Ask a physicist anything. (7)

[mzungu]

Just as an update on the neutrino situation, I saw a talk today by one of the members of the collaboration. It was fairly interesting. My basic impression after walking away from the talk is:

1. I'm more convinced than ever that supernova 1987A observations make this result exceedingly unlikely. With SN1987A, the extremely long baseline (about 160,000 light years) means that measurement errors or errors in modeling the supernova simply aren't very important for the final result, which is that the difference in neutrino speed compared to the speed of light cannot be more than about one one thousandth of the observed speed discrepancy by the OPERA collaboration. It's going to be obscenely difficult, if not impossible, to come up with a theory that explains both observations (this was more from conversations before and after the talk than the talk itself, by the way).

2. The OPERA collaboration detected no difference in the arrival time at different energies. This, to me, was a giant red flag: in order to explain both the OPERA and the SN1987A observations, you're going to need the speed to depend upon energy. And yet it didn't appear to.

3. This measurement was an extremely sensitive and difficult measurement to make. It required a series of very accurate determination of time and position. And they did attempt to correct for the various errors by using a level of redundancy on these measurements. Still, if, for example, the delay induced by the electronics at the CERN laboratory were underestimated slightly, or the delay induced by the electronics at Gran Sasso was overestimated, that could explain the discrepancy as well.

4. There may have been some irregularities in the data reduction. As stated above, it's a really really sensitive measurement. And some people thought that the statistical analysis performed to extract the delays may have been a bit dodgy.

5. Approximately half of the OPERA collaboration declined to sign the paper. This may indicate some doubt within the OPERA collaboration that sufficient rigor was employed in this result, and is overall a pretty damning indictment of the results. There may be a mundane explanation for the fact that they didn't sign, but it really is not a good indication.

Spoken like a true scholar!

 

[GrowingSmaller]

Whats the speed of light in a dustpan and brush?

Is the speed of light the same in a Dyson cyclonic and a traditional Hoover upright?

 

[Wiccan_Child]

Whats the speed of light in a dustpan and brush?

Is the speed of light the same in a Dyson cyclonic and a traditional Hoover upright?

Current research indicates that light travels at c in all three instances.

 

[Cabal]

Dyson Singularity does sound pretty awesome though.

 

[Doveaman]

First, I disagree that you were; you made a glib remark that changed Chalnoth's words, If you had said "In my opinion, OPERA are incompetent", that's fine. But deliberately twisting someone's words to fit your own presuppositions doesn't fit the criteria of honest and civil debate.

But I personally don’t think the OPERA scientists were incompetent.

As a creationist, faster than light speed is not a problem in my religion, so such results only help to confirm my faith.

It’s you guys that seem to have the problem with the results, and my use of the term "incompetent" was only to summarize what Chalnoth appeared to be saying about the scientists who did the experiment.

But I accept that "incompetent" might have been a bad choice of a word on my part since Chalnoth clarified what he meant.

The original 'Ask a Physicist' threads were mine, and were shut down by someone like you.

Don’t make me out to be a monster.

Maxwell511 recreated the sixth incarnation,

I wasn’t aware your thread was closed. Sorry about that.

I thought this was your same thread and some error (there’s that word again) in the system resulted in Maxwell511 being registered as the OP.

but I still see this thread as my own, if only in spirit.

I see it that way too, actually.

If you noticed, I don't post here that often because I think you have a good thread going on here.

It's only when you guys post silly threads in these forums that I like to jump in so as to point out your silliness.

 

[Chalnoth]

As a creationist, faster than light speed is not a problem in my religion, so such results only help to confirm my faith.

Ahhh, so that is why you're so strongly opposed to any idea that this could possibly be a mistake.

And it's a screwy rationale if ever I heard one. Even if this experiment were confirmed (which is unlikely), finding that high-energy neutrinos travel 0.003% faster than light wouldn't really make for any significant differences in how our universe behaves at large scales. It would have some very interesting consequences for the details of fundamental law, but it just wouldn't impact us. At all.

This idea that this could possibly confirm your faith is positively ludicrous. Your faith must be such that any time you think you see something which contradicts established science, that confirms your faith. Well, guess what? Established science is almost always correct. It may be incomplete, but it is almost always correct. Betting against established science is like betting against a racehorse that almost always finishes the track in half the time as the competition. It's ludicrous.

 

[chris4243]

As a creationist, faster than light speed is not a problem in my religion, so such results only help to confirm my faith.

By this do you mean that invisible pink unicorns either help confirm your faith or are a problem in your religion, or that your religion conflicts with the idea that neutrinos can't travel faster than light?

 

[Ration]

Current research indicates that light travels at c in all three instances.

Well, it would be slightly less considering all these objects would be in earths atmosphere. Though by a very small margin, otherwise everything would be glowing blue...

