What’s the most distant thing we can see with the naked eye? What about with a telescope? What about at other wavelengths? Is there anything more to see? I discuss these questions and more in today’s Ask a Spaceman!

This episode is sponsored by BetterHelp. Give online therapy a try at betterhelp.com/spaceman and get on your way to being your best self. Visit BetterHelp to get 10% off your first month!

Support the show: http://www.patreon.com/pmsutter
All episodes: http://www.AskASpaceman.com
Follow on Twitter: http://www.twitter.com/PaulMattSutter
Read a book: http://www.pmsutter/book

Keep those questions about space, science, astronomy, astrophysics, physics, and cosmology coming to #AskASpaceman for COMPLETE KNOWLEDGE OF TIME AND SPACE!

Big thanks to my top Patreon supporters this month: Justin G, Chris L, Barbara K, Alberto M, Duncan M, Corey D, Tom G, Naila, John S, Joshua, Scott M, Rob H, Louis M, John W, Alexis, Gilbert M, David L, Rob W, Valerie H, Demethius J, Jules R, Mike G, Jim L, Scott J, Lewis I, Peter E, David S, Paul L, Jon-Boy, Scott R, Tim R, Mark R, Alan B, Craig B, Mark F, Richard K, Maureen R, Stace J, Stephen S, Stephen J, Joe R, David P, robert b, Sean M, Tracy F, Sarah K, Ryan L, Ella F, Sarah K, Richard S, Sam R, Thomas K, James C, Syamkumar M, Homer v, Mark D, Bruce A, Steven M, Bill E, Tim Z, Linda C, Scott M, Avery P, Farshad A, Kenneth D, Gary K, Paul G, David W, dhr18, Lode S, Alyssa K, Bob C, Simon G, Red B, Herb G, Stephen A, James R, Robert O, Lynn D, Jeffrey C, Allen E, Michael S, Reinaldo A, Jessica M, Patrick M, Amy Z, Sheryl, John G, David W, Jonathan S, Sue T, Josephine K, Chris, P. S, Michael S, Erlend A, James D, Larry D, Matt K, and Charles!

Hosted by Paul M. Sutter.

 

EPISODE TRANSCRIPTION (AUTO GENERATED)

When the idea of a sun centered or heliocentric universe first started to arrive on the scene in the late 1500 early 1600 in Europe, there was a very reasonable objection to the idea. And this objection came from Tycho Brahe, perhaps the greatest astronomer to ever live, at least according to Tycho Brahe. And he said, look. Let's say we live in a solar system, cute name, by the way, for for this setup, and the earth revolves around the sun. That means over the course of a year, the Earth changes position by over 180,000,000 miles.

You know, 1 during the summer, we're on this side of the solar system. During the winter, we're on the opposite side. That's a big difference. That means, if I look at a distant star from these two vantage points, then the position of the star on the sky should slightly change because I'm looking at it from these these vastly different reference points. And so, he he went out to perform that measurement and found no shift in position with the stars at all.

And he was the world's greatest astronomer, so if anyone's gonna do it, it's him. And so he said, look. Like, I I understand mathematics, and that we have one of 2 situations, this lack of observation of the shift of the positions of stars. This either means that the earth is the center of the universe, in which case over the seasons, you will never see a shift because you always have the same perspective, Or, you know, we could live in a Sun centered universe, a solar system, a heliocentric universe. But in order for this to be true, the stars have to be so far away that it's impossible for me, the world's greatest astronomer, to measure a shift in their position.

When according to my calculations, they have to be at least 700 times further away than Saturn. And now we know that the nearest stars are a little bit more than 700 times further away than Saturn. And it's in I'll admit, it's a little funny to think back about how ridiculous that sounds like. Oh my gosh. The star is 700 times further away than Saturn.

