Your wife laughing at the 'bald' question was just the best. (from a fellow baldie)

I think it's great that we are probing the universe for aliens. Personally, I'm tired of aliens doing all the probing.

Great vids, Fraser. I just discovered them a couple of weeks ago and been binge watching them ever since. But I recognized you because someone subscribed me to your old, plain text emails you used to send out like 20 years ago! Back then I used to print them out to prove to my friends how nerdy I was because I thought the info was so interesting. It's great to see UT has come so far. Keep doing what you love, man.

Another particularly good Q&A segment, Fraser. Thanks so much for sharing. Steve

If the aliens are hostile it is too late. Actually that raises the question, why not sterilize every planet in the galaxy instead of waiting for competitors to develop radio, probably a century or two before we get interstellar spaceships?

Your Question Shows have just made me realise something - I have learned so much from this Channel and from Astronomy Cast with Dr Pamela Gay that to me at this point giving answers is easier than asking questions - the questions I have now cannot be answered because the actual hardware and research has problems keeping up with you :)

Good choice with the head shave. Looks so much better than a comb over!

I often fall asleep to interesting shows. I can't sleep at all when crap is on! ;) I remember Hyakutake really, really well. Amazing sight!

Hi Fraser. I'd love to hear you speak about the properties of the vacuum of space (i.e. how many atoms are in a cubic meter in galactic space as opposed to intergalactic space). The idea that the vacuum of space isn't truly empty fascinates me. Great channel!

Glad you were able to see it. Glad the clouds didn't obstruct your view. Love your vids Fraser. Keep up the wonderful work that inspires us and keeps us all thinking!

Thank you so much for answering. The sheer fact that you did on top of that exciting info had me giddy. Again, thank you. 😊

Love your videos thanks so much for the opportunity to watch the videos you make , I am learning so much keep it up.I am hoping that some day in the near future i will be in a better position to become patron!!! Thanks again

I always thought it was a bad idea to advertise out into the universe that we exist and where we are, because you just don't know what other intelligent advanced beings are out there, some could look at us like how a lot of us look at animals, and farm us and keep us as livestock for food, others might want to torture us for fun, experiment on us for the greater good, whatever, who knows what mindsets other beings could have. But you make a great point that surely if they're intelligent and advanced enough to be able to decipher the plaque, gold record, and make their way over to us, then they would be intelligent and advanced enough to already know we exist and where we are without finding Voyager.

I've fallen asleep to Pamela's gorgeous, soothing, voice SO many times. And yeah, yours is ok too. I guess ;) I always listen again when I'm conscious though, promise :D

Holy cow. I am my friends started out with the plan of going to Carbondale. We looked at the weather that morning, and decided our best bet was to go into Kentucky. We ended up in the little town of Marion, Kentucky. This proved to be a great bet. We had a beautiful clear skies. Our plans for 2024 are already beginning.

Can't wait for astronomy cast start new season! I've been falling asleep to issac arthur's video this summer.

...your absolutely wright Fraser ...I was watching the sky 20+ years ago and I remember the comet was almost covering the whole ,,ceiling" ...from horizon...to the other horizon....that was a fantastic ,,picture"....I wish in my lifetime see again something similar to that......magic

Aw man, that's a shame about the cloud cover : ( That was my biggest fear after driving 800 miles to see it. It was partly cloudy all day and i was watching the sky like a hawk, thinking "we go that way if we need to!". All of the sudden, 10 minutes before totality, the entire sky cleared around the sun in every direction. It was incredible, man.

Truly amazing the power of a telescope/sensor that can analyze the light reflected off an exomoon and determine the distribution of seas and continents of the world it orbits.

Fraser, I'm new to your channel, and have a quick question: you and Isaac Arthur talk a lot about the Fermi paradox, but what about a reverse Fermi? As in, if another civilization is out there, what are the conditions required to actually detect it, given our current technology and understanding of physics? How do these detection methods change based on the development and distance of that civilization? Am I correct in believing that, unless we were close enough to pick up our own radio signals, we wouldn't be able to detect ourselves? Sorry if you've already covered this; I'm still digging through your library. But it's something that causes a lot of confusion when it comes to Fermi discussions. I also don't understand the incentive to become a K2 civ, especially since population growth tends to level off as technology and standards of living improve, and don't understand why the Kardaschev scale is so often taken as a given. I'm missing a core element of the philosophy. Thank you for your fantastic content.

Hey Fraser, thanks for answering my quastion!

Question: UY Scuti has the largest radius of any known star but is only 11 solar masses. What decides the density of a star, besides their stage in life? Why is there no larger red supergiant with say 20 solar masses?

