The Search for Life

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

[PhysicsGenius]

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.

Trolling in the park

[Doctor Fishboy]

A most excellent troll!

Thanks for making me smile, PhysicsGenius!

Re:SETI is a Black Hole

[TheGreenLantern]

So what your saying is that we should travel back in time to the 1940's, and stop all those first radio and television transmissions that had enough power to escape our solar system, since they have no chance of reaching ET?

Yes

[PhysicsGenius]

I have a newsletter regarding this idea if you would like to subscribe.

Re:Yes

[TheGreenLantern]

Your ideas sicken and confuse me, and I would like to subscribe to your newsletter. But only if it's a green one.

WRONG

[GPS Pilot]

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.

In which direction would the signal be deflected? The "mass behind it" will in most cases be roughly equally distributed in all directions. Therefore, the net deflection is negligible.

Furthermore, you're just plain wrong. The Hubble telescope has imaged [nasa.gov] galaxies more than 12 billion light years away [cnn.com]. So we know that the radius of your "tiny sphere" is at least 12 billion light years. That's probably a significant fraction of the entire universe, and plenty of territory for hunting for extraterrestrial signals.

Re:SETI is a Black Hole

[Gyver_lb]

Wrong!

1/ the Drake Equation only deals with our galaxy. It doesn't even pretend to give a fixed result. It's merely a statistical toy to play with.

2/ You assume that the total mass of the universe is above a certain value. You define the universe as a black hole. It's the never-ending search about the density of the universe, and the resulting conclusion : all time expanding or final collapsing of the known universe. But it does in no way interfere with our ability to send and receive signals to/from anywhere in the universe (although receiving something from a black hole is quiet difficult - nothing's impossible unless you prove you have perfect knowledge of all universe physics rules - but it's a corner case...) ...

Shortly, the tiny sphere you're describing either doesn't' exist or simply is the universe as we commonly define it.

Enough feeding the troll.

Bending Logic

[cybercreek]

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.

Re:Bending Logic

[Doctor Fishboy]

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.

For more information, have a look at my earlier post on this thread [slashdot.org]

Re:Bending Logic

[sinan]

To make this work, all you have to do is turn 90 degrees and the universe will look the same. Imagine a sphere centered at the observer and with a radius of "PhysicsGenius" All the light beams turn 90 degrees at the surface of the sphere all in the same direction and they appear as combed hairs tangent to the sphere everywhere on the spheres surface.

Sinan