could we shine a laser on this new solar system and detect something in 180 years?

"Tony Rusi" wrote in the subject line for some reason "could we shine a laser on
this new solar system and detect something in 180 years?"
http://news.independent.co.uk/world/...p?story=421468

Hmm, let's try it out ...

*shines laser*

Waits ...
...
...
...
...
...
...

Aha! Something's coming back ...
"Oi! Turn that light off, some of us are trying to sleep over here, you know!"

Tony Rusi wrote:
http://news.independent.co.uk/world/...p?story=421468

No.
The brightest lasers around would be detectable only with sensitive instruments
at this distance.
The reflection would be so dim that I'd be surprised if a photon a second
would pass through our solar system.

--
http://inquisitor.i.am/ | | Ian Stirling.
---------------------------+-------------------------+--------------------------
Get off a shot FAST, this upsets him long enough to let you make your
second shot perfect. -- Robert A Heinlein.

(Tony Rusi) writes:

could we shine a laser on this new solar system and detect something in
180 years?

http://news.independent.co.uk/world/...p?story=421468

No, unless a technological civilization MUCH more advanced than ours
happens to live there, is looking for laser light, and happens to have a
MUCH bigger laser system than we can currently build properly positioned
to shine a beam back at us.

Lasers still obey the inverse sqaure law beyond the diffraction-limiting
distance of their focusing aperture. It would take a HUGE lens system
thousands of kilometers in diameter stationed at the edge of the solar
system to hold a laser beam reasonable tight over interstellar distances,
and a VERY powerful laser before it will be easily noticed against the
much brighter background light that the Sun produces.


-- Gordon D. Pusch

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We can't even shine a laser on Pluto from Earth and get
a return. This Solar System is roughly a kajillion (to
use a technical term) times farther away.

So no.

Gordon D. Pusch wrote:
(Tony Rusi) writes:

could we shine a laser on this new solar system and detect something in
180 years?

http://news.independent.co.uk/world/...p?story=421468

No, unless a technological civilization MUCH more advanced than ours
happens to live there, is looking for laser light, and happens to have a
MUCH bigger laser system than we can currently build properly positioned
to shine a beam back at us.

Lasers still obey the inverse sqaure law beyond the diffraction-limiting
distance of their focusing aperture. It would take a HUGE lens system
thousands of kilometers in diameter stationed at the edge of the solar
system to hold a laser beam reasonable tight over interstellar distances,
and a VERY powerful laser before it will be easily noticed against the
much brighter background light that the Sun produces.

Not quite that big.
I suspect you've read (or calculated) the needs for a laser pushed sail.

Talking near-term, and assuming you are using an OWL class 100m mirror
scope for the transmitter.
Say 100 light years.
This is 3*10^9 light seconds away.

The above scope will produce a beam with a divergance of around 1*10^-8
radians.
This will produce a beam with a diameter of 30 light seconds at the
target star, so you will need to point it at a planet.

The sun produces around 1400W into 1m^2 at around 500 light seconds.
This will be (6*10^7)^2 dimmer at the target star, or 4*10^15 times dimmer,
for a power of 6*10^-12W/m^2.

The beam area is around 1*10^20m^2, to equal the suns power into this
area needs a laser with power of 600Mw.

The largest current continuous wave lasers are around a megawatt or so,
which would be trivially detectable by even primitive spectroscopy.

To get something naked-eye visible needs a bit more (assuming for the
sake of argument the naked eyes are similar to ours)

It'd be a large engineering project, but something that could be done
essentially now, given funding, without much development of much actual
new stuff.

It does not for example require the large space-based manufacturing
industry, that laser-pushed sails probably do.

As to data transmission, that gets lots easier once someone is actually
pointing a large dish your way.


--
http://inquisitor.i.am/ | | Ian Stirling.
---------------------------+-------------------------+--------------------------
"I am the Emperor, and I want dumplings." - Austrian Emperor, Ferdinand I.