Hi Frasier, I'm new to your channel and I've enjoyed watching your videos. So far, I like your Jean-Luc Picard answer the best, it was awesome.

The thing I would like to see in my lifetime is a supernova, naked eye. I hear Betelgeus is ready to pop.

Hi Fraser, I have a question - sort of a rehash of a question already asked. It's about time dilation and gravity wells. You answered this recently but .... sorry ..... not really to my satisfaction bro :) We know that the deeper one gets inside any sort of gravity well the more slowly time passes, right? GPS satellites correct their clocks daily to compensate for the difference in time out there, right? Well, when the other user asked you about inter-galactic space and how time 'flows' out there away from any large gravitational source I got the feeling they were curious about the 'natural' flow of time. Our units for measuring time are quite arbitrary, mostly based upon the rotation and orbit of Earth but ok, let's just take a second at sea level as the standard unit of time - a tick or a tock. What I'd like to know is ...... what would be the length of a 'second' out there in inter-galactic space compared to our standard unit? 0.75 of our second? 0.8? There's has to be a natural time unit, right? I mean, we can't really say that the rate at which time passes is 'universal', can we? Because it depends on whether or not you're inside a gravity well and how far inside it you happen to be. However ... there ought to be places in the universe where gravity has such little effect that the passage of time is .... natural, unaffected by gravity. places where the flow of time would be constant and somewhat universal. This is quite different from relativistic time dilation too, isn't it? Time dilation as we usually know it is due to velocity and not gravity so I guess the ultimate question here then is .... how does time flow when you're not moving at all and there's nothing near you to create gravity? Cheers! edit: by the way, _if_ governments really did have alien tech why would they keep it in some desert facility here on Earth? I mean it stands to reason that the one thing they'd want more than anything, if alien contact had been made, would be their means of propulsion and once you had that you've no longer any need to remain here on Earth. Once you've got the propulsion you can go wherever you like, cart around as much building material as you like, plug up a large asteroid maybe and stick your space program in that. It would be a lot easier to keep a secret space program secret if it were off-planet, wouldn't it? If the people involved in it aren't here on Earth then they can't betray the secret, can they? Just some food for thought there bro :D

I favorited this video due to your first answer, the one about math!

I always wondered if you could reasonably detect the polarization of light reflected off surface water of exoplanets.

You suggested Astronomy cast to me not long ago and i found it very hypnotizing. Great content, especially reviews on all the sci-fi books you guys read. But yes, I fell asleep. WARNING: dont fall asleep on your computer chair!

Thanks for the great show, could've mentioned that reaction wheels can saturate on use in addition to breaking. Also the different versions of evolution is a bit peculiar way of saying convergent evolution. It's not different kind of evolution, it's the same laws creating similar solutions without being genetically related. Since evolution tends to go similar routes without apparent family ties, it's fair to assume that planet with similar characteristics to earth would also have very similar flora and fauna.

Another question about the ''star shot''. These probes will be travelling at say 10 to 20 % of the speed of light so will there be a kind of ''red shift'' in the radio waves that will be transmitted from the space craft? Will this ''red shift'' be enough to make communication difficult?

Wish I could hit a like button, when I learn something off each these different answers. Lovin the shows..

Reaction wheels seem like they would be incredibly simple pieces of equipment consisting of a weight (which can’t really fail) and an electric motor (which are very reliable on earth). What causes them to fail in space? Also, on the question of what life would look like on other planets, in addition to chance, it would totally depend on the physical conditions on that planet (atmospheric pressure and content or strength of gravity, for example). If gravity were fairly low, there could be giant animals. If the oxygen content were really high, you could see giant insect-like creatures (as we did on earth when oxygen content was really high).

