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It's Official: You're Lost In a Directionless Universe (sciencemag.org)
Reader sciencehabit writes: Ever peer into the night sky and wonder whether space is really the same in all directions or if the cosmos might be whirling about like a vast top? Now, one team of cosmologists has used the oldest radiation there is, the afterglow of the big bang, or the cosmic microwave background (CMB), to show that the universe is 'isotropic,' or the same no matter which way you look: There is no spin axis or any other special direction in space. In fact, they estimate that there is only a one-in-121,000 chance of a preferred direction -- the best evidence yet for an isotropic universe. That finding should provide some comfort for cosmologists, whose standard model of the evolution of the universe rests on an assumption of such uniformity.
I guess my purpose is to lead a meaningless, directionless life.
120 characters ought to be enough for anyone
Neither "lost" nor seeing how the topology of the universe is pertinent in any sense to that.
Rather a long stretch from the science to a populist click-bait philosophical "conclusion"...
~ Whence do you come, slayer of men, or where are you going, conqueror of space?
This is what happens when you use Apple Maps for directions...
What if the observable universe (whose boundary is the CMB or maybe the cosmic neutrino background) is only a small tiny fraction of the actual universe, and it does have a direction, but that direction is so small on our scale that it isn't measureable and lost in the noise?
This doesn't convince me that the universe isn't just a bunch of left over particulates from the power stroke of an ICE. A few hundred billion more years and we're probably going to start getting pushed out the exhaust valve.
It was just dismissed as a statistical error, because no one really wanted to address it.
You are in a universe full of twisty little galaxies, all alike.
Mod me down with all of your hatred and your journey towards the dark side will be complete!
Incorrect.
Mind / Consciousness.
//It was quickly realised that this dipole was the result of our Galaxy moving at 600 km/sec with respect to the CMB radiation//
source
Hey, you're not lost. Look on the bright side. You're always at the center of the universe. ;^)
You sound way too rational to be an AC here at Slashdot.
Have you considered signing up for an account? Or, alternatively, commenting on sites that are much more serious than this one? Reading your post, I have the feeling your rational thoughts are going to waste here. You might actually help people think if you keep doing posting well reasoned statements here.
While the CMB may be without spin, there are giant voids that appear to only exist in one direction. Saying "the universe is isotopic" implies that it's the same in all directions, and if there are giant voids in only one direction, then that's clearly false.
Now to state that the CMB is without direction inherent in it may well be a true statement, and it sounds much closer to what they actually showed. That, itself, is an interesting statement, and may well be true. The step from there to "the universe is without direction" appears false. Which is an interesting result, and may be significant. Somehow if cosmic inflation happened it allowed minor variations to be expanded into significant variations. (This has been proposed before as one of the reasons for believing in inflation.) But this would appear to imply that the CMB was set at a time before inflation. (I don't know whether this is standard theory or a new result.)
I think we've pushed this "anyone can grow up to be president" thing too far.
Almost to the beginning. The CMB dates to something like 370,000 years after the start. Prior to that the universe was opaque - too many free electrons. Super-hot electron soup blocks radiation across all wavelengths.
Are you so tired that you don't know the different usage of "to" and "too"?
"Eve of Destruction", it's not just for old hippies anymore...
No! It really is special. In any frame except the CMB rest frame, a moving particle experiences Hubble drag from the expansion.
That's just not true. A particle moving in any reference frame will experience "Hubble drag" from expansion, with regard to that reference frame. There is no such thing as a "special" frame of reference: the laws of physics are invariant with regard to all frames of reference, inertial (special relativity) or not (general relativity). The expansion of the universe means that you can't establish a global inertial reference frame, which is why we need, so you need general relativity for cosmological expansion (though interestingly enough Newtonian cosmology arrives at the same end results, in many cases).
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
In that case, doesn't the CMB radiation represent a frame of reference, kind of like the (discredited) Ether idea?
Yes, it is called the Hubble flow comoving frame. Since we are moving relative to the comoving frame this creates a dipole pattern on the Cosmic Microwave Background due to Doppler shift. For the Solar System (moving within the Milky Way galaxy) it is 369 km/sec in the direction of the boundary between the constellations Leo and Crater.
Second class citizen of the New Gilded Age
That doesn't sound right to me.
a photon moving in an expanding universe redshifts
Only from the point of view of an observer somewhere in its future light cone. To the person who fired the photon, or anyone else in the past light cone, it would blueshift (not that they can detect it any more).
Or to put in another way, if two photons are travelling in opposite directions, expansion will redshift them both, according to anyone who might detect either of them. But that means their momentums have changed by opposite amounts, so they can't both have been "slowed" (not the right word when you're talking about light, but it'll do, and the same applies to massive objects as well) towards the same rest frame.
systemd is Roko's Basilisk.
A particle moving in any reference frame will experience "Hubble drag" from expansion, with regard to that reference frame.
Uh, no. Hubble drag drives velocities exponentially to zero in one particular reference frame, which is the comoving frame. Anything at rest with respect to the comoving frame stays at rest. There is no conflict with relativity here: the fundamental laws of nature are true irrespective of reference frame, but the particular realization of the spacetime induces a preferred frame. This is akin to spontaneous symmetry breaking in particle physics (i.e., the Higgs mechanism).
Or to put in another way, if two photons are travelling in opposite directions, expansion will redshift them both, according to anyone who might detect either of them. But that means their momentums have changed by opposite amounts, so they can't both have been "slowed"
It's the magnitude of the momentum that matters. Think of it in terms of energy: as photons propagate through an expanding space, their wavelengths increase, i.e. they lose energy. This is true regardless of the direction in which the photons are propagating. The same happens to massive particles, except in that case, they actually do slow. Observers with in different Lorentz frames will see the photons redshifted or blueshifted in different ways, but that is an independent effect.
You have to think in terms of coordinate invariants.