"Christopher M. Jones" wrote in message ...
We can't even shine a laser on Pluto from Earth and get
a return. This Solar System is roughly a kajillion (to
use a technical term) times farther away.

So no.


Has anyone else tried Gunter Nimtz's method over a longer distance?

Yet last month an extraordinary development in this tale unfolded at a
special colloquium organised in Snowbird, Utah. Attending the meeting
were some of the leading researchers in this field of
faster-than-light quantum phenomena. To an astonished audience, Nimtz
announced that his team at Cologne had not only measured superluminal
speeds for their microwaves, but had actually sent a signal faster
than light. The signal in question was Mozart's 40th Symphony. What
they did was frequency modulate their microwave source with the music
and then measure how quickly the music arrived after traversing the
forbidden zone in a waveguide. According to Nimtz, Mozart's 40th
hopped across 12 centimetres of space at 4.7 times the speed of light.
What's more, Nimtz actually had a recording to prove it. To his now
bemused audience, he played a tape in which among the background hiss
strains of Mozart could be heard. This was the "signal" that had
travelled faster than light. But that very word "signal" triggered
heated discussion, with some participants claiming that the symphony
could not be regarded as a signal. Among them was Chiao. "It's not a
signal in Einstein's sense because of the timescales involved. I agree
that when the music crosses the barrier it is shifted forward in time,
compared with music that travels by a conventional path, but only by a
very small amount. It is so small that you can predict what will
happen to the music simply by looking at how the original audio
waveform is changing. There is no threat to causality." Nimtz is not
so sure. "I don't have an opinion on whether this violates causality.
However, I do not accept that Mozart's symphony isn't a signal. In
principle, I could extend the path over much longer distances and then
it would not be possible to predict the course of the music. Then you
really would have a signal travelling faster than light." Nimtz
clearly believes he is onto something important. By contrast, Chiao
and his colleagues, while happy to peer beyond the normal confines of
scientific orthodoxy, are determined not to be lured over the edge.
Their collective view remains firmly grounded in the sanctity of
causality and Einstein's special theory of relativity. "Einstein
causality," Chiao says, "rules out the propagation of any signal
faster than light, but it does not limit the group velocity of
electromagnetic propagation." Chiao's colleague Steinberg puts it
another way: "What stops you from sending a signal faster than light
is that the calculation only works for smoothly varying pulses. If a
smoothly varying pulse shows up at noon, it may have been possible to
predict its shape from the shape of the pulse at 8 am. If at noon you
suddenly have an important message and decide to change the shape of
the pulse in order to convey this message, that change will not travel
any faster than the speed of light." Despite such reassurances, many
physicists admit to being more than a little troubled by these faster
than light phenomena. While few are prepared to accept Nimtz's more
extravagant claims, many will doubtless want to see how much further
theory and experiment can fly in the face of common sense.

(Tony Rusi) writes:

"Christopher M. Jones" wrote in message ...
We can't even shine a laser on Pluto from Earth and get
a return. This Solar System is roughly a kajillion (to
use a technical term) times farther away.

So no.


Has anyone else tried Gunter Nimtz's method over a longer distance?

Yet last month an extraordinary development in this tale unfolded at a
special colloquium organised in Snowbird, Utah. Attending the meeting
were some of the leading researchers in this field of
faster-than-light quantum phenomena. To an astonished audience, Nimtz
announced that his team at Cologne had not only measured superluminal
speeds for their microwaves, but had actually sent a signal faster
than light.

More careful analysis showed that they were using an invalid definition
of "signal velocity," and that the signal traveled slower than light,
in perfect consistency with Einstein Causality and Special Relativity.



[...] "Einstein causality," Chiao says, "rules out the propagation of any
signal faster than light, but it does not limit the group velocity of
electromagnetic propagation."

The first half of Chiao's statement is correct. The second half is wrong.

