The English common law said THAT?
Nor does it say that cops can't have someone sneak a bug into
someone's home without a warrant.

Thus the need to advance the definition of "unreasonable searches and
seizures" beyond the confines of the English common law in 1791.

I disagree. If it's unreasonable for a cop to enter your home without
permission, it's equally unreasonable to plant a bug or use infrared
without permission. However should change be required, the way to do
it is with a law or amendment, not judge-made law.

(And it would be pretty easy to defeat infrared searches, a bit of
metal over the walls and it doesn't get out of the house. A few rolls
of aluminum foil would do it, as would metal-backed insulation in the
walls and ceiling.)

It simply says (if I understand
correctly) that you need a warrant to search private homes etc. *

You understand incorrectly. The constitution merely speaks to
*unreasonable* searches and seizures. Searches and seizures with a
probable cause warrant a presumed reasonable but they are not the only
ones which are.

But still, there is no reason to believe that modern technology
changes the definition of unreasonable. The methods, yes, but not the
definition.

That
is any search, be it by physical entry or infrared. *The question is
if it is a search and if so is there probably cause.

Two excellent questions - neither of which is addressed by the 1791
English common law.

The term "search" is pretty well understood, now as it was in 1791.
Nor has the definition of "probable" changed.

In addition the forth amendment
clarified the need to get a warrant based on probable cause.
We can add "probable cause" to the list of constitutional imponderables.
I would like to see a number put on that. *At least 75% probable that
there is evidence etc. there before the warrant is issued. *Of course
that would require teaching some probability to cops and judges.
Just how would you presume to place a number on THAT.
What constitutes "75%" or whatever probability? However would you
compute that?
That's the sort of thing I can have lots of fun with.

But not in any real world situations.

Why can't a lawyer ask, "Officer, you say you had probable cause to
search my client's house. Just how probable was it that you would
find evidence there and how did you determine that probability?"

You do things
like determining witness reliability, or the probability that the tire
tracks at the scene. *Most likely you will have to calculate joint
probabilities.* *Not that difficult to do if you have a bit of
statistical knowledge.

That's not how "prudent and cautious" people operate in the real world.

A court of law is hardly reflective of most of the world.

And probable cause operates on the basis of such individuals, who are,
in almost all instances, NOT statisticians.

You don't have to be a statistician to understand the basic concepts
required for such calculations. In fact modern technology could help
here. It would be simple to produce a computer program to calculate
everything they need, you'd only have to help them understand the
concepts. For most people of average intelligence, a few hours (maybe
4-8) of class time would be more than adequate.