- 1 day ago
American Museum of Natural History Astronomer Dr. Jackie Faherty joins WIRED to answer the internet's burning questions about the cosmos. How old is the universe?Could a solar flare destroy the internet? What would happen if two stars merged together? Where was the Big Bang located? Are non-spherical planets possible? Answers to these questions and many more await on Cosmology Support.
For information about the American Museum of Natural History, visithttps://amnh.orgorconnect with the Museum on YouTube at/americanmuseumofnaturalhistory
For information about the OpenSpace datavisualizationsoftware, visit:https://www.openspaceproject.com/
Director: Lisandro Perez-Rey
Director of Photography: Charlie Jordan
Editor: Paul Tael
Expert: Dr. Jackie Faherty
Line Producer: Jamie Rasmussen
Associate Producer: Brandon White
Production Manager: Jonathan Rinkerman
Casting Producer: Nick Sawyer
Camera Operator: Jeremy Harris
Sound Mixer: Sean Paulsen
Production Assistant: Ryan Coppola
Post Production Supervisor: Christian Olguin
Post Production Coordinator: Stella Shortino
Supervising Editor: Eduardo Araujo
Additional Editor: Sam DiVito
Assistant Editor: Justin Symonds
For information about the American Museum of Natural History, visithttps://amnh.orgorconnect with the Museum on YouTube at/americanmuseumofnaturalhistory
For information about the OpenSpace datavisualizationsoftware, visit:https://www.openspaceproject.com/
Director: Lisandro Perez-Rey
Director of Photography: Charlie Jordan
Editor: Paul Tael
Expert: Dr. Jackie Faherty
Line Producer: Jamie Rasmussen
Associate Producer: Brandon White
Production Manager: Jonathan Rinkerman
Casting Producer: Nick Sawyer
Camera Operator: Jeremy Harris
Sound Mixer: Sean Paulsen
Production Assistant: Ryan Coppola
Post Production Supervisor: Christian Olguin
Post Production Coordinator: Stella Shortino
Supervising Editor: Eduardo Araujo
Additional Editor: Sam DiVito
Assistant Editor: Justin Symonds
Category
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TechTranscript
00:00I'm Jackie Faraday from the American Museum of Natural History.
00:03Let's answer your questions from the internet.
00:05This is Cosmology Support.
00:11At Eagle Jomer asks,
00:14Hey Siri, how old is the universe?
00:17The universe is roughly 14 billion years old.
00:20And we get to that answer by looking out into the cosmos
00:24and seeing the most distant things that we can.
00:27The most distant thing in the observable universe
00:30is the cosmic microwave background radiation.
00:33That's the signal of the Big Bang.
00:35And right behind me, we have a representation
00:38of what the cosmic microwave background radiation looks like.
00:41Bluer colors or redder colors showing tiny temperature fluctuations
00:46for what might have been going on about 13.8 billion years ago.
00:51At Purposefully Lit asks,
00:53So did we decide if 3i Atlas is a comet or an alien ship at this point?
00:58I'm trying to see if I need to get my life together.
01:00You need to get your life together.
01:01It's just a comet.
01:02It's not an alien ship.
01:043i Atlas is one of three objects that were discovered
01:07that have a velocity that suggests
01:10that they are not gravitationally bound to the sun.
01:14They didn't come from the leftover material
01:16that is in our solar system,
01:18which is where the majority of our comets come from.
01:22The first one was Oumuamua.
01:24The second one is called Borisov.
01:25And then there's 3i Atlas.
01:27Oumuamua came in and had a composition
01:30that was most like what we would call an asteroid.
01:33Borisov grew a tail like we would usually see happen with comets
01:38as they get close to the sun.
01:39They're icier.
01:40So you see a nice, beautiful tail
01:41as they get hotter and closer to the sun.
01:433i Atlas arrived.
01:45And all the imagery that we've seen thus far
01:47indicates that it's got a tail, like a comet.
01:50So 3i Atlas is still a really exciting object,
01:55even if it isn't the alien ship
01:57that's gonna take everybody to a different place.
01:593i Atlas is an object formed out of the material
02:04from another solar system.
02:06At M5 Defense asks,
02:09is the universe infinite?
