbers.
But here’s the odd thing.
If you have two objects of positive and negative mass, and they were equal, the negative mass
would repel the other, but the positive mass would attract the other.
This results in the two masses accelerating but remaining together yet separate.
Give it enough time and they will accelerate to the speed of light, relatively quickly
so long as the acceleration is constant, assuming we can factor in all the things that might
disrupt that.
That’s strange.
If you did that with equal sized planets, you’d accelerate them to light speed or
near it, causing extremely severe time dilation, meaning you could cross most if not all of
the observable universe in a lifetime in the frame of reference standing and living on
one of those worlds.
The rest of the universe would pass by fast forward in time however, and if you could
ever stop you’d find that massive amounts of time had passed.
But what would it matter to you?
Well, in our position, not really.
If we were able to build a negative-earth and get this planetary star drive going, you’d
just live your life on earth as you normally would have.
Your perception of the passage of time would remain the same in our frame of reference.
If you could get rid of negative earth and somehow slow down without destroying the planet,
you’d find yourself across the universe and in the far future in a lifetime.
If, as it were, we were early in the game of life in the universe, and rare, we might
not be so rare coming out of relativistic speed.
We may pop out to find a galaxy teeming with intelligent life, all discovering the same
technology and sending themselves careening across the universe.
Don’t go too far however, the expansion of the universe and the passage of time eventually
doesn’t let you do this if you want to get anywhere meaningful.
But there’s more.
Moving to 1990 and science fiction author and physicist Robert Forward.
His ideas, and subsequent ones have been floated as an alternative to dark matter and dark
energy.
The overall structure of the universe as we see it often includes voids where few galaxies
seem to inhabit.
Forward’s idea was that the repulsive force of negative matter might be causing this by
pushing normal matter around.
The problem is, you should still see evidence of the negative matter, it’s unlikely to
not have more interaction than just anti-gravity should it exist, and we simply don’t see
anything.
But the strangeness doesn’t end there.
Negative mass as we’ve envisioned it is something that physics doesn’t prohibit,
but that doesn’t mean it exists or can exist.
That’s not the whole story now, indeed the universe may be hinting at some form of negative
mass.
In 2017 a team at Washington State University did an experiment with atoms of rubidium where
they reduced the temperature of those atoms to near absolute zero.
This is not zero degrees in how we think of it, but rather the coldest possible temperature
at about -273 Celsius or -459 Fahrenheit.
Strange things happen when you do this.
What you get is known as a Bose-Einstein condensate.
These conditions cause a large amount of particles to occupy the lowest quantum state to the
point that quantum effects that would normally only be seen below the level of the atom suddenly
become apparent at the atomic level.
Using lasers, what happened with the Rubidium atoms was that they began to show traits of
having achieved some sort of negative effective mass when they accelerated towards a pushing
force, instead of being repelled by it.
Other oddities in this grain is that under certain conditions, electrons can do something
like this, and there’s even a hypothesis of some unknown semiconductor composites that
might exhibit signs of negative mass in some form.
If that’s the case, then it may ultimately hint that the universe does indeed allow for
negative mass and even create it in nature.
This changes everything we know however about the universe and creates some huge headaches
along with it for the physicists.
The reason is that if you could have negative mass a bunch of highly speculative technologies
come onto the table.
Think backwards time travel, Alcubierre warp drives and stable wormholes.
And that’s a problem.
If time travel and wormholes were truly possible, and we see hints of materials that could make
them possible, then we have to ask.
Where are the aliens and time travelers and various mixes of both?
One explanation is that our understanding of physics is incomplete, thus we don’t
yet know about any other potential brick walls that may prevent those things.
Or it could be so unbelievably difficult and resource intensive no one ever does it across
the entire timeline of the far future universe.
But there is another option, and it’s spooky.
It could simply be that there is, and never will be, anyone else out there.
And in the future, perhaps the not too distant one, we are no longer here.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently contemplating the
end of my youtube career centuries from now.
Think of the headline in the daily intergalactic times.
JMG finally found alien life, and then promptly hugged the antimatter alien, and then he was
no more but the larger mass regenerative alien soon recovered.
Not good for me, though I'm glad the alien is okay and be sure to check out my books
at your favorite online book retailer and subscribe to my channels for regular, in-depth
explorations into the interesting, weird and unknown aspects of this amazing universe in
which we live.