Surviving Sun's Red Giant Phase, True Color of Sunspots, Identifying Interstellar Objects | Q&A 214

How many stars did our radio signals reach? How to visualize the expansion of the Universe? Can we save the Earth from the Sun's red giant phase? How can we tell that an object has interstellar origin? All this and more in this week's Q&A!
🦄 Support us on Patreon:
/ universetoday
00:00 Start
01:02 [Tatooine] If the Sun is white, are sunspots really black?
05:19 [Coruscant] How many stars did our radio signals reach?
08:51 [Hoth] How do gravitational assists work?
11:43 [Naboo] How to visualize the expansion of the Universe?
13:35 [Kamino] How will the Mars sample return mission find all the dropped tubes?
16:27 [Bespin] Can Earth survive the Red Giant phase of the Sun?
20:16 [Mustafar] What effect will a supernova have on nearby stars?
21:51 [Alderaan] Should the US continue to explore space?
24:16 [Dagobah] Can we time travel with a wormhole?
26:59 [Yavin] What killed the Chinese Mars rover?
29:32 [Mandalore] How does light pollution work?
33:04 [Geonosis] How can we tell that an object is interstellar?
📰 EMAIL NEWSLETTER
Read by 60,000 people every Friday. Written by Fraser. No ads.
Subscribe Free: universetoday.com/newsletter
🎧 PODCASTS
Universe Today: universetoday.fireside.fm/
Weekly Space Hangout: / @weeklyspacehangout
Astronomy Cast: www.astronomycast.com/
🤳 OTHER SOCIAL MEDIA
Twitter: / fcain
Twitter: / universetoday
Facebook: / universetoday
Instagram: / universetoday
📩 CONTACT FRASER
[e-mail]
⚖️ LICENSE
Creative Commons Attribution 4.0 International (CC BY 4.0)
You are free to use my work for any purpose you like, just mention me as the source and link back to this video.

[@7heHorror]

Bespin! Love that answer. A precarious project of course because 10k years is long enough for Earthlings to forget about the massive asteroids we sent hurtling towards us.

[@hikingpete]

Regarding gravitational slingshots, the explanation that helped me involves imagining Jupiter as a large truck on the highway, and the probe as a bouncy ball flung towards the truck.

[@luciobaggio8695]

Precisely, it is just an instance of elastic scattering. With a high enough mass difference, the small object bounce back with same absolute speed in the center of mass reference frame. So if the c. of m. is moving relative to the solar system, the final speed is twice the planet speed (plus the probe speed).

[@christopherblare6414]

Degobah - one thing to note about wormhole based time machines, they can't travel back farther than when they were created. So unless someone already has one, there is no way you can go back before now.

[@PinataOblongata]

I have to admit, I didn't realise that I didn't really understand slingshots as well as I thought when I watched the explanation for the Hoth question, but it seems obvious now that you've explained it. Feels good knowing I understand it better, now :)

[@cacogenicist]

If you're a multi-million year old civilization, you definitely would not move Earth -- you would lift mass off the sun to extend its life. You could use that mass for all sorts of things, like improving your (long since built out) Dyson swarm -- or if you've been lazy and haven't gotten to it yet, building your Matrioshka brain.

[@universemaps]

Great episode of q&a! The volume is a bit lower than usual... I love this channel's usual compressed high audio levels because I can listen with my phone without headphones.

[@frasercain]

Yeah, we forgot to run one audio pass on it that we normally do.

[@Dick_Gozinya]

5:20 Well, we know our TV broadcasts will reach Omicron Persei 8 around 1000 years from now.

[@arnelilleseter4755]

I'm amazed at how many people question why we should explore space or why we should spend money on the Large Hadron Collider, it has no real value. I use to respond with "Why should we bother with music or movies. We can't eat it." By exploring the universe and doing experiments we can learn some things that will benefit people in a tangible way. But even if we don't, exploration and the search for knowledge has value in itself.

[@boredgrass]

Alderaan! A Two part comment: 1. Dear commander Woolf, it is not only a great question but I also love that you made the effort of asking and had the courage to ask., never ever stop asking! I am deeply impressed! 2. For Frazer: When people build something magnificent there comes a moment when everything comes together and it becomes visible what it is all about. For me that moment came in Commander Woolf's question and your answer! It moved me.