02:11In an infinite universe, it's infinite in all directions.
02:15Lines of light stay parallel forever.
02:18We refer to as a flat universe.
02:22In a finite universe,
02:23the structure would have to curve back on itself.
02:26So it could be a curved structure,
02:28like a spherical structure,
02:30or it could be open on either sides, like a saddle.
02:34Studying the shape of the universe
02:36is a major aspect of astrophysical research.
02:39All we're really referring to in this case
02:41is how light as it's moving
02:43is moving either parallel or it's curved.
02:47So our current thinking now
02:48suggests that we live in an infinite universe.
02:52At TBG3963 asks,
02:55are we living in a multiverse?
02:57Yes or no?
02:58I can't answer that yes or no,
03:01because nobody knows.
03:02Is it possible?
03:03There's nothing I can tell you
03:05that says that it is impossible.
03:07So if you could, for instance,
03:09get to a point where you saw our universe
03:12from a bird's eye view,
03:14could you see other universes out there
03:16that had their own Big Bangs that started them?
03:19That is a possibility
03:21and one that scientists look into.
03:24That's not answering the question, though,
03:26if we live in a parallel universe
03:28where there's multiple versions
03:30of every scenario of every day you've ever lived.
03:33This is simply,
03:35are we the only universe that is,
03:38or is it possible that there are many out there?
03:40And the answer to that question is maybe.
03:45Okay, I'm f***ing Irish says,
03:47in Interstellar,
03:48why didn't approaching the black hole
03:50cause spaghettification?
03:53Spaghettification is the idea
03:55that as you get closer and closer
03:56to something that's very, very massive,
03:59the part of you that's approaching it
04:01gets yanked with a force so big
04:04that it starts to pull you apart.
04:06And if you've watched the movie Interstellar,
04:08Matthew McConaughey's character
04:10enters the event horizon.
04:12The event horizon is the point of no return.
04:14You have to get closer and closer and closer
04:17to the singularity or the center
04:18of that supermassive black hole.
04:20And because it's a hundred million solar masses,
04:24he has to get way closer
04:25to the center of the singularity
04:27before he feels that spaghettification.
04:30Doesn't mean he would have been feeling something,
04:32he would have been feeling something,
04:33but he wouldn't have been spaghettified.
04:34Just remember the difference
04:35between a supermassive black hole
04:38versus a stellar mass black hole,
04:41very different gravitational pulls on your body.
04:44Voodoo Mikava asks,
04:47what's at the center of the Milky Way?
04:49A supermassive black hole,
04:52which we call Sagittarius A-star.
04:55Also at the center of our galaxy,
04:57there's gas and there's some dust.
04:59I think of it like Metropolis or Times Square.
05:02It's where a lot of material is congregating,
05:06but all of it is kind of surrounding
05:08this supermassive black hole.
05:11OMBX from Reddit asks,
05:13what came first, stars or galaxies?
05:16The short answer is stars will come first.
05:19Stars are the components of galaxies.
05:21The first stars,
05:23because they were basically just hydrogen,
05:26were really large objects,
05:28probably a hundred times the mass of our own sun.
05:32And those didn't live for very long
05:34because they're so massive.
05:35And so as they blew up,
05:37they created the next generation of materials
05:40that could come together to make more stars.
05:43And as more stars formed,
05:45they clumped together.
05:46And those clumps,
05:47as they came together,
05:48formed galaxies.
05:50And the galaxies then formed together
05:52and they make galaxy clusters
05:54and all of it comes together
05:55to make the cosmic web
05:56that we know and love and live in today.
05:59Bradley Marquez asks,
06:01what is the largest single structure
06:03discovered in the universe?
06:04The largest structures that we know of
06:07are roughly a billion light years across.
06:10And what they are,
06:11are these gigantic walls of galaxies.
06:16So the image that's behind me
06:18is from a map that's been made
06:21of the Sloan Digital Sky Survey Galaxies.
06:24It's a telescope that was in the United States.
06:26And it measured how far away all the galaxies are.
06:29It's color-coded by their density.
06:31And there are some structures
06:33that we can tell are all linked together,
06:36where the galaxies are all held together
06:39into a coherent structure.