I'm going to assume a Hubble constant of 71 km/sec/Mpc because you get the accepted value for the age of the universe from its reciprocal, which is 4.346e+17 sec, or 13.77 billion years. Let's say that you observe something at the edge of the observable universe. You know that it was 13.77 billion light years distant 13.77 billion years ago. When you correct its position for the expansion of space, how far away is it now? This is an integral problem, since the expansion of space itself increases with increasing distance, and the recession speed that the expansion of space causes is not limited to the speed of light. We will walk the distant object forward in time by a (relatively) small increment, e.g., 100 years, and assume that the recession speed was constant over that little bit of time. We find out where it was a hundred years after we saw it. We compute a new recession speed based on the Hubble constant: 71 km/sec/Mpc. We compute a new distance, when the object was two hundred years after we saw it, based on that recession speed. Rinse and repeat, until the accumulated amount of time reaches 13.77 billion years. With a 100 year time increment, the final (corrected) distance is 37.426062 billion years, and the final (corrected) recession speed is 2.7176023 c. With a 1000 year time increment, the final (corrected) distance is 37.426061 billion years, and the final (corrected) recession speed is 2.7176022 c. You can see that the integration almost converges when the time step is a thousand years, so there isn't any reason for me to belabor my computer with finding solutions with time-steps smaller than a century. An even more interesting question is: How far away would a galaxy have to be observed by us today in order to have a corrected distance of 13.77 billion years, and therefore be on our cosmological horizon right now? I did the math. It turns out that a galaxy that we observe as being 7.8105394 billion light years from Earth, and having an observed recession speed of 0.56714329 c, has a corrected distance of 13.771721 billion years and a corrected recession speed of 1.0000000 c. It would serve no purpose for us to send any intergalactic spaceships to chase after galaxies farther away than 7.81 billion light years because they'd never catch up with the galaxies they were chasing. Not even if they could accelerate to within a cat's whisker of the speed of light. We can observe a very large number of galaxies that are, already, over the cosmological horizon and lost to us. Here's the Python code. When copying the code, if you do, replace any underscores with spaces. import math pi= 3.141592653589793238462643 # conversion: seconds per year k1= 3.15576e+7 # conversion: meters per light year k2= 9.4607304725808e+15 # speed of light in m sec⁻¹ c = 299792458.0 # Hubble constant in sec⁻¹ = 71 km/sec/Mpc H = 2.3009532955054991665e-18 # Observed distance (where it was), LY y = 7.810539401e9 # Observed distance (where it was), meters d = y*k2 # time step in years dt= 100.0 # time counter, years t = 0 # initial recession speed, m sec⁻¹ v = d*H # output initial state print(d/k2,v/c) # integration loop while t

Is a swing by therotical possible at a black hole and how much speed could it add if so?

Hi Fraser, my question is it possible that dark matter has gotten trapped down in Earths gravity well and takes up a probably very very small amount of Earths mass?, if so how small or large is it? Or will we never know. Another question is could pockets of dark matter mess up a trajectory of a spacecraft during a interstellar journey?, is their anyway of detecting these if their are any?

Can telescopes detect objects in space obscured by other, closer objects in their line of sight/signal and, if so, how?

Hey Fraser, when does the Weekly Space Hangout return? You've probably said it but I missed it. Thanks

If the Arecebo radio telescope was at Proxima Centauri could it detect radio broadcasts from the earth? how about the square kilometer array?

Hi Fraser! Can you explain if the Neutrino is smaller then the Electron? Also, Is there a place in the universe that's at Absolute Zero Kelvin (-273.15 Celsius) or below. If not, what's the coldest we've measured?

I've got a question: why it is believed that water is necessary for ANY (i.e. alien) life to evolve?

I read once years ago in community college that the 4 forces were once one force near the beginning of the universe and seperated when the universe cooled, could you shed some light on this please? Love your videos btw

Question: Regarding binary/pinwheel WR-104 do we know yet if the GRB jets will be pointed at us? I haven't seen news of it for a while, but IIRC it could blast our southern hemisphere.. whenever soon by star standards. Keep your sunblock handy!

I think a great way to look at the evolution on a different planet say compared to earth would be using Australia as an example...sure its on the same planet but Australia separated from Gondwana about 180 million years ago. Marsupials which are believed to have evolved during the Cretaceous solve a lot of the same evolutionary challenges with end results that look VERY much like their mammal equivalents. A great example of this is the Tasmanian Tiger (Thylacine) that went extinct in the 1930s. It was an apex predator like the mammalian wolves/tigers etc and looked similar but had a lot of unique characteristics. I think it would be like that on other planets given variables close to earth. The closer the more earthlike the results etc. If you take a look at the skeleton of one of these compared to a timber wolf its scary how similar they are but thats due to evolution due to similar challenges/pressures.

Terrific video. Regarding aliens knowing we are here, and attacking us, I would doubt that we have anything to worry about. My guess is that if a civilization has the capability to transverse the stars, they have already passed through one or more “great filters”, including the violent, aggressive filter we are (and have been) in. In other words, I would bet that an advanced civilization would have evolved out of their aggressive phase.

I have heard a lot about missing anti-matter in proportion to matter. Would anti-matter have an opposite lightcone from matter if observed from the big bang?