They're, like, 70,000 times further away than Saturn, the nearest star. But it took 200 years to resolve. You know, Tycho Brahe raised this objection in the early 1600. It wasn't until 18 thirties that an amateur astronomer, Friedrich Bessel, finally managed to measure the distance to a star. It was some random star, 61 Cygni.

It's about 10 light years away. He also invented the term, light year, by the way, to communicate how vast this distance is. But 200 years to measure the distance to one of our nearest neighbor stars. 2 centuries, Tycho Brahe's objection stood. And even though astronomers would eventually adopt the heliocentric model, mostly because it made horoscopes easier to predict, but that's a different episode.

Even though they did this and adopted, they could they knew. They're like, well, Tycho was kind of right. The stars should be measurable. This shift should be measurable, of course, across the seasons. It took 2 centuries to answer that.

I mentioned this because we're about to casually discuss distances and measurements, and I just want us to be a little bit grounded that actually taking these measurements and achieving these distances are just a little bit challenging. It took 200 years of work for us to get our first reliable distance measured to a star. That star was 10 light years away. Obviously, we've gotten a lot better at it since the 18 thirties, but it took a long time, over 200 years of having telescopes before we could really nail this. And so I just want us to ground this discussion, now that we're properly grounded, we can explore very distant things, which is pretty fun.

By the way, I also like to point out that distances measurements in astronomy are incredibly difficult, because there are 2 challenges. 1, sometimes things are just really really far away, which makes them dim on our sky, which makes it hard to see and hard to measure. Also, some things are just by nature, small and dim, and makes it very, very difficult to spot. You know, we had this whole discussion recently about near Earth objects and how hard they are to find, even though they're really close to us, closer than the nearest stars, that's for sure. But they're so small and they're so dim, they're almost impossible to see.

An example of this, this random fact, we were able to measure the distance to stars before we discovered the planet Neptune. I'll say that again because it's pretty wild. We were able to measure distances to stars before we even knew that Neptune existed. And even though Neptune is really close, it's comparatively small and dim. Astronomy is kind of challenging, that's why it's a science, and that's also what makes it so much fun.

The most distant planet that you can see by the way with the naked eye is is almost always Saturn. Some people can see Uranus, the next most distant planet out. It appeared in some old star catalogs, but it was mistaken for a planet. It's it's, like, probably below the vision of almost everybody, But some people can at least claim to see Uranus. I'm not gonna always believe them, but at least they can say.

So it's right on the edge. So that's the most distant planet you can see. When it comes to stars, the nearest visible star is Alpha Centauri, which is about 4 and a quarter light years away. That means that the light from Alpha Centauri left over 4 years ago. Think of what you were doing 4 years ago at this time.

4 years is quite a long time. And and all that time, think back the 4 years ago. The the seasons coming and going. Maybe your kids getting older. Maybe you getting older.

A few more gray hairs here and there. 4 years. And that light started that journey 4 years ago and has been sailing through interstellar space all that time before finally landing on your retina. It's just one of these astounding aspects of astronomy that I always absolutely adore. 4 years.

That light could have graduated high school in that time. This is crazy. Anyway, as for the most distant star that you can see with the naked eye, I I need to make a little digression here. And we need to talk about the absurd and somewhat comical system that astronomers use to measure how bright things appear in the sky. Because this this number, this measurement is not going to come up so much in this episode.

But I've been honestly, I've been wanting to talk about it for a while, and this is the perfect way to do it. And you're going to encounter this if you are in any way associated with astronomy nerd atry. You will encounter this kind of measurement system for measuring brightnesses, because it makes no sense, and it's absolutely confusing. So, in in your life, you are going to encounter this system, especially at all those swanky, fancy astronomy parties, and I want you to feel like you belong. So here is this system that astronomers use to measure brightnesses, like a calibration, like a temperature scale, or a size scale.

This is their scale. To start off, we need to acknowledge that different objects have different brightnesses. This is a generally true statement. Another generally true statement is that sometimes objects can appear brighter because they are genuinely brighter, they are giving off more light, and sometimes objects can appear brighter simply because they are closer. For example, Jupiter is giving off far less light than Alpha Centauri, but Jupiter appears much brighter on the sky because it's so much closer to us.

