Negative Time is Real, Physicists Confirm. Kind Of.

In a new paper, a group of physicists claims to have confirmed the existence of “negative time.” I had never heard of this, but I had a look at the paper. And I think I have figured it out.

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#science #sciencenews #physics

[DataIsBeautifulOfficial]

Finally, a way to procrastinate before I start.

[DanielaAngulo]

Hi, Sabine! I’m the lead author of the paper. Thanks for highlighting the research, I feel honoured. I wanted to add some clarifying comments.
1. A single photon has no definite phase so it is not possible to track those phases.
2. The paper is about measuring the atomic excitation time caused by those single photons. That atomic excitation time is mapped to a phase shift of another beam, a classical one, continuous wave.
3. We set a definition for that excitation time being the time integral of those phase shifts imparted on the auxiliary beam.
4. When we integrated and saw those excitation times, they happened to correspond to the group delay 😮
As you said, we wanted to see if the origin of the group delay that the wave packet of the photon picks up can be attributed to the time they spent as an atomic excitation (“inside the atoms”).

[Velereonics]

This may sound unrelated but my takeaway is that google news and traffic-based public interest being the driving factor behind academic success will be the end of us all.

[AdrianBoyko]

4:45 “sounds really weird at first sight” … I think it’s weirder that you hear with your eyes.

[Axacqk]

Pause at 0:27 and squint. Do you see cops in full riot gear storming a rave party or have I been spending too much time toying with stable diffusion these last few days?

[randyscottguitar]

Thanks for all your work, Sabine. I count on your plainspoken and informative videos every day.

[spastictuesdays]

I want -20 years, all the way back to that first time I woke up with a pain that I couldn't explain.

[jjeherrera]

This reminds me the claims some years ago regarding the possibility of sending signals faster than light by passing them through a dispersive medium. The explanation was similar to what you explain in this video. It was just a phase shift due to the dispersive medium. This property of dispersive media is used everyday for diagnostic purposes in plasma physics.

[therealnotanerd_account]

My brain bugged, when I saw an ad before this video with Sabine in it.

[TupperWallace]

Thank you for this very clear explanation of something that is impossible to decipher from news reports. We are fortunate to have you teaching us, even if you don’t believe in free will. 😊

[petervogel]

Great, that you are clarifying this subject so clearly, Other press information did not express the group velocity and so give a totally different impression of the facts. I studied Physics and Mathematics and appreciate any clear and complete description that does not mislead the mind. Thank you!!!

[I.amthatrealJuan]

I got a Sabine ad before the actual video. What?

[nyyotam]

This is reminiscent of super-luminal group velocity of photons: The group velocity is an artifact of the wave shape, so it cannot actually be used to modulate a signal and transform information. Every change in the wave shape will advance with the next wave front exactly at the speed of light and not any faster, even though that the group velocity can be as large as we wish (to both sides, positive or negative). It is also like a laser pointer moving across the lunar surface. If we move the pointer fast, it would look to us like the laser point moves faster than the speed of light, on the surface of the moon. But in fact, this is just an artifact of our design, and so it cannot be used to transfer information faster than light, between two points on the moon. So its not really negative time, just like group velocity (or the movement of the dot of a laser pointer fired from earth on the moon) is not really faster than light travel.

[andreobarros]

I feel like I got 15 years older in those last few 7 years. I supposed this could explain why other people are getting negative time.

[koraamis]

I didn't got late to work, just my wave packet got distorted

[vdivanov]

Here's a negative $10 (depending on the perspective).
The thanks though is certainly positive, hopefully in both directions!

[joyl]

I was reading about this and was hoping you would have more answers than the lame media articles. Your opening sentences had me laughing!

[simonleung]

So, the negative frequencies in Fourier Transform do have meaning

[gror]

Hi from Toronto! I typed this before the video was made and uploaded.

[michaelwhalan]

Closest to negative time is astronomy looking back at the distant past in the dark sky.