New Study Shows Universe Still Expanding On Schedule

The Bad Astronomer writes "A century ago, astronomers (including Edwin Hubble) discovered the Universe was expanding. Using the same methods — but this time with observations from an orbiting infrared space telescope — a new study confirms this expansion, and nails the rate with higher precision than done before. If you're curious, the expansion rate found was 74.3 +/- 2.1 kilometers per second per megaparsec — almost precisely in line with previous measurements."

Comments

Obligatory Spelling Comment

[ixnaay]

Not to be pedantic, but that is an impressive way to misspell 'messureents'.

8 year old's question

[RichardDeVries]

It expands into what?

Re:8 year old's question

[RichardDeVries]

On behalf of all 8 year olds: thank you, that was very informative. As for myself: I'm supposed to have an IQ well above 130, but it would probably take me months to make sense of that page.

Re:8 year old's question

[kheldan]

Correction: There is no space and time that we can determine with any certainty outside our physical universe.

Re:8 year old's question

[multiben]

Milk. The universe is surrounded by milk.

Re:8 year old's question

[Anonymous Coward]

Unless you have a generic curiosity, don't try to hard to read that, as it is not related to the universe's expansion. The grandparent was just being random or joking. A Hilbert space is just what you get when you treat the set of all continuous functions as a vector space. It has several different possible basis sets of functions you can add up to make any other function, e.g. sine waves via Fourier analysis. Instead of having unit vectors like x, y, and z, you would have unit vectors like sin(x), sin(2x), sin(3x), etc. (which makes it infinite dimensional). The concept is really important to physics, especially quantum mechanics and any where else things like Fourier analysis would be done with some mathematical rigor. But it is not what the universe is expanding into.

The typical analogy used for what the universe is expanding into is like a balloon being inflated, with that being a 2D universe on the surface of the balloon. You could ask about the third dimension it is expanding into, but that is not really relevant (at the moment at least). The only thing that really matters is the curvature of local space (how non-flat any given spot on the balloon is). Short of discovering some new theories unlike what we've seen before or something like brane theory, the equivalent of the 3D dimension in the balloon analogy would be unreachable and meaningless, as it would not be able to affect things in anyway beyond the curvature of the surface.

Re:8 year old's question

[turbidostato]

"There is no space & time outside the physical universe.
Are you sure? How do you know?"

He doesn't need to know: that's a per-definition fact.

A different question would be if the physical universe is composed of four dimensions or there are more.

Re:Units

[amRadioHed]

Due to expansion, the speed of objects accelerating away from us is proportional to the distance from us. So according to this, an object at 1 megaparsec from us will be receding at 74.3 km/s, while an object at twice the distance will be moving twice as fast.

Re:Not to be pedantic

[countach]

Well, to be pedantic, its a stretch to say "we have no clue". We can make some pretty damned good guesses.

Re:Units

[sconeu]

Interestingly, some back of the envelope calculations (using rough numbers ... 300000km/s for c, 75km/s/mpc for Hubble's Constant, and 3.25 ly/pc) gives a value of roughly 13 billion light years for the recession velocity to approach c. 13 billion years is also *ROUGHLY* the age of the visible universe.

Re:Units

[ImprovOmega]

That can't be right. The universe is about 14,000 megaparsecs in radius, even if we were at the exact center that would have things traveling outward at 1.04E9 m/s or 3.46c. I'm reasonably certain they're not claiming FTL on this one so... Is it actually 74.3 m/s instead of 74.3 km/s? Or is there something else going on here?

Re:Units

[j00r0m4nc3r]

Space itself can expand FTL, but anything inside that space is limited to c. This also means that at any given point in the universe, there is a boundary where you can never reach beyond, because the space itself is expanding away FTL, so you can never catch up to observe anything beyond that boundary...

Re:Units

[thrich81]

Space itself can expand such that the objects (events?) within it are moving apart at faster than c. Any two objects separating faster than c can't measure that -- they cannot pass any signal between them. Any light (or other signal) which leaves one will be redshifted away to nothing before it gets to the other. They are outside each other's observable universe. I'm pretty sure this has to handled using General Relativity, I don't think Special Relativity has any concept of expanding or contracting space-time. Space-time described by Special Relativity is flat and static.