[@chrisgriffith1573]

Always a pleasure listening to your videos, so many things to ponder and comment on, I love hearing your angle about what is going on today!

[@kevinlindstrom6752]

Bespin. I don't know if it's the best question but it certainly is the best answer. That is fantastic.

[@MCsCreations]

Thanks for all the work, Fraser! 😊 Stay safe there with your family! 🖖😊

[@disinclinedto-state9485]

Hey Fraser, great show as always. How do astronomers confirm/ensure that an "interstellar object" was not a solar object that had a funky gravitational interaction to get kicked into escape velocity?

[@nilayvyas4662]

Bespin - It was hard to pick the best. Great questions and answers! Thank you!

[@ayoung7811]

What a fabulous presentation. I have subscribed for months (Not a Patrion yet), and am suprised at how much I have learned today. Thank you for your work.

[@unruffledaria9643]

Bespin, best ever geoengineering concept I've ever heard!

[@MaxBrix]

The trick to gravitational assist it to approach the planet from behind as it orbits the sun. The planet pulls you away from the sun and in the direction it orbits. Since it is moving away as you fall the interaction takes longer and imparts extra energy. Then you leave the gravitational well of the planet as fast as possible away from the orbital direction of the planet.

[@MaxBrix]

A simpler way to see it is if you pass behind a planet it slows down. if you pass in front of a planet the planet speeds up. The opposite happens to your space craft.

[@918Boyz]

p0

[@joesalinasjr5225]

Fraser, your program are outstanding. I have learned so much from watching your videos. I supported your programs on Patreon at the $10.00 level for some time. But now my finances have changed. I am retired, but I still love your programs. So I continue to watch on KZbin. Thank you for all you do.

[@frasercain]

Thanks for all your support Joe. Don't worry about funding us, that's totally voluntary. And remember, you've still got the ad-free edition of UT available for life.

[@XFourty7]

26:37 Indeed! I was thinking about the SG1 episode with Wayne Brady last night, gotta rewatch that one soon. :P

[@SomeMadRandomPerson]

Some nice questions in this week, my favourite was Coruscant.

[@nickmorgan5144]

Bespin. Beautiful answer, and a beautiful solution to a hard problem. I have a question regarding this topic - how far away do you think we are from being able to start this process? It would seem that we are on the verge of having this capability, but maybe I am missing something?

[@CarFreeSegnitz]

We have the capability right now. What’s missing is the urgency. Earth will be able to support life for hundreds of millions of years yet before the sun makes it impossible. Optimistically humanity will be around for two million years. We could do our successors a favour by setting up the Earth-moving scheme. Or trust our successors are going to be capable of doing it themselves without our help.

[@ashleyobrien4937]

If you want to get E.T's attention, the best way, by far, is to simply send up into solar orbit a number of very high yield thermonuclear warheads, and detonate them in a time sync'd sequence up to the number ten, so for example , set off one, then after a unit amount of time, set of two in sequence, then wait a unit amount of time, then set off three in sequence, wait a unit amount of time, then set off four in sequence and so on. This will create a multispectral emission of our base ten decimal system, a simple mathematical progression that would be unmistakable as a sign of intelligence, and also it would carry a far higher chance of being detected because of it's wide energy spread across the E.M spectrum. At least, that's how I would do it, if I wanted to say "hello"

[@kaitlynlsari681]

A.c. Clarke used the idea of the gigaton bomb in one of his novels as a way to pinpoint and locate all of the asteroids in our solar system. In the novel, an alien civilization detonates one in its solar system not long after the energy pulse reaches it like they were waiting for someone to send a signal like that so yeah someone's thought of it before and it might work

[@ukraine7249]

Set fires on the moon?

[@Seadalgo]

The residual plutonium alone would be a sign of Intel life when viewed through a spectrograph

[@CarFreeSegnitz]

The yield you’d need! Our sun puts out millions of times the yield of the Czar Bomba… continuously. You’d need bonkers enhanced gigaton bombs to get the signal to rise above our sun’s noise. If it were up to me I’d do giant geometric sun shades. ETs’ Kepler telescope would see impossible dimming that would suggest a planet that weighed nothing but was some multiple of the diameter of the sun. That would get their attention enough to aim their JWST at us. Then they’d see a pentagon or triangle shade, unmistakably artificial. The observation window for shades is far longer than bomb signals. And the shade could do duty for humanity as a solar energy collector.

