This weekâs video is on Dark Matter, a strange,
fascinating and mysterious substance, though in some ways I think it is considered fascinating
because we call it Dark. Dark Matter, Dark Energy, and Dark Flow, each
topics Iâd like to cover in the future, have no special relationship with each other. We call them Dark because we canât see them. It is a bit like how every new jet plane or
weapon gets called X something-or-other, the X means itâs a prototype and that gets dropped
later on. Dark Matter, Dark Energy, and Dark Flow have
as much relation to each other as a prototype assault rifle, fighter jet, and naval cruiser. What Dark Matter and Energy both have in common
is that they are thought to make up a huge chunk of the Universe. What they also have in common is that they
have both captured the attention of the public, which is mostly good, but also means that
an awful lot of scientifically dubious stuff that has popped up around them. I will talk about some of the weirder things
we might be able to use the stuff for near the end, it does have potential uses, but
itâs also collected a lot of rubbish over the years as people tapped it for its mystery
value. And again the stuff is quite the mystery,
but at the same time it also isnât. Weâve suspected this stuff existed for almost
a century now back to when we first realized we lived in a galaxy. Back in the days of yore, when particle physics
had just established that atoms included protons and electrons and not much else, we thought
the universe was probably an object of infinite size and age, the Steady State Model, on the
grounds that if it wasnât infinite in size then if it was infinite in age everything
should have smashed together into one big ball under the influence of gravity. And of course the Universe had to be infinitely
old because if it was not you would have to wonder about what was around before it and
where it came from. But we were getting good enough with our telescopes
to be able to measure the relative speed of a lot of stars and it established that they
were by and large moving in an orbit of what we eventually realized was the galaxy. This is where the problem started with the
missing mass. We were getting pretty good at doing orbital
calculations at this point and realized that based on the number of stars we could see
and their mass, everything should be rotating around the galaxy at a certain speed depending
on how far from the center it was. Much like how the planets rotate around the
sun, only a good deal more complicated since while the sun is one big enormous mass surrounded
by a handful of smaller planets who perturb each otherâs orbits just a little bit, the
distribution of the galaxy makes the influence of them on each other a much bigger factor
in things. We wonât go through that math, but there
was agreement there was a lot of matter we couldnât see, an awful lot too, way more
than planets around stars would justify. This wasnât too big a deal though, we just
assumed it was a lot of gas and rock and such and the orbital models were hardly precise
things at the time. Now we had realized galaxies existed quite
some time before that, a generation before the United States came into existence Immanuel
Kant had nicknamed them Island Universes and it had been speculated a lot of them were
flattened disks, like our own is. But we had no idea how far away they were
until about the End of World War One when comparisons of the brightness of novae in
them to ones here was noticed to be a lot dimmer, and dimmer to a degree that would
indicate they were millions of light years away. This caused what was called the Great Debate,
about the size and scale of the Universe. They still werenât getting called galaxies
at that time, spiral nebulae was the normal term, and Iâve never been able to find out
when that fell out of use and galaxies came in. You will see in a lot of very old scifi stories
or articles references to visiting the Andromeda Nebula for instance. Now in 1933 Fritz Zwicky, the fellow who coined
the term supernova, was at Caltech studying clusters of the nebulae or galaxies when he
noticed that they had to have way more mass than we could see to be behaving as they did. He estimated the one he was looking at must
have some 400 times more mass than he could see, and he called this matter dark matter,
though being Swiss he used his native tongue. Now let me give you a quick example of how
you could estimate a Galaxies mass, simplified to avoid all the heavy math you need to do
this when youâre looking at effective snapshots of billion year processes. Our neighbor, the Andromeda Galaxy, is actually
moving toward us. Thatâs not the norm, virtually every galaxy
is moving away from us, red shifting, as you know, and thatâs what killed the Steady
State model in favor of the Big Bang. We know what frequencies of light certain
types of stars and phenomena give off, so we can look at distant things and say thatâs
the spectrum they should be emitting, but everything on it is moved a bit over. Itâs red-shifted, meaning itâs traveling
away from us quite quickly. Blue-shifting, where the spectrum of a star
moves the other way, indicates the opposite. So if I had millions of years to watch the
Andromeda galaxy approaching us I could say it was going at such and such a speed when
I started looking and is now going faster, being sped up by gravity. If I calculated how much faster Iâd know
how much force the gravity had exerted and be able to say how massive our galaxy was. Same as I could estimate the gravity and mass
