Gravity Is Not a Force (And The Acceleration Is Upwards!)

Because two masses warp spacetime and cause each one to pull the other towards it, which of the two masses were accelerating "upward," and why was not the other?

[EdwardCurrent]

Just watched this in its entirety. 5:17 is pretty disappointing. I didn't even think to talk about centripetal acceleration in the video, because I figured anyone who's taken any physics classes at all knows that the acceleration of a rotating system is toward the center, not away from it. Also, you've confused linear acceleration with four-acceleration (admittedly I should have made that more clear). As for which direction is up? That would be *the direction pointing away from the massive body in question.* The video is basically 7 minutes of straw-man misunderstandings of general relativity and bare assertions that are inconsistent with the theory, peppered with unnecessary insults. Do better next time.

[fireflyf]

Ed used to be a Poe of the ultra-religious video producers on YT, but has since transitioned away from that to produce serious content such as his excellent videos countering 9/11 truther claims.

His video you're replying to here actually IS a pretty good simplified explanation of gravity from a relativistic perspective.

[keithnewton]

At 7:00 I thought I was going to be treated to "GRAVITY" but I was still happy with the ending. Thanks

[ldmitruk]

I was desperately hoping for a reprise of the gravity rant.

[StubbornProgrammer]

We're so used to Quantum Physics being the "weird physics" that we forget General Relativity is pretty _fucking_ weird compared to our everyday intuitions. The TL;DR is that General Relativity says gravity is not as a force, but space-time curvature, and objects following that curvature are going in "straight lines". This means that to stay a constant *distance* away from the Earth's center we have to constantly accelerate upwards, at least at the rotational speed of the surface of the Earth.

Following is the "Not Long Enough; Explain That Bullshit".

First let's get the #1 thing that EdwardCurrent got wrong out of the way... the "acceleration due to gravity" is not up. Under GR there IS no acceleration due to gravity because there IS no gravitational force to accelerate anything. No, what points up is direction of acceleration required to DEFY where the local curvature of space-time, ie. Earth's gravity, says objects "at rest" should be going. This part at least is in perfect agreement with our everyday experience, and as far as Newton is concerned, even the forces under our feet are right - under Newton's gravity the ground stops us from heading to the center of the Earth, and under GR it does exactly the same thing.

The bit that defies all common sense is what "at rest" means under GR. Quoting from
"Phenomena that in classical mechanics are ascribed to the action of the force of gravity (such as free-fall, orbital motion, and spacecraft trajectories), correspond to inertial motion within a curved geometry of spacetime in general relativity; there is no gravitational force deflecting objects from their natural, straight paths. Instead, gravity corresponds to changes in the properties of space and time, which in turn changes the straightest-possible paths that objects will naturally follow."

So under GR, satellites in orbit around the Earth are actually going in straight lines (once we exclude all the atmospheric drag and thrusters and whatnot). Me falling to the center of the Earth because I'm going too slow? Also a straight line. And how to we deflect an object from following a straight line? We accelerate it. What's exerting a force on me right now with the right magnitude and direction? The ground. The ground is accelerating me upwards away from the path defined by the space-time curvature caused by the Earth. Under GR it makes perfect sense. Under everyday intuition? Hell no.

That's why General Relativity is fucking weird.

[petehjr]

Edward used to do Poe videos but they were firmly tough in cheek. Now it looks like he's doing deep Poe videos without the nudge nudge wink "checkmate athiests".

[v.sandrone]

Up is defined as away from the giant turtle that pushes the earth.

[ronaldderooij]

I am sorry to say that the video you criticize is right. The problem you have with it, is that you do not distinguish reference frames. A mass bends spacetime. Including TIME The acceleration is caused by the time component in it. You follow the geodesic that is the shortest way to the future. That is "falling". Up and down are, as you say, not really relevant. So, two people sitting in chairs on opposite sides of the earth each have their own reference frame relative to earth (relativity, right?). Their shortest way to the future is to fall to earth. Both are standing on solid ground, so they get to be hindered. As they are not falling anymore, they are accelerated (due to not being able to get to the shortest way to their respective futures) UPWARD by earth. The moon is constantly falling in freefall around earth. It IS following the geodesic (shortest way to its future). So it is falling, but caused by the centripedal (not centrifugal) force (or angular momentum) it is not physically moving towards earth. So, it circles. If it circles, it does follow a straight line in spacetime, but it does not follow a straight line through space (without time this time). So, it is accelerated towards earth, not being able to follow a straight line (reference frame here, the earth moon ensemble).

[subductionzone]

What? Desertphile cannot do orbits? The acceleration of an object on a string swinging in a circle is towards the center of the circle. The string is pulling it that way. You conflated the resultant centrifugal forces, a psuedoforce, with centripetal force.

[gepisar]

6:54 OMG! I thought for a minute there, we were going to get a Desertphile meta clip of "Gravity!!!" in an actual desertphile video!!!