[@nathanegbert977]

Setting off 63 thermonuclear warheads is a heck of way to say "hello"

[@junkmail4613]

4:22 How about getting a half inch diameter "dental mirror," put it on the ground in a little movable vice, and reflect it against a white wall, in a shadowed area about 30 to 80 feet away. the image you see on the wall, is as if the sunlight passed through a pinhole the size of the mirror. Maybe a half inch in diameter. Would work fine above that cabinet behind your head (against the wall). I did this during a solar eclipse at work and the 25 to 30 people working in the electronics manufacturing lab could watch the whole eclipse live, (as long as I went outside each half hour, and re aligned the small dental mirror)

[@1000dots]

Easily my favourite channel

[@redcirclesilverx4586]

Kamino shoots i hope we can get actual pick up and launch streams

[@magiegainey5036]

Tatooine- Great video. Thank you for your hard work!

[@KaktitsMartins]

10'000 stars within 100ly radius?? Thats way more than i imagined!

[@peterkallend5012]

Use a reflector telescope as your projector. Use a pinhole camera, those work wonderfully. Both help view the sun without damaging equipment or eyes.

[@michaelallen2971]

The video creator is wrong. There are filters you can buy for your telescope that allow safe and direct viewing of the sun. They are called white light filters or sometimes known as aperture filters.

[@asafoster7954]

​@@michaelallen2971 the video creator wasn't wrong lol

[@peterkallend5012]

@@michaelallen2971 yes, there are. I've used them to do a solar declination for M2 aiming circles in Iraq so we could more accurately lay our mortars in for indirect fire support missions. My comment was specifically intended as a solution to prevent melting the internal components of a telescope, which those filters don't actually do. Besides, using those filters restricts the number of people that can observe at one time. Using a projected image can increase participation in that regard.

[@bassangler73]

@@michaelallen2971 true, the Mylar versions are under $50 for a 6" or less aperture but I have found that the ones made of glass do a much better job because they are not a wrinkled piece of Mylar that is next to impossible to clean...I dont think Fraser was wrong, he just was probably trying to show people an inexpensive way to view the sun...

[@michaelallen2971]

​@@bassangler73 he didn't. He just said don't do it you can't do it.

[@jupiter604]

Thanks Fraser.. I liked the Dagobah question

[@ProfessorMAG]

The way I visualize the "expanding universe" is to imagine everything "shrinking" but remaining in the same location. With spacetime "shrinking" or "compressing" the time component is slowing down too, so light takes longer to travel the relative distances. Its all a mater of the reference frame you choose. Perhaps like the inside of a black hole?

[@chrisgriffith1573]

One thing nobody really talks about/seems to consider in calculations regarding The Fermi Paradox is time dilatation for the inhabitants of any world that may be out there and how this affects their development/lifecycle/interactions in reference to our time frame and our interactions- their "radio signals" or their communications might be so very different to our that we may not know them as anything we can identify. In addition, this difference might make preclude them from evolving as fast if their gravity well is shallow. Time would make their environment far harder to evolve within, slower means we have come out far faster than anything else- and they have far more opportunities for asteroids to wipe them out before they get a chance.

[@dwayne_draws]

Bespin. Great question and great answer.

[@terryharding4185]

Another great batch of questions. I'll have to go Hoth this time

[@charleslivingston2256]

Loved the answer to Hoth

[@kd7jhd]

Thanks for another great show. I really like your background music. Are you will and able to share where I can listen to it myself?

[@brainbark]

Hoth! Another great show, thanks.

[@tryhardfpv5351]

The down draft from the drones propellers will blow the dust away from the samples. Hover over them until cleared enough to pickup.

[@CarFreeSegnitz]

9:51 “… if Jupiter was just sitting there… it would net out to zero…” Agreed that the craft wouldn’t get an assist with respect to another body (the sun) but there is a significant effect on its path. If the pass was close enough the encounter could almost completely reverse the course of the spacecraft. And the lone rogue Jupiter would take almost twice the craft’s momentum to start moving ever-so-slowly in the opposite direction of the craft’s new path.

