Focal length of Sun's gravitational lens

I have been thinking this through quite hard, but I got nowhere

I know that stars and nebulae close to the solar disk in the sky get
warped in their position because general relativity dictates that the
Sun's gravitational field can perturb the path of the rays. But the
question I have is can the Sun's gravitational field act as a
magnifier to focus more of the light from stars onto the earth? Does
the Sun's gravitational lens have a focal length of 1 astronomical
unit? If so how many degrees does a star have to be within from the
center of the solar disk in order for its magnified image to be
focused upon the Earth?

I'd really apprecite any advice to me. Cordially invited replies.
Thank you! Thank you! )

On Mar 6, 4:31*pm, wrote:
I have been thinking this through quite hard, but I got nowhere

I know that stars and nebulae close to the solar disk in the sky get
warped in their position because general relativity dictates that the
Sun's gravitational field can perturb the path of the rays. But the
question I have is can the Sun's gravitational field act as a
magnifier to focus more of the light from stars onto the earth? Does
the Sun's gravitational lens have a focal length of 1 astronomical
unit? If so how many degrees does a star have to be within from the
center of the solar disk in order for its magnified image to be
focused upon the Earth?

I'd really apprecite any advice to me. Cordially invited replies.
Thank you! Thank you! )

There are two other people around here from the UK, I am not one of
them.

92 percent opposed the Iraq war, and over time that number moved
sharply
toward 100 percent, currently at 99.9 percent and 0.1 percent are
still playing
secret government crab and CCTV Der Kommissar. Is it for the
government?
I poop in your society's big brother.

On Fri, 06 Mar 2009 15:31:18 -0800, deloitetouche wrote:

I have been thinking this through quite hard, but I got nowhere

I know that stars and nebulae close to the solar disk in the sky get
warped in their position because general relativity dictates that the
Sun's gravitational field can perturb the path of the rays. But the
question I have is can the Sun's gravitational field act as a magnifier
to focus more of the light from stars onto the earth? Does the Sun's
gravitational lens have a focal length of 1 astronomical unit? If so how
many degrees does a star have to be within from the center of the solar
disk in order for its magnified image to be focused upon the Earth?

I'd really apprecite any advice to me. Cordially invited replies. Thank
you! Thank you! )

(Comments to trolls included in parentheses.)

You can figure this out from observational data and very simple math
without ever invoking any of Einstein's reasoning. (This allows us to
avoid yet another damn' 100-post long flamewar. Not that I think that
will happen.)

To begin with, its focal length will vary depending on how far the light
passes from the center of the Sun, because a lightray passing near the
Sun will be deflected more than one passing it farther away. That is to
say, the focal length will be shorter for light passing the Sun's limb
than for light passing it at a greater distance from its center.

That is, a gravity well is pretty much a non-imaging lens.

Next, the focal length of a lens is the harmonic mean of the distance
from the object being imaged to the virtual image which the lens forms.
For an object at a very great distance, the distance to the virtual image
approaches the focal length.

Finally, observations during Solar eclipses tell us the angle by which
starlight passing the Sun's limb is deflected. (Again, guys, actual,
repeated observations made by actual people with perfectly good
telescopes, so let's not have a lot of horse**** about how gravity can't
possibly deflect light.)

So...

Look up the aforementioned angle. You can find the number on myriad Web
sites.

Then do a little trigonometry: find the height of a right triangle whose
base is the radius of the sun and whose other base angle is 90 degrees
minus the starlight's deflection angle.

If you don't know trig, many math Web sites will have a diagram of a
similar situation captioned with the appropriate formula.

The height of this triangle is the focal length of that part of the Sun's
gravity well near its surface.

If you dig around some you may even find deflection angles for greater
distances from the Solar limb. They will be smaller, so the triangle
will be taller, hence the focal length at that radius from the Sun's
center will be longer.

Dear deloitetouche:

wrote in message
...
....
I know that stars and nebulae close to the solar disk
in the sky get warped in their position because
general relativity dictates that the Sun's gravitational
field can perturb the path of the rays.

GR does not dictate that. GR describes what Nature does.

But the question I have is can the Sun's
gravitational field act as a magnifier to focus more
of the light from stars onto the earth?

No. The most that gravity can do for any mass, is create
Einstein rings, and they are not specular images.

....
I'd really apprecite any advice to me. Cordially
invited replies. Thank you! Thank you! )

In the case of the Sun, you'd have to crush it down to below a
neutron star's diameter so that the Einstein rings would be
outside matter. Otherwise, all you get is a displaced image.

David A. Smith

wrote:

I have been thinking this through quite hard, but I got nowhere

I know that stars and nebulae close to the solar disk in the sky get
warped in their position because general relativity dictates that the
Sun's gravitational field can perturb the path of the rays. But the
question I have is can the Sun's gravitational field act as a
magnifier to focus more of the light from stars onto the earth? Does
the Sun's gravitational lens have a focal length of 1 astronomical
unit? If so how many degrees does a star have to be within from the
center of the solar disk in order for its magnified image to be
focused upon the Earth?

I'd really apprecite any advice to me. Cordially invited replies.

Try a star with greater mass .... much greater mass.
Much much much much greater mass. Concentrate on
mass. The answer is in mass.




Thank you! Thank you! )

In article ,
wrote:
I have been thinking this through quite hard, but I got nowhere

I know that stars and nebulae close to the solar disk in the sky get
warped in their position because general relativity dictates that the
Sun's gravitational field can perturb the path of the rays. But the
question I have is can the Sun's gravitational field act as a
magnifier to focus more of the light from stars onto the earth? Does
the Sun's gravitational lens have a focal length of 1 astronomical
unit?

:-) .... no! Any "focal length" would be more like a hundred
thousand to a million astronomical units, i.e. several light years.

Also, the "gravitational lens" of the Sun (or any other large mass)
doesn't qork quite like an optical lens. On an optical lens the deflection
is larger further away from the optical axis all the way out to the rim
of the lens. It must be that way, or else parallell light would not be
refracted into a single focal point.

In the case of the Sun (or any other large mass), the deflection is
larger the closer to the Sun's surface the light ray passes. And
there is no well-defined "rim" of the "lens" - the deflection just
drops off continuously the further away from the Sun the light ray
passes. This also means that this "lens" has no well-defined focal
length.

If so how many degrees does a star have to be within from the
center of the solar disk in order for its magnified image to be
focused upon the Earth?

I'd really apprecite any advice to me. Cordially invited replies.
Thank you! Thank you! )


--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stjarnhimlen dot se
WWW: http://stjarnhimlen.se/

In article ,
jerry warner wrote:


wrote:

I have been thinking this through quite hard, but I got nowhere

I know that stars and nebulae close to the solar disk in the sky get
warped in their position because general relativity dictates that the
Sun's gravitational field can perturb the path of the rays. But the
question I have is can the Sun's gravitational field act as a
magnifier to focus more of the light from stars onto the earth? Does
the Sun's gravitational lens have a focal length of 1 astronomical
unit? If so how many degrees does a star have to be within from the
center of the solar disk in order for its magnified image to be
focused upon the Earth?

I'd really apprecite any advice to me. Cordially invited replies.

Try a star with greater mass .... much greater mass.
Much much much much greater mass. Concentrate on
mass. The answer is in mass.

No known stars have a large enough mass - you'd need a heavy black
hole for that to happen. And if a large enough black hole would
somehow replace the Sun, then the Earth would be in trouble....



Thank you! Thank you! )



--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stjarnhimlen dot se
WWW: http://stjarnhimlen.se/

On Mar 6, 4:31*pm, wrote:
I have been thinking this through quite hard, but I got nowhere

I know that stars and nebulae close to the solar disk in the sky get
warped in their position because general relativity dictates that the
Sun's gravitational field can perturb the path of the rays. But the
question I have is can the Sun's gravitational field act as a
magnifier to focus more of the light from stars onto the earth? Does
the Sun's gravitational lens have a focal length of 1 astronomical
unit? If so how many degrees does a star have to be within from the
center of the solar disk in order for its magnified image to be
focused upon the Earth?

I'd really apprecite any advice to me. Cordially invited replies.
Thank you! Thank you! )

There are two other people around here from the UK, I am not one of
them.

92 percent opposed the Iraq war, and over time that number moved
sharply
toward 100 percent, currently at 99.9 percent and 0.1 percent are
still playing
secret government crab and CCTV Der Kommissar. Is it for the
government?
I poop in your society's big brother.

Suck Ceausescu buttcrack. I am watching you English.

On Mar 6, 4:31*pm, wrote:
I have been thinking this through quite hard, but I got nowhere

I know that stars and nebulae close to the solar disk in the sky get
warped in their position because general relativity dictates that the
Sun's gravitational field can perturb the path of the rays. But the
question I have is can the Sun's gravitational field act as a
magnifier to focus more of the light from stars onto the earth? Does
the Sun's gravitational lens have a focal length of 1 astronomical
unit? If so how many degrees does a star have to be within from the
center of the solar disk in order for its magnified image to be
focused upon the Earth?

I'd really apprecite any advice to me. Cordially invited replies.
Thank you! Thank you! )

There are two other people around here from the UK, I am not one of
them.

92 percent opposed the Iraq war, and over time that number moved
sharply
toward 100 percent, currently at 99.9 percent and 0.1 percent are
still playing
secret government crab and CCTV Der Kommissar. Is it for the
government?
I poop in your society's big brother.

Suck Ceausescu buttcrack. I am watching you English.

This is not racist South Africa where people can be institutionally
followed.

CCTV cameras allow use of remote control to follow people on one's
home
television set through networked CCTV cameras.

****ing fascists. Anne's Clar Der Kommissar.

On Mar 6, 4:31*pm, wrote:
I have been thinking this through quite hard, but I got nowhere

I know that stars and nebulae close to the solar disk in the sky get
warped in their position because general relativity dictates that the
Sun's gravitational field can perturb the path of the rays. But the
question I have is can the Sun's gravitational field act as a
magnifier to focus more of the light from stars onto the earth? Does
the Sun's gravitational lens have a focal length of 1 astronomical
unit? If so how many degrees does a star have to be within from the
center of the solar disk in order for its magnified image to be
focused upon the Earth?

I'd really apprecite any advice to me. Cordially invited replies.
Thank you! Thank you! )

There are two other people around here from the UK, I am not one of
them.

92 percent opposed the Iraq war, and over time that number moved
sharply
toward 100 percent, currently at 99.9 percent and 0.1 percent are
still playing
secret government crab and CCTV Der Kommissar. Is it for the
government?
I poop in your society's big brother.

Suck Ceausescu buttcrack. I am watching you English.

This is not racist South Africa where people can be institutionally
followed.

CCTV cameras allow use of remote control to follow people on one's
home
television set through networked CCTV cameras.

****ing fascists. Anne's Clar Der Kommissar.

Everybody in entire Europe who mention current politics and New
Direction
mention the UK based CCTV in their first sentence.

Don't you hate your ****ing Nazi country? I told East Germans
before the wall came down, I tell you.

East Germans were silent. I told them.