06:42And we call it the Sloan Great Wall.
06:45And for many years,
06:46that was the largest structure.
06:48But now there's a couple of others
06:49that are in competition for it.
06:51They each stretch a billion light years across.
06:55The Milky Way is a part of its own structure.
06:59And we call that Laniakeia.
07:02Astronomers have looked at that structure
07:03and seen a couple of things.
07:05One, it kind of looks like a spider web
07:07with filaments that are coming in and weaving around.
07:10Those filaments are made of galaxies.
07:12And then in the gaps between them,
07:14you can see there's voids.
07:17Much of this is being shaped by dark matter.
07:19So this web, this structure,
07:22which is the hierarchical map of the universe,
07:25is carved out by material that we can't even see.
07:30DJ Annam wants to know,
07:32what exactly is dark energy and dark matter?
07:35When you look out across the cosmos,
07:38you see the galaxies clump together.
07:40But in studying the way everything moved,
07:43we realized the stars in the galaxy
07:45were orbiting in a way we did not fully understand.
07:48Ones on the outside were moving faster
07:52than we thought they should be.
07:55Same thing with galaxies.
07:57Huge clusters of galaxies were being held together,
08:01seemingly by nothing.
08:03Some gravitational thing
08:05that was giving off no light whatsoever.
08:08And we dubbed it dark matter.
08:11Dark matter has the same gravitational properties
08:15that you and I have,
08:17but it gives off no light.
08:20So we cannot see it.
08:21And one other thing we discovered
08:23is that the universe has been expanding.
08:27And not only has it been getting larger,
08:29it's getting larger faster and faster.
08:32And we weren't sure what to make of that either.
08:35But when we realized that the most distant galaxies
08:38are way farther away than we thought they should be,
08:42we had to give a name to that,
08:44to this mysterious force
08:45that was driving our accelerating, expanding universe.
08:51And that has been called dark energy.
08:54So between those two,
08:56dark matter and dark energy,
08:58they make up roughly 95%
09:01of the mass budget of the whole universe.
09:03Here's a question from the astronomy subreddit.
09:06How do you think the universe will end?
09:08The universe is expanding
09:11and it's accelerating as it's expanding.
09:14So things are moving farther away from each other.
09:18If you wait long enough,
09:19everything gets farther and farther
09:21and farther away from each other.
09:23New stars can't form.
09:25The stars that are there will just peter out,
09:28which means the heat,
09:29what we call the entropy of the galaxy,
09:31will just start to slowly dissipate
09:33farther and farther down.
09:35And it just becomes a frozen, dark, cold world
09:39where you can't see anything.
09:40That is one,
09:42and maybe the most likely scenario,
09:44called the heat death or the big freeze.
09:46In an alteration of that,
09:49this same dark energy
09:51accelerates the expansion,
09:54pushing things farther and farther and farther away,
09:56even to the interiors of things.
09:59Galaxies themselves pushed apart from each other.
10:02All the gas,
10:03all the molecules,
10:04the protons,
10:05the neutrons,
10:06the quarks,
10:06it all gets decimated and eviscerated
10:10by this force.
10:11We call that the big rip.
10:13And then the third option
10:15is that the volume of space
10:18hits the boundary.
10:20that there is some point
10:22where we accelerate out
10:24and that gravity takes us back in.
10:27And when it does,
10:28the universe shrinks back down
10:30to a singularity point.
10:32And that singularity
10:33would be the end of the universe.
10:36And we call that the big crunch.
10:39While all of these are scenarios
10:41that are going to take the universe out,
10:43you do not have to worry about this right now.
10:46Each one of these
10:47is trillions and trillions
10:49a Google number of years
10:51in the distant, distant, distant future.
10:54I'd be way more worried
10:56about taking care of our own planet right now
10:58than how the universe
10:59is going to take out the universe later.
11:02Blue-haired hero asks,
11:04how do asteroid belts stay a belt?
11:06Wouldn't gravity pull the asteroids together?
11:08Great question.
11:09I'm going to answer that
11:10with a little show and tell here.
11:12In front of me,
11:13you might mistake them
11:14for just general rocks,
11:16but they're rocks from space.
11:17I have one here
11:19that is from a collision
11:20that's called Allende.