We measure the the true amount of light coming off an object with something called the luminosity. So objects with greater luminosity are emitting more raw power of light. That's connected to the brightness that we see, but there's more to the story because we have to fold in distance to get a measurement of the actual brightness that we perceive. On our sky, stars have a variety of brightnesses regardless of their true luminosity. Some stars appear brighter, some appear dimmer.

Sometimes, they are bright because they genuinely are larger, brighter, more intense, more luminous stars, and sometimes not. Back in the day, we didn't know this. We didn't know that the stars were distant. We didn't know that the stars had different distances from us. We assumed that they were all just pasted on the celestial sphere, out beyond the orbit of the planets.

And so all we had was just, okay, some stars, like Sirius and Betelgeuse look super bright and a bunch of other random nobody stars don't look super bright. So the ancient Greeks, and yes, we are digging way into the back catalog for this system, devised a scheme where they classified stars according to magnitude. They said that stars of the first magnitude were the brightest, stars of the second magnitude were the next brightness, all the way down to stars of the 6th magnitude. So they had 6 categories, 6 buckets for brightnesses of stars. In the top bucket, the first magnitude were the brightest ones, and then the 2nd brightest category, 3rd brightest category.

Why 6? Like, why 6 subdivisions for these magnitudes, for these categories? I mean, first, why not? Get off my back. We can just do whatever we want if we feel like it.

2nd, this magnitude system was devised so that very roughly, remember this is all done by eye with no precision measurements whatsoever, the system was devised so that roughly, stars in one magnitude were half as bright as the stars in the next magnitude up. So at the very top, in your first magnitude stars, you have the absolute brightest stars by eye, you have that one, that one, that one, that one, that one. They're all pretty much the same brightness. They're all the brightest. Top prize.

Then, you look at stars that are roughly half as bright, which is as good as you're gonna get by I, and those go in the second category. And then half as bright as that, go in the third category. Once you get down to the 6th magnitude, there are no more stars that you can see. There are the 7th magnitude stars are half as bright as the dimmest stars you can see on the sky, and so that's it. Like I said, this is all sketchy.

It's all very rough guesses. This was all firmed up and standardized in the 19th century as was the fashion at the time. And so that's why when we talk about stellar magnitudes, which is different than their luminosity, the luminosity is the raw power coming out of the star, the magnitude is a measure of the brightness that we see on the sky. And that's why lower number magnitudes means brighter star. A magnitude 1 star or a star with a magnitude of 1 is brighter than a star with a magnitude of 2 which is complete opposite to what you think it would be.

You'd think, okay, if something's brighter, it should have a larger number attached to it. I know that's how you would think. But instead, we need to think of it as a rank of brightness. Stars of magnitude 1 are 1st rank. They're at the top of the order.

Stars of 2nd magnitude are 2nd rank. So this is a rank ordering of brightness of stars, which is okay. We can kind of accept that. Except, this is where it gets really weird, that kind of magnitude, the magnitude that we see with the naked eye on our sky is known as apparent magnitude, the perceived magnitude. Once astronomers were able to finally measure the distances to these stars, they could correct the apparent magnitude because some stars are bright because they're close, some stars look very very dim to us, but in actuality, are incredibly bright.

They're just super far away. So we need to switch from what we call apparent magnitude to absolute magnitude. Absolute magnitude is the magnitude that you would measure from a standardized distance of 10 parsecs away, so about 40 light years. Why 10 parsec? I don't know.

Seemed convenient at the time. The absolute magnitude is connected to the luminosity of the star, because now you're doing an apples to apples comparison. You're ignoring distance. You're looking at the true brightness. We call this the absolute magnitude.