[abitoftheuniverse]

Something like 10 years ago, a lot of the more popular channels on Youtube known for either promoting atheism, skeptisism, rationality, or, just for calling out bullshit, snake oil and pseudoscience, they all made videos about "A strange ball of light suddenly appearing in the sky." They were great, the whole thing was awesome. Every channel put it's own spin on the idea. Every person had their own expressions, their own reactions and their own character, behind the video, but they were all pretty much saying the same thing. They were all making the same point(s).
1. That we don't get outside enough, on average.
2. If you don't know what's going on, you can basically make it seem as if it's something supernatural, or, extraterrestrial (which in this case, the sun would be) or miraculous.


But they all did such a good job, they were all so funny, and many of their videos wound up getting to people looking for 'real' UFO videos, that they managed to make a strong point and helped a lot of people to not fall for that sort of WOW/WOO BS that people attach to things as their brains struggle to find explanations.


I almost feel like this is some sort of satirical collaboration, but, I also don't want to be that guy that ruins the joke and doesn't let the moral of the story, sink in deep enough so that it can take hold.


Obviously I love both Edward Current and Desertphile, you've both done great things for Youtube, and by YT I mean for us, that use it, for entertainment, education and ...empathy. We love to laugh, to learn and to relate to each other's lives. And some of us are just here for a good argument. So, if that's what this is, if Eddie is just trying to provoke an argument, and DP you're just playing along for the fun and lessons the observers can take in along the way, that's awesome. Neither of you have to come out and admit it. You're both great channels.


The 'Checkmate, Atheists.' guy and the "Gravity!" guy, (even though I knew of both of you and were subscribed to your channels long before those became your most mimed words) in an argument? I'd love to see a back and forth play out between you, despite all the comments saying "This isn't a real argument." or "he doesn't really believe that" or "whatever". Some of the best debates are those where two entertains basically draw their arguments out of hats and then defend them, and I'll be honest, I'm dying for some really good debate drama and, not the kind of dirty name calling that there was between people like Captain Awesome, Fake Sagan or any of those types of people back in the day. Maybe just a parody of that sort of thing, or a parody of the arguments that we've had to hear, over the course of our lives, either from religion, conspiracy, pseudoscience or anything. Anything! Make a mud fight out of 2020 for the fun of it. Please! I'd love that.


Live long and prospect.

[raymondthebrotherofperryma]

If the Universe is accelerating "upwards" at 9.8 m/s^2 then why is this force a sixth as strong on the moon and 0 on the ISS? Hmm?

[Saxie]

As my favorite teacher in high school once said, "Never seek logic where none exists.".

[subductionzone]

This was an attempt by Edward Current to explain General Relativity to others. It seems that they can't quite get it. In General Relativity gravity is not a force.

[immortalsofar]

The speed of light is 299792458 m/s.
I've been alive for 54 years and experienced gravity for every second of that time.
Therefore, if gravity was caused by the earth accelerating at 9.8m/s "upwards" and assuming (somehow) that it was stationary when I was born, it would have reached the speed of light before I was 10 years old, been unable to go any faster and gravity would have shut off.

[BuellersBack]

Holycrap, there are so many mistakes in your video (Desertphile's). Centripdetal force DOES accelerate the spinning ball on a string towards the center. Common man, this is Physics 101, Sheesh!

[Jean-qnfy]

Wow! How did I miss this? I usually gobble up your videos as soon as I see them.

[bdf]

He's right about the apple in the spaceship. There is no force acting on the apple. A force is involved, but it's acting on the spaceship. No force on the apple itself.


Now my head hurts.

[mathis]

2:20 He is right and you are wrong. In the reference frame of the rocket the apple seems to move, but there is actually no force acting upon it. The thruster is accelerating the rocket, not the apple.
3:20 It is descriptive, but it is an desctiption of how reality actually works. Im not entirely sure what you mean by the term "perception" here. Because it sounds like you tie it to a sentient observer. But this is objective. It also works for two clocks or cameras moving wrt one another
4:00 Actually, when it comes to general relativity, statements like this, although not intentionally, aren't even that wrong. To say "earths surface is accelerating *outwards*" could be a somewhat acurrate description. Spacetime is distorting, such that space is "falling" into the earth, and the repulsive electromagnetic forces accelerate the matter outward.
General relativity is an absolute mindfuck, and my understanding is only at the level of one specialized course for one university semester. So take my interpretation with a grain of salt
5:20 You are wrong again. The string is pulling the ball toward the center. Pretty much just like the sun is pulling the earth toward itself, making it fly around it by always pulling on it. If no force acts on the ball it moves straight forward, if it is pulled toward the center it moves around it, and if it is pushed away from the center it will fly away.
5:40 Yes the ground is pushing (/enacting a force on) you upwards, through electromagnetic repulsion. If not, you would accelerate downward, due to gravity. Or did you think gravity magically stops as soon as you touch the ground?
6:30 Yes your body does that. If you stand on a trap door and i open it, the force keeping you in place is gone. You won't just float there. GRAVITY, YOU FUCKING MORON! GRAVITY! ;-)
He honestly understood more about mechanics and relativity than you did.

[woowooNeedsFaith]

5:16 - I would have to disagree with you. To counteract inertia, you need acceleration towards the center. Otherwise the object would keep going straight line.