11:22And I have a second one
11:24from a fall that happened in Kansas.
11:27Both of these are from asteroids.
11:30The asteroid belt exists
11:31in a location between Jupiter and Mars,
11:34as shown in the image behind me
11:36with all of the green dots
11:37that are out there.
11:38This belt is not very dense.
11:41It was probably a planet
11:43that wanted to form,
11:44maybe Mars-sized
11:45or smaller than Mars-sized,
11:47but it's close to Jupiter.
11:49Believe it or not,
11:50but you could fit the entirety
11:51of all the other mass
11:52in the solar system,
11:53aside from the sun,
11:55inside of Jupiter.
11:56Jupiter has a very large gravitational pull.
12:00As a result,
12:02it wouldn't let a planet form
12:04in that vicinity.
12:06It would just gravitationally
12:08pull it apart.
12:09But every single movie
12:11you've probably ever seen
12:13that shows a space-faring person
12:17traveling around an asteroid belt
12:18has done it incorrectly.
12:20You're not gonna dodge
12:22and weave all of these rocks
12:24surrounding a belt.
12:26There's huge gaps.
12:27You can pass one of these rocks
12:29and not see another one
12:30for a significant amount of time.
12:33WritingConsistent834 asks,
12:35If an alien with a very,
12:36very strong telescope
12:37looked at the Earth
12:38from one million light-years away,
12:40would they be seeing
12:41how the Earth looked then?
12:43Meaning how it looked
12:44a million years ago.
12:46And the answer is yes.
12:48Behind me,
12:49there's an image
12:50of the Milky Way
12:51with a grid around it
12:54that is a million light-years
12:56in radius.
12:57And if there was a planet
12:59at the edge of any of that
13:00that was looking towards us,
13:02you would see the Earth
13:04in an ice age.
13:05You wouldn't see technology.
13:06You would see megafauna.
13:07If you were to go
13:0866 million light-years
13:10even farther away,
13:12a giant asteroid
13:13would be hitting the planet
13:14as dinosaurs were having
13:15their last big moments.
13:17This applies even
13:18in our own solar system.
13:20We're a little over
13:22seven light minutes
13:24away from the sun.
13:25So it would take us
13:26a little over seven minutes
13:28to know that something
13:30had happened
13:31because it takes time
13:33for the light
13:34to leave the object
13:35and arrive at your position.
13:37At2wells asks,
13:39why are sunspots black?
13:41Sunspots are black
13:43because they represent
13:44a slightly cooler temperature
13:48on the surface of the sun.
13:51So the sun is very
13:52magnetically active.
13:54And sometimes it,
13:56for lack of a better expression,
13:58it burps.
13:58When it does,
14:00it's spitting out
14:01some material
14:02and the surface
14:03might be representative
14:04of a strong area
14:06of magnetic fields.
14:08And it doesn't have
14:09as much convection
14:10or the ability
14:12for heat
14:12to leave the sun,
14:13which is why
14:14it looks to be
14:14a darker color.
14:15And the sun does
14:16go through a cycle
14:18where you see
14:18lots of sunspots
14:20to weigh less sunspots.
14:21When you get more sunspots,
14:23you also get more
14:23of these burps
14:24where more material
14:26will leave the sun,
14:27come towards the earth,
14:28and we can have
14:29geomagnetic storms
14:30that cause fun things
14:32like the aurora borealis.
14:34Here's a question
14:35from the
14:36No Stupid Questions
14:37subreddit.
14:38Would a solar flare
14:39destroy the internet?
14:41The answer to that
14:42is probably
14:42a little bit complicated.
14:44It wouldn't destroy
14:44the internet.
14:45It's hard to destroy
14:45the internet.
14:46But it could cause
14:47quite a bit
14:48of technological damage.
14:49It's a very active star
14:51and sometimes it has
14:53coronal mass ejections
14:55that come off of it.
14:56What we're showing you
14:57is a big one.
14:58It was called
14:58Bastille Day
14:59and it sent
15:01a whopping amount
15:02of charged particles
15:03towards the earth.
15:04The earth, though,
15:05has a very protective boundary
15:07which is this blue magnetic field
15:09that you can see
15:10surrounding the earth
15:12and that helps us a lot.
