Evidently not at least while I’m on my phone. Some urls have a format that fools Discourse’s gizmo that generates preview boxes.
On a pc I could fiddle with it enough to succeed maybe.
So, no pushing negaspheres with tractor beams.
How could you be so wrong, “Doc” Smith?
We’ve had experimental evidence for a long time. It’s nice that the new experiments agree with the old ones, but it’s hardly shocking.
And @gnoitall , Doc Smith’s negaspheres were always a weird conflation of the notions of negative mass, antimatter, and black holes. Though I do admire the sheer chutzpah in describing the interaction between a planet and a planet-sized negasphere as resulting in nothing but “a gentle puff of gamma rays”.
I’ll bet the answer is somewhere in the physics of inertialess mass that allows FTL travel without any pesky “jumps” or “wormholes”.
Who is Doc Smith, what’s a Negasphere, and how did Doc Smith get one the size of a planet?
E. E. Smith, author of the Lensman books, classics of space opera science fiction. And also (indirectly) the origin of Qadgop the Mercotan.
Smith pretty much invented the concept “space opera”. The Lensman series came in second place for the Hugo award for best all time sci-fi series (lost to Asimov’s Foundation series).
Sorta Gharlane of Eddore’s farts.
Oh, I thought we were talking about a different Doc Smith.
Oh, the pain! The pain!
Hey, my creator did the best he could with the science of the time. He started writing that stuff in 1919 after all. That’s also the year he got his chemical engineering Ph.D.
“Qadgop the Mercotan slithered flatly around the after-bulge of the tranship. One claw dug into the meters-thick armor of pure neutronium, then another. Its terrible xmex-like snout locked on. Its zymolosely polydactile tongue crunched out, crashed down, rasped across. Slurp! Slurp! At each abrasive stroke the groove in the tranship’s plating deepened and Qadgop leered more fiercely. Fools! Did they think that the airlessness of absolute space, the heatlessness of absolute zero, the yieldlessness of absolute neutronium, could stop QADGOP THE MERCOTAN? And the stowaway, that human wench Cynthia, cowering in helpless terror just beyond this thin and fragile wall…”
BTW, Cynthia (the Mrs.) and I are still together!
I’m glad she appreciates that you consider her worth the effort to rasp-slurp your way through centimeters (I guess) of neutronium to get to her.
The point about “negaspheres” is that Smith’s Lensman stories envisioned a substance called negative matter which would annihilate an equal mass of normal matter. (Possibly influenced by the discovery of real-life antimatter in contemporary physics.)
Negaspheres were simply spheres of assorted sizes (from fist-size to whole planets) of negative matter.
However, negative matter was always pitch black. More relevantly, it had negative mass, so reacted to gravity opposite to the behavior of normal matter.
“Tractor beams” were another Smith invention, and were beams of force that could attract, grasp, or repel matter. (They’re pretty much ubiquitous in SF now.)
The anti-mass phenomenon of a negasphere also affected tractor beams: the attraction setting of a tractor beam actually repelled a negasphere, and switching a tractor beam to repel a negasphere would draw it to you.
That was a lot of off-topic setup for a dumb joke; I apologize for it. I know we have a lot of E. E. “Doc” Smith fans in the community, but that doesn’t really justify an “inside joke” based on 75-year-old space opera tropes.
We return you now to our regularly scheduled real-life physics discussion.
Of course it justifies such a joke! It enabled us to fight ignorance and raise awareness about space operas and for me to pointlessly pontificate on precious pearls of prescience. Or something.
OK, carry on with physics then.
This from the Times (unpaywalled) seems to answer the OP: https://www.nytimes.com/2023/09/27/science/physics-universe-antimatter.html?unlocked_article_code=g0-4d_68hpj7-_dlDJIkIzkK9qZkVYq4nnLeV6ZptAzcEawra4Ue8rfD4as5IXbDsFhClnsGTRzVKXkv9JM1AlZR88pii1u_xSRJ9imsWz2N-kBpqATGypoTyToxSj9PeWWk2UvzHEtlfkil3VJhKrZyf7b_qvx4AwL8T1s_xq667UkADslLxnhWKv70Z_VE21NubUmW7WnPQGktjnsENZu-VzyIH3_PWl-vXrITZb5BO3jrVoykM0bfZNSvNwWNi2VjREOTI_9eIPzsp7er5Xfwb3Z9IYqH0SN0E-3XLaSb6sOeWAFcM3rBkuxjSMsBnULacuF67x1rb8uvDHSoquq7XbxJ&smid=url-share
Bottom line: anti-hydrogen atoms (anti-atoms?) fall in a gravitational filed at the same rate as hydrogen atoms.
Or this article too:
(Result of Post#9 experiment?)
I noticed that the 2017-era discussion upthread included a link to a post from 2014, but that that link doesn’t work after the migration of the forum’s backend. The updated link is here, in case anyone is trying to follow the 2017-era discussion. (The linked 2014 post also has now-broken links, but I didn’t try to figure those out.)
Yes, where is Bergenholm when we need him?
Or I’d settle for a spindizzy.
Who cares about those silly old-fashioned conservation laws, anyway?
And of course speculate upon the whichness of the why. Sir Austin Cardinge would understand, of course.
I suspect few, if any physicists ever thought that antimatter would behave differently to gravity. Antimatter is just matter, and there is nothing in General Relativity that distinguishes types of matter/energy. It’s just unfortunate that someone back in the day happened to choose the prefix “anti”, which gives lay folk (and SF writers) the impression that these particles are bizarro, opposite-matter.
Absolutely. Relativity has survived all the experimental and observational tests we have been able to do as far as I know.
Still, as Feynman said, “nature is what she is”; it is as well that we did the check.
And it’s I think still not quite sure from the experimental data that the gravitational effect is exactly the same (though we all expect that’s just measurement uncertainty and will be resolved with better equipment).
But then towards the end of the 19th century physicists like Lord Kelvin were saying there is nothing much more to be done in physics: just add a few more decimal points to the measurements…
This past weekend the CBC program “Quirks and Quarks” interviewed Timothy Friesen, one of the researchers involved in the CERN anti-hydrogen study.
Antimatter falls down, much to the relief of physicists | Quirks and Quarks with Bob McDonald | Live Radio | CBC Listen (warning, autoplay at end of clip)
He noted that even though they did their best to cool the anti-hydrogen, the still present thermal motion and limited size of the test chamber meant that a portion of the atoms hit the top and sides. What they observed was that the expected percentage did hit the bottom of the chamber. To improve the accuracy they would need to start with a larger initial sample, suspended in a much larger chamber.