I know it'll sound sarcastic, but it's a good illustration of the point:

Go build a racecar, personally, right now. No, you can't practice making a simpler one first. Straight to trophy winning.

Well, what's the problem? Racecars already exist, so it's not even like you need to develop new technologies. Go, do it. Then also make a profit, because no one's giving you free money here. Chop chop.

In this analogy, the only difference between you and them is that the current chip makers know how to make a moped.

Making stuff from scratch isn't easy, and these guys are working literally at the edge of what's physically possible. It's not even completely sure if you can go even smaller than currently available.

For comparison, you can't make a 0.01 nm chip because that's less than half the size of a hydrogen atom.

And to even do the current work, you need to come up with and build whole new tools and machines, which cost billions, because they're literally manipulating atoms at this point.

Because an individual photolithography machine costs millions of dollars to build.

The first prototype usually costs several times that.

To get smaller features, you have to keep using shorter and shorter wavelengths of light.

The latest machines use ultraviolet light. So, in order to see what's happening, you need UV cameras, and software to convert the images to something the human eye can perceive.

Then, you need to develop techniques that can etch those tiny features; it's roughly analogous to writing with a marker; what works when the letters are 4" tall doesn't work when they're 1/8".

You need ultra pure chemicals in an ultra clean environment. But many of those chemicals require special handling and materials to transport and apply them. Those materials in turn require exotic techniques to make and machine them.

So you might have to become the world expert in welding a particular metal, at incredibly small scale, without contaminating anything.

The world is full of failed attempts at all of these things.

You might spend hundreds of millions of dollars just to fail.

Because there are parts to the situation where you calculate it out, and it might work, but then you go to build your fabrication machines, and nothing you do gives you the precision necessary to make the transistors that small.

And now you've just put 3 years of intense engineering and money into a product that doesn't even make it to market.

You have MILLIONS of transistors in there, and they're applied with a process that's like photography. So you're asking them to go to the biggest zoom possible, right away. But unfortunately, every time you zoom a little bit more, you could have more errors. 1% errors means 10,000 transistors are bad, and that means that chip is shot, no good at all. Your computer could go haywire if maybe even a single transistor is bad, the error allowances are extremely small.

So if you look at it historically, look at what happened when they sent up the space telescopes. They had issues with the Hubble lens (zooming). Every time you step up in technology, there are errors that have to be worked out. Errors that could destroy your entire set of chips, resulting in billions of dollars in costs.

It isn't just about calculations, because even if calculated to a tee, is not a guarantee it will work because you are pushing boundaries on what is possible or what we know is possible. So there will be unknowns throughout. There is no guarantee that your calculations will translate 100% to reality. That in itself should kinda explain the risk imo. You simply cannot guarantee based on calculations alone that something boundarie pushing will work in reality even though the math worked out perfectly.

We know theory and practice don't precisely align in semiconductors. They live on the finnicky edge of quantum physics

Semiconductor devices books will have two charts next to each other. One telling you what the equation says the values should be and one showing you what the actual measured values tend to be. They can be off by >20% at times because exactly where in the silicon crystal that phosphorous atom landed matters a lot

They are, they started 10-15 years ago based on the results of work 20 years ago. You get the chip today. 9-14 years ago they got the results from the manufacturing 19 years ago and couldn't incorporate the changes into the the plans already in motion the previous year, though sometimes they can and you get internode improvements either in yeild or performance.

ASML is rumored to have spent $300 million and 5 years in developing extreme UV lithography

it is unbelievably hard to make it work and a factory cost +$10billion ...