of Earth by dropping a rock and seeing how fast it got as it fell. In a nutshell if you do this for our two galaxies
youâd find out they both massed a lot more than the stars in them would suggest they
did. Now thatâs not a problem, we already know
a lot more hydrogen and gas is floating around than the stars contain. Add to that, the year before Jan Oort, for
whom the Oort Cloud was named, had tweaked to a similar idea, that the mass of our own
galactic plane was much larger than we thought. Problem was, his calculations were erroneous
and Zwicky himself was off by an order of magnitude. For a long while, because our data and modeling
just wasnât sufficient to really nail it down probably, the idea kind of hung out in
limbo. Everyone agreed there was a lot more matter
than what star contained but this was somewhat shrug worthy. Seeing gas clouds of hydrogen is a bit tricky
but conceptually straight forward. Everything tends to absorb or reflect light,
and any given atom or molecule has certain characteristics of which frequencies it does
this for. So if Iâm looking at a star I know thereâs
some gas and dust between me and it, and if I look at one twice as far away Iâd expect,
on average, thereâs be about twice as much. Start looking at thousands of them and you
can start calculating pretty exactly how much gas and dust is between you and each of them
and get a good idea how much junk is lying around in between and even its distribution. Weâve gotten way, way better at this as
the years rolled by, and way better at measuring the mass of galaxies, and it started getting
very obvious that there just wasnât enough mass out there, in terms of stars and gas
and dust, to equal the gravitational force we saw. The discrepancy was just way too big and way
too concrete to ignore anymore. This gives us our first two properties of
dark matter, because we know it has to have mass, or at least exert gravity, generally
considered the same thing, and we know it has to be transparent to light. Because it isnât sucking up visual light
or any of those other frequencies like radio we look at. Or at least, if it does interact with light,
itâs got to do it very minimally, either by being compacted into huge dense chunks
or just interacting so little we donât notice, being very weakly interacting. Thatâs how things stood in 1980, when I
was born and Vera Rubin submitted her results on the galactic rotation problem showing rather
firmly that most galaxies were carrying about 6 times more mass than we could account for
from stars and gas and dust to be spinning at the rates they were. This wasnât a groundbreaking and surprising
paper exactly, it had been suspected for a while, but she had compiled such a compelling
hard argument and collection of data that it wasnât so much a nail in the coffin as
a stake through the heart of the idea that it might just be a mundane source of mass
we were estimating badly. This was hard, sheâd used the best modern
equipment of the time to measure this stuff and spent years compiling it, and every model
agreed that for stars to orbit their galaxies like they were doing there needed to be a
lot more mass than we could otherwise detect, either because it was emitting light or blocking
it. Now a lot of options were put forth, we had
discovered neutrinos for instance, theyâd been theorized since the 1930âs and first
detected in 1946, and had some of those expected properties. Neutrinos donât interact with virtually
anything, thatâs why they can glide untouched through entire planets. The problem with using them for dark matter
is two fold. First neutrinos come about essentially as
the byproduct of nuclear reactions. When you get a nuclear decay or a fusion or
fission reaction some of that excess energy flies off as a neutrino. Several trillion of them pass through you
from the sun every second as a result of the fusion of hydrogen into helium. Thatâs the problem though, only a small
fraction of the mass of a star is converted into neutrinos, and hydrogen is hands down
the most abundant material in the Universe, meaning most mass hasnât gone and been fused
and produced neutrinos yet. So neutrinos canât make up the majority
of the mass and energy of the Universe because they simply havenât been produced in large
enough amounts yet. And since they fly off virtually unimpeded
you can expect those from far and ancient corners of the Universe to arrive intact to
our detectors. So thereâs no reason to think they got produced
in huge quantities at some point early in the Universe and we canât see them now. Thatâs the other problem. Neutrinos have very little mass compared to
their total energy, they move within spitting distance of the speed of light. And virtually nothing stops them. So they ought not to be hanging around galaxies. They ought to be fairly evenly distributed
throughout the Universe, more even then photons since light does get absorbed by a lot of
things. Thatâs our third property of dark matter. It canât be moving too quickly or it wouldnât
be clumped up around galaxies. Itâs not evenly distributed throughout the
Universe, it clumps around galaxies a lot. That means it canât be moving too fast on
average. The escape velocity of galaxies is higher
than Earthâs or the solar system but itâs nowhere near the speed of light. So we can assume this missing mass isnât
moving near the speed of light like neutrinos do, or even at decently relativistic speeds,