And once you make this correction for distance, once you standardize the distance, stars can be way wacky bright. Because the stars that are first magnitude to our eyeballs looks pretty bright, and and in general, they're pretty bright stars. But then there's some random dim star that just happens to be super far away, and if you were to get up close to it, it's way brighter than Sirius, than Betelgeuse, than any of the bright stars on the Vega, any of the bright stars on our sky. Way brighter. So we've got a problem.

The brightest stars are first rank, first magnitude, and we've already decided that dimmer stars are second rank or third rank or 4th rank. So so what's brighter than a first rank star? A 0th rank star. And what's brighter than that? A negative 1th rank star, and then a negative 2th rank star.

Because that's the opposite direction. There's no other directions to go. So now, thanks to the ancient Greeks, who decided on a rank ordered system for measuring and categorizing stellar brightness that we see the with the naked eye, we're in the awkward position of calling super bright stars something like Betelgeuse has an absolute magnitude of negative 7.2, and that's supposed to indicate that this is far brighter than a negative 4 magnitude star or a 3 magnitude star, like this makes any sort of sense whatsoever. Anyway, I just wanted to fill you in, because you are guaranteed to encounter this horrible system, and you can thank the ancient Greeks for the mess we're in. And we need to take a quick pause so that I can let you know that this show is sponsored by BetterHelp.

You know, we've talked a lot about time in this series. What is the nature of time? There's all sorts of physics concepts that we explore about the nature of time, but there's also this human part of time or the experience of time that we all know so intimately, and yet we don't understand. And one of the biggest things about time is that we all wish we had more of it. Like, if there's an extra hour in the day or if we could just put things on pause, what would we do?

I'd probably do more episodes. I don't know. But, like, we all wish that time was different. And one of the coolest things about therapy that I've seen in my own experience is that, you know, by realigning your perspectives, by realigning your expectations, you can get a better sense of your own flow of time. So that time does its thing outside of our control, but you can be a part of that flow.

If you're thinking of starting therapy, give BetterHelp a try. It's entirely online. It's convenient, flexible, suited to your schedule. Fill out a brief questionnaire, and boom, you're connected to a licensed therapist. You're done.

Visit better help.com/spaceman today to get 10% off your 1st month. That's better help, he l p, dot com slash spaceman. So we've covered the nearest star that we can see, which is Alpha Centauri. That is not the nearest star to the Earth. That's Proxima Centauri, which is a little bit closer, but because Proxima Centauri is a red dwarf, we can't see it with our naked eye.

The brightest star we see on the sky is Sirius aka the dark star, which is totally a really bright star, but it's only 8.6 light years away. So it gets to be nice and bright on its own and it gets to be super close. As for the most distant star visible with the naked eye, that's a bit up for debate because, a, everybody has different eyes, and, b, stars have a tendency to vary in brightness. They can be a little bit brighter and a little bit dimmer. With those caveats aside, when you ask, okay, on average, what is the most distant star visible to the most number of naked eyes with, you know, decent functioning night vision across the world, you know, taking away light pollution and all that stuff.

The general consensus is a little star, well, actually, it's a big star, in the constellation Cassiopeia. It's called v762 Cas. It's a variable star, so at its dimmest, as an apparent magnitude of 6.02, and at its brightest, a whopping 5.92. So it's either way, it's like right at the edge of human visibility, without a telescope, without binoculars, without anything. And you need an absolute clear crystal clear dark sky night in order to see it, but it's there, right at the edge of visibility.

In reality, it is 100,000 times more luminous than the sun. It is putting out a 100,000 times more light than our own sun is, which is insane. But it's over 16,000 light years away, which is why it looks so dim to us. Let that sink in. The light that left this tiny star in the constellation Cassiopeia left the surface of that star 16,000 years ago.

16,000. That is before writing. That is before cities. That is somewhere around the dome of agriculture, maybe even before it, if I'm remembering right. 16000 years, that light has traveled the interstellar depths before reaching your eyeball.

