3I/ATLAS: Probably NOT an alien interstellar probe

[pood]

He must realize that he can end up looking like a fool? So why risk it? Because he thinks the pay-off would be huge if he is right?

What are the odds?

Because it’s clickbait and somewhere downstream he is making money. Those people who tell you the world is going to end on such and such a date suffer no penalty for being proven wrong. They just move on to the next date. And keep their fan base.

 

[pood]

Basically I think Loeb is like a religious leader or a cult leader, like Trump. He tells people what they want to hear, and can never be proven wrong.

 

[DBT]

I suppose there is always a rationale for failure. Nobodies fault....next event please.

 

[steve_bank]

Wow, I just figured it out.

ET in orbiting in invisible spaceships are on the net posting on the forum.

That explains a lot.

 

[Loren Pechtel]

No, the point is there is no possible suspension as you can only transmit the force at the speed of sound.

Yet you can continuously apply 16000 gs to a tardigrade for a full minute without killing it?

No idea on the g-tolerance of a tardigrade, but what's the relevance? I'm talking about speed, not acceleration. Your 16,000g is unquestionably from a centrifuge, it's just going round and round, not smacking the atmosphere.

 

[Loren Pechtel]

The maximum velocity increase achievable relative to the Sun, by gravitational slingshot from a planet, is twice the planet's orbital velocity. So the best you can do in the Solar System with a single manoevre is about 96km/s (twice the orbital velocity of Mercury).

Each slingshot manoevre is effectively a perfectly elastic 'bounce', transferring momentum to your spacecraft from tne planet. As far as I can see, if you have infinite time for the task, you could keep doing such manoevres until you have stolen all of the momentum from everything in the Solar System, and all the planets have fallen into the Sun.

Your final velocity would be huge in such a scenario; although your accelerations would get very small as your probe's mass increased due to its speed. You should achieve a sizable fraction of c for any probe with a reasonable rest-mass.

Two problems:

1) They're not in the right place to do this.

The setup in the question assumes that we can wait until they are, however long that takes.

2) While in theory you could get 96km/sec out of Mercury look at the periapsis. It's way, way below the surface.

Sure, but we are looking for an upper bound to the achievable velocity relative to the Sun. Some assumptions are justified, such as treating planets as point masses. It's not like I am asking you to consider a spherical planet in a vacuum...

Moo!

Tables exist for the maximum velocity that can be obtained from the various planets.

 

[Elixir]

No idea on the g-tolerance of a tardigrade, but what's the relevance? I'm talking about speed, not acceleration.

Speed isn’t an issue. You don’t mind going 500+ mph in a plane because the rate of your acceleration is gradual. If you were simply placed in the way of the plane while it was going 500+ mph, you’d get “smacked” by your instant acceleration from zero to 500. In fact you’d be pizza. Not from the speed, from the acceleration.

Same deal with imbedding a terrestrial object in a fast moving interstellar object - it ain’t the speed that will get you, it’s the acceleration, aka getting “smacked”. Surviving the impact means reducing the G forces of acceleration.

It’s NOT about the speed (until you get to relativistic speeds). Kinda like how falling from great heights won’t kill you, the rapid deceleration upon impact will.