[@eneslem]

Hey Fraser, If I was standing on one of the moons of Jupiter, how bright would Jupiter appear to me? Is there enough sunlight to make it bright enough to make it appear like in the pictures, or are those pictures long exposure, and Jupiter would appear really dim to the eye? What about really far away plants like Neptune?

[@TraditionalAnglican]

Alderaan - I don’t think people realize how many things we rely on were invented, developed & deployed as a result of the space program in the 1960’s. I also don’t think they have any idea just how necessary “Frontiers” and new horizons are to human development.

[@thedenial]

Kamino: Since the sample recovery helicopters are only a backup I was curious if they'd be useful either way after the return rocket is launched, NASA states "Scientists are currently investigating other potential science or exploration uses for the helicopters following the completion of the Mars Sample Return effort." so hopefully we'll get to see them in action.

[@istvansipos9940]

11:52 I think you possibly missed his real issue, Fraser. The flatness. He asked how a 3d something (our universe) could be "flat". I'm afraid, the well explained 3d grid won't clarify that.

[@jensphiliphohmann1876]

About 12:20: ▪︎The balloon analogy is confusing in another way: By inflating the balloon, you enlarge everything in proportion. If this happened to the universe, we wouldn't notice any expansion. ▪︎About the universe being flat: The entire universe doesn't even have to be flat but could also have an enormous radius of curvature. Additionally, what we see is actually the past light cone, and a cone mantle is naturally flat except of its pointwhich actually is your eye. ▪︎About the universe about being flat _and therefore infinite_ in space: A surface or a region being flat doesn't need to mean that it's infinite, at least not in all directions. A cylindrical mantle, e.g., is indeed flat in the inner geometrical sense though it's bent in 3D. You could could it parallel to its axis and roll it out on a table, and its geodesics if they go the same direction at any point do it everywhere.

[@krebonio]

Questions about Titan: would a lighter filled with air work the same way as a butane lighter does on earth? And for how long would a human survive on the surface of Titan wearing only heavy winter clothes and an oxigen mask?

[@kaitlynlsari681]

No. Fire needs oxygen no oxygen in titans atmosphere so you wouldn't even get a flicker because titans atmosphere is mainly nitrogen. And literally a few seconds. The good news is titans atmospheric pressure is 1.5 times earth's at sea level, the bad news is Titan is so cold that methane exists at the triple point there which means it can be solid ice, a liquid or a gas.its 179 degrees Celsius below zero or minus 292 Fahrenheit. Yould be frozen dead in seconds without a special thermal suit that was contained

[@krebonio]

@@kaitlynlsari681 my dude, titans atmosphere is the fuel (methane/ethane mixed with nitrogen), the lighters got the oxygen and spark. Would it flame up?

[@bjornfeuerbacher5514]

I vividly remember a crackpot with whom I tried to discuss lots of years ago. He insisted that because the sunspots look black, this has to mean that these are holes in the atmosphere of the sun, and we can see the interior of the sun, and the interior "obviously" is metallic hydrogen, i. e. a fluid or even a solid. :D

[@bludragonproject9677]

In regardes to Bespin, read the book Cities In Flight by James Blish. By the way great channel, always enjoy it!

[@j7ndominica051]

The radio transmissions would all be jammed up if you could receive all of them simultaneously, like if you listen to medium wave at night. that'll take some crazy math to make an asteroid go from Jupiter to Earth repeatedly many times. I am also confused by gravity assists, and I like your explanation.

[@ColCurtis]

With an asteroid gravity assist earth would only slow down on its apoapsis, at the opposite side of its orbit from the speed assist, but earth would be accelerated during the interaction with the asteroid at its periapsis. Earth would then need another gravity assist at its new apoapsis to bring up the periapsis into a circular orbit by increasing the speed of earth again during the asteroid interaction.

[@bassangler73]

Corncerning the dust problem on Mars Rovers, has any space agency tried a system such as on a digital camera sensor that shakes the solar panels with micro vibrations to remove the dust?