15:14Our magnetic field
15:15ends up cascading
15:17the plasma
15:18down across the earth
15:19centered at the poles
15:21which is why
15:22you can get
15:22these gorgeous
15:24light shows
15:25closer to the northern
15:27or southern latitudes.
15:28Also, this energy
15:30that comes from the sun
15:31that interacts
15:32with our planet
15:32can overpower
15:34a grid
15:35or can actually hit
15:36some of the satellites
15:37that are orbiting
15:38the earth.
15:38What we do now
15:39is we turn the satellites
15:41off when we suspect
15:43there's a major
15:44magnetic storm happening.
15:45iamedac asks
15:47what is the difference
15:48between dwarf planets
15:49and other planets?
15:50Is it just size
15:51or are there other factors?
15:53The dwarf planet definition
15:55came in the early 2000s
15:57when astronomers voted
15:58on a new definition
16:00for the word planet
16:02and the object
16:02that really made
16:03everybody vote on it
16:04is Pluto.
16:06So the difference
16:06between a planet
16:07and a dwarf planet
16:08is are you dominating
16:10your area or not?
16:12Jupiter, for instance,
16:14it's got an asteroid belt
16:15around it.
16:16It's got nearly
16:17a hundred moons around it.
16:19Jupiter is dominating
16:20its area of the solar system.
16:22Pluto just doesn't do that
16:24in its area
16:25and so for that
16:26it got demoted
16:28to dwarf planet status.
16:30Another clear quirk
16:32about Pluto
16:33is you can see
16:35all of the other orbits
16:37of the main planets
16:38of the solar system.
16:40They really form a plane,
16:41a nice plane
16:42with a little bit of deviation
16:43but a nice plane
16:44around the sun itself
16:46but Pluto's off
16:48by tens of degrees
16:49from the orbit
16:50of all of the others
16:51and so as it goes around
16:53it looks like it's off kilter
16:55from the rest
16:55of the solar system.
16:56So that was always
16:57a striking quality
16:58of Pluto
16:59that made people feel
17:00a little less comfortable
17:02with calling Pluto
17:03a planet
17:04versus this new designation
17:06for it
17:07which is a dwarf planet.
17:08Noble Pups asks
17:10what would happen
17:11if two stars merged together?
17:13It's not that easy
17:15to get it to happen.
17:16Gravity is more interested
17:19in getting the objects
17:20to orbit each other.
17:21Small stars can do it
17:23and it can be a nice merger
17:24an interesting little explosion
17:26it will be an explosion.
17:28The bigger the star
17:29or the more massive
17:30the objects that are merging
17:31the event gets crazier
17:33and crazier.
17:34You can get
17:35for instance
17:36two high mass stars
17:38to slam into each other
17:40and when they do
17:41they give off
17:42an enormous amount
17:43of energy
17:44so much so
17:45that you might get
17:46what's called
17:46a gamma ray burst
17:48which is the most energetic
17:49kind of explosion
17:50that we see
17:51throughout the universe
17:52and famously
17:53we saw two neutron stars
17:55merge with each other
17:56and the result
17:57was a wobble
17:59in the entirety
17:59of space-time
18:00that we could detect
18:01from here on Earth.
18:02At Rachel in Canada asks
18:04Wait, there are rogue planets now?
18:07Yes.
18:08Or at least there's
18:09a word that we use
18:10to describe objects
18:12that are really low mass
18:13wandering the cosmos
18:15by themselves
18:16without a host star.
18:18Maybe they got ejected
18:19from their home
18:20planetary system
18:21maybe they formed
18:23that way on their own
18:25but what we know
18:26is that there's
18:27Jupiter-like planets
18:28that are wandering around.
18:30The image behind me
18:31is showing the night sky
18:33but then
18:33we can actually show you
18:35with these blue circles
18:36the locations
18:37of stars
18:38where we've found
18:40planets around them
18:41but then
18:42some of those blue circles
18:44are going to be
18:44surrounding nothing
18:45because they are
18:47freely wandering
18:48dots in the sky
18:49that are rogue worlds.
18:51We actually think
18:52right now
18:53every star
18:54has at least one planet
18:55if not more
18:56so finding planets
18:58is commonplace.