 

[ToBeInChrist]

It doesn't bother me whether or not light travels at this speed or that speed, really.

Chris, does the existence/non-existence of little pink unicorns threaten your beliefs somehow, or would it destroy your lack of faith to find that neutrinos travel at this or that speed?

 

[mzungu]

YESSSSSSSSSSSSS!!!!!!!!!!!!!!!!!!! Researchers unveil a design for an "antimagnet" - a sort of invisibility cloak that undoes the effects of magnetic fields and which could find wide application.

http://www.bbc.co.uk/news/science-environment-15017479

 

[Wiccan_Child]

Well, it would be slightly less considering all these objects would be in earths atmosphere. Though by a very small margin, otherwise everything would be glowing blue...

The average speed (distance over transit time, relativity notwithstanding) would be slightly less than c, but the actual velocity of light would still be c

Light travels in fits and bursts when it travels through some medium, as it's absorbed by atoms in the air, and there is a small delay between re-emission. So although it travels at c when it actually moves, it keeps being delayed, and so the effective speed of light is less than c.

It's like a racing car that keeps stopping in the pitstop. Though its actual speed when racing is very high (and very constant), the pitstops mean its transit time is longer than it otherwise would be.

 

[mzungu]

[SIZE=-1] When light travels in a material, the photons are absorbed by the atoms which in turn increases their energy. After a fraction of time the atoms loose energy and release a photon. The released photon and the absorbed photons are identical. This process is repeated until the photons exit the material.
So to an observer, the light will seem to slow down!

A good example is:
If you take a plane from London to Athens on an airbus 320 and land in Paris for a transit stop whereby you immediately board another airbus 320 and continue to Athens with another transit stop in Rome; Then your trip will have taken longer than if you took a direct flight. The speed of the aeroplanes are identical but not the duration of the total time to complete the distance.
So in conclusion if an observer saw the plane take off in London and then observed the plane landing in Athens, when he knows the speed of the planes then he will mistakenly think the plane must have slowed down!

[/SIZE]

 

[mzungu]

Here's one for ya: If you compress a light beam by changing its frequency and decompress it again; Will the time it takes to cover a given distance "appear" to change

 

[Wiccan_Child]

Here's one for ya: If you compress a light beam by changing its frequency and decompress it again; Will the time it takes to cover a given distance "appear" to change

Technically, no. Light has only one intrinsic property, which can be expressed as energy, frequency, wavelength, etc. On the other hand, changing a photon's frequency would require interfering with it some how, probably by absorbing it and re-emitting it at a different frequency (a phenomenon known as florescence). As there will be a small delay before re-emission, it will appear to slow down.

 

[mzungu]

Mind-Reading Tech Reconstructs Videos From Brain Images | Popular Science

 

[Chalnoth]

Technically, no. Light has only one intrinsic property, which can be expressed as energy, frequency, wavelength, etc. On the other hand, changing a photon's frequency would require interfering with it some how, probably by absorbing it and re-emitting it at a different frequency (a phenomenon known as florescence). As there will be a small delay before re-emission, it will appear to slow down.

Well, to nitpick a little bit, a single photon has four degrees of freedom:
1. One degree of freedom for the frequency (or wavelength, or energy).
2. Two degrees of freedom for the direction of motion.
3. One degree of freedom for the spin (is it spin up or spin down?). This is also related to the polarization (can be described as horizontal or vertical polarization, or alternatively as right-handed or left-handed circular polarization).

 

[Wiccan_Child]

Well, to nitpick a little bit, a single photon has four degrees of freedom:
1. One degree of freedom for the frequency (or wavelength, or energy).
2. Two degrees of freedom for the direction of motion.
3. One degree of freedom for the spin (is it spin up or spin down?). This is also related to the polarization (can be described as horizontal or vertical polarization, or alternatively as right-handed or left-handed circular polarization).

Ah, that's why I said intrinsic property. Its extrinsic properties are, as you rightly say, variously categorised as direction, spin, polarisation, etc. But there's only one intrinsic property, expressed as either energy, momentum, etc.

 

[Certainty]

if you placed a photon/light into a container 100percent reflective, would the light stay in there forever, and if there were a camera (which had no theoretical mass) would the inside of the box look absolutely White ?

 

[Doveaman]

Ahhh, so that is why you're so strongly opposed to any idea that this could possibly be a mistake.

Nope.

This idea that this could possibly confirm your faith is positively ludicrous.

I agree. My faith has already been confirmed. Thanks for the reminder.

 

[mzungu]

If I were to look at a tree I would see a tree even though the light came from the sun. Now If I were to look at a mirror I would see myself with the the light still coming from the same source. Can you please explain reflection and how it affects the information carried by the photons?