[@eamonia]

Dude, you're so freaking cool. Rock on.

[@theoptimisticskeptic]

Bespin: I'd love to be around to if we're still around and to see how humanity deals with the 'Red Giant' problem.

[@user-pd8yl3ol2k]

Fraser Cain: Would it be possible to use the temperature and pressure differentials in the Venus atmosphere to generate power? I am thinking of an analog to geothermal power where you send a dirigible with log hoses that would dangle down into the hotter and denser atmosphere close to the surface. Add a couple of oneway valves and a sterling engine on one end, and you should be set. Is this defeated by material science concerns or weight limitations? Would we need to wait for graphene to make this viable, or are there other problems that I am not considering?

[@barnabuskey3956]

If you could be given all information you wish to know about everything in existence however the side effect is the more information you gain the quicker you expire. Based off this assumption how much information would you want? Wether the information is known or unknown doesn't matter.

[@jensphiliphohmann1876]

A question akin to BESPIN: ▪︎Were it theoretically possible to lift Venus that way up to Mars in order to collide those planets the same way as Proto-Earth collided with Theia in order to get a similar result? ▪︎Were this maneuver possible without colliding Venus with Earth?

[@dbaker059]

Question: What is the limit, ignoring lack of resources, with current building materials to the size of space ship or station that could be built before gravity started to deform the structure to a sphere? I'm thinking Death Star or Borg cube type structures Thanks

[@CarFreeSegnitz]

No real limit if you don’t mind slowly rotating the station/spaceship to counter the inward self-gravitation.

[@lawsongnosis]

Hoth! Also... If we ran out of fossil fuels tomorrow, how bad would this hurt our space game? Can we produce all of the chemical fuels we currently need using renewables?

[@cafaque]

Bespin

[@agentdarkboote]

Okay so dust in the center of our galaxy blocks visible light from the accretion disk of Sag A* from getting to our telescopes. But it's also not *that large* and it's incredibly far away. I'm wondering, if we sent a swarm of infra red telescopes to the solar gravitational lens, and also assuming starting at the sun isn't an issue for them at that distance, would they have enough resolution to get an image of Sag A*?

[@samson1200]

Couruscant. Is the a finite upper limit of satellites that can be in Earths Orbits that would interfere with launching or receiving human spaceships?

[@cantbesirius]

My answer for Alderaan that nobody asked for: same reason we fund the military, we don't want to be eliminated by an exterior threat. Humanity can't end with the sun or an asteroid. Could you imagine being that person watching the sun expand toward you thinking "wow wish my ancestors weren't selfish assholes". TIRED OF IT! lol

[@idodekkers9165]

Hey Fraser are there mathematical solutions for the location part of time travel? even if we figure out moving in time, since everything in the universe is moving, if we travel in time and not in space, the earth will not be here. I know that mathematically time travel is possible, but is this problem solved?

[@1milkmile]

hi Fraser, I saw the new image from JWST, the hot star Wolf-Rayet 124 and its mentioned that Wolf-Rayet is phase before going supernova. But for me it looks like a supernova. What's the difference?

[@Hovado_Lesni]

Hello Fraser. Well today on the way to work I was listening to science fiction as always and one thing came to mind. Highly altered people. Like augmented with microchips. They can think in milliseconds. For them, one second can last a long time. So, if they perceive time like this, won't they see everything dark? When I set the camera to 1/4000, which is 0.25ms, the day changes to darkness. There is simply not enough time for enough photons to hit the sensor. The same should happen with the eyes

[@simonjennings5458]

Question: we can fire objects at crazy speeds on earth using magnets but in a vacuum the speeds become crazy. is there anyway we could construct a giant electro magnetic tunnel in space and use it as a launch tube. thankyou for all your content i love it.

[@chrisgriffith1573]

Compressed gas. Make a compressor that gathers and condenses Martian atmosphere to use as a forceful power wash on a wiper that works to clear the solar panels. The panels would need a redesign to work with these "wipers" and the blasting they would receive. This would need to be a required energy calculation in the overall battery usage to power the compressor and wipers, but the return is continued function of the probe... I would also think that these new panels would have stronger (heavier) constructions, so to lighten the load and also increase strength, designers might use lenses which act as diffusers, and as tiny reinforcement arches, all designed with A.I. engineering programs, 3D printed using some of the new methods we have today... could be a game changer. The other factor might be anti static charging of the panels themselves, and use magnetic repulsion under or within the panels, perhaps a panel is not so much a panel, but a rod with a spinning magnetic motor that we can manipulate for repelling the dust itself.