This star, a 100000 times brighter than the sun, is so bright it would literally melt your face off if you were to approach it. And it is so far away that despite all of its power and all of its ferocity, it appears as only the dimmest pinprick of light on our sky. All of the stars that we see with the naked eye, without a telescope, are giants. They are much more massive than the sun. They are the only ones bright enough to be seen at interstellar distances, even a few light years away, with the naked eye.

Stars like our sun, stars smaller than the sun, are just too dim to overcome the light years of distance between them and us, making them invisible without a telescope. To give you a sense of how many stars there really are in that volume contained by the distance to v 762 CAS, that 16,000 light years, you know, imagine a sphere with a radius of 16,000 light years going right up to v762 Cas. Within that volume, within that sphere, there are about 9,000 stars visible to the human eye. There's about a 1000000 more that are invisible to us. But while that's the most distant star, it's not the most distant thing.

That honor goes to a Patreon ad. That's patreon.com/pmsutter, and it's how you, yes you, can keep this show going. If you've been thinking about it, now is the time to do it. I truly do appreciate all of your support, and your support shines with radiant glory, absolute and apparent magnitudes, in the negatives, all across the universe, and I truly do appreciate it. No.

The actual most distant thing that you can see with the naked eye is the Andromeda galaxy. Forever, we thought it was a nebula, just a collection of gas and dust and random stars, and then in the 19 twenties, Edwin Hubble discovered that it's it's a mere 2 and a half 1000000 light years away. You can't see any individual star in the Andromeda galaxy, but there's around a trillion of them, and so they combine their light together to make a a vague fuzzy patch on our sky. It's not the most visually impressive thing, but it's there. And when you look at it, you take that into account, that light travel time, 2 and a half 1000000 light years, that means 2 and a half 1000000 years ago.

There weren't even humans back then when the light from Andromeda started its journey. And we're not talking interstellar distances. We're talking intergalactic distances. That light has sailed through the void for 1000000 of years, and it landed on your eyes. I this like, you are literally connected to the stars, not in an astrological kind of way, but a physical kind of way.

Like, light from distant stars is now touching your eyes. It's becoming a part of you. This is amazing. There's still one more thing more distant than that we can see, and these are rare transient events. We're talking explosions here.

Most of the visible supernova that become apparent on our sky happen in our galaxy, but there are more powerful explosions that occur throughout the universe, like gamma ray bursts. There was a gamma ray burst back in 2008 that was visible to the naked eye for about 30 seconds before it faded away. So if you happen to be looking at just the right patch of the sky, at night, you'd see a little bright star, actually, it's more like a dim star, like, just barely appear on the edge of human vision, before going away. The distance to that, this particular one, it was grb 080319b, for those of you keeping score at home, and this explosion went off, 7,500,000,000 light years away. 7.5000000000 years.

That's amazing. That's amazing. Obviously, with a telescope, the universe opens up before us because telescopes are light buckets. They allow us to see both very dim things because they can collect more light than a human eye, and they allow us to see very small and distant things because they offer greater resolution through magnification. So those two properties of a telescope combined allow us to see, like, really really really far.

We can see We can map stars piercing into the Milky Way, tens of thousands of light years. We can see individual stars. We can see individual galaxies. We've mapped galaxies out billions of light years away, done surveys of them. But even our most advanced telescopes, and I really should do an episode on upcoming mega observatories, so please just ask, can't see the most distant stars and the most distant galaxies alone.

The most distant ones, the ones at the very edge of the observable universe, they are just too far away. They are too small. They are too dim. Even with the James Webb Space Telescope, or the Veracy Rubin Observatory, or the 30 meter telescope, any of our giant mega observatories, it's just too much. They can't do it.

Thankfully, nature helps us along with a little trick and that trick is called gravitational lensing. Say I'm looking at a distant galaxy. In between me and that galaxy is a big old massive object, like a galaxy cluster, like something really big and heavy. That massive galaxy cluster has a lot of gravity and so it bends space around it very, very strongly. And what happens is that light coming out of that distant galaxy, that distant object, as it approaches the galaxy cluster that that's in the middle, the intervening galaxy cluster, the light gets bent, and it acts like a lens.

