Astronomy with Finlarg, Part 1: The Earth - Moon System

[thereforeithought]

Re: jumping 6X higher on the Moon than on Earth, many science fiction stories about Deimos, the small moon of Mars, feature astronauts jumping to great heights due to miniscule gravity. Good reads.

[finlarg]

@thereforeithought I don't have the figures to hand, but I would imagine that the escape velocity of Deimos is quite low, so it might be possible to end up in a separate orbit of Mars?

[thereforeithought]

@finlarg That's what one of the stories said, I was a kid when I read it, and it was science fiction, so it's not reliable, nice idea, though.

[finlarg]

@thereforeithought I just looked up the escape velocity and it seems to be about 15 mph, which is not very fast. So if an astronaut jumped up at a slower velocity, he or she woul slowly float back down. But if they were able to lauch themselves up faster than this, then they'd escape Deimos' gravity altogether and orbit mars as a separate 'satellite'!

[thereforeithought]

@finlarg I've actually read that a long time ago.

[nahaymath]

Thank you for posting this video, finlarg!

I came here to ask one question: astronomers' best theory for how the moon formed was that object X smashed into young earth E, the ejecta then coalesced to become the new moon. How do scientists know it went that way, rather than object X shot in from outer space and got trapped by E's gravity and became the moon itself?

Thanks for replying!

[finlarg]

@nahaymath You're welcome!

To my knowledge, it is because of the geological dating of the moon. It appears to be the same age as the earth, 4.6 billion years. If it originated from elsewhere, then that would be a heck of a coincidence! The moon also seems to be made of similar material to the outer layers of the earth, not it's iron core, so the idea that something collided in a glancing blow and ripped off some of the outer materials seems plausible.

[nahaymath]

@finlarg Thanks! I should have known that.

[psandbergnz]

I don't find this video very well explained, for example at 4:36, the speaker says: "the bulge [of the moon] is enough to keep the same side facing the earth".

What sort of explanation is that? What relevance has the bulge of the moon to do with the fact that on earth we only see the same face of the moon?!

I believe the explanation that the same face of the moon is always visible has to do with the moon's rotation relative to the earth.

[finlarg]

@psandbergnz The fact that the moon rotates at the same rate as it orbits the earth is not co-incidence. The bulge keeps it tidally locked, so the same side always faces us. As far as we know the moon used to rotate relative to us, but it gradually slowed down, to the point where it stopped. From then on gravity caused a slight bulge towards the earth. This bulge also prevents it from rotating, in other words it would take a HUGE amount of energy to start it spinning again.

[psandbergnz]

@finlarg, thanks, but I think that the moon DOES spin on its axis. Hence, we always see the same face of the moon.

Take two balls to represent the earth and the moon. Place them on a table, the "earth" in the centre. Then mark a point on the "moon" ball, the point facing the earth. Now orbit the moon around the earth. You have to spin the moon one revolution per orbit for the point to keep facing earth. The moon has a day and night period (27 earth days), indicating it spins.

[finlarg]

@psandbergnz It depends on your point of reference. From earth, the moon does not spin. From the sun and other planets the 'earth-moon system' spins around it's barycentre, which is within the earth. The earth spins relative to this system, but the moon does not. The moon spins relative to the sun, but at the same rate as the system. One day in the distant future the earth will also stop spinning, but whether it will be tidally locked with the sun or moon, I'm not sure off the top of my head...

[psandbergnz]

@finlarg, your explanation does sound plausible. The same moon face could always point towards the earth if the moon did not rotate, but only the earth did. An analogy might be attaching a string to a tennis ball, and then whirling the ball around you. The point at which the string attaches to the ball is always facing you as you turn around to keep the ball rotating. The string prevents the ball from spinning on its axis.

This earth-moon system could permit day and night on the moon.

[finlarg]

@psandbergnz That's kind of how it works, just substitude the string with gravity. Each lunar 'day' lasts a fortnight, followed by a similarly long night.

Check out this animation to see what the earth would look like from the far side of the moon

watch?v=oUgQ3ylaEK4

Notice that the earth moves a bit, which means we don't see the exact same half of the moon, it 'wobbles' a bit. In the animation a month is condensed into about 30 seconds!

[MacNutz2]

great stuff Finlarg

[finlarg]

@MacNutz2 Thanks Mac!

[unassumption]

Cost probably prohibits lunar observatory

[unassumption]

Impossible to comprehend these sizes, times, speeds, etc

[finlarg]

@unassumption Difficult, yes... but not impossible! This video deals with the more local stuff, it gets harder!

[unassumption]

Education doesn't teach you most things - i learn more from reading textbooks. Yale, MIT and standford have series on astronomy too if you want to watch them? I prefer f=mg to universal gravitation if you know what i mean earth should be our focus since its where we live. Learning about the beauty of the universe > all fiction and art and could have an earthy use. I like living in our system mostly, biology is nice and entropy maximizing :)

[finlarg]

@unassumption I think all aspects and approaches to education are important, just as long as it sticks to the known facts and makes clear what is hypothesis. Each person is receptive to slightly different media.

[Schamsie]

Well done. Thank You.

[finlarg]

@Schamsie You're welcome!

[pchtermino1]

Well done.

[finlarg]

@pchtermino1 Thank you!

[MsScienceFTW]

Good job. :)

[finlarg]

@MsScienceFTW You're most kind!

[BadScienceForFools]

Since I (maybe like many others) dont have much knowledge about astronomy I find it very interesting and important to get some simple and basic facts for an introduction in the subject. I'm really looking forward for more of this.

[finlarg]

@BadScienceForFools I'm glad that I can pass some of my enthusiasm for the subject on to others! For me the best way to learn is one step at a time and always relating to things we're familiar with, especially when huge distances and sizes are involved.