or it would be spread out a lot more evenly, whereas the models that show it exists by
making galaxies spin at the wrong speed indicate its spread out in a spherical halo around
the galaxy. Since it clearly doesnât interact with light
or normal mass there are no collisions making particles of dark matter slow down and tend
toward a disc-around-a-sphere distribution like many galaxies and solar systems exhibit. Gravity would slow them down as they try to
pass us and speed them up as they neared, so youâd get nice orbits for those moving
slow enough to stay captured, but they will not generally clump into balls like normal
matter does to form planets and stars because theyâre not colliding with anything to average
out their momentum. So that is 3 properties so far, they interact
with gravity, because they exert it on things and we can see it clumping around galaxies. They donât interact with light or normal
matter, or at least do so even less than neutrinos do. And they do not have much speed. We might as well add a fourth too, that they
demonstrably make up the majority of the mass in the Universe. So that is the state of play for the last
couple generations, we have a learned a bit more but mostly why various alternative explanations
donât work. Here are some of the more common ones and
their strengths and flaws: Wimps â Short for Weakly Interacting Massive
Particle, this is the current favored candidate for dark matter. You could think of this like a neutrino, though
in the way a glacier creeping across the landscape is like a snowball. Which is to say they are both made of ice
and moving, but the one is much faster and smaller. If a Neutrino is a weakly interacting low
mass particle, a WIMP is any even less interacting heavy mass particle. Neutrino mass is about a millionth of an electronâs
mass and billionth of a proton or neutronâs mass. WIMPS are thought to be as massive as a proton
to maybe a thousand times more massive, currently. Nor would they have to be a single type of
particle, there could be a whole particle zoo of these which would make sense since
theyâre the majority of matter. After all there are 6 flavors of quarks and
6 types of leptons of which the electron is one and the neutrino is too, well actually
three. Of the four fundamental forces, gravity, electromagnetism,
and the weak and strong nuclear force, leptons can interact with all but the strong force,
whereas quarks interact with all four. But the gauge bosons, the particles that transmit
those forces, usually are said to only interact with the force type they transmit and gravity,
though gravity is always kinda tricky to talk about at the subatomic scale. Very loosely though weâd say each particle
has traits that let it interact with a given type of force and some particles are just
missing those. I sometimes think of it like a module or receiver
that lets it pickup that forces signal, as it were, and apparently most of the matter
in the universe didnât come with that installed for anything other than gravity. Gravity is a weird force, it is way weaker
than the other three and has defied a lot of out attempts to unite the forces in Grand
Unified Theories. Itâs fairly popular nowadays to say itâs
not entirely real or maybe not a force, but I reject that. Not because I disagree with the general reasoning
but simply because gravity is the first of the four physical forces we encountered and
studied, so if we stop calling it a force to me that would like having a definition
of automobile that excluded the old Model-T. Keeping it simple though, WIMPs would be particle
that just donât have the device installed to listen to those other three forces, or
have only a very cheap system that barely hears them. Most other particles have the receivers installed
for one, two, or all three of those forces. I find this analogy makes it easier to understand
why apparently most of the particles in the Universe are lacking this trait. Now again the WIMP is the lead candidate,
so itâs got more in its favor then against it. Starting with quite a few models predicting
something like them ought to exist. The big thing against them is trying to detect
the wretched things. Weâve mostly managed to figure out what
they arenât. Like neutrinos, WIMPS ought to be flying around
and through us all the time, but it is kind of hard to detect something whose only known
property is it does not interact with anything for you to detect. I mean if you had a box full of the stuff
you could shine a flashlight right through it and see nothing, wave your hand through
it and feel nothing, and while you could detect it by feeling its mass when you picked up
the box, they would just slide right through the box, which couldnât have kept them inside
in the first place anyway. The big longstanding competitor to WIMPs was
MACHOs, Massive Compact Halo Objects, MACHOs and WIMPs are fairly inspired acronyms since
they are quite descriptive. Where the Wimp is a tiny particle that doesnât
interact with virtually anything, a MACHO is a huge macroscopic object that just doesnât
emit much light. This is everyoneâs favorite first suggestion
too. Brown Dwarf stars, big gas giants, neutron
stars that have cooled down, and black holes. Now Halo is important in there because it
means the objects are out in the halo of the galaxy. Remember we need a distribution of matter
that implies the missing mass enfolds the galaxy as a loose sphere. A MACHO definitely absorbs light, it just
doesnât particularly emit it. Theyâre very dense compared to dust clouds