If stars in a region of the Milky Way were dimmer on average compared to the surrounding region, how much dimming would be noticeable? Also, how big would this region need to be for the effect to be noticeable - 8 degrees across? 16 degrees? 90 degrees?

Starshot initiative will pass across oort cloud. There are serious chances of It coliding against any object there? And why sending the ''starship'' across the cloud? Wouldn't be safer to send It perpendicularly to solar system to avoid objects?

Fraser, you mentioned we will have telescopes which will be able to peer through to the edge of the observable universe, can you speculate what we might be able to see, and would there be images or just data? Thank you

we went to Tennessee to see the eclipse, west of Nashville. We lucked out and the clouds went away in time for totality. We drove over 10 hours.

1:39 Them birds just want to be in your video..

Is it possible that when you get to the singularity of a Black Hole, time actually reverses itself (going off the theory that going faster than the speed of light reverses time, or something similar) and that if all the Black Holes in the universe come together they either make an element so rare that it takes all of the protons, neutrons, and electrons in the universe to make that is also very radioactive and decays, making a new Big Bang. Or would it just rewind time for all the objects in the universe, because it is all the objects of the universe, then explodes for some reason or another, like an implosion/explosion grenade over and over again? (Sorry if this didn't make much sense, I'm very tired)

Mr. Cain will it be possible to determine if an exoplanet has a magnetosphere?

Ok here's a hard one. If a cosmonaut can go inside a super massive black hole a live, would we be able to send an instrument, say a 5k mile long that is measuring every second and moment of itself and its surroundings... Since an astronauts is OK wouldn't said instrument be able to send information from inside the black hole from the parts not inside of it?

If humanity becomes a primarily space faring species, do you think we will still use seconds as our unit of time considering it is completely related to the time on earth. And how would days/months work for an interplanetary species?

I was in Carbondale (nearby Pomona actually) at a friend's house. We saw the entire eclipse from beginning to end. I tweeted Pamela to see if there was anything public going on. In 2024, you and Pamela are invited to join us at the same location.

Fraser, if a rogue planet was to approach our solar system how soon could we detect it and would it likely settle in orbit or.....?

A recent study indicates that only a small % of earth-like planets are visible to earth or any other planet with current methods due to off-ecliptic alignment of most planets. The futility of hiding may rest on invalid assumptions.

A fantastic show. Very interesting. Thanks.

Your are right, Frasier. They have known life is here for millions of years. Now - we are just being observed...

Ok question, why is the moon eventually going to break free of the Earth's gravity well, while other moons like Mars's are eventually gonna crash inwards?

Any thoughts on The Three Body Problem by Liu Ci Cin?

Was there in Carbondale also. Was an interesting event. Just like how you described, one small spot of the stadium, going up in cheers as one ray of light comes and swept across them moments before C2. It was infectious, getting the whole crowd going and just a peek to totality and the corona. The last moments of totality I could see prominences on the solar limb. What a moving experience. I'm disappointed that the weather wasn't perfect for it, but I saw enough to enjoy it, and that environment was very interesting also. Here's to 2024.

Why is the speed of light so slow? What's holding it back?

I have a question for you, can you escape a black hole with a warp drive?

Glad you enjoyed the eclipse. 1:45 "Anything better than math ... to understand the universe" Well, physics, and science more generally. But I suspect that's not in keeping with what your questioner meant and won't satisfy him. My answer would be to explain what math is, from which it follows that there are no sensible substitutes for it. Math is just the study of absolute truths, truths that we can know without using physical experiments or observations. If you had some other real way of studying absolute truths, well, it would *be* math. For instance, when Kurt Goedel broke new ground with his undecidability proof, or when Georg Cantor did the same for infinities, those new methods were immediately recognized to be mathematical, though they had never been seen before. You could make a similar argument for the uniqueness of science - if something else made reliable predictions about the world as a consequence of repeatable experiments and observations, that thing would be science.

Physics has a measurement unit for everything in the universe but doesn't seem to have one for rate of flow of time. 1 earth sec is 1 sec on surface of the earth but how do we define 1 sec on the surface of a jupiter-size exoplanet or at the surface of star? Also, what could be the fastest possible flow of time in the universe and how much would that be compared to earth time?

Can you please do a video with Isaac about Kepler, its catalogue, and a special focus on TESS, and its upcoming catalogue, and the potential implications? Keppler proved to us that there is a great population of planets in our galaxy, but imagine how amazing it will be to truly take measure of their number? That's why TESS is my #1 favorite future space mission!

What are your current thoughts on space innovation such as space x versus NASA?

