What's the Straight Dope on Acoustic Levitation

Factual Questions
1

I was watching a video on the building of the great pyramids,and a new theory is that the blocks were kind of “floated” over to where they needed to go by acoustic levitation.

I looked into acoustic levitation a bit, and apparently its a real thing, with scientists being able to float small objects the size of a screw.

So theoretically its possible 40 ton blocks were floated with sound.

But what exactly what it take to do that? Being the right frequency? Being SUPER loud?
This isn’t necessarily a post about is this how the pyramids were built, more like, is this even remotely possible?

2

I’m not a physicist or an engineer, but I’m sure one will be along shortly.

I would call BS on the idea if only because (a) common sense tells me that it would take at least the same energy as any other method of lifting blocks that size (which is A LOT of acoustic energy) and (b) it seems highly inefficient (due to energy loss as the acoustic waves escape the actual job of lifting). According to Wikipedia, current technology only permits the lifting of objects weighing a few grams. Building a crane out of old Transformers parts would seem to be a lot better way to go about this.

I also suspect this thread is going into a different board shortly.

3

So, you have two options:

  1. The Egyptians moved multi-ton blocks using the obvious method of lots of people pulling on ropes (and using boats to get them to the area of the pyramids).

Nothing magical about it.

Or

  1. They somehow invented an amazing tech that we still can’t build today. Leaving no records whatsoever of such tech and not developing any tech at all that’s remotely advanced for the time. They didn’t even have steel then!

Also, do you have any idea what the energy from that intense of sound energy does to rock?

The simplest mental filter gives you the answer.

4

Obviously, the Ancient Egyptians did not have accoustic technology beyond the lyre. It is safe to say that they did not lift multi-ton bricks with the power of music.

As for the general idea of lifting large objects, there a few problems that would make it more difficult at larger scales.

Firstly, viscosity reduces with size. To a microbe, water is akin to a syrup. To a human, it’s just water and presumably, for a blue whale, it’s even easier to move through - possibly explaining their tiny flippers compared to a smaller fish like a koi which has larger and more numerous flippers. I would expect that to remain true with gasses. At a small scale - like with a pebble - air will be relatively viscous and serve as a somewhat reasonable medium for slapping your target with to keep it raised up in the air. But, at a large scale, potentially, you can’t even compress air to be thick enough to even be able to support such a large mass.

Secondly, there is the square-cube law. Basically, if you double all of the measurements of a cube, it gets eight times as heavy. Let’s take an example:

1x1x1 cube
Weight: 1 cube

2x2x2 cube
Weight: 8 cubes

3x3x3 cube
Weight: 27 cubes

4x4x4 cube
Weight: 64 cubes

As you grow a rock in size from a pebble to a giant stone fit for building a pyramid with, its mass is growing at a much greater rate than its dimensions. The amount of energy you need is proportional to its mass, so if you double its size, you need to increase the amount of energy by eight times to keep it aloft.

Lifting things on a vibrating cushion of air is not a particularly efficient means of lifting something.

(I’ll note that both the first and second problem are probably the same problem expressed in different ways.)

A human runs at something like 100 watts per hour, in terms of food intake. As the person building the pyramid, you need to be supplying all of your workers with at least that in order to build the pyramid. If you have 500 workers, then you’re spending 50,000 calories per hour.

If you’re using acoustic levitation and that requires an equal amount of energy to power 1,000,000 lightbulbs just to lift a stone for a single second, your power needs are just off the charts. Egypt couldn’t produce that much power at that moment in time. All they had access to, in terms of energy, was solar power harvested through plants. That solar power was limited to what could be collected that season and is limited by the surface area of a small band around the Nile. Modern day humans can exceed that by mining coal, oil, and uranium - harvesting energy that accrued under the Earth over a period of billions of years, shipping it from impoverished countries who don’t use much electricity to wealthy ones who do.

Obviously, that’s not an impediment if the Ancient Egyptians had aid from aliens or something, but I would expect that the aliens would have had a more efficient method of lifting heavy weights - anti-gravity or something - rather than using acoustic levitation.

I’ll also note that, you have to loft the object first, before you can further lift it with acoustic levitation. That’s a strong demerit for a lifting technology.

5

Not to mention what it does to human flesh.

You’re talking about the kind of energies that Bond villains put into their death traps.

6

I think you meant to say “Calories per hour”, there, not “watts per hour”. Watts are already a power unit, so “watts per hour” would only be useful if you were talking about power changing.

7

I won’t comment on the pyramids (what happens in Ancient Egypt stays in Ancient Egypt).

But, I find it amusing that people are hemming and hawing about levitating things bigger than screws when we have hovercraft.

8

We can levitate very large things. We just can’t levitate large things using sound.

9

Hovercrafts have engines.

10

There were a lot of cats around in ancient Egypt. I don’t know if they had an acoustic substitute for vacuum cleaners, but I wouldn’t underestimate the levitating power of a few dozen startled cats tethered to a block.

11

Maybe the Egyptians knew what is now a lost art: cat herding.

12

Ah, the [del]Chewbacca[/del] Hovercraft defense!

13

That use acoustics as the hover inducing mechanism?

14

Acoustic levitation is a thing. But mostly you only levitate really small/light things.

Consider what sound is…a pressure wave in air. This is how you hear. Sound hits your ear drum and moves it. It is a physical thing with physical effects.

Now consider how much pressure you would need to lift a stone used in building the pyramids. I can’t do the math but I am not sure it is possible (even in theory assuming unlimited energy and ability to convert it to sound). I would imagine a compression wave that powerful (using air-pressure to levitate a multi-ton stone) would super-heat the air and kill most things anywhere near it and probably shatter the stone (if not outright melt it).

And why would you want to try this method anyway? Of all the ways someone could harness power to move a multi-ton stone the best idea is sound??? How about trying a lever and fulcrum or pulleys? Waaay simpler, waaay more effective for this task.

15

This would seem far-fetched, except that acoustic levitation was already a tried and tested technology on Atlantis. The lizard people told me.

16

As I said, I wasn’t commenting on how the pyramids were built, or even saying this particular method of acoustic levitation is scalable. I’m just saying being cynical even at the mere notion of air lifting heavy objects is odd given aviation history in general, things like helicopters and hovercraft, but even more subtle things - I’ve seen something like a large air hockey table used to demonstrate inertia by lifting quite a heavy object. The concept is proven, all that’s in question is the particulars.

17

If vibrations won’t work; how about hydraulics? Here is a video from a guy who thinks that they could have used water to float the blocks into place: How were the pyramids of egypt really built - Part 1 - YouTube

18

In terms of transporting the things a long distance, using waterways and rivers may make sense (though I don’t see submerging them - how do you get them back up out of the water? Why not just put them on a barge?)

In terms of lifting stones up to place them on the top of the pyramid, while his solution is inventive, if the Egyptians had that sort of technology then the Romans would have, and if the Romans had it, we would know about it. We would also have archaeological evidence of a stone waterway coming up to the base of the pyramids. The people who built it would just fill the things in with dirt, so they would still be there, preserved under the sand.

I’m unaware of any case where floating things up a vertical shaft of water was ever used to lift something (?). I imagine that there are practical engineering issues with that which make it infeasible to pull off in reality until you also have the sorts of technologies that would allow you to avoid doing it that way.

19

I don’t see how they would have gotten the water up to the top at a faster rate than it would leak out thru cracks.

Also, you need BIG floats to lift rock. The scale shown is ridiculous.

20

Roman aqueducts transported water for dozens of miles, presumably without significant loss. It’s just a matter of having a waterproof binder between your stones.