so weâd expect they donât block much light. This has generally not been a popular solution
with the people studying the problem, but more the solution popular with folks not studying
it, since it basically represents folks saying âDo we actually need to make up some freakish
new material composing the supermajority of the Universe?â In a nutshell, especially these days as weâve
compiled more data and more accurate data, the answer is yes. Now there is a lot of reasons this doesnât
work, many of them highly technical, but let me offer a more intuitively simple one thatâs
a variation of the one I use with the Fermi Paradox I call the Time Elapse Argument, or
TEA, because I like acronyms too. If I see a weird looking galaxy a billion
light years away, and know that it looked like that a billion years ago, then spot a
similar one a similar distance away in a different direction and another in third direction I
can say that those are unrelated, if artificial in origin, and furthermore that in a volume
with a radius of a billion light years weâd expect 3 of them. So if I look out to a radius of 2 billion
light years, which would have 2-cubed or eight times the volume, I ought to expect about
8 times as many of them or about 24 of them. Going out to 3 times the distance Iâd expect
27 times as many or 81 of them, give or take. Going out to, say, five billion Iâd expect
to find about 400 of these things. But if they are artificial in origin, youâd
think theyâd be more common as the universe got older and more folks arose to build one. As time elapses you can argue they should
be more common, so the further away you look, and the further back in time you look, the
less common they should be. If you are seeing a phenomena which appears
evenly distributed throughout the universe in space, and therefore time, it is not too
likely to be artificial in origin. This works quite well for a lot phenomena
folks have jumped the gun on and attributed to aliens, which has often included dark matter. But it also includes a lot of MACHOs. Planets take time to form, there are more
of them now than they used to be⌠which is a good caveat to the time elapse argument
since we canât assume just because something is now more common that it is artificial,
just that if it is not more common nowadays it probably is not artificial. Planets take time to form, Neutrons stars
take time to form as a star must form, live, and die, then cool a lot to being invisible
to us. So we should expect that a long time ago in
a galaxy far, far away it ought to have a not formed so much of a Massive Compact Object
Halo. Weirdly what we instead see at huge distance
away and back in time are things like dwarf galaxies composed of mostly dark matter instead. But we certainly are detecting dark matter
around ancient galaxies absurdly far away in time and space. So that along with it not being neutrinos
tells us that Dark Matter is also old. It is old, it is cold, and it is massive. As best as we can tell it has stayed constant
in quantity this whole time too so it presumably does not have a half-life or get created by
interactions between normal matter. There are tons of other weaknesses for it
being MACHOS but I think that is the one that is easiest to understand without needing lots
more science and technology background on it. The next candidate is the Axion. This particle was first theorized to deal
with some problems in strong nuclear force interactions. It is very like the WIMP, except it isnât
heavy. Whereas WIMPS can be thought of as heavy version
of neutrinos, weighing as much or more as a proton whereas neutrinos weigh in at about
a billionth of that, the axion weighs even less than the neutrino, anywhere from about
the same mass to a millionth of neutrino mass. Now the axion is thought to be a particle
with very tiny mass and no electric charge, but is also thought to switch into photons
in magnetic fields. Axions are nice candidates since they are
hard to detect but not nearly as hard as WIMPs, both from their properties and that they ought
to be somewhere between a billion to a billion, billion times more common. But while it would make a huge difference
to cosmology if it were WIMPS or Axions making up dark matter they are pretty similar objects. Theories for Axions do place their creation
all the way back to the early time of the Universe too. In some ways I would say the Axion beats the
WIMP out as a candidate for dark matter in the sense that it will be a lot easier to
detect, so focusing on proving it or disproving either gets us the answer or gets it out of
the way. And we have a number of experiments just getting
under way or coming on line soon that ought to settle the matter. Weâre going to skip the Kaluza-Klein Particle,
an option for dark matter under string-theory. It has not been ruled out yet but it is supposed
to be easier to detect than most of the others, relatively speaking of course, and we havenât
got a whiff of it in the experiments we expected to get a whiff from. I will also skip the gravitino, a particle
predicted under Supersymettry, they were a great candidate but the blows to super-symmetry
in recent years demote them I think. Similarly MOND, Modified Newtonian Dynamics,
loosely the idea that gravity doesnât fall off as the inverse square at very long distances,
has fallen strongly out of favor so we will skip it too. That leaves our last big candidate, tiny primordial
black holes. Normal black holes just donât form enough
