There is a theory named after a man that states that something is changed by observing it. What is this called

Answer 1

Heisenburg's uncertainty principle.

Answer 2

THE THEORY IS NAMED AFTER THAT MAN????

UHMM... DON'T KNOW BOUT THAT BUT I KNOW THE THEORY..

YOUR CAN READ ABOUT SCHROEDINGER'S CAT...
Schrödinger wrote:

One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small, that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.
It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation. That prevents us from so naively accepting as valid a "blurred model" for representing reality. In itself it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.

ONE CANNOT KNOW THE STATE OF A BODY UNLESS IT IS OBSERVED....
TO OBSERVE OS TO "MEASURE"...
AND ONE CAN NEVER KNOW OR MEASURE THE ORIGINAL (AS IN) ORIGINAL STATE OF THAT BODY...
GOT IT?

Answer 3

Often attributed to Heisenberg, but his uncertainty principle doesn't really pertain to this issue. It's a general principle of quantum mechanics. The state of a system can only be described in terms of probabilities of outcomes of certain measurements. When you measure a system, the probabilities collapse to 100% (for the value you got) and a bunch of 0%'s (for all the values you could have got, but didn't).

Heisenberg's uncertainty principle was a mathematical formula which talked about how some pairs of variables (non-commutable pairs) can't be known at the same time with infinite precision.

The snappy name his principle was given has lead to many popular misconceptions about it (e.g., according to Heisenberg, you can never be sure of anything).

Answer 4

Roadkill's right.

http://www.aip.org/history/heisenberg/