19:00How common rogue planets
19:01are is an open question
19:04in astronomy right now.
19:06DW Redd asks
19:07is there any possibility
19:08of having non-spherical
19:10planets out there?
19:11By definition
19:12by how the International
19:13Astronomical Union
19:14defines them
19:15need to be round.
19:17You can be a little bit
19:18oblate
19:18meaning pulled apart
19:19a little bit on the sides
19:20but for the most part
19:22by our definition
19:23you're supposed to be round.
19:24There's a lot of objects
19:25out there in the solar system
19:26that aren't round.
19:28Here is an image
19:29for you to see
19:29is called Bennu.
19:31Bennu is an asteroid.
19:32We've actually
19:33gone to Bennu
19:34landed on it
19:35taken a sample
19:36and brought it back
19:37but you can see
19:38it's quite an irregular shape
19:39when you go up to it.
19:40It looks like
19:41it's a conglomeration
19:42of a lot of rocks
19:43that have slammed
19:43into each other.
19:44Those kinds of structures
19:45we see throughout
19:46the asteroid belt
19:47you can see them
19:48even in tiny moons
19:50like the moons of Mars
19:51which are called
19:52Phobos and Deimos
19:53but for a planet
19:55to be called
19:55a planet
19:56you need it
19:57to be round.
19:58At the Physics Memes
19:59asks
20:00is there a spot
20:01where the Big Bang
20:01happened?
20:02Do we know where it is?
20:04Is it the center
20:04of the universe?
20:06One of the things
20:06that people have
20:07commonly through time
20:09wanted to think
20:10is that there must
20:11be a center.
20:12Maybe the Earth
20:13was the center
20:13of the universe.
20:14That was a thought process
20:15before we really understood
20:16that we went around the sun.
20:18Similarly,
20:18in cosmology
20:19one way to look out
20:20into the universe
20:21is to feel
20:21that there must be a center
20:23because in all directions
20:24it looks like
20:25we have some homogeny
20:27to the way
20:28that the galaxies
20:29are laid out.
20:30But every single planet
20:31with a little Earthling
20:33on it
20:33or another species
20:34on it
20:35would be looking out
20:36and thinking
20:36the same thing.
20:37There is no center
20:39to the universe.
20:40Everything is a part
20:41of the exact same
20:43extremely large structure.
20:46We're on the surface
20:47of a balloon.
20:48The Big Bang
20:48is when the balloon
20:49started to blow up.
20:50And then as it did
20:51everything started
20:52to expand out.
20:53The space
20:54that you're in
20:55right now
20:56came from that same moment.
20:57We live on the outside
20:59of the balloon though.
21:00The outside of a balloon
21:01has no center.
21:03It's a surface
21:04that is surrounding
21:05a material.
21:07It's uniform
21:07for everyone
21:08in each direction.
21:10Frank Sizzle asks
21:11how do we know
21:12the shape of our galaxy?
21:13No one's been outside
21:14to take a look.
21:15The image behind me
21:16shows you
21:17what we think
21:18the galaxy
21:19probably looks like
21:20and that's based
21:21on observations
21:22that we have done
21:23from Earth.
21:24Then we can look
21:26beyond our galaxy
21:27and start to see
21:28the shapes
21:29that they have
21:30and infer
21:31based on what we see
21:32we likely
21:34have a shape
21:35akin to a spiral.
21:36Our best estimates
21:38the galaxy
21:39is 150,000
21:41200,000 light years
21:42across
21:43but then only
21:44like a thousand
21:45light years thick.
21:47It's compact.
21:48Are we definitely
21:49a spiral?
21:50There's no definites
21:51on this
21:51but observational evidence
21:53from looking at
21:54the way the stars move
21:55and how gas
21:56and dust clumps
21:57indicates that
21:58we're a spiral galaxy.
21:59At Regastriga asks
22:01what are the different
22:02types of stars?
22:04Size
22:05and temperature
22:06really differentiate them.
