[ExI] Von Neumann Probes

[Keith Henson]

I think we might have seen a Dyson patch around Tabby's star.  From
the size and time of the 22% dip, you can calculate that the object is
509 times the area of the Earth, and the velocity, which gives you the
orbit. I posted the math here a few years ago.

There are about 20 dipping stars in a 1000 light-year radius around
Tabby's star.  If the blinking is due to aliens and the AI estimate of
3000 years for them being in space, then the spread out is 1/3rd of c.

Keith

On Sun, Jan 25, 2026 at 9:14 AM spike jones via extropy-chat
<extropy-chat at lists.extropy.org> wrote:
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> From: extropy-chat <extropy-chat-bounces at lists.extropy.org> On Behalf Of Jason Resch via extropy-chat
> Subject: Re: [ExI] Von Neumann Probes
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> On Sun, Jan 25, 2026, 11:28 AM spike jones via extropy-chat <extropy-chat at lists.extropy.org> wrote:
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>  From: John Clark <johnkclark at gmail.com>
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> Do offer a mathematically based refutation to my conclusion that any millimeter scale von Neumann probe at anywhere near .01C is completely impossible, regardless of any plausible future materials breakthroughs.  I might buy the notion of a micro-C however…  What’s the big hurry?...spike
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> Aren't there proposals in which an ionizing laser is shot forward of the craft and then magnetic fields are used to steer those charged particles out of the craft's path? I don't know how practical this is, but it might avoid the erosion problem.
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> Jason
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> Hi Jason,
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> Some calculations in mechanical engineering are wildly complicated, such as shock wave mechanics.  But as velocities get sufficiently high, the calculations get simpler again, because some factors at the velocities at we are accustomed become increasingly irrelevant.  Example: if the relative speed in a collision get high enough, the chemical bonding energy in the material doesn’t matter: that energy is completely dominated by the energy of collision.  At really high speeds, anything anywhere near a milli-C, all we really need to understand are two fundamental concepts: conservation of energy and conservation of momentum.  Never mind the subtleties of shock waves, entropy, and such.  Just the two conservation concepts are all ya really need.
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> If we get in too much of a hurry with our interstellar probes and insist that they arrive at the nearest stars in under several tens of thousands of years, it doesn’t matter what the probe is made of, or if we can get stuff out of the way ahead of us.
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> On the notion of ionizing lasers and magnetic fields, we can estimate the energy required to create the field or laser and see that the notion is impractical, considering we must transfer momentum and energy from us to whatever is in our way.  That momentum and energy must come from somewhere.
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> spike
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