Posted by
michael
on from the start-on-this-planet dept.
tanveer1979 writes "Space.com is carrying a very informative article about the "Arecibo Diaries" i.e. the search for Life outside. It explains all about the Arecibo telescope, the false alarms and all else."
SETI is a Black Hole
by
PhysicsGenius
·
· Score: 4, Interesting
As much as I'd like to believe in alien intelligence (and I do!) I
can't hold still for mathematical abuses such as the infamous Drake
Equation. To take one example:
One of the assumptions that Drake built in is that a signal of
sufficient strength can travel arbitrarily far. This simply isn't so.
Einstein himself showed nearly a century ago that spacetime is bent
back on itself in the presence of gravitational force. For an object
the size of a planet the effect is minor (except for the inhabitants,
ha ha) but even something as relatively puny as our sun can deflect a
beam of light measurably.
The point of this is that a signal will only propagate outwards until
the total mass behind it exceeds a critical value (the location of
this is called the "event horizon" in an analogy to black holes). At
that point its deflection will equal more than 90 degrees...i.e. it
will not go any farther from its point of origin.
Sending signals outward is useless unless we expect to find
intelligence within the tiny (universally speaking) sphere defined by
this event horizon. And, via symmetry, we can prove that listening
for signals from other solar systems is useless for the same reason.
The money spent on SETI would do better on something mathematically
possible, like NASA's attempts to create an anti-gravity device.
Bending Logic
by
cybercreek
·
· Score: 5, Insightful
Assuming the post is true, they why do we see the light from galaxies over 10 billion light years away? Surely the "light horizon" would prevent that. And if light is bent 90 degrees, them that would only direct us to see them as being in "front" of us. But we would still see them. Seems to be something missing in the argument. Please explain what evidence exists for the "light horizon" from non black hole sources.
Interesting idea though. Needs some evidence.
Ah, but what you are forgetting is that if you look at 90 degrees to the *right* of the covariant space-time metric, the Riemann tensors that describe PhysicsGenius' metric can be seen to trivially allow light from MANY times the event horizon distance to reach your observable cone.
It is a matter of simple algebra and some unique insight to get a recursive solution for Hubble length closed universes.
Slashdot Mirror
One of the assumptions that Drake built in is that a signal of sufficient strength can travel arbitrarily far. This simply isn't so. Einstein himself showed nearly a century ago that spacetime is bent back on itself in the presence of gravitational force. For an object the size of a planet the effect is minor (except for the inhabitants, ha ha) but even something as relatively puny as our sun can deflect a beam of light measurably.
The point of this is that a signal will only propagate outwards until the total mass behind it exceeds a critical value (the location of this is called the "event horizon" in an analogy to black holes). At that point its deflection will equal more than 90 degrees...i.e. it will not go any farther from its point of origin.
Sending signals outward is useless unless we expect to find intelligence within the tiny (universally speaking) sphere defined by this event horizon. And, via symmetry, we can prove that listening for signals from other solar systems is useless for the same reason. The money spent on SETI would do better on something mathematically possible, like NASA's attempts to create an anti-gravity device.
Assuming the post is true, they why do we see the light from galaxies over 10 billion light years away? Surely the "light horizon" would prevent that. And if light is bent 90 degrees, them that would only direct us to see them as being in "front" of us. But we would still see them. Seems to be something missing in the argument. Please explain what evidence exists for the "light horizon" from non black hole sources. Interesting idea though. Needs some evidence.
A most excellent troll!
Thanks for making me smile, PhysicsGenius!
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