It acts literally like a magnifying lens. It's it's the exact same equations that tell us how it behaves. And so if things line up just right, we can look through a Galaxy cluster, at an even more distant object, and the light from that object will be expanded and it will be amplified. We can get magnification effects up to 10,000 times. Imagine a pair of binoculars that can magnify by a power of 10,000.

That is what we are able to do with this gravitational lensing technique. So when we are very careful and very observant, we can occasionally get a glimpse of objects sitting even deeper into the dark, far beyond the reach of even our most powerful telescopes. With that technique, we can now meet the most distant known individual star. That star is called Earendel, and yes, that's a nerdy Lord of the Rings reference, which is itself a nerdy reference to the Anglo Saxon myth of the morning star. That one star, Earendel, individually imaged like a single speck, a single star seen through gravitational lensing around a massive galaxy cluster.

That star sits roughly 28,000,000,000 light years away. This is truly mind boggling to me. Due to the expansion of the universe, we know that this star formed roughly 900000000 years after the big bang, making it among the 1st generations of stars to ever appear. This star is nearly 13000000000 years old. This star is older than the Earth, older than our solar system, older than the entire Milky Way galaxy.

It's doubtful that Earendel still exists. Bright stars like this do not live long. That means this star hasn't existed in our universe for 1000000000 of years, and yet its light still remains. If I was in a more poetic mood, there would be something beautiful to say about it, but instead, let's just soak it in. The bare fact.

The star existed 13000000000 years ago, lived its life and died, But its light persists in the cosmos and reaches our telescopes today. But that's still not the most distant known object. That honor currently goes to, well, it doesn't have a nerdy nickname like Arendelle, sorry, it's just a phone number, Jade's GSZ 130. It was discovered with the James Webb Space Telescope there, no surprise because that's sort of its job, to discover distant objects. The current distance to this galaxy, and, yeah, in order to get even these kinds of distances, we can't just have a single star, we need an entire galaxy's worth of light.

That distance is currently pinned at 33.6000000000 light years. There are tentative observations of even more distant galaxies, but we haven't fixed. We haven't pinned the distance yet reliably. So this is the most distant confirmed object that we know of. At that distance, it means the galaxy was born within 400000000 years after the big bang.

It might even contain some remnants of the first generation of stars to ever appear in the universe. It's apparent magnitude, by the way. It's brightness as it appears on our own sky. If we're doing this ranking system of the Greeks, you know, 1st rank, 2nd rank, it's rank, 29th, which is kind of dim. We do know that there are more distant galaxies out there, more distant stars, but we can't see them yet.

We don't have the astronomical power to do it. This is something called the cosmic dawn, the dark ages, which you know, if you've listened to this show, I have a soft spot for. But currently, Earendel is the limit to what we can see with stars, and Jade's dash GS dash z 13 dash 0 is the limit to what we can see with galaxies. But that's still not the most distant observed thing. For that, you have to switch to different wavelengths of light.

These galaxies and stars are discovered in infrared or visible. Once you switch over to microwave, you can see an even more distant thing. We see something called the Cosmic Microwave Background. This is light that was white hot when it formed, when our universe was only 380000 years old, when it transitioned from being a plasma to a neutral state, released this white hot flash of of radiation that has persisted in the cosmos ever since. It is now redshifted all the way down to microwaves.

You know those old antenna TV, Or if you currently have an antenna TV, if you ever get static on the channel, about 25% of that static comes from the cosmic microwave background. That means this light was emitted 13.77000000000 years ago, has been sailing through the voids, the clusters, the filaments of the universe before landing on your TV. That's wild. It's we're soaked in it. We're soaked in this radiation.

