Gravity Visualized

tivity the explanation for gravity is that matter bends space and so you put mass in a place of space at warp space-time and objects are not feeling a force of gravity they're just following the natural curvature and so this is a sheet of lycra where do you get this is my old bike shorts no there's literally a spandex calm you can get a sheet like this if you buy the sales stuff so you don't care what it looks like right for like 20 bucks maybe less depending on the sale and so you put matter and it warps space-time and so if I have another object it also warps space-time they feel that and they're attracted to each other and so that's that's Einstein's picture of gravity objects warp space-time feel that curvature and move accordingly and if you have more mass you have more mass is going to bend space-time more respond and so you put something there now it's attracted now in reality that big mass would feel the warping of space-time by the marble - right it would move a little bit but we usually usually ignore that you know the earth makes the Sun move a little bit but it's so small we can ignore it the moon makes the earth kind of wobble around two point three quarters of the way from the center of the earth we usually don't account for that when we're looking at satellite motion well instead of just letting go of one what if I give it a sideways push now it orbits now it's losing energy which wouldn't happen in the solar system right not noticeably there's some perturbations from other planets and things but this one does lose energy and spirals in if I don't push it as hard it will do the lips when you study the solar system all the planets are going around the Sun the same way why is that did God decide the only life clockwise or as I'm whether he's above or below the solar system right why is everything going in the same direction well the answer is it wasn't different directions but there was a preferred direction the distant form from had a slight preference one way versus another and things go in the opposite way got eliminated and when it's all said and done everything is going the same way that usually that works 90% of the time and so I had slightly more in one hand and another but I don't consciously do that and you want to give them something spread out a little yeah the wrong way get eliminated right now there also would have been you know this is where this analogy breaks down there's you know another dimension right but those things are out of the plane also that weren't near the preferred plane also got eliminated and so that's kind of cool now my students use a pH et Phet simulation called my solar system and so they've seen all this on the computer and when we do this during our special relativity unit they're like he is just like the computer that's kind of cool that a stretch see the Micra model sings suicide just like it learn to the computer now some things we've discovered using this I'll say it's just some larger marbles my friends with them out but they've been space time too right and so maybe you can get one thing so the earth-moon system maybe and so you see that this seemed you know you can't buy micro this big you get it in rolls and you have to sew it together I've been told to use a stretchy string the stretchy thread to sew it together and so the next time I do it I'll do that because it pulls and so you just a little bit of thread fixes it and so in the morning when I first set this up look at leaning against the table will be underneath fixing holes from last year one time my principal walked in and I hear somebody in the room and I'm underneath on the middle sewing in a little paws yet and then he's looking around for me and he kind of knows some of these in the room buddies oh there you are because what are you doing there and I go I'm repairing a rip in the fabric of space-time you've probably seen plastic ones of these right the Discovery Center Children's Discovery Museum in San Jose has won the Exploratorium has won sometimes they have MIT's shopping malls you put money in it but one thing you can't do with those is put two masses in and so when we went to the moon when we first started we set our spaceship so I'm going to call free return trajectory x' so they would go to the moon and this is hard to get down and they would come back and like a figure eight and so that lets you show now of course the moon is smaller but if you look at the plots of the free return trajectory back from the Apollo program you'll see it has a figure eight sort of shape and so this takes a little bit of practice to be able to do the figure eight these clamps around here you can adjust it to make it tighter if it's not working so Steve and I when we set this up in the morning we played around with it and actually I think it was working better than usually is it's so not easy and so I go through that's one year a kid who read some stuff about the dark energy energy have extra oh and so I'm just energy what does that makes everything come apart right and so dark energy would be that stuff goes apart rather than toward it so if you work in dark energy anytime right and so I go through that spiel maybe it takes me ten fifteen minutes talking with the kids you stuff they're not familiar with and then I just let them play and so that's where we discovered the earth-moon thing is I just let it play and they're like mr. Barth career-low and they're all excited cos they discovered that so so if you want to try it out what we do but we want to play mr. burns so I see the whole thing if you buy all the parts and everything is about a hundred dollars but one of my favorite days so you're gonna do it Monday right Steve don't do it but just do it once and you'll be hooked it will take a little bit of cooling to put it together but I'll post the plans it takes it comes apart all the PVC pipe wrap it with a bungee cord stuff the biker in that box and I can carry the whole thing myself this is about the right size you can get your whole class around it pretty much smaller what one problem is reaching some of you I think would have trouble with that so you get a student to do it right one thing you got to watch though is some students will think to go underneath to push up and then while they're underneath somebody decides to put the big mass out and you know they get their space-time warped and so just tell me can't go under and so is general relativity in the state standards no probably the the crowning achievement of science not in the state standards can you fit it in after the star test you bet you can find some videos like you know I show a thing on gravity waves and then we do this and that's you know a day almost a day but since I don't understand it myself that's plenty so let's go back into the room