[@Voltion-]

Mandalore! What telescopes should I look into getting? I have the itch now!

[@massimookissed1023]

About the only things in the sky worth looking at with a telescope are the Moon, Jupiter, and Saturn. If you want to see anything else, you're gonna need to think about sticking a camera on it to take long or multiple exposures, and use a computer to process the images.

[@averybrooks2099]

ChatGPT as of September 2021 there were approximately 14,000 stars within a 100 light years of Earth. That's crazy, I'm betting we find out the number is higher because of the Red Dwarfs Fraser spoke about.

[@HorsecreekDK]

As a followup to the Earth-Red-Giant question (Bespin): How much of an AU will Earth need to be moved? 500million years / 10.000 = 50.000 asteroid fly bys. 0,1AU in 50.000 fly bys is 300km each time. Can a single asteroid do that?

[@jensphiliphohmann1876]

03:50 f: Binoculars are probably not the very best things you can use to project the sun anywehere. The danger of damage to the telescope itself is also a matter of concern. If you happen to have a mirror telescope, this danger is most likely minimal if you remove the ocular and project the sun to a wall or something like that, since the light then doesn't need to go through anything but is just reflected.

[@AliHSyed]

21:52 FraserGPT

[@BobDaniel]

BESPIN + QUESTION: I've heard you say that you can RAISE the orbit of something by slowing it down (today's example of escaping the red giant phase of the sun), but I've also heard you talk about satellites being slowed down by atmospheric drag thereby LOWERING their orbit and needing to be boosted back up to safety. Having trouble reconciling those two things, can you clarify?

[@1969kodiakbear]

Canada and Alaska. By the way, I have difficulty communicating because I had a stroke in Broca’s area, the part of the brain that controls speech. 2/8/2021 but I lived again. (My wife helped me compose this.)

[@nubletten]

Is it strait up planned obsolesence in space industry? No dust sweepers on the rovers or landers with solar cells. I am aware a horse hair broom can scratch the surface, but if the only other option to small scratches is "let it die" then idk, seems like the data would be worth it to me. also dagobah

[@smeeself]

Tatooine

[@Hackanhacker]

space is Our world too !!! Not only earth

[@arthur_stephens]

Alderaan

[@michaelgian2649]

Hoth

[@veryrandomuser]

Had to check if I'm the odd one out regarding AM/PM and the understanding, or lack thereof of the concept, but turns out only four (five if generous) countries use it.

[@HPA97]

What would happen if Pluto suddenly teleported into the habitable zone? Would it quickly get an atmosphere?

[@deshawn994]

I know that our solar system moves but how fast are we traveling through space and what would it take to stop and seat still in space

[@zooot820]

dagobah. question, why haven’t we explored the north or south poles of Mars or inspected the ‘black sand’? is it fear or contamination?

[@bbartky]

NASA’s Phoenix lander landed in Mars’s northern polar region at 68.22°N, 234.25°E, in 2008. I can’t put a link in the comments but you should Google it since it was a very cool (pun intended) 😉 mission.

[@Hackanhacker]

Motorizing the earth :P lets raize that orbit !!!

[@johnbennett1465]

If a single asteroid passing every 10,000 years is enough to change Earth's orbit, what happens when hundreds or thousands of spacecraft are tweaking Earth's orbit each year? Do we need to make sure that all changes balance out? Obviously the effect will be small over a year, but over hundreds of years, could we cause a crisis by randomly changing our orbit?

[@billykorando6820]

Setting aside the mass of all the satellites is inconsequential, satellites orbiting the Earth wouldn’t change its orbit because they aren’t adding or removing energy. That’s why you need the asteroid pulling on Earth to then go around Jupiter. The asteroid would be acting as a transfer of momentum between the two planets.