22:08So the highest mass stars
22:10called O stars
22:12or B stars
22:13and then there's
22:14A stars
22:15which are medium-sized stars
22:17and then there's stars
22:18like our sun
22:19an F
22:20or a G star
22:21or even a K star
22:22then it starts to get
22:24into the low-mass stars
22:26and those are
22:27the M stars
22:28and then
22:29you enter a regime
22:30where
22:31you're not even
22:32talking about
22:33a star anymore
22:33but it probably forms
22:35in a similar way.
22:37Some people call them
22:38failed stars.
22:39They're objects
22:40that don't have
22:41enough mass
22:42to get hydrogen
22:43burning at their core
22:45to get a nuclear
22:46engine going
22:47and we call
22:48those things
22:49brown dwarfs
22:50and they get the letters
22:51L, T and Y.
22:53Hanny Zizo 58 asks
22:55are super earths real?
22:57Super earths are real
22:59but I think they sound
23:00more exciting
23:01than what they are.
23:03A super earth
23:04is a planet
23:07that is bigger
23:08than the earth is.
23:10Sometimes they're also called
23:11mini-Neptunes
23:13which probably doesn't sound
23:14quite as exciting
23:15as super earths.
23:16A super earth will be
23:17about twice the radius
23:19of the earth
23:20and you can fit
23:20probably two to ten
23:22earths inside of it.
23:23And as we've scanned
23:24the cosmos
23:25the most common
23:26kind of planet
23:27that we've been finding
23:29has been
23:30this super earth
23:31sized planet.
23:32And it's intriguing
23:33that we don't have one
23:36in our solar system
23:39and astronomers
23:39never like
23:40to feel like
23:41our solar system
23:43is special
23:44in some way.
23:45So either
23:46we lost our super earth
23:47or there is
23:49some concept
23:50that there's
23:51a ninth planet
23:52beyond Pluto.
23:54Just your boy T asks
23:55why is the night sky
23:57dark?
23:58The short answer
23:59is because
24:00the universe
24:01is kind of infinite.
24:03This question
24:04is also something
24:05called
24:05Olber's paradox.
24:07If every line of sight
24:09that you can point
24:10your figure at
24:11in the sky
24:12lands on a star
24:13why isn't the night sky
24:16endlessly filled
24:17with light?
24:18So while nearby stars
24:19you can see really well
24:20as you get farther
24:21and farther
24:22and farther away
24:23the light
24:23it just takes longer
24:25to reach us
24:26from those locations
24:27and at some level
24:29it gets shifted
24:30to a wavelength
24:31that we can't see.
24:33Bring a telescope in
24:34then you can see more.
24:36So for instance
24:37the Hubble Space Telescope
24:38famously took an image
24:39where it stared
24:40at a seemingly
24:41dark patch of sky
24:43continuously
24:44for several days
24:45and it was
24:46filled
24:46with galaxies.
24:48Lots and lots
24:49of galaxies.
24:50But that kind
24:51of ability
24:52to see
24:52is not within
24:53the human capacity.
24:55We are just not
24:56that sensitive
24:56to light.
24:57Here's a question
24:58from Cora.
24:58how many stars
25:00are visible
25:00from Earth?
25:01So if you're
25:01in the northern hemisphere
25:02you've got maybe
25:034,000, 5,000 stars
25:04available to you
25:05from the southern hemisphere.
25:06So maybe like
25:079,000, 10,000 stars
25:08in total
25:09that the best conditions
25:10on planet Earth
25:11best eyeballs
25:12that we can possibly
25:13put out there
25:14could actually see.
25:15So what we can
25:16bring up here
25:17is a small sample
25:19of roughly
25:20350,000 stars
25:22that we have mapped
25:24that we know
25:24where they are
25:25and how they're moving.
25:26You can't see them
25:27because your eye
25:28is just not
25:29sensitive enough
25:30to be able
25:31to see these stars.
25:33Light pollution
25:33is making it
25:34more difficult
25:35for you to see them.
25:36Your eye makes it
25:37difficult for you
25:37to see.
25:38I would just
25:38encourage everybody
25:39to try and preserve
25:40their nighttime sky.
25:41This is the best view
25:42that you're ever
25:43going to get
25:43of what's out there
25:44in the cosmos.
25:45So those are all
25:46the questions for today.
25:48Thanks for watching
25:49Cosmology Support.
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