And this light is right at the edge of what we can absolutely see, because the universe is only so old, and light can only travel so fast, that there is a limit. We do live in the center of a universe. Take that Kepler. In Copernicus, it turns out we are at the center in a certain way, because there is a limit to what we can see given the age of the universe. The Cosmic Microwave Background is right at the edge.

Imagine we live inside of a giant sphere with the Earth precisely at the center, and our Milky Way galaxy is right there next, you know, wrapped around us. And then, Andromeda is just like a little pinch away. And then, we do some galaxy surveys, and we can fill out the the large scale structure, the cosmic web around us. And then, oh, approaching the edge of the sphere, there's Earendel, there's the Jade's galaxy. And then you can imagine the cosmic microwave background as this, like, thin layer of paint right on the inner surface of this sphere, and that is what we are seeing.

It's right at the edge of what we can ever see. And so it's worth an ask. Can we see beyond that? The answer is not yet, but we might be able to pierce beyond the Cosmic Microwave Background. We can't do it in light because the Cosmic Microwave Background, it's this, like, curtain of radiation that obscures everything that happened before.

So we can't look directly with radiation to see beyond that thin skin of paint of the CMB and all the way to the edge and remember, this is also going back in time. So the Cosmic Microwave Background was generated when our universe was only 380000 years old. If we can get some sort of signal, it will be from a younger universe and a younger universe and then we're pushing all the way up to the Big Bang. We might be able to get very very close. Neutrinos were produced in abundance in the early universe.

Those could have streamed right through the CMB. If we build a big enough sensitive enough neutrino detector, we might catch some of those relic primordial neutrinos that would give us some sense of what the universe was like in its earliest days. And if we do detect one of those neutrinos, it would make it the oldest known thing, the most distant thing we have ever measured because that one neutrino that we detect would have originated, I don't know, like a few minutes after the big bang and then sailed through until it hit our detector. Plans are currently afoot to go even deeper with something called the big bang observatory. This is a gravitational wave detector that is designed to look for gravitational waves generated in the inflationary epoch.

We're talking less than a second after the big bang. If we detect those, that would be the oldest thing. It'd be beyond the film of paint of the CMB and like right at the microscopic edge of the limit of what we could possibly see. Those gravitational waves would be the oldest known things in the universe because they would have sloshed through space for 1000000000 of years, generated in the first second of the big bang before finally reaching our observatories. This is beautiful to me.

It's amazing to me. One of my favorite things about astronomy is that the farther out we go in distance, the further back we go in time. As we pierce further and further into the universe and we collect the most distant thing, The most distant star, the most distant galaxy. Mapping the CMB, pushing further. We are peeling back the history of the universe itself.

The entire history of the universe is just laid out before us. Which is amazing. And for for we're just getting started. We've mapped less than 3% of all the stars in the Milky Way. We've mapped less than 1% of all the galaxies in the observable universe.

We have not pushed into the cosmic dawn to the birth of the first stars and galaxies. We have not pushed beyond the Cosmic Microwave Background into the neutrinos and the gravitational waves left over from the big bang. We've accumulated some pretty impressive records, but we've got a lot of work to do. Thank you to Ralph for the question that led to today's episode, and thank you, of course, to all my top Patreon all my Patreon contributors. All of you.

I love all of you. That's patreon.com/pmsetter. I'd especially like to thank my top contributors this month. They are Justin g, Chris l, Barbara k, Alberto m, Duncan m, Corey d, Tom g, Nyla, John s, Joshua, Scott m, Rob h, Lewis m, John w, Alexis, Gilbert m, David l, Rob w, Valerie h, Demetrius j, Jules r, Mike g, Jim l Scott, j Lewis, I, Peter e, David s, Paul l, John Boy, and Scott r. It is all those contributions and so many more that keep this show running.

I can't thank you enough. Please keep the questions coming. Askaspaceman@gmail.com or just the website, askaspaceman.com, and I will see you next time for more complete knowledge of time and space.

Comment