to account for all that mass, but a lot of our notions about the moments right after
the big bang gives us some cause to think lots of small black holes might have formed
then. Now if Stephen Hawking is right, that black
holes evaporate with time, with the smaller ones evaporating much faster, via the Hawking
Radiation we talked about in the video on micro-black holes and Hawking Radiation, then
we can put a minimum mass on those. Small black holes donât live long and are
very bright. And so not only would the smallest of them
be gone by now but they ought to have left a ton of radiation around all over the universe
making its way here. If heâs wrong then no problem at all. A small black hole with no Hawking Radiation
is a WIMP for all practical purposes, one would fly right through you without you even
noticing. But if they do evaporate, we can say they
have to mass at least a hundred megatons or they wouldnât be around anymore. One with a mass less than that wouldnât
have lived this long and would have been quite bright. We can push that up a bit too, because there
is dark matter in our own solar system, some models say now it might be denser than expected,
possible a whole large asteroids worth scattered about, and if thatâs the case we can put
an upper limit on how much radiation they could be spitting out without us noticing
them. Iâd say realistically we would see them
if they massed less than about 100 billion tons, because that at that point youâd expect
them to give off a bit less than a megawatt each of radiation and number about a million. If they massed less they would each be way
brighter and more numerous. Chop a black hole into ten small ones each
of equal mass and they would each be a hundred times brighter than the original and again
ten times more numerous. Iâd have difficulty imaging us missing things
brighter than a megawatt and more numerous than asteroids. 100 billion ton black holes would be about
as bright as small asteroids and about as numerous. Not that they would be giving off visible
light, it would be gamma, but Iâd have a hard time imagining us missing even the 100
billion tons ones in gamma. Smaller than that and Iâd say no way. Bigger than that is an option but not a lot
bigger or we would detect them messing with planetary orbits and picking up accretion
disks. Now whatâs interesting is that while there
is cosmic microwave background radiation, thereâs also infrared and xray background
radiation, and recently NASAâs Alexander Kashlinsky and others noticed that there was
a lot of matchup in those two, with the most obvious candidate for such a match being primordial
black holes. At the same time we have just recently gotten
our first detections of gravitational waves from the LIGO detector, our first sight of
black holes and not just things glowing while they fell into them, and it has been suggested
some of those detections were of the merger of primordial black holes. I will link an article in the video description
from a couple months ago from Shannon Hall at Space dot Com discussing this more, but
while primordial black holes have been a solid if minor contender for dark matter for a long
while, their stock seems to be on the rise the last couple years while quite a few of
the others have lost steam during that same time. So WIMPs remain the strong first place, and
Iâd say axions after that, but I would promote primordial black holes to third place and
we can pursue both them and axions aggressively in the next decade to either prove them or
disprove them. There are tons of other dark matter candidates,
from the plausible and credible if minor candidates to the downright zany, but those are the big
ones and I also mentioned discussing some uses of Dark Matter so if I donât get to
those now the video will get too long. The first and most obvious use is just as
filler material. If you can find some substance or field that
lets you interact with dark matter, then thereâs lots of uses for something that basically
is just mass with no interactions. Weâve discussed quite a few megatructures
on the channel that use most of their mass just for gravity, like shell and discworlds,
and we would usually assume you would use hydrogen and helium for this job, since they
are so abundant compared to other elements like carbon and iron. Dark matter would for instance be even better. You donât have to worry about undergoing
any weird transitions into things like metallic hydrogen or start up fusion if you stick too
much in one place. Dark stars, hypothetical stars composed mostly
of dark matter that might have been around when the Universe was young, are thought to
have been able to get a big as solar system. Since some hypothetical forms of dark matter
are their own anti-particle, youâd expect the rare collisions of two of them to produce
a matter-anti-matter reaction generating light. This light is why we call them stars, or dark
matter stars or dark stars. You probably wouldnât want to use dark matter
as a dense filler in such a case, though it would depend on how often those collisions
were happening, but that would make that an excellent power supply too. Obviously we have no concept for a material
or field that could contain dark matter but if we did have one, and if dark matter was
its own anti-particle, you could imagine sticking it in a big balloon or bladder you could squeeze
tighter to make more collisions occur or expand out to decrease those. Giving you essentially a massively plentiful