[@johnbennett1465]

@@billykorando6820 I said spacecraft not satellites. I am talking about interplanetary missions. This can include launching to escape velocity as well as using flybys. I am also assuming that by the time we are doing hundreds of missions per year the vehicles will be much larger than current interplanetary missions. Now is even that enough to matter? I don't know.

[@billykorando6820]

​@@johnbennett1465 I would assume still trivial. The asteroid Fraser uses as an example is (apparently) Bennu, which has a mass of about 7 *billion* kilograms. It's difficult to imagine we'd ever be launching that amount of mass from Earth. Even if we were doing some project like terraforming Mars, or some other body, you wouldn't launch that kind of mass from Earth to Mars (or where ever) but either using in-situ resources or redirecting an asteroid to a parking orbit near the relevant body.

[@johnbennett1465]

@@billykorando6820 you may well be right, but I was talking about hundreds of years which does give some time for the total to add up.

[@GoldenPhil]

I love all your videos. i do have one question. If all the rovers and other solar powered gear we land on Mars gets covered with so much dust. why doesn't JPL or Nasa add either an arm with a brush to clean the solar panels or add an air blower to clean the dust off the panels.

[@bjornfeuerbacher5514]

Brushing the dust away would make lots of scratches on the solar panels. And air blower would require first compressing the air (which is rather thin on Mars...) greatly, and thus would require lots of energy.

[@GoldenPhil]

@@bjornfeuerbacher5514 thanks for the answer. would some kind vibration shake it off? like the vibration mode on a phone?

[@AngelFix]

Aldearaan

[@Yora21]

I saw Jupiter yesterday evening and was quite surprised how bright it already is right after sunset when there are still no stars visible at all. (Of course there's also Venus, but you can see that in the late afternoon all the time.)

[@MountainFisher]

Soon Venus will move to the other side of the Sun and start coming up in the morning.

[@twistedwhiskers8776]

29:34 Personal timestamp I can see maybe 20 stars but not 100s

[@LordBitememan]

Strange question: suppose a friend and I go off into deep space tied together by a weirdly hypothetically long rope. We spread apart till the rope is sufficiently taut and proceed to kill some time. Maybe we sing American Pie two or three times, play a game of Monopoly via correspondence, a trillion or so years pass. Over time does the expansion of the universe pull us apart until the rope snaps? Or, if the rope doesn't snap, are we now accelerating through space by being connected to one another via the rope? Or does the expansion of the universe just kind of go around us and not bother complicating matters?

[@tonywells6990]

That's a great experiment to do if you can wait on scales of 100 billion years.

[@LordBitememan]

@@tonywells6990 A hundred billion years? Is that all? Please, I've dealt with Comcast tech support. Give me a challenge.

[@simonehudspeth861]

I think since local galaxy groups maintain control over each other rather than flying apart I think your rope would be equal to their gravity meaning you would be just chilling as space expands around your "local group"

[@bbbenj]

Coruscant for me 😉

[@ronodowd5724]

august has good metarote lighte showers in easrernen canada

[@deisisase]

I've used the raisin bread to get people to picture the expansion of the universe.

[@nilayvyas4662]

So, a question. I believe you said it is very hard to estimate the number of red dwarfs and browns dwarfs within 100 light years of Earth. Have red dwarfs and brown dwarfs been ruled out as the source of dark matter? If so, how / why? Thanks!

[@lonny7277]

Coruscant

[@supplychainoperationsresearch]

oh algorithm gods! Head your humble servants plea and spread this video!

[@Eddyfamily]

Vote Geonosis - in your video you show an animation of “known Near-Earth Asteroids Jan 31, 2018”. If the definition of a planet includes “clears its orbit”. That is a lot of stuff that is not cleared. Can you explain “cleared orbit”?

[@zimmy1958]

Alderaan. and thanks Fraser.

[@Yora21]

It often sounds like when galaxies collide and form an eliptical galaxy, they will remain eliptical forever. Shouldn't they turn into a disk shaped galaxy with enough time, by the same processes that make solar systems and planetary rings become flat disks?

[@TraditionalAnglican]

Kamino - The dust is probably less an a mm thick…

[@sprinter768]

My vote goes for Bespin

[@GadgeteerFarm]

Could we use gravity slingshot to move Venus away from the sun and maybe closer to it?