Channel: apbiolghs

Views: 81,165,939

Rating: 4.7826362 out of 5

Keywords: space, time, warping

Id: MTY1Kje0yLg

Length: 9min 57sec (597 seconds)

Published: Sat Mar 10 2012

Reddit Comments

[u/IamSparticles]

If you want a crash course in orbital mechanics, try out Kerbal Space Program. Or if you want something easier try Simple Rockets on iOS or Android.

[u/Whitegook]

This guy man! He deserves a real serious salary and incredible amounts of respect. Him (and maybe colleagues) figured out how to explain incredibly complex material in very real term and make it fun and interesting! I mean this presentation here, with a slight amount of presentation practicing, could be a TED talk not only about gravitational mechanics but quality of teaching.

[u/[deleted]]

You know all the matter in space they can't identify. Has anyone considered that it might actually be spandex?

[u/LXicon]

orbits were explained by Issac Newton mathematically, given that objects would have a force acting on them that got bigger with more mass and smaller with more distance : F = G x ( m1 x m2 / r² )

Newton didn't know how gravity worked, but he explained it and proved that orbits would be in the shape of ellipses.

the linked video shows how Einstein's idea of "Space-Time warping" would explain how gravity actually works. If you imagine 3D space flattened down to the surface of the trampoline, the mass of the objects warp Space-Time like the surface of the trampoline is pulled downward.

it's not that simple. 3D space and even time are warped. if you flew a clock in orbit, it would be further away from the earth than a clock on the surface so time would be warped. GPS satellite clocks are actually programmed to run faster so they match clocks at the surface. if they weren't, your GPS would be off by miles!

[u/BenevolentCitizen]

This analogy helps to visualize what's going on, but I still have a blind spot in understanding what causes gravity.

The warping of the fabric in the case of this analogy is caused by real world gravity -- meaning, the fabric is being warped because the gravity of the earth is pulling the weights down, which in turn pull the fabric down.

But what's not explained here is what the real-life equivalent is of what earth's gravity is doing in this model. What I mean is, mass causes spacetime to warp, and this activity models the effects of that, but it doesn't help explain why mass does that -- or at least, if it does explain it, I'm not understanding.

Once spacetime is warped, it makes sense that objects move into orbits: they're continuing to fly straight, as per Newton's first (?) law, but "straight" is curved thanks to the mass of other objects. But why is the mass of the other objects curving spacetime in the first place?

(This might not be the right venue for this post. I can x-post to /r/AskScience if that's the case.)

Follow-up: Thanks all for your posts. After reading through your replies and doing some searching, I see that this model doesn't explain why mass warps spacetime because we don't know why mass warps spacetime!

[u/Guesty_]

My favourite part was when he made the smaller marble orbit around the bigger marble while they orbited around the centre weight.

[u/[deleted]]

His "fixing a rip in the fabric of spacetime" and "get their spacetime warped" jokes would be enjoyed on /r/dadjokes

[u/post-baroque]

Something I never understood: This is explaining gravity by using gravity. The thing being modeled needs itself in order to work. So it really doesn't explain how gravity works, just what it does.

Or am I completely missing the point? Is this meant to just explain how the warping of spacetime allows gravity to interact with mass?

[u/c53x12]

Pretty sure Sagan illustrated this as the "rubber sheet universe" decades ago. It's always fun to see in action, though.