
New ALPHA-g Detector Poised to Search for Signs of Anti-Gravity - DanielBMarkham
https://spectrum.ieee.org/tech-talk/aerospace/astrophysics/new-alphag-detector-poised-to-search-for-signs-of-antigravity
======
stephengillie
> _Understanding whether antimatter obeys the same laws of gravity as matter
> is an important step toward confirming whether decades of theory surrounding
> antimatter stand true._

The Economist recently covered the same experiment at CERN:
[https://news.ycombinator.com/item?id=18110857](https://news.ycombinator.com/item?id=18110857)

------
ars
If anti-matter has anti-gravity, then the next question to answer is why do
photons obey normal gravity?

Are there anti-photons? (Presumably only anti-matter can make them.) Or is
matter special because it matches photons gravitationally and thus answers the
question of baryogenesis.

That second option leads to some very interesting implications for stars made
of anti-matter. Any photons they make would be "shoved" away from the star -
but where does that energy come from?

The first option means there are photons we can not detect (only anti-matter
can make them, so only anti-matter can see them). That would imply there is an
entire second universe out there overlayed on this one (at least photonically
overlayed) that we have never seen, except gravitationally.

But during annihilation events which type of photon would be produced? Both?
Randomly one or the other?

Finding that anti-matter has anti-gravity would open an absolutely enormous
list of questions. It's not as simple, as OK, anti-gravity - every other part
of physics would have to change as well.

~~~
akiselev
Do we know that photons obey normal gravity? I was under the impression that
we know that light can be bent by the warping of space-time due to gravity,
but not that it interacts with the Higgs field.

Photons don't _really_ have an anti-matter pair that we can observe afaik
because anti-particles have the same mass and spin but opposite charge as
their counterpart. Since photons have no charge, a photons anti-matter pair is
just another photon. Furthermore, we know that anti-hydrogen has the same
spectral lines as hydrogen so their electromagnetic interactions are the same.

Finding that anti-matter has anti-gravity would be world changing, though I'm
setting my expectations very low. It would mean that we have access to the
kind of exotic matter needed for a practical Alcubierre warp drive and could
open up an entirely new field of space time engineering. It's just extremely
unlikely, given all we know, that anti-matter has such properties.

~~~
AGoodName
>we know that light can be bent by the warping of space-time due to gravity

That literally is light obeying gravity. Gravity interacts exclusively by the
warping of space-time. Gravity and the Higgs field are completely 100%
unrelated.

[https://profmattstrassler.com/2012/10/15/why-the-higgs-
and-g...](https://profmattstrassler.com/2012/10/15/why-the-higgs-and-gravity-
are-unrelated/)

~~~
hliyan
> Gravity and the Higgs field are completely 100% unrelated.

That is an incredible insight for me -- I never thought of it that way. So the
thing that creates inertia (mass) is not the same as the thing that generates
gravitational force -- they're just correlated in the types of matter that
beings like us can interact with?

~~~
gpderetta
IANAP, but IIRC while the higgs field gives mass to electrons, quarks, the W
bosons and a few more particles, the vast majority of the mass of the atom
(and thus of what we normally call matter) is due to the binding energy of
quarks and gluons and not related to the higgs field.

------
blueprint
This could be one of the most important experiments that modern physics has
attempted.

It's funny that they must adapt their schedule to others, and not the other
way around. They're being given just a few days to carry everything out before
hitting a cut-off point that may realistically cause the experiment never to
get done due to changes in funding or the landscape.

If they obtain a positive result, how many experts will suddenly no longer
have a position of expertise?

Suddenly, I wonder if they are having a harder time than other experiments,
and whether there are any at CERN who actually don't want the experiment to
occur.

~~~
eganist
> If they obtain a positive result, how many experts will suddenly no longer
> have a position of expertise?

This is true of most experimentation for novel theories, and it's true of many
large experiments e.g. attempting to locate the Higgs Boson (the discovery of
which invalidated many theories of physics just through confirming certain
unknowns.)

> Suddenly, I wonder if they are having a harder time than other experiments,
> and whether there are any at CERN who actually don't want the experiment to
> occur.

Well, possibly, but not for the conspiratorial reasons you're alluding to.
It's a powerful device with only so much time to operate; the usage of that
time needs to be prioritized, and that prioritization can really only be
accomplished by gauging the likelihood of an outcome which produces new
knowledge (either validating a theory or invalidating it). No one behind the
operation of the ALPHA-g detector is going to block an experiment because they
may personally not like the results; if the detector has a hand in a
successful discovery, the detector and the team supporting it will be able to
claim having a hand in the discovery.

~~~
XorNot
The real issue is so far all the supporting evidence and theory says
antimatter obeys normal rules of gravity. So it really is a long-shot
experiment - if it actually differs in a significant way (and let's be clear:
experiencing less gravity, going in a slightly different direction - anything
- would be major) - then that would be a huge surprise.

~~~
blueprint
What evidence are you referring to which supports antimatter obeying "normal
rules of gravity", by which I am presuming you mean gravitating in the same
direction as matter?

~~~
krastanov
There is a very large and very convincing body of purely mathematical
arguments, and some minor experimental work
[https://en.m.wikipedia.org/wiki/Gravitational_interaction_of...](https://en.m.wikipedia.org/wiki/Gravitational_interaction_of_antimatter)

~~~
blueprint
For some reason I had a feeling you'd post that. That wikipedia page doesn't
show anything except for, at best, an argument that the Standard Model is
incompatible with gravitational repulsion plus many statements of unsuccessful
attempts to falsify repulsion of antimatter. Did you even read it??

By the way, it's old news by now that Standard Model is incomplete. But let's
just go back to passive aggressively condescending to people we don't know on
the internet by implying they've never studied so much as modern QFT because
we're not prepared to understand their original argument.

~~~
eganist
> But let's just go back to passive aggressively condescending to people we
> don't know on the internet

Please stop accusing people of this; it's being observed as radiating from
your own commentary by multiple people, which might explain why others are
responding in kind. I called out the gaslighting elsewhere, and the fact that
you're persisting with it against multiple parties hampers constructive
discussion.

~~~
blueprint
Are you not aware of his other comment to me? I've seen it many times before.
We don't know each other so perhaps defer belief that you can tell whether
that is true or not until you have some evidence. Gaslighting... lol