source of energy equal to antimatter but way safer, easy to throttle, and naturally abundant,
super abundant even. The Bussard ramjet we discussed way back in
the Interstellar Colonization video probably doesnât work, it seems to take more energy
to sweep up the hydrogen it runs across in space and fuse it into helium than it would
produce in thrust, BUT if you could do that with dark matter and it was its own anti-particle
youâve an amazingly mass efficient fuel supply evenly distributed throughout the galaxy
that practically has a sign on it saying perfect ârocket fuelâ. Ships able to gather that up as they plowed
by ought to have no problem going quite close to the speed of light and not needing to worry
about running out fuel. If it isnât its own anti-particle then we
can still use it, and not just for filler mass, it could be dumped into black holes
as power supplies for instance. Also I joked once about what I call the Dark
Telegraph, which would essentially be an ultradense line of matter between two places where like
any massive object it contracted space. Keeping something like that from collapsing
on itself is a lot easier with something like dark matter, you could send a beam between
relay points, or even two overlapping beams going opposite directions, and unlike normal
matter you can send your laser message right down that beam without needing to worry it
would scatter. Itâs not actually faster than light, but
from a practical standpoint it would be since along that path space would be contracted
so the message would get there faster than normal. If we cannot find an easy way to manipulate
the stuff though, there is again the black hole route. Dark matter would be eaten by a black hole
whose event horizon they crossed. Event horizons are quite tiny compared to
galaxies but in the long term, like we contemplated in the Black Hole farming video, youâd expect
black holes to eat a lot of them, gaining their mass energy and angular momentum, which
we discussed using in that video. So there are actually some uses for the stuff
inside the realm of plausible science, albeit we have to stretch a bit. As we learn more about the stuff we may learn
other uses for it or way to manipulate it, and Iâd say we can be optimistic on that
score for now, though we also need to be patient, it isnât likely we will crack the mysteries
of dark matter for some years. And it is mysterious stuff, though hopefully
a bit less so now weâre done for the day. Next week is going to be a look at asteroid
mining and weâll look at some confusion about both this topic and asteroids in general. Weâll probably be spending a fair amount
of time in the near future discussing colonizing the solar system. We will be coming back to discuss cosmology
quite a lot before 2016 is over, but I am going to do a poll again. The winner will be next, next weekâs video
and odds are most of the next few will be from the runners up. Iâm thinking about switching this over to
the website, IsaacArthur.net, to just be an ongoing thing but it will be a Youtube poll
this week Here are the options:
First, a look at Cryptocurrency, both in the emerging use of it in things like bitcoin
and in how it and related concepts might impact civilizations down the road. Second, a similar topic, folks have been asking
me to discuss the concept of post-scarcity societies for a while, and explain what that
actually means and what some of the implications of that might be. For the third option I thought about taking
a deeper look at the concept of a Technological Singularity. We kind of brushed past it in the Transhumanism
video and a deeper look at this idea and artificial intelligence seems appropriate. For the fourth option weâll take a more
detailed look at SETI, the search for Extra-Terrestrial Intelligence, Iâd meant to give it an overview
in the video on Tabbyâs star but that got almost entirely cut out to look at the anomaly
in more detail. Quick channel update, as mentioned last week
the website, IsaacArthur.net, is now up, and all the audio is now available to listen to
or download at soundcloud. Regarding foreign language subtitles, which
I mentioned last time Iâve been considering, a subscriber pointed out Youtube has an option
I could enable to let viewers submit those so I went ahead and did that, and on screen
is a link to a quick 2 minute video from youtube that explains how to do that if you want to,
and since each video already has subtitles it does have an expedited methods where the
timing is already there and you can just click auto-translate if you like then just fix the
blatant translations errors. My only request is that no matter how funny
some of those automated botches might be you resist the urge to leave them un-fixed for
the humor value. Changing sentence structure or wording to
be more appropriate to that tongue I will leave to peopleâs good taste and judgment,
this channelâs audience usually exhibits a hefty surplus of both. Okay on that note, donât forget to hit the
like button if you enjoyed the video, and share it with others. Questions and comments are welcome, and you
can try out some of the other topics on the channel. Thanks for watching, and Iâll see you next
time!
I wonder if gravitation lensing calculations for systems far away from our galaxy need to take into account the dark matter in our solar system and in the milky way. If the dark matter bubble we are in has a lensing effect on all observations, maybe it brightens images which may effect 'star standard candle' luminosity.