Welcome to r/science! This is a heavily moderated subreddit in order to keep the discussion on science. However, we recognize that many people want to discuss how they feel the research relates to their own personal lives, so to give people a space to do that, personal anecdotes are now allowed as responses to this comment. Any anecdotal comments elsewhere in the discussion will continue to be removed and our normal comment rules still apply to other comments.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

Excerpt:

>Markus Oberthaler at Heidelberg University in Germany and his colleagues cooled more than 20,000 potassium atoms in a vacuum, using lasers to slow them down and lower their temperature to about 60 nanokelvin, or 60 billionths of a degree kelvin above absolute zero.

>At this temperature, the atoms formed a cloud about the width of a human hair and, instead of freezing, they became a quantum, fluid-like phase of matter called a Bose-Einstein condensate. Atoms in this phase can be controlled by shining light on them – using a tiny projector, the researchers precisely set the atoms’ density, arrangement in space and the forces they exert on each other.

>By changing these properties, the team made the atoms follow an equation called a space-time metric, which, in an actual, full-scale universe, determines how curved it is, how fast light travels and how much light must bend near very massive objects. This is the first experiment that has used cold atoms to simulate a curved and expanding universe, says Oberthaler.

Nature, DOI 10.1038/s41586-022-05313-9

I thought they decided it wasn't curved

Can someone explain how this means that particles materialize, breaking every mass or energy preservation rule?

> When the researchers used their projector to make atoms mimic an expanding universe, the atoms moved in exactly the kind of ripple pattern that would be expected if pairs of particles were popping into existence – a phenomenon called particle pair production. The researchers say this suggests that the particle pairs can be produced in an expanding universe, like our own.

Negative/positive particle pairs don’t break any laws because there is no net energy change

Most particles don't have zero mass, so the energy also has to come from somewhere.

Surely, that's a change in entropy going to wrong way, though? Do we have any other evidence of materializing matter for free at zero energy investment? What about mass?

Ground state fluctuations generate the paired particles.

Since there are fields everywhere and particles are just disturbances of the field, there can be random particle-antiparticle creation by "borrowing" some of the energy of that field. Usually they near instantly eliminate eachother, putting that energy right back.

Near black holes there is a chance that on the event horizon those pairs are created, one particle on the inside, one on the outside. The one on the outside can escape while the one on the inside won't (as it needs to travel at more than the speed of light). Hence energy is taken out of the field at the event horizon for the creation of 2 particles, but the black hole only gains one of them, hence it is a net energy loss of the black hole. That is also called Hawking radiation.

Also those thermodynamic rules are more of like a general trend and less of a rule that applies in every single instance.

That's why they simulated it

It’s not a zero investment - the energy comes from the ground state so-called “zero point” energy

[deleted]

[removed]

[removed]

[removed]

[removed]

[removed]

They saw how popular “WHAT IF” comics were and decided make a branch of study based on that called “science”.

Wild stuff, really.

Powered by piles of flaming grant money

[removed]

It’s just that popular, you see.

We know that it has a minimum curve, not that it isn't curved

I heard someone describe it as bumpy before I'm not sure how real that is mind u

It is, but its also traveling at c so as long as its moving away it won't cross the horizon. It could also be created so its moving towards the horizon as well and there's no change in the system.

[removed]

[removed]

When we were in high school me and my buddies used to pop out of empty space all the time, and it was no big deal

[removed]

[removed]

Hawking radiation

Gravity doesn't slow down light, it curves spacetime and makes the light need to travel further. The light always travels at the speed of light (in a vacuum.)

No one has ever described this so concisely in my entire life, thank you.

There’s a light bulb going off above my head now but I can’t see anything because of how dense I feel.

My understanding of this was that there was some kind of bias to pull antimatter in over the event horizon, shrinking the black hole. Although I don’t understand how’s it works. Am I wrong to make this assumption?

There is no bias, gravity [unlike other forces] does not discriminate between particles and anti-particles [they have positive mass after all].

Simply because 2 particles are created out of the field at the event horizo, the black hole looses the energy/mass [as they are interchangeable] of 2 particles. However since it can suck one of them right in (doesn't matter which) it can gain the energy of 1 particle back, while the other is ejected. Hence it has lost the energy of 1 particle.

> 2 particles are created out of the field at the event horizo, the black hole looses the energy/mass [as they are interchangeable] of 2 particles.

If the particles are created outside of the black hole, at the event horizon. How is it the black hole losing mass? These particles did not originate from the blackhole, they originated in the space many miles away from the blackhole. From my understanding of what you said the blackhole would be purely gaining mass.

everthying that is inside the event horizon is automatically part of the black hole, as nothing sub-light can escape. Since the particles are created at the boundary, one can be barely on the inside while the other is barely on the outside. The one outside can escape while the one inside is doomed. Since the energy comes from the point at the exact boundary, which is part of the black hole, it looses that energy and thus mass.

[removed]