Would it be possible to have non-mechanic reaction wheels by pumping lots of electrons thru a huge coil? How much of the weight of copper wires is composed of electrons?

Hi Fraser,Could there be another solar system closer that alpha Centauri?I mean have they looked in every single direction 4 light years.

Question: after recently watching the amazing documentary Farthest it got me thinking, do you ever get upset that you will miss all the future space discoveries and achievements that humans will accomplish past your lifetime

Question: Here's the experiment, 2 atomic clocks, one placed inside a bubble, and that bubble inside a hollow spherical shell filled with superfluid helium. What happens if we use a magnetic field to spin the helium up to high speeds? Will the stationary clock in the middle of the high speed fluid read the same as the other, or will it read slower?

Solar eclipse was great to see, but it was also very disappointing. I went to an area with 95-95% totality and it just looked like a cloudy day with a strange grey haze for less than two minutes.

Q: what do you think about the movie life?

One thing that's bugged me, is that seti has a requirement of having a repetition of a signal, yet humans have never repeated a signal to potential aliens.

Star Shot Daisy Chain: If the Daisies are launched every couple of minutes how is each one going to be accelerated to 0.1c? Presumably they don't go from 0 to 30 000 km/s in 2 minutes. Or do they?

If we see an object 13.7 billion light years away, we must have been much closer to that object when the light left it, as the entire universe was much smaller then. Have the photons currently reaching us been chasing us for 13.7 billion years as we move away at just under the speed of light relative to that object? Not far behind but slowly creeping infinitesimally closer? If so how can they hit us at the speed of light when they've spent the last 13.7 billion years travelling at only just above zero speed relative to us?

13:21 well, that was a *bold* question!

Fraser Cain, the best way to describe the universe is interpretive dance! :-)

Well I for once avoid your videos before sleep. Sometimes it's 3 am on a workday and I'm rewatching old episodes.

Quick question, I can't really find a good video about how planets get an athmosphere, so how?

Hey farser, i've got a question Based on the size of the observable universe, do we know the rate of expansion of the universe? And is it the same on every side?

Do you have a powerful amateur telescope? If yes, what's the smallest extraterrestrial object you've seen?

Hi @Fraser Cain ! I have a Schmidt-Newton telescope with 950mm focal length, 200mm mirror diameter, and a light polluted place, but stars are visible with naked eye. Currently (and for a long time) I don't have vehicle to transport it. Is it worth assembling here? What should I watch with it?

Love your show great job keep it up 😃

If we know how old the universe is and how fast its expanding, then how is there any question about its size? Surely it's just a matter of simple maths and yet we still don't know how big the universe is? Some say it's infinite?

Hello i wanted to ask you something, in end of juno mission the spacecraft is going to be crashed into the Jupiter why?

You are showing your youth, I saw comet hyakutake in New York City, Yes it was fully viewable in Queens. It was great I could only imagine seeing it in a dark location. As for 2024 we live in Buffalo now, come visit great location, rain shadow from Lake Erie.

I always wondered what's the point of looking for extraterrestrial life in other star systems if we won't be able to directly study or interact with them for at least hundreds of years. And if we ever find an inhabited planet we would never be able to reach it in our lifetime.

Please answer my question, why do human want to know if alien is still exist, and what is the point doing it?

In case of quasars, what would happen if regular matter was replaced with dark matter only? Would our equipment be able to detect the effects, if so, would we be able to tell the difference? Thanks, love the show!

Great video! Keep it up!

What is your favorite deep space object, and why does it intrigue you as much as it does? The deep space object I particularly enjoy M43. It was the first nebulae I viewed through my telescope, and the proximity to Orion constellation makes it very convenient to find. Nowadays, I enjoy solar viewing and planetary viewing while attempting to take nice pictures in my attempt of astrophotography.

Using the Swartzchild Theory and the information from man made dumb holes, could we not theoretically create a black hole; and what are the pros and cons of doing so?

Subtitles are not active, even the auto generated ones.

Q: So, the giant gas planets does produce a tremendous radiation. Is it possible for life to happen for example on Titan or Europa?

I have a question. Why isn’t there a way to fuel/ power rocket engines with just solar energy. Of course they will have to be massive but don’t you think it’s good? Earth will be out of fuels eventually so either we leave now or we might not be able to at all

Sci-Fi often has people blowing up stars but are there any realistic theoretical ways to blow up a star that could actually be built in the next century or so?

How are Quasars and Hawking radiation possible if light can't even escape black holes? Aren't those things 'coming out' of a black hole?

Even if the aliens are hostile, it's a good idea to contact them. Better be them destroying us than doing it ourselves.