[KrisBlueNZ]

Cool vid, nicely narrated and edited and full of interesting info. Thanks mate :-)

[finlarg]

@KrisBlueNZ No worries, thanks for the encouragement!

[finlarg]

@OldSchoolSkill Thank you kindly!

It's mind boggling to imagine what the human race COULD be doing now in 2011, if we learned to stop arguing and fighting with each other... it's so sad... I believe that youtube can help the flourishing of science, particularly by inspiring young people to learn, for curiosity's sake, rather than just to further their earning capacity.

If you haven't already, check out 420simpson and Vitoldian, two young youtubers, wise beyond their years!

[GluteusIlluminatus]

Interesting video. I'm looking forward to the rest of the series.

[finlarg]

@GluteusIlluminatus Thank you, they won't be ready for posting as quickly as I'd like... work and 'real' life has a habit of getting in the way!

[TheBlackSpider82]

Nice vid. I enjoyed it. Keep up the good work. :)

[finlarg]

@TheBlackSpider82 Most kind, thank you!

[Vitoldian]

Great video, very inspiring! However, I think the reason the colonization of the Moon hasn't started yet is more due to lack of decent funding than technical issues. We already have telescopes in the orbit, the trip to the Moon just costs more.

[finlarg]

@Vitoldian Thank you very much!

Without a doubt, I'm sure NASA would have had many more manned missions by now if they could afford it! But something I would be keen to do if I were involved would be to have a small telescope on the moon... even if only to get some more pictures of the entire earth!

[r95rdstr]

In my mid-teens, I was appalled at the audacity of man (The Catholic Church) in believing that we are at the center of the universe, the pinnacle of all that is. I also realized that space and time are boundless. Since then, and also having no formal training in astronomy, I find it much easier to conceptualize the vast expanses in space in terms of light speed distances, rather than km/mi. The moon is about 2 light seconds away. The sun is 8 light minutes. The next star is 4 light years, etc..

[finlarg]

@r95rdstr Absolutely, the concept of light years, parsecs and so on are invaluable for understanding the vast distances involved. I deliberately left that out of this video, to try to focus on our immediate locality and keep episode 1 fairly concise. I plan to deal with the speed of light in some detail in future vids...

[r95rdstr]

@finlarg My apologies for trying to jump ahead of the rest of the class..lol! You're doing a great job in teaching the basics first, which is well warranted by the other comments here. I look forward to your future videos.

[finlarg]

@r95rdstr It's hard to know how much info to put into each video. One of my earlier videos ran to over 12 minutes (An alternative to the ten commandments) and I think I tried to cram far too much into it! It would have worked better as 2 or 3 separate videos...

[macnutz]

Big thanks, I love this stuff.

[finlarg]

@macnutz You're very welcome!

[irreverentreverend]

Very well done. I'll be keeping watch for your series, including the math and physics parts. Maybe I should have paid more attention, too.

My teachers said I should have become an astronaut because I took up space in school.

Good job.

Rev

[finlarg]

@irreverentreverend Thank you!

My teachers probably thought I was a waste OF space! I used to be everything that annoys me about some kids today!

[tenagliac]

Good show. What I wonder is about brightness. I seen the nebula in Orion and the Andromeda galaxy in my telescope (60mm refractor). What a disappointment. Would they be so dim close up or glorious like in the photographs in astronomy magazines ?

[finlarg]

@tenagliac I don't think they would be particularly bright, even if you were much closer. The photos you are speaking of are usually taken on long exposures or consist of many 'stacked' photos, to capture as much light as possible. The stars within the famous 'pillars of creation' hubble photo (as an example) are massively over-exposed, so they look like small spheres, when in actuality they are points of light... they are SO far away and SO far apart!

[itsasin1969]

Question. If we look back far enough we should see the singularity or big bang. True? But if we look in the any direction, do we see the same singularity? Are we looking at the same place when we look far back enough in any direction?

thank you thumbs up..

[finlarg]

@itsasin1969 Theoretically yes, but the universe was opaque for the first few hundred million years... but what we DO see is the cosmic microwave background radiation, in all directions, which is the red-shifted afterglow of the big bang. We can't see the singularity but we can deduce it's existence from the available evidence and our understanding of the laws of physics. In a kind of way we are looking at the same 'place' by looking in all directions, but it's complicated!

[420simpson]

Great video. I assume you have read Cosmos by Carl Sagan. When I lived in Montana, ts a very isolated state in the US, There were no lightsources to distract starlight, so the night sky was awesome. Now i live in Texas, with many big cities, so I dont have that here. If you havent, I suggest watching symphony of science videos. I think it’s extraordinary that gravity and space affect time differently. We try to think of time as a constant, when really it is just perception.

[finlarg]

@420simpson I certainly have read Cosmos... and got the DVD's of the TV series!

It's great when you have a really clear night, away from light pollution - plus, knowing something about what you're looking at, makes it even more awesome!

Time and space are not fixed (nothing to fix them to!) and are often referred to as spacetime. It all depends on your frame of reference... the only constant is the speed of light.

[luxfair]

Great video. Thank you.

[finlarg]

@luxfair No probs, glad you liked it!

[AtheistApe5]

This looks to be very interesting. I'm a fan of astronomy and always hearing more about it. I guess my question would be, what is your particular area of astronomy to study the most?

[finlarg]

@AtheistApe5 It's hard to say... all of it really! I have loads of astronomy books, old and new, many of which I've read more than once. I've recently been trying to get to grips with relativity, the speed of light and the strangeness of trying to imagine the shape of the universe, which you can never see simultaneously!

The further you go into astronomy the more physics, maths, chemistry and even biology you encounter... I wish I paid more attention at school!