Furthermore, it is not even the "group velocity" that the correct
definition of "signal velocity" in a dispersive medium --- a fact
that later bit Chiao in the @$$ when he published his "gain-assisted
FTL propagation" claim a few years later. The _correct_ defition of
"signal velocity" is the "front velocity" --- as alluded to in your
following quote from Steinberg:

Chiao's colleague Steinberg puts it another way: "What stops you from
sending a signal faster than light is that the calculation only works
for smoothly varying pulses. If a smoothly varying pulse shows up at
noon, it may have been possible to predict its shape from the shape of
the pulse at 8 am. If at noon you suddenly have an important message and
decide to change the shape of the pulse in order to convey this message,
that change will not travel any faster than the speed of light."

It is the propagation og the "sudden change in shape" (the "wavefront")
that defines the "signal velocity," as shown by Sommerfeld a Century ago ---
and the velocity of the wavefront can be rigorously shown to be bounded
by lightspeed in =ANY= medium that has a causal frequency response ---
i.e., any medium that cannot say "ouch" until _after_ you kick it.


-- Gordon D. Pusch

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In article ,
Tony Rusi wrote:
Has anyone else tried Gunter Nimtz's method over a longer distance?

While the distance can be extended in principle, it's nothing so simple
as just buying a longer pipe.

Moreover, as I understand it -- with the caution that this is an area I
*don't* keep up with -- Nimtz et al did *not* actually measure the speed
of propagation, in any sense that physicists in general acknowledge as
measurement. Rather, he demonstrated transmission of a signal through a
path whose speed, given certain assumptions, is *calculated* to be faster
than light. But the path is very noisy and the difference between the
speed of light and the calculated speed is a fraction of a nanosecond, so
actually confirming the calculation is exceedingly difficult, and he is
currently pretty much alone in believing it.

Note that in any case, this trick only works within a waveguide -- it is
not something you could use to signal across open space.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

(Henry Spencer) wrote in message ...
In article ,
Tony Rusi wrote:
Has anyone else tried Gunter Nimtz's method over a longer distance?

Note that in any case, this trick only works within a waveguide -- it is
not something you could use to signal across open space.

That particular trick isn't, but there are others (not yet tested in
hardware), which potentially do.

The whole field of "apparent FTL" systems is interesting and, I
personally believe, ripe for further work. There's about five
different systems where different investigators have reported
intriguing results, with very different physics but very
similar underying mathematics -- propogation beyond cutoff.

----------------------------------------------------------------
"Limited funds are a blessing, not Jeff Greason
a curse. Nothing encourages creative President & Eng. Mgr.
thinking in quite the same way." --L. Yau XCOR Aerospace
www.xcor.com

(Henry Spencer) writes:

In article ,
Tony Rusi wrote:
Has anyone else tried Gunter Nimtz's method over a longer distance?

While the distance can be extended in principle, it's nothing so simple
as just buying a longer pipe.

Moreover, as I understand it -- with the caution that this is an area I
*don't* keep up with -- Nimtz et al did *not* actually measure the speed
of propagation, in any sense that physicists in general acknowledge as
measurement. Rather, he demonstrated transmission of a signal through a
path whose speed, given certain assumptions, is *calculated* to be faster
than light.

....Make that _mis-calculated_ to be "faster than light," since the
assumptions he used are _PROVABLY WRONG_. A physically correct calculation
shows that the actual signal velocity was indeed slower than light, and
that Nimtz's experiment was entirely consistent with Einstein Causality
and Special Relativity.


But the path is very noisy and the difference between the
speed of light and the calculated speed is a fraction of a nanosecond, so
actually confirming the calculation is exceedingly difficult, and he is
currently pretty much alone in believing it.

Note that in any case, this trick only works within a waveguide -- it is
not something you could use to signal across open space.

....Actually, it doesn't even work in a waveguide, since both Nimtz's
assumptions and his method for calculating signal velocity are wrong.


BTW, Greg Egan has a very nice Java Applet demonstrating why both Nimtz and
Wang et al were in error when they claimed they'd achieved "FTL signaling"
at http://gregegan.customer.netspace.net.au/APPLETS/20/20.